pppg gp

during equipment failure investigations. The citations of Annex A of Part 3 were collected for the working 

group that developed the IEEE SPD Trilogy but do not purport to be an exhaustive listing. Although 

acknowledged and appreciated, for obvious copyright limitations, these 51 papers from other researchers 

cannot be reprinted here. 

CONTENTS 

 

Surge suppression in a typical home wiring system (1963) 

Surge voltages in residential power circuits (1967) 

Surge voltages in residential and industrial power circuits (1970) 

Transient overvoltages in secondary systems (1981) 

Varistor versus environment: Winning the rematch (1986) 

Annex – Statistics on failure rates of clock motors (1964)
SURGE

SUPPRESSION

IN

A

TYPICAL

HOME

WIRING

SYSTEM
Reprint of declassified General Electric Technical Information Series Report 63GL97

Significance:

Part 3 Recorded occurrences

The present interest in this report is historical as the experiments and devices it described represent

initial efforts in addressing the emerging problems associated with the introduction of semiconductors in

the consumer market.

This now declassified proprietary report was prepared to document experiments performed in the early

sixties to assess the capability of devices available at that time for serving as surge-protective devices in

residential circuits. The context was that the emerging electronic appliances were found vulnerable to

transient overvoltages and therefore in need of some form of protection.

The technology at that time offered the well-proven selenium rectifier (under the General Electric trade

name “Thyrector” among other similar offerings in the market), the well-known low-pass RC filter, and the

emerging five-layer semiconductors. All these were then valid candidates but of course became

completely supplanted ten years later when zinc-oxide based varistors were stumbled upon and quickly

recognized as a promising technology.

Interesting observations on the propagation of surges in a low-voltage ac power system are also

documented in this report, and these are still applicable today.
TECHNICAL INFORMATION SERIES 

GENERAL @ ELECTRIC 

I -. - .. - 

REPRODUCIBLE COPY FILED AT G.E. TECHNICAL DATA CENTER NO. PAGES 

BLDG. 5, SCHENECTADY, N. Y. 

LIMMARY 

Artificial surges approximating typical switching surges 

were injected in a home wiring system. Various types of 

surge suppressors were connected to various points of the 

NO. 63GL9 7 

DATE 6/24/63 

G.E.CLASS 1);s 

GovT. cuss None 

rUTHOR 

.D. Martzloff 

system and their effectiveness evaluated. 

SUBJECT 

For the short (3~s) surges applied, the following surge 

suppressors provided the attenuation tabulated below, 

showing the effectiveness of the AC switch and SSS switch 

ITLE Surge Suppression in a Typical Home 

Wiring System 

SUPPRESSOR 

GE "AC Switch" 

Hunt "SSS Switch" 10 

Controlled Avalanche 

Diode 3 0 

Further work is required to investigate the Thyrector 

performance with surges of longer duration 

% of original % of original . 

surge at location surge at other 

!of suppressor 1 points 

:EY WORDS 

~NFORMAT~ON PREPARED FOR Transient Overvoltages Pooled Program 

TESTS MADE BY S. Deiber - F. D. Martzloff 

AUTHOR F. D. Martzloff t??fl& 

2" Thyrector 5 0 

~OMPONENT Converter Circuits Engineering 

50 

I 

APPROVED R. G. Hoft 
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VOLTAGES

IN

RESIDENTIAL

POWER

CIRCUITS
1

 A nostalgic footnote:

As noted on the cover page,1967 IEEE Conference papers were available at the meeting

at the then-current price of $0.75, and later for $1.00. However, they became no longer

available from IEEE some time thereafter. This reprint is one of the rare archival records.

G.J. Hahn

General Electric Company

Schenectady NY

François Martzloff

General Electric Company

Schenectady NY

f.martzloff@ieee.org

All rights reserved IEEE

Reprinted, with permission, from 

IEEE Conference paper 31 CP 67-430 1

Significance:

Part 3 – Recorded occurrences

One of the first papers reporting surge recording in low-voltage ac power circuits (see footnote).

Both waveform information and frequency of occurrence marked the beginning of the IEEE effort toward

characterizing surge voltages in low-voltage ac power circuits, a departure from the traditional unidirectional

and separate 1.2/50 and 8/20 waveforms in use for high-voltage equipment testing.

In the mid-sixties, when these recordings took place, there were very few, if any, surge-protective devices

(SPDs) installed in residential power circuits. After the emergence of ubiquitous consumer-type SPDs, the

results of subsequent monitoring campaigns were drastically changed (See “Galore” in Part 2) but the

information is still valid for the frequency of occurrences to the extent that the origins of surges have not

changed, only the observed levels are now considerably reduced by the proliferation of SPDs.
SWE VOLTAGES IN RESIDENTD% POWER CIRCUITS 

Both of: 

General Electric Cunpany 

Schenectady, N. Y. 

G. J. Hahn 

F. D. Martzloff 

Menber IEEE 

A paper recurmended by the IEEE Pmtective Devices Carmittee of t

IEEE Power Group for presentation at the IEEE Scnmer Fbwer Meetin

brtland, Ore., July 9-14, 1967. Manuscript suhitted April 3, 1

made available for printing May 3, 1967. 

I - Price: $1.00 All Rights Resewed by (759 at meeting) The Institute of Electrical and Electronics Engine

Inc., 

(15C per copy additional if 345 East 47th Street first class mailing desired) N~I., vnllr TLT v r nnl n 

Paper No. 

31 CP 67-430 

A.G.. au-rr, L.. I. lVYl, 

(254 per copy additional if 

air mail is desired) Litho in USA 
SURGE VOLTAGES IN RESIDENTIAL POWER CIRCUITS 

by 

G.J. Hahn and F.D. Martzloff 

Research and Development Center 

General Electric Company 

Schenectady, New York 

Abstract 

Special instrumentation was developed for 

monitoring the magnitude and frequency of occurrence of surge voltages in residential circuits. 

Over a period of two years, more than 400 

locations in 20 cities were surveyed. Monitoring 

was accomplished by automatic recording cathode 

ray oscilloscopes and simple surge counters. 

Two significant sources of surge voltages 

were identified: load switching within the house, 

and external surges, most likely associated with 

lightning, coming through the service drop. 

Internally generated surges as high as 2500 

volts were recorded during this test program, and 

six of the 250 households (i.e., 2.4 percent) in 

the sample experienced surges of this type in excess of 1200 volts once or more per day. A statistical evaluation indicated that a 90 percent 

confidence interval for the true proportion of 

homes with such surge voltages is between 1.0 and 

4.7 percent. 

Surges due to lightning reaching 5600 volts 

have been recorded on a 120-volt overhead distribution line. Independent evidence shows the 

occurrence of a number of surges in excess of 

2000 volts. 

In this study, a total of. 8 surges in excess 

of 1200 volts were caused by lightning and recorded on 39 counters at room outlets in 14 localities over the summer months. 

Introduction 

The successful operation of semiconductors 

and new insulation systems in appliances and consumer electronic devices may be adversely affected 

by transient overvoltages occurring on the 120- 

volt power supply. Detection and measurement of 

these transient surges permits a designer to provide suitable built-in tolerance, or at least to 

recognize that there is a need for appropriate 

suppress ion or protect ion: 

Special instrumentation has been developed 

for detection and measurement of surge voltages. 

In the first phase of testing automatic recording cathode ray oscilloscopes provided complete 

information on wave shape, and on magnitude and 

frequency of occurrence at a small number of 

arbitrarily chosen locations. These data, though 

statistically restricted, were adequate to demonstrate the existence of the problem, define some 

sources, and indicate typical wave shapes. It 

also became clear that there was a need for a 

larger sample that would be more statistically 

valid. 

In the second phase of testing, one hund

surge counters, simple in design and easy to 

stall, were developed especially for this prog

These counters were installed in several hund

homes in various cities located in the East an

middle West of the United States. 

The purpose of this paper is to discuss r

cordings obtained during the two phases of th

program and the statistical aspects of the re

It is hoped that publication of this paper wi

encourage other investigators to publish thei

findings. This would provide a broader stati

tical base for verification of the frequency a

magnitude of surge voltages. 

Instrumentation 

Recording surge voltages in the field po

special problems. For example, the instrumen

cannot be continually attended and the signals 

be recorded are unpredictable in magnitude, p

ity, and frequency of occurrence. 

In cooperation with Tektronix, Incorpora

a type 515 cathode ray oscilloscope was modif

to record transients on film, with automatic a

vance of the film after a recording. 

The modifications involved a change in th

trigger and sweep circuits, as well as remova

a11 knobs (an important detail for an instrum

to be left in all types of locations). 

Most oscilloscope trigger circuits are p

ized. This often causes a loss of recording w

the polarity of the initial signal is not know

For surge recording, the trigger circuit was m

ified by feeding to the time base trigger thro

two OR logic diodes the push-pull signal that 

applied to the input of the oscilloscope dela

line. With this modification, the sweep is 

started for either polarity, while the signal 

delayed before reaching the deflection plate 

the CRT. In addition, the conventional blank

circuit holds the beam in low intensity befor

the sweep starts. 

A second modification changed the sweep 

a constant speed to a logarithmic speed, fast 

the start and slow toward the end. This allow

the recording of an impulse front with good re

lution, while providing sufficient duration o

the sweep to record a long tail. 
Finally, a relay was added with its coil 

energized whenever the beam sweep is triggered. 

Through a set of contacts on this relay, the film 

advance sequence in the camera is activated. 

The camera, attached to the scope bezel, is 

a Beattie-Coleman system, accommodating 100 feet 

of 35 mm film, with no shutter, and recording on 

a 24 x 36 nun frame the trace displayed on the CRT. 

Following the sweep, the contact mentioned above 

closes the motor circuit, advancing the film to 

the next frame in a few seconds. This film transport duration is matched in the oscilloscope trigger circuit by a hold-off so tliat no sweep will 

occur during film advance. 

In order to prevent the film from being 

fogged by extended exposure to the faint glow on 

the phosphor (caused by imperfect blanking of the 

beam, cathode glow or light leaks) a built-in 

timer in the oscilloscope advances the film by one 

frame every hour. This provides an approximate 

method for timing the occurrence of surges. Since 

the surge-voltage tests were conducted, an automatic time recording feature has been added to 

give a more precise recording of time at each 

event. 

Figure 1 is a photograph of this oscilloscope 

camera system. The relatively high cost of this 

system, its conspicuous presence (e.g., size, 

camera noise, etc.) in a home, and the amount of 

film to be scrutinized frame by frame limit the 

number of locations at which recordings can be 

made. However, for conclusions to rest on a sound 

statistical basis, it is necessary to investigate 

a large number of locations. To be acceptable to 

cooperative home owners, a transient detector 

should therefore lend itself to inconspicuous installation and simple data handling. Thus, a device which can merely be plugged into a wall 

receptacle, and that has a digital counter indicating the number of surges occurring above a 

specified threshold is satisfactory for widespread 

recording. 

The circuit shown in Figure 2 was developed 

for the purpose, and packaged as shown in Figure 

3. This device is connected to a wall receptacle 

by a conventional appliance cord, not a special 

probe. This connection is simple, establishes a 

typical final path for a surge impinging upon any 

appliance connected to this particular wall receptacle, and provides power for the high impedance rectifier circuit and a signal input to 

the trigger-sensor circuit. 

A crudely compensated divider (RlCl/R2C2) 

attenuates the incoming surge before application 

to the Silicon Symmetrical Switch (SSS). This device has the characteristic of turning on abruptly 

whenever the voltage across it reaches a threshold, such as 250 volts. This threshold remains 

constant for durations as short as 0.1 s. When 

the SSS turns on, the attenuated surge is applied 

to the gate of the very sensitive, fast switching 

Silicon Controlled Switch (SCS). If the polarity 

of this surge is positive, the SCS turns on, 

allowing the capacitor C to discharge through 

coil of the solenoid-actuated counter S. A h

impedance (50,000 ohm) divider and half-wave 

tifier provide a trickle charge 15-volt suppl

the capacitor C. The resistance of this divi

represents a negligible load for the house wi

system, yet is sufficiently low to allow some 

leakage in the electrolytic capacitor C. The 

charging time (several seconds) of the capaci

is not objectionable, since the transients to 

detected do not have a high repetition rate. 

Calibration of the circuit is obtained b

justing the value of the divider (RlCl/R2C2). 

these tests, the threshold level was set at 1

volts for one group of counters and at 2000 v

for another group. A bench circuit was set u

whereby a surge with adjustable level and dur

could be superimposed on a 60 Hz, 120-volt po

supply. Some consideration was given to the 

to segregate, or filter out, the surge from t

60 Hz power voltage; in this case, however, w

the minimum level at 1200 volts, the base 170

crest represented a small contribution and wa

cluded in the signal detected by the circuit. 

Surges with approximately flat top and duratio

from several microseconds to 0.2 microsecond 

applied to determine the variation of the thr

old voltage as a function of surge duration. 

typical response curve is shown in Figure 4. 

response of this crest-indicating counter can 

considered satisfactory, since the oscillosco

recordings in homes, as will be discussed lat

have indicated that the shortest half-period 

oscillatory surges is in the order of 2 micro

seconds. 

Recording Procedure 

In the first phase, oscilloscopes were i

stalled at the basement service entrance of h

in the Schenectady, New York area. These loc

do not represent a statistician's ideal sampl

but, during the initial phase of the program, 

nature of transients rather than statistical 

racy was the major subject of interest. Late

the program, the range of locations was broad

to include homes in other urban and rural are

particularly in Florida and South Carolina. 

In the second phase, surge counters were 

stalled at unspecified outlets in the homes o

engineers in 20 cities in the northeast and m

west. Two distinct recording periods were sc

uled: winter, because there is usually a mini

of lightning activity at that time of year, a

summer, which ordinarily includes a mziximum o

lightning activity. 

Since the oscilloscope input circuit ope

at a level of a few volts, it is somewhat sen

to direct radiation of electromagnetic noise 

the preamplifier, even if there is no signal 

the probe. In order to discriminate against 

type of spurious indication, the recording pr

cedure included a period during which the osc

scope probe was shorted with the ground termi

remaining connected, so that spurious signals 
to ground loops would be detected. In this manner, any noise entering the system could be recorded and later recognized for what it was in 

the analysis of the recordings made with the short 

circuit removed from the probe. 

The surge counters record only one polarity; 

in order to minimize record keeping by the homeowner, the connection of the cord was not polarized. In the event of an oscillatory surge (which 

is always quickly damped in these systems) two 

cases of counting can occur. For instance, the 

high side of the divider can be connected to the 

"hot" terminal of the receptacle (Figure 5). If 

the first half-cycle is positive and exceeds 1200 

volts, a count is registered. If the first halfcycle is negative, and the second, positive half 

is highly damped, no count is registered. If the 

first half-cycle is well above 1200 volts causing 

the second half, in spite of some damping, to exceed 1200 volts, a count is registered. For the 

reverse connection, the same would occur for reverse polarity. Thus, the actual number of surge 

occurrences of both polarities in excess of 1200 

volts is between 1 and 2 times the number indicated by the counter. The objective of the recording in this test series was only to determine 

whether or not surges occurred rather than their 

exact number. Consequently, the value of the 

multiplying factor is not very significant. 

Results Of The Recordings - Oscilloscopes 

The first recording analysis revealed that 

some homes were subject to frequent surge voltages, some experienced only a few isolated surges, 

and others did not experience any surges in excess 

of the trigger level (300 to 400 volts). Furthermore, among those installations where surge voltages frequently occurred, the surges at some 

houses were relatively low (rarely in excess of 

800 volts), while other houses had surges in the 

range of 1200 to 2500 volts. 

Rates of surge occurrence ranged from zero 

(no surge in one to two weeks) to 0.5 per hour, 

with peak values from 400 volts (trigger threshold) to 5600 volts. 

At the conclusion of the recording program, 

a total of 16 homes and two overhead distribution 

poles had been monitored for a total of 7000 

hours. The peak of the surges was distributed as 

shown in Figure 6a; the most frequent and severe 

surges were distributed as shown in Figure 6b. 

Further analysis of some recordings was made 

by deliberate switching of loads in the houses 

where frequent surges had been observed. In some 

cases, the operation of a specific device (e.g., 

oil burner, fluorescent lamp, pump motor, refrigerator, food mixer, etc.) was found to be the 

cause of the surges. In other cases, no amount of 

deliberate load switching could reproduce surges 

such as those recorded during unattended monitoring. The home owner was occasionally able to 

correlate surge recordings with lightning or 

power system disturbances. 

A pattern emerged from all this informat

showing two definite causes of surge voltages

the homes: 

1. Load switching in the house occasion

produced transient surges; these affected 

only that particular house. For any par

ular house, these transient surges had a 

shape which was consistently repeated wi

variations in amplitude along the entire 

recording. This probably resulted from c

bination of switch characteristics and th

impedance of the house wiring system; the 

variations in amplitude were probably cau

by variations of the switching angle and

connected loads. Typical wave shapes of 

recorded surges are shown in Figures 7a, 

and 7c. 

In one case, it was possible to inst

an oscilloscope in a house adjacent to th

where repetitive surges up to 1700 volts 

being recorded. The service drops were c

nected to the same pole, yet no surges o

ring simultaneously were recorded in the 

second house. 

2. Surge voltages not associated with lo

switching within the house were associate

with lightning storms. In some cases, th

home owner was able to correlate the film 

vance counts with the storm. Although re

corded during lightning storms at two di

ent locations, the surges shown in Figure

8a and 8b present the interesting charac

istic of being oscillatory at a frequency 

the range of 300 kHz. The surge shown in 

Figure 8a was recorded-at the overhead d

tribution line (oscilloscope mounted on t

pole), while the surge of Figure 8b was r

corded at the service entrance in a home

The first exhibits far less damping than 

second; this might be explained by the lo

damping due to lower resistance of the sy

tem at the pole than at the end of a serv

drop. 

Both of these surges, as well as most of 

other surges recorded during lightning storms

exhibit this oscillatory characteristic at a f

quency which,is nearly constant for a particu

locality. This constancy suggests that the o

lation of the system followed an excitation ca

by the lightning stroke. A number of surges 

the range of 800 to 1200 volts were observed d

ing several storms. The maximum surge voltage 

recorded was 5600 volts; several other surges 

corded during the same period were in excess o

4000 volts. 1 

Results of The Recordings - Counters 

With the two causes of transients identi

by the oscilloscope measurements, the surge 

counters wee applied in two separate program

First, during the winter months, the counters 

installed in a large number of houses for peri

of one or two weeks; the objective was to 
determine how many houses sustained repetitive 

surges. Second, during spring, summer, and fall, 

each counter was left at one or two locations for 

periods of 9 to 48 weeks; it was known from the 

first test that these homes were not subject to 

load switching surges. The objective was to determine the frequency and characteristics of externally generated surges, presumably caused by 

1 ightning . 

The first period produced the data shown in 

Table 1, and the results obtained during the 

second period are shown in Table 2. 

Statistical Analysis of The Recordings 

Internally Generated Surges 

The data in Table 1 show that 6 houses, or 

2.4 percent, were subjected to repetitive surges 

from among a total of 250 homes sampled. The 

true percentage doubtless differs somewhat from 

2.4 percent due to statistical variations. However, one may be 90 percent confident that the 

true percentage is between 1.0 percent and 4.7 

percent." This band could be narrowed by taking 

additional samples. However, it should be noted 

that the precision is proportional to the square 

root of the sample size. Thus, four times the 

number sampled, or 1000 homes, would be necessary 

to cut the size of the statistical error band by 

approximately one-half. Since the above results 

refer to statistical variations only, they do not 

take into account possible biases due to such 

factors as restrictions in selecting members of 

the sample (principally engineers in a number of 

designated locations) or the time of year (winter 

months ) . 

The probability of internally generated surges 

undoubtedly varies among e.conomic groupings (i.e., 

the devices in use in homes probably vary with the 

economic status of the resident); however, devices 

found to generate surges ( i . e . , furnaces, refrigerators, etc.) exist in most homes. 

Externally Generated Surges 

Results from the second testing period that 

was concerned with externally generated surges are 

shown in Table 2. From 39 counters installed in 

a total of 91 homes in 14 localities, a total of 

8 occurrences in 6 separate localities were observed during an equivalent exposure time of 846 

weeks. A ninth occurrence was disregarded in this 

analysis because it occurred in the same home during the same storm. Of the two pairs of occurrences which took place in the same location, one 

pair occurred during the same stonn and the second 

involved two occurrences at different times. 

 his result is obtained by the well-known method 

of setting confidence intervals for a sample percentage. Further details may be found in statistical te~ts.~,3.4 

Analyses could be conducted based on the 

following alternative assumptions: 

1. Voltage surges above 1200 volts occur 

only during the period of the year that t

counters were installed in the homes. Th

although the counters were in homes for o

part of the year, the time involved (i.e.

the summer months) was so chosen that no 

ther surges would have been noted even if 

each counter had been run for 52 consecut

weeks. The average number of surges per 

would then be 8/39, or 0.205. 

2. Voltage surges occur randomly at a co

stant rate throughout the year. Thus, a 

counter which was in use 9 weeks, on the 

average, would be subject to a third as m

surges as a counter in use for a period o

weeks. Under this assumption, a total of 

surges observed in a total time equivalen

16 years (846 weeks) ~ields an average of 

surges per year. 

Using these tuo extreme assumptions, a ra

could be established for the estimated number 

surges per year in a larger sample, based on t

specific sample, The above calculations refer 

only to single polarity surges. If all surges 

being considered, the given values must be mu

plied by a value corresponding to the addition

proportion of opposite polarity surges above 1

volts which do not also result in positive sur

above 1200 volts. This multiplying factor is 

probably about 1.6; it accounts for the dampin

between the first and second 1/2 cycle of an o

latory surge. 

Lightning-induced surges are likely to af

more than one house when they occur. Local ge

graphical and meteorological conditions are cr

cal influences on these surges ; however, these 

factors could not be considered in this prelim

investigation, 

To relate the above data to risk of appli

failure, the given values must be modified by 

probability that a surge above 1200 volts woul

cause failure of operating appliances. Failur

effects would vary with different appliances. 

Possible Further Analysis 

A more refined analysis for a probability 

measurement of voltage surges per lightning st

is possible if the geographical location of th

homes, the occurrence rate of lightning storms 

during the testing period, and exact dates at 

voltage surges occur is considered. The resul

values can then be used in conjunction with in

formation given in Reference 5 to calculate th

probability of a voltage surge in any specifie

geographic area, during a particular part of t

year. Such an analysis would remove the need 

making one of the two alternative assumptions 

stated above and lead to a single set of estim

However, this would require more detailed data 

could be collected in this program. 
Finally, it is noted that if one has knowledge of the actual voltage surges, rather than 

merely the information concerning whether or not 

a surge above 1200 volts occurred, a more sensitive analysis is possible. In this case, for 

example, probability plotting and other techniques 

based upon the statistical theory of extreme 

values4 3 might well be applicable. 

Effects of Surge-Voltages 

On Connected Electrical Devices 

The surges which have been recorded in this 

program occurred during normal operation of the 

household, with no knowledge of the connected load 

situation at the time of occurrence. 

The question of energy involved in the surge 

is related to the impedance of the system, since 

these recordings provide voltage data only. Surge 

impedance measurements of house wiring cable indicate a value of 100 to 300 ohms for a typical 

branch circuit, so that the surge impedance at the 

service entrance could be in the order of 5 to 10 

ohms. However, this low value exists only for the 

travel time (i.e., a fraction of a microsecond). 

Connected loads will have a lower impedance than 

that of the branch circuit. This value will be 

dependent upon frequency whenever inductive components are present. These loads will absorb part 

of the energy of the surges and thus lower their 

peak. 

Ikvices such as motors and transformers have 

solid insulation and such a long history of successful application that their performance is not 

in question. Perhaps unusual failures can be explained by extreme values of surges as indicated 

by the data. 

Defective wiring practices (e.g., pinched 

insulation, reduced air clearances in wall boxes, ' 

etc.) will cause air flashover with or without 60 

Hz power follow. In fact, one house was brought 

to our attention because of complaints of sparking 

in a light fixture. With the switch in the ground 

wire and the frame attached to a grounded pipe, 

flashover at 1700 volts was observed in correlation with the start of an oil burner in the house. 

This defective light fixture was acting as a voltage limiting gap for the house. 

Appliances containing semiconductors and directly exposed to the line transients may be more 

vulnerable. Actually, the 1200-volt threshold 

level was selected as the result of this consideration. It is interesting to note that, although a 

number of surges above 2000 volts were recorded by 

the oscilloscopes, the few surge counters calibrated for 2000 rather than 1200 volts did not 

produce any recording above 2000 volts. 

An independent study of clock motor failures 

produced information on failure rates versus withstand levels. This study was very pertinent to 

the surge counter program, since thousands of 

clocks are connected a t a l l times to the power 

system. Over a period of three years, failure 

rates were correlated with insulation level of 

coils. A very significant 100 to 1 drop in fa

ure rate resulted from an increase in withstand 

voltage from approximately 2000 to approximate

6000 volts. This shows that, even though no 

surges over 2000 volts were recorded by the 20

volt counters, surges in excess of 2000 volts d

indeed occur. 

Conc lus ions 

1. Residential power circuits are subjec

to surge voltages due to two distinct cau

load switching within the house, and exte

nally generated surges that are most like

associated with lightning. 

2. Internally generated surges caused by 

load switching are likely to be repetitive

They can generally be associated with a 

specific device, probably operating errat

ically or exciting some natural frequency 

the wiring system. They are not related 

lightning or disturbances from the utility

Peaks as- high as 2500 volts have been observed. The best single statistical estim

is that 2.4 percent of households of the 

sampled experience these internally gener

repetitive surges in excess of 1200 volts

However, because of the statistical varia

ity in the sample, this value may be as lo

as 1 percent or as high as 4.7 percent. 

Surges may be repeated several times a da

3. The frequency of surges caused by lig

ning is not affected by household electric

devices, but rather by local geographical 

and meteorological conditions. The limite

data in this program reveal several light

ning-caused surge occurrences above 3000 

volts with one reaching 5600 volts. 

4. Independent evidence shows that a sig

icant number of surges above 2000 volts d

occur periodically in residential power li

Acknowledgments 

The contribution of the hundreds of indiv

uals involved in the data collection and the c

tribution of J.E. Lenz for the data on overhea

distribution lines are gratefully acknowledged

References 

Lenz, James E. , "Basic Impulse Insulation 

Levels of Mercury Lamp Ballast for Outdoor 

Applications,'' (Discussion), Illuminating 

gineering, February 1964, pp. 133-140. 

Dixon, W.J. and Massey, F.J., Jr., Introdu

tion to Statistical Analysis, McGraw-Hill, 

New York, 1957. 

Bowker, A.H. and Liberman, G.J., Engineeri

Statistics, Psentice-Hall, New Jersey, 195
York, Philips Technical Library, Springer-Verlag, 

1965. 

O.H. Davie and J. Wood, "An Automatic Cathode-ray 

Oscilloscope Beam Brightening Device for Transient 

sients," Electronic Industries, Vol. 24, April 

1965, pp. 68-71. 

Recordings," Journal of Scientific Instruments, 

Vol. 33, No. 5, May 1956, p. 203. 
Figure 1. Oscilloscope and Camera 

Figure 3a. Surge Counter--Cover Removed 

Figure 3b. Surge Counter Elements--Removed fr

Shield 

DURATION OF FLAT TOP PULSE . microrrcondr 

Figure 4. Response of Surge Counter 
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u 

D 1 

..-I 

u 

U 

4 CO 

,=I 

D 

rg 

a 

$4 al 3 M en $4 

'" 7 i% rn 
Figure 7a. Internal Switching Transient Recorded 

at a Farmhouse (15 such transient surges in 1500 

hours) 

Figure 7b. Composite Record Showing Surges for a 

24-hour Period at a Suburban Home. (Oscilloscope 

is triggered for each surge, plus once every hour, 

resulting in 2 165-volt band of steady state 60 Hz 

voltage. Recordings above 1800 volts are blanked 

out by the oscilloscope.) 

Figure 7c. Single 

corded at the Same 

5-day period surge

corded as follows: 

1500 volts,21 abov

volts. Source was 

a high-voltage tra
Figure 8a. Transient Surges Recorded on Overhead 

Distribution Systems in Charleston, South Carolina 

(3800-volt crest, 300 kHz oscillation.) 

,.*&" 

Figure 8b. Transient Surge Recorded at the 

vice Entrance of a Home in Florida 
SURGE

VOLTAGES

IN

RESIDENTIAL

AND

INDUSTRIAL

POWER

CIRCUITS
Copyright 1970 by IEEE

Reprinted, with permission, from

IEEE Transactions on Power Apparatus and Systems, Vol. PAS-89, No.6, July/August 1970

Significance:

Part 3 Recorded occurrences

At the invitation of the Surge Protective Devices Committee, the 1967 Conference Paper was resubmitted

for consideration as a Transactions paper, with additional information presented on industrial case histories

acquired since publication of the conference paper.

Both waveform information and frequency of occurrence marked the beginning of the IEEE effort toward

characterizing surge voltages in low-voltage ac power circuits, a departure from the traditional unidirectional

and separate 1.2/50 and 8/20 waveforms in use for high-voltage equipment testing. One of the outcomes

of that effort was IEEE Std 587, which eventually evolved into IEEE Std C62.41 and its successive 1980,

1991, and 2002 versions.

Note that the title still refers only to surge voltages, not surge currents. In the mid-sixties, when these

recordings took place, there were very few, if any, surge-protective devices (SPDs) installed in residential

power circuits and the threat was indeed one of surge voltages. After the emergence of ubiquitous

consumer-type SPDs, the results of subsequent monitoring campaigns were drastically changed (See

“Galore” in Part 2) but the information is still valid for the frequency of occurrences to the extent that the

origins of surges have not changed, only the observed levels are now considerably reduced by the

proliferation of SPDs (for which the available surge current becomes a matter of interest).
Reprinted by permission from IEEE TRANSACTIONS ON POWER APPARATUS AND SYSTEMS 

Vol. PAS-89, No. 6, JulylAugust 1970 

pp. 1049-1056 

Copyright 1970, by the Institute of Electrical and Electronics Engineers, Inc. 

PRINTED IN U.S.A. 

Surge Voltages in Residential and Industrial 

Power Circuits 

FRANCOIS D. MARTZLOFF, MEMBER, IEEE, AND GERALD J. HAHN 

Abstract-Special instrumentation was developed for monitoring 

the magnitude and frequency of occurrence of surge voltages in 

residential and industrial circuits. Over a period of 2 years, more 

than 400 locations in 20 cities were surveyed. Monitoring was 

accomplished by automatic recording cathode-ray oscilloscopes and 

simple surge counters. In residential circuits, two significant sources 

of surge voltages were identified : load switching within the house, 

and external surges, most likely associated with lightning, coming 

through the service drop. In industrial circuits, the levels of surges 

are lower than in residential circuits. However, switching surges 

on the load side of the switch can be severe, Internally generated 

surges as high as 2500 volts were recorded during fhis test program, 

and surges due to lightning reaching 5600 volts have been recorded 

on a 120-volt overhead distribution line. 

Paper 69 TP 618-PWR, recommended and approved by the Surge Protectwe Devices Committee of the IEEE Power Group for presentation at the IEEE Summer Power Meeting, Dallas, Tex., 

June 22-27, 1969. Manuscript submitted February 17, 1969; made 

available for printing April 7, 1969. 

The authors are w~th the Research and Development Center, 

General Electric Company, Schenectady, N. Y. 12305. 

T HE succeesful operation of semiconductors and 

insulation systems in appliances and consumer electr

devices may be adversely affected by transient overvolt

occurring on the 120-volt power supply. Detection and mea

ment of these transient surges permits a designer to pro

suitable buihin tolerance, or at least to recognize that the

a need for appropriate suppression or protection. 

Special instrumentation has been developed for detection 

measurement of surge voltages. In the first phase of tes

automatic recording cathode-ray oscilloscopes (CRO) prov

complete information on waveshape, and on magnitude 

frequency of occurrence at a small number of arbitrarily ch

locations. These data, although statistically restricted, 

adequate to demonstrate the existence of the problem, d

some sources, and indicate typical waveshapes. It also bec

clear that there was a need for a larger sample that woul

more statistically valid. I11 the second phase of testing, 100 s
1050 IEBE TRANSACTIONS OX PO\VI.:Il .\PP.LRATUS AND SYSTEMS, JULY/AUGUST 

counters, simple in design and easy to install, were developed especially for this program. These counters were installed in several 

hundred homes in various cities located in the East and Midwest 

of the United States. 

The purpose of this paper is to discuss recordings obtained 

during the two phases of this program and the statistical aspects 

of the results. It is hoped that publication of this paper will 

encourage other investigators to publish their findings. This 

would provide a broader statistical base for verification of the 

frequency and magnitude of surge voltages. 

In regard to industrial circuits, less data have been accumulated, but a number of significant case histories are presented to 

illustrate the problems likely to be encountered in that field. 

IXSTRUMENT~TION 

Recording surge voltages in the field poses special problems. 

For esample, the instruments cannot be continually attended, 

and the signals to be recorded are unpredictable in magnitude, 

polarity, and frequency of occurrence. 

In cooperation with Tektronis, Inc., a type 515 CRO was 

modified to record transients on film, with automatic advance of 

the film after a recording. 

The modifications involved a change in the trigger and sweep 

circuits, as well as removal of all knobs (an important detail 

for an instrument to be left in all types of locations). 

Most oscilloscope trigger circuits are polarized. This often 

causes a loss of recording when the polarity of the initial signal 

is not known. For surge recording, the trigger circuit was modified by feeding to the time base trigger through two OR logic 

diodes the push-pull signal that is applied to the input of the 

oscilloscope delay line. With this modification, the sweep is 

started for either polarity, while the signal is delayed before 

reaching the deflection plate of the cathode-ray tube (CRT). 

In addition, the conventional blanking circuit holds the beam 

in low intensity 'before the sweep starts. 

A second modification changed the sweep from a constant 

sped to a logarithmic speed, fast at the start and slow toward 

the end. This allows the recording of an impulse front with good 

reso!utiou, while providing sufficient duration of the sweep to 

record a long tail. 

Finillly, a relay was added with its coil energized whenever 

the beam sweep is triggered. Through a set of contacts on this 

relay, the film advance sequence in the camera is activated. 

The camera, attached to the scope bezel is a Ueattie-Coleman 

system, acconlmodating 100 feet of 35-mm film, with no shutter, 

and recording ona 24- by 3&mm frame the trace displayed on the 

CRT. Following the sweep, the contact mentioned above closes 

the motor circuit, advancing the film to the nest frame in a few 

seconds. This film transport duration is matched in the oscilloscope trigger circuit by a hold off so that no sweep will occur 

during film advance. 

In order to prevent the film from being fogged by extended 

exposure to the faint glow on the phosphor (caused by imperfect 

blanking of the beam, cathode glow, or light leaks) a builtrin 

timer in the oscilloscope advances the film by one frame every 

hour. This provides an approsimate method for timing the 

occurrence of surges. Since the surge-voltage survey was conducted, an automatic time recording feature has been added 

to give a more precise recording of time at each event. 

Fig. 1 shows this oscilloscope camera system. The relatively 

high cost of this system, its conspicuous presence (e.g., size, 

camera noise, etc.) in a home, and the amount of film to be 

Fig. 1. Oscilloscope and camera. 

Fig. 2. Surge-counter circuit. 

scrutinized franie by frame limit the ~~urnber of locatio

which recordings can be made. However, for conclusions t

on a sound statistical basis, it is necessary to investigate a 

number of locations. To be acceptable to cooperative home o

a transient detector should therefore lend itself to inconspi

installation and s~mple data handling. Thus a device whic

merely be plugged into a wall receptacle, and that has a d

counter indicating the number of surges occurring abo

specified threshold is satil;factory for widespread recording. 

The circuit shown in Fig. 2 was developed for this pu

This device is connected to a wall receptacle by a conven

appliance cord, not a special probe. This connection is s

establishes a tylical final path for a surge impinging upo

appliance connected to this particular wall receptacle

provides pourer for the high-impedance rectifier circuit 

signal input to the trigger-sensor circuit. 

A crudely compensated divider attenuates the incoming 

before application to the silicon symmetrical switch 

This device has the characteristic of turning on abruptly 

ever the voltage across it reaches a threshold, such as 250 

This threshold remains constant for durations as short 

ps. When the SSS turns on, the attenuated surge is applied 

gate of the very-sensitive fast-switching silicon controlled s
MARTZLOFF AND HAHN: SURGE VOLTAGES IN PO\VER CIRCUITS 

DURATION OF FLAT TOP PULSE , micm~q.rconds 

Fig. 3. Response characteristic of counter. 

(SCS). If the polarity of this surge is positive, the SCS turns on, 

allowing the 50-pF capacitor to discharge through the coil of 

the solenoid-actuated counter. A high-impedance divider and 

half-wave rectifier provide a trickle charge 15volt supply for 

the C~O-~F capacitor. The resistance of this divider represents a 

negligible load for the house wiring system, yet is sufficiently 

low to allow some leakage in the electrolytic capacitor. The long 

charging time (several seconds) of the capacitor is not objectionable since the transients to be detected do not have a high 

repetition rate. ' 

Calibration of the circuit is obtained by adjusting the value 

of the divider elements. In these tests, the threshold level was 

set at 1200 volts for one group of counters and at 2000 volts 

for another group. A bench circuit was set up, whereby a surge 

with adjustable level and duration could be superimposed on a 

60-Hz 120-volt power supply. Some consideration was given to 

the need to segregate, or filter out, the surge from the 60-Hz 

power voltage; in this case, however, with the minimum level 

at 1200 volts, the base 170-volt crest represented a small oontribution and was included in the signal detected by the circuit. 

Surges with approximately flat top and durations from several 

to 0.2 ps were applied t,o determine the variation of the threshold 

voltage as a function of surge duration. A typical response curve 

is shown in Fig. 3. The response of this crest-indicating counter 

can be considered sat.isfactory since the oscilloscope recordings 

in homes, as will be discussed later, have indicated that the 

shortest half-period of oscillatory surges is in the order of 2 Ms. 

In the first phase, oscilloscopes were installed at the basement service entrance of homes in the Schenectady, N. Y., area. 

These locations do not represent a statistician's ideal sampling, 

but during the initial phase of the program, the nature of transients, rather than statistical accuracy, was the major subject of 

interest. Later in the program, the range of locations was broadened to include homes in other urban and rural areas, particularly 

in Florida and South Carolina. 

In the second phase, surge counters were installed at unspecified outlets in the homes of engineers in 20 cities in the 

Northeast and Midwest. Two distinct recording periods were 

scheduled: winter, because there is usually a minimum of 

lightning activity at that time of year; and summer, which 

ordinarily includes a maximum of lightning activity. 

Since the oscilloscope input circuit operates at a level of a 

few volts, it is somewhat sensitive to direct radiation of electre 

magnetic noise in the preamplifier, even if there is no signal from 

the probe. In order to discriminate against this type of spurious 

Fig. 4. Surge-counter package 

,200" -- - - - - - - - 

NO COUNT REGISTERE0 

1200 V - 

Fig. 5. ltecording with single-polarity connter. 

indication, the recording procedure included a period du

which the oscilloscope probe was shorted with the ground 

minal remaining connected ,so that spurious signals du

ground loops would be detected. In this manner, any noise e

ing the system could be recorded and later recognized for 

it was in the analysis of the recordings made with the 

circuit removed from the probe. 

The surge counters record only one polarity; in orde

minimize record keeping by the homeowner, the connectio

the cord was not polarized. In the event of an oscillatory 

(which is always quickly damped in these systems), two cas

counting can occur. For instance, the high side of the di

can be connected to the "hot" terminal of the receptacle 

5). If the first half-cycle is positive and exceeds 1200 vol

count is registered. If the first half-cycle is negative, and 

second, positive half is highly damped, no count is regist

If the first half-cycle is well above 1200 volts causing the se

half, in spite of some damping, to exceed 1200 volts, a cou

reg~stered. For the reverse connection, the same would occu

reverse polarity. Thus the actual number of surge occurrenc

both polarities in excess of 1200 volts is between 1 and 2 t

the number indicated by the counter. The objective of th

cording in this test series was only to determine whether or 

surges occurred rather than their exact number. Conseque

the value of the multiplying factor is not very significant. 
TABLE I 

Most Most 

Severe Surge Frequent Surge 

Duration Duration Average Crest (PS or Crest (ps or Surges House Type* (volts) cycles) Type* (volts) cycles) per Hour Remarks 

1 A-1.5 700 10 ps A-1.5 300 10 ps 0.07 

2 A-2.0 750 20 ps A-2.0 500 20 ps 0.14 

3 B-0.5 600 1 cycle B-0.5 300 1 cycle 0.05 

4 B-0.5 400 2 cycles B-0.5 300 2 cycles 0.2 

5 C 640 5 PS too few to show typical 10 total 

6 B-0 .3 400 1 cycle B-0 .3 250 1 cycle 0.01 

7 B-1 1800 1 cycle B-1.0 800 1 cycle 0.03 

8 C 1200 10 ps B-0 .5 300 4 cycles 0.1 

9 B-0 .25 1500 1 cycle same as most severe 0.2 

10 B-0 .25 2500 1 cycle B-0.25 2000 1 cycle 0.4 

11 B-0 .2 1500 1 cycle same as most severe 0.15 

12 B-0.2 1700 1 cycle B-0.2 1400 lcycle 0.06 

13 B-O.l 350 1 cycle too few to show typical 4 total 

14 C 800 15 ps - - - 1 total 

15 B-0.25 800 3 cycles B-0.25 600 3 cycles 0.05 

16 B-0.15 400 15 ps B-0.13 200 30 ps 0.4 

Street pole B-0.5 5600 4 cycles B-0.3 1000 1 cycle 0.1 

Hospital C 2700 9 ps C 900 5 rs 0.1 

Hospital B-0.3 1100 1 cycle too few to show typical 4 total 

Department 

store B-0.5 300 1 cycle B-0.5 300 1 cycle 0.5 

Street pole B-0.2 1400 4 cycles B-0.2 600 4 cycles 0.07 

* A-long oscillation; Bdamped oscillation; C-unidirectional. Number shows frequency in megahertz. 

fluorescent light swit

ing 

lightning storm 

oil burner 

oil burner 

water pump 

oil burner 

house next to 12 

lightning 

rural area 

surges 

lightning stroke near

lightning storm 

lightning storm 

The first recording analysis revealed that some homes were 

subject to frequent surge voltages, some experienced only a few 

isolated surges, and others did not experience any surges in 

excess of the trigger level (300 to 400 volts). Furthermore, 

among those installations where surge volta,ges frequently 

occurred, the surges at some houses were relatively low (rarely in 

excess of 800 volts), while other houses had surges in the range 

of 1200 to 2500 volts. Rates of surge occurrence ranged from 0 (no 

surge in 1 to 2 weeks) to 0.5 per hour, with peak values from 300 

volts (trigger threshold) to 5600 volts. 

At the conclusion of the recording program, a total of 30 

locations, including two overhead distribution poles had been 

monitored for a total of about 10 000 hours. Table I shows a 

detailed analysis of the recordings at 21 locations. Three homes 

and six industrial locations did not produce any triggering with 

the threshold as low as 400 volts. 

Further analysis of some recordings was made by deliberate 

switching of loads in the houses where frequent surges had been 

observed. In some cases, the operation of a specific device (e.g., 

oil burner, fluorescent lamp, pump motor, refrigerator, food 

mixer, etc.) was found to be the cause of the surges. In other 

cases, no amount of deliberate load switching could reproduce 

surges such as those recorded during unattended monitoring. 

The home owner was occasionally able to correlate surge recordings with lightning or power system disturbances. 

A pattern emerged from all this information, showing two 

definite causes of surge voltages in the homes: load switching 

within the house and lightning storms. 

Load Sudching.. Load switching in the house occasionally 

produced transient surges; these aflected only that particular 

house. For any particular house, these transient surges h

waveshape which was consistently repeated with variation

amplitude along the entire film recording. This probably 

sulted from a combination of the switch characteristics an

impedance of the house wiring system; the variations in am

tude were probably caused by variations of the switching 

and/or connected loads. In an industrial circuit, the same 

tition of a particular pattern was also noted [I]. Typical w

shapes of t>he recorded surges are shown in Figs. 6-8. 

.In one mse, it was possible to install an oscilloscope in a h

adjacent to that where repetitive surges up to 1700 volts 

being recorded. The service drops were connected to the 

pole, yet no surges occurring simultaneously were recorde

the second house. 

Lightning: Surge voltages not associated with load switc

within the house were associated with lightning storms. In 

cases, the home owner was able to correlate the film adv

counts with the storm. Although recorded during ligh

storms at two different locations, the surges shown in Fig

and 10 present the interesting characteristic of being oscilla

at a frequency in the range of 300 kHz. The surge. show

Fig. 9 was recorded at the overhead distribution line (o

loscope mounted on the pole), while the surge of Fig. 10 

recorded at the service entrance in a home. The first exh

far less damping than the second; this might be explained by 

lower damping due to lower resistance of the system at the 

than at the end of a service drop. Both of these surges, as 

as most of the other surges recorded during lightning sto

exhibit this oscillatory characteristic at a frequency whic

nearly constant for a particular locality. This constancy sug

that the oscillation of the system followed an excitation ca

by the lightning stroke. A number of surges in the range of 

to 1200 volts were observed during several storms. The maxim
MARTZMFF AND HAHN: SURGE VOLTAGES IN POWER CIRCUITS 

Fig. 6. Residential surges, 24hour composite. Black band is 

fl70-volt sweeps at hourly intervals. 

Fig. 7. Residential surge, oil burner ignition. 

Fig. 8. Industrial circuit. Surge due to equipment maintenance; 

note digital timer record. 

Fig. 9. Surge recorded on street pole in Charleston, N. C. 

Fig. 10. Surge recorded at service entrance of Florida home. 

TABLE I1 

NUMBER OF HOUSES WITH REPETITIVE 

SURGE ACTIVITY ABOVE 1200 VOLTS 

Number House

of Recording with 

Homes Period Repetit

Location Surveyed (weeks) Surge

Providence, R. I. 4 

Cleveland, Ohio 28 

Auburn, N. Y. 12 

Lynchburg, Va. 3 

Syracuse, N. Y. 8 

Chicago, Ill. 23 

Ashland, Mass. 24 

Holland, Mich. 6 

Louisville, Ky. 10 

Somersworth, N. H. 50 

Plainville, Conn. 5 

Asheboro, N. C. 24 

Fort Wayne, End. 38 

DeKalb, Ill. 14 

2-6 none 24 none 2-3 none 2-3 none 1-2 1 

1-6 none 1-2 1 

2-10 none 2-6 none 1-2 1 

10 none 1-2 none 14 3 

3-12 none 

TABLE I11 

SURGE COUNTERECORDINGS ABOVE 1200 VOLTS 

(SPRING, SUMMER, AND FALL) 

Number Total Numb

of Homes of 

Location Homes X Weeks Surge

Providence, R. I. 6 60 1 

Ashboro, N. C. 13 85 none DeKalb, Ill. 11 60 2 

Sornersworth, N. H. 3 48 1 

Chicago, Ill. 12 58 none Cleveland, Ohio 8 106 1 

Decatur, Ill. 12 72 2 

Holland, Mich. 7 56 none Auburn, N. Y. 3 70 none Springfield, Pa. 1 24 none Ashland, Mass. 6 72 none Pittsfield, Mass. 3 60 1 

Plainville, Conn. 3 60 none Lynchburg, Va. 3 - 15 none 

Total 91 846 8 in 

8 hom

surge voltage recorded was 5600 volts; several other su

recorded during the same period were in excess of 4000 v

c- 3 

Counters 

With the two causes of transients identified by the oscillos

rnessurements, the surge counters were applied in two sepa

programs. First, during the winter months, the counters 

installed in a large number of houses for periods of 1 or 2 we

the objective was to determine how many houses susta

repetitive surges. Second, during spring, summer, and fall, 

counter was left at one or two locations for periods of 9 t

weeks; it was known from the first test that these homes 

not, subject to load switching surges. The objective wa

determine the frequency and characteristics of externally ge

ated surges, presumably caused by lightning. 

The first period produced the data shown in Table 11, and 

results obtained during the second period are shown in T

111. 
1054 IEF,E TRXNS.\CTIONS ON I'OWElt APPARATUS AND SYSTKMS, JULY/.~UGUST 

Internally Generated Surges 

The data in Table I1 show that 6 houses, or 2.4 percent, 

were subject to repetitive surges from anlong a total of 250 

homes sampled. The true percentage doubtless differs somewhat 

from 2.4 percent due to statistical variations. 

However, one may be 90-percent confident that the true percentage is between 1.0 and 4.7 percent.' This band could be 

narrowed by taking additional samples. However, it should be 

noted that the precision is proportional to the square root of the 

sample size. Thus four times the number sampled, or 1000 

homes, would be necessary to cut the size of the statistical 

error band by approsimately one half. Since the preceding results 

refer to statistical variations only, they do not take into account 

possible bias~s due to such factors as restrictions in selecting 

members of the sample (principally engineers in a number of 

designated locations) or the time of year (winter months). 

The probability of internally generated surges undoubtedly 

varies among economic groupings (i.e., the devices in use in 

homes probably vary with the economic status of the resident); 

however, devices found to generate surges (i.e., furnaces, refrigerators, etc.) exist in most homes. 

Extm~ally Generaled dwges 

Results from the second testing period that was concerned 

with externally generated surges are shown in Table 111. From 

39 counters installed in a total of 91 homes in 14 localities, a 

total of 8 occurrences in 6 separate localities were observed during 

an equivalent exposure time of 846 weeks. A ninth occurrence 

was disregarded in this analysis because it occurred in the same 

home during the same storm. Of the two pairs of occurrences 

which took place in the same location, one pair occurred during 

the same storm and the second involved two occurrences at 

different times. 

Analyses could be conducted based on the following alternative 

assumptions. 

1) Voltage surges above 1200 volts occur only during the period 

of the year that the counters were installed in the homes. Thus 

although the counters were in homes for only part of the year, the 

time involved (i.e., the summer months) was so chosen that no 

further surges would have been noted even if each counter had 

been run for 52 consecutive weeks. The average number of 

surges per year would then be Bstimated as 8/39, or 0.205, with a 

90-percent confidence band of 0.102 to 0.370. 

2) Voltage surges occur randomly at a constant rate throughout 

t.he year. Thus a counter which was in use 9 weeks, on the 

average, wou!d be subject to a third as many surges as a counter 

in use for a period of 27 weeks. Under this assumption, a total of 

8 surges observed in a total time equivalent to 16 years (846 

weeks) yield an estimated average of 0.5 surges per year, with a 

SO-percent confidence band of 0.25 to 0.90. 

Using these two extreme assumptions, a range could be established for the estimated number of surges per year. The preceding calculations refer only to single-polarity surges. If all 

surges are being considered, the given value must be multiplied 

by a value corresponding to the additional proportion of opposite 

1 This result is obtained by the well-known method of setting confidence intervals for a percentage from a sample. Further details 

may be found in statistical texts [3]-(51. 

polarity surges above 1200 volts which do not also resu

positive surges above 120 volts. This multiplying fact

prohably ahout 1.6. 

Lightning-induced surges are likely to affect more than 

house when they occur. Local geographical and meteorolo

conditions are critical influences on these surges; however, 

factors could not be considered in this preliminary investiga

To relate the preceding data to risk of appliance failure

given values must be modified by the probability that a 

above 1200 volts would cause failure of operating applia

Failure effects would vary with different appliances. 

Possible Further Analysis 

A more refined analysis to estimate the probability of vo

surges per lightning storm is possible if the geographical loc

of the homes, the occurrence rate of lightning storms durin

testing period, and exact dates at which voltage surges occ

considered. The resulting values can then be used in conjun

with information given in [8], [9] to calculate the probabilit

voltage surge in any specified geographic area and season. 

an analysis would remove the need for making one of the 

alternative assumptions stated previously and lead to a s

set of estimates. However, this would require more det

data than could be collected in this program. 

Finally, it is noted that if one has knowledge of the a

voltage surges, rather than merely the information conce

whether or not a surge above 1200 volts occurred, a more 

tive analysis is possible. In this case, for example, proba

plotting and other techniques based upon the statistical th

of extreme values [5], [7] might well be applicable. 

The surges which have been recorded in this program occ

during normal operation of the household, with no knowled

the connected load situation at the time of occurrence. 

The question of energy involved in the surge is related t

impedance of the system since these recordings provide vo

data only. Surge impedance measurenlents of a house w

cable indicate a value of 100 to 300 ohms for a typical br

circuit so that the surge impedance at the service entrance c

be in the order of 5 to 10 ohms. However, this low value e

only for the travel time (i.e., a fraction of a microsecond). 

nected loads will have a lower impedance than that of the br

circuit. This value will be dependent upon frequency when

inductive components are present. These loads will absorb 

of the energy of the surges and thus lower their peak. 

Devices such as motors and transformers have solid insul

and such a long history of successful application that 

performance is not in question. Perhaps unusual failures ca

explained by extreme values of surges as indicated by the da

Defective wiring practices (e.g., pinched insulation, reduce

clearances in wall boxes, etc.) will cause air flashover wi

without 60-Ha. power follow. In fact, one house was bro

to our attention because of complaints of sparking in a 

fixture. With the switch in t,he ground wire and the fram

tached to a grounded pipe, flashover at 1700 volts was obse

in correlation with the start of an oil burner in the house. 

defective light fixture was acting as a voltage limiting gap fo

house. 
MARTZLOFF AND HAHN: SURGE VOLTAGES IN POWER CIRCUITS 

Appliances containing semiconductors and directly exposed 

to the line transients may be more vulnerable. Actually, the 1200- 

volt threshold level was selected as the result of this consideration. It is interesting to note that, although a number of surges 

above 2000 volts were recorded by the oscilloscopes, the few 

surge counters calibrated for 2000 rather than 1200 volts did not 

produce any recording above 2000 volts. 

An independent study of clock motor failures produced information on failure rates versus withstand levels. This study 

was very pertinent to the surge counter program since thousands 

of clocks are connected at all times to the power system. Over a 

per~od of 3 years, failure rates were correlated with the insulation 

level of the coils. A very significant 100 to 1 drop in failure rate 

resulted from an increase in withstand voltage from approximately 2000 to approximately 6000 volts. This shows that, even 

though no surges over 2000 volts were recorded by the 2000-volt 

counters, surges in excess of 2000 volts do indeed occur. 

The authors have been associated with a number of investigations where surges were suspected to be the cause of equipment problems. In the industrial environment, isolated cases 

tend to attract more attentioh than in residential circuits. 

The few case histories briefly summarized in this paper illustrate 

the types of problems likely to be encountered, where often 

surges are not in fact the cause of the problem, but where the 

presence of the test crew at the site precipitates a more thorough 

evaluation of the problem and sometimes reveals an unsuspected 

new fact. 

On the occasion of these investigations, the surge counters 

were installed at the same time on the system and left for several 

weeks or months at the site whenever possible. So far, in over 

15 locations, no surge over l2OO volts has been recorded on 240- 

or 480-volt buses ("mains"). On the other hand, severe surges 

have sometimes been recorded on the load side of the switch. 

However, these load side surges are associated with the subsystem operation and can be controlled (if recognized) by the 

subsystem designer or operator, in contrast with the surges on 

the mains that affect all users in the house, building, or plant, 

and on which they have little control. 

Problem 

Occasional flashover in a 480-volt distribution system at a 

steel welding shop. 

Suspect: Switching surges associated with arc welding. 

Investkdion: Install surge recording o~cilloscopes on the bus. 

Result: No surges recorded. 

Second Investigation: Power factor capacitors had been installed 

on the bus, but this fact had not been revealed by the initial 

discussions; their presence on the bus practically eliminated 

the possibility of surges on the bus. (Switching the whole bus 

system was tested and produced no surges in this case.) Final 

conclusion was contamination of the insulation in the polluted 

atmosphere. 

Failures of a 480-volt saturable reactor in a motor control 

system. 

Suspect: Switching surges associated with contactpr operation. 

Investigation: Record surges on site during deliberate

trolled switching of the contactor. 

Result: Contactor bouncing and restrike produce a num

steep front (0.1 ps) surges on the winding, causing ex

turn-to-turn stress. 

Problem 

Failures of rotor windings in 440-volt induction moto

crane system. 

Suspect: Switching surges associated with contactor ope

Inoestigation: Record surges with monitoring oscill

during deliberate, controlled switching of the contactor. 

Result: No excessive surges found; however the tes

notices during the on-site test that the overspeed protec

the motor control had been bypassed by the user. 

Problem 

Frequent blowing of fuses in a power factor correction cap

bank. 

Suspect: Switching surges. 

Inwstigation: Record current in the fuse and system v

during switching operation. 

Result: Contactor bounci?g produces a number of 

current surges exceeding the rms capability of the fuse. 

Problem 

Failures of lamp ballasts in an industrial plant. 

Suspect: Switching surges. 

Inwstigation: Install monitoring oscilloscopes. 

Results: No surges found in several weeks of monitori

further problem. 

Conclusion: The best surge suppressor is a surge monitor

1) Residential power circuits are subjected to surge vo

due to two distinct causes: load switching within the hous

externally generated surges that are most likely associate

lightning. 

2) Internally generated surges caused by load sw

are likely to be repetitive. They can generally be associated 

specific device, probably operating erratically or exciting 

natural frequency of the wiring system. They are not rela

lightning or disturbances from the utility. Peaks as high a

volts have been observed. The best single statistical es

is that 2.4 percent of households of the type sampled expe

these internally generated repetitive surges in excess of 

volts. However, because of the statistical variability 

sample, this value may be as low as 1 percent or as high 

percent. Surges may be repeated several times a day. 

3) The frequency of surges caused by lightning is n

fected by household electrical devices but rather by 

geographical and meteorological conditions. The limited 

in this program reveal several lightning-caused surge occur

above 3000 volts with one reaching 5600 volts. 

4) Independent, evidence shows that a significant num

surges above 2000 volts do occur periodically in resid

Dower lines. 

5) Industrial power circuits appear less likely to be sub

to surges on the mains. However, switching surges in subsy

can originate at the switch and affect the loads. 


Part 3 Recorded occurrences

This unclassified (available to anyone) report was prepared to provide more details – until then contained

in classified internal reports or summarized in the two IEEE papers reprinted in this Part 3 – on the

measurements made in the 1963-1967 period. 

Only brief remarks are made in this report on possible suppression methods. Papers included in Part 6

(Tutorials), Part 7 (Mitigation techniques) and Part 8 (Coordination of cascades SPDs) provide information

on protection techniques prior to and after the emergence and widespread use of metal-oxide varistors.
GENERAL@ ELECTRIC 

General Electric Company 

Corporate Research and Development 

Schenectady, New York 

TECHNICAL INFORMATION 

SERIES 

ITHOR 

Martzloff, FD 

I 

IIGINATING CORPORATE 

IMPWENT Automation and Control Laboratory RESEARCH ANO DEVELOPMENI 

SCHENECTADI, N.V. 

I 

TLE 

Transient Overvoltages 

in Secondary Systems 

Transient overvoltages have been recorded in secondary systems for 

a period of four years, using recording oscilloscopes and surge counters. 

Conclusive evidence has been accumulated on the occurrence of 

surges at potentially damaging levels on 120 volts residential circuits. 

Less frequent and less severe surges were found on commercial and 

industrial circuits. 

This report is a summary of measurements made from 1963-1967 

and has been adapted from a 1967 internal report. An up-to-date 

bibliography is included. 

SUBJECT 

transient overvoltages 

GE CLASS 1 

NO. PAGES 20 

El WORDS 

surge 

81CRD121 

DATE May 1981 

INFORMATION PREPARED FOR 

Additional Hard or Microfiche Copies 

Available From 

Technical Information Exchange 

Bldg. 81 Room A1 33, Schenectady, N.Y., 12345 
TRANSIENT OVERVOLTAGES IN SECONDARY SYSTEMS 

F. D. Martzloff 

I. INTRODUCTION 

The increasing use of semiconductors in consumer and commercial appli

cations has increased the risk of component failures due to transient overvolt

ages. This situation was recognized by the General Electric Company in the 

early sixties, and a program was initiated in 1962 for the purpose, among 

others, of recording transient overvoltages in low voltage systems in order 

to obtain factual information for an estimate of this risk. 

Transients were recorded with oscilloscopes at a numbe~of locations, in 

order to obtain data on representative waveshapes. These data were supplemented by a second project in which a large number of locations were monitored, using a fixed threshold surge counter especially developed for this 

program. 

This report combines a presentation of the new results with a review of 

earlier data, in order to summarize present knowledge on the occurrence of 

transient overvoltages in secondary systems, with references to related area

of effects on semiconductors and transient suppression. 

The cause of transients, the recording and the results are discussed, and 

conclusions based on statistical considerations are presented. 

11. CONCLUSIONS 

1. (a) Two major causes of transient overvoltages exist in residential 

secondary circuits: surges generated within the house by some device such a

relays, contactors, mercury switches, etc., and surges fed in from the pow

service entrance, primarily lightning- induced. 

(b) Commercial or industrial secondary systems are not subjected to t

internally generated surges found in residential circuits, as they are "stiffer" 

than the latter. 

2. Internally generated surges above 1200 volts are likely to occur at 

frequent intervals (one or more per day) in about 2. 5% of all U. S. households. 

3. Lightning-induced surges may occur at a rate of 0.1 to 0. 9 per household and per year. Statistical evidence in this case is not as firm as in the 

case of the internally generated surges. 

' 4. These surges can definitely cause failures in unprotected appliances, 

especially those containing semiconductors directly exposed to the line voltage

5. A number of commercially available devices offer various amounts of 

protection at various costs. The need for built-in protection versus no protec

or protection external to the appliance at the owner's expense is a subject of 
discussion rather than a hard fact, since it involves variable parameters such 

as nuisance costs, prestige, duration of warranties, etc., in addition to the 

simple probability of failure considerations. 

6. In spite of the impossibility of making definitive and all -encompassing 

conclusions, the author hopes that this report will increase the awareness of 

the occurrence of potentially damaging surge voltages on residential secondary 

circuits and promote a better anticipation of associated problems, which should 

ultimately increase the reliability of electronic products. 

111. TRANSIENT MEASUREMENTS IN SECONDARY CIRCUITS 

The measurement of transients was conducted over a period of three years; 

in 1962 and 1963 with oscilloscopes and in 1965 with surge counters designed 

and built in 1964. The objective of the oscilloscope measurements was to explore the characteristics (waveshape, magnitude) of surges, while the objective 

of the surge counter measurements was to establish a broad base for the statistical treatment of the results. 

1. Oscilloscope Measurements 

Table I shows an analysis of the surges recorded in terms of most severe, most frequent, and average number per hour at each of 23 locations. 

Briefly, the oscilloscopes are modified Tektronix 51 5 oscilloscopes where 

a nonpolarized sweep trigger is provided by the transient overvoltage occurring 

in the circuit being monitored. A 35 mm camera, with no shutter, continuously 

monitors the blanked-out screen until a surge triggers the logarithmic sweep, 

at which time the transient is displayed on the screen and recorded on the film, 

and the motor-driven camera advances one frame. 

This equipment, not without electronic and mechanical incidents, provided 

the means to monitor the voltage in homes and commercial buildings for a 

period of several days and thus establish patterns for transients recurring within 

this time period. 

Typical waveshapes (corresponding to severe cases for amplitude but typica

as far as shape is concerned) are shown in the oscillograms of Figs. 1, 2, and 

These oscilloscope measurements indicated that potentially damaging surge

can occur very frequently in some households, while other households were 

relatively free from frequent disturbances. In some cases, the occurrence of 

frequent surges was correlated with the operation of an appliance such as a 

furnace, refrigerator, etc. 

Measurements in larger secondary systems, i. e. , commercial or industria

buildings, did not record frequent, internally generated surges similar to those 

found in households. Lower amplitude, less frequent occurrences were found, 

believed to be associated with switching surges or lightning-induced surges involving the complete local power grid. 
2. Recordings with Surge Counters 

The oscilloscope measurements clearly established the dual source of 

surges in households, internal or external. In order to evaluate the possible 

effect of these on a national scale, a program of designing and building about 

100 surge counters for installation in as many households as possible was 

initiated in 1964. These were installed late in 1964, and the readings monitored and analysed in 1965. 

2. 1 Test Plan 

The recording of household surges was divided into two separate periods, 

each with distinct objectives. A first recording period held in winter and early 

spring covered short periods at each of a large number of residences, in order 

to investigate the proportion of households subjected to frequent internally gener

ated surges. 

, A second recording period held in late spring and summer was organized at 

a reduced number of locations with longer periods, in order to investigate the 

frequency of lightning-induced surges at a number of specific locations. 

A related program was also carried on at two locations where frequent 

internally generated surges were occurring, to demonstrate the effectiveness 

of the suppression obtainable from a small Thyrector stackconnected at the 

outlets. 

The surge counter design has been described in a previously published 

paper. (l) It provides cumulative counting of surges in excess of 1200 V or 

2000 V for durations above 0.2 ps when plugged into the 120 V outlet. * 

Briefly, these recorders consist of a solenoid driven counter, with a 

storage capacitor discharged into the solenoid when triggered by a surge in exce

of a set threshold, of one polarity. The threshold level of the counter was set 

at 1200 volts for three quarters and at 2000 volts for one quarter of the counters

The storage capacitor was held charged by a high resistance rectifier power 

supply drawing power from the line being monitored. 

The choice of the 1200 volts and 2000 volts threshold levels was the result of data on the performance of semiconductors, especially diodes and 

SCR1s under transient inverse voltage. It seems that appliance circuits containing diodes or SCRts connected either directly or by low impedance components to the incoming 120 volt line may fail when the surges on this line 

exceed 1200 volts. On the other hand, a device with some degree of filtering, 

such as an input transformer, may require in the order of 2000 volts on the 

incoming line to pass on 1200 volts to the semiconductor(s) in the circuit. 

*These recorders were designed specifically for installation in 120 V outlets and 

have a relatively low input impedance. Therefore, they may load down a circuit if, for instance, installed on the load side of a switch. 
2. 2 Internally Generated Surges Investigation 

This investigation was carried on with the cooperation of individual engineer

at 18 departments, who installed the counters in their homes and returned the 

records to the author for compilation. 

The recording period lasted from December 1964 to March 1965, corresponding to an expected minimum of lightning activity, and involved about 250 homes. 

Complete results are shown in Table 11. 

The results are summarized as follows: 

1. Six homes in a total of 250 homes are subjected to repetitive surges in 

the 1200 to 2000 volt range, which are most likely limited to each of the six, 

i. e. , not affecting adjacent houses. This represents a percentage of 2. 4% of 

the houses surveyed where potentially damaging repetitive surges can occur. 

The statistical validity of this percentage is discussed below. 

2. Three isolated random surges were recorded, associated with no known 

or suspected system disturbances. 

The recording results were analyzed by G. J. Hahn, who prepared the follow

ing discussion. 

Statistical Aspects of the Recording Results 

The data indicated 6 voltage surge situations in a total of 250 homes sampled

This indicates a rate of 2. 4% in the sample. One would expect that the true 

voltage surge rate in the population from which the random sample was taken 

would differ from the sample rate due to statistical variations. However, one 

may be 9970 confident that the voltage surge rate in the population is between 

0. 6'70 and 6. 3% and 95y0 confident that the true proportion is between 0. 970 and 

5. 3%. 

Assuming now that more homes had been surveyed, one can wonder how muc

narrower the band would be. In response to this question, if we had observed 

12 voltage surges in 500 homes, the 99% confidence interval would have been 1. 07

to 4. 8% and the 95% interval would have been 1. 270 to 4. 2%. Similarly, with 24 

voltage surges in a sample of 1000 the 99% confidence interval would have been 

1.3% to 4. 070 and the 9570 confidence interval would have been 1. 57'0 to 3. 6% 

The above results refer to statistical variations only, and thus represent 

limits on the proportion of voltage surges in the population from which the sampl

was selected. Thus, they do not take into account any possible biases that might 

have been introduced by such factors as restrictions in selecting members of 

the sample (principally GE engineers in a number or designated locations) or the 

time of year (winter months). 

The statistical calculations are based on the well-known method of establishing confidence intervals for the binomial parameter using the Poisson 

approximation. Further details may be found in statistical 33 4, 
Discussion of the Results 

Within the limitation that the homes surveyed are assumed to be typical of 

all residential buildings where new solid state appliances are likely to be found, 

the ITo to 570 probability of repetitive surges is not negligible. That is, electronic appliances with a surge damage threshold below 1200 volts are likely to 

suffer in-warranty failures at a rate of 170 to 5% of sales. 

While the small number (6) of locations detected in this survey may appear 

to be small and thus intuitively unconvincing, there is a 99% level of confidence 

that the actual rate is 0. 6 to 670. * 

Continuing the data accumulation by increasing the number of homes surveyed will of course increase the validity of the conclusions, but not by a very 

large amount; for instance, if the same percentage (2. 470) had been obtained 

from a sample of 1000 homes (an effort 4 times as large as the one reported 

here) the range of probability for a 9970 confidence level would be reduced to 

1. 3 to 470 compared to the present 0. 6 to 6%. This offers some incentive for 

increasing the number of homes surveyed, especially at locations where only 

a few homes were surveyed, but again, the return of better data are disproportio

to the effort that could be applied in one year. 

2. 3 Externally Generated Surges 

2. 3. 1 Test Procedure 

At the conclusion of the repetitive surge detection program the surge counter

were installed for an extended period at a few homes for the duration of the 

summer, or at least for several weeks. Presumably, these homes were not 

subjected to repetitive internally generated surges (as confirmed by the recordings), so that only externally generated surges would be recorded. Except when 

a correlation was established with a lightning storm, there is no available information on the cause of the surge, so that lightning as well as system switching 

surges are included in this statistic. 

Table I11 summarized the recording data. A complete discussion of the 

results by G. J. Hahn follows. 

2. 3. 2 Analysis of Voltage Surge Data and Some Implications 

A. Introduction 

Data have been obtained on single polarity voltage surges above 1200 volts 

on 39 counters installed in a total of 91 homes in 15 localities for a total exposure time of 841 weeks. A total of 8 occurrences were observed during this 

YgThe fact that the counters record only one polarity is immaterial in this cade: 

the point was to detect those houses which had repetitive surges, not the number of surges at each location. (With random polarity in the surges, and some 

damping in oscillating surges, there is a factor of more than one and less than 

two to be applied to the number of surges indicated'in order to obtain the total 

number of surges of both polarities. ) 
period. From this information, it is desired to draw some conclusions concerning the expected number of such surges per home per year. The total ti

per counter ranged from 9 weeks to 48 weeks, with the average time per dev

being 22 weeks. The program was so planned that all devices would be in ho

during the summer months, that is, the period during which lightning storms

and thus voltage surges, are most likely to occur. 

B. Results of Analysis 

Analyses were conducted based on the following two alternate assumption

1. Voltage surges above 1200 volts occur only during the period of year 

that the counters were installed in the homes. Thus, although the counters w

in homes only for parts of the year, the time involved was so chosen (name1.y

the summer months) that no further surges would have been noted even if eac

counter had been run for 52 consecutive weeks. 

2. Voltage surges occur completely randomly throughout the year. Thu

a counter that was in use only 9 weeks would on the average have only a third 

as many observed surges as a counter in use for a period of 27 weeks. 

The above two assumptions clearly represent extremes. Thus, although 

neither is very realistic, results based on such assumptions permit one io ob

tain bounds within which one can reasonably expect the true expected number 

surges to lie. The results are as follows: 

Under assumption 1: A total of 8 surges occurred on 39 counters, thus 

the best estimate of the expected number of surges per home per year is 

8/39 or 0.205. This estimate is subject to statistical error, since only a 

limited number of counters were involved. However, from the appropriate 

statistical calculation^(^^ 4, we can state with 90% confidence that the average 

number of surges is between 0.102 per year and 0.370 per year. 

Under assumption 2: A total of 8 surges were observed in a total of 16. 

years of testing. Thus the expected number of surges per year is 8116.173 o

0. 495. The 90% confidence interval on this estimate is 0. 246 surges per yea

to 0. 892 surges per year. 

The above calcula?lons refer only to single polarity surges. If one is 

ir:terested in all surges, the given values need be multiplied by a value corre

sponding to the additional proportion of opposite polarity surges above 1200 v

which do - not also result in positive surges above 1200 volts. This multiplyin

factor is probably in the order of 1. 6, accounting for the damping between th

first and second 1 / 2 cycle of an oscillating surge. 

Some additional assumptions are also involved in the analysis. Although 

these assumptions are not strictly met, they are probably not sufficiently incorrect to critically affect the validity of the analysis. These assumptions a

1. The homes were selected strictly at random. 

2. The voltage surge rate is the same from one home to the next. 

3. All voltage surges of one polarity during the period of installation we

recorded. 
If it is desired to relate the above data to probability of appliance failure, 

one must clearly multiply the given values by the probability that a surge above 

1200 volts would lead to appliance failure assuming the appliance is in use during the time of the lightning storm. (This would clearly be different for a toaster 

from what it would be for a radio. ) If one is interested only in failures during 

the warranty period an additional adjustment would be required. 

C. Possible Further Analysis 

A more refined analysis is possible by taking into account the geographical location of the homes, the occurrence rate of the lightning storms during 

the period under examination in these homes, and the exact dates at which the 

voltage surges occurred in order to obtain a measure of the probability of a 

voltage surge per lightning storm. The resulting values can then be used in 

conjunction with the information given in Ref. 4 to calculate a probability of 

voltage surge in any specified geographic area during a particular part of the 

year. Such an analysis would remove the need for making one of the two alternate assumptions stated above and lead to a single set of estimates. However, this would require more detailed data than could be collected in this 

program. 

2. 4 Surge Suppression Experiment 

At two of the locations where repetitive surges were found, a prototype 

surge suppressor was installed at the receptacle into which the counter was 

plugged. This suppressor consists of a Thyrector packaged for plug-in installation at receptacles, and is currently under evaluation by the Semiconductor 

Products Department for the home market. The counters were installed in 

alternating periods with and without suppressors, and the recording rates compared. A counter was especially modified to record surges over 60Q volts in 

order to roughly evaluate the effectiveness of the suppressor in reducing the 

surges of 1200 volts or more occurring without suppression. 

Location No. 1 - (Home in Ft. Wayne, Ind., refrigerator identified as source

Dates No. of Surges Above No. of Surges Above 

(1 965) Conditions Days 1200 Volts Recorded 600 Volts Recorded 

3/11to8/10 Nosuppressor 152 252 Unknown 

8/10to9/16 Suppressor 3 7 0 Unknown 

9/16 to 11/12 No Suppressor 57 107 Unknown 

10/29 to 11/12 No Suppressor 14 Unknown 11 

11/12to 11/26 Suppressor 14 0 0 

1/24 to 1/31 No Suppressor 7 Unknown 3 

1/31 to 218 No Suppressor 7 Unknown 12 
Location No. 2 - (Home in Newton, Mass., oil burner identified as source

Dates No. of Surges Above 

(1 966) Conditions Days 600 Volts Recorded 

5/10 to 5/17 No Suppressor 7 8 

5/17 to 5/24 Suppressor in 7 0 

5/24 to 5/31 No Suppressor 7 0 

There were eight recordings which occurred in the first seven days withou

the use of the suppressor. On or about May 18, the warm weather really set 

in, and it is doubtful that the burner went on after that, which explains the 

absence of surges in the second period without the suppressor. 

The results of the experiment at both locations are quite conclusive for 

the effectiveness of the Thyrector in suppressing the internally generated surg

from a potentially damaging value in excess of 1200 volts to an innocuous value 

of less than 600 volts. 

IV. DISCUSSION OF THE TRANSIENT MEASUREMENTS 

1. Distribution of Magnitudes 

The histogram, Fig. 4, shows the distribution as recorded by the oscilloscopes; the low frequency shown below 500 volts is due to a deliberate cutoff in the sensitivity of the oscilloscopes (in order to limit the number of oscilloscope triggers). This is to be compared with the distribution reported in 

Ref. 5 and reproduced on Fig. 5, where the frequency increased by three decades with a threshold lowered from 400 to 50 volts. 

The highest internally generated surge was about 2800 volts, with the 

majority of the surges in the 1000 to 1500 volts range at locations where these 

were occurring frequently. 

Lightning surges were found as high as 5. 6 kV; however, the small total 

number of surges recorded makes it difficult to present definitive conclusions. 

2. Distribution of Surge Generating Appliances 

The 2. 470 estimate derived from the surge counter survey has already bee

discussed from the statistical point of view in Section 111. The real problem, 

however, is that of trading off minimum manufacturing cost (and, therefore, a 

calculated risk of failure) against complaint expenses. This is certainly the 

prerogative and responsibility of individual departments, and not that of the 

CLUL~IUL-. ItIU w cv CL , IL IV 11~pccl LllaL Lllc daLa yr cu~rrL~J lr-r G will ooalba-ibu* 0 a 

factual input to this trade-off. 
V. EFFECTS OF TRANSIENT OVERVOLTAGES ON SEMICONDUCTORS 

Previous investigations have indicated some significant factors to be 

considered when semiconductors are exposed to transient voltages in the 

reverse direction (forward direction generally results at worst in one-half 

cycle forward conduction into the load, which is not catastrophic with the AC 

power sources): 

1. Failure modes, nonavalanche rectifiers 

The nonavalanche (or at least the non-"controlled avalanche") 

rectifiers fail by breakdown of the insulation surface at the edges 

of the wafer. This breakdown is a characteristic of the semiconductor geometry and materials, and has no direct relation to 

the PRV rating of the device. 

Application of a reverse voltage transient during forward conduction produces failure at levels substantially lower than when the 

transient is applied during blocking. 

No significant difference was found between the failure level for 

single vs multiple (several thousands) application of overvoltages. 

For steep pulse fronts (shorter than 1 us), the failure level increases with rate of rise. 

Aging of semiconductors by storage at high temperature does not 

affect the failure levels. 

Energy level of the transient, i. e., duration for a specified voltage appearing across a specified impedance, does not affect the 

failure level. 

2. Failure Modes--Controlled Avalanche Rectifiers 

The energy dissipating characteristic of the device can hold the 

transient voltage level below surface breakdown level, however, 

long pulses may heat the material so much as to produce: 

bulk failures by hot spot 

an increase in the voltage across the device such that surface 

breakdown voltage is reached 

Therefore, care and not indiscriminate selection is required in 

applying avalanche characteristics for circuits exposed to "long" 

transients. 

VI. SUPPRESSION METHODS 

Transient suppression can be accomplished either at the source or at the 

sensitive load. System designers may be able to specify the suppression at the 

source, but the majority of users will have to protect their appliances at the 

load, or at some location of their system. For instance, in a home, the suppressor may be installed at the service entrance or at an outlet. The service 

entrance location is optimum for protection against incoming surges, while the 
outlet location is optimum for protection of a single appliance at that outlet. 

Nevertheless, a substantial protection is obtained throughout the house if a 

suppressor is installed at one outlet only. 

While protective devices are fairly well known, their application can 

lead to some pitfalls. (6) For large and expensive equipment, it seems more 

acceptable to provide some investment in surge protection, which can then 

be specified by technical performance rather than cost. On the other hand, 

mass market devices are subject to economic criteria which make the selection of a surge protector a more delicate trade-off. 

VII. REFERENCES 

J. Martzloff, F. D. and Hahn, G. J., "Surge Voltage in Residential and 

and Industrial Power Circuits, If IEEE Transactions on Power Apparatus 

and Systems, Vol. PAS-89, July/August 1970, pp. 1049-1056. 

2. Dixon, W. J. and Massey, F. J. , Jr. , Introduction to Statistical Analysis, 

McGraw -Hill Book Company, Inc. , New York, 1957. 

3. Bowker, A. H. and Lieberman, G. J. , Engineering Statistics, Prentice - 

Hall, Inc., Englewood Cliffs, New Jersey, 1959. 

4. Brownlee, K. A., Statistical Theory and Methodology in Science and 

Engineering, John Wiley & Sons, Inc. , New York, N. Y. 

5. Bull, J. H. and Nethercot, W., "The Frequency of Occurrence and the 

Magnitude of Short Duration Transients in Low Voltage Mains, - The 

Radio and Electronic Engineer, September 1964. 

6. Martzloff, F. D., If Coordination of Surge Protectors in Low -Voltage 

AC Power Circuits, If IEEE Transactions on Power Apparatus and 

Systems, Vol. PAS-99, ~anuar~l~ebruary 1980, pp. 129-133. 

VIII, ACKNOWLEDGMENTS 

The author wishes to acknowledge the support received from the department

involved in the pooled program, involving financial support from the department

as well as the cooperation from the hundreds of individuals who took the surge 

counters home and returned the records to the author. 

The contribution of G. J. Hahn, Statistician, Research and Development 

Center, in interpreting and discussing the statistical aspects of the results is 

acknowledged. 
TABLE I 

DETAILED ANALYSIS OF RECORDED SURGES 

1 mST SEVERE SURGE NOST FREQUENT SURGE LVERAGE 

WER DURATION OF 

' SURGES OBSERVATION REHARKS 

1 HOYR / WRS I - 

CREST 

VOLTS 

:-TO -PK DURATION CREST PK-TO-PK DUBA ON us 'SK VOLTS gcgs VOLTS VOLTS fTYPE 

D.P. Shattuck 

- - -- 

K.N. Mathes 0- 14 / 250 I nuorescent light 

switchin

I It I I I 

P. Chowdhuri 1 cycle B-0.5 300 500 1 cycle 

I I I I I I 

P.H. Bosvorth 2 cycles B-0.5 300 500 2 cycle 

R.L. Maul - 1 ps 1) Two few surges to show 

typical valw. I surgesl 500 

total I 

R.G. Hoft 

Probably al

storm. 

P.A. Fessler 

- 

Ellis 

Hosvital 

All during 

storm. 

-- - 

St. Clare's 

Hospital 

Barney's 

Dept. Store 

L & H Hotel 

1400 Il cycle I I 'bo few surges to show 

typical valw. I surges 700 

total 

500 lcycle B-0.5 300 500 lcycle 

I I 

Probably 

H.R. Sellers 0.2 100 oil burner. 

W.H. Bellamy 

W.J. Smiley 

J. R. Ross 

F.D. Martzloff 

P.A. Abetti 

D.G. Gruber 

K.H. Hoffmann 

Deer Park 

Palmetto 

#2 llG System 

480 volt 

feed svstem 

2000 1 1 1 same as most severe 

0.4 1 125 1 ail burner 

2000 1 1 1 same as most severe qTT!=

water pump 

0.06 1 500 1 oil burner 

I surges 150 House adjac

total to J.R. Ros

. surge Probably 

total lightning 

400 1 1 1 too few to show typical 

0.05 1 1500 I Rural area 

sur es 

Lightning 

stroke with

1000 feet. 

10 ps 10 )Is 200 4 cycles B-0.2 600 1000 cycle *

s stem 

.4 400 &cycle too few to show typical 

No surges above 300 volts were recorded at the 7 following locations: GE Bldg. 37, roof-top house, air conditioning 

bus, 440 volts bus. 550 volts bus; Hotel Van Curler; FE system #I; B. Murphy. 

qT: A - Long Oscillation; B - Damped Oscillation; C - Unidirectional - NUMBER SHOWS FREQUENCY IN MEGACYCLES 
TABLE fI 

SIMURY OF SURGE COWER RECORDINGS IN HOMES - DECEMBER 1964 to MARCH 1965 

Location Number Recording Number of 

(~pproximate) of homes Period Houses with Detailed Information 

surveyed (weeks) Surge Activity 

Providence. R.I. 4 2-6 None 

Cleveland, Ohio 

Lg. Lamp data 14 2 -4 1 1 surge over 1200 - community-wide power 

failure. 

Min. Lamp data 14 2 -4 None 

Auburn, N.Y. 12 2-3 None 

Lynchburg, Va. 3 2-3 None 

Syracuse, N.Y. 8 1-2 1 1200 to 2000V surge, 1 polarity only, 64 coun

in 10 days, probably refrigerator. 

Chicago, Ill. 23 1-6 None 

Ashland, Mass. 24 1-2 2 1 surge over 1200V in a 20 day period, no 

known system disturbance. 

6 surges over l2OOV in a 12 day period, no 

known system disturbance. 

Holland, Mich. 6 2-10 None 

Louisville, Ky. 10 2-6 1 1 surge over 1200V - lightning stroke which 

burned out TV set and UHF converter in the 

home. 

Somersworth, N.H. 

(and nearby N.B. h 50 1-2 

Maine locations) 

1 Surges between 1200 and 2000 volts, some 

probably close to 1200 as two counters at 

same location had difference in count. 

Counter slmultaneously installed in adjacent 

house did not record any surges. Most 

frequent count at night in cold weather; 

probable cause is oil burner. 

Plainville , Conn. 5 10 None DAD & CPDD data. 

--- 

Asheboro, N.C. 24 1-2 None 

Ft. Wayne, Ind. 

Spty. Transf. data 23 1-2 None 

Laboratory data 15 2-4 3 

* 

Location #1: Ballast side of switch control- 

(7 counts) ling a fluorescent lamp, no * surges on the line side. 

Location #2: Surges recorded in connection 

(5 counts) with operation of GE portable * mixer. 

Location #3: Surges recorded as fan motor 

(5 counts) plug is removed from same 

outlet as counter. * All between 1200 and 2000V 

None 

Pittsfield 26 1-2 1 One surge with no known system disturbance 
Ashboro, N. C. 

De Kalb, Ill. 

Somersworth, N.H. 

Chicago, Ill. 

Cleveland, Ohio 

Decatur, Ill. 

Cleveland, Ohio 

Holland, Mich. 

Auburn, N.Y. 

Springfield, Pa. 

Ashland, Mass. 

Pittsfield, Mass 

Plainsville, Conn. 

Lynchburg, Va. 

Total 

1 in Home 11.1 

1 in Home #2 

1 in 1 Home 

0 

1 in 1 Home 

1 in Home #l 

2 in Home %3 

0 

0 

0 

0 

0 

1 in 1 Home 

9 in 8 Homes 

Several storms in area. 

Violent storm. 

No known disturbance. 

Owner installed arrester 

after the first count. 

During power outage. 

During storm. 

During same storm. 

2000 volt counter at same 

outlet did not register 

(during storm) . 
2000 , 

1500 - 

1000 - 

500 - 

0 - 

Volts 

500 - 

1000 - 

1500 - 

1000- 

500- 

0- 

Volts 

500- 

1000- 

1500' 

3000- 

ZOO& 

1000- 

0- 

Volts 

1000- 

2000- 

3000 - 

Composite record showing 

surges for a 24-hour 

period. 

Oscilloscope is triggered 

for each surge, plus once 

every hour, resulting in 

- + 165 volt band of steady

state 60 cps voltage. 

Recordings above 1800V 

are blanked out by 

oscilloscope. 

I I 0 d 

0 8.5 18 31 5 3 1 do 

Microseconds 

Single surge occurring 

150 ps after initial, 

low amplitude surge 

triggered the oscilloscop

Maximum recorded surge, 

at 2600 volts. 

In a 5-day period surges 

this wave shape were 

recorded as follows: 

Number Voltage Range 

of surges 

1 2500 - 3000 

21 2000 - 2500 

18 1500 - 2000 

13 1000 - 1500 

Cause: H.V. transformer 

oil furnace interr

Fig. 1. Typical Surges Recorded at Stewart Manor, L. I., N. Y., 

February 16-21, 1963. 
Lightning surge at Deer Park 3.8 KEr crest, 1,Us rise time 

330 KC oscillation 

Lightning surge at Deer Park 5.6 KV crest, rise time ( IDS 

500 KC oscillation 

Fig. 2. Transients Recorded on Overhead Distribution Systems in 

Charleston, S. C, , July 1963. 
Switching transient with restrikes--probably external to the house. 

(The faint sine wave corresponds to the return of the electron beam which wa

not completely blanked out. It illustrates the peak-to-peak value of the 

steady state 117 voltage, but not at the same rate as the forward sweep.) 

Internal switching transient 

(15 such transients in 1500 hours) 

Fig. 3. Transients Recorded at a Farmhouse, August 1963. 

- 18 -
BIBLIOGRAPHY 

This bibliography was prepared by the author for IEEE Standard 587 - 1980, 

"IEEE Guide for Surge Voltages in Low-Voltage AC Power Circuits". It 

is reprinted with permission of The Institute of Electrical and Electronics 

Engineers, Inc., 345 East 47th Street, New York, New York 10017. 

Dl. Publications Describing the Environment 

[Dl] AIEE COMMITTEE REPORT. Switching 

Surges Due to De-Energization of Capacitive 

Circuits, AZEE Transactions, Aug 1957, pp 

562-564. 

[D2] ALLEN, G. W., and SEGALL, D. Monitoring Computer Installations for Power Line 

Disturbances, presented at the IEEE Power 

Engineering Society Winter Meeting, New 

York, NY, Jan 1974, Paper C74-199-6. 

[D3] BODLE, D. W., GHAZI, A. J., SYED, M., 

and WOODSIDE, R. L. Characterization of the 

Electrical Environment, Toronto and Buffalo, 

NY: University of Toronto Press, 1976. 

[D4] BULL, J. H. Impedance of the Supply 

blains at Radio Frequencies, Proceedings of the 

First Symposium on EMC, Montreux, May 

1975, 75CH1012-4 Mont. 

[D5] CHOWDHURI, P. Transient-Voltage Characteristics of Silicon Power Rectifiers, IEEE 

Transactions on Industry Applications, vol 

IA-9, Sept/Oct 1973, p 582. 

LUbJ CLANUS, N., and YlLKL'J!i, b. '1'. A 

Ground-Lightning Environment for Engineering Usage, Stanford Research Institute, Menlo 

Park, CA 94205, Aug 1972. 

[D7] Golde, R. H., Ed. Lightning, vols 1 and 2, 

New York: Academic Press, 1977. 

[DB] HASLER, R., &d LAGADEC, R. Digital 

Measurement of Fast Transients on Power 

Supply Lines, proceedings of the Third Symposium on EMC, Rotterdam, May 1979. 

[D9] JOHNSON, I. B. IEEE Tutorial Course: 

Surge Protection in Power Systems, IEEE 

Power Engineering Society, 79EH0144-6-PWR, 

1978. 

[Dl01 LENZ, J. E. Basic Impulse Insulation 

Levels of Mercury Lamp Ballast for Outdoor 

Applications, Illuminating Engineering, Feb 

1964, pp 133-140. 

[Dll] LERSTRUP, K. Atmospheric Overvoltages on Low-Voltage Installations, International 

Electrotechnical Commission, Doc IEC-28Al 

WG1, Feb 1976. 

[Dl21 MARTZLOFF, F. D. Coordination of 

Surge Protectors in Low-Voltage AC Power Circuits, presented at the IEEE Power Engineering 

Society Summer Meeting, 1979, Paper F 79 

635-4. 

[Dl31 MARTZLOFF, F. D. Protection contre 

les surtensions: Importance des nouvelles techniques. Proceedings, 1980 ZEEE Canadian Conference on Communications and Power, 

80CH1583, pp 267-270. 

[Dl41 MARTZLOFF, F. D., and CROUCH, 

K. E. Coordination de la protection contre les 

surtensions dam les reseaux base tension 

residentiels, Proceedings 1 978 ZEEE Canadian 

Conference on Communications and Power, 

78CH1373-0, pp 451-454. 

[Dl51 MARTZLOFF, F. D., and Hahn, G. J. 

Surge Voltage in Residential and Industrial 

Power Circuits, ZEEE Transactions on Power 

Apparatus and Systems, vol PAS-89, July1 

Aug 1970, pp 1049-1056. 

[Dl61 PLUMER, J. A., and CROUCH, K. E. 

Lightning Protection for Traffic Control Sys- IXT--L:-~--. nn --A D---A ..--. n~

Public Technology, 1978. 

D2. Publications Describing Test Methods 

[Dl71 CROUCH, K. E., FISHER, F. A., and 

MARTZLOFF, F. D. Transient Control Levels: 

A Better Way to Voltage Ratings in Power Converter Applications, Conference Record, IEEE 

Industry Applications Society, 11 th Annual 

Meeting, Chicago, IL, Oct 11-14, 1976, pp 

940-944. 

[Dl81 FISHER, F. A. and MARTZLOFF, F. D. 

Transient Control Levels, a Proposal for Insulation Coordination in Low-Voltage Systems, 

ZEEE Transactions on Power Apparatus and 

Systems, vol PAS-95, JanIFeb 1976, pp 120- 

129. 

[Dl91 LUTZ, M. Testing with Impulse Voltages 

and Impulse Currents in the Range of 0.5 to 75 

kV and 1 A to 30 kA, Haefely Application 

Note, 1979. (Available from American HV Test 

Systems, Central Garrett Industrial Park, Accident, MD 21520.) 
[D20] MARTZWFF, F. D. Transient Control 

Level Test Generators, Corporate Research and 

Development, General Electric Company, Schenectady, NY, 1977, Rep 77CRD241. 

[D21] MARTZLOFF, F. D. and FISHER, F. A. 

Transient Control Level Philosophy and Implementation: The Reasoning Behind the Philosophy, Proceedings 2nd Symposium on EMC, 

Montreux, June 1977,77CH1224-5EMC. 

ED221 MONDRUSAN, M. Long-Duration Impulse Current Generator for Arrester Tests 

According to IEC Recommendations, Bulletin 

SEV/VSE, ~0168,1977, pp 1304-1309. 

[D23] RICHMAN, P. Conductive Surge Testing 

of Circuits and Systems, presented at the FAANASA Symposium on Lightning Technology, 

Florida Institute of Technology, Apr 22-24, 

1980. 

[D24] RICHMAN, P. Diagnostic Surge Testing, 

pts I, 11, Power Conversion, Oct/Nov, 1979. 

[D25] TIMPERLEY, J. E. Construction and 

Application of a SWC Generator, presented at 

the IEEE Power Engineering Society Winter 

Meeting, New York, NY, Jan 1972, Paper 

C72-040-9. 

D3. Standards and Related Documents 

[D26] ANSI C62.2-1969, Guide for Appli

tion of Vdve Type Lightning Arresters 

Alternating Current Systems. 

ID271 ANSI/IEEE C37.90a-1974, Guide 

Surge Withstand Capability (SWC) Tests. 

[D28] ANSI/IEEE Std 28-1974, Standard 

Surge Arresters for AC Power Circuits. 

[D29] Code of Federal Regulations, Lon

tudinal Voltage Surge Test #3, sec 68.302(

title 37, Telecommunications. Washington, D

US Government Printing Office, 1977. 

[D30] IEC No 664 (1980), Insulation Coor

nation within Low-Voltage Systems Includ

Clearances and Creepage Distances for Equ

ment. 

ID311 IEEE Std 4-1978, Standard for Hi

Voltage Testing Techniques. 

[D32] IEEE Std 465.1-1977, Test Specifi

tions for Gas Tube Surge Protective Devices. 

[D33] Rural Electrification Administrat

(REA) Specification PE-60, Trunk Carr

Multiplex Equipment. Washington, DC 202

1975. 

ID341 UL943, Standard for Safety - Grou

Fault Circuit Interrupters, May 1976. 
WINNING

THE

REMATCH
Varistor versus Environment: Winning the Rematch

François Martzloff, Life Fellow, IEEE

National Institute of Standards and Technology

Gaithersburg MD 20899 USA

f.martzloff@ieee.org

© 1986 IEEE

Reprinted, with permission, from IEEE Transactions on Power Systems, Vol.PWRD No.3, April 1986

Significance:

This paper is listed under four categories of the Annotated Bibliography as it bears on the corresponding topics. 

The multiple listing reflects the sections in which this paper is cited as supporting material for IEEE Std C62.41.1

and C62.41.2. Therefore, it can be found in the following four parts of the Anthology:

Part 2 Development of standard – Reality checks

Provides an example of the need to recognize capacitor switching transients when characterizing the surge

environment

Part 3 Recorded occurrences, surveys and staged tests

Provides an example of monitoring and staged tests motivated by field failure, leading to a better understanding of

the environment in which SPDs were expected to perform.

Part 4 Propagation and coupling of surges

Provides an example of how far (3000 meters) the low-frequency transients generated by capacitor switching can

propagate, unabated, in a path involving two step-down transformers.

Part 7 Mitigation techniques

Provides an example of improved mitigation design based on field experience
VARISTOR VERSUS ENVIRONMENT: WINNING THE REMATCH 

Francois D. Martzloff, Fellow IEEE 

Corporate Research and Development 

General Electric Company 

Schenectady, New York 12345 

Abstract - An unusual case of difficult application of surge 

prntective devices was solved by field measurements with retrofit 

of protective devices suitable for the particular environment. Onsite measurements indicated that capacitor switching transients 

were causing excessive current surges in the varistors and fuses 

protecting the input to a thyristor motor drive. Knowledge of the 

environment gained by the measurements allowed understanding 

of the probieiti aiid sp&biioii of maiching siirge ijioi&i~a 

devices. 

SUMMARY 

During the initial startup of a solid-state motor drive in a -L--..:--l ..r.-.-ano:..n ..lnrt .4:ffin..ltiar r.r;th +ha .rar:ntnr --A ,,,*G,..,ra, p'vr&,D,,& p,u.,L, uu"ru,,,"* U.U*" ",.A. .SAW .n..*. ". "%I" 

its protective fuse at the input of the thyristor circuits. Frequent 

blowing of the fuse was observed, with occasional failure of the 

varistor. On-site measurements of the voltages and currents at the 

input to the drive indicated that switching transients associated 

with the operation of a remote substation capacitor bank and the 

relatively low clamping level of the varistor were producing current 

above the fuse and varistor ratings; hence the short lives of these 

two components. When the actual conditions at that site were 

determined by measurements, it became possible to specify surge 

protective devices capable of withstanding that environment. Immediate relief was secured by the installation of a larger varistor at 

the same point of the circuit; long-term protection was obtained by 

the addition of a gapless metal-oxide varistor arrester on the primary side of the step-down transformer feeding the drive. The 

situation has been changed from failures occurring every few days 

to no further problems in the 3 years since the larger varistor was 

insiaiied. 

INTRODUCTION 

This paper presents a case history illustrating how surge protective devices that are successfully applied for the majority of cases an ~ccasiana!!y snKe: fzi!u:e when ~YPOECC! to exceptio??~!!~ 

severe surge environments. This paper also shows how little 

attenuation occurs, at the frequencies produced by switching 

surges, between the distribution level (23 kV) and the utilization 

level (460 V), even though a long line and two step-down 

transformers exist between the source of the transient and the 

point of measurement. 

85 SM 365-2 A paper recommended and approved 

by the IEEE Surge Protective Devices Committee of 

the IEEE Power Engineering Society for presentation at the IEEE~PES 1985 Summer Meeting, Vancouver, 

B.C., Canada, July 14 - 19, 1985. Manuscript submitted February 1, 1985; made available for printing April 22, 1985. 

The problem involved a 460 V power supply to a 

drive circuit in a chemical processing plant extending ove

square miles. During the initial startup, difficulties arose 

varistor and its protective fuse at the input of the thyristor 

Frequent blowing of the fuse was observed, with occasion

of the varistor. The plant substation, fed at 23 kV from 

utility, included a large capacitor bank with one-third of 

"...:+"l.c\* -.. nr.4 .-.a- *A ...,...:A- ..,...,&.. Fnr+,.. ne.4 ".rota- 

anlrnlru uu uzau ULL rv pvrnur yvnrn larrur auu ojururl

regulation. These frequent switching operations were susp

generating high-energy transients that might be the caus

failure of the fuses and varistors, because literally thou

similar drive systems have been installed in other 

without this difficulty. On-site measurements perform

repeated blowing of fuses and occasional failure of varist

nected at the input to the thyristor drive indicated that in

devices were not matched to their environment. From t

on, specifying larger sizes, sizes appropriate to the envi

[ll, solved the problem. 

POWER SYSTEM AND SWITCHING TRANSIEN

Figure 1 is a simplified one-line diagram of the s

elements of the power system causing the varistor failu

incoming 115 kV power is stepped down to 23 kV. Thr

of 5400 kVAR capacitors are connected to the 23 kV bus

operating conditions involve two banks connected at a

with the third bank switched on or off automatically to 

voltage regulation. Power distribution throughout the sit

at the 23 kV level. 

The various drive systems which experienced the diff

supplied at 460 V by a 2300/460 V transformer in thei

house. A substation close to the control house sup

2300 V power from the 23 kV distribution system. 

SiTE 

SUBSTATION DISTRIBUTION SYSTEM HOUSE i cONTROL 

I 

CON

CU

VARISTORS 

0885-89/77/86/0004-0059$01.00@1986 IEEE 
Figure 2 is a simplified three-phase schematic of the power 

input. In the original circuit. the thyristor modules were protected 

by varistors at the power input of the 1250 hp drive, where the 

measurements were made. A 6 line inductance, L1, was 

inserted between the bus and the thyristor modules; 20 mm 

varistors rated 510 V were connected in a delta configuration, in 

series with a current-limiting fuse in each line. The varistor confieciioii via3 about 80 ciii loag, in:iodi;cing an e3tima:ed ! jiH 

inductance into each lead. 

TO CRO 

IIW I+&=&== THYRISTOR 

MOD",. 

u 

[ IDENTICAL CIRCUIT TO THYRISTOR MODULE 

Figure 2. Simplified three-phase schematic 

Instrumentation and Measurements 

Oscilloscopes were used to measure voltage across one varistor 

and its connection and currents through all varistors. Voltage 

measurements were made phase-to-phase on the floating delta 

460 V bus bars with Tektronix P6015 1000:l probes, connected to 

a Tektronix 7633 storage oscilloscope in differentia mode. Current measurements were made with a Tektronix CT5 20:l current 

transformer coupled with a P6021 current probe and connected to 

a second Tektronix 7633 storage oscilloscope. 

The trigger modes used during a two-hour monitoring period 

inciuaed posiiive or negaiive siopes for both siow ac and highfrequency modes. For the various modes, the level was adjusted 

to produce a trigger for a voltage exceeding the normal line voltage crest by about 20°/0, or a varistor current in excess of 2 A. No 

trigger occurred during the monitoring period. A low-frequency 

voltage recorder installed by plant personnel produced a recording 

characterized as representative of an unusually quiet day in the 

power system operations. 

Manual off-on switching of the 5400 kVAR capacitor bank at 

the 23 kV utility substation was the next step in the measurement 

procedures because the switching of a capacitor bank is always a 

prime suspect for producing transients. Measurements were performed with one oscilloscope monitoring the line voltage upstream 

of the line inductors (Figure 2) and another oscilloscope monitoring the sum of the currents in the three varistors (Figure 3). 

Figure 3. CT connection for recording 

all three varistor currents 

Results 

-. 1ne osciiiogiams of Figure 4 show typicai voitage recor

made during this sequence. The voltages are not open-circuit 

sient voltages. They are instances of the voltage appearing a

bus entrance point. This voltage is the sum of the varistor c

ing voltage, the voltage drop in the varistor connections, an

voltage across two L1 inductances. 

A typical total event recorded on one of the phases dur

capacitor bank closing is shown in Figure 4A. A low-frequ

oscillation with a period of 3 ms (330 Hz) and initial peak-to

amplitude of 450 V decayed in about 10 ms. The high-frequ

oscillations are resolved in the recording of Figure 4R (rec

during a similar switching sequence). This high frequency h

initial peak-to-peak amplitude of 2000 V, decaying in about 

The period is 180 ks (5.5 kHz). A similar, third event is sho

Figure 4C. For scaling the amplitudes, the steady-state volta

shown in Figure 4D. 

A Sweep: 2 ms/div Vertlcal: 500 Vfdlr 

B Sweep: 0.5 msldlv 

Vert1c.l: 500 Vldiv 

C Sweep: 1 msldlv 

Vertlcal: 500 Vldlv 

D Sweep: 2 maldlv 

Vcrticd: 500 VIUv 

Figure 4. Capacitor switching transients 

and steady-state voltage 

Observe that, depending on the time of clos~ng with respe

the 60 Hz voltage, the 5.5 kHz oscillation varies in ampli

f,lrtherrr?ore, !he modc!atic)n by the 330 Hz osc!!!ntlcn pc

crests of the 5.5 kHz oscillation above the 1000 V level some 

after the beginning of the trace, at a time when the 5.5 kHz a

tude is already lower, producing a burst of pulses above 

1000 V level. 

The significance of this finding will be discussed next; 

reference to Figure 5, which shows recordings of transient 

rents in all of the three varistors. The 510 V varistor has a n

nal voltage at 1 mA [21 in the range of 735 V to 970 V. F

varistor with a nominal voltage in the middle of this range, a 

rent in the order of tens to hundreds of amperes will flow 

..-B.~-- ,.r jnnn TT :- ---$:-A vwrrat;E; wi lwww r 13 app~lcu io ih2 iiiiii~i~i. Figure 5A sho

train of current pulses in the range of 10 to 40 A. In the bu

Figure 5B, the recorded current pulses range from 5 A to 2

The current and voltage traces are not simultaneous e

because each of the two oscilloscopes was triggered by its int

circuit. The nearly symmetrical appearance of this burst ca

compared to the symmetry of the voltage peaks exceeding 

1000 V level in Figure 4, the one correlating with the other. 

The oscillograms of Figures 4 and 5 were selected as 

severe from a series of 20 capacitor switching sequences. 

sequences could not even produce a current or voltage tr

tour sequences produced bursts w~th the central peak exce

120 A, two of these reaching 200 A peaks. 
A Sweep: 0.2 ms/di, 

Vertical: 20 A/dlv 

I3 Sweep: 8.5 msldlv 

Vertlcsl: 40 A/div 

Figure 5. Current surge bursts during capacitor switching 

These recordings establish the nature of the current surges that 

are conducted by the varistors, with an estimate of 10% reaching 

200 A maxlmum crests and another 10% reachmg 120 A crests, ,-A- ..,, -----:*..- L..-,. :'-L:-- IUI a11 bapabnul uaun SWILLIIIII~. 

In F~gures 4 and 5, we note that the characteristic appearance 

of the voltage and current usually observed during a switch 

restrike is absent 131, indicating a clean switching action of the 

vacuum interrupters used for switching the capacitor bank. Restrikes are most likely to occur during de-energizing. In all the offon switching sequences of this test series, no significant transient 

was observed during de-energizing; all occurred during energizing. 

The oscillograms of Figures 4 and 5 establish and explain the 

pattern of current pulses. The voltages of Figure 4 are not the 

open-circuit voltages impinging the drive input but, rather, the 

voltages resulting from the clamping action of the varistors. To 

better evaluate the magnitude of the switching transients, opencircuit voltages were recorded in a next sequence, with all fuses to 

the drive open, thus disconnecting both the varistors and all sensitive loads. Figure 6 shows two typical recordings of open-circuit 

voltages and two of voltages resulting from varistor clamping, 

recorded during a series of 10 switching sequences for each condition. Tabie i shows the recorded crests of the five highest voitages in each condition; the di!Te:ence bekeen the :wo gioiips, 

with due allowance for the imperfect statistical basis of the observations, indicates that the 510 V varistors reduced the peaks from 

a typical high of 1450 V to a typical high of 1100 V. 

Open-Circuit Voltsges 

With 20 mm Varistors 

All Traces: Sweep: 0.5 nts/div 

Vertical: 500 Vldiv 

Table 1 

FIVE HIGHEST TRANSIENTS 

IN SEQUENCE OF 10 SWITCHINGS 

Without Varistors I With Varistors I 

DISCUSSION 

Nature of the Transients 

The absence of any transient (over 120% of norm

during ihe 2-hour moniroring period was somewhat surp

!he cestex! ef ear!ier repc:!s cf high ccun% :cc~ibed wi:h 

disturbance analyzers. Frequent checks of threshold l

variations of the possible trigger modes were made, m

the chance of catching an overvoltage, but indeed none 

This unusual quiet was also reflected in the chart record

by the plant personnel, so that the absence of random 

for that period can be accepted at face value. 

Therefore, conclusive evidence was obtained that s

current pulses were absorbed by the varistors during 

switching. The magnitude and duration of these pu

excessive for the capability of a 20 mm disc; many simi

installed elsewhere do not experience the failures encou

that particular location. 

Another significant finding from these measuremen

fact that the switching transients, generated at the 23 

propagate down to the point of utilization at the 460 

Numerical discussion of this finding is given later in this p

Effect of Transients on Varistors 

Published varistor ~cifimtions inr!u& the "p&e r

family of curves that define, for each varistor type, the n

isolated pulses that a varistor can absorb until its "r

reached i4i. The curves show lines relating amplitude, 

and total number of pulses. Figure 7 shows this family 

for the original 20 mm varistor. 

Figure 8 shows the same curves for a proposed 32 m

tor. It should be noted that the pulse rating does not m

strophic failure of the varistor at the end of this rating, b

10% change in the varistor nominal voltage. Althou

change is indicated, the varistor is quite capable of stayin

voltage and of clamping surges. 

Figure 6. Capacitor switching transients 

lYCULSE 0UI)ATION - u 

Figure 7. Pulse ratings of 20 mm varistor 141 
Figure 8. Pulse ratings of 32 mm varistor 151 

A careful examination of the pulse rating curves will show that 

the duration of the pulses has a strong influence on the number of 

permissible pulses. Furthermore, the relationship between the 

increased duration of the pulses and the decreased number of permissible pulses is not proportional. For instance, consider pulses 

of 106 A peak eiid 100 CLs (juia~oii (FigGFe 9A): the ci;rves 

5000 pulses allowed. Now increase the duration of the pulses to 

1000 ps (a ten-fold increase), while keeping the amplitude at 

100 A: the curves show the permissible number as one pulse 

only. Thus, the ten-fold increase in duration does not result in a 

ten-fold decrease in the number of permissible pulses; the reduction in that number is much greater than the inverse of the 

increase in duration. Conversely, taking a pulse duration of 

1000 ps, and seeking the amplitude allowable for the same 5000 

pulses, Figure 9B shows that the current is 20 A, which is five 

times less than the original 100 A, not ten times less. Therefore, 

it wou!d be incorrect to treat the multiple pulses of Figure 5 as 

five separate short pulses; rather, one equivalent long pulse has to 

be defined. 

The five-pulse burst of Figure 5 has been redrawn in Figure 10 

in order to plot an equivalent continuous pulse of approximately 

equal duration, with a crest such that the i.t integral of the burst 

and the i.t of the equivalent pulse are approximately the same. 

The use of i.t rather than the i2.t integral typically used for fuses or 

other linear loads is justified by the fact that heat deposited in the 

varistors is the significant parameter because the nominal voltage 

change process is temperature related; this heat is the product of - --A 4 r-n- .. --notnnt .,nltona nrrnae the nnnlin~nr rrle valrawr; i auu rile I,ral!j curlarsur vvarvbv ar~vuu UA~ I.vl.....rr. 

varistor during the burst. 

The equivalent pulse of Figure 10 can then be used to evaluate, from the pulse ratings of Figure 7, the number of highamplitude switching transients that will consume 100% of the 

vzris!~r pu!se ra!ing. !nspec!ior? of Figure 6 shows that for a 

800 ps duration and 100 A amplitude, the pulse rating of the 

20 rnm varistor (6 kA rating at 8/20 ps) is reached with two such 

events. With a probability of about 10% that this highest switching 

transient would occur during random timing of the switching (the 

effect decreases rapidly for transients other than the highest) and 

with 2 to 4 swirching operaiions each day, iht piiise iaiiiig of the 

varistors could be reached with 20 operations, failure perhaps 

starting at 40 to 50 operations, or after about 10 days of exposure 

to that power system environment. This estimate is unavoidably 

imprecise because the pulse rating curves represent a conservative 

minimum; actual failures will occur only for amplitudes or numbers of pulses exceeding the rating by a large but imprecise margin 

to allow for manufacturing variations. However, the order of 

magnitude of this estimated time to failure is in accord with the 

observations made at that installation. 

IMPULSE DURATION-us 

A. Same current, increasing duration 

20 1% I0 MX

IMPULSE DURATION-@n 

B. Same number of pulses, increasing duration 

Figure 9. Reading pulse ratings curves 

/L/ ACTUAL 

Figure 10. Single-pulse equivalent pulse for multiple pu

Note that two types of events occur. One is the prem

blowing of the fuse, which is not caused by a varistor iaiiu

by the i2.t capacity of the fuse being exceeded by the enviro

[I]. The other is the fuse blowing caused by the varistor e

life ultimate failure. 
An obvious remedy would be to use a varistor with greater 

energy-handling capability. The 32 mm size offers such a possibility. Inspection of Figures 7 and 8 shows that the equivalent 

pulse of Figure 10 (800 ps and 100 A) corresponds to a permissible occurrence of 100 pulses for the 32 mm varistor, in contrast to 

the two for the 20 mm varistor. The improvement in the number 

of pulses is 50 times more pulses until pulse rating is reached. The 

improvement in the number of pulses until varistor failure occurs, 

however, is not necessarily 50 times more pulses. Because of the 

imprecision mentioned previously in the margin between end of 

pulse rating and ultimate failure, that margin is not necessarily the 

same for the two sizes, 20 mm and 32 mm, but it is reasonable to 

expect the same order of magnitude improvement in the ultimate 

failure as in the pulse rating. This expectation of a 50 times 

improvement would change !he time be!ween fel!ures fro.?? the 

few days observed with the 20 mm size to perhaps one year with 

the 32 mm size, providing immediate relief and time to make fur- -. ther changes for the iong term. 'l'herefore, the change to a 32 mm 

size, cannec:eb a; :he saiiie of the circiiit, was immadiaieiy 

implemented for that particular environment. 

Further gains could be obtained in the length of time between 

varistor failures by increasing the clamping voltage of the varistors. 

This increase would result in lower current pulses for the same 

open-circuit transient voltage. A 510 V rating had been selected 

by the designer of the drive as the result of a trade-off between 

varistor clamping voltage and the withstand voltage of the thyristors protected by the varistors. If thyristors with higher voltage 

withstand were used, the solution would be easy. 

Of course, the standard varistor product line has a certain tolerance band, reflecting normal production lot variations. In principle, a selection could be requested from the manufacturer that 

varistors with a narrower band be supplied for this application. 

The maximum clamping voltage allowed by the drive specifications 

would be retained, but those varistors in the lower half of the distribution, which draw larger current pulses for a given open-circuit 

transient voltage, would have been removed from the population 

01" varistors. For instance, the range of nominal voltages for a 

575 V, 32 m.r. ua:iatc: (the next higher vokage ofTered1 is 805 to 

1005 V for 1 mA dc, while the maximum nominal vo!tage of the 

same diameter but rated 510 V is 910 V for 1 mA dc. Thus, for a 

normal distribution of nominal voltages of the 575 V varistor, 50% 

of the devices could theoretically be used without exceeding the 

upper limit of the 510 V varistor that is consistent with the drive 

specifications. To achieve this end, it would be necessary for the 

supplier or user to make a careful determination of the nominal 

voltage on a population of 575 V varistors in order to retain only 

the lower half of the distribution (Figure 11). 

ACCEPTABLE LEVEL FOR THYRISTORS I 

SPECIFIED BY DRIVE DESIGNER 

PRESENT USE 

RANGE OF NOMINAL 

VOLTAGES FOR 510 V 

- - VOLTAGES FOR 575 V 805 1 1005 I 

Figure 11. Tolerances bands of 510 V 

and 575 V varistors 

In addition to the proposed upgrading of prote

460 V level, three other remedies could be consider

tion of surge arresters at the 2300 V level, installat

arresters at the 23 kV level, or a change in the circuit

the capacitor switching, designed to reduce the sev

transients at their origin. 

In general, the protection available from surge ar

to improve when the arresters are installed at higher 

ages. Thus, it is quite possible that arresters ins

2300 V primary of the 23001460 transformer could pr

effective clamping (and at the same time relieve 

energy stress) than the varistors at the 460 V leve

course implied that these would be the zinc-oxide 

arresters.) The full benefit of these arresters dep

configuration of the 2300 V system and its ground

grounded iieiiirai in a wye sysiem, resistance-groun

Boating de!?a! when the arresters "re mnnected i~ 

tional line-to-ground mode. In a second phase of 

described here, 2300 V arresters were installed at the 

primary. A discussion of their expected performance, 

the success of the retrofit, is given later on. 

Likewise, arresters on the 23 kV side could be in

23 kV substation to mitigate the capacitor switching 

their origin, or at the primary of the 23 kVl2300 V su

the control house, where they would also serve 

protection for the overhead 23 kV incoming power 

arresters, again, must be of the gapless type to obta

effective protection. 

The final remedy in the list of alternatives, but per

in effectiveness when the opportunity exists, would b

reducing the severity of the capacitor switching trans

origin. Series inductors or damping resistors may be 

the effectiveness of which would be predictable if a s

the power system behavior were performed by comp

..," 'Wk:l- +h,,+ ----A.. -,... IA --' k6. ,. Lll'LL ,GI.IGUJ wuu HUL be appiied io this pm

tion: it is a remedy that should be cnnsiderac! for n si

exceptionally severe environment. 

The measurements made first with open-circuit, t

20 mm, 510 V varistors on the 460 V side have show

of maximum voltage from 1450 V to 1100 V (Tabl

current of approximately 200 A is flowing in the line 

(Figure 5). 

We can assume that the voltage drop in the line fr

tation and two step-down transformers is mostly 

5.5 kHz, and that the voltage in the varistors can be t

voltage across a resistor at the time of the crest of 

wave. The diagram of Figure 12 shows the relation

the three voltages VoC, VL, and VV, respectively, the 

voltage generated by the capacitor switching action, 

drop in the line and two transformers, and the varist

the current peak. Treating this highly nonlinear circu

circuit is an apprnrimation !ha! wi!! prnvide P! each 

full range of voltage and current conditions a valid ord

tude for the purposes of this discussion. Numerical 

avaiibie for rigorous treatment at any instant over t

of coiidi:ioii~ :6!. With iht shpil'ying assumpiion, w

mine the order of magnitude of the 5.5 kHz curren

flow in an arrester installed at the primary terminals 

Vl460 V transformer as follows. 

REFERENCES 

[I] F.D. Martzloff, "Matching Surge Protective Devices to their 

Environment," Proc. IEEE/IAS Meeting. October 1983, pp. 

387-392. (Also scheduled for IAS Transactions, Jan/Feb 

1985.) 

Committee. He is chairman of the Working Group on Surge C

zation in Low-Voltage Circuits. He is also a member of the 

Advisory Subcommittee of the USA Advisory Committee on 

28A, ANSI C.62 Subcommittee on Low-Voltage Surge 

Devices, and Chairman of the NEMA Low-Voltage Arresters 

Committee. He has been awarded 13 U.S. patents, primarily i

of varistors and transient protection. 
Discussion 

J. L. Koepfinger (Duquesne Light Company, Pittsburgh, PA): The author 

has addressed one of many mechanisms for producing repetitive overvoltages on low-voltage circuits. In this particular instance, it was possible 

to obtain controlled conditions so that a measurement could be made 

of the voltage and currents resulting from the capacitor switching. It 

would be useful if there was an analytical method presented that cor- related the generation of the 5.5-kHz pulses with those measured. Did 

the author attempt to make such a correlation? 

This paper points out the need to know the characteristic of the surge so that proper sizing of the protection can be achieved. Therefore it would 

be desirable to be able to have some analytical tool to permit calculation of the frequency of the surge due to remote capacitor switching. 

Manuscript received July 24, 1985. 

Frnncois D. Martzloff: The paper reported a case history from which 

usefui informaiion may be derived on reirofiiiina - corrections of simiiar 

pmb!ems or, he??er, on .voiding ?he pmh!em hy foresight. The d?lntions confronting the author was the need for immediate corrective action rather than complete investigation and mutual validation of analytical 

methods ad fieid measureiiieiits. 

The literature is fairly rich in both theoretical and practical papers on 

the problems associated with capacitor switching, both for energizing 

and for de-eneraizina. the latter involving the risk of restrikes. Because 

of this availabi<ty Gd the limited space available in the TRANSACTXONS on one hand. and because of the limitations in scoDe of the field retrofit 

mission on ihe other hand, no attempt was made to correlate the 

measurements with the power system parameters (which were not readily available to the author). In response to Mr. Koepfinger's suggestion, 

abstracts are cited below to provide references to both analytical tools 

and practical results published by other workers. 

Bibliography, 1970-1985 : REFERENCES 

[I] M. F. McGranaghan, W. E. Reid, S. W. Law, and D. W. Gresham, 

"Overvoltage Protection of Shunt-Capacitor Banks Using MOV Arresters," IEEE Trans. Power App. Syst., PAS-103, No. 8, Aug. 1984, 

vv. 2326-2333. - - 

Protection requirements and surge arrester duties are analyzed for 

both diairai - and iransieni neiwurk arlaiy~er -.. ~'Tiu'Aj suiiuiaiioas. Suiip!c &n~n_a!pirA expressions =e developed for evaluating arrester duty 

as a function of capacitor bank size. Guidelines and limitations for 

applying arresters at grounded- and ungrounded-wye capacitor banks ae based oil overvokEge c~larac~er;spics &-ies;er 

capabilities. 

[2] J. H. Brunke and G. G. Schoeckelt "Synchronous Energization of 

Shunt Capacitors at 230 kV," IEEE PES (Power Eng. Soc.) Winter 

Meeting, New York, NY; Jan. 20-Feb. 3, 1978; Publ. by IEEE 1977, 

Paper A78-148-9, p. 4. 

This paper reports on the application of synchronous switching 

to reduce inrush transients when switching a 230-kV shunt capacitor 

bank. Computer studies determined the required switch perfokce. 

[3] J. D. Cuffman, John Linders, M. A. Zucker, and S. Willima , "Power Factor Correction Capacitors and Their Side Effects," IEEE 

Conf. Rec., 28th Ann. Conf. Electr. Ens. Probl. Rubber Plast. Ind., 

Akron, OH, April 5-6, 1976, pp. 37-49. 

The major reason for applying capacitors to an electrical distribution system is to correct poor power factor. In the greater majority 

of installtions it is a routine procedure. In some instances capacitors 

may cause problems with other in-plant equipment and in other instances they may suffer undesirable side effects that originate in other 

equipment. Among these problems are switching surges, voltage unbaiance due to fuses biowiiig, and iimiionics geiiergted by SCRcnn?m!!cd en,r?ipmen?= 

[4] H. J. Yelland, and C. P. Yellna, "Vacuum Contactors: Latest 

Development in Their Design and Application," Certif. Ens. V 54, 

No. 1. Jan. 1981, pp. 824-841. 

The paper includes the following topics: Design of vacuum bottles (glass and ceramic); design of the complete vacuum contactor 

and their panels; panels with on-load isolation, and panels with offload isolation vacuum contactor applications (motor 

capacitor switching, arc and other (furnace-switching, tran

switching, mine-winder-reversers). Surge generation by vacu

tactors is considered under the following heads: basic ene

and de-energization transients; transients generated when s

inductive loads; assessment of a vacuum contactor from 

generation point of view; types of surge suppression devic

ching of capacitive loads. An extensive discussion of the 

appended. 

[5] Jack R. Harbaugh and John E. Harder, "Important Consid

for Capacitor Applications in the Petroleum and Chemical 

Industries," IEEE Pet. Chem. Ind. Conf., 27th Ann. Rec. 

Pap., Houston, TX, Sept. 8-10, 1980; IEEE, #80CH154

Piscataway. NJ, pp. 157-167. 

The location of capacitors may have a significant effec

(I**2R losses within the plant transformers and conductor

is wasted energy. Transients generated by capacitor switch

require attention in the selection of arresters, system insul

ofier equipment. ofcap&iors artly require som 

attentinn to !&rge motors during system r=!&ng or t

This study addresses each of these considerations, providi

guidelines for effective, reliable capacitor application. In a

a c:l&iisi is provided for indiisirid capaciior app&

[6] J. F. Burser, R. J. Santoro, J. W. Stolle. R. E. Owen an

Clinkenbeard, "Comparative Evaluation of Field Test D

Computer Results on Capacitor Switching Transients." 

Minutes PA Electr. Assoc., Eng. Sect., Trans. and Distrb. 

West Middlesec, PA, May 15-16,1979; PAElectr. Assoc., En

Harrisburg, PA 1979. 

An arrester failure case was analyzed occurring at the 

substation capacitor bank switching with the use of a trans

work analyzer (TNA) and digital computer techniques. The 

volved a 12.5-kV ground-wye distribution sytem. Results of t

study, which were validated by field tests, showed the effects o

configuration magnitude of transient over voltages. 

[7] Eldon J. Rosers, and Don A. Gilles, "Shunt Capacitor S

EM1 Voltages, Their Reduction in Bonneville Power Admin

Substations," IEEE Trans. Power Appar. Syst. PAS-93, 

Nov.-Dec. 1974, pp. 1849-1860. 

Back-to-back switching of grounded wye shunt capacito

high frequency, high-magnitude current flow in overhead 

___..->___. .,___._____PI_>..__> ___l.____ 

~~UUIIU ma~ GUIIUUSLU~S. IVLS~SU~CIIICIILS UL IIIUUSCU vui~agc

trol cables and receptacles; transverse voltages on fuse bl

secondaries and personnel intercept voltages are reporte

methods of confining transients to capacitor areas and s

*--I.-: --..:-.*."a LGcIlluqusJ as Isvlswsu. 

[8] Paul C. Krause and William C. Mauser, "On-Line Transie

trol of Capacitor Switching to Improve System Stability,

Trans. Power Appar. Syst. PAS-92, No. 1, Jan-Feb. 1

321-329. 

A simplified voltage-reactance equivalent of the one-mac

fhte bus system was used. The material presented in this pap

that this simplified model does not predict the performance o

machine infinite bus system with the accuracy necessary to d

the capacitor switching times so as to achieve the control ob

However, it is shown that computation accuracy may be im

by including system losses. It appears that in order to apply 

control techniques it will be necessary to develop more 

models of the power system components. Also, faster than r

iterative, on-line computation techniques as simulated in th

should be implemented and used to calculate the switchin

Until these obstacles are overcome, optimal control theory w

little impact upon the power industry. 

[9] D. 0. Wiitanen, J. D. Morgan, and G. L. Gaibrois, 

Tr -_-- :I-- "...1.-LI-- IF..--^:^-*^ 1- -,..I-, --A r?..-^-

uqxutul JWILSIIIII~ I I iulwslrLa, fulayrrcal 611u ~A~C

Results;" IEEE Trans. PowerApp. Syst. PAS-90, No. 4; Ju

1971, pp. 1639-1645. 

Station capacitor bank energization transients predicted 

cuit model are compared to field-test results. Selection of a 

model is discussed. A computer solution of the model is pr

Manuscript received September 19, 1985. 
ON

FAILURE

RATES

OF

CLOCK

MOTORS
Excerpt of a 1964 declassified General Electric memorandum discussing failure of clock motors

Significance:

Part 3 Recorded occurrences

The memorandum from which this excerpt is drawn was provided to Martzloff in support of his

contribution to gathering data on the occurrence of surges in low-voltage ac power systems, for a 

just-launched IEEE project on the emerging concerns about surge occurrences. 

These statistics provide convincing evidence, based on a large number of reported failures, that a

correlation exists between the rate of failures and the surge withstand capability of the motor windings. 

A design change in this withstand level, from 2 kV to 6 kV produced a 100:1 drop in the failure rate. 

Interestingly, this 100:1 ratio, when plotted on a chart in which data from other sources were entered,

produced a slope in good agreement with these other sources. Thus, the large number of clocks,

operating 24/7/365 and unwittingly serving as sacrificial “surge counters” boosted confidence that the

limited observations (in duration and in locations) being reported by other researchers were consistent.

Of course, the present-day significance of surge voltages is affected by the proliferation of surgeprotective devices, but these data are still useful as an indication of the occurrence of surges, only the

levels have changed but presumably the mechanisms are still in action.
.