ppy, , , yg

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 pdf

file “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).

Filename: Res&Ind surges
Surge Voltages in Residential and Industrial 

Power Circuits 

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 Protective 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 prmting 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. In the second phase of testing, 100 s
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 

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

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

reso!ution, 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 advancc 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 33gmm frame the trace displayed on the 

CRT. Following the sweep, the contact mentioned above closes 

the motor circuit, advltncing 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 builbin 

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 canlera 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 number 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 sati5factory 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 typical final path for a surge impinging upo

appliance connected to this particular wall receptacle

provides power for the high-impedance rectifier circuit 

signal input to the trigger-sensor circuit. 

A crudely coml~~ated 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 

1s. 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 FIAT TOP PULSE , micm*bconbs 

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 50-lrF capacitor. The resistance of this divider represents a 

negligible load for the house wiring system, yet is sufficiently 

low to allow some hakage 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 

tr- I COUNT REGISTERE0 

Fig. 5. ltecording with single-polarity counter. 

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 s

(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

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

*170-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. 

Cleveland, Ohio 

Auburn, N. Y. 

Lynchburg, Va. 

Syracuse, N. Y. 

Chicago, Ill. 

Ashland, Mass. 

Holland, Mich. 

Louisville, Ky. 

Somersworth, N. H. 

Plainville, Conn. 

Asheboro, N. C. 

Fort Wayne, Ind. 

DeKalb, 111. 

none 

none 

none 

none 

1 

none 

1 

none 

none 

1 

none 

none 

3 

nme 

TABLE I11 

SURGE COUNTER ECORDINGS 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. 

DeKalb, 111. 

Somersworth, N. 

Chicago, 111. 

Cleveland, Ohio 

Decatur, 111. 

Holland, Mich. 

Auburn, N. Y. 

Springfield, Pa. 

Ashland, Mass. 

Pittsfield, Mass. 

Plainville. Conn. 

~~nchbuk, Va. 

Total 

none 

2 

1 

none 

1 

2 

none 

none 

none 

none 

1 

none 

- 

none 

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 oscillosc

measurements, the surge counters were applied in two sepa

programs. First, during the winter months, the counters w

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, e

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

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

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'OWEK 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. 

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 

the 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 

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]-151. 

polarity surges above 1200 volts which do not also resu

positive surges above 120 volts. This multiplying fact

prohably about 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 probability 

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 ease, for example, probab

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. 
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.