Power Quality Site Surveys: 

Facts, Fiction, and Fallacies 

Abstract-The quality of the power supplied to sensitive electronic 

equipment is an imporlant issue. Monitoring disturbances of the power 

supply has been the objective of various site surveys, but results often 

appear to be instrument-dependent or site-dependent, making comparisons difficult. After a review of the origins and types of disturbances, the 

types of monitoring instruments are described. A summary of nine 

published surveys reported in the last 20 years is presented, and a close 

examination of underlying assumptions allows meaningful comparisons 

which can reconcile some of the differences. Finally, the paper makes an 

appeal for improved definitions and applications in the use of monitoring 

instruments. 

S ITE surveys are generally initiated to evaluate the quality 

of the power available at a specific location with the aim of 

avoiding equipment disturbances in a planned installation or of 

explaining (and correcting) disturbances in an existing installation. In either case, survey results constitute one of the inputs 

in the decision-making process of providing supplementary 

line conditioning equipment, either before or after disturbances have become a problem. Depending on the reliability 

requirements of the load equipment, its susceptibility, and the 

severity of the disturbances, various line conditioning methods 

have been proposed: surge suppressor (with or without filter), 

isolating transformer, voltage regulator, magnetic synthesizer, 

motor-generator set, or uninterruptible power supply (UPS). 

Because this additional line conditioning equipment may 

require significant capital investment, the choice of corrective 

measures is generally made by economic trade-off which is the 

prerogative and responsibility of the end user. However, if 

technical inputs to this trade-off are incorrect because erroneous conclusions were drawn as a result of a faulty site survey, 

the whole process is worthless, or worse yet, misleading. 

For this reason, a good understanding of the merits and 

limitations of site surveys is essential for reconciling expectation with reality before expensive line conditioning equipment 

is called for; one should deal, not with fiction or fallacies, but 

with facts. 

Power disturbances that affect sensitive electronic loads 

Paper ICPSD 87-05, approved by the Industrial and Commercial Power 

Systems Department of the IEEE Industry Applications Society for presentation at the 1987 Industrial and Commercial Power Systems Department 

Technical Conference, Nashville, TN, May 2-7. Manuscript released for 

publication March 2, 1988 

F. D. Martzloff is with the National Institute of Standards and Technology, 

Gaithersburg, MD 20899. 

T. M. Gmzs is with the Liebert Corporation, 1050 Dearborn Drive, 

Columbus, OH 43229. 

IEEE Log Number 8822938. 

have a variety of sources. Lightning, utility switching, and 

utility outages are often-cited sources of power disturbances. 

However, power disturbances are often caused by users 

themselves, through switching of loads, ground faults, or 

normal operation of equipment. Computer systems, as one 

example of these so-called sensitive loads, are not only 

sensitive loads but also can generate some disturbances 

themselves. Their nonlinear load characteristics can cause 

interactions with the power system such as unusual voltage 

drops, overloaded neutral conductors, or distortion of the line 

voltage. 

Utility systems are designed to provide reliable bulk power. 

However, it is not feasible for them to provide continuous 

power of the quality required for a completely undisturbed 

computer operation. Because normal use of electricity generates disturbances and because unexpected power system 

failures will occur, every site will experience some power 

disturbances. The nature of these power disturbances, their 

severity, and their incidence rates will vary from site to site. 

To place the problem in perspective, however, one should 

keep in mind that poor-quality power is only one of the many 

causes of computer downtime. Hardware problems, software 

problems, and operator errors also contribute to computer 

downtime. 

Sometimes there is too great a tendency to attribute 

operational difficulties to power supply problems. For example, studying power-related computer problems at U.S. Navy 

installations, Key [I] found that only 5-10 percent of the 

observed computer downtime was attributable to power 

problems. Reviewing case histories, Martzloff [2] described a 

safety problem created by panic actions of the computer 

system operators who pulled out power cords of the remote 

terminals (including the safety grounding conductor) because 

they suspected power line surges when, in fact, the problem 

was incorrect grounding practices for the shields of the data 

lines. 

Historically, transient overvoltage effects on novel semiconductor systems were the first concern; by now, the 

importance of undervoltages or loss of power has also been 

recognized. In the nine surveys reviewed in this paper, four 

address all types of disturbances and five are concerned 

exclusively with the transient overvoltages. While this review 

is mostly concerned with the reports of transient overvoltages, 

this limited discussion does not mean that other disturbances 

are less significant. 

Power quality surveys have been performed, reported, and 

discussed by many authors, but their results or conclusions are 

0093-999418811 100-1005$01.00 O 1988 IEEE 
1006 IEEE TRANSACTlONS ON INDUSTRY APPLICATIONS, VOL. 24, NO. 6, NOVEMBERIDECEMBER 1988 

SURGE, IMPULSE complete loss of line voltage, but the duration of this outage 

was quite different when it was defined by computer users (as 

short as one half-cycle) or power engineers (seconds, perhaps 

minutes). Now, the users and manufacturers of line conditioners do not make a clear distinction between complete loss of 

line voltage (zero voltage condition), severe undervoltages 

("deep sags"), or the single-phasing of polyphase power 

systems. For example, a momentary flicker of fluorescent 

lighting caused by a brief loss of voltage might be considered 

an outage; however, a brief sag to less than 80 percent of 

WAVEFORM DISTORTION nominal voltage will produce the same visible effect. Some 

UPS manufacturers consider input voltage sags that cause 

transfer to the battery backup operation as outages. Part of the "lNUTES' problem may be that the definition of "outage" has regulatory 

implications for evaluating the performance of public utility 

LOUTAGE 

Fig. 1. Graphic definitions of disturbances. 

not consistent [3]-[14]. Quotations from these surveys, out of 

context, have perhaps also contributed to the confusion. In an 

attempt to clarify the issues, this paper presents a brief review 

of the origins and definitions of disturbances, and then it 

describes the development of monitoring instruments. Comparisons are made among nine published surveys with attempts 

at reconciling results. Finally, an appeal is made for improved 

measurement methods to provide more consistent reporting of 

recorded power disturbances. 

As will become painfully apparent in the review of site 

surveys, the terms used by the workers reporting their 

measurements do not have common definitions. An effort is 

being made within the IEEE to resolve this problem, as 

described later in this paper, but consensus has yet to be 

reached. In this paper, terms describing disturbances are 

consistent with the IEEE Standard Dictionary of Electrical 

and Electronics Terms [15] and with established usage within 

the community of surge protective devices engineers. Two 

examples of this lack of consensus are described here to make 

the point; resolving them is beyond the scope of this paper. 

The generally accepted meaning of surge voltage, in the 

context of power systems, is a short-duration overvoltage, 

typically less than 1 ms or less than one half-cycle of the power 

frequency. This meaning is not that which has been established 

by manufacturers and users of monitoring instruments and line 

conditioners. This unfortunate second meaning is a momentary overvoltage at the fundamental frequency with a duration 

of typically a few cycles. In this paper, this second meaning of 

the word "surge" (a momentary overvoltage) will be signaled 

by the use of quotation marks. What the surge protective 

devices engineers call surge is called "impulse" or "spike" 

by the monitoring instrument community. Fig. 1 shows by 

graphic descriptions the confusion created by the dual meaning 

of the word surge. Acknowledging the desire of users for terse 

labels, we propose for consideration the word "swell" instead 

of "surge" for a momentary overvoltage. 

The term "outage" is another example of confusion created 

by unsettled definitions. Most users agreed that it meant a 

companies. No such distinction has been made in this paper, 

because taking sides on that issue is not within its scope. 

The term "sag" has not yet been defined in the IEEE 

Dictionary, but it is now generally accepted as meaning a 

momentary voltage reduction at the ac power frequency. 

However, details (threshold, duration, etc.) of what characterizes a sag are not well defined. 

Protection from power disturbances is now essential because increasing dependency on computer-based systems for 

industry, commerce, and consumers makes disruptions less 

and less acceptable. The most visible indication of power 

disturbances is the occurrence of operational problems such as 

hardware damage, system crashes, and processing errors. 

Some users of computer systems may accept, albeit reluctantly, operational problems because they see them as unavoidable. Other users may be unaware that otherwise 

invisible power disturbances could be the cause of operational 

problems. A single power disturbance can cost more in 

downtime and hardware damage than the investment in power 

protection that would have prevented the disturbance; almost 

all sites could benefit from a reduction of operational problems 

by improving the quality of the power supplied to the 

computer systems [13]. 

Power line monitoring with sophisticated power disturbance 

recorders has often been advocated as a way to determine if 

any line conditioning is required. While monitoring appears to 

be a logical first step, it has limitations. For example, severe 

disturbances occur infrequently or on a seasonal basis. 

Therefore, monitoring periods of less than a year might not 

produce an accurate power disturbance profile; most users are 

unwilling to wait at least 1 year. Also, power line monitoring 

produces only past performance information, for changes 

within the site, at neighboring sites, or by the utility can 

drastically alter the power disturbance profile. 

While exact prediction of the disturbances to be expected at 

a specific location is almost impossible and attempting it 

would be a fallacy, general guidelines can be formulated. An 

attempt has been made by standards-writing groups to provide 

guidance [16] or specifications reflecting expected disturbances [17]-[19]. Users, however, generally seek specific 

data for their particular case; hence site surveys will still be 

IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 24, NO. 6, NOVEMBERIDECEMBER 1988 

PERIPHERA~ Remote element 

0 power introduce an 

addl tional 

Electromagnetic field ground loop 

couples into loop and Comoosi te 

induces common mode disturbance on input port., line voltImpinging common 

mode disturbance 

is blocked by an I ' I fwAw) 

isolation transformer, neglecting Lf,.* - [Y I -3 Common mode interwinding 1 "" 

capacitance. -A V +'-I& disturbance 

'3 

Ground current from other 

systems couple common mode 

disturbance into grounding conductor of power supply. 

Fig. 4. Three examples of origins of common mode disturbance on power 

input. 

affect a sensitive load. The first type is a disturbance on the 

input power conductors relative to the input power grounding 

conductor. Fig. 4 shows in @ and @ examples of origins for 

these disturbances. This type of disturbance can be limited 

somewhat by a line conditioner, but it is also influenced by the 

location of the line conditioner and the wiring practices. 

The second type is a ground potential difference between 

elements of the computer or remote peripherals connected to 

the computer. Fig. 4 shows in @ an example of this type. This 

type of disturbance is more difficult to limit because it is 

influenced by factors such as the system configuration and the 

impedance of the grounding system. These two factors are 

generally beyond the direct control of the user except in the 

construction of a new facility. 

Because of the broad frequency band involved, wiring 

resonances can make equalizing ground potentials difficult. 

Proper computer system grounding, including a signal reference grid, has been found to be effective against most common 

mode disturbances [25]. However, when remote elements are 

connected to the computer systems by data cables, large 

ground potential differences are possible. Proper surge protection of the power supply and proper grounding of data cables 

will help eliminate hardware damage but might not prevent 

data corruption. When dealing with the situation of example 

@ in Fig. 4, fiber optic links are very effective because they 

provide complete metallic separation of the various elements 

in the system, a separation that might not be sufficiently 

achieved by the discrete opto-isolation devices sometimes 

proposed for that function [2]. 

Normal Mode Disturbances 

Normal mode disturbances are defined as unwanted potential differences between any two current-carrying circuit 

conductors. Fig. 5 shows three examples of the origins of such 

disturbances. Usually a sine wave of nominal voltage is 

desired for a computer power supply. Any deviation from this 

sine wave is a normal mode disturbance. Computer users and 

interact with power system 

source impedance to cause 

disturbance on bus bars (B) 

2 Switching other loads "II P on local system 

@ Impinging ' disturbance '-----I 

(Lightning. 8 

Normal mode 

transformer 

by magnetic = 

coupling. - defined 

Fig. 5. Three examples of origins of normal mode disturbance on 

power input. 

monitoring instruments designers characterize these disturbances by a variety of terms not always clearly defined such as 

sags, surges ("swells"), outages, impulses, ringing transients, waveform distortion, and high-frequency noise. Unfortunately, there is no consensus at the present time on the exact 

meaning of these terms and their underlying quantitative 

definitions such as amplitude, duration, and thresholds, Later 

in this paper, a new effort to remedy this situation is described. 

Historically, the first (unintended) disturbance monitors 

were the actual load equipment; only later, when confronted 

with unexplained failures or malfunctions, did the users start 

monitoring the quality of their power systems. Monitoring 

power quality at the fundamental frequency had long been 

performed by utilities, but the precise characterization of 

microsecond-duration surges in the early 1960's required 

special oscilloscopes. For the next 15 years, combinations of 

oscilloscopes or simple peak-detecting circuits were the basic 

instruments for monitoring transient overvoltages. In the 

1970's commercially-produced digitizers became available, 

and the technology has made continuing progress as experience has been accumulated and faster digitizing circuits have 

been developed. 

Early site surveys were generally limited to voltage measurements in the normal mode. This limited scope reflected 

concerns for damage to sensitive electronic components 

connected across the line. The fact that the source impedance 

of the surge was not recognized as being important in these 

surveys led to the generation of some performance standards 

that do not specify the current-handling requirements for the 

surge protective devices [19]. With the introduction and 

widespread application of clamping protective devices (silicon 

avalanche diodes or metal oxide varistors), the surge current 

diverted through these devices became a very important factor 
MARTZLOFF AND GRUZS: POWER QUALITY SURVEYS 

for proper device selection. Therefore, the need emerged for 

characterizing current as well as voltage surges, but few 

surveys to date have addressed this need. This need offers a 

challenge to designers of monitoring instruments and to 

would-be surveyors. 

This challenge has produced attempts to define an "energy" 

measurement with an instrument which is only a voltmeter. By 

assigning a parametric value to the source impedance of the 

surges and integrating the product (~olts)~.seconds of the 

surges, some knowledge on the energy involved would be 

obtained as suggested in [14]. However, the real question 

concerns the sharing of energy between the impedance of the 

source and the impedance of the load, in this case the nonlinear 

impedance of the protective device. A lengthy discussion of 

the energy contained in the surge versus the energy delivered 

to the protective device is beyond the scope of this paper, but 

the difference needs to be recognized to prevent further 

confusion as future monitoring instruments include an "energy" parameter in their readouts. 

With the present development of sophisticated multichannel 

digitizing instruments, it should be feasible in future surveys 

to monitor both voltage and current in the normal mode as well 

as in the common mode. Note, however, that the current of 

interest is that which the surge source (of otherwise unknown 

impedance) would force through a proposed surge protective 

device. This device would be shunt-connected at the point 

being monitored so that the current to be monitored is not the 

surge current in the direction of undefined downstream loads. 

The amplitude as well as the waveform of the surges needs to 

be characterized for correct application of surge protective 

devices. Peak-reading monitors provide useful information on 

surge activity at a given site, but assessment of the surge 

severity level for the proper sizing of protective devices 

requires waveform and source impedance information [20], 

WI. 

Recent monitoring instruments offer the capability of 

recording potential differences between the neutral and the 

grounding conductor which constitutes one form of common 

mode disturbances. To our knowledge, no instrument has been 

offered for explicit monitoring of potential differences within 

the grounding system itself such as @ and @ in Fig. 4. Some 

types of monitors include current probes and could record 

current in grounding conductors, but this parameter has not yet 

been reported in published surveys. 

One difficulty encountered by users of monitoring instmments in this fast-paced technology is that manufacturers 

introduce improved features in response to specific wishes of 

the users or as a result of their own research; data collected by 

different instruments become equipment-dependent. While 

this continuing progress is a welcome development, it makes 

comparison of survey results difficult without the details on 

the instrument characteristics and methods of measurement. 

Occasionally, an instrument might have limitations or might 

introduce artifacts which are not immediately apparent so that 

the survey results suffer some loss of credibility when these 

possible limitations are discovered [ll], [12]. Users may also 

have difficulty in interpreting complex instrument outputs, and 

excessive simplification of a complex data base can lead to 

some misunderstanding or misapplication of published do

ments; a tutorial effort is then necessary to avoid these pitfa

[271, 1281. 

The instruments used in the various surveys reflect techn

ogy progress as well as logistics constraints resulting in 

diversity of approaches. Nevertheless, all monitoring inst

ments used in past surveys were voltmeters (with o

exception, combining voltage and current measurements) fr

which disturbance parameters were derived. Some of 

monitors recorded a single parameter such as the act

voltage peak or the fact that the voltage exceeded a pre

threshold. Other monitors combined time with voltage m

surements describing voltage waveforms. The record

functions of instruments used in the surveys may be classif

in broad categories. 

Threshold counters-The surge is applied to a calibra

voltage divider, triggering a counter each time a pre

threshold is exceeded. The early types were analog; m

recent types are digital. 

Digitalpeak recorders-The surge is converted to a dig

value which is recorded in a buffer memory for later playb

or printed out immediately after it occurs. In the early types 

recorders, only the peak was recorded; in later types, 

duration of the surge was also recorded, opening the way 

the more complex digital waveform recorders now availab

Oscilloscope with camera-The surge triggers a sin

sweep on the CRT of the oscilloscope which is recorded a

occurs by a shutterless camera with automatic film advan

The oscilloscopes available at that time (the early 1960's) 

not allow differential measurements. 

Screen storage oscilloscope-The surge is displayed a

stored on the cathode ray tube. The writing-speed capability 

these oscilloscopes was a limitation in the late 1960's. 

Digital storage oscilloscope-The surge is digitized 

stored in a shift register for subsequent playback and disp

whenever a preset threshold is exceeded. An important feat

is the capability of displaying events prior to the beginning 

the surge. 

Digital waveform recorder-The surge is digitized 

stored in a manner similar to the digital storage oscillosco

but additional data processing functions are incorporated in 

instrument, allowing reports of many different parameters 

the disturbance relating voltage to time. 

Although some surveys might aim at great accuracy, 

real world experiences such an infinite variety of disturban

that any attempt to describe them in fine detail only restr

general usefulness of the data. Seeking such fine and definit

detail is another fallacy. Some simple instruments can 

considered useful (and inexpensive) indicators of frequ

disturbances; other, more sophisticated (and more expensi

instruments can provide quite comprehensive data on dis

bances (but only on past events from which future disturban

can be extrapolated only by assuming that the causes w

remain unchanged). Thus there is a practical limit to 

amount of detail that a survey can yield, and unreali

expectations of very precise information should be avoide
1010 IEEE TRANSACTIONS ON INDUSTRY APPUCATIONS, VOL 24, NO. 6, NOVEMBERIDECEMBER 1988 

Fig. 6. Varistor upstream of monitor. 

Before attempting yet another broad survey of power 

quality, would-be surveyors need to consider not only improvements in instrumentation but also changes that have 

occurred in modern power systems, in particular the proliferation of surge protective devices. These two differences 

between earlier surveys and the more recent surveys should be 

kept in mind when comparing results and when planning 

future surveys. 

Prior to the proliferation of surge protective devices in lowvoltage2 systems, a limitation had already been recognized 

[17] for peak voltages: the flashover of clearances, typically 

between 2 and 8 kV for low-voltage wiring devices. For that 

reason the expected maximum value cited in the IEEE Guide 

on Surge Voltages [16] reflects this possible truncation of the 

distribution around 6 kV. Unfortunately, some readers of this 

Guide interpreted the upper practical limit of 6 kV as the basis 

for a withstand requirement, and they have included a 6-kV 

test requirement in their performance specifications. A new 

version of this Guide, currently under preparation as a 

Recommended Practice, will attempt to avoid this misinterpretation. 

The number of surge protective devices such as varistors 

used in the United States on low-voltage ac power circuits 

since their introduction in 1972 may be estimated at 500 

million. Therefore, a new limitation exists in the voltage 

surges that will be recorded. A surge-recording instrument 

installed at a random location might be close to a varistor 

connected near the point being monitored. Such a proximity of 

surge protective devices and recording instruments may 

impact present and future measurements in several ways, as 

contrasted to previous measurement campaigns. Four are 

outlined below. 

1) Locations where voltage surges were previously identified-assuming no change in the source of the surges-are 

now likely to experience lower voltage surges, while 

current surges will occur in the newly installed protective 

devices. 

2) Not only will the peaks of the observed voltages be 

changed, but also their waveforms will be affected by the 

presence of nearby varistors as illustrated in Figs. 6,7, and 

8. 

A) If a varistor is located between the source of the surge 

and the recording instrument (Fig. 6), the instrument 

will record the clamping voltage of the varistor. This 

voltage will have lower peaks but longer time to halfpeak than the original surge. 

B) If the instrument is located between the source of the 

' Defined as 1OMl V or less by IEEE and IEC. 

Fig. 7. Varistor downstream of recorder. 

Fig. 8. Voltages measured at beginning and end of 75-m branch circuit for 

surge applied in normal mode at service entrance, with protective device 

installed between line and neutral conductors (from [29]). (a) Connection of 

varistor at end branch circuit. (b) Voltage at service entrance. Vertical: 

10M) Vldiv. (c) Line-to-neutral ;&age. Vertical: 500 Vldiv. (d) Neutraltoground voltage. Vertical: 500 Vldiv. 
MARTZLOFF AND GRUZS: POWER QUALITY SURVEYS 101 1 

Survey 

B-N 

M-H 

Can 

A-S 

G-S 

WBB 

AEM 

0-B 

Goe 

Period 

Circa 

1962-1963 

1963-1967 

Circa 

1969-1970 

1969-1972 

1977- 1979 

Circa 

1982-1983 

1982-1983 

1982-1983 

Circa 

1983-1984 

Locale 

Great 

Britain 

USA 

US 

Navy 

USA 

USA 

Sweden 

USA 

(Alaska) 

USA 

Europe 

* Principal type stated first. 

** See detailed descriptions in text. 

TABLE I 

DETAILS OF THE LOCALES AND INSTRUMENTATION 

System 

Voltage 

System 

Type* 

Power 

Frequency 

Connection Filtered 

Mode Out 

240 

120/240 

2771480 

120 

450 

Not 

Stated 

1201208 

2201380 

1201240 

1201240 

1201208 

2771480 

2201380 

Industrial & 

residential 

Residential & 

industrial 

Shipboard 

Computer 

sites 

Telephone 

facilities 

Industrial 

Isolated 

systems 

Industrial & 

computer 

sites 

lndustrial & 

miscellaneous 

surge and a varistor, or if a parallel branch circuit 

contains a varistor (Fig. 7), the instrument will now 

record the clamping voltage of the varistor, preceded by 

a spike corresponding to the inductive drop in the line 

feeding the surge current to the varistor. 

C) If a varistor is connected between the line and neutral 

conductors, and the surge is impinging between line and 

neutral at the service entrance (normal mode), a new 

situation is created, as shown in Fig. 8. The line-toneutral voltage is clamped as intended; however, the 

inductive drop in the neutral conductor returning the 

surge current to the service entrance produces a surge 

voltage between the neutral and the grounding conductors at the point of connection of the varistor and any 

downstream point supplied by the same neutral. Because 

this surge has a short duration, it will be enhanced by the 

open-end transmission line effect between the neutral 

and grounding conductors [29]. 

3) The surge voltage limitation function previously performed 

by flashover of clearances is now more likely to be 

assumed by the new surge protective devices that are 

constantly being added to the systems. 

4) These three situations will produce a significant reduction 

in the mean of voltage surge recordings from the total 

population of different locations as more and more varistors are installed. However, the upper limit will remain the 

same for locations where no varistors have been installed. 

Focusing on the mean of voltage surges recorded in power 

systems can create a false sense of security and an incorrect 

Analog multithreshold 

Analog single-threshold 

Oscilloscope and Camera 

Oscilloscope and Camera 

Screen storage oscilloscope 

Oscillograph 

Digital multiparameter 

Digital multiparameter 

Digital multiparameter 

Digital storage oscilloscope 

Digital multiparameter 

2-point digital V & I: 

Peak amplitude & time 

Time to 50 percent of peak 

Two digital waveform 

recorders (fast & slow) 

Not Yes 

stated 

L-N No 

L-L No 

(ungrounded) 

Not Not 

stated clear 

L-N Yes 

Common Yes 

(unclear) 

L-N Yes 

L-N (V) No (V) 

Series (I) Yes (I) 

L-G Yes 

description of the environment. Furthermore, the need for 

adequate surge current handling capability of a proposed 

suppressor with lower clamping voltage might be underestimated because some diversion is already being performed. 

This summary includes nine papers published in the United 

States and in Europe, with a brief description of instrumentation design, definition of parameters, and results. Papers are 

listed in chronological order. 

Table I shows details of the locale, system voltage, 

instrument type, and connection mode as described in the 

papers. Other surveys may have been published, particularly 

in Europe, which did not come to the attention of the authors. 

Suggestions for including additional published data in the 

revision process for the Guide on Surge Voltages [16] are 

invited. 

Bull and Nethercot, in a 1964 article [3], report monitoring 

performed in the mid 1960's on 240-V systems in Great 

Britain with instruments of their design. Their initial instrument used vacuum tubes, leading to the development of a 

solid-state circuit which may be considered the forerunner of 

modern monitors. The instrument had several channels, each 

with a different threshold. Eventually, the solid-state instrument was made available commercially, and several units 

were used in some of the monitoring performed in the United 

States and reported in the data base of [16]. 
1012 lEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 24, NO. 6, NOVEMBERIDECEMBER 1988 

The monitoring locations were selected to include a variety 

of conditions, with data being collected for several weeks at 

each location over a total period of 2 years. The results do not 

mention transients above 600 V; it seems that no channels 

were provided above that level because the authors were only 

concerned with the range of 50-600 V. 

Martzloff and Hahn, in a 1970 paper [5], report the 

highlights of measurements made in the 1963 to 1967 period 

on residential, commercial, and industrial circuits, mostly 

single-phase 120 V. Further details, originally held proprietary, were eventually released [30] for sharing information 

with other interested parties. Waveform data were obtained 

with commercial, custom-modified oscilloscopes fitted with 

motordriven cameras. These oscilloscopes were installed at 

various locations where transient activity was suspected. In 

addition, a peak counter circuit was developed, and 90 units 

with a 1200- or a 2000-V threshold were deployed at 300 

locations where there was no prior suspicion of unusual 

transient activity. 

The oscilloscope data gave one of the first indications that 

the traditional unidirectional impulse, long used for dielectric 

testing, might not be representative of surges occurring in lowvoltage circuits. The threshold data indicated locations where 

surges above 1200 V occur frequently (about 3 percent of the 

sample), while other locations appear far less exposed to 

surges. The 100:l reduction of an alarming failure rate of 

clock motors, achieved by increasing the surge withstand 

capability of the motors from 2000 to 6000 V, is documented 

in that paper. 

Cannova, in a 1972 paper [6], reports the monitoring of 

surges on U.S. Navy shipboard 120- and 450-V power 

systems in the late 1960's. Instrumentation used for the initial 

phase of the monitoring program consisted of oscilloscopes 

similar to those used by Martzloff. Provision was also 

included for the option of measuring the transients alone 

(through filters) or superimposed on the ac line voltage; this 

option reflects the old dichotomy, still unsettled to this day, as 

to whether the transients should be measured as an absolute 

value or as a deviation from the instantaneous value of the ac 

sine wave (see the surge and impulse descriptions in Fig. 1, 

and the last column of Table 1). 

The results are not reported separately for 120- and 450-V 

systems, it is not possible to express them in terms of per-unit 

or percentage of nominal system voltage. The statistical 

treatment aims at fitting the recorded transients to a normal 

distribution and concludes that a log normal distribution is a 

better fit. A brief statement is made on the durations of the 

recorded transients (without a statement on how those durations are defined), citing a majority of durations between 4 ps 

and 6ps, with a few at 19 ps. 

From the data base, acknowledged to be a small total 

number of events, a voltage protection level of 2500 V was 

defined. The specification of a 2500-V 1.2150-ps voltage 

withstand by DOD STD 1399 was derived from this survey. 

Two aspects of the conclusions are especially worth noting: 

1) there was no information on the source impedance of the 

surges, and yet the data eventually served to specify requirements for surge protective devices; and 2) a large difference in 

frequency of occurrence was noted among ships of the same 

type and class, similar to the observations on land surveys. 

Allen and Segall, in a 1974 paper [7], report the monitoring 

of several types of power disturbances at computer sites, 

performed with oscilloscopes, oscillographs, and digital instruments, in the 1969-1972 period. Details of the instrumentation were described in a separate paper [31]. Disturbances 

are described as overvoltages and undervoltages, oscillatory 

decaying disturbances, voltage spike disturbances, and outages. The terms sag and "surge" ("swell") had not yet made 

their appearance in the jargon. 

The survey was conducted in two phases. In a first phase, 

preliminary information was obtained on ranges of disturbances, leading to the development of a second generation of 

monitors deployed in the next phase. The recorded disturbances are described by plots and histograms. The highest 

surge recorded in the first phase is shown as 350 V. In the 

second phase, the monitors grouped all surges into three 

categories, the highest having a range of 100 percent (of line 

voltage) to infinity, so that no detailed information is provided 

to describe high peak values. The survey does report in detail 

the occurrence of undervoltages and overvoltages, providing a 

basis for the comparisons with the Goldstein-Speranza study 

made later in the present paper. 

Goldstein and Speranza, in a 1982 paper [8], report the 

monitoring of several types of disturbances at a variety of 

locations in the Bell System, with digital multiparameter 

instruments, in the 1977 and 1979 period. The conditions of 

the survey are documented, including instrument locations and 

definitions of the parameters as well as the methods of data 

processing. 

The findings are briefly reported with emphasis on predictions for disturbances expected at specific sites. The prediction 

is obtained by using a statistical model derived for all sites and 

making adjustments reflecting specific site conditions determined by a limited survey at that site. The authors are 

emphatic on the point that the lack of correlation between sites 

prevents blanket application of the overall findings to any 

specific site, but that useful predictions are possible by 

combining the overall data with limited knowledge on specific 

site data. This concept is echoed in the Guide on Surge 

Voltages [16], where the frequency of occurrence is presented 

in graphic form with well-defined slopes but with a wide band 

of possible exposures, depending on the particulars of the site. 

A Polya distribution is identified by Goldstein and Speranza 

as the best fit for this type of rare events data, in contrast to 

other surveys where their authors attempted to fit a normal 

distribution or a power or exponential law profile. 

Wernstrom, Broms, and Boberg, in a 1984 report 

published in Sweden and circulated in the United States as an 

English draft translation [lo], report monitoring of industrial 

2201380-V systems by digital multithreshold instruments, 

corroborated by waveform recording with digital storage 

oscilloscopes. The parameters to be recorded and reported are 

defined in an introductory section; however, their description 

of "common mode" and "differential mode" in the English 

translation does not correspond exactly to symmetrical and 

asymmetrical voltages defined by the IEC. In the section 
MARTZLOFF AND GRUZS: POWER QUALITY SURVEYS 10

discussing transient sources and propagation, they make a 

significant comment that "common mode voltages are the 

most interesting and at the same time are the voltages most 

difficult to defend against. " 

The range of surges recorded extends from 200 to 2000 V. 

In a summary tabulation, rise times are shown as ranging from 

20 to 200 ns and duration from 0.2 to 2.5 ,US. An interesting 

additional measurement was made by simultaneous recordings 

at two distant points of the power system, showing some 

aspects of the propagation and attenuation of a surge. The 

survey also shows a wide difference of surge activity among 

sites but a relatively constant slope of the rate of occurrence 

versus level. 

Aspnes, Evans, and Merritt, in a 1985 paper [ll], report a 

survey of the power quality if rural Alaska at isolated power 

generation facilities. The monitoring instruments are identified as one of the contemporary commercial digitizing 

monitors. A very comprehensive summary of the recordings is 

presented including frequency deviations (a unique situation in 

these isolated systems), sags and "surges" ("swells"), 

impulses (i.e., surges), and outages. 

Because the sites were in isolated systems (their installed 

capacity or system impedance is not stated), one would expect 

differences from the typical survey of interconnected power 

systems. m ract suspectea ainerences were the motivation for 

conducting the survey. Thus finding differences in the results 

would not be particularly meaningful from the point of view of 

this paper aiming at comparisons. However, bringing up this 

survey serves the purpose of noting that some ambiguity 

surfaced in connection with the possibility that built-in surge 

protection in the monitors might have attenuated the surges 

being recorded. Knowing the source impedance of the surges 

(not the impedance at power frequency) would have settled the 

issue. This case history point out again the desirability of 

including surge current monitoring in future surveys as a 

method of characterizing the source impedance of the surges. 

Odenberg and Braskich, in a 1985 paper [12], report the 

monitoring of computer and industrial environments with a 

digital instrument capable of the simultaneous recording of 

voltage surges and current surges. This new capability for 

relating voltage and current shows a growing awareness of the 

need to monitor current surges-an improvement over previous surveys limited to the measurement of voltages. However, the reported surge currents are those of a current toward 

undefined loads downstream from the instrument; they do not 

include any measurement of the current through a shuntconnected surge diverter, a measurement that would have 

provided new information on the source impedance of the 

surges. 

The digital processing applied by the instrument yields two 

points of the surge: the peak value with the time to reach peak 

and the time elapsed until decay to 50 percent of the peak 

value. From these two points, a "waveform" description is 

proposed without any other information on the actual waveform. From a large number of recorded surges (over 250 000 

events) a startling finding is cited: 90 percent of the recorded 

surges have their 50-percent point in a narrow window of 900- 

observations reported by other surveys have not been succe

ful. 

Goedbloed, in a 1987 paper [14], describes in detail 

custom-built automated measurement system monitoring 22

380-V networks in Europe. The automated measureme

system reflects the progress made in digitizing techniqu

since the Bull-Nethercot days of vacuum tubes. By combini

two commercial recorders with a custom interface, t

developers obtained detailed recordings with a 10-ns sampli

interval and 20-ps window on the first recorder and a 1-

sampling interval and 2-ms window for the second recorde

The system included a provision for automated da

reduction, yielding raw data as well as statistical informati

on amplitude, rate of rise, energy measure, spectral densi

and conversions from time domain to frequency domain. W

a relatively low threshold of 100 V above the line voltage, t

distribution of occurrences is weighted toward low arnp

tudes; nevertheless, occurrences are reported above 3000 V

The paper also addresses indirectly the question of norm

mode versus common mode surges by discussing symmetric

voltage and asymmetrical voltage as defined in the IE

Dictionary [24]. An indirect definition is proposed for a thi

type identified as the "so-called non-symmetrical voltag

which was the mode of monitorine used in this survev. line 

grounding conductor (called "protective earth" or "protectiv

conductor" in Europe). This third type is currently incorp

rated in the more general definition of common mo

proposed by the IEEE Guide on Surge Testing, which mig

leave some ambiguity on the definitions (see Fig. S), or lead 

considering "pure common mode" as opposed to som

combined mode in which both normal and common (pu

modes are combined. Looking for guidance in IEC definitio

does not help much; the IEC definition addresses de

networks, but the Goedbloed paper states that nearly 

networks monitored were of the TN type-that is, phas

neutral (implying a wye), and protective-earth conducto

The paper clearly states the mode of connection so there is 

ambiguity, but this instance serves again to illustrate the ne

to harmonize definitions. 

Relative Occurrence of Different Types of Disturbances 

Two of the surveys reviewed in this paper have been wide

cited, one performed in the early 1970's by Allen and Seg

(A-S for short) [7], and the other performed in the late 197

by Goldstein and Speranza (G-S) [8]. However, the findin

do not a first appear to be in agreement; a detailed comparis

of these two surveys provides a good illustration of the pitfa

of superficial interpretation of survey results. 

A cursory comparison of the results (Table II) might le

one to conclude that a significant change in power disturbanc

at computer sites occurred between 1972 (end of the A

study) and 1979 (end of the G-S study). A-S reported 88

' A related issue, now being addressed but not yet resolved, is the eff

produced on the amplitudes of common mode surges by different practices 

grounding the neutral (at the service entrance or at the remote substati

1100 ps. Attempts to reconcile this singular finding with the Comments are invited on this aspect of characterizing the environment. 
1014 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 24, NO. 6. NOVEMBERIDECEMBER 1988 

TABLE I1 

UNRECONCILED COMPARISONS BETWEEN THE GOLDSTEIN-SPERANZA 

AND ALLEN-SEGALL RESULTS 

G-S Study A-S Study 

Date of Study 

Duration (monitor months) 

Number of Sites 

Oscillatory, decaying 

Impulses 

Sags 

"Surges" 

Outages 

* Sites confined to Bell System. 

** Included in impulses. 

TABLE nI 

MONITOR THRESHOLDS 

G-S Study A-S Study (%) 

Sags1"Surges" 

Oscillatory 

Impulses 

percent of observed disturbances as spikes, impulses, and 

transients, 11.2 percent as sags, and 0.47 percent as outages. 

G-S, on the other hand, reported 87 percent of the observed 

disturbances as sags, 7.4 percent as impulses, 0.7 percent as 

"surges" ("swells"), and 4.7 percent as outages (which they 

call power failures). 

Taking a more careful look at the monitoring thresholds 

used in each study (Table III) helps to explain why the number 

of impulses appear to have decreased and the number of sags 

appear to have increased. Since G-S use a threshold of -4 

percent for sags while A-S use - 10 percent, one can expect 

the G-S study to indicate a higher percentage of sags, because 

the sags between - 4 and - 10 percent are not included in the 

A-S study. Oscillatory decaying disturbances are not specifically identified in the G-S study but are included under the 

category of impulses. The threshold for impulses used by G-S 

(200 V for 120-V lines, or 118 percent) is higher than that used 

by A-S (f 10 percent). Because the rate of occurrence 

increases steeply for lower amplitude disturbances, one can 

expect a drastic reduction in the percentage of impulses 

reported by the G-S study as compared to the A-S study. 

The increase in percentage of power outages reported by 

G-S may be explained by the shift in the number of 

disturbances observed due to other threshold changes. Percentages can be a very misleading basis for comparison unless 

all conditions are equal. For example, the incidence of power 

outages observed in both studies is very similar, even though 

the percentages are one order of magnitude apart; A-S report 

0.6 occurrence per month while G-3 report 0.4 occurrence per 

month. 

Both studies present summaries and statistical analyses of 

their disturbance data in difference ways. A-S use only the 

observed disturbances as a data base and present results as 

incidence rate graphs. Incidence rates of sags and impulses at 

different thresholds are given by A-S, allowing a more direct 

comparison with the disturbance thresholds of the monitoring 

instruments used in the G-S study. 

The G-S study presents a statistical model of the disturbance 

rates to predict the incidence rates at predefined disturbance 

levels, selected to correspond to those levels generally 

expected to cause computer systems problems: impulses 

greater than 200 V (1 18 percent of nominal peak voltage), sags 

greater than -20 percent of the nominal voltage, and 

"surges" ("swells") greater than 10 percent of nominal. The 

G-S model states the disturbance rates in terms of probability, 

such as 50 percent of the sites will have less that "x" 

disturbances per year or 90 percent of the sites will have less 

than "y" disturbances per year, but with a cautionary note that 

there is no firm correlation between sites, making specific 

predictions from overall results somewhat uncertain. 

When the disturbance rates at the same thresholds are 

compared for the A-S data and the G-S model (for 75 percent 

probability), the results are surprisingly similar (Table IV). 

The conclusions of these two studies are that deep sags 

contribute about 62 percent of the power system problems 

which are related to normal mode disturbances, severe 

impulses are responsible for 21 percent outages for 14 percent 

and "surges" ("swells") for 2 percent. 

Differences in Surge Amplitudes 

The amplitudes of the surges reported in the surveys vary 

over a wide range, and comparisons are difficult because the 

data are not presented in a uniform format. An attempt was 

made to get a quantitative comparison of the amplitudes 

reported in the surveys; however, the exercise was quickly 

found to be futile because of the following two main reasons. 

1) Looking at "maximum values," one finds that in some 

surveys the quoted maximum is actually a value in excess 

of the range of the instrumentation, while for others it is the 

measured value. There are too few points and insufficient 

information to attempt a statistical treatment of this 

truncated data base (censored data in statistical terms). 

Furthermore, the quoted value in some surveys is the total 

voltage (instantaneous value of ac sine wave plus surge), 

while in others the sine voltage has been filtered out. When 

surges are in the range of several thousand volts (the 

concern being damages), the difference between the two 

definitions is not significant; however, when surges are in 

the range of a few hundred volts (the concern being 

malfunctions), the difference is significant. 

2) Because the lower threshold of the recorder varies among 

surveys, and the frequency of occurrences increases 

dramatically with lower threshold, the labels of average, 

median, most frequent, typical, etc., are not meaningful 

for comparing amplitudes. The preceding discussion of 

A-S and G-S results has illustrated the profound effect of 

threshold selection on reported results when they are 

expressed in percentages. 

For these two reasons, any comparison at the present stage 

of inconsistency in report formats can only be qualitative. 

Conjecture or speculation, rather than hard facts, might 
RECONCILED COMPARISONS 

Normal Mode Power Disturbances Per Year 

G-S Model A-S Study Combined Data 

No. of Percentage No. of Percentage No. of Percentage 

Events of Events Events of Events Events of Events 

Impulses (greater than 100-percent peak) 8 15 12 27 10 2 1 

Sags (greater than - 20-percent rms) 36 68 25 57 30 62 

"Surges" (greater than + 10-percent rms) 2 4 0 0 1 2 

Outages (0 V, on 1 or more phase) 7 13 7 16 7 14 

TOTAL 53 100 44 100 48 100 

Fig. 9. Appearance of recordings made with storage oscilloscope and high-speed oscilloscope. (a) Low full scale and slow sweep

Screen storage oscilloscope, 1968 vintage (same type as used by Allen-Segall). (b) High full scale and slow sweep. Screen storage 

oscilloscope, 1968 vintage (same type as used by Allen-Segall). (c) High full scale and fast sweep. High-speed oscilloscope, 1968 

vintage. 

explain differences, as illustrated in the following two examples. 

The relatively small number of high-amplitude surges 

reported by Allen-Segall compared to other surveys 1161 might 

be explained by a limitation of their instrument. This 

explanation was submitted as a written discussion of the paper, 

but because of the "conference paper" status of the paper it 

was not published by the IEEE. 

Briefly stated, the storage oscilloscopes used by A-S had the 

limited writing speed of contemporary technology; furthermore, the small amplitude set for full scale was such that a 

high-amplitude transient would have its peak off screen and 

the steep rise would not be seen on the phosphor. Fig. 9 shows 

a set of oscillograms recorded in the laboratory by Martzloff in 

1974, with the same model of oscilloscope as used by A-S: an 

actual 2200-V transient overvoltage appears as a benign 400-V 

transient if the oscilloscope sensitivity is set in anticipation of 

relatively low-amplitude transients and relatively slow speed, 

as was the case in the A-S study 1311. 

Another difference in observed amplitudes is found in the 

results of the Alaska power survey [ll]. One possible 

explanation for the relatively low surge level observed was 

suggested in the discussion of that paper: the built-in surge 

protection of the power supply for the internal electronics of 

the monitor might have reduced the levels of the surges 

observed by the monitors which had their power cord and 

monitoring probe connected to the same duplex receptacle. 

A general explanation of differences in amplitude

the various surveys might be the observation by som

authors of the lack of correlation between sites. Fur

some surveys include sites where equipment fail

experienced or expected, while other surveys wer

sites not singled out for particular problems. 

differences in overall results of various surveys mig

be the result of the different surge exposure at the 

monitoring. This explanation implies that surveys w

needed where specific information is desired. 

Differences in Waveform 

From those surveys made with waveform recordin

ity, the "typical" forms suggested by each author 

collected in Fig. 10. The finding of ringing waves, a

to the traditional unidirectional impulses, seems 

these low-voltage circuits. 

Martzloff and Hahn were among the first to r

waves. Their reported measurements were incorpo

the data that resulted in the eventual selection of a 

ring wave with a 250- or 500-ns rise time for the UL 

Ground Fault Circuit Interrupters [32] and the 0

kHz ring wave of the IEEE Guide on Surge Volt

The data base of the Guide on Surge Voltages 1161 shows os

ring waves recorded in the Bell System during a survey before t

Speranza study, but not otherwise published. 
1016 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 24, NO. 6, NOVEMBERIDECEMB

MICROSECONDS 

(a) 

Typfcal duration: 4-bus 

Longest observed: 19~s 

Fig. 10. "Typical" waveforms reported in site surveys. (a)-(c) Three examples of surges recorded by Martzloff. (d) Typical 

waveform according to Goedbloed. (e) Description of waveform by Cannova. (0 Description of waveform by Odenberg-Braskich. 

(g)-(i) Three examples of surges recorded by Wernstrom, Brorns, and Boberg. 

While Cannova does not report detailed descriptions of the 

waveforms, the statements "4 to 6 ps" and "up to 19 ps" 

could be interpreted either as a time to half-value or as the time 

between the initial rise and the first zero crossing of a ringing 

wave. Interestingly, that data base led to the specification of a 

unidirectional longer impulse, the classic 1.2150-p voltage 

impulse, for conservative rating of candidate surge protection 

devices to be installed in the shipboard environment [19]. 

Wernstrom, Broms, and Boberg show three examples of 

recordings. The first is indeed a ring wave with a frequency of 

about 500 kHz and a rise time of 200 ns. The second example 

is a burst of nanosecond-duration transients, similar in shape 

to the proposed IEClTC65 Electrical Fast Transients [33]. The 

third example is (of all things) a unidirectional (almost) 

impulse. 

The data reported by Odenberg and Braskich are different 

from the others in that only two points of the waveform are 

reported: peak and 50 percent of peak amplitude. As such, this 

description is not a complete waveform; furthermore, their 

report that 90 percent of their 250 000 recordings show 

percent point occurring between 900 and 1100 ps is 

among all the surveys. 

The Goedbloed data presentation reflects concerns a

ing interference rather than damage; hence, the empha

given to amplitude, rate of rise, and energy rath

waveform. An oscillogram characterized as "typic

presented in Fig. 10: it is a ring wave with a frequ

about 800 kHz. In the data processing by conversion 

recorded events to a standardized trapezoidal pul

median of the time to half-value is found to be abou

which is an indirect measure of the relatively short dur

the observed surges. 

Agreement and Disagreement on Rate of Occurren

versus Levels 

Several of the survey authors have attempted to fit a 

distribution or a simple relationship between the 

occurrence and the amplitude of the surges. In maki
Peak Surge 

8-N = ~ull & Nethercot (compostte) H = Martzloff (~ef.[30]) Can = Cannova 6-s = Goldstein & Speranza NEB = Nernstrom et a1 (upper limit) Goe = Goedbloed 

clock - 2 kv 6 6 kV points only 

Fig. 1 I. Comparison of slopes of frequency of occurrence versus level of 

surges among surveys. 

attempts, the frequency of occurrence is presented in different 

forms such as histograms, cumulative frequency, or number of 

occurrences in excess of a stated surge level. Fig. 11 shows on 

a single chart the relative distributions of the findings, 

normalized for voltage level and frequency of occurrence for 

each survey result: the slope of the lines is what can be 

compared, not the absolute rate of occurrence. It is remarkable 

that slopes are similar among the surveys if one keeps in mind 

that the absolute frequency of occurrence is site-dependent. 

The ambiguities plaguing the field of site surveys have 

become apparent to many interested workers, resulting in the 

formation of a new Working Group Monitoring Electrical 

Quality sponsored by the Power Systems Instrumentation and 

Measurements Committee. The scope of the document being 

developed by this Working Group is as follows. 

This Recommended Practice covers monitoring the electrical quality of single-phase and polyphase ac power systems. 

To obtain consistent descriptions of disturbances in the 

electrical quality of power systems, this document presents 

definitions of nominal conditions and of deviations from 

these nominal conditions that may originate within the 

source of supply or from interactions between the source 

and the load. 

generic description is presented of the susceptibility 

equipment to deviations from nominal conditions. 

To obtain comparable results from monitoring 

performed with different instruments by different op

this document presents recommendations for meas

and application techniques, and interpretations of r

While there is no implied limitation on the voltage r

the power system being monitored, signal inputs 

instruments are limited to 1000 V or less. Fund

frequencies of the ac power systems being monitore

the range of 45 to 450 Hz. 

Although it is recognized that the instruments may 

used for monitoring dc supply systems or data trans

systems, details of application to these cases ar

consideration and are not included in the present sco

also recognized that the instruments may perform m

ing functions for environmental conditions (temp

humidity, high-frequency electromagnetic radiation

ever, the scope of this document is limited to the co

electrical parameters derived from voltage or from 

measurements, or both. 

Contributions to the development of this docum

invited and welcome, and further information may be 

from the authors. 

A review of power quality site surveys conducted 

last twenty years reveals interest facts, and close exam

of the results can dispel some fictions and fallacies. 

1) Considerable progress has been made in recording 

ity of monitoring instruments, mostly as the r

progress in the hardware and software used in d

systems. Improvements include multichannel sync

recording of different parameters, fast data acq

automated data reduction, and improved resolutio

2) With the steady progress and expanded capab

instruments, it becomes increasingly important to 

greater consistency in definitions of the disturbanc

eters and the methods of application of the mo

instruments. 

3) Site-to-site variations in exposures preclude makin

predictions for a specific site from an overall data b

useful predictions can be made by adjusting the ove

base only slightly by limited data collection at th

interest. 

4) The steady increase in the number of surge pr

devices being installed in low-voltage power circu

last several years can be expected to continue. T

might be a lowering of the mean values of observe

but not necessarily the extreme values of the distr

5) Differences among results indicated by a cursory c

son can in many cases be resolved by a closer exa

of the conditions under which the surveys were co

However, some differences appear less likely 

explained if raw data have been processed and th

parameter measurements are no longer avail
reports and sharing of experiences at technical meetings 

might help overcome this difficulty. 

6) A new IEEE Working Group on Monitoring Electrical 

Quality has been formed with a broad scope that encompasses this process of improving consistency in the 

definitions and interpretation of power disturbances. In 

addition, the IEEE Working Group on Surge Characterization is also attempting to obtain a broader data base for the 

revision of the Guide on Surge Voltages. These two 

groups are ready to provide counsel and forum to any 

would-be surveyor in planning and reporting the collection 

of new data on disturbances, thus avoiding later difficulties 

in incorporating the results in a shared data pool. This 

paper is presented in support of this effort and to promote 

greater participation among interested workers and users. 

The contributions to this review by Arnold Perrey, 

Catherine Fisher, and Robert Palm, Jr., respectively, in the 

literature search, organization, and graphic presentation, are 

gratefully acknowledged, 

T. S. Key, "Diagnosing power quality-related computer problems," 

IEEE Trans. Ind. Appb, vol. IA-15, no. 4, JulyIAug. 1979. 

F. D. Manzloff, "The protection of computer and electronic systems 

against power supply and data line disturbances," General Electric 

Company, Schenectady, NY, Report 85CRW84, 1985. 

I. H. Bull and M. A. Nethercot, "The frequency of occurrence and 

magnitude of shon duration transients in low-voltage supply mains," 

Radio Electronic Engineer, Sept. 1964. 

Committee Report, "Bibliography on surge voltages in ac power 

circuits rated 600 V and less," IEEE Trans. Power App. Syst., vol. 

PAS-89, no. 6, JulyiAug. 1970. 

F. D. Martzloff and G. J. Hahn, "Surge voltages in residential and 

industrial power circuits," IEEE Trans. Power App. Syst., vol. PAS89, no. 6, JulylAug. 1970. 

S. F. Cannova, "Short-time voltage transients in shipboard electrical 

systems," in IEEE IAS 1972 Annual Meeting Conf. Rec. 

G. W. Allen and D. Segall, "Monitoring of computer installation for 

power line disturbances," presented at the IEEE PES Winter Meeting 

Conference, New York, Jan. 1974, Paper C74199-6. 

M. Goldstein, and P. D. Speranza, "The quality of U.S. commercial ac 

power," in Proc. INTELEC Conf., 1982. 

0. B. Laug, and D. L. Hillhouse, Analysis of Requirements for 

Shipboard Voltage Spike Suppressors, NBSIR 84-2844, National 

Bureau of Standards, 1984. 

H. Wemtrom, M. Bmms, and S. Boberg, "Transient overvoltages on 

ac power supply systems in Swedish industry," Foorsvarets 

Forskningsanstalt, Huvudavdelning 3, Sweden, Report FOA E 300(nE2, 1984. 

1. D. Aspnes, B. W. Evans, and R. P. Merritt, "Rural Alaska electric 

power quality," IEEE Trans. Power App. Syst., vol. PAS-104, no. 

3, Mar. 1985. 

R. Odenberg and B. Braskich, "Measurements of voltage and current 

surges on the ac power line in computer and industrial environments," 

IEEE Trans. Power App. Sysi., vol. PAS-104, no. 10, Oct. 1985. T M Gn17c ''Power dkturhances and comouter svstems: A com~ari- son of the Allen-Segall and the Goldstein-Speranza power he 

monitoring studies," in Proc. 1986 Electrical Overstress Exposition, 

Nelson Publishing Company, Nokomis, FL, Jan. 1986 

J. J. Goedbloed, "Transients in low-voltage supply networks," IEEE 

Trans. Electromagn. Compat., vol. EMC-29, no. 2, May 1987. 

IEEE Standard Dictionary of Electrical and Electronics Terms, 

ANSIIIEEE Std 100-1984. 

Gu~de on Surge Voltages in Low-Voltage AC Power Circuits, 

ANSIIIEEE C62.41-1980. 

Insulation Coordination within Low-Voltage Systems, Including 

Clearances and Creepage Distances for Equipment, IEC 664-1980. 

Control of Electromagnetic Interference, DOD

STD

[I91 Interface Standard for Shipboard Systems, DOD-STD-

1978. 

[20] F. D. Martzloff, "Varistor versus environment: W

match," IEEE Trans. Power Del., vol. PWRD-1, no

[21] W. Meissen, "Uberspannungen in Niederspannungsn

voltages in Low-Voltage Networks), Elektrotechnisch

vol. 104, 1983. 

[22] G. W. Allen and D. Segall, "Impact of utility distribu

power line disturbances," presented at the IEEE PES Su

Conf., July 1976, Paper A763884. 

[23] IEEE Guide on Surge Testing for Equipment Conn

Voltage AC Power Circuits, ANSIIIEEE C62.45-198

1241 IEC Multilingual Dictionary of Electricity, publishe

distributed in cooperation with Wiley-Interscience. 

1251 Guideline on Electrical Power for ADP Installations, 

National Bureau of Standards, 1983. 

1261 F. D. Martzloff, "Matching surge protective devices to 

ment," IEEE Trans. Ind. Appl., vol. IA-21, no. 1, J

1271 T. S. Key and F. D. Martzloff, "A consensus on 

grounding sensitive electronic equipment," in Conf. R

Annu. Meet., vol. 2, Sept. 1986, pp. 1054-1060. 

[28] Recommended Practice on Powering and Groun

Electronic Equipment in Commercial and Industri

tems, IEEE PI 100. 

[29] F. D. Mwtzloff and H. A. Ganper, "Surge and 

propagation in industrial power lines," IEEE Trans. In

IA-22, no. 4, JulylAug. 1986. 

[30] F. D. Martzloff, "Transient overvoltages in second

General Electric Company, Schenectady , NY, Repo

1981. 

[31] G. W. Allen, "Design of power-line monitoring equi

Trans. Power App. Syst., vol. PAS-90, no. 6, NovJD

[321 UL Standard for Safety 943, Ground Fault Circui

Underwriters Laboratories, 1976. 

1331 Electrical Fast Transients-Burst Requirements, IEC 

4. 

Franqois D. Martzloff (M15&SM

born in France where he completed 

ate studies. He also received th

Georgia Institute of Technology, A

and the MSIA from Union College

NY, in 1971. 

He was with General Electric f

working on transient measurement

tion of electronics, and application 

is presently with the National Institu

and Technology, Gaithersburg, M

conducted electromagnetic interference. He is contributing to t

of national and international standards in the IEEE PES S

Devices Committee, IEEE PES Power Systems Instrumentatio

ments Committee, IEEE IAS Power Systems Engineering C

C62 Surge Arresters Committee, and IEC TC77lWG6 on E

Compatibility. 

Thomas M. Gmzs (S'74-A'77-M'86

B.S. degree from Franklin Univers

OH, and the M.B.A. degree from th

Dayton, Dayton, OH. 

He is currently a Technical Mar

for the Liebert Corporation Columb

he 1s reswnslble tor me u$> and ro

ing ~pplication Engineering Dep

joining Liebert in 1981, he has bee

applying power conditioning produc

based systems. He has written se

articles and has made presentations around the country on 

power disturbances, power conditioning, and gmnding 

systems. Prior to joining Liebert, he was an Electrical Desig

seven years with Dresser Industries. 

Mr. Gmzs is a member of the IEEE IAS Working Grou

grounding sensitive electronic equipment.