f.martzloff@ieee.org

© 1992 IEEE

Reprinted, with permission, from

IEEE Transactions on Industry Applications, Vol.28, No.6, November/December 1992

Significance:

Part 2 Development of standards – Reality checks

Demonstration ad absurdum: 

Accepting the premise of proposed IEC 100/1300 high-energy surges being representative of the environme

modeling the response of typical metal-oxide varistors, leads to the conclusion that most of the billions of va

in service should fail at alarming rates – but we know they do not. Ergo, the premise is not valid and the pr

high-energy test should not be considered as an across-the-board requirement. 

(See also paper “MOV - VDE" in this Part 2 for an experimental demonstration.)

On the other hand, the tests proposed in IEEE Std C62.41 would not result in systematic failure of common

varistors and consequently appear more realistic
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 28, NO. 6, NOVEMBER / DECEMBER 1992 

Validating Surge Test Standards by Field 

Experience: High-Energy Tests and 

Varistor Performance 

Charles Fenimore, Member, IEEE, and Fran~ois D. Martzloff, Fellow, IEEE 

Abstract-New, high-energy surge tests are emerging in IEEE 

and IEC standards. Field experience offers a valuable criterion 

for validating or invalidating proposed standards. A proposal 

under consideration by the IEC involves so much energy that a 

varistor of the voltage rating commonly used in protecting load 

equipment, if subjected to this test, would almost certainly fail. 

Yet, reported varistor failure rates do not reflect such a situation. Thus, a reexamination of the premises that led to the 

proposed test specifications appears necessary. Proposals for 

high-energy tests as additional waveforms in the new version of 

IEEE C62.41, on the other hand, lead to current and energy 

levels that do not place typical varistors in immediate jeopardy. 

Thus, they appear more consistent with field experience. 

NATURAL approach in defining the surge tests to A, e performed on any equipment is to attempt duplicating the conditions observed in site measurements. 

However, this approach would lead to a situation where 

general conclusions are drawn from limited measurements of specific surge occurrences. It has, in fact, led to a 

multitude of proposals for test standards that may subsequently be applied outside of their original, correct context because no other standard is available at the time. An 

example of this situation may be developing with the 

proposal by Technical Committee 77 of the International 

Electrotechnical Commission (IEC) for a high-energy 

100/1300-ps surge test. 

To evaluate the effects of various proposed or existing 

high-energy stress tests on commonly used varistors, this 

paper presents a simple yet effective model of a surge 

generator. The evaluation proceeds by quantifying the 

current through the varistor and the corresponding energy 

deposited in the varistor. The computed results are compared with the published device ratings to predict the 

likelihood of failure. This likelihood is then compared 

Paper IPCSD 90-40, approved by the Power Systems Protection Committee of the IEEE Industry Applications Society for presentation at the 

1990 Industry Applications Society Annual Meeting, Seattle, WA, October 7-12. This work was supported by the Building Industry Consulting 

Service International (BICSI) and by the US. Army Research, Development, and Engineering Center. Manuscript released for publication 

September 24, 1991. 

The authors are with the Electricity Division, National Institute of 

Standards and Technology, Gaithersburg, MD 20899. 

IEEE Log Number 9203290 

with the available information from field experience on 

failure rates. 

Any immunity test should be conducted with an objective that is more subtle than the goal to "duplicate the 

environment." A test stress is applied to a device not to 

demonstrate that it can survive any of the stresses that it 

will encounter in nature but only to demonstrate for the 

benefit of both manufacturer and purchaser that the 

device can survive an agreed-on, simple, and reproducible 

stress. From surviving the test stress, the inference is 

made, subject to confirmation by field experience, that the 

device does have the ability to survive the infinite variety 

of stresses that it will encounter during its life in the real 

world. In other words, simple test stresses are useful 

because they can be reproduced over a period of time at 

the same facility and between facilities, providing a common language and a standard of comparison that is essential to conduct orderly transactions. Test standards should 

not, however, be misconstrued as representing natural 

phenomena. They are effective only if they discriminate 

between those devices with a potential for long field 

survival and those that are likely to fail. 

The proposed 100/1300-ps IEC test should be reexamined with this philosophy in mind because it appears that 

commonly used varistors would be expected to fail when 

subjected to this test. Anecdotal experience does not 

support the prediction of failure in the field, raising questions as to the general validity of this test. On the other 

hand, high-energy tests derived from new proposals contained in the revised version of IEEE Std. C62.41 do not 

lead to contradiction between field experience and predicted test results. 

PROPOSED IEEE AND IEC HIGH-ENERGY TESTS 

Metal-oxide varistors that suppress surges by absorbing 

energy have proliferated in low-voltage ac power circuits. 

Consequently, new high-energy tests have been proposed 

to assess the ability of these varistors to withstand the 

corresponding stress. In a major revision of the IEEE 

Guide C62.41 [I] (emerging as a Recommended Practice 

[2]), an additional waveform has been proposed to assess 

this ability. The proposal is a 10/1000-ps surge, with 

three "system exposure" levels, which are defined below. 

The IEC Technical Committee TC77 is considering a 

0093-9994/92$03.00 0 1992 IEEE 
FENIMORE AND MARTZLOFF: VALIDATING SURGE TEST STANDARDS BY FIELD EXPERIENCE 

surge test requirement based on the scenario of currentlimiting fuses clearing a fault at the end of a cable, where 

the energy trapped in the system inductance causes a 

large transient at the time the fuse interrupts the current 

[31. That scenario was first described and quantified by 

Meissen [4] and incorporated in German Standard VDE 

0160 [5]. 

The new C62.41 Recommended Practice proposes, 

among other waveforms, a high-energy stress defined by 

an open-circuit voltage and a source impedance at three 

"system exposure" levels. For the "low exposure" level, no 

high-energy stress is proposed; for the "medium exposure" 

level, the surge environment involves a crest of two times 

the system peak voltage with a source impedance of 1 0. 

For the "high exposure" level, the crest is 2.3 times the 

system peak voltage, whereas the source impedance is 

only 0.25 0. 

The IEC proposal appears to be based on the VDE 

0160 standard, which specifies the direct discharge of a 

large capacitor-thousands of microfarads-into the 

equipment under test (EUT). The VDE test procedures 

are not quite clearly outlined at this point but might be 

interpreted as readjusting the capacitor charging voltage 

after connecting the EUT to the surge generator in order 

to maintain the specified test voltage across the EUT. 

That approach would be diametrically opposed to the 

generally accepted practice of performing a surge test 

with a generator having the capability of delivering a 

well-defined open-circuit voltage and short-circuit current 

or an open-circuit voltage associated with a specified 

source impedance (see Fisher and Martzloff [6] and the 

IEEE Guide on Surge Testing [7]). 

Another ambiguity in the VDE 0160 test specification is 

that it might be acceptable to perform a test where the 

voltage waveform is less than the specification, provided 

that 80% of the energy stored in the surge generator 

capacitor is delivered to the EUT. However, there is no 

provision in the test procedure for measuring this energy, 

and it is doubtful that this condition can be achieved with 

a surge generator containing the parallel resistor that is 

necessary to achieve the specified rate of decay (or duration of the tail of the wave) when the EUT offers a high 

impedance. 

Metal-oxide varistors offered by manufacturers include 

ratings of 130 V rms for applications in 120-V systems and 

250 V rms for application in 220-V systems. The motivation for using these varistor ratings is, of course, the 

desire to provide the lowest possible clamping voltage to 

protect sensitive equipment. A paper presented at the 

Ziirich EMC Symposium suggests that premature varistor 

aging may result from this close clamping (see Martzloff 

and Leedy [8]). However, the 130- and 250-V varistor 

ratings are still widely used by equipment manufacturers 

who take the position that they are not afflicted by unacceptable failure rates. Thus, the authors accept that position as reflecting actual field experience and will apply it 

as a criterion for validating or questioning the proposed 

This paper reports the results of modeling the application of a surge test to a family of commonly used varistor 

sizes (14, 20 and 32 mm in diameter). For each varistor 

size, the computations were performed for three levels of 

manufacturing tolerances on the varistor: nominal value, 

- lo%, and + 10%. A varistor with its clamping voltage at 

the maximum acceptable tolerance level (the level shown 

on published I - V curves) will tend to absorb less energy 

than a varistor with a lower clamping voltage because it 

will divert current for a smaller part of the surge. The 

maximum energy deposition in the varistor will occur for a 

varistor having the lowest acceptable clamping voltage 

(typically 20% below the maximum), as indicated by the 

10% tolerance on varistor nominal voltages. Should the 

test generator parameters be at the most severe conditions within its uncertainties (higher peak voltage and 

longer duration than nominal within allowable tolerances), 

the stress on the varistor would be even greater. 

The circuit model used in the computations reported in 

this paper is a simple capacitor-discharge circuit that can 

produce the 10/1000-ps waveform of C62.41 or the 

100/1300-ps waveform of VDE 0160, where each has the 

appropriate selection of the components values. The modeling results, which are discussed in detail below with 

supporting information in the Appendix, indicate that the 

smaller size varistors would not be damaged at the 

"medium exposure" level of C62.41 but would be damaged at the "high exposure" level. The 32-mm varistor 

would easily accept several applications of the "high exposure" level, whereas the 20-mm varistor would have a 

limited life. On the other hand, few varistors will survive 

the VDE 0160 stress. 

Table I presents this information in the form of the 

number of surges that a varistor can survive for the three 

sizes and three tolerance values of varistors and for the 

three type of tests: VDE 0160, C62.41 "high exposure," 

and C62.41 "medium exposure." The results with C62.41 

are in good agreement with anecdotal (unpublished) field 

experience, that is, 14-mm varistors installed at the service 

entrance are often in jeopardy, 20-mm varistors have a 

better chance, and 32-mm varistors are generally successful. Failure rates are not reported formally in the literature, but anecdotal information does circulate. The 

response of industry to the Ziirich paper alerting the 

community to the risk of premature aging caused by 

repeated swells [a] was that 20- and 32-mm varistors do 

not suffer from an unacceptable or alarming failure rate. 

The predicted survival rates of Table I appear to be 

consistent with actual field experience, thus validating the 

stress levels proposed by IEEE C62.41. In contrast, for 

the VDE 0160 stress, the predicted survival rate is so low 

that a conclusion appears inescapable: The VDE 0160 

stress involves an exceptionally high energy level, making 

the application of the test questionable if interpreted as a 

general requirement. The authors do not question the 

scenario leading- to this stress level but do cluestion the - - 

high-energy test standards. -.. - ~ a 
1236 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS. VOL. 28, NO. 6, NOVEMBER / DECEMBER 1992 

TABLE I 

PREDICTED NUMBER OF HIGH-ENERGY SURGES THAT A VARISTOR 

CAN SURVIVE ASA FUNCTION OF SIZE AND CLAMPING 

VOLTAGE TOLERANCE 

Varistor 

Clamping 

Size Voltage VDE 0160 C62.41 C62.41 

mm Tolerance Class 2 High Medium 

none 

none 

none 

none 

none 

1 

none 

1 

5 

none 

1 

8 

1 

3 

20 

8 

80 

800 

80 

3000 

> loh 

500 

8000 

"indefinite" 

20 000 

200 000 

"indefinite" 

IEC proposal to require an across-the-board test at that 

level for all equipment. 

The dramatic effect of the tolerance value on survival 

rate is also apparent. Greater reliability can be achieved if 

users would accept-better yet, request-a slightly higher 

clamping voltage than the lowest clamping voltage offered 

by the manufacturers of varistors and by the manufacturers of packaged suppressors. 

The normal practice in surge testing of low-voltage 

equipment, as described in the IEEE Guide on Surge 

Testing 171, is to specify an open-circuit voltage and a 

short-circuit current to be delivered by the surge generator. With these two parameters specified, the surge generator is considered to be defined for any test involving a 

specimen of high impedance (typically insulation) or low 

impedance (typically a surge diverter). For the unidirectional surges of 10/1000 and 100/1300 ps, a simple 

four-component model circuit can produce these waveforms. An actual surge generator, of course, requires 

careful attention to avoid problems of parasitic 

impedances, but the simple circuit model of Fig. 1 can 

deliver the required waveforms, as shown in Fig. 2 for the 

case of the nominal C62.41 10/1000-ps waveform. 

In the specification of that waveform, the tolerances 

allowed by C62.41 recognize the fact that the open-circuit 

voltage will inescapably have a longer duration but shorter 

rise time than the short-circuit current. Because the 

high-energy aspect of this test makes the current waveform the most significant parameter, the values of the 

components in the model were selected to most closely 

approximate the nominal 10/1000 ws for the short-circuit 

current while allowing the open-circuit voltage to go to 

the longest duration permitted by the tolerances. For the 

VDE 0160 model, the values of the components were 

selected to comply with the 6000-pF requirement while 

producing the specified open-circuit voltage. 

In predicting varistor failure rates, the model can take 

into consideration the possible combinations of manufacturing tolerances on the varistors and the uncertainties of 

the test (which is something that is more difficult to do by 

Fig. 1. Four-component circuit for 10/1000- and 100/1300-ps surge 

modeling. 

0-0 

0 1 2 

TIME (ms) 

Fig. 2. Open-circuit voltage V and short-circuit current I produced by 

circuit model with parameters set for the C62.41 10/1000-ps waveform. 

tests on random samples). In the simple computations 

reported here, three cases have been computed with the 

varistor at the midpoint and the two extremes of its 

manufacturing tolerance. The surge generator parameters 

were set to produce the nominal current waveform in 

order to make a midrange rather than a worst-case prediction. The conclusions on survival rates and validation 

of the proposed tests presented above would not be dramatically affected if the surge generator parameter tolerances were included in the computation. 

The component values of the circuit shown in Fig. 1 

may be selected to generate the desired waveforms of the 

various standards. The selection method is described below. In order to determine the response of the circuit with 

the nonlinear varistor, numerical techniques are used as 

shown in the second step below. 

In the circuit of Fig. 1, the capacitance C is charged to 

an initial voltage q.. The surge generator has a series 

resistance R, and a parallel resistance R,. A small inductance L is tuned to provide the specified rise time. This 

simple LRC circuit is described by a characteristic equation 

where R is defined below. The two decay constants are 

The response of the circuit is a "double exponential" 

waveform [9]. 

Using the allowed tolerances of C62.41 for the model, 

the waveshape of the short-circuit current (in which case 

R is R,) was set at 10/1000 ps. For the open-circuit 

voltage (in which case R is R, + R,), the maximum 
FENIMORE AND MARTZLOFF: VALIDATING SURGE TEST STANDARDS BY FIELD EXPERIENCE 

duration allowed by C62.41 is 2000 ps. The decay times, 

which are expressed as full width at half maximum 

(FWHM) for these two waveforms are designated as t, 

and t,, respectively. The effective source impedance is 

defined in C62.41 as the ratio of the peak open-circuit 

voltage Vp to the peak short-circuit current I,. Its value 

Z = %/Ip has the dimension of an impedance. 

Because the time constants are widely separated, the 

determination of the circuit component values from the 

values of t,, t,, Z, and Vp can be simplified to produce 

approximate values. The characteristic decay values A+ 

and A- are given by 

Applying a logarithm yields 

R tR - R . tR 

L E -- 

log .9 - log .l log 9 ' 

The expressions (1)-(5) uniquely define the characteristics 

of the circuit for given values of the time constants, the 

source impedance, and the peak open-circuit voltage. 

With the parameters of the model test circuit thus 

defined, the solution of the response of the current and 

energy in the varistor is obtained numerically using the 

ordinary differential equation package PLOD [lo]. The 

varistor is presumed to contain an internal series resistance R, and have the I-V relationship 

In particular, for long times t, the short circuit current I,, 

and open-circuit voltage Voc, are given by The first-order system of equations to be solved is given 

by the definition of the capacitor current I and by Ohm's 

law 

At half maximum, one has 

and 

t, = log2. (R, + R,) . C. 

The varistor current I, and I are related by (6) and by 

With a small value of the inductance 

and By exploiting this relationship, a direct numerical solution 

for the varistor current is possible. In addition, the energy 

in the varistor Em is found by integrating 

These relations lead to the four equations: 

The initial charge is given by C . T/,, and the initial current 

and energy in the varistor are zero. The computations 

were performed for the two C62.41 exposure levels and 

for the maximum VDE 0160 stress, as described below. 

MODELING RESULTS 

C62.41-10/1000- ps Stresses 

To evaluate the effects of the test on varistors, a simple 

model of an equivalent circuit of the varistor is connected 

to the terminals of the model generator. The charging 

voltage of the generator is, of course, left unchanged. For 

the range of frequencies involved in these waveforms, the 

only two significant elements of the varistor equivalent 

circuit (Fig. 3) are the pure varistor R,, (I = kV") and 

the series resistance R,,, R, in the model. The parallel 

resistance R,,,, capacitance C, and the series inductance 

The inductance is determined by considering the 10-90% 

rise time tR. The widely separated time constants allow 

the fast component of the current to be estimated by 

at short times t. 
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 28, NO. 6, NOVEMBER / DECEMBER 1992 

(LEAD 

INDUCTANCE1 

Fig. 3. Equivalent circuit of a varistor (Source: [14]). 

L of the complete equivalent circuit can be neglected. 

Three diameters of 130-V rated varistors were considered, 

each with its characteristic clamping at - 10,0, and + 10% 

of the nominal value published by one manufacturer. 

Fig. 4 shows the type of plots obtained from the model 

where the current through the varistor and the cumulative 

energy deposited in the varistor are computed as a function of time. Showing the complete set of results for all 

combinations would require excessive space; a summary 

of the results is presented in the Appendix. In the typical 

example of Fig. 5, three curves show the cumulative 

energy for a 14-mm varistor with nominal rating of 130 V 

rms and three tolerance values - 10,0, and + 10% clamping voltage when exposed to the C62.41 "high exposure" 

stress level. 

VDE 0160 loo/ 1300-ps Stress 

Fig. 6 shows the parameters of the 100/1300-ps surge, 

Class 2 described in the most recent amendment to VDE 

0160 [I11 and in the IEC proposal [3] . The voltage level is 

specified as 2.3 times the peak of the ac power system 

voltage. (The amendment also cites a Class 1 category 

with a level of only 2.0 times the peak of the ac power 

system voltage and a shorter duration). Accepting for the 

moment the premises that led to the specification of this 

test, the authors applied the same circuit model used for 

the IEEE waveforms to produce the specified VDE waveform with an energy storage capacitor having the value 

specified in the latest amendment to VDE 0160. (Earlier 

versions of the VDE 0160 standard suggested a 25 000-pF 

capacitor. In the amendment, this value has been scaled 

down to a range of 700 to 6000 pF, perhaps implying that 

the issue is still unsettled, and thus, the IEC proposal is 

still open to feedback from users.) 

In this case, because the VDE places emphasis on 

maintaining the voltage waveform, the model parameters 

were set to obtain an open-circuit voltage close to the 

100/1300-ps values, with the exception of the resulting 

short-circuit current, for which VDE 0160 does not specify a value. Fig. 7 shows the open-circuit voltage and 

short-circuit current computed by the model. 

The computations were performed for the 250-V rms 

rating because the VDE 0160 does not provide specifications for system voltages of less than 220 V rms. Details of 

the results are presented in the Appendix together with 

the corresponding results from the C62.41 stress levels. 

0 1 2 

TlME (rns) 

Fig. 4. Energy deposition E and current I in a 20-mm varistor with 

nominal clamping characteristic (0% tolerance) during the "High Exposure" 10/1000-fis C62.41 surge. 

50 III~IIIII 

- 10% - 

Rating of l4mm varistor _ 

+lo% - 

0 1 2 

TlME (ms) 

Fig. 5. Energy deposition in 14-mm varistors at - 10, 0, and + 10% 

values of clamping characteristics during a "high exposure" 10/1000-ps 

C62.41 surge. 

Fig. 6. Voltage waveform of the 100/1300-ps surge specified by VDE 

0160 and proposed by IEC (Source: [5]). 

OLO 

TIME (ms) 

Fig. 7. Open-circuit voltage V and short-circuit current I produced by 

model with parameters set to approximate the VDE 0160 voltage waveform. 
FENIMORE AND MARTZLOFF: VALIDATING SURGE TEST STANDARDS BY FIELD EXPERIENCE 

Typical manufacturer specifications [I21 include a joules 

rating for maximum single pulses; however, industry standards (Section 6, IEEE Standard on Varistor Test Specijications [131) raise some questions on the application of such 

a simple criterion. 

The cumulative energy levels for the three varistor sizes 

(each at three tolerance levels) were computed with the 

model for the C62.41 and VDE 0160 stress levels. The 

results are shown in Table 11, together with the typical, 

single-pulse joule rating published for these sizes. By 

using this somewhat oversimplified joule criterion (more 

than 10% change in nominal voltage may occur if joule 

rating is exceeded), it would appear that only the 14- and 

20-mm varistor, for the low values of tolerance, might be 

in jeopardy. 

Using the criterion of "pulse rating" proposed by manufacturers [Ill, [14], where the current peak and duration 

are taken into consideration leads to more detailed and 

reliable conclusions, which also agree with field experience (see Martzloff [15]). 

Therefore, the current peak and its duration (FWHM) 

were also computed for the nine combinations of varistor 

parameters and compared with the "pulse rating" corresponding to the duration and peak in each case. The 

detailed results, which are the basis for the summary of 

Table I, are presented in tabular fashion in the Appendix, 

together with a discussion of the finer points of the 

analysis. 

1) Predictions of the impact of the 100/1300-ps surge 

test proposed by the IEC and based on the VDE 0160 

standard show that the millions of varistors in service 

should experience a greater failure rate than that indicated by available information on actual field failures. 

This inconsistency raises serious questions on the proposed requirement of such a severe test to a wide range of 

equipment. 

Furthermore, the lingering ambiguity in the VDE 0160 

standard (and, consequently, in the IEC proposal) on 

whether to set constant open-circuit voltage or to adjust 

the voltage while the specimen is connected needs to be 

clarified. A constant, specified open-circuit voltage combined with a well-defined source impedance is the generally accepted practice in surge testing. 

2) The energy levels and currents resulting from application of a waveform described in the revised IEEE 

C62.41, on the other hand, range from benign for typical 

large varistors to severe for small varistors. Thus, this set 

of stress levels appears to be more consistent with field 

experience, at least as inferred from available anecdotal 

information. 

3) Although the authors do not question the validity of 

the fuse-blowing scenario, which is the basis for the VDE 

0160 and proposed IEC test, they recommend a critical 

TABLE I1 

SINGLE-PULSE RESULTS AND RATINGS (IN JOULES) 

O/C varistor varistor 

14 -10 1 212 43 

Varistor 

Size Tolermm ance 

NOTES: 

1. Five numbers are printed In bold face in the results columns for two values of tolerances in 

the 14-mm and 20-mm varistors. These vdues exceed the rating of the varistor, and thus would 

indicate a high likelihood oi failure at that stress level 

2 The varistor model postulates the same I = kVm relation for the three ratings, with a series re^ 

nstance that decreases as the hameter oi the varistor increases. The lower serles resistance invites 

a greater current diversion into the varistor in the upturn region oi the I V characteristic, where its 

effect is more noticeable, especially for the VDE 0160 and the lower tolerance case for the varistors 

review of the statistics of the occurrence of fuse blowing, 

the use of varistors with low clamping voltage, and the 

distribution of actual clamping voltage within manufacturing tolerances. They also urge all users to share information on the observed failure rates and thus attain a 

broader perspective on these issues. 

VDE 0160 

Class 2 

250V 

This Appendix provides a summary of the 54 separate 

computations made to determine the current in the varistor resulting from the three high-energy tests discussed in 

the paper. Three varistor sizes were considered (14, 20, 

and 32 mm), and their "pulse rating" obtained from [12] 

and [14]. The 32-mm size has been dropped from the 

current product line of [I21 and might appear obsolete. 

However, it was selected because it has been applied in 

the past [14], and thus, more field experience is available 

for that size than for the 40-mm size, which is the present 

offering. 

The computed results are presented in Table A1 for the 

VDE 0160 Class 2 and the C62.41 "high exposure" and 

"medium exposure7' stresses. In each major section of the 

table, the computed current peak and FWHM are tabulated. Next to these computations, the corresponding current peaks are shown from the "pulse ratings" in [12] or 

[14] for the computed duration and for 1, 10, and 100 

applications of that peak of current pulse. 

The usual description of a unidirectional surge is based 

on the FWHM, and therefore, the computations of the 

current in the varistor were aimed at characterizing this 

description of the current waveform. However, the "pulse 

rating" curves in both [I21 and [I41 are based on an 

"impulse duration" defined as the time from virtual origin 

of the wave and the virtual time to half value. In the case 

of the C62.41, with a front time of 10 ,us and a FWHM of 

1000 ps, the difference between the FWHM and the 

"impulse duration" is negligible. In the case of the IEC 

100/1300-ps waveform, the difference is more significant, 

C62.41 

High 

130 V 

C62.41 

Medlurn 1 130 V 
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 28, NO. 6, NOVEMBER / DECEMBER 1992 

VARISTOR 

DIA Tolermm ance 

TABLE A1 

MODELING RESULTS VERSUS DEVICE RATINGS-CURRENT AND DURATION 

VDE 0160 = 10011300 ~s IEEE C62.41 10/1000 ps "High" IEEE C62.41 10/1000 ps 'Medium" 

2.3 x 220 x 1.4; 6000 YF; 2.3 x 120 x 1.4; 0.25 n; 2.0~ 120 x 1.4; 1.0~; 

250-V varistor 130-V varistor 130-V varistor 

of Pulses in Columns of Pulses in Columns 

'Adjustment of approximately half of the rise time made to account for the difference between the computed FWHM and the "virtual duration" used in manufacturers 

specifications. For the short rise time of the C62.41, the difference IS negligible. 

"When allowable peak current for the wrresponding duration and number of pulses exceeds the rated peak current at that duration, the varistor IS deemed in jeopardy; this 

situation is shown by shading the wrresponding area in the rating columns. The unshaded areas represent "survival" of the varistor through the high-energy stress. 

IMPULSE DURATION -In 

Fig. AI. Typical published family of "pulse rating" curves showing 

amplitude, duration, and number of allowable pulses. 

and therefore, the comparisons of Table A1 include a 

40-ps adjustment in the duration (about half of the rise 

time). 

The peak values of the current shown in the table that 

exceed the "pulse rating" have been identified by shading 

the area in the columns. At a glance, it becomes apparent 

that the survival rate to a VDE 0160 exposure can be 

expected to be extremely low; it will be moderate for the 

C62.41 "high exposure7' and will be at its maximum for 

the C62.41 "medium exposure" stresses. 

ACKNOWLEDGMENT 

The authors acknowledge the contribution of T. Key in 

presenting this paper at the 1990 Annual Meeting of the 

Industry Applications Society when, on short notice, they 

were unable to travel to Seattle. 

REFERENCES 

[I] ANSI/IEEE C62.41-1980, Guide on Surge Voltages in Low-Voltage 

ac Power Circuits. 

[2] ANSI/IEEE C62.41-1991, Recommended Practice on Surge Voltages in Low-Voltage ac Power Circuits. 

IEC Document 77~(~entral Office)4, Oueruiew on Electromagnetic 

Compatibility-Immunity Tests. 

W. Meissen, "uberspannungen in Niederspannungsnetzen," Elektrotechnische Zeitschrift, vol. 104, 1983. 

VDE 0160 Ausriistung von Starkstromanlagen mit elektronischen 

Betriebsmitteln, May 1988. 

F. A. Fisher and F. D. Martzloff, "Transient control levels: A 

proposal for insulation coordination in low-voltage systems," IEEE 

Trans. Power App. Syst., vol. PAS-95, 1976. 

ANSI/IEEE C62.45-1987, Guide on Surge Testing for Equipment 

Connected to Low-Voltage ac Power Circuits. 

F. D. Martzloff and T. E. Leedy, "Selecting varistor clamping 

voltage: Lower is not better!," in Proc. 1989 Zurich EMC Symp. 

A. Greenwood, Electrical Transients in Power Systems. New York: 

Wiley-Interscience, 1971. 

E. Argon, I. L. Chang, G. Gunaratra, D. K. Kahaner, and M. A. 

Reed, "Mathematical software: PLOD," IEEE Micro, vol. 8, no. 4 

pp. 56-61, Aug: 1988. 

VDE 0160A1 Anderung 1 zu DIN VDE 0160/05.88, Apr. 1989. 

Transient Voltage Suppression Decices, Harris Corp, 1990. 

ANSI/IEEE C62.33-1982, IEEE Stand. Test Spec. Varistor SurgeProtectiue Decices. 

Transient Suppression Manual, 5th Ed., General Electric Company, 

1986. 

F. D. Martzloff, "Varistor versus environment: Winning the rematch," IEEE Trans. Power Deli~sety, vol. PWRD-1, no. 2, Apr. 

1986. 

Charles Fenimore (M'88) received the B.S. degree from Union College, Schenectady, NY, in 

1966 and the Ph.D. degree from the University 

of California, Berkeley, in 1978. 

He is an applied mathematician in the Electricity Division of the National Institute of Standards and Technology, Gaithersburg, MD. His 

interests include modeling and computing the 

nonlinear characteristics of high-energy/highvoltage electrical systems. He is the author of 

numerous papers on the breakdown of dielectric 

liquids, high-voltage measurements, and the solution of partial differential equations. 

Dr. Fenimore is a member of the Dielectrics and Electrical Insulation 

Society and the Circuits and Systems Society of the IEEE. 
FENIMORE AND MARTZLOFF: VALIDATING SURGE TEST STANDARDS BY FIELD EXPERIENCE 1241 

Fraqois D. Martzloff (F'83) was born in France, bushings development, power electronics, transient measurements, surge 

where he completed his undergraduate training, protection of electronics, applications of varistors, and electromagnetic 

and came to the United States in the 1950's to interference protection. 

continue his graduate studies. He is contributing to the work of several IEEE committees, in 

In 1985, he joined the staff of the National particular, the revision of ANSI/IEEE C62.41, Guide on Surge Voltages, 

Bureau of Standards (NBS, now NIST) to ex- into the Recommended Practice as discussed in the paper, and an 

pand NBS activities in the field of conducted update of C62.45, Guide on Surge Testing. He is serving as vicechair of 

electromagnetic interference with more recent the IAS IEEE Standards Coordinating Committee on Power Quality. In 

emphasis on power quality and surge protection the IEC Technical Committee 77 on Electromagnetic Compatibility, he 

issues. Prior to joining NBS, his long career at is serving as chair of SC77B (industrial systems) and secretary of WG2B 

General Electric included high-voltage fuses and (installation and mitigation).