standard for 90s

7/28/2019 Standard for 90s

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A Standard for the 90s:

IEEE C62.41 Surges Ahead

Franois D. Martzloff

National Institute of Standards and Technology

Reprinted from Compliance Engineering, Fall 1991

SignificancePart 6: Tutorials, textbooks, and reviews

A trade magazine article publicizing the release by IEEE of the updated version of theseminal IEEE Std 587-1980 (a.k.a C62.41-1980).


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A Standard for the 90s: IEEEC62.41 Surges Ahead

The Recent Upgrade of This Key IEEE Standard Reflects theGrowing Interest Over Power Line SurgesFrancois D. Ma rtzlofi National Institute of Standards and T echnology, (301 )975-2409

th each year that passes, we are relying m ore andmore on electronics in our lives, at home, a t work, for, for defense ..the list is endless. Reliability of these

sed sophistication which often brings about m ore sus -ibility to disturbances. Thus, immunity toic disturbances, including surges in the poweris a must.ners and users perform surge testing to verify that,eed, their equipment is imm une to these surges. The, however, is what level of imm unity m ust beeved, since there are engineering tradeoffs to be m ade,ell as economic considerations. Depe nding on the type(its mission) and the loca tion where it will bea moderate or very high degree of im munity isopriate. To select the appropriate level of surge stressto perform surge testing in a manner that w ill yieldd results while ensuring sa fety, reliable guidance is

rs after its first publication as IEE E Standard 587,Guide on Surge V oltages in Low Voltage AC Power(now A NSYIEEE C62.41- 1980) has undergone atransformation into a Recomm ended Prac tice form at.m a guide proposing two basic w aveform s to representical surges, the documen t now proposes consideration ofard waveforms (the old friends of 1980)by three additiona l waveform s, one a fastt, the others longer, high-energy surges.

History of IEEE C62.41the occurrence of surges that led to theof a small working group in 1966 to develop587 have not changed much, although the electronicaffected by surges as w ell a s thewriting group have undergone considerable

changes. The initial effort to provide guidance fordesigners on su rges in low voltage circuits was started byDave Bodle [ I ] , who persuaded a small group of concernedfellows to seek a hom e in the IEEE S urge-ProtectiveDevices Comm ittee (a body w hich, at the time, was mostlyconcerned with the high voltage world of electric utilities).This pioneer group set out to collect published data onsurge occurrences and even circulated among its members aset of six peak-reading surge counters donated by onesponsor to add to its data base. These were the days beforethe explosive development of disturbance monitors cumgraphics. And so, IEEE 587 was born in 1980, with greatexpectations that it would be a useful guide for designersand users of electrical and electronic equipment.Alas, there were no other documents available to guidethose users in selecting severity levels from the choiceproposed by IEEE 587. In particular, the citation of 6kVbeing a practical upper limit for the occurrence of su rges in120-V circuits was soon misconstrued as implying arequirement that all equipment should be designed towithstand 6kV surges. Product specification sheets beganto state 'meets IEEE 587,' forgetting the difference betweena standard and a guide in E E E parlance. In the meantime,the guide was renumbered ANS IIIEEE C6 2.41, as part of afamily of surge-related documents [2] but the '587' labelhas stuck and is even found in the model names of severalcommercial surge generators.In a first attempt to help users make sensible and correctdecision on surge testing, the IEEE working groupdeveloped a Guide on Surge Testing - ANSVIEEEC62.45-1987. The Guide provided information on how toconduct reliable and sa fe surge tests ("D on't kid yourself,don't kill yourself!"), also pointing out how to interpret theconcep ts of locations categories proposed in the originaldocum ent. How ever, the questions and misuse by somecontinued, so the working group resolved to update theguide.

Compliance Engineering 27


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Normally, IEEE procedures require a 5-year cycle of reaffirmation or revisionbut the challenge of reviewing new data and developing consensus on thissubject stretched the work into ten years, culminating in a RecommendedPractice that was approved early in 1991 and is now available from IEEE. Froma group of 12 people in 1980, the working group grew to 29 by 1990, reflectingthe growing interest about surge protection among users and manufacturers ofelectronic equipment. Reconciling the different points of view from theenlarged group has produced a new document that should receive even betteracceptance than the original 1980 version and, hopefully, result in fewer

Toward a More Useful StandardOne of the first difficulties was to anive at a satisfactory agreement of whatthe word 'surge' means; to some a surge is a temporary increase in the AC line

voltage. hatm mean in^ is now replaced by the term 'swell,' although a sizeablefraction of the engineering community will continue to use the word surge withthat meaning.Next came the issue of noise versus surges (spikes, etc.). How big must avoltage change be to become a surge? That issue was in fact not resolved;

instead, a conceptual figure was included in the document to show therelationships among several parameters (see Figure 1) and thus leave thebottom end of the range open to appropriate interpretation depending on thecircumstances. In addition, the single-value upper limit of voltages proposed inthe 1980 version has been replaced by a table featuring three levels for eachwaveform, according to the location category or the system exposure. Themenu of waveforms proposed in the 1991 version is new and, hopefully,improved, and includes the following types:

The 0.5 ps - 100 kHz Ring Wave, defined in the 1980 version, as standardwaveform.The Combination Wave, 1.2150 ps - 8/20 p , also from 1980, as standardwaveform.The EFT Burst (5150 ns), adopted from IEC 801-4, as additional waveform.A new 10/1000ps Wave, for high-energy stress, as additional waveform.A new 5 kHz Ring Wave, for capacitor switching transient, as additionalwaveform.

The rationale for proposing standard and additional waveforms is rooted in theacceptance of the 1980 waveforms as being representative and useful, whilerecognizing that other waveforms may be encountered in specific cases andshould be recognized. However, the wish for complete representation of allsurges that may occur has to be tempered by economics and engineeringjudgment; hence, the split between standard (recommended) and additional(suggested). Figure 2 shows all five waveforms, and Table 1 presents asummary of the voltage and impedance values. The new waveforms areproposed in response to emerging concerns on surge occurring in specificenvironments. Thus, a brief discussion of these three new waveforms is in order

Additional Waveforms Address Emerging ConcernsThe EFT Burst has been developed by Technical Committee 65 of theInternational Electrotechnical Commission (IEC) to provide a screening test forsusceptibility to the fast transients that can be induced in power as well as data

lines by the multiple re-ignitions occurring during the opening of a circuit by acontactor. While this type of contactor is mostly found in industrialenvironments (the world of TC65), other systems can have the same exposure(at least until the day when all power switching will be done by bounce-free,

Fall 1991Circle Reader S e ~ i c eI7


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for the 90's ...

-free solid-state relays). The catch, how ever, is thattest waveform was proposed to evaluate im mun ity ofment by a test procedure that involves couplin g theinto the equipm ent under test by a capac itance divider:ing capacitor an d the internal capacita nce of thepment under test. It does not mean that the 1-4kVes involved in this test necessarily occur in the p owe rems; what it means is that equ ipme nt that passe s theverity test will most likely b e im mu ne to wha t theworld does to connected equ ipme nt. On e should notsight of this fundam ental aspec t of test sta ndards ; it isible to duplicate all possible occurren ces in o ne test,f a test can be develop ed so that equ ipme nt that p assesest has better field perfo rman ce than equipm ent thatthe test, then the test is a va luable to ol f or reliable11000 p s Wa ve has be en prop osed to provide as to stress equipm ent with high-e nergy s urges, such asthat can occur during m ajor po wer-sy stem faultThe data base for that waveform is som ewhat

range of peak levels and so urce imped ance ised, to be selected accord ing to th e particulars of thetion. As one check f or reality, the energ y depositionility of this waveform is su ch that sma ll varistorsmm diameter or less) in co mm on us e - by the millions -ld only withstand a few ap plications of that surge. Thus,know that such a high-energy su rge does not o ccu r very

. EFFECTI 1 0MICROSECONDS MIL LIS EC ON OS SECONDS

DURATIONOFM MFIGURE 2: Simplified Relationships Between Voltage,Duration, Rate of Chan ge and T heir Effects on Equipment.(Allfigures in this article reprod uced from IEEE StdC62.41-1991, "Recommended Practice on Surge Utilities inLow-Voltage AC P ower Circuits ." Copyright O 1991 bythe Institute of Electrical and Electronics Engineers, Inc.,with the permission o f he IEEE.)

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100 kHz Ring Wave

0 00 10 40 w 10 TtME.pa to o

Combination Wave, Open-Circuit Voltage

DURATION - 2 0 ~ 8

0 10 m 10 " O TIME.p8

Combination Wave. Short-circuit Current

0 00 20 10 a0 TIME. n* 800

Waveform of a pulse in the EFT burst

Waveform for the 1011000 ys current surge

1 0 100 zoo 300

Waveform for 5 kHz Ring Wave

2

Fall 1991


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A Standard for the 90's ...

LocationCategov

AtA2A3

S e mExposure**

LowMediumHighLowMediumHigh

Stendard Waveforms I .4100kHz Combination EFTWng Wave

None30 NoneNone

ditional WaveformslO/lam Ring Wave

W***Q) W*" (0)+one

1.0 11.3 0.25

None1.0 11.3 0.25

None1.0 11051.8 0.5 to 1

None1.0 l t O 51.8 0.5 to 1

C1C2C3

Location Category A is end of "long" branch circuits.LOCatiOn Ca tego ry B is service entrance and 'short" branch circuitsLocatlon Category C is outside of building** System exposu re levels reflects environment factors: lightning activity, power system switching, etc.... Voltage in per-unit of the pe ak of the mains voltage, added a t the peak of the sine wave

Table I : Peak Surge Levels ( V ) and Source Impedances ( Z ) in C62.41-199 1.

LowMediumHigh

The 5 H z Ring W ave has been proposed to represent thesituation encountered near large pow er-factor correctioncapacitor banks. Switch ing transients in the range of 500 to1000 Hz can occur, with high-energy capability. In thiscase, the data base is rich in computer simulations andanecdotal recordings but it is difficult to make an accurateprediction for the general case,because the actual transientsdepend entirely on the local situation. It will be up tomanufacturers and users to agree on a comprom ise betweenconservative overdesign w ishes and eco nom ic viability ofthe design.

Waveform Selection Supports InternationalHarmonization Efforts

NoneNoneNone

The waveform s presented in the new Recomm endeda positive step towardernational standards. Thebination Wave is consistent with the conventional'impulse' typical of IEC surge testing; the ElT Burstan existing IEC Standard.00 kHz R ing Wave, long resisted by som eomm ittees, is beginning to gain a foothold iny. The 10/1000 ps W ave could be anve to the 10011300 ps surge 'under consideration'e IEC T C 77 surge imm unity drafts. (This10011300 ps surge is a varistor killer and, therefore, shouldits original scop e of applicationfaults areby fuses(5)). The 5 kHz Ring W ave has yet to gainonal recognition.To assist designers in making com puter simulations, theended Practice document provides equations fornces are also specified. ThisGuide onbut it was included in the Recomm ended

Practice document until such time as a revised guide onsurge testing will include it (that revision has just beeninitiated, and it will probably take another year before therevision is in print).Last but not least, the new R ecommended Practicedocument has three appendices that offer tutorialdiscussions of the concepts used in the document, provideinformation on the data base, and list almost 100bibliograp hic citations, with brief note s on the contents ofthe papers. Thus, readers of the Recomm ended Practicewill have on hand a short course on how to be prepared todeal with surges in low voltage AC circuits.Francois D. Martzloff is a member of C6 2.41 workinggroup, and has been involved in surge protection issues formore than two decades. He has been at the NationalInstitute of Standards and Technolog y since 19 85 and canbe reached at (3 01 )975-2409.The author acknowledges th ef iv ey ea r effort in consensusbuilding b y the members of the working group and otherinterested parties that made possible the revision of IEEE587 into a Recommended Practice.REFERENCESI. Bodle, D.W. et al. Characterization of the ElectricalEnvironment, University of Toronto Press, 1976.2. C62: Com plete Edition: A bound-book collection of allthe guides and standards on surge protection, publishedperiodically by IEEE .3. Martzloff, F.D. & Leedy, "T.F. Electrical FastTransients: Applications and Limitations," IEEETransactions IA-26, Jan/Feb 1990, pp 151 1594. Feninmore, C, and M artzloff, F.D. "Validating SurgeTests by Field Experience: High-Energy Tests andVaristor Performance." Conference Record, IEEE 4ASAnnual Meeting, Seattle, 1990.5. Meissen, W. Uberspannungen inNiederspannungsnetzen, Elektrotechnische Zeitschrifr,vol. 104, 1983.

6 210 220 2

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NoneNoneNoneNone1.0 1

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standard for 90s

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