COORDINATION OF CASCADES 

Compiled by Fr-ois D. Martzloff 

September 1992 
FOREWORD 

In view of the emerging concerns on the likelihood of achieving a successful coordination of cascaded 

surge-protective devices, this bibliography has been compiled to provide as complete information as 

possible to the joint efforts underway within the US National Committee for the IEC, as well as within 

the transnational community, at the level of the Working Groups of cognizant Technical Committees. 

This document is organized in two parts: 

1. List of identified documents with retrieval information. Depending on the outcome of requests 

made to the various pubiishers, hii copies of the documents might be made available to members 

of interested Working Groups. 

2. For each document, a single-page digest showing the author's abstract, the author's conclusions, 

a?;! brief uii~tzti~i-is hiii the ie~i~~ei coiiceiing the iinpilc~iiiumilrppiic'dtiom of the document 

te L5e ~dbjed of cacde c~~idiiizti~ii. 

Udes stated ntherwise, dxtracts er condusims shewn for each paper are verbatim timscripts (iii tot6 

or in part) of those provided by the author(s) of the papers. 

The 'Reviewer's Annotations' have been added to focus on the issue of cascade coordination, and 

represent the reviewer's (Martzloff) ~oint of view. As such, they are subject to discussion or even 

refutation; they were formulated with the objective of stimulating open discussion, not adversarial 

controversy. 

Comments on this bibliography will be welcome, perhaps leading to periodic updates as necessary. One 

possibility might be that annotations contributed by other experts could be included in later issues of this 

bibliography, leading to a shared document of the Joint Working Group. Suggestions for listing 

additional documents are invited. 

NOTE: This September 1992 issue has been prepared for the September, 1992 meeting of IEEE SPD WG 3.4.6 and the October 

1992 Joint Working Group of IEC SC28A. SC37A, TC64, SC77B and TC81. The deadline for printing and distribution made it 

impossible to complete all the annotations; the selection of those citations that are annotated does not reflect a systematic intention 

of ranking papers by order of signif~cance. 

Cascade Bibliography - September 1992 3 
2002 REMARKS 

As stated in the Foreword (on following Page 3), this Annotated Bibliography was compiled in 

1992 in support of a Working Group of the IEEE Surge-Protective Devices Committee engaged 

in the development of an Application Guide on Low-Voltage Surge-Protective Devices, and an 

IEC project about to be launched, involving five Technical Committees or Subcommittees of the 

IEC for developing a “pilot” Technical Report or Standard on the application of low-voltage 

surge protective devices (SPDs), intended in particular to focus on the coordination of cascaded 

SPDs, an issue that was emerging at the time. To the author’s knowledge, only few additional 

papers were published on the subject after 1992, see the file “Citations Part 8” that is included as 

Annex A of this Part 8. 

Both documents IEC and IEEE eventually reached maturity and, ten years later, the IEC has 

published its document, and the IEEE has conducted a ballot on its document. They can be 

obtained from their respective sponsoring organizations: 

IEEE PC62.72-2002 – Guide for the application of surge protective devices for low-voltage 

AC power circuits 

Ballot in progress (December 2002, publication expected mid-2003) 

Abstract: Information is provided to specifiers and users of surge protective devices (SPDs) 

about the application considerations of SPDs associated with power distribution systems 

within North America. This guide applies to SPDs to be connected to the load side of the 

service entrance main over current device of 50 or 60 Hz ac power circuits rated at 100-

1000V rms. The effects and side effects on the presence and operation of SPDs in lowvoltage power distribution systems are described. The coordination of multiple SPDs on the 

same circuit is described.

IEC/TR 62066 (2002-06) – Surge overvoltages and surge protection in low-voltage a.c. 

power systems - General basic information 

Abstract: Presents a general overview on the different kinds of surge overvoltages that can 

occur on low-voltage installations. Typical surge magnitude and duration as well as frequency 

of occurrence are described. Information on overvoltages resulting from interactions between 

power system and communications system is also provided. Additionally, general guidelines 

are given concerning surge protection means and systems on the basis of availability and risk 

considerations, including interactions and the need for coordination and consideration of 

temporary overvoltages in the selection of surge-protective devices. 

1992 ACKNOWLEDGMENT

Only the cooperation of many authors who made available hard copies of their papers, or of their 

colleagues’ papers, made this compilation possible. Their help in this venture has been essential. 

My hope is that in providing this review, I have not misrepresented their ideas. If I did, I take 

full responsibility for an unintentional error and offer my apologies. 
ALPHABETICAL - CHRONOLOGICAL LISTING OF DOCUMENTS 

ANSIIIEEE C62.41-1991 - Recommended Practice on Surge Voltages in Low-Voltage AC Power Circuits. 

ANSI C84.1-1989 - American National Standard for electric Power Systems and Equipment - Voltage Ratings (60 Ua.4.. I XACI b4J. 

Anderson, L.M. and Bowes, K.B. - The Effects of Power-Line Disturbances on Consumer Electronic Equipment. 

ZEEE Transactions PKW-5, No.2, April 1990, pp 1062-1065. 

Benda, S. - Inte$erence-free Electronics - Design and Applications. Chartwell-Bratt Ltd., Bromley, U.K., 199 1. 

Bird, A.O. - The Effects of Installation Practices on the Performance of Transient Voltage Surge Suppressors. 

Proceedings, Forum on Surge Protection Application, NISlTR-4657, August 1991, pp 105-116. 

Corbett, M.P. and Wolff, B.I. - Performance of MOV Suppressors in Low-Voltage AC Circuits. Proceedings, 

Forum on Surge Protection Application, NISTlR-4657, August 1991, pp 43-50. 

Crouch, K.E and Martzloff, F.D. - Lightning Protection of Residential AC Wiring. Declassified Memo Report 

MOR-78-095, GE Company, 1978. (Available from FD Martzloff) 

Davidson, R. - Suppression Voltage ratings on UL Listed Transient Voltage Suppressors. Proceedings. Forum on 

Surge Protection Application, NISlTR-4657, August 1991, pp 89-92. 

Diigaii, R.C. aid Sdt, S.D. - Low-VoitageSide Current-Surge Phenomena in Singie-Phase Distribution 

Traasfo-mer System. _?reprint TLn 553-2, 1EEE T&n Ce::fc"rc"xcc", 1986. 

Dugan, R.C., Kershaw, S.S., and Smith, S.D. - Protecting Distribution Transformers from Low-Side Current 

Surges. Preprint 7D 401-1 PWW, IEEE T&D Conference, 1989. 

Dugan, R.C. - Conduction of Lightning Stroke Currents From the Utility System to Load Devices. Conference 

Proceedings, Power Quality, October 1989. 

Dugan, R.C., Goedde, G., and Henry, C. - Conduction of Lightning Stroke Currents From the Utility System to 

Load Devices. Conference Proceedings, Power Quality For End-Use Applications, March 1990. 

Dugan, R.C. - Low-Side Surges: Answers to Common Questions. Cooper Power Systems Bulletin SESWOl, April 

1992. 

Goedde, G.L., Dugan, R.C., and Rowe, L.D. - Full Scale Lightning Surge Tests of Distribution Transformers and 

Secondary Systems. (Place of publication unknown) 

Goedde, G.L., Marz, M.B., and Henry, D.C. - Coordinating Lightning Stroke Protection From the Utility System 

to had Devices. Proceedings, Second internationai Power Quuiityi~SD Conference, October 1990, Philadelphia. 

Hairabedian, B. - A survey of Power Line Disturbances at Typical IBM Computer Installations in the U.S. for the 

Period 1988-1992. Document Number 7l? 21.1507, International Business Machines Corporation, Kingston NY, 

June 1992. 

Hasse, P., Wiesiger, I., and Zischank, W. - Isolations-koordination in Niederspannungsanlagen auch bei 

Blitzeinschlagen. Electrotech. Zeitschr~jl, Jan 1989, pp 64-66. (In German; English translation available from FD 

Martzloff) 

Hasse, P. - Overvoltage Protection of low-Voltage Systems. IEE Power Series, Peter Peregrinus Ltd. London, 

1992. (Original German edition in 1987) Available in the U.S. from IEEE. 

Hostfet, O.T. et al. - Coordination of surge protective devices in power supply systems: Needs for secondary 

protection. Proceedings, International Conference on Lightning Protection, Berlin, September 1992. 
Iiuse, j.3. - Contributions to the revision of Doc 28A(Sec)47, internal document, ZEC!SC28A WWI, 1988. 

IEC 28A(USA/Las Vegas)09 - (Draft) Explanation for over-voltage categories. December 1984, Amended Aug

1987. 

IEC 28A(Norway) - Comments of the Nonoegian National Committee on Document 28A(Secretariat)47. 

IEC 37AIWG3(Convenor) 1 - DraB Application Guide, 1992. 

IEC 64lWG3 138A - Explanation of interfaces for overvoltage categories. Supplement to Appendix B of Repon 6

November 1990. 

IEC 77(C0) 1 18 Clmsification of Electromagnetic Environments 

Lagergren, E.S., Martzloff, F.D., Parker, M.E., and Schiller, S.B. - The effect of repetitive swells on metal-ox

varistors. Proceedings, PQA 92 Conference, September 1992, pp xx-xx. 

Lai, J.S. - Performance Criteria for Cascading Surge-Protective Devices. Proceedings, Open Forum on Su

Protection Application, NZSllR-4654, August 1991, pp 147-160. 

Lat, M.V. - Determining Temporary Overvoltage Levels for Application of Metal-Oxide Surge Arresters 

Multigrounded Distribution Systems. ZEEE Transactions PMRD-5, April 1990, pp 936-946. 

Martzloff, F.D. and Crouch, K.E. - Coordination de la protection contre les surtensions dam les dseaux ba

tension rbidentiels. Proceedings, I978 IEEE Canadian Conference on Communications and Power, pp 451-4

(In French; English translation available from FD Martzloff) 

Martzloff, F.D. - Coordination of Surge Protectors in Low-Voltage AC Power Circuits. IEEE Transacti

PAS-99, January/February 1980, pp 129-133. 

Martzloff, F.D. - Coupling, Propagation, and Side Effects of Surges in an Industrial Building Wiring System. IE

Transactions L4-26, MarchIApril 1990, pp. 193-203. 

Martzloff, F.D. and Lai, J.S. - Cascading Surge-Protective Devices: Coordination versus the IEC 664 Stairc

Proceedings, PQA 91 Conference, pp 191-198. 

Martzloff, F.D. - On the Propagation of Old and New Surges. Proceedings, Open Forum on Surge Protect

Application, NZSTIR-4654, August 199 1, pp 19-28. 

Martzloff, F.D. and Lai, J.S. - Cascading surge-protective devices: Options for effective implementatio

Proceedings, PQA 92 Conference, September 1992, pp xx-xx. 

Man, M.B. and Mendis, S.R. - Protecting Load Devices from the Effects of Low-Side Surges. Proceedin

ZEEE/ZCPS Conference, May 1992 

 eyer, J.P. - Parafoudres en Cascade. Proceedings, UTE Workshop on Surge Arresters, Paris, March 20, 1

ji French). 

Rousseau, A., Lafon, G., and Malpise, F. - Les parafoudres face aux norms. Proceedings, CEM 92, 

International Workshop on EMC, Lyon-Ecully, France, June 1992. (In French) 

Scuka, V. - Application of modern surge suppressors in low-voltage power installation networh. Institute for H

Voltage Research, Uppsala University, UURIE:250-86, 1986. 

Cascade Bibliography - September 1992 
Scuica, V. - EM1 Coniroi in 'Low-Vdiage Power insiaiiaiions. fioceetiing~, i987Eh'CZurich Symposium, pp 429- 

434. 

Smith, S.B. and Standler, R.B. - The Effects of Surges on Electronic Appliances. ZEEE Transactions PWW-7, 

No.3, July 1992, pp 1275-1282. 

Standler, R.B. -Protection of Electronic Circuitsfrom Overvoltages. Wiley-Interscience, New York, 434 pp, 1992. 

Standler, R.B. - Coordination of Surge Arresters and Suppressors for Use on Low-Voltage Mains. Proceedings. 

1991 Zurich EMC Symposium, pp 5 17-524. 

Standler, R.B. - Calculations of Lightning Surge Currents Inside Buildings. Proceedings, ZEEE International EMC 

Symposium, August 1992, pp 195-199. 

Stringfellow, M.F. and Stonely, B.T. - Coordination of Surge Suppressors in Low-Val-e AC Power Circuits. 

Proceedings. Forum on Surge Protection Application. NZS21R-4657, August 199 1, PP - - 133- 138. 

Stringfellow, M.F. - Fire Hazard of Surge Suppressors. Proceedings, Power Quality Conference, Anaheim Ca, 

September 1992. 

Cascade Bibliography - September 1992 
Anderson, L.M. and Mwes, K.B. - The Effects of Power-Line Disturbances on Consum

Electronic Equipment. IEEE Transactions PJGW-5, No. 2, April 1990, pp 1062- 1065. 

AUTHOR'S ABSTRACT 

This study quantified the effects of simulated power 

system transients, voltage fluctuations and momentary 

interruptions on household electronic equipment. 

Nondestructive testing was performed to determine 

the applicability of the CBEMA and IEEE 

susceptibility curves to consumer electronic 

equipment. As a results, graphs were developed 

which illustrate these effects. 

AUTHOR'S CONCLUSIONS 

(ExcerpW 

Overvoltageltransient testing in this study failed 

demonstrate any adverse effect on the equipm

tested. [...I Any cumulative effects due 

accelemted aging (loss of life) from eit

undervoltages or overvoltages were not considered 

this study. [authors' italics] 

The researchers' objectives were primarily nondestructive tests ~rnderv~lkge effects. For tpas:mt &&kg, 

ANSIIIEEE C62.41 tests were not used, "due to the destructive nature of the pulses." nor was any reference m

to the IEEE Guide on surge testing. However, 'High-Energy' tests were applied with pulses of 100 and 300 

width and 1000 V peak (presumably an open circuit voltage as the authors state "The equipment used was capa

of supplying 1000 V peak impulses on the supply for the equipment tested ... ") There is no statement on a b

filter nor on the generator source impedance. Thus, the surge effectively applied to the test specimen termi

might have been less than 1000 V. 

From the report that no adverse effects were found, one may draw a tentative conclusion (subject to revisiting 

effects of loading the generator by the supply impedance and its internal impedance), parallel to that of Smit

Standler (1992), that appliances have more immunity than what seems to be postulated in offering Transient Volt

Surge Suppressors clamping at 330 or 400 V levels. 

Cascade Bibliography - September 1 992 
ANWiEEE 262.41-199i - Recommended Practice on Surge Witages in Low- Wtage AC Power 

Circuits. 

IEEE ABSTRACT 

A practical basis is provided for the selection of voltage and current tests to be applied in evaluating the surge 

withstand capability of equipment connected to utility power circuits, primarily in residential, commercial, and light 

industrial applications. The recommended practice covers the origins of surge voltages, rate of occurrence and 

voltage levels in unprotected circuits, waveshapes of representative surge voltages, energy, and source impedance. 

Three location categories are defined according to their location relative to the building service entrance. For each 

category, representative waveforms of surge voltages and surge currents are described, organized in two 

recommended "standard waveforms" and three suggested "additional wavefonns." 

This is an update of ANSI/IEEE C62.4 1-1980 (previously known as IEEE Standard 587). It provides a description 

of surge sources and presents a database of previous surveys that have evaluated surge voltages in low voltage ac 

power circuits. Methods for design and protection of electronic circuits to achieve surge immunity are presented. 

This standard also includes information on probability of surges occurring and presents a new test waveform with 

a shorter wave front for testing of electronic equipment. 

A surge voltage is regarded as having its origin in either a lightning or switching transient, and is therefore a high 

frequency phenomena. A graph based on test data is provided which shows the rate of surge occurrence based on 

surge crest voltage at unprotected locations. On an unprotected circuit, the surge voltage is limited by the sparkover 

of clearances, which for 1201240 volt systems is given as 6 kV or less. This level is considered as a cutoff level 

for transients on indoor power systems. The two recommended "standard waveforms" are the 100 Hz Ring wave 

and the 1-2/50 - 8/20 Combination Wave. The three suggested "additional waveforms" are the 5/50 ns EFT burst, 

the 10/1000 voltage/current wave, and the 5 kHz Ring Wave. 

While providing a description of the surge environment that can be expected, the document 

emphasizes that it should not be construed as a surge-withstand requirement standard. 

Cascade Bibliography - September 1992 
ANSI C84.14989 - American National Standard for electric Power Systems and Equipmen

Voltage Ratings (60 Hertz). 

1. Scope and Purpose 

1.1 Scope. This standard establishes nominal voltage 

ratings and operating tolerances for 60-hertz electric 

power systems above 100 volts and through 230 

kilovolts. It also makes recommendations to other 

standardizing groups with respect to voltage ratings 

for equipment used on power systems and for 

utilization devices co~ected to such systems. 

1.2 Purpose 

The purposes of this standard are: 

(1) To promote a better understanding of the 

voltages that are associated with power 

systems and utilization equipment in order to 

achieve overall practical and economical 

design and operation 

(2) To establish uniform nomenclature in 

field of voltages 

(3) To promote standardization of nomi

system voltages and ranges of volt

variations for operating systems 

(4) To promote standardization of equipm

voltage ratings and tolerances 

(5) To promote coordination of reiationsh

L,..,~~.. -,w-u ....-&A- JJDGILI and equipment vuit

ratings and tolerances 

(6) To provide a guide for future developm

and design of equipment in order to achie

the best possible conformance with the ne

of the users 

(7) To provide a guide, with respect to cho

of voltages, for new power syst

undertakings and for changes in old one

nThe d_mmment is ess.~t;d!y 2 stegdy-st.te v&qe qmif;&~~. 1:dm no: pvi& ~foruiioij the mpitu

or duration of abnormal temporary overvoltages, but only states that corrective action must be taken promptly w

the system voltage exceeds the specified upper limit. 

The group that developed this standard is currently considering developing a document that would address the is

of temprary overvoltages. 

Cascade Bibliography - September 1992 
Benda, S. - Zntegerence-pee electronics. Chartwell Bratt Ltd. Bromley BR1 2NE, U.K. 

Subtitle of the book: 

Design and applications. 

The design and use of interference-free systems and printed circuit boards 

within industrial process automation and the utilities industry. 

Excerpts from back cover abstract: 

Interference-free electronics teaches how to design circuit boards, electronic devices and systems with high immunity 

to interference. The book also deals with process adaptation, communication and power supply with immunity to 

hti:eifeii:eiia. . . . . 

Chapter headings: 

Introduction 

Interference sources, coupling factors 

Grounding, earthing and screening 

Standards for interference immunity tests 

Supply system 

Protecting components against transients and surges 

Signal transmission . . . Field installation guidelines 

Apparatus design 

The design of interference-proof circuit boards . . . Communications 

Fvfi@:icn ... f'& 

ktIStigaGSE &S9Lrbmces . . . Tr=&!&=t;@ 

&n&~ion 

Reviewer's annotations 

The emphasis of the book is on equipment design rather than power systems and installation practices. 

A limited scanning of the book and its index does not reveal the issue of cascade coordination as a topic. 

Cascade Bibliography - September 1992 
Bird, A.O. - The Effects of Installation Practices on the Performance of Transient Voltage Sur

Suppressors. Proceedings, Forum on Surge Protection Application, NISTIR-4657, August 199 

pp 105-116. 

AUTHOR'S ABSTRACT AUTHOR'S CONCLUSIONS 

Packaged surge protection devices are generally 

installed on low voltage AC systems to provide a 

controlled transient environment, as opposed to an 

uncontrolled environment relying upon the 

unpredictable sparkover of some clearance within the 

distribution system. 

The objective of effective surge protection devices or 

systems is to controi transient overvoitages to a ievei L_l---. rnlow the ~diierdbiiiiy to damage and, in many pa.2n.2 +ha -.",.*..+;I.:1:+., +rr :-.&a2 -^^A^ ^C I--.---:- -, -" --p~l~iry rv WLGLA&AGUW ul Slarruu~: 

equipment. 

The achievement of this objective is dependent on the 

characteristics of the protection device, the length and 

configuration of co~ecting leads used, fusing and the 

coordination of protection devices. 

The effects of differing installation techniques are 

investigated and, where possible, the optimum 

solution is proposed. 

Correctly specified, correctly installed, transie

voltage surge suppression can significantly reduce t

incidence of disruption and damage of electron

equipment due to transient surge voltages. 

The objective in specifying protection is to insure th

transient overvoltages are controlled to a level belo

the Equipment Transient Design Level, achieving 

reasonable safety margin. 

practi@a, A~S &@iive can oniy if t

performance of the surge protection device is n

compromise.. by poor installation practice a

inappropriate device coordination. 

REVIEWER'S ANNOTATIONS 

Cascade Bibliography - September 1992 
mr- Corbett, my. and 'Noiff, E.1. - Performance oI'MOV Suppressors in Low-Voitage AC Circuits. 

Proceedings, Fonun on Surge Protection Application, NZSTZR-4657, August 1991, pp 43-50. 

AUTHORS' ABSTRACT AUTHORS' CONCLUSIONS 

Surge voltages on indoor ac power distribution lines 

can arise from both external and internal sources. 

Service entrance arresters help to reduce the effects 

of lightning but do not eliminate a need for 

suppressors at the location of sensitive equipment. 

Protective characteristics are improved by cascaded 

stages of arresters and suppressors regardless of the 

strategy used for coordination. 

The surge-protective characteristics of MOVs are 

used to maximum advantage when surge arrester 

MOVs are combined with suppressor MOVs at 

distribution panels or branch locations serving 

sensitive equipment. This plan results in two or 

more stages of protection against lightning surges and 

achieves significantly lower clamping voltages. 

,--..-a:--.:-- -c ---&--A:-.- >--.:--- : 1 ..-- c.wIumauuu UI SUI~G-~IULZX;LIVG uev1cxs 111vu1ves 

mnnv fact-- t-LAml n-A M~-III;I. --A ' -J IOICVIU, -UW .YIU LZUUWILUC, QYU iS 8 

cnq&x g~&jmg the prw&= cf the MQV I=T. 

However, the presence of two stages d0e.s allow 

grader flexibility in grader of voltage ratings. 

Because protective levels are lower with two stages, 

a downward auction on ratings can be avoided. For 

the best suppression, MOVs are used in L-N, L-G, 

and N-G modes where consistent with other 

requirements 

REVIEWER'S ANNOTATIONS 

Cascade Bibliography - September 1992 
Crouch, K.E and Martzloff, F. D. - Lightning Protection of Residential AC Wiring. Declassifi

Memo Report MOR-78-095, GE Company, 1978. (Available from FD Martzloff) 

AUTHORS' ABSTRACT AUTHOR'S CONCLUSIONS 

New transient suppressors using metal oxide varistors Installation of a varistor protector at the load cent

offer improved protection of appliances and consumer if incorporated with very short leads, effectiv

electronics against overvoltages. This improvement, protects all of the wiring in the house. However, t

however, could be at the risk of imposing excessive installation is difficult to implement in exist

duty on the suppressor in case of a ve'ry severe systems and will continue to be difficult unti

lightning stroke near the house where these package is developed to allow comection to the lo

suppressors are installed. center bus bars with very short leads. 

A simulated house wi~g system (actual wire, not Until =I& a3 --kg=! p&ge is -&&& for z

computer simulation) was subjected to three levels of systems, a coordinated protection .scheme 

lightning currents injected into the ground wires, with implemented, as a retrofit, that would still prov

various combinations of suppressors installed alone or reliable protection for millions of sensitive applian

in a coordinated combination. in existing systems. 

Test results show that an effective and safe Thus, a coordinated protection scheme is technica

combination of devices can be specified for full feasible. The cost should be acceptable to do

protection of the loads in the house. yourself homeowners, although it might be 

deterrent to those owners who have to call in 

electrician to install a protector at the load cent

Based on increasing awareness in the technical a

regulatory agencies community of overvolt

protection, the incorporation of protection to lo

centers offers the best approach to new installatio

REVIEWER'S ANNOTATIONS 

The paper shows the effect of larze currents flowing in the nwtrailgr~unding cnnd~t_cr af service &q 

building, and explores options for placing an arrester at the service entrance or at the end of branch circuits, 

both. 

The many oscillograms reproduced in the paper also show how a unidirectional stimulation (8120 ps current flow

only in the grounding conductors) result in oscillatory transients in the differential mode. 

Cascade Bibliography - September 1992 
Davidson, R. - Suppression Voltage ratings on UL Listed Transient Voltage Suppressors. 

Proceedings, Fonun on Surge Protection Application, NZSTIR-4657, August 1991, pp 89-92. 

AUTHOR'S ABSTRACT AUTHOR'S CONCLUSIONS 

Some manufacturers and purchasers of UL Listed 

Transient Voltage Surge Suppressors (TVSS) have 

expressed concern to UL about certain types of 

advertising claims that have been made with respect 

to the suppression voltage ratings marked on UL 

Listed TVSS. 

Examples are claims that the minimum 330 volt 

suppression rating in UL's Standard for Transient 

Voltage Surge Suppressors, UL 1449, is "the best UL 

rating" or that 330 voits affords "the most protection 

possibie" or ihat "ihe iower the suppression rating the 

better the TVSS product (or protection it provides)". 

The purpose of this brief paper is to clarify the 

meaning and limitations of the suppression voltage 

ratings that are marked on UL Listed TVSS products 

in association with the UL Listed Mark. 

The suppression voltage ratings marked on UL Listed 

TVSS provides the purchaser with independently 

generated information on how a TVSS -performs 

when subjected to a specified impulse surge. On the 

other hand, the ability of a TVSS to protect 

connected equipment from both upset and damage 

may depend on a number of factors including 

knowledge of both the susceptibility and vulnerability 

of the particular equipment. 

To the extent that the above mentioned factors are 

'mown, the suppression voitage raiings on 'u'i Listed 

TVSS can contribute useful information to an overall 

assessment of the adequacy of surge protection. 

When these factors are not known, claims that one 

TVSS provides better protection than another, solely 

on the basis of the UN 1449 suppression voltage 

rating, may be misleading. 

REVIEWER'S ANNOTATIONS 

The paper provides the position of UL concerning the issue or clamping voltage selection for TVSSs. 

Cascade Bibliography - September 1992 
Dugan, R.C. and Smith, S.D. - Low-Voltage-Side Current-Surge Phenomena in Single-Pha

Distribution Transformer Systems. Preprint T&D 553-2, IEEE T&D Conference, 1986. 

AUTHORS' ABSTRACT 

Lightning current surges entering the secondary 

windings of distribution transformers can be a cause 

of transformer failure. Proposed solutions have 

included interlacing the secondary windings and 

applying low-voltage arresters. Tests have been 

proposed to verify the ability of a transformer to 

withstand these surges. This paper shows that the 

amount of current varies significantly for different 

sizs and &signs of transformers, iod, and 

&la* It is a:w sho-m &.& he entire 

w9&q cia~~it & ti=& --.a*-- Jy JKU. 

Mastes &!en to protect the t~asf~r~~er generd!y 

increase the surge voltage stress on the load 

equipment. The source of the problem is the voltage 

drop along the secondary cable. Minimizing that 

voltage can effectively alleviate the problem at both 

the transformer and the load. These facts must be 

taken into consideration before developing 

transformer test standards to address the low-voltageside current surge problem. 

AUTHORS' CONCLUSIONS 

(Excerpts) 

Concerning proposed test levels for low-voltage 

current surges in distribution transformers, it wouid 

appr b be kappropriaie to specify a single current 

me&& fsr a! tmsf~.rmeis. TL,e aiiieit of siirge 

cu~f?nt && psses thmgh tlrp fmsf~mer V&+S 

significantly with the design and k VA rating of the 

transformer. The current that flows is not a constant, 

but is determined, primarily, by the net differential 

mode voltage drop across the secondary cable and, 

also, by the impedances of the transformer, cable, 

load, and ground. 

Smaller-sized transformers with interlaced 

secondaries of low-voltage arresters will typically 

pass twice as much surge current as conventional, 

non-interlaced designs of the same rating. 

The 10-kVA transformer described in this pap

would typically see less than 7 percent of th

lightning stroke current in each half of the seconda

winding (14 percent total in the secondary) when th

secondary windings are not interlaced. In th

interlaced connection, the same transformer would b

expected to see nearly 16 percent of the lightnin

stroke current in each half (33 percent total). Th

latter figure is the theoretical limiting value assumin

equal division of the stroke current in the seconda

cable and between pole and house grounds. 

25-Yv'A and 50-kVA non-interiaced transformers w

dlow more airrent to fiow than the iO-YVA no

;at&z!& tmfGFuei I.------- -uac Of AL UCP -: i

impedances. In fact, the impedance of a 50-kV

transformer is relatively insignificant when compare

to the cable impedance and the surge current in th

transformer approaches the theoretical limit. Th

fact, in combination with different distributions of th

turns in larger kVA transformers may explain wh

researchers have reported that transformers that a

50-kVA or larger, are essentially immune to failu

from low-voltage-side current surge phenomen

Another factor might be that these transformers a

generally connected to more than one secondary loa

which our studies indicate would decrease th

voltages induced within the transformers. 

The system consisting of the distribution transform

and ioad has a complex response to lightning surg

and very sensitive to changes in the characteristics 

.L - -- -- --Iur: mmpunenrs of the system. Changes io th

*-"& rz-lOl -aLUG1 wur -....-A* I.- - &id -- .-.L --- wiuuut d

considering the effects of the changes on the rest 

the system. For example, protecting the transform

insulation by interlacing the transformer secondari

or by applying low-voltage arresters w

approximately double the voltage stress on the lo

for the smaller transformer sizes. The only soluti

found that minimizes the problem in all areas of t

system is to use shielded secondary cable that h

adequate mutual coupling between the neutral an

phase conductors. This minigtizes the surge curren

by reducing the net differential voltage induced by t

lightning surge currents flowing in the cable neutra

- - - - - - - REVIEWER'S ANNOTATIONS 

Cascade Bibliography - September 1992 
Dugan, R.C., Kershaw, S.S., and Smith, S.D. - Protecting Distribution Transformers from 

Low-Side Current Surges. Preprint TD 401-1 PWW, ZEEE T&D Conference, 1989. 

AUTHORS' ABSTRACT 

Abstract - In geographical regions where severe 

lightning is accompanied by poor pole grounds, the 

secondary distribution system is subjected to high 

voltage surges due to lightning current seeking 

alternate ground paths through the low-voltage 

circuits. Complete protection of the low-voltage 

circuits must be coordinated because applying surge 

protection at one location will frequently increase the 

stress at other iocations. Distribution transformers 

s.&ja.& to ~& &.ti- .ke pi;-y. r*h&ag 

!ayer&&yer *&L!aGcE tc &&LcGca fie= +Ae ------ cmnndary side. n-e htem4 v~!bge di~&&~~~~ 

such that primary arresters are generally ineffective 

in controlling this stress. Interlacing the secondary 

windings will reduce the primary winding stress when 

the surge current is nearly balanced in the two 

secondary winding halves, but is ineffective when the 

surge current is not balanced. Either MOV or 

gapped arresters across the secondary terminals 

provide more complete protection for the 

transformer. Transformers with interlaced secondaries 

and those with low-voltage arresters can place greater 

stress on the load insulation. Arresters applied at the 

service entrance do not protect all insulation 

throughout the structure, but do not appear to worsen 

any' insulation stress. Arresters applied at the 

transformer or at the service entrance should have 

REVIEWER'S ANNOTATIONS 

AUTHORS' CONCLUSIONS 

In areas where low-side current surges are a problem, 

all distribution transformers, with or without 

interlaced secondaries, are susceptible to failure from 

low-side current surges. Interlaced secondaries are 

effective in reducing the transformer failures from 

secondary surges, but are still susceptible to surges 

that are not balanced. Low-voltage arresters can 

significantly reduce the failure rate of non-interlaced 

transformers and offer protection against both L-l---- > --> ---L-l---- > mauwa~ auu u~~u;ruaur;cu suryca. 

BQ~& MQV-typ zv&=n ad a siqn!e ggp=pJ 

arrester are effective in protecting transformers. It 

would appear from the literature that MOV arresters 

would be required for protecting loads. 

Arresters applied in the pole environment should have 

a current discharge capability of at least half of that 

for a standard distribution class arrester. Arresters 

applied at the service entrance should have the same 

capability because they see the same currents. The 

minimum conduction level should be high enough to 

coordinate with the primary arrester. 

Because the surge originates from a surge voltage 

drop in the service drop cable, clamping or limiting 

the voltage at one end increases the voltage at the 

other end. iiis impiies that the service entrance 

o-ug bt t" L& pr"Lp&&- t" cmrd&ate -w& .he t-"cFn-~- ..-t-+;n.. n;r nrrartar rhA..lA & .'QYIIw.LY-. p"CL.CIIwY. *-a Q11-1-I aYwU'u 

cimilar in mtina tn the tmncfnrmer srr~cter and hav~ --"Y.-. ... ----e .- -- *..-*--. -..---. -- ..-- . a discharge voltage of less than 2 k V to coordinate 

with load insulation. This arrester seems to be only 

partly effective in protecting the house load if there 

are other ground paths. However, the addition of a 

service entrance arrester is not likely to worsen surge 

problems within the house such as might occur if the 

transformer is protected without protecting any part 

of the load circuit. 

Cascade Bibliography - September 1992 
Dugan, R.C. - Conduction of Lightning Stroke Currents From the Utility System to Lo

Devices. Conference Proceedings, Power Quality, October 1989. 

AUTHOR'S ABSTRACT 

Recent research into distribution transformer failures 

has suggested that the frequency of lightning surges 

entering loads from the utility system may be higher 

than previously believed. Protective devices must be 

carefully applied to be effective. Multiple grounds, 

which are frequently found in load circuits, can 

defeat protective efforts. This paper describes how 

surges can enter load circuits through utility system 

neuirai paths. Surges may come from oveiheaci and -t ,ITn\ _ uucrgrvunu {UUJ systems dike. Tne surges foiiow 

grsG ..a+%.- :..+.. A- 1 LZ-L 2: )I-- 1116" LUG 10- , UUUL; ugu udkieiiikd 

VQ!QOPC c t&q pw thrqgh ~ms&&d& zb!e. 0-- 

Sensitive appliances should be protected. Appliances 

connected to multiple ground paths should have the 

ground conductors of dl paths bonded at a single 

point of connection. Arrester voltage discharge 

levels and current discharge capacities should be 

coordinated from the utility system all the way to 

load point. 

AUTHOR'S CONCLUSIONS 

One thing that should be obvious from th~s article 

the "ground" is not always at zero potent

especially under lightning surge conditions. Su

currents can be very high and have a high rate 

rise, which develop large voltage in induct

elements as well as resistive elements. The sur

become a problem basically because there 

multiple grounds in the system and the surge curre

flow between them. This can result in insulat

faiiure due to potentid differences between ground

I?;e bsic p:s:iGii iiihcip;e is to dmp voi*ug

and bond all ground conductors at the point 

connection to the power supply. 

Surges can enter the load structure quite easily on 

system neutral conductors. Surge current 

conducted to the neutral nearly every time a uti

primary distribution line is struck by lightni

Because these lines are struck many times 

lightning-prone areas, surges may be entering lo

circuits more frequently than believed. There see

to be little that can be practically done to reduce 

frequency of these surges. In fact, efforts by utili

to protect their own equipment may increase 

magnitude of the surges entering the lo

Therefore, load device protection that is carefu

coordinated with other elements of the system see

prudent. 

REVIEWER'S ANNOTATIONS 

Cascade Bibliography - September 1992 
- 

Dugan, KC., Goedde, G., and Henry, C. - Conduction of Lightning Stroke Currents From the 

Utility System to Load Devices. Conference Proceedings, Power Quality For End-Use 

Applications, March 1990, 

AUTHORS' ABSTRACT 

Recent research into distribution transformer failures 

has suggested that the frequency of lightning surges 

entering loads from the utility system may be higher 

than previously believed. Lightning does not have to 

strike the secondary system directly on order to 

generate spikes in loads. In fact, many spikes are the 

result of lightning currents being conducted on the 

load on the so-called "neutral" or "ground" paths: the 

normai paths designed to conduct these currents. 

pio*~i~."e &"ices mwt he proper raiing and 

,,n,aC..ll.r ,,,l:arl r, La ,EFa,4:.,, nK..I*:-l- 2- ~GLUUJ ayyncu rv UG GL~-LLVG. ~v~usrlyl~ gluuuu~, 

which are frequently found in load circuits, can 

defeat protective efforts. This paper describes how 

surges can enter load circuits through utility system 

neutral paths. 

Surges may come from overhead and underground 

(UD) systems alike. The surges follow ground paths 

into the load, inducing high differential voltages as 

they pass through unshielded cables. Generally, both 

ends of the cables must be protected. Secondary 

arresters in the service drop environment may see as 

much as 113 to 112 of the utility's primary arrester 

discharge current. Arresters in the service entrance 

should have similar current discharge ratings as a 

secondary arrester on a distribution transformer. 

Service entrance arresters offer protection to load 

circuits that do not have other ground paths. 

Sensitive appliances and appiiances connected to . . ,.*--.-..- --.:*I. ---lL-l- --*l.- -L---IJ L ---- LLI~UI~ wlru ulu~r~p~c; y~uuuu paw WXJUMJ nave 

special protection. Arrester voltage discharge levels 

and current discharge capacities should be 

coordinated from the utility system all the way to 

load point. 

AUTHORS' CONCLUSIONS 

One thing that should be obvious from the article is 

the "ground" is not always at zero potential, 

especially under lightning surge conditions. Surge 

currents can be very high and have a high rate of 

rise, which develop large voltage in inductive 

elements as well as resistive elements. The surges 

become a problem basically because there are 

multiple grounds in the system and the surge currents 

flow between them. This can result in insulation 

faiiure due w potentiai differences between grounds. 

The basic protection principle is to clamp voltages 

and bond all ground conductors at the point of 

connection to the power supply. 

Surges can enter the load structure quite easily on the 

system neutral conductors. Surge current is 

conducted to the neutral nearly every time a utility 

primary distribution line is struck by lightning. 

Because these lines are struck many times in 

lightning-prone areas, surges may be entering load 

circuits more frequently than believed. There seems 

to be little that can be practically done to reduce the 

frequency of these surges. In fact, efforts by utilities 

to protect their own equipment may increase the 

magnitude of the surges entering the load. 

Therefore, load device protection that is carefully 

coordinated with other elements of the system seems 

prudent. 

REVIEWER'S ANNOTATIONS 

Cascade Bibliography - September 1992 
Dugan, R.C. - Low-Side Surges: Answers to Common Questions. Cooper Power System

Bulletin SEW, April 1992. 

AUTHOR'S ABSTRACT 

AUTHOR'S CONCLUSIONS 

The power industry is beginning to come to grips 

with the problem of low-side surges, also referred to "It's a Complex Systems Problem" 

as low-side current surges. However, the interjection 

of current may be inappropriate because there are 

voltage issues as well, so we will refer to the 

phenomena generically as "low-side surges. " 

The extent of the problem is very significant to the 

utiiiiies, whether they reaiize it or not. Cooper Sjis'em's rnt Utility Power miib Survey 

(1g)g)G) k&;=b@ b&.& & aLflet ;c yo of dl -uediiis 

1m&stmd t&s pr&!~_m_. o= c="yt;a::;ag :*-~h 

indicates that approximately 50% - 70% of all 

distribution transformer failures in regions with any 

significant lightning are due to low-side surges in one 

way or another. 

REVIEWER'S ANNOTATIONS 

Answers are provided to the following questions: 

What is the origin of the surges ? 

Are interlaced transformers immune to low-side surges ? 

Why protect both sides ? 

.-.. what do iow-side surge voitages iook iike ? 

Ca a service entrance arrester protect the entire house ? 

Cascade Bibliography - September 1992 
Goedde, G.L., Dugan, R.C., and Rowe, L.D. - Full Scale Lightning Surge Tests of Distribution 

Transformers and Secondary Systems. (Place of publication unknown) 

AUTHORS' ABSTRACT 

Low-side surges are known to cause failures of 

distribution transformers. They also subject load 

devices to overvoltages. A full-scale model of a 

residential service has been set up in a laboratory and 

subjected to impulses approximating lightning strokes. 

The tests were made to determine the impulse 

characteristics of the secondary system and to test the 

validity of previous analyses. Among the variables 

lnvest~gated were stroke location, the balance of the 

surges in tine service cabie, and the effectiveness of 

arrester protecii~n. Low-side surges were found io 

z.4 -4? 4.*.- I.,":,. ,.-------a-. 'L- --&--I \rVAAalJL Vl LWV U(WI\r bV-UGIIW. LllG LldLUIdI 

frequency of the system and the inductive response of 

the system to the stroke current. The latter 

component is responsible for transformer failures 

while the former may be responsible for discharge 

spots often found around secondary bushings. 

Arresters at the service entrance are effective in 

diverting most of the energy from a lightning strike, 

but may not protect sensitive loads. Additional local 

protection is also needed. The tests affirmed 

previous simulations and uncovered additional 

phenomena as well. 

AUTHORS' CONCLUSIONS 

Low-side surges typically consist of two major 

components: a component ranging in frequency from 

0.8 to 3 MEz and a siowerchanging component that 6- 'LA :-..I :-.- -r*L- *- *LA LG~IGXU~ LUG uuuu~vr; iwpulvnws ul mc sysiern LU me 

rate of change of the lightning stroke current in the 

triplex cable. The tests confirmed earlier analyses of 

low-side surge phenomena in transformers and 

verified that the phenomena affecting the transformer 

can be analyzed by simply considering the 

inductances in the secondary system, neglecting the 

cable capacitances. 

The higher-frequency component is probably 

responsible for the lowenergy discharge "spots" 

observed around the secondary bushings in some 

transformers. However, its greatest impact is likely 

to be on load equipment. 

Arresters at the service entrance are useful for 

forcing low-side surges to be balanced and for 

diverting most of the surge energy away from outlet 

protectors with less energy-handling capability. 

Unbalanced surges were found to generate much 

higher surge voltages in the secondary system and 

are, therefore, undesirabie. Baiancing the surges 

between the two 126-voii side aiso aids in the ---Ae- A:-- -r A--- r --2*L :-.--I--- > -..- ~-3. - piura;r~uu ui rranslurmtsrs w~m mrcnacxu swonaary 

windings. Non-interlaced transformers subject to 

low-side surge failure should be protected with 

arresters in accordance with previous analyses. 

The service entrance arrester in all ratings studied 

(175V to 650V) appears to be quite effective in 

protecting conventional insulation against the lowerfrequency component of low-side surges. However, 

it should not be relied upon to protect the entire load 

circuit, especially sensitive loads, against the higher 

frequency component of the surges. The appropriate 

local protection of devices sensitive to that type of 

surge is still required even if there is an arrester in 

the service entrance. It would appear that most 

practical lengths of secondary circuit feeder cable 

would be sufficient to force most of the energy from 

a low-side surge through the service entrance arrester 

and, thus, heip prevent ihe faiiure of the iocai 

protective device. Che area &at remains open w 

investigation is the effect of the turnoff transient of 

MOV-type arresters in load circuits on the 

transformer. Another is the switching surge and 

power frequency coordination of arresters in the 

secondary circuit. 

REVIEWER'S ANNOTATIONS 

Cascade Bibliography - September 1992 
fl- AA- fl r - - 

U-UG, u.L., bfaiz, M.B., aid Henry, U.L. - Coordinating Lightning Stroke Protechon Fro

the Utility System to Load Devices. Proceedings, Second International Power QualityA

Conference, October 1990, Philadelphia. 

AUTHORS' ABSTRACT AUTHORS' CONCLUSIONS 

Distribution transformers and end user loads can be 

damaged by lightning strokes which pass through 

transformer primary winding arresters and are 

coupled to secondary circuits through grounding 

leads, as well as by lightning strokes directly to 

secondary circuits. This damage can be avoided if ------ 1.. - - --Jl- -r 

~LU~IL~ worumad 8f;fMter~ are deb at the t,.""rf#.rmnr --....A ..-Kw,uwL -=ai, senice cii:=ce ad Io&. 

p=p dsr;l)\pf s~n&r;. serge phe=.=a=m ad 

the importance of transformer ~.nn&ry circuit 

protection coordination to both utilities and end users. 

An effective MOV protection coordination scheme is 

also described and recommended. 

There are more paths for lightning surges to re

customer loads through utility systems than 

generally believed. Multiple grounds at differ

potentials, especially under lightning su

conditions, prevent distribution transformer prim

arresters from protecting secondary circuits. T

principies in using surge arresters to pro

distribution ioads and equipmeni are (ij prevent 

FsOe c.&ye ni kam f io-iv- ;iig '&"Ugh he io& 

q~@~~t p1md md (2) $- *&e aii&e~ 

close to the load or equipment as possible. 

arrester can guarantee the protection of a rem

device. 

In most distribution systems, transformer second

circuit protection is rarely used and when used i

often miscoordinated. Many 175 and 650 v

arresters do not have the current carrying capab

to survive the 34 kA surges that can be expecte

transformer secondaries and service entrances. 

volt arresters can also miscoordinate with transform

primary arrester SSPLs. 650 volt arresters w

coordinate, but may provide inadequate volt

protection. Both current and voltage coordination 

be improved by a 480 volt arrester with a 40 

rating. Properiy coordinated protection using the 

.-.A , VVIL nigh current arrester shouid become stand

pmchce 6.. ---&..-& p1uLFiL.L I- du 61- ihe iiiiliQ's di~tribu

tp2sf~p-es eEd .*:'= la&,. 

REVIEWER'S ANNOTATIONS 

Same conclusions as Marz & Mendis, 1992 

Cascade Bibliography - September 1992 
-- Hairabedian, B. - A survey of Power Line Disturbances at Typicai IBM Computer instaiiations 

in the U.S. for the Period 1988-1992. Document Number TR 21.1507, International Business 

Machines Corporation, Kingston NY, June 1992. 

AUTHORS' ABSTRACT 

The results of a power-linedisturbance survey at 25 

IBM computer installations are presented. Twentyfour (24) of the sites were in the US and one (1) was 

in Canada. The survey logged a total of 22,201 

monitor-days and spanned the period 1988 to 1992. 

The resuits are given in the form of frequencydisiribution tabies, Wei'iuii profiies, histories of ---ALL. --A -L ---- 1 -c -L---A --.--.- IuuIl~y GVGUU, auu sruulluluylw Ul Sualrxl GVGUW. 

Tf;e &a is g)vreE fGr &&ki&aI sics g& fGr 

composites of all the sites. The sites are compared in 

a Weibull parameter-ranking map. The composite 

results of the survey are compared with those of the 

1972 and 1982 IBM surveys. Examples demonstrate 

the use of the Weibull parameters for defining and 

predicting site behavior and the sue of frequency 

distribution data for deriving relative susceptibilities 

of various load systems. 

AUTHOR'S CONCLUSIONS 

(Excerpts) 

History of Events: 

The monthly history data of saglswell and surges 

show some patterns of Periodicity. The month-ofyear data shows an increase in sags for the month of 

Juiy, and mociest increases for August and 7 1 -.. :_ __ -L..Z _.._ _--1_-_11-- r__ rL:_ 

novemoer. lnere 1s no oov~ous explananon rur LIUS 

--'&-- yarLG1u. 

The hour-of-day data shows a much more obvious 

increase in sags during the daylight hours. It 

suggests that some of the sags are directly related to 

daily human activity. 

REVIEWER'S ANNOTATIONS 

A comprehensive report on the recording of disturbances at various computer sites. 

THe detailed tables include statistics on several categories of disturbances. Most significant to the present context 

are the temporary overvoitages, with a classification bin of overvoitages above 35 9% of the nominai rms iine voitage. 

A few occurrences of these are reported in some iocations. 

Cascade Bibliography - September 1992 
-- Hasse, P., Wiesiger, J., and Zischank, W. - Isolations-koordination in Niederspannungsanlage

auch bei Blitzeinschlagen. Electrotech. Zeitschnp, Jan 1989, pp 64-66. (In German; Englis

translation available from FD Martzloff) 

AUTHORS' ABSTRACT AUTHORS' CONCLUSIONS 

This paper describes the principle of insulation 

coordination in low-voltage consumer systems for 

mains-camed overvoltages according to IEC Pub 664 

and DIN VDE 0109. The required surge voltage 

levels can also be maintained during a direct lightning 

stroke. For mains-camed overvoltages and for the 

case of a direct stroke, distribution of the surge 

current between the two arresters in different 

appiication caiegories are determined. 

7he authors do not label a particular part of th

article as 'Conclusion' but the closing paragrap

reah as follows: 

Thus the spark gap will -largely independently fro

the impedance of the downstream system - on

respond to surge currents having a higher rate 

change of current than 1 kAlps, which correspon

to a 8/20 ps wave, with a peak current of 5 kA. 

more ihan 99 5 of the cases, direct iightniDg curren

3 a-ie a ~gher vd-ue A&= Mlps! So ci rc-a ii 

Figure 3 makes it possible for the spark gap 

distinguish between a distant stroke and either a nea

by or direct stroke. This safety method is effectiv

as well for partial lightning currents entering th

structural system by the mains network (near-b

stroke) as also in case of partial lightning curren

that travel backwards into the mains from a buildin

struck by lightning. 

REVIEWER'S ANNOTATIONS 

Cites 10l350 ps as a waveform to consider for simulation of near-by and direct stroke, in addition to the 8/20 p

waveform, which is considered appropriate for distant strokes. 

Proposes to provide at the service entrance a two-stage surge arrester consisting of a gap on the utility side and 

varistor on the load side, separated by a coordinating inductance. Clearing of power-follow in the gap is n

discussed. 

Cascade Bibliography - September 1992 
Hasse, P. - Overvoltage Protection of low-Voltage Systems. IEE Power Series, Peter Peregrinus 

Ltd. London, 1992. (Original German edition in 1987) Available in the U.S. from IEEE. 

Excerpts from back cover abstract: 

... The author gives examples of overvoltage damage to electrical systems with electronic devices, such as 

measurement, control and regulating circuits and data processing systems. The book goes on to discuss causes . . . . The operation and application of proven overvoltage protection devices are considered and the author refers to 

relevant German and international standards. 

Chapter headings: 

Damage caused by overvoitages 

ihi of hadi overvoitages pi&&",e E-u is 

~c-=my?i~"YtJ md &y/i~ad . . -. 

Practical examples of protection 

Final remark 

Reviewer's annotations 

Sections 5.4.1.4, Coordination of protective elements, and 5.4.2, Arresters for power systems discuss the topic of 

cascades, with reference to a protection scheme that includes a gap, which may be of the "quenching gap" type also 

described in that chapter. Thus, the downstream device is spared the dissipation of large energy, following 

sparkover by the gap. No computations are presented in association with the discussion of the principle of tlus 

approach to coordination. 

Examples are given, with schematics and device photographs, of the application of arresters in low-voltage TN and 

TT networks. 

Cascade Bibliography - September 1992 
Hostfet, O.T., Herviand, T., Nansen, B., and Huse, J. - Coordination of surge protecti

devices in power supply systems: Needs for secondary protection. Proceedings, Internation

Conference on Lightning Protection, Berlin, September 1992. 

AUTHORS' ABSTRACT AUTHORS' CONCLUSIONS 

Primary SPDs at the origin of an LV installation will 

not in general assure sufficient overvoltage 

protection. Voltage oscillations will occur within the 

installation depending on the circuit lengths, resonant 

frequencies, steepness of the surge impulses, etc. 

Therefore, there is a need for additional SPDs for 

sensitive apparatuslequipment within the installation. 

To ensure safe coordination regarding the energy 

on *he 3'"u8, -he pto~wiion ie"& jciamping 

,,~l,~,,~\ AC ,I,- ..r;-..,-. Dmr rL1..la -,.-,.-^11.. I.. VVX-&Y, V* uv yfiu.pAJ Si YJ JUWUlSb g'ZUG1411r UCi 

somewhat lower than for the additional SPDs 

(secondary protection) within the installation. 

On the basis of observed failures on secondary sur

protection devices, theoretical and experimen

investigations are performed in order to clarify t

need for such protection including the sharing 

energy stresses in relation to the primary sur

protection system. 

The analyses have shown that, generally, volta

osciiiations w~ll occur within an installation w

surge protection. The ampiitudes of these osclllatlo

depends on severid circuit parameters as weii as t

incoming surge voltages. In special cases, t

maximum voltage may be more than twice t

protection level on the primary surge protecti

devices. Accordingly, there might be a need f

secondary protection, especially with respect 

various sensitive equipment. 

Furthermore, it is found that in an installation w

two or more surge protective devices, the high

energy stresses will generally occur on the dev

with the lowest clamping voltage. Therefore, t

protection level for the secondary protection shou

be selected somewhat higher than for the prima

protection independent of the location. In this w

the current flowing in the secondary devices will 

lower than in the primary ones, and sufficie

protection is obtained for sensitive equipm

aithough the nominai ciamping voitage is reiative

high. 

REVIEWER'S ANNOTATIONS 

Cascade Bibliography - September 1992 
HUS~, J.P. - Contributions to the revision of Doc 28A(Sec)47, Internal document, 

ZEC/SC28A WWl, 1988. 

AUTHOR'S ABSTRACT 

('Introduction') 

AUTHOR'S CONCLUSIONS 

(From concludiig 'General comment') 

Calculation results are presented in order to give a From the analysis made in this paper, it is seen that 

contribution to the revision of the document the suppressor energy stresses occur on the 

[28A(sec)27 - 'Explanation of interfaces for suppressor with the lowest clamping voltage 

overvoltage categories]. In the paper, only stresses representing the lowest resistance to ground. 

on surges suppressors are dealt with. Accordingly, it seems that concerning the stresses 

upon voltage limiters, suppressors, etc., it would be 

preferable to have one overvoltage category only. In 

that case several suppressors with the same clamping - A- .. 3 L. - .. . vulragc: wu~u oe: appllea and the stresses wouid be 

i~E.&$~e sh-d L&pGea *Ae sqjprawB. 

REVIEWER'S ANNOTATIONS 

These comments on the simplifications made in the 28A approach (Table E) were the first submitted that provided 

computations of cascades. In particular, the assimilation of the wavefront of an 8/28 ps current to a 114 sine wave 

of 30 kHz impulse was debated. 

In support of the objections, the paper presented results of computations, but its was not until later that papers 

emerged that included both computations and actual tests, validating each other. 

Noteworthy is the concluding statement that the device with lowest clamping level is subjected to the highest stress, 

in contrast to the underlying assumptions of the IEC 664-1980 staircase. 

This contribution has appeared in several IEC documents, SC28A, TC64, and now SC37A. 

Cascade Bibliography - September 1992 
IEC 28A(iiSAiLas Vegas')OY - (Draft) Explanation for over-voltage categories. December 198

Amended August 1987. 

REVIEWER'S ANNOTATIONS 

The seminal IEC paper on cascade coordination - before the term was coined. 

Based on assumed 8/20 ps waveforms and some separating inductive impedance, approximate computations w

made by assuming that at each stage of a multiple-step cascade, the driving voltage is that established by 

preceding surge-protective device. 

Numerical simulations have made this paper obsolete. 

Cascade Bibliography - September 1992 
IEC 28Aj~orwayj - Comments of the Norwegian Ivm-onai Committee on Document 

28A (Secretariat)47 

INTRODUCTION CONCLUSIONS 

In this document [28A(Secretariat)47] extensive 

simplifications are made in order to present simple 

explanations. It seems, however, that some of the 

simplifications and assumptions made are 

questionable. Accordingly, the results presented 

(Table E for instance) should be reconsidered. 

Furthermore, there are some statements in the 

document that should be revised. 

As stated in the introduction, this document should be 

reconsidered and revised on several points. It is 

proposed that more realistic calculations be 

performed in order to analyze the stresses on 

interface suppressors. Representative crest values of 

8/20 current impulses for testing purposes should be 

determined on the basis of results from these 

analyses. 

REVIEWER'S ANNOTATIONS 

These comments on the simplifications made in the 28A approach (Table E) were the first submitted that provided 

computations of cascades. In particular, the assimilation of the wavefiont of an 8/28 ps current to a 114 sine wave 

of 30 kHz impulse was debated. 

In support of the objections, the paper presented results of computations, but its was not until later that papers 

emerged that included both computations and actual tests, validating each other. 

See the 1988 Huse citation for an expanded contribution of this subject. 

Cascade Bibliography - September 1992 
IEC 37AiwG3(Convenor)i - Drafi Application Guide, 1992. 

SCOPE AUTHOR'S CONCLUSIONS 

This application Guide gives indications regarding None 

selection and installation of SPD to be co~ected to 

50/60 Hz AC and to DC power circuits rated 50 to 

loo0 v. 

REVIEWER'S ANNOTATIONS 

Annex 1, 'Two and three step protection efficiency' is the same as giver! !F. C!2&.9 2.2 of !EC TCSd WC-3 (Ad

WG Convenor)l of February 1990. 

Shows a graph of required Temporary Overvoltage levels of 1.7 per unit at 3 seconds and 3.0 per unit at 

second. Such a requirement is likely to challenge the use of 130-V varistors on a 120-V system. 

Cascade Bibliography - September 1992 
IEC @/'iVG3 i38A - Expimation of interfaces for overvohage categories. Suppiement io 

Appendix B of Repon 664, November 1990. 

ABSTRACT 

(from 'General' Clause) 

The framework of IEC publication 664 includes cases 

where the incoming supply to an installation can be 

considered inherently controlled and cases where 

protective control is used. This supplement deals with 

situations where protective control is used in the 

installation or within equipment connected to the 

installation. In this latter case the installation may hzxvre ~sm: =r pr&a+;e cc=trG!. 

It must be recognized that successive interface 

devices, such as surge suppressors, may interact 

detrimentally unless proper grader is provided in their 

selection. In this respect it is also noted that there is 

a fundamental difference in the behavior of surge 

suppressors based on air gaps as opposed to those 

based on solid-state monotonic devices (varistors or 

diodes). When a system includes both types of surge 

suppressors, it is necessary to take into consideration 

the impinging surge voltage as well as the 

corresponding available surge current. 

CONCLUSIONS 

(From Clause 2) 

Three basic requirements determine the selection of 

an interface surge suppressors: 

- The rated voltage of the surge suppressor is 

selected at a value above the worlung 

voltage of the system. 

- Within the constraints of the first two 

conditions, the residual voltage of the surge 

suppressor should be selected according to 

the impulse withstand voltage of the 

equipment. 

It is possible within a system to cde anumber of 

interface surge suppressors to achieve the various 

overvoltage categories. The number of overvoltage 

categories will be determined by the number of 

different surge suppressor residual voltages specified. 

However, it is also possible to achieve the lowest 

overvoltage category by the use of a suitably selected 

zGpp iesmi zt 'he 6r;gh of tkle -~s*a:;ation* 

REVIEWER'S ANNOTATIONS 

Note the continuation of the expectation that a cascade is possible, but the emergence of the idea that the lowest 

clamping voltage might be obtained by a service entrance arrester. 

Cascade Bibliography - September 1992 
IEC 77(CO) i i 8 Ciassi@ztion of Electromagnetic Environments (Committee Draft, 1992) 

REVIEWER'S ANNOTATIONS 

This document is an attempt at describing the total electromagnetic environment, both radiated and conducted. 

starts by identifying the phenomena that produce disturbances, then proceeds to state what levels may be encounter

at various categories of locations. The attempt is to have one single value for one location, but consensus 

selecting these level has been a difficult process. Further revisions are likely before the document reach

recognition as a standard. Present plans at IEC is to publish it as a Report. 

Cascade Bibliography - September 1992 
.*- iagergren, E.S., iviutzioff, F.D., Pari<er, MA, and Sciiiiier, S.B., - Tie effect of repetitive 

swells on metal-oxide varistors. Proceedings, PQA 92 Conference, September 1992, pp xx-xx. 

AUTHORS' ABSTRACT 

Neither the effects of repetitive swells on metal-oxide 

varistors, nor the occurrence of swells have been 

documented in the literature. The paper briefly 

describes a laboratory system capable of generating 

arbitrary swells and applying them to test varistors. 

A statistical experiment on five lots of varistors has 

been performed and preliminary results are reported. 

Effects of amplitude, duration, and number of swell nnn..-a-nar .-a ,rranrarl ..r:,, VCCULICILICW Qlr a-, LWu5 ii~ a ciktiioa ke 

&=cgbOP_ iz v2T;rrteT m&2! \'~!&ge frQE &fCre 

after the we!! sequence. 

AUTHORS' CONCLUSIONS 

1. Applying swells produced by a computerdriven 

system is a practical method for subjecting varistors 

to repetitive swells under controlled conditions. 

2. The factors that affect the varistor response are 

the amplitude of the swell, the duration of the swell, 

and the number of swells experienced in the life of 

the varistor. 

3. It seems that failure by thermal runaway occurs 

quickly when amplitude or duration settings are large. 

Failure caused by gradual aging (the 10% limit 

quoted by industry) appears to require a larger 

number of swells than those applied so far in our 

experiments. 

4. These results lead to an action items list, 

with an open invitation to all interested parties for 

contributing to shared information on the subject. 

REVIEWER'S ANNOTATIONS 

This paper is only a status report on an ongoing project aimed at characterizing the aging, if any, of generic MOVs 

under the effect of repeated swell over the service life of a varistor. 

Two mechanisms have been encountered in the test series: a relatively small (less than 3 5%) change in varistor 

nominal voltage for limited cumulative stresses, and a failure by overheating when exposed to stresses of excessively 

longduration (seconds) temporary overvoltages. 

A more comprehensive paper should be presented at a future meeting. 

Cascade Bibliography - September 1992 
-iai, J.S. and -Martzloff, F.D. - Coordinating Cascaded Surge-Protective Devices. Proceeding

ZEEE/LS Annual Meeting, October 199 1. 

AUTHORS' ABSTRACT 

Cascading surge protection devices located at the 

service entrance of a building and near the sensitive 

equipment is intended to ensure that each device 

shares the surge stress in a optimum manner to 

achieve reliable protection of equipment against 

surges impinging from the utility supply. However, 

depending upon the relative clamping voltages of the 

two devices, their separation distance, and the 

waveform of the impinging surges, the coordination 

may or may not be effective. The paper provides 

computations with experimental verification of the 

energy deposited in the devices for a matrix of 

combinations of these three parameters. Results 

show coordination to be effective for some 

combinations, and ineffective for some others, a 

finding that should reconcile contradictory 

conclusions reported by different authors making 

different assumptions. From these results, improved 

coordination can be developed by application 

standards writers and system designers. 

AUTHORS' CONCLUSIONS 

1. Coordination of cascaded devices can 

achieved under various cornbinations 

parameters, but some combinations w

result in having a suppressor with l

energy-handling capability called upon 

divert the largest part of the surge energ

This uncoordinated situation can cre

adverse side effects when hizh curr

surges occur. 

2. Significant parameters in achievi

successful coordination involve three facto

over which the occupant of the premises h

no control: the relative clamping voltages 

the two devices, their separation distan

and the prevailing waveforms for imping

surges. This uncontrolled situation prese

a challenge and obligation for standar

writing groups to address the problem a

develop consensus on a trade-off 

advantages and disadvantages of High-L

versus Low-High. 

3. Coordinated schemes can be proposed 

utilities to their customers, including 

service entrance arrester and one or m

plug-in devices to be installed for 

dedicated protection of sensitive applianc

However, even such an engineer

coordinated arrangement could be defea

by the addition of a suppressor with a v

low clamping voltage, not an insignific

likelihood in view of the present competit

for lower clamping voltages. 

REVIEWER'S ANNOTATIONS 

The paper describes 72 combinations of 130 V, 150 V, and 250 V devices arranged in cascades, with separat

distances ranging from 5 to 40 meters, and with 8/20 ps and 10/1000 ps impinging waveforms. 

While the 8/20 ps waveform can still result in a contribution from both devices to sharing the surge energy, 

1011000 ps waveform does not produce any inductive separation of the devices past the rise time, so that ene

is equally shared between devices of equal rating, and for two different devices, the lowest rated take 90% or m

of the total energy. 

Cascade Bibliography - September 1992 
Lai, J.S. - Performance Criteria for Cascading Surge-Protective Devices. Proceedings, Open 

Forum on Surge Protection Application, NISTIR-4654, August 199 1, pp 147- 160. 

AUTHOR'S ABSTRACT AUTHOR'S CONCLUSIONS 

Cascaded surgeprotective devices in a low-voltage 

power system interact each other under surge 

conditions. Coordination of cascaded devices may be 

achieved by manipulating the device clamping level 

and energy handling capability. However, as cascade 

condition may be effective for a certain surge source 

and distance between the devices but not effective for 

other cases. To develop the performance criteria for 

cascaded devices, all possible environments need to 

be taken into account. This paper uses the voltage 

clamping level of cascaded devices, their separation 

distance, and the surge waveform as parameters to 

study the energy deposited in the devices. All 

assumed cases were studied using computer 

simulation with necessary experimental verification. 

Results show reasonable agreement between 

simulation and experiment. A total of 72 case study 

results provide standards writers and application 

engineers with quantification information for the 

development of improved cascade coordination. 

With study of a total of 72 cascade combinations 

using different parameters, this paper initiates a 

broader view of cascade coordination and a need for 

further consensus on real-life environments which 

involve the magnitude and waveshape of the highenergy impinging surges from utility lines, 

probability and severity of losing neutral, surge 

energy from switch-mode power conversion 

equipment; size of conductors, and the distance 

between the surze-protection devices. 

Although the MOV model described in this paper 

successfully predicts the I-V characteristics and surge 

responses, especially the energy sharing of cascaded 

devices, more analytical studies are needed to reduce 

the deviation between simulation and experiment. 

These include: 

MOV stray inductance and capacitance if 

more accurate waveshape matching is 

necessary. 

Consensus of MOV characteristics for the 

same voltage level and size of the device but 

different manufacturers 

Modeling of a gap-type surge protection 

devices which would cause different surge 

responses when used as the arrester to 

replace MOVs. 

Well-defined impinging surge sources 

including voltage and current waveforms and 

the coupled source impedance network. 

REVIEWER'S ANNOTATIONS 

This paper contains a detailed report on the measurements and computations that were the basis for the two papers 

[Lai & Martzloff, 19911 and [Martzloff & Lai, 19911. 

Cascade Bibliography - September 1992 
'L&, M.V. - Determining Temporary Overvoltage -Levels for Application of Metal-Oxide Sur

Arresters on Multigrounded Distribution Systems. IEEE Transactions PWAW-5, April 1990, 

936-946. 

AUTHOR'S ABSTRACT AUTHOR'S CONCLUSIONS 

Abstract: This paper provides an evaluation of 

different anaiytical methods that may be used to 

calculate values of temporary overvoltage on 

multigrounded distribution systems as a result of 

single line-to-ground faults. The methods are 

evaluated in terms of their general accuracy, their 

ability to account for changes of earth resistivity, 

ground electrode resistances and grounding 

frequency, and also in terms of the overall impact of 

such changes on the calculated overvoltage level. 

Recommendations are provided for the use of these 

methods under different sets of system conditions. 

The objective of this study was to evaluate the imp

of the overvoltage calculation methods on 

selection of metal oxide arrester ratings 

multigrounded distribution systems in the presence 

variable system grounding parameters. Accur

arresters are extreme!y sensithe to ove.rvn!tages. T

results of the study kdirate &st- presea!!y 

ratings, derived on t!x basis nf rhp a-dy 

assumed value of 125 pu;, lire suffici

conservative only for well grounded system

Overvoltages on systems where the ground

parameters depart significantly from the nomi

values should be calculated using the meth

recommended in this paper. In many cases revis

of ratings to be used on such systems may 

required. 

Based on a comprehensive evaluation of differ

methods for calculation of overvoltages 

multigrounded distribution systems, it has b

concluded that the commonly used method bases 

symmetrical components is inadequate for anyth

but the simplest calculation for a system with n

ideal grounding parameters. 

For systems where poor grounding conditions 

known to prevail, the best method of analysis is 

neglect the ground effects altogether. 

The best overall results are provided by 

sophisticated, matrix algebra bases method, wh

analyzes the ladder network cells of 

multigrounded distribution neutral individually. 

REVIEWER'S ANNOTATIONS 

Cascade Bibliography - September 1992 
Martzloff, F.D. and Crouch, K.E. - Coordination de la protection contre les surtensions dans 

les rkseaux basse tension residentiels. Proceedings, 1978 IEEE Canadian Conference on 

Communications and Power, pp 451-454. (In French; English translation available from FD Martzloff: 

Coordination of overvoltage protection in low-voltage residential systems) 

AUTHORS' ABSTRACT 

The development of metal-oxide varistors has made 

possible a substantial improvement in the mitigation 

of overvoltages in residential, commercial or light 

industrial power systems. For instance, transient 

suppressors are now available that can be plugged 

ink a wd! fnaptx!=, t&1~ -6" pssib!e the 

pmtpft;~n ~f zp.~?p!ia~s ac =!=&&c &J~W that . . mioht & &mgpj by ~v=mdtag=s mcurzg m -a" 

pmxtr syckmc. 

2. Commercially available protective devices are 

capable of limiting overvoltages to acceptable limits; 

even in the case of an injection corresponding to 

extreme values, several arrangements may be 

considered: 

a) A lightning arrester consisting of a spark 

gap and silicon carbide varistors can limit the 

~vp~e!t~g~ t,n &QE$ 2J V, e!i&a!hg !he +k 

breakd~w- the wir;bg ma the zt,tpnhn! fire 

hward. This 2m V !i--t pmvi&.~ pmtPrt_i~n fnr 

conventional appliances but may he hdqwte to 

protect electronic devices that tend to be more However, due to economic considerations, these sensitive. 

suppressors have only a limited capability for 

absorbing high current surges that may be associated b) A metal-oxide varistor, presently 

with lightning strikes occurring nearby. Thus, one available only as an industrial component package, 

may ask whether the installation of a suppressor with correctly installed in the service panel (short 

limited capability might not pose a risk of failure or connections) would be sufficient to limit overvoltages 

create a false sense of security. for all the building, even for high amplitude lightning 

It is then worthwhile to examine what occurs in a 

building provided with suppressors having different 

capability, located at different points of the building. 

as a function of the surge current intensity imposed 

by the lightning strike. Furthermore, the combination 

of several suppressors may allow a coordinated 

p+&=.ti~= fer r&&!f: QF~&=, WE& it weu!d 

worthwhile to demonstrate; 

AUTHORS' CONCLUSIONS 

1. It is sufficient to inject, in the ground conductor 

of the service drop, a surge current corresponding to 

a moderate lightning stroke to reach hazardous 

voltages between the phase and neutral conductors 

within the building. 

strokes. 

c) A varistor with limited capability, the 

VSP-1, installed at a particular receptacle, will limit 

overvoltages at that point to values that are acceptable 

for electronic devices, without being itself exposed to 

hazardous stress, if its distance from a panel - not 

equipped with protection - is greater than about 10 

meters. For shorter distances, the stress applied to 

the VSP-1 might exceed the expected reliability, with 

failure of the varistor. This failure would still 

provide protection during the surge, but lead to a trip 

of the panel breaker. Of course, if a protection 

according to (b) were provided, it would not be 

necessary to install a VSP-1. If the protection 

provided at the service panel is less than ideal (HLP), 

the addition of a VSP-1 at the receptacles that supply 

sensitive devices would provide protection for these 

devices, while the HLP would provide diversion of 

high currents. 

REVIEWER'S ANNOTATIONS 

The conclusion presented in this paper, that coordination can be achieved, is based upon two premises: 

1. The impinging surge (into the ground systemi mt in phxw c~dmt~n) is ca@d bt_n & &&- 

conductors of the service drop and appears as a L-N mode at the service entrance, hat still with a short 

rise time. 

2. The service entrance is a gap-varistor combination, so that as soon as the gap has sparked-over (during the 

ascending front of the wave), all current ks transferred to the arrester, away from the suppressor at the end 

of the branch circuit. 

Cascade Bibliography - September 1992 
Martzloff, F.D. - Coordination of Surge Protectors in Low-Voltage AC Power Circuits. IEE

Transactions PAS-99, January/Febmary 1980, pp 129- 133. 

AUTHOR'S ABSTRACT AUTHOR'S CONCLUSIONS 

Surge protectors can be installed in low-voltage ac 

power systems to limit overvoltages imposed on 

sensitive loads. Available devices offer a range of 

voltageclamping levels and energy-handling 

capability, with the usual economic trade-off 

limitations. Coordination is possible between lowclamping-voltage devices having limited energy 

c2pgbihty md &g~=&w~g~vG~~ge &i,+- hgyhg 

&gh =~=q~y qyg&!iv. pue ppr gj-j~ 

e.~aqn!~s ~f cmrd;n.tion, we!! s &!it;.==! 

experimental results on surge ppgatim. 

Coordination of surge protectors is feasible w

existing devices, even if device characteristics var

The experiments reported in the paper show thr

facts from which conclusions can be drawn: 

Fact 1: Where an unidirectional current is injec

into the ground system only, the response 

rt - we system is an osciiiating voitage, at 5

1-TT- C- &t - --.---- 2 - - MIL lor me syswm uexri'd. 

2: pue wGi,ra!sEr;: wcice iiiiWm, 

determined by loading the system, is in 

range of 50 to 100 il for the particu

system investigated. 

Fact 3: Without substantial connected loads in 

system, the opencircuit surges appearing 

the service entrance propagate along 

branch circuits with very little attenuatio

Con. 4: Coordination of surge suppressors requir

a finite impedance to separate the t

devices, enabling the lower voltage device 

perform its voltageclamping function wh

the higher voltage device performs 

energy-diveriing hciion. 

I-.-... -"ii. 2. <. 7%- ~~~ept that ~iiige ~dttg- d

fiGm +Ae sr".ie ectm~ to Gii;e~

misleading for a lightly loaded syste

Rather, the protection scheme must be bas

on the propagation of unattenuated voltag

Con. 6: Indiscriminateapplication of surge protect

may, at best, fail to provide the intend

protection and, at worst, cause disrupt

operation of the suppressors. What 

needed is a coordinated approach based 

the recognition of the essential fact

governing devices and surge propagation

A condead vesiai~ iid ~r~k~a: piiSicztioii of the kifomtion initiaiiy deveioped in the proprietary (n

declassified) 1978 Crouch & Martzloff report. 

Cascade Bibliography - September 1992 
Martzloff, F.D. and Leedy, T.F. - Selecting Varistor Clamping Voltage: Lower is not Better! 

Proceedings, 1989 EMC Zurich Symposium, pp 137- 142. 

AUTHORS' ABSTRACT 

Surge protective devices, such as varistors, are 

applied to protect sensitive load equipment against 

power-line surges. The need to provide low 

clamping voltage for protection of equipment with 

low inherent immunity must be balanced against the 

risk of premature aging of the protective device. 

Lower clamping voltage causes more frequent 

&teFJeE~3x of *Ae p;.c;*ative device, K.pIe.a:b$ i*& 

-e-erroino 7h~ pgpr dmfib fez pssib!e ~1- =f *-- 

gj& prnah~te gghg, -!!kg for 2 m~f= ~~ern md 

&us more reliable application_ of protm-tive device-s. 

AUTHORS' CONCLUSIONS 

Several mechanisms involving surges or momentary 

overvoltages can cause accelerated, or premature 

aging of varistors, if the clamping voltage is selected 

at too low a level without appropriate consideration 

of all factors. 

A second mechanism, fortunately not occurring too 

frequently, involves fuse blowing and can produce 

immediate destruction of the varistor at the first 

occurrence if the clamping level is selected at too low 

a level. The implications of this situation needs 

greater recognition among varistor users. 

A third mechanism, decreased thresholds of thermal 

runaway in the long term, is directly related to the 

selected clamping level, with aging accelerated by a 

low clamping level selection. This situation is well 

recognized by high-voltage arrester designers, but not 

by low-voltage electronic circuit designers. 

The obvious, but difficult remedy to this situation is 

to design equipment with a reasonably high surge 

withstand capability so that retrofit using protective 

devices with very low clamping voltage will not be 

necessary. For those situations where a close 

protection would be required, a very careful 

consideration of all factors becomes imperative, 

rather than cookbook application of protective 

devices. 

REVIEWER'S ANNOTATIONS 

The title is the theme. 

Cascade Bibliography - September 1992 

Martzloff, F.D. and Lai, J.S. - Cascading Surge-Protective Devices: Coordination versus the 

IEC 664 Staircase. Proceedings, PQA 91 Conference, pp 19 1- 198. 

AUTHORS' ABSTRACT AUTHORS' CONCLUSIONS 

Cascading two or more surge-protective devices 

located respectively at the service entrance of a 

building and near the sensitive equipment is intended 

to ensure that each device shares the surge stress in 

an manner commensurate with its rating, to achieve 

reliable protection of equipment against surges 

impinging from the utility supply as well as internally 

,,,,,*,A " ., .-." UA ....-... a- a-...a-.I:-, ....A- *La G W LlUWGVGl, UGpUUUlg Upll LUG 

C!q&g w!*ags =f *Ae de.JiC~s) *heir 

qk=tiOn &stae, ad t&= WPVefem ef t&= 

iqkghop surge, rmc&&i~n my or mav mt_ k. 

effective. The paper reports computations confirmed 

by measurements of the energy deposited in the 

devices for combinations of these three parameters. 

1. Coordination of cascaded devices can be achieved 

under various combinations of parameters, but some 

combinations will result in having a suppressor with 

low energy-handling capability called upon to divert 

the largest part of the surge energy. Thls 

uncoordinated situation can create adverse side effects 

when high current surges occur. 

2. S@Afiwt p--"tes & =fie\,@ Fd-fid 

cmr&btic?x? &YO!vp th~~ fxtss, ever =Sch tAe 

wr.~pzt of the prekss mntr~!: the. relative 

clamping voltages of the two devices, their separation 

distance, and the prevailing waveforms for impinging 

surges. This uncontrolled situation presents a 

challenge and obligation for standards-writing groups 

to address the problem and develop consensus on a 

trade-off of advantages and disadvantages of 

High-Low versus Low-High. 

3. Coordinated schemes can be proposed by utilities 

to their customers, including a service entrance 

arrester and one or more plug-in devices to be 

installed for the dedicated protection of sensitive 

appliances. However, even such an engineered, 

coordinated arrangement could be defeated by the ->a:.:-- -c - --.:.L - 1 ---. -I---:-- ;IULUILIUU UI a aupprwwx wlul a wry IUW sraiuplrry 

..A~+~,.P -A+ ;rn:-:Gnnr+ l:tP1;hrrrrrl ;- .r;a..r -4 *ha vu~wp, UUL au samts~lttb~~~~ ttn=tu- LU VLG- UL we 

pmat mmpd?icE fcr C!sFapi3g -gC!tages. 

REVIEWER'S ANNOTATIONS 

Cascade Bibliography - September 1992 
Martzloff, F.D. - On the Propagation of Old and New Surges. Proceedings, Open Fonun 

Surge Protection Application, NISTIR-4654, August 1991, pp 19-28. 

AUTHOR'S ABSTRACT 

The revised IEEE Recommended Practice on Surge Voltages ANSIIIEEE C62.41 has introduced a new generat

of surge waveforms; how they travel in low-voltage power systems will affect some of the earlier tenets on su

propagation characteristics. The recent emergence of cascaded surge-protective devices raises a new set of conce

in which propagation characteristics play an important role. 

The objective of this paper is to review the propagation characteristics of the old and the new generation of su

waveforms. Measurements are reported and the effect (or, rather, the lack of effect) of wire diameter 

&-g=eE:g! by a simle exF~mezbl deEGmtmiiGE. 

TABLE 1 

MEASURED CURRENTS AND VOLTAGES, CALCULATED IMPEDANCE (10 m CABLE) 

FOR THREE WIRE SIZES AND THREE WAVEFORMS 

Nominal generator I Ring Wave 1 Combination Wave 

waveform I I I I 

1 011 000 ps Wave 

Peak current, I, (A) 

Actual rise time of current 

(PSI 

*Wire size (AWG) 

REVIEWER'S ANNOTATIONS 

Data for evaluating the effect of the inductance in separating two devices, as a function of waveform (major effe

and wire size (minor effect). 

100 

0.8 

10 ) 12 1 14 

Cascade Bibliography - September 1992 

170 

22 

10 1 12 1 14 - - 

Peak vo!t=ge during surge 1 800 1 790 1 800 1 760 1 780 1 Qnn 

!",! I I I """ 

Effective impedance V,/I, 4.5 4.7 

cn) 

8.0 7.9 8.0 4.6 
~artzioff, F.D. and Lai, J.S. - Cascading surge-protective devices: Options for effective 

implementations. Proceedings, PQA 92 Conference, September 1992, pp xx-xx. 

AUTHORS' ABSTRACT 

The basic and critical parameters for a successful 

coordination of cascaded surge-protective devices 

include the relative voltage clamping of the two 

devices, their electrical separation through wiring 

inductance, and the actual waveform of the impinging 

surge. The authors examine in detail the implications 

of the situation resulting from the present ~~~~~.l~&& annlirzatinn nf &vjcp-s ~th !Q\U -rr------- 

clampkg voltage at the end of branch circuits and 

devices with hizher clamping voltase at the service 

entrance. As an alternative, several options are 

offered for discussion, that might result in effective, 

reliable implementation of the cascaded protection 

concept. 

AUTHORS' CONCLUSIONS 

1. The reality of having many millions of 130- 

V rated varistors installed on 120-V 

systems, and 250-V rated varistors installed 

on 230-V systems makes the ideal scenario 

of a wellcoordinated cascade difficult or 

perhaps unattainable in the near future. 

2. As a compromise, a cascade with equal 

voltage ratings for the arrester and the 

suppressor can offer successful coordination, 

if the impinging surges are presumed to be 

reiaiiveiy short. 

The coordination of a simple cascade of an 

arrester and a suppressor of equal voltage 

rating, both connected line-to-neutral, is 

slightly improved by the larger cross-section 

of the arrester. However, an unfavorable 

combination of tolerances for the two 

devices can wipe out the improvement. 

The neutral grounding practice of the utility 

has a profound effect on the cascade 

behavior, and must be thoroughly 

understood for successful application of 

cascaded surge protection. Clearly, 

additionai studies are required in this area. 

The waveform of the impinging surge has 

also a large effect on the outcome. If more 

data were available on the frequency of 

occurrence of 'long surges', some of the 

uncertainty surrounding the success of a 

cascade would be lifted. 

The idea of an expendable, one-shot arrester 

at the service entrance could offer a solution 

out of the dilemma and should be further 

investigated. 

REVIEWER'S ANNOTATIONS 

Cascade Bibliography - September 1992 
~arz, M.B. and Mendis, S.R. - Protecting Load Devices from the Effects of Low-Side Surg

Proceedings, ZEEE/ICPS Conference, May 1992 

AUTHORS' ABSTRACT AUTHORS' CONCLUSIONS 

Wherever lightning and power systems grounds exist, 

distribution secondary systems are subjected to high 

voltage surges due to lightning current seeking 

ground through low-voltage circuits. Utilities are 

becoming aware of this low-side surge phenomenon 

and are applying secondary arresters to protect their 

distribution transformers. This practice can increase 

the voltage stress at the customer service entrance. 

If any ground paths exist on the customer side of the 

service entrance, these surges can penetrate further 

into the customer's system. Damage caused by lowsick surges can be avoid& if properiy coordinated 

arresters are installed at the transformer secondary, 

service entrance, and load device. 

This paper describes the secondary surge phenomena 

and the importance of protecting the service entrance 

and critical load devices properly, especially when 

secondary arresters are applied on distribution 

transformers. A properly coordinated and effective 

MOV protection scheme is described and 

recommended. 

There are more paths for lightning surges to rea

loads through utility systems than is genera

believed. Multiple grounds at different potent

prevent distribution transformer primary arrest

from protecting secondary circuits, especially un

lightning surge conditions. Two principles to foll

when using surge arresters to protect distribution lo

devices are (1) prevent the surge current fr

flowing through the load or equipment to ground a

(2) place the arresters as close to the load 

equipment as possible. No arrester can guarantee 

protection of a remote device. 

In most distribution systems, transformer second

circuit protection is rarely used and when used i

often miscoordinated. Many 175 and 650 v

arresters do not have the current carrying capabi

to survive the 33 kA surges that can be expected 

transformer secondaries and service entrances. 

volt arresters can also miscoordinate with transform

primary arresters SSPLs. 650 volt arresters w

coordinate, but may provide inadequate volt

protection, Both current and voltage c&rdination 

& 

be improved by a 480 volt arrester with a 40 

rating. Properly coordinated protection using the 

volt class arrester should become standard practic

pi~iwi bib disiribiiiion transformers and i

REVEWER'S ANNOTATIONS 

Note the recommendation of a 480-V arrester at the service entrance. This recommendation proceeds from conce

about the current coordination of the arrester. 

However, the coordination of energy sharing between service entrance and internal suppressor does not seem to 

addressed. 

A table shows current values in the range of 2 to 17 kA for 'Load Arrester' but this reviewer could not find 

definition of the what this load arrester is -- is it a SPD at the end of a branch circuit ? Are we talking about 17 

flowing in the branch circuits wiring ? 

Cascade Bibliography - September 1992 
Meyer, J. P. - Parafoudres en Cascade. Proceedings, UTE Workshop on Surge Arresters, Paris, 

March 20, 1992 (In French). 

AUTHOR'S INTRODUCTION 

(Translated excerpts) 

AUTHOR'S CONCLUSIONS 

(Translated excerpts) 

The purpose of this paper is to present a report on SC28A and TC64 are at a dead end and the 

current standard activities. . . . foundations of the [IEC 6641 concept are shaking. 

Let us hope that enlightenment will come from the 

A cascade is made necessary by the surge withstand LV Arrester document from SC37AiWG3 . . . levels of equipment in a 2301400 V installation: 

- 6 kV at the point of common coupling A cascade of arresters is always to be preferred over 

- 4 kV at the point of fixed switchgear a single arrester! 

- 2.5 kV at the level of common end-use equipment 

- 1.5 kV at the level of sensitive equipment 

This handout material was distributed in support of a presentation by J.P. Meyer at a workshop organized by Union 

Technique de 1781ectricit6. It makes reference to the objections raised by J. Huse on the proposed SC28A(Sec)47 

explanation of interface devices. During the discussion period, Mr. Meyer projected on the screen a chart showing 

that the present situation in the EDF distribution system makes possible the occurrence of temporary overvoltages 

of 1.5 per-unit for 5 seconds. 

Cascade Bibliography - September 1992 
Rouiet, J.P. - La coordination de i%oiement et ie concept de 'Categorie de surtension' en b

tension. Proceedings, UE Workshop on Surge Arresters, Paris, March 20, 1992 (In Frenc

AUTHOR'S ABSTRACT 

(Adaptation from the French text) 

AUTHOR'S CONCLUSIONS 

(Adaptation) 

This is a two-part presentation discussing the IEC In the future, one may expect a less r

664 publication and its table of overvoltage organization of protection against overvoltages, m

categories, then the work of IEC TC64 to adopt and possible by regrouping equipment into categories 

amend the concepts initially proposed in IEC 664 will make possible the application of var

protective methods appropriate to the desired ser

continuity. 

Application of surge arresters will be the wor

SC37AltryG3. Let us wish them success, an

fruitiui cooperation among Committees 28A, 3

and 64. 

REVIEWER'S ANNOTATIONS 

In the discussion of the Overvoltage Categories concept, Roulet points out unresolved questions relating to cas

applications, potential rise of ground references, unwanted neutral-ground connection, and the need for end-of

indication. 

References are made to the forthcoming cooperation between SC28A and TC64iWG3. 

Cascade Bibliography - September 1992 
Rousseau, A., Lafon, G., and Maipike, F. - Les parafoudres face aux normes. Proceedings, 

CEM 92, 6th International Workshop on EMC, Lyon-Ecully, France, June 1992. (In French) 

AUTHORS' ABSTRACT 

(Translated) 

Surge-protective devices for low-voltage systems are 

sophisticated devices which must be defined by 

several parameters: protection level, energy handling 

capability, end-of-life behavior, standby current, 

association with other devices of the same type, etc. 

This paper reviews currently applicable French 

standards and compares then to foreign standards. A 

review is presented of international activities, in 

particular studies on coordination of protective 

devices. 

AUTHORS' CONCLUSIONS 

(Adapted from final discussion) 

The problem remains of the coordination between two 

SPDs. The cases studied so far generally involve 

ZnO varistors. However, many other components or 

module exist that raise even more problems of 

coordination. It seem therefore difficult today to 

coordinate products from different manufacturers, 

without prior testing or simulations. Thus, it is 

easier to rely upon coordination tests performed by a 

manufacturer on its own product line. 

REVIEWER'S ANNOTATIONS 

The paper presents a snapshot of the status of standards in France, Belgium, Germany, and the USA, underlining 

the differences in philosophy and postulated threat waveforms. Several unresolved questions are identified that merit 

consideration on the international level, such as protective level, energy handling capability, failure mode, standby 

current, coordination. 

An example is given of successful coordination between a gapped varistor and simple varistor with an 8/20 ps wave 

and as little as 5 m separation, but no information is provided for coordination with the 101350 ps wave which is 

cited elsewhere in the paper. 

Cascade Bibliography - September 1992 
Scuica, V. - Appiicatzon ojmodem surge suppressors in low-voltage power installation netwo

Institute for High Voltage Research, Uppsala University, UURIE.-250-86, 1986. 

(Not available at press time) 

AUTHOR'S ABSTRACT AUTHOR'S CONCLUSIONS 

REVIEWER'S ANNOTATIONS 

Cascade Bibliography - September 1992 
S-~cu*ka, V. - EM1 Control in Low-Voltage Power Installations. Proceedings, 1987 EMC Ziirich 

Symposium, pp 429-434. 

AUTHOR'S ABSraACT 

(Excerpts from 'Introduction') 

According to Martzloff 131 the impedance of low 

voltage power installations in general is in the range 

of 50 to 100 0, therefore, the expected minimum 

current through the secondary suppressor must be in 

the range of 10 to 40 A until the gap of the primary 

surge arrester will be able to break down. It would 

therefore be of advantage, if the surge impedance of 

the installation circuit is not too low. Our measurements of impedances in low voltage power installations in different stxuctures have shown, that the 

impedance may decrease by a factor of up to three by 

moving from a distant point in the instaiiation to the 

main power distribution box of the structure. 

Approaches have been made to artificially increase 

the impedance of low voltage power circuits by 

applying femte cores in coils of power network 

filters. It is unfortunately often forgotten that core 

saturation currents for the core dimensions normally 

used usually are very low, much lower than usual 

surge currents in the line. The most safe way in 

increasing the impedance of the particular installation 

line segment is to separate the surge suppressors by 

a properly designed physical line or a noise 

suppression transformer. 

n-e no& Sf iGtepatie-dl - =j! 

recommenclati~fis reg=r&ng the =pp!iat:~n ~f =-- *sY 

suppression in particular in industrial power !ks Ilnn 

installations and the need of standardized equipment 

testing procedures and test-level specifications have 

been recognized. An overview of the situation of 

today has been given in a paper by Martzloff [8]. 

In the following we shall present and discuss our 

experimental and theoretical investigations made on 

an artificial low voltage power installation segment 

and on ordinary low voltage power installations in 

different structures. The investigations have been 

performed in order to determine the values of the 

basic electric circuit parameters and to deduce the 

electro-physical relationship for different components 

and circuit parameters of a modem low voltage 

power installation. 

AUTHOR'S CONCLUSIONS 

(Excerpts) 

Spark gaps should only be used as overload 

protectors of varistors, or as insulation-coordination 

protectors where AC-short circuit follow currents are 

not to be expected. In a 380V AC power system the 

varistor V' - type should be installed in the main 

power distribution box in accordance with the 

established practice. In general, if there are no 

special reasons, additional varistors of type V' are not 

necessary to be installed in subdistribution boxes. 

Further more, varistors of type V' in the 

subdistribution boxes would draw high surge currents 

along the connection lines between the boxes. This 

could be a disadvantage from the point of interference 

suppression. The secondary varistors V2 should be 

installed near the sensitive equipment. Preferably, 

such equipment should not be connected to the power 

line near the main distribution box. A long 

installation line may be of advantage. 

A reasonable value of the nominal voltage for a 

secondary varistor of - type is between 620 and 

750 V DC and the diameter between 14 and 24 mm. 

Refening to the Table 4, only a minor part of the 

total surge current will pass through the installation 

line and the varistor v. An optimized protection of 

the equipment, regarding the common mode and the be-.. -.--- ---I- ---I .--- 6,-Y GI~ muuc VOIL~~C: surgs, is vbbined by using 

a xt =f +&= v&-;stars [8]. 

surge valbge acress the v&stcx V2 ha z 

appreciable longer rise time than the original surge at 

varistor V'. For an injected lightning current of 1/50 

us, the dominant frequency of the voltage surge 

across V2 will be in the range of 10 kHz. This 

makes it possible using an additional power 

transformer, e.g., an isolation transformer, which 

significantly reduce the surge entering into the 

protected equipment. We may also conclude that 

equipment with a power transformer is very suitable 

to be efficiently protected using a set of secondary 

varistors. 

REVIEWER'S ANNOTATIONS 

Paper reports computations with EMTP and makes reference to measurements, presumably reported in Scuka, 1986 

for a cascade of two varistors. 

The impinging surge is a current of 1/50 ps waveform - a steep front. 

Paper seems to encourage varistor at end of branch circuit to have hgher voltage rating than varistor at service 

entrance. 

Cascade Bibliography - September 1992 48 
Smith, S.B. and Standler, R.B. - The Effects of Surges on Electronic Appliances. Z

Transactions PWW-7, N0.3, July 1992, pp 1275-1282. 

AUTHORS' ABSTRACT AUTHORS' CONCLUSIONS 

With the dramatic increase of electronic equipment 

and appliances being used in homes, the topic of 

power quality and its relationship to appliance 

reliability has recently become very important to both 

the utility company and the consumer. We subjected 

a total of 16 different clocks, television receivers, 

microwave ovens, and dc power supplies to three 

different transient overvoltage (surge) waveforms 

~li* arq!ihd-e k.bvm 0.5 and 6 kV. All of these 

devices were operating from the ac supply mains 

when the overvoltage was applied. The switching 

power supplies and television receivers were damaged 

with surges between 4 and 6 kV. Three of five 

models of digital clocks were upset (temporary 

malfunction) with surges between 1.6 and 6 kV. 

Tests of 12 different models of consumer appIi

and two switching power supplies showed 

television receivers and switching power suppli

vulnerable to damage by surges with peak 

circuit voltages between 4 and 6 kV. 

protection is desirable for these vuln

appliances. However, some of the appliances i

project were not vulnerable to damage by a li

number of surges. Further research, leadi

archival papers, is recommended on both (

effects of surges on appliances and (2) techniq

mitigate damage and upset by surges. 

REVIEWER'S ANNOTATIONS 

Two noteworthy paragraphs in the discussion presented by the authors read: 

The results of this research show that the conventional wisdom that electronic 

appliances are easily damaged by surges with a peak voltage of a few kilovolts 

may greatly exaggerate the effect of surges on modem consumer appliances. 

If manufacturers include metal oxide varistors inside appliances in order to 

prevent damage or upset, they should consider using varistors rated for twice the 

normal nns voitage. This reiativeiy iarge conduction voiiage wiii de it 

possibie io instaii a secondary arresters iipsiram from the zipphiice &z: 5s 

g- . . OW - 3 Cwrumauun -----I:--.:-- ... :*I- r -- .-... a- +La --- WIUI die valiatvm uw~uG urr ep&--. 

The conclusions and discussion remarks point out that the quest for very low protective voltage, such as 330 

400 V may indeed be an exaggeration of the need for protection. The immunity to surges as high as 1.5 kV 

in the paper may be the result of inherent immunity of the power port circuitry, or the result of some b

protection at the input. In either case, the authors have provided significant evidence that relatively high prot

levels at the point of load connection, a requirement for a successful cascade, should not be viewed as a thr

the appliances. 

Another anecdotal consideration is that the highest percentage of reported failures (50%) cited in the paper in

TV receivers and VCRs. The authors suggest that this finding may be related to the high cost of these appli

more likely to be reported than the failure of a clock. This reviewer suggests that a possible contribution to th

percentage may be that TV equipment is a two-port system (power port and communications port), compare

single-port clock, raising the issue of the need for special protection of two-port devices. (In the tests repor

the authors, only differential-mode surges were applied to the two-conductor line cord, no mention is made 

ggps ad rpfprp~cp, ~&qg~. ~f sips! pa;) 

Cascade Bibliography - September 1992 
Standler, R.B. - Protection of Electronic Circuitsfrom Overvoltages. Wiley-Interscience, New 

York, 434 pp, 1992. 

Excerpts from cover flap abstract: 

Protection of Electronic Circuitsftom Overvoltages collects and logically presents the information in this field ion 

one convenient text. At the same time, it provides practical rules and strategies for the design of circuits to protect 

electronic systems from damage by transient overvoltages. These rules are, as often as possible, related to physical 

laws rather than traditional rules of thumb. ... Because many of these circuits operate from ac supply mains, 

protection of equipment operating from the mains is also discussed. ... 

Reviewer's annotations: 

The book contains 24 chapters organized in four parts: 

Symptoms and threats 

Protective devices 

Application of protective devices 

Validating protective measures 

The following are excerpts from Chapter 19, under the heading of "Coordination of Protection" page 294: 

. . . In most hybrid protection circuits, shunt devices with smaller clamping voltages are installed downstream, nearer 

the equipment to be protected. Some series impedance is installed between each pair of shunt protective devices 

to provide proper coordination. . . . 

... But for overvoltages with durations of a few milliseconds, it will be difficult to insert an adequate series 

impedance between shunt protective devices and still maintain normal operation of the load. . . . 

.. . One solution to the problem of coordinating multiple varistors on the mains is to reverse the normal order of 

devices. Place the varistor with the smallest value of V, at the secondary arrester. Varistors downstream would 

hzge s;ighi;y krger v&Des of '"T,. ( n-ame iai ex+&@e foiiowsj 

. . . It is .n~&ias &ff;.sdt !a cmr&&= ==!tip!= ~3q-e pr&=t;.ve &\pic= .a*&g you r+ai= of H~+gi;er, 

vou can't even try to ~mrdbatt varistors that zre hiddez .r?h I chssis ldpcs ye= haw &m? the:! . . . 

Cascade Bibliography - September 1992 
S'tanaier, R.B. - Coordination of Surge Arresters and Suppressors for Use on Low-Volta

Mains. Proceedings, 1991 Zurich EMC Symposium, pp 5 17-524. 

AUTHOR'S ABSTRACT AUTHOR'S CONCLUSIONS 

A secondary arrester is used at the point of entry of 

the mains into a building to provide protection from 

severe surges, such as direct lightning strikes to 

overhead mains. A surge suppressor is used at the 

wall receptacle to protect vulnerable electronic 

equipment from damage by transient overvoltages. 

This paper discusses the sharing of current between 

the anester and suppressor during surges. Results of 

both a theoretical analysis and laboratory experiments 

are reported. Conventional practice is to make the 

conduction voitage of suppressor. it is shown that it 

is ktir tu design the arrester with a smaiier 

conduction voltage than the suppressor, in order to 

obtain better coordination, better electromagnetic 

compatibility, and lower cost. 

Good coordination of two metal oxide varistors c

be obtained by specifying that the anester have 

- lower conducting voltage than the suppressor. A

example for use on mains with a nominal voltage 

10 V nns is to us (1) an arrester with VH - 240 V a

a diameter of 40 mm and (2) a suppressor with V

390 V and a diameter of 14 mm. It is possible th

future research will show that suppressor varist

with a diameter of 10 mm are suitable for use in t

well coordinated method. 

REVIEWER'S ANNOTATIONS 

Computations are made with only resistance of wire between cascaded devices, no inductance. 

Measurements as well as computations are reported for several combinations of service entrance arresters (650, 17

150 V) and branch circuit end suppressors (130, 150, 250 V). 

The conclusion that good coordination can be achieved with lower voltage clamping at the service entrance is we

founded but does not take into consideration the reality of uncontrolled low levels of clamping from billions 

installed TVSSs ad built-in sgpprescn.rr,. 

Cascade Bibliography - September 1992 
Standier, R.B. - Caicuiations of Lightning Surge Currents Inside Buildings. Proceedings, IEEE 

Intemional EMC Symposium, August 1992, pp 195- 199. 

AUTHORS'S ABSTRACT AUTHOR'S CONCLUSIONS 

This paper describes the distribution of surge currents 

inside a building during a direct lightning strike, on 

the basis of numerical simulations of building wiring, 

various loads, and five different combinations of 

metal oxide varistors connected inside the building as 

surge arresters and surge suppressors. The 101350 

ps wave with a peak of 20 kA, which is widely 

accepted as a simulation of current in a direct 

lightning strokes, is used as the source. The network 

Inside the building is modeled as eight branch 

circuits, each with a different resistive, capacitive, or 

inductive ioaci and each wiih a different iength. Tne 

results of this modeling is compared with the 8/20 

and 1011000 standard surge test waveforms. It is 

shown that the surge test waveforms of ANSIIIEEE 

C62.41 have a peak current and duration that are 

both too small to represent the effects of a direct 

lightning strike to the mains. Instead of revising 

C62.41 to include larger stresses for the environment 

inside a building, it is urged that standards specify 

maximum allowable values of peak surge current and 

rates-of-change inside a building. Coordinated surge 

arresters and suppressors should be used to keep 

surge currents inside a building within the specified 

limits. 

Computer simulations of simple arrangements of 

branch circuits, loads, and one or two varistors show 

that surge currents inside buildings during a direct 

lightning stroke to the mains have a larger peak 

current and longer duration than maximum surge test 

levels recommended in ANSIDEEE C62.41-199 1. 

The discussion of this paper recommends that we do 

not continue to specify surge currents that might be 

found inside buildings. Instead, it is recommended 

that limits be set on the maximum permissible surge 

current inside buiidmgs by considering pnnc~ples of 

electromagnetic compatibility. Coordinated surge 

arresters and suppressors should be used to keep 

surge currents inside a building within the specified 

limits. Such an approach is an extension of the 

Lightning Protection Zone Concept of Hasse and 

Wiesinger in Germany. 

Cascade Bibliography - September 1992 
Suingfeiiow, M.F. and Stoneiy, B.T. - Coordination of Surge Suppressors in Low-Voltage 

Power Circuits. Proceedings, Form on Surge Protection Application, NISTIR-4657, Au

AUTHORS' ABSTRACT 

This paper reports on a theoretical and experimental 

study on the coordination of metal oxide varistors on 

an indoor low-voltage power system. The system 

studied was a 120-volt three-wire power line, 

equipped with phase, neutral and ground conductors. 

Metal-oxide varistors were applied at three points on 

the system. These were at the service entrance, at 

the distribution panel and at the load. Total line 

length studied was 30 meters (100 feet), with the 

distribution panel being located at the central point. 

When unidirectional surges typical of lightning were 

applied at the service entrance, both experimental and 

theoretical studies showed similar results. Namely, 

removal of protection at either load or distribution 

panel resulted in unacceptably large oscillatory 

voltages. Best load protection was achieved with 

movs in all three locations. Distribution of surge 

current between movs in three locations is shown to 

be good for both low and high surge currents. 

Coordination of protective levels was shown to be 

achieved, even with long surges typical of lightning. 

AUTHORS' CONCLUSIONS 

The following conclusions may be reached regar

the protection of loads connected to low-voltag

power systems inside buildings when subjecte

external transients: 

1) A serviceentrance arrester or suppr

diverts the majority of surge current 

from the building wiring. 

2) The best protection is always obtained w

suppressors are located on internal wiri

both distribution panels and at the load

3) The lowest-rated mov does not have t

located at the service entrance, but ca

effective when applied at the load. 

4 Testing with the new ANSI C6

Category C3 combination wave gives re

in reasonable agreement with those exp

from more realistic lightning w

However, the energy deposited in mov

this wave is much lower than expected 

lightning. 

REVIEWER'S ANNOTATIONS 

Cascade Bibliography - September 1992 
Suingfeiiow, M.F. - Fire Hazard of Surge Suppressors. Proceedings, Power Quality 

Conference, Anaheim Ca, September 1992. 

AUTHOR'S ABSTRACT AUTHOR'S CONCLUSIONS 

Surge suppressors can and do catch fire. One or two 

recent nationally-publicized incidents show that 

serious property damage and injury can result from 

such suppressor fires. The popular and much 

repeated theory of how this occurs is that suppressors 

degrade in service when exposed to transients or 

power disturbances. This degradation eventually leads 

to suppressor failure by overheating. The author 

shows in this paper that this theory is completely 

wrong. Suppressors removed from service throughout 

the E.3. and Zanada show no signs of degradation. 

Siipprtx~r damage from overheating can aimost 

always be directly traced to power-frequency voltage 

overstress, usually resulting from building wiring 

faults. A laboratory test which simulates these faults 

is proposed. Preliminary test results on some of the 

most popular commercially-available surge 

suppressors show that many can be set on fire in a 

reproducible way. It is concluded that internal 

protection against overheating is required to ensure 

suppressor safety and that safety agency approvals 

should include fire hazard tests. 

REVIEWER'S ANNOTATIONS 

Contrary to popular myth, field data shows that surge 

suppressors containing metal oxide varistors do not 

degrade in service. 

All suppressors are, however, exposed to rare 

incidents of severe power-frequency overvoltage 

caused by power-line accidents, such as broken 

neutral conductors. These incidents appear to be 

increasing in frequency due to the more widespread 

adoption of modular furniture with integral wiring. 

The many connectors used in this form of electrical 

distribution appear to be very prone to wiring 

problems. 

The overvoltages resulting from broken conductors 

are very large (1.5 to 2 times normal voltage), may 

be sustained for many minutes, and can cause 

suppressors to overheat internally. 

Products equipped with overcurrent fuses or magnetic 

circuit breakers may catch fire in rare cases. This is 

true for those having both plastic and metal housings 

and components rated for both 130 V and 150 V. 

A fire hazard test, similar to that described in this 

paper, is proposed to be added to safety agency tests 

for surge suppressors and similar products. 

Cascade Bibliography - September 1992