Paper presented at PQA'92 Conference, Atlanta, 1992 

Significance 

Part 8 – Coordination of cascaded SPDs 

The early nineties were marked by the emergence of concerns about the coordination of cascaded SPD as the 

concept of “Whole-house protection” was gaining popularity. However, it appeared that the selection of service 

entrance SPDs and point-of-use plug-in SPDs was not an integrated process, hence some possibility that the 

expected coordination might not be achieved. On the other hand, if a well-designed combination could be 

implemented by a single authority responsible for the selection of the two devices, then the competing requirements 

for these to devices might be accommodated. 

The service entrance SPD is generally selected from the point of view of the utility, and therefore tends to be a 

rugged device with relatively high limiting voltage because of the desire to have a conservative maximum continuous 

operating voltage (MCOV). On the other hand, the point-of-use SPDs, for those purchased independenly from the

service entrance SPD, are generally designed to offer the lowest possible limiting voltage. This relationship makes 

coordination difficult. If the two devices are selected with the same limiting voltage (and thus comparable MCOVs), 

then the inductance separating the two devices can have a chance to decouple the two devices sufficiently to achieve 

a satisfactory coordination. The inductance of the wiring between the service entrance can add some voltage drop 

between the two devices, so that an acceptable degree of coordination can still be achieved if the two device have 

equal limiting voltages. The redeeming effect of the wiring inductance is of course dependent upon the waveform of 

the impinging current surge, as well as the length of the branch circuit. 

In this paper, the relationships of these parameters are explored by numerical simulations. Cross-validation of 

simulation and measurements in actual circuits for typical applied surges was demonstrated in earlier papers so it 

was not repeated here. 

Filename: Coordination 1992 
Franpis D. Martzloff 

National Institute 

of Standards and Technology f 

Gaithersburg MD 

Ar.."*....d - tlUJbrtL4.4 ba-k- -> 'Thik-aT par-Ams a 

successfl coordination of cascaded surge-protective devices 

include the relarive volrage clamping of the tw~ devices. 

their elecnical separation through wiring inductance, and 

the actual wave$onn of the impinging surge. The authors 

euunine in detail the implications of the situation resulting 

from the present uncoordinated qpplication of devices with 

low clamping voltage a the end of branch circuits and 

de""k"&" .*k+k +@LWT ch.qiEg v&qe &. :he scT"-k-e 

emance. As an altendve, several options are oflered for 

discussion, that might result in gective, reliable 

implernenfation of the cascaded protection concept. 

Ccordinating cascading surge-protective devices is a 

concept whereby two devices are connected at two different 

points of a power system, with some physical, but mostly 

electrical, separation (inductance) between the two points. 

The upstream device is designed to divert the bulk of an 

impinging surge, while the downstream device, close to the 

equipment to be protected, is intended as a fmal clamping 

stage, including surges generated within the facility. 

Successful coordination is achieved when the heavyduty 

upstream device does indeed divert the bulk of the surge, 

rather than letting the downstream device attempt to divert 

exmshe mO~riil. of &e SSUrge c-ni. TO &&gui& 

between the two surge-protective devices (abbreviated as 

'SPD'), the heavy-duty, upstream device will be referred to 

as 'arrester', while the lighter duty, downstream device will 

be referred to as 'suppressor'. The basic and critical parameters for successful coordiition of the arrester-suppressor 

cascade include the relative voltage clamping of the two 

devices, their electrical separation through wiring h&ciC~u*, md '&e xtui -w-B Y.efO- of 'he hphging surge* 

The prime objective of a cascade anangement is to 

maximize the benefit of surge protection with a minimum 

expenditure of hardware. Another benefit of a cascade is 

the diversion of large surge currents at the service entrance, 

so that they do not flow in the building, thereby avoiding 

side effects (Martzloff, 1990). * 

* C&&m.. oreprese.aed nr (4~tb?, Dae) r&er thnn nr n~"?~,hcred 

item, and are listed a&habeticaliy in the appmded bibliography. 

7he bibliography ako includes item not cited in this paper, as an 

indication of the increaring level of inrerest in tfi subject. 

Technology Administration, U.S. Department of Commerce 

Jih-Sheng Lai 

Power Electronics A-pplications Center 

Knoxville TN 

Tine idea of a two-step protection has been expio

many authors over the last two decades, as can be see

the bibliography included in this paper. Starting 

different premises, and with changing opportunities as 

technology evolved, these authors have reached conclus

that are sometimes convergent, and sometimes diverg

giving the appearance of contradictions. 

In two previous papers (Lai & Martzloff, 1

?vrhdoff 2k hi, iXi j, we have examined ine simpie 

of a two-wire, single-phase circuit where each of the 

SPDs is connected between the high-side of the line and 

low-side (neutral or grounding conductor), showing 

numerical examples the effect of three signifi

parameters: relative clamping voltage, separation, 

impinging waveform. When these three parameters are 

taken into consideration, many of those earlier diver

wiic1-~ioii~ iiv ionger appear contraaiicrory. Iiather, 

become for each case a limited view of a consistent set 

changes over the complete matrix of the possible ranges 

the three parameters. 

The two-wire circuit is a simplification applicable to 

U.S. practice for residential service, which is gener

single-phase, with a mid-point neutral bonded to the l

ground at the entrance to the building. In some count

a e$<6 ifi pt&.ce ',f pun&g: 

neutral is grounded at the distribution transformer but is 

"mounded at the -ice enme a we!!. Wrrrll, 

installation includes a distinct 'protectiveearth' condu

that is bonded to the local earth ('ground' in U.S. Engli

not to the neutral. In contrast, U.S. practice is to bon

local ground, at the service panel, both the neutral and 

'equipment grounding conductor' that serves the s

PL3+a**'e 'he Liim*~&v-e -> ifi EuTo

practice. 

This difference in the utility ,punding practice 

implications on the implementation of a cascade in 

European context, where a service entrance arrester is m

likely to be connected between the incoming lines 

protective earth, while end-of-circuit suppressors are m

iiiceiy TO be comecteci between he and neutral. l

;ilig2iiiSiii is iiioie winpiex stan ibe simpie iwo

cascade corresponding to the U.S. practice, and we prop

a model that takes into ~~idepAnz thismrp mq

circuit. In the unbonded neutral connection scheme, th

is a greater separation between the two cascaded devices 

thereby the likelihood of successful coordination can 

expected to increase. 

&niribuiions of iho i-iationd insiiiurc of Standards and iec-moiogy are not subject to U.S. Copyright 
It is one thing to design an approach based on opthum 

coordination where all the parameters are under the control 

of the designer. Such an opportunity existed in utility 

systems implemented under centralized engineering. It is an 

altogether different challenge to attempt, after the fact, 

coordinating the operation of surgeprotective devices 

connected to the power system by diverse and uncoordinated 

(and uninformed) users. For example, excessively low 

clamping voltages may be a threat to long-tenn reliability of 

varistors (Markloff & Leedy, 1987; Davidson, 1991). 

Our effort in promoting a coordinated approach may 

come too late for the de facto situation of having millions of 

suppressors in service with a relatively low clamping 

voltage. This situation will impose an upper limit to the 

clamping voltage of a candidate retrofitted arrester. 

Therefore, close attention must be paid to the selection of 

the reiative ciamping voitage of the two devices, in view of *L- ---n:A-- -----:-----a- c-- --L LUG c;uruuc;ug rajuucucuw rur pcrlulluarcu uuucr surgc 

conditions - a successful cascade - and reliable withstand 

for temporary power-frequency ovemoltages. Nevertheless, 

coordination might still be achieved through understanding 

the possible tradeoffs; in the future, users could avoid the 

pitfalls of poor coordination or the disappointment of 

implementing protection schemes that cannot provide the 

hoped-for results. 

Finally, we propose for discussion among utilities and 

manufacturers a diffkent approach to the selection of the 

service entrance arrester: a one-shot expendable device that 

would protect the installation against rare, but catastrophic 

sustained temporary overvoltages at power frequency. 

c: ---- 1 --A - LA- AK--l-ax a T -2 1 Ml\ :IL--&- rrgurca I auu A, uulu (lv~aru~urr OL ~*ll, 177~)~ IIIIWLI~G 

the impact of the relative voltages on the energy sharing 

between the two devices. In these two figures, a plot is 

shown of the percentage of the total energy dissipated in the 

suppressor, as a function of the distance separating the two 

devices, for various combinations of clamping voltages, and 

for two postulated waveforms. In the plots, H, M, and L 

correspond respectively to a high, medium, and low voltage 

rating, in the context of a 120-V rms circuit application. 

As long as the only postdated impinging wavefonn 

remained the classical 8120-ps current surge (Figure I), 

good coordination could be expected, even with an arrester 

clamping at a voltage somewhat higher than the clamping 

v&ge of the sqqrmwr- ghg~g~phy wm ~rpi~~ 

in the development of several insulation coordination 

documents of the International Electrotechnical Cornmission (IEC) in the last decade (Crouch & Martzloff, 

1978; Martzloff, 1980; IEC 28AvSA/Las Vegas109, 

1983 and its later modifications). 

5 10 20 40 

DISTANCE BETWEEN ARRE!STER 

AND SUPPRESSOR (m) 

Figure 1 

Relative energy deposited by a 3kA. 8120-p~ wave 

in the suppressor for arrester-suppressor combinations 

of 250 V (HI, 150 V (MI, or 130 V (L) ratings, 

as a function of separation distance 

However, if, in accordance with new descriptions of th

surge environment, we apply a surge with longer waveform

such as the 1011000 ps of ANSUIEEE C62.41-1991, or th

German 101350 ps (Hasse et al., 1989), then coordinatio

cannot be obtained if the arrester has a higher clampin

voltage than that of the suppressor (Figure 2). 

5 10 20 40 

DISTANCE Bl3WEN ARRESTER run c~ ~asacccna IA N." -r r -" p,, 

Figure 2 

Relative energy deposited by a 220A, 1011 000-ps wave 

in me suppressor for arrester-suppressor combinations 

of 250 V (HI, 150 V (MI. or 130 V (L) ratings, 

as a function of separation distance 
A partial remedy might be expected in a scenario where 

the arrester and the suppressor would be specified with the 

same nominal (rms) voltage. The arrester would have, by 

definition, a larger cross-section than the suppressor, in 

order to fulfill its mission of prime dissipator of energy. 

The lqer cmss-section ~~1tc ia a lower cwrrent de~~ity, 

lowering the clamping voltage corn-pared with that developed 

for the same current into the suppressor experiencing a 

higher current density. Thus, we could expect some relief 

of the 50%-50% division of energy shown in Figure 2 for 

two &vices of equal voltage rating. 

To quantify this expectation, we have modeled a 40-mm 

diameter varistor rated 150 V rms, and used the model 

defined in our 1991 ,paper for a 20-mm diameter vziEt?r. 

Figure 3 shows the I-V characteristics for the two devices. 

Starting with the same voltage at 1 mA (equal by definition 

of the nominal voltage), the 40-mm varistor indeed provides 

a siightly lower clamping voltage than the 20-mm varistor, 

for currents above 1 mA. Conversely, for the same voltage 

(parallel connection), the plots show that in the 200-A range 

(the value selected for the 10/1000-ps wave in the 1991 

tests), there is a UX)/UX) ratio in the currents flowing in the 

two devices. In the 3-kA range (the value shown in 

ANSUIEEE C62.41 for the 8120-ps wave), the 2000/UXK) 

ratio is practically the same. 

-1 MI 0.1 1 10 100 10~) loo00 - Qnent (4 

Figure 3 

Cuwe-'tting for the nominal I-V characteristics of 

1504 rated varistors. with diameters of 20 and 40 mm 

mequai sharing of the current for two paraiieiconnected devices with vertically offset characteristics is 

~en=_11y Gew& &&lp ~ ,nG&&?q .;)pp&cq 5)- 

when the objective is to increase the energy handling 

capability of the two devices comected at the same point. 

In the present case, however, the objective is opposite: a 

very unequal sharing is sought to effect coordination 

-between the two devices. 

Figure 4 shows a cascade using the 40-mm varistor as 

service entrance arrester and the 20-mm varistor as surge 

suppressor. me fig!* dsc &curs t!~e mxep?s cf !x.a?k;; 

categories (A and B) defined in ANSUIEEE C62.41-1991. 

Figure 4 

Configuration of a two-stage cascade, with bath devi

connected between line and neutral conductors 

The arrester and the varistor are separated by a dis

d, justifying the transition frnm Gtegcry E ?.f ~e see

entrance to Category A at the receptacle. 

In the numerical examples and computer-generated 

illustrated below, we selected only one value, 10 meters

the distance separating the arrester and the suppressor

our referenced 1 99 1 papers, we gave examples of dist

ranging from 5 to 40 meters, as well as plots 

measurements of the surge currents in an actual cir

The correspondence k~~een he rngdebg res-d's a& 

experimentk measurements was demonstrated in t

papers. Therefore, for the similar combination of de

discussed here, we can use the same numerical model 

appropriate modification of the device parameters), and 

limit ourselves to modeling - precisely the point of ha

developed a valid model. 

Figure 5 shows the computed current division betw

arrester (I:) and suppressor (Id for a 3-lr4, 8!3np W

impinging upon a cascade of two varistors, 40 mm fo

arrester and 20 mm for the suppressor, each rated 15

Figure 6 shows the division for the same cascade w

220-A, 10/1000-ps impinging wave. 

Figure 5 

Division of the current between arrester (I,) 

and suppressor iizi for a ? 50-ii, 40-mmi20-mm casca

10- separation, with a 3-kA, 8120-ps impinging sur
Figure 6 Figure 8 

Division of the current between arrester (Il) and Division of the power between arrester (PI) and suppresso

EE~~DCEOI !!2! fey e ? 5°K ~dn-mr??!X!-mrr! rezcade, :P2) fw s ? 50=v, 40=m7:!2O=mm ccsc&e, ? O m sepzmtk

10 rn separation, 220-A, 1011 000-ps impinging surge with a 220-A, 1011 000-ps impinging surge 

Tnqection of these two figures also provides qualitative 

insight on the behavior of the circuit. For the 8120-ps 

wave, the inductance of the 10-m length of wire retards the 

rise of current in the suppressor during the first part of the 

surge, but tends to maintain the current in the suppressor 

even after the arrester current has decayed to zero. For the 

1011000-p wave, the wiring contributes a significant 

difference in the currents only during the rapidly-changing 

period - the front of the wave - with the difference in the 

tail solely attributable to the difference in cross-section 

between the arrester and the suppressor. 

Because of the quasi-constant voltage across the varistor 

&&-kg +&= p&-g= =..r=fi:, the -P, hhsvkr qpq is t&= 

pwer @a& of Fists 7 and 8 which show the power 

dissipated in each device, respectively for the 8120-ps surge 

and the 10/1000-p.s surge. The corresponding energy was 

obtained by integrating the two power curves. The results 

are shown in Table 1, which also includes the results for the 

original 20-mml20-mm cascade. 

Figure 7 

Division of the power between arrester (PI) and 

suppressor (P2) for a 150-V, 40-rnrn120-mrn cascade, 

10 rn separation, 3-kA, 8120-ps impinging surge 

Table 1 

Distribution of deposited energy in arrester and suppresso

20mm120mrn and 40mrn120mrn cascades, 10 m 

separation, 8120-p~ and 1011 000-p~ impinging surges 

th +I 11 Waveform I ~evices l~rresterl~uppressorI suppressor 11 

I (joules) 1 (joules) I(% of totallll 

Predictably, the 8120-p waveform produces a goo

coordination, for a U)-d20-mm cascade as well as for 

#mm/20-mm cascade. In fact, the only differen

between the two is a fraction of joule, which is not show

in the table where the values have been rounded off. 

When postulating a 1011000-ps waveform, the 40-m

arrester indeed diverts slightly more current than the 20-m

suppressor, as shown in Figure 6. However, when th

energy levels are compared (see Table I), the improveme

obtained by changing from 20-d20-mm to 40-mmlU)-m

cascades is only a small reduction in percentage of the tota

down to 40% from the 48% of the original 20-mm120-m

cascade. 

The small 8% advantage of the 40-d20-mm casca

is likely to be lost when the statistics of possible toleranc

for the two devices are considered. Figure 9 shows t

effects of combing the relative tolerance deviations fro

nominal values, the same nominal values that were used 

computing the advantage of the #mm/20-mm cascade ov

the 20-mm/20-mm cascade. 
Arrester Arrester 

High Low - 

Suppressor Increased 

High 

Suppressor Decreased 

Low 

Figure 9 

Advantage of 40-mm120mm cascade 

over 20inm120-mm cascade 

For any cascade where the tolerances move in the same 

direction (50 % of the cases), the advantage remains at 8 % . For combinations where the tolerances make the arrester 

lower than the suppressor (25 56 of the cases), the advantage 

is improved. For combinations where the arrester is higher 

than the suppressor (25% of the cases), the advantage is 

decreased and may be completely wiped out. Thus, the 

hoped-for improvement fbm the lower current density 

might not be very substantial. 

In polyphase systems, or even single-phase systems, the 

bndhg kWe.3 =et_d md P-& @OQ=~) my & ,tc~e 

distance from the arrester - at the limit, one might 

consider a system with ungrounded neutral or no neutral. 

In such cases, the arresters are likely to be connected line 

to-ground. Yet, the majority of suppressors are likely to 

be connected iineto neutral - the two conductors feeding 

the power port of the sensitive ioaci in need of surge 

protection. Indeed, some countries or some suppliers object 

tc my ef m-a&iGn far gqeepI%4e>+e 

installed at receptacles or incorporated in connected 

equipment. Thus, the simple case treated in our 1991 

papers, with the two devices (arrester and suppressor) 

diverting the surge to the same neutral conductor, may be 

more complicated - perhaps with the welcome effect of a 

greater separation of the two devices. 

Figure 10, from (Rodet, 1992) shows a typical conn&don & agr- f"r sY*m wi& a proktive 

earth distinct from the neutral. This configuration could be 

modeled for the complete circuit; however, as an illustrative 

example and for comparison with the case of Figure 4, we 

have simplified the circuit as shown in Figure 11. The two 

varistors have the same voltage rating (150 V). Of course, 

in a European context of a 230/400-V three-phase system, 

the modeling should be done with varistors of appropriate 

ratings, say, 320 V. The generic conclusions reached for 

the example of the typical single-phase 2401120-V in use in 

the U.S. can be extended to the 2301400-V situation. We 

interpreted the configuration of Figure 10 and postulated for 

the coupling of the impinging surge as a commo

scenario, that is, a surge coupled by earth curren

inductive coupling into the loop formed by 

conductors and earth. 

Soiircer ;fioiiiez, i 5923 

LEGEND 

RB: Earth ground at the distribution transformer 

1 : Service entrance panel 

2: Sub-panel with feeders for branch circuits 

3: Local earth electrode (PE) 

4: Arresters connected to local earth (PE) 

5: Connection of arresters to PE 

6: Single-phase equipment that may contain an 

Figure 10 

Typical threephase !~l.sts!!atIw with pntnF+;ye 

separate from the system neutrd 

Figure 11 

siiipiifi& m&iici &,.iv& from 

the three-phase system of Figure 10 

Inspection of this circuit model reveals that sep

between the two devices of the original cascad

longer the simple length of two-conductor wire. 

pinging surge, postulated to be common mode, 

revisited for such a power system configuration

two induced surge currents were exactly equal (t

common mode) and the two arresters were ident

voitages produced at points L and N by the surge 

flowing in each of the arresters would be equal

there would be no stress imposed upon the sup

connected line-to-neutral at the end of the branch 
For a voitage m appear between L and N, we must 

postulate unbalanced currents in the conductors L and N 

and a tolerance combination difference between the two 

arresters. Using this simplified model, we then computed 

the current., powers, and energy depositions in a cascade 

consisting of two #mm varistors for the arresters, and 

a 20-mm varistor for the suppressor, both rated 150 V. 

We postulated a tolerance of + 10% for the line arrester 

and a tolerance of -10% for the neutral arrester. For the 

current imbalance, we postulated respectively 3 kA and 

1 kA for the case of an 8120-ps impinging surge, and 

respectively 200 A and 100 A for a 10/1000-ps surge. 

Figure 12 and Figure 13 show respectively the current 

distributions among the three devices for these two 

impinging surge waveforms. Even with the wide range 

of postulated differences between the arresters, the 

current in the suppressor is negligible. 

Figure 12 

Division of the current among attesters (neutral, I,), 

!!&, i2! em& =g=prese fe 6 1e;O-V r-~dg, 

1 O-m separation, 1 -kA13-kA, 8120-m surge. 

and tolerances of + 10% and -10% on the anesters 

EL....-- ? r aywr nu 

Division of the current among arresters (neutral, I,). 

(line, 12) and suppressor (I3) for a 150-V cascade. 

10-m separation, 1 00-AR00-A, 1 011 000-ps surge. 

and tolerances of + 10% and -1 0% on the arresters 

intuitive anaiysis of highiy noniinear varistor circuits 

lead to severe errors. However, in this case, the resull 

the accurate numerical computations can be readily und

stood by recognizing that the difference in voltages at poi

N and L is only 20% of the arrester clamping voltages, 

little to cause a significant current in the suppressor. 

Thus, a marked difference in the cascade behav

occurs, depending upon the neutral earthing pradice of 

-. ...lf&. --A at- 11-: ---.I-*-> -__-_-_ uuucy am LUG w~~npu~lwg pusruzutx~ sr;c:nariu 

coupling the impinging surge. It is important to note t

we have presented only two possible configurations amo

the many that may be encountered for different countr

Therefore, correct application of surge-protective devi

will be achieved only through a good understanding of 

context - the grounding practices - of a particular ap

cation. Such an understanding will require coordination 

the qpEca+;o~ infn_rm_.t;~n &ha A~velnnd --. ;nev

-a-r- ... -. -

Technical Committees or SubcomIlljttees of the Internatio

Electrotechnical Commission (IEC), specifically SC2

(Tnsulation Coordination), SC37A (Low-Voltage Sur

Protective Devices), 64 (haallation Wiring), SC77B @g

Frequency Disturbances), and 8 1 (Lightning Protection)

SERVICE ENTRANCE OPTIONS 

Among electric utilities, different philosophies a

different standards are encountered on what is deemed 

be an acceptable temporary overvoltage level. F

instance, in the U.S., ANSI Std C84.1-1989 only cite

moderate allowance for temporary overvoltages (+6

for 'Range B') but acknowledges the possibility 

urpater nvewnltaaw QC~, wh& PA^ "pr~

=--I-- ------- v-- 

corrective action shall be taken." The French utili

considers that temporary (over 5 seconds) overvoltages 

1.5 times the nominal system voltage must be accepted 

a realistic, unavoidable level in their distribution system

Some utilities may even wish to have a service entra

arrester survive the condition of a loose neutral conn

tion in a three-wire, neutral bonded to center-tap syste

VXAPI~ CIII-.CII+~~- nn An l;nhdrr_lnndarl &An m- ran

WLlULU VVGLVUALUgW VLl LUG LlgUUJ-AU4uGU SAUG baLL 1-U

values up to almost twice the nominal system voltage

Tbe occurrence of a temporary (smnds) overvolta

of 1.5 per-unit, or more, is likely to cause massive fail

of consumer-type equipment in a residence, raising 

issue of liability of the utility for this failure, in view 

the European trends in legislating that 'electricity i

product' and that suppliers thereof are liable in the c

of a defective product. 

* Communication by J.P. Mcycr at UTE Workrhop on Surge Arrest

Paris, March 20, 19Y2. 
An effective solution to this problem might be to 

design the service entrance arrester in such a manner that 

its relatively low maximum continuous operating voltage 

(made necessary by the millions of low-rated suppressors) 

wiii cause it to faii - in an acceptahie siton-circuiz mode 

- .& +deiekj 'he @ "?A&~~ *he r'& 

dence. Service would be interrupted and a replacement 

of the ~gwh~t, exped&de ave-ger WQI.~~ heqa~&, 

but the consequential liability of massive appliance 

failures would be avoided. This option seems to merit 

careful examination by the electric utilities, the arrester 

manufacturers, and the standards- or code-writing bodies. 

THE DILEMMA OF SPD VOLTAGE RATINGS 

- 

me foregoing resuits, acided to those presented in the 

many papers cited in the bibliography, forebode quite a 

challenging task of coordinating a cascade downstream of 

the service entrance. This challenge is made even more 

difficult by including the concerns about the 'Low-Side 

Surges' that have led to the recommendation of serviceentrance arresters with ac rms ratings higher than the 

classic 175 V (Dugan & Smith, 1986; Dugan, Kershaw 

& Smith, 1989; Marz & Mendis, 1992). 

Caught between the inescapable, too-late-to-bechanged situation of the 130-V varistors embedded in 

appliances and the recommendation of 175 V or more for 

arresters at the service entrance, the coordination schemes 

proposed by different authors appear elusive: equal 

voltages (Huse, MartzlofQ, lower voltage for the entrance 

(Hasse et al., Standler, Hostfet et al.), or slightly higher 

arrester voltage (Stringfellow). Perhaps, the 1970svintage protection schemes, with a gap-type arrester 

(Martzloff, 1980), rekindled as a result of the new 

coordination issues (Hasse et al., 1989), might be another 

solution. From the diverse interests and expertise of the 

five IEC committees mentioned above, a solution might 

emergz, although it is not obvious at this time. 

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 well-coordinated cascade difficult 

or perhaps unattainable in the near future. 

2. As a compromise, a cascade with equal voltage 

ratings for the meter qytrasnr can offer 

successful coordination, if the impinging surges are 

presumed to be relatively short. 

3. The coordination of a simple cascade of an arre

and a suppressor of equal voltage rating, b

connected line-to-neutral, is slightly improved by 

larger cross-section of the arrester. However

mfavorabie combination of tolerances for the 

devices mi wipe out me improvement. 

4. The neutral grounding practice of the utility ha

profound effect on the cascade behavior, and m

be thoroughly understood for successful applica

of cascaded surge protection. Clearly, additio

studies are required in this area. 

5. The waveform of the impinging surge has als

large effect on the outcome. If more data w

available on the frequency of occurrence of 'lo

surges', some of the uncertainty surrounding 

success of a cascade would be lifted. 

6. The idea of an expendable, one-shot arrester at 

service entrance could offer a solution out of 

dilemma and should be further investigated. 

Jih-Sheng (Jason) Lai is a native of Taiwan. He received 

MS. and Ph.D. in electrical engineering from the Universi

Tennessee, Knoxville, in 7985 and 7989, respectively. F

1980 to 1983, he was the Electrical Engineering Departm

Chairman of Ming-Chi Institute of Technology, Taipei, Taiw

where he initiated a power electronic program and receiv

grant from the school and the National Science Counc

study abroad. 

In 1989, he joined the EPRI Power Electronics Applicati

Center, where he is currently the Power Electronics Mana

His main research interests are power electronics mode

andsimulation, circuit design, andmicrocomputer applicati

Dr. Lai has 2 patents in high frequency power conversions 

adjustable speed drives and more than 25 articles publishe

the fields of control systems, power systems, and po

electronics. In the surge protection area, he ckvelo

varistor models and simulated cascaded surge protec

circuits to understand more about fundamental concepts

Franqois 0. MartJoff is a native of France. After un

graduate studies there, he obtained an M.S-, E.E. at Geo

- Iech h 1952 and, twenty years later. an M.S., I.A. at U

College. After 32 years in the private sector (Southem St

Eguipment, 1953- 7 956, and GE, 1956- 19851, he pined 

National Bureau of Standards, now National Institute 

Standards and Technology. His early professional experie

included the design of high-voltage fuses and high-vol

bushings. He changed to semiconductor technology, bu

high-vo/tage experience led him to the study of transie

which he has steadily pursued for the last 30 years. 

As an IEEE Fellow, he has contributed a number of pap

and ieu the development of several standards on su

characterization and surge testing. He has been granted 

patents, mostly on surge protection. In the IEC, he is ser

as Convenor of two working groups and chairs Subcomm

77B (High-frequency Disturbances) of TC77 on Ele

magnetic Compatibility IEMC). 
APPENDIX - BIBLIOGRAPHY * 

ANSIAEEE 052.41-1991 - Recorrrmended Practice on Surge 

Voltages in Low-Voltage AC Power Circuits. 

ANSI C84.1-1989 - Amen'can National Stcurdard for electnic 

Power Systems and Equipment - Voltage Ratings (60 Hertz). 

Cmur.h, R,F. and Mart710ffi FD. - Lightning P-mtection 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 

Protedion Application, NISIZR-4657, August 1991, pp 89-92. 

Dugan, R.C. and Smith, S.D. - Low-Voltageside -tSurge Phenomena in Single-Phase Distribution Transformer 

Systems. Prepnepnnt T&D 553-2, IEEE TdiD Confmence, 1986. 

Dugan, R.C., Kershaw, S.S., and Smith, S.D. - Protecting 

Distribution Transformers from Low-Side Current Surges. 

Preprint ID 401-1 PWW, LEEE T&D Conference, 1989. 

Dugan, R. C. - Conduction of Lightning Stroke Currents From 

the Utility System to Load Devices. Conference Proceedings, 

Power Quality '89, Intertech Communications Pub., Ventura 

CA. 

Dugan, R.C., Goedde, G., and Henry, C. - Conduction of 

Lightning Stroke Currents From the Utility System to Load 

Devices. Conference Proadings, Power Quality For End-Use 

Applications, Electric Power Research Institute, Paio Alto, 

March 1990. 

Dugan, KC. - Low-Side Surges: Answers to Common 

Questions. Cooper Power System BuUetin SE9001, April 

1992. 

Hasse, P., Wiesiger, J., and Zischank, W. - Isolationskoordination in Niederspannungsanlagen auch bei 

Blitzehchlagen. Elemotecia. Zeitschn'ft, Jan 1989, pp 64-66. cia -, Engiish iransiation avaiiabie fiom FE Xdv@ 

Hostfet, O.T. et al. - Coordiion of surge protective devices 

in power supply systems: Needs for secondary protection. 

Proceedings, International Conference on Lightning Protedion, 

Berlin, September 1992. 

Huse, 3.P. - Contributions to the revision of Doc 28A(Sec)47, 

Internal document, IEC/SC28A WGO1, 1988. 

IEC 28A(USAfLas Vegas)09 - (Draft) Explcuration for overvoltage categories. December 1984, Amended August 1987. 

IEC 37A/WG3(Convenor/Roma)l - Draft Application Guide, 

January 1992. 

IEC 64/WG3 138A - Explanation of interfaces for overvoltage 

categories. Supplement to Appendix B of Report 664,1990. 

IEC 77(CO) 1 18 Chsi@ation ofElemornugnetic Environments 

Lai, J.S. and Martzloff, F.D. - Coordinating Cascaded Surge 

Protective Devices. Proceedings, IEEE/L4S Annud Meeting, 

October 1991. 

Lai, J.S. - Performance Criteria for Cascading Surge-Protec

Devices. Proceedings, Open Fonun on Surge Protec

Application, MSTIR-4654, August 1991, pp 147-160. 

Lat, M.V. - Determining Temporary Overvoltage Levels 

Application of Metal-Oxide Surge Arresters on Multigroun

-.2.. . . - .. m-mY.r uismouuon aysrems. LCCC r ransaaionr r WAU-J, A

1990, pp 936946. 

ar--c-i,cT r n ,,a P -,.- I. v E n-..-a:--~..- a- 

AV'LQILYV117 I..-. 41lU L1VUbU7 n.E. - -1WVII UG 

protection contre les Surtensiom dans les r&eaux basse tens

dsidentiels. Proceedings, 1978ZEEE Ganadian Conference 

Communications and Power, pp 451454. (In French; Eng

translation available from FD Martzloff) 

Maxtzloff, F.D. - Coordination of Surge Protectors 

Low-Voltage AC Power Circuits. IEEE Transactions PRT-

Jan"ry/February 1980, pp 129-133. 

Mzdt off, F.D. =& My, T.F. - .Cpl&&g V=;_w Clamy

Voltage: Lower is not Better! Proceedings, 1989 EMC Zu

Symposium, pp 137-142. 

Martzloff, F.D. - Coupling, Propagation, and Side Effect

Surges in an Industrial Building Wiring System. lE

Transactions L4-26, March/April 1990, pp. 193-203. 

Martzloff, F.D. and Lai, J.S. - Cascading Surge-Protec

Devices: Coordination versus the IEC 664 Stairc

Proceedings, PQA 91 Con_ference, pp 191-198. 

Martzloff, F.D. - On the Propagation of Old and New Sur

Proceedings, @en Forum on Surge Protection Applicat

NISllR-4654, August 1991, pp 19-28. 

Man, M.B. and Mendis, S.R. - Protecting Load Devices fr

the Effects of Low-Side Surges. Proceedings, IEEE/IC

Conference, May 1992. 

Roulet, J.P. - La coordination de I'isolement et le mcep

'categorie de surteasion' en base tension. Prodngs, W

Workshop on Surge Arresters, Paris, March 20, 1992 

French). 

Scuka, V. - Application of modern surge suppressors in l

voltage power installation nehoorkr. Institute for High Vol

a_-&, LTpPdp LT~ym@, ~~~~:z19g6. 

Skuka, V. - EM1 Control in Low-Voltage Power Installatio

PrnruuAinoc .---R-".-e.., ---. TOR7 FMC -.--- 71irirh ~,~riirm, pp 639-434 

Standler, R.B. - Coordination of Surge Arresters 

Suppressors for Use on Low-Voltage Mains. Proceedin

199l Ziiricfi EMC Symposium, pp 5 17-524. 

Stringfellow, M.F. and Stonely, B.T. - Coordination of Su

Suppressors in Low-Voltage AC Power Circuits. Proceedin

Fonun on Surge Protection Application, MS12R-4657, Au

1991, pp 133-138. 

* Zhe authors and the concerned IEC Working Groups wouki welcome contribruions of additions to this bibliography. 

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