Arshad Mansoor, Member, IEEE

Power Electronics Applications Center

Knoxville TN 37932 USA

Amansoor@epri-peac.com

François Martzloff, Life Fellow, IEEE

National Institute of Standards and Technolo

Gaithersburg MD 20899 USA

f.martzloff@ieee.org

© 1998 IEEE

Reprinted, with permission, from

Proceedings, 8th Annual Conference on Harmonics and Quality of Power, Athens, October 

Significance:

Part 2 Development of standards

Part 7 Mitigation techniques

The application of surge-protective devices (SPDs) in low-voltage AC power circuits, in particular me

varistors (MOVs) has been influenced by the perception that low-limiting voltage is a desirable chara

Unfortunately, this low limiting voltage – intended for surge protection – makes the devices more sus

fail under conditions of extended temporary overvoltage (TOV).

Like any electronic component, SPDs will fail if overstressed beyond reasonable limits, and this is no

rejecting their application, but a cause for concern on ensuring that the failure mode – rare as it migh

acceptable. 

This acceptability must also take into consideration the effect of the available fault current that the po

can deliver at the point of connection of the SPD. This point needs to be more clearly and specificall

emerging standards on SPD applications.
The Dilemma of Surge Protection vs. Overvoltage Scenarios: 

Implications for Low-Voltage Surge-Protective Devices 

Arshad Mansoor, Member, IEEE 

Power Electronics Applications Center 

Knoxville TN 37932 USA 

Abstract - The application of surge-protective devices in lowvoltage systems faces the dilemma of providing effective limiting 

against surges while not attempting to limit the temporary 

overvoltages that do occur in a power system The paper illustrates 

this dilemma with specific scenarios and presents recommendations 

for reconciling these two conditions through adequate design and more explicit standards. 

I. INTRODUCTION 

The concept of b4Whole-House Surge Protection" has become 

a popular subject of discussion and has in fact been 

implemented by several utilities in North America. In this 

approach, the utility will install a surge-protective device (SPD) 

at the service entrance of the customer and provide additional 

plug-in SPDs. These additional SPDs are presumed to be 

wellcoordinated with the service-entrance SPD, and are 

installed within the customer premises, presumably at the point 

of connection of so-called "sensitive appliances" such as home 

entertainment, computers, and sophisticated kitchen appliances. 

The main purpose of these SPDs is to protect sensitive 

equipment against surges, a mission that they can accomplish 

quite well. However, the failure mode of these devices under 

temporary overvoltages (TOVs) that might be expected under 

abnormal but possible conditions of the power system has 

become cause of some concern for utilities and their customers. 

An SPD should not be expected to protect downstream 

equipment in the case of a TOV and then return to normal 

operation, as it does by definition for surge protection. The 

dilemma for SPD designers is whether to select a maximum 

continuous operating voltage (MCOV) high enough to survive 

common TOVs - but at the price of diminished surge 

protection - or to select surge protection with a lower MCOV 

- and then accept failure of the SPD for infrequent but 

possible TOVs. In any case, one should expect that if a TOV 

at any level would cause the SPD to fail, that failure mode 

should be acceptable. 

Fraqois Martzloff, Fellow, IEEE 

National Institute of Standards and Technology* 

Gaithersburg MD 20899 USA 

This dilemma of surge protection versus overvoltage scenarios 

has been created by the industry's obsession with providing 

very low clamping voltages for surge mitigation (Martzloff & 

My, 1989[1]). And now, the need to ensure coordination of 

the "cascade" of the service-entrance SPD and the plug-in 

SPDs has exacerbated this situation. The issue of cascade 

coordination has already been debated at length in the literature 

(Martzloff & Lai, 199 1 [2]); (Stonely & Stringfellow, 199 1 [3]); 

(Hostfet et al., 1992 [4]); (Rousseau & Perche, 1995 151). 

Further debate or exhaustive references to the many papers on 

that subject is not our purpose. It is mentioned here only as a 

contributing factor to the dilemma, but a factor that cannot be 

ignored in a complete assessment. 

11. SURGE PROTECTIVE DEVICES 

FOR LOW-VOLTAGE SYSTEMS 

Ihe introduction of metal-oxide varistors (MOVs) in the 

seventies was a timely innovation, concurrent with the 

increasing use of semiconductors in consumer products. While 

these semiconductors opened new opportunities, their relatively 

low tolerance for surges created a strong demand for better 

surge-protective devices. Unfortunately, market competition 

encouraged a downward "auction" that led to attributing high 

value to low clamping voltages, a situation unwittingly 

encouraged by the listing of "transient suppression levels" 

stipulated in UL Standard 1449 [6]. The list begins at 330 V 

for SPDs intended for 120 V circuits, although there is good 

evidence that most consumer loads do not need such a low level 

of protection (Anderson & Bowes, 1990 171); (Smith & 

Standler, 1992 [8]). 

The generic structure of typical low-voltage residential power 

systems is shown in Figure 1 for the case of a detached home. 

Underground service has similar characteristics. This system 

extends from the outdoor line-side of the service drop all the 

way through the premises wiring, including plug-in type SPDs. 

Figure 1 also shows the various locations where an SPD can be 

installed. 

* Electricity Division, Electronics mad Electrical Engineering Laboratory, 

Technology Administrution, U.S. Del~urtment of Commerce. 

Contributions~m the Nufionul Institute ojstundardr and Technolagy are not 

subject to U.S. copyright. 

Paper accepted for presentation at the 8U International 

Conference on Harmonics and Quality of Power 

ZCHQP '98, jointly organized by ZEEEIPES and NTUA, 

Athens, Greece, October 14-16,1998 

0-7803-5105-3/98/$10.00 0 1998 IEEE 

Typically, there are six locations. The first three: O at the 

outdoor weather-head, Q at the service entrance, and O on the 

line side of the main disconnect are within the scope of IEEE 

Std C62.34 [9]. The next three are within the scope of ongoing 

IEEE project P62.62 [lo]: @I at the load side of the panel 

disconnect, 6 at a permanently wired receptacle, and 8 as a 

plug-in device. Locations O through Q are within the premises 

wiring and therefore under the control of the end-user, while 

locations O and Q are under the control of the utility. 
Branch arcuit 

0 Load side d Service dmp @ Load side d mPh Overevnnt d8W 

@ Meter base adapter @ Penanently cumded maplade 

@Linesirkjdmainovercurrentdevke @Ccmicme&dwplug.ln 

Nat shown: SPDs incorporated in equipment power port 

Figure 1 - Possible SPD locations for a residential building 

An emerging requirement in standards for application of the 

low-voltage SPDs under development at the International 

Electrotechnical Commission (IEC 61643-1 [I 11) as well as at 

the IEEE (P62.62 [lo]) is the provision of a "disconnector" 

intended to discomect a failing SPD. Failure under conditions 

exceeding the SPD capability is recognized as unavoidable, but 

the consequences of such failure are made acceptable thanks to 

the action of the disconnector. 

Unfortunately, some ambiguity has crept in the interpretation 

of this requirement. In some cases is has been interpreted as 

only disconnecting the failed SPD component from the power 

system, but leaving the load energized - and without further 

surge protection (Martzloff, 1998 [12]). If the disconnector is 

of this latter type, the SPDs components of an SPD package 

will fail under TOV conditions, presumably in a safe manner, 

but then allow the TOV to be applied to the downstream load. 

This is undesirable for the typical user who values equipment 

protection above continuity of operation. Finally, there is the 

worst case, as reported in many anecdotal instances, where the 

failure mode of SPDs under TOV conditions has not been 

graceful, to say the least. These instances, while not very 

frequent, have led to new testing requirements for failure 

modes from the Underwriters Laboratories in the updated 

Second Edition of their UL 1449 [6] Standard for low-voltage 

surge-protective devices ("TVSS" in the industry jargon). 

Given this unsettled situation, it will be useful to review the 

scenarios that can lead to failure of an SPD component in an 

SPD package, in particular under TOV conditions. For the 

sake of completeness, we will describe first some failure 

scenarios under surge conditions, as they have some bearing on 

the disconnector design. 

III. FAILURE MODES UNDER SURGE 

CONDITIONS 

For a correctly applied SPD, failure under surge conditions 

should be a very rare occurrence. Nevertheless, one can 

enumerate the following failure scenarios in a field application 

- including misapplications: 

A single, large, and not anticipated impinging surge 

exceeds the capability of the SPD. An example of this 

situation can be the presence of switched capacitor banks; 

A succession of surges, such as multiple lightning strokes, 

exceeds the capability of the SPD. This situation has been 

identified for distribution arresters (Darveniza, 1997 [I 31) 

and might also occur for low-voltage SPDs; 

A thermal runaway is launched in an SPD exposed to high 

ambient temperatures at the time when a surge (within 

specifications for normal ambient) occurs; 

In the questioriable scenario of an alleged "degraded" SPD 

(Stringfellow, 1992 [14]), a thermal runaway is launched 

by the heat generated during a within-specifications surge. 

For all these scenarios, the ultimate failure mode depends on 

the fault current that the power system can deliver at the point 

of connection of the SPD. For maderate fault currents, such as 

on branch circuits, the disconnector can generally provide 

protection. The fuse design can still be a challenge: carry the 

load current, carry the specified surge current, but melt in case 

of a power-frequency fault current resulting from failure of the 

SPD component. For very high available fault currents, such 

as that prevailing at some service entrances close to a large 

distribution transformer, successful clearing may be a greater 

challenge. Furthermore, coordination of overcurrent protection 

is more difficult, compared to branch circuits inside the 

building where the wiring impedance and the rating of circuit 

breakers in the panel can ensure proper coordination. 

IV. FAILURE MODES UNDER TOV CONDITIONS 

Three major types of TOV-induced failures can be identified 

for low-voltage SPDs: 

Moderate TOVs associated with power system faults, such as 

a line-toearth fault in a three-phase system, creating a 1.73 

times nod line voltage in the other phases. Ferroresonance 

can also produce moderate but significant overvoltages. 

Extreme TOVs associated with the commingling scenario 

(accidental fall of conductors of a higher voltage upon 

conductors of a lesser voltage). No conventional, varistor-only 

SPD can be expected to survive such a scenario. 

Double voltage TOVs associated with the loss of neutral in a 

single-phase, threeconductor, earthed center-tap system such 

as the 1201240 V service typical of North American systems. 

Depending on the philosophy of the system designer, in 

particular the utility for the case of a service-entrance SPD. 

survival or expected but acceptable failure can be stipulated for 

the loss-of-neutral scenario. 
a) Moderate TOVs: System Faults 

Among abnormal conditions that can produce temporary 

overvoltages, we give two examples of incidents resulting in 

overvoltages not exceeding twice the normal voltage. Some 

SPDs based on the misconception that a very low clamping 

voltage is desirable might not survive such moderate TOVs. 

Single-phase faults to earth on a three-phase system produce 

a shift in the unfaulted phases. The severity of the voltage rise 

depends on the fault location, the system impedance, and the 

earthing practices. For a 'IT power system in steady-state, the 

neutral will by symmetry be at the same potential as earth, as in 

Figure 2 (a). However, if an earth fault occu on one phase, it 

will cause a shift of potential as the system attempts to maintain 

balance. The neutral will be elevated and a corresponding shift 

will be experienced by the other two phases. In the worst case 

of a completely isolated system with a bolted fault to earth on 

one of the phases, we could have the situation depicted in 

Figure 2 (b). This shows a neutral which has been elevated to 

one per unit, causing the unfaulted phases to drift up to 1.73 per 

unit with respect to earth. 

For three-phase systems with an artificial neutral through an 

earthing transformer or a finite resistance, the earth impedance 

is high. This arrangement limits the fault current during a 

singleline-toearth fault, but allows enough for fault detection 

using overcurrent relays. It also inserts some impedance 

between the system neutral and the actual earth so that the 

voltage on the unfaulted phases will shift toward somewhat less 

than line-line value as shown in Figure 2 (c). 

Figure 2 - Effect of a single phase-to-earth fault 

Series resonances occur in a power system when a series 

circuit consisting of an inductance and a capacitance is excited 

at its natural frequency. As an example of this condition, 

Figure 3 shows a portion of a temporary overvoltage resulting 

from a power system switching incident (restoring power phase 

by phase after interruption [15]), which produced a sustained 

rms voltage exceeding 150% and lasting four seconds. 

Source: EPRl Report [l5] 

Figure 3 - Temporary overvoltage caused by ferroresonance 

b) Extreme TOVs: Commingling 

In this real-life scenario, the low-voltage SPD connected on the 

secondary side of the distribution transformer, and normally 

energized at its rated voltage, is first brought to failure by the 

large overvoltage resulting from commingling conductors. In 

an overbuilt system, a collision of a vehicle with a pole, or 

breaks caused by icing, the conductors of the higher voltage 

distribution system or sub-transmission system can fall on the 

lower voltage distribution system. Such accidental contact 

injects an intruding voltage for a few cycles, until the higher 

voltage breaker clears the fault. 

Figure 4 shows a simplified one-line diagram of the two 

medium-voltage systems (the intruding MV1 and the victim 

MV2) being accidentally commingled. In this figure, the bond 

between the two systems earth connections is shown in dotted 

line to present the generic case of commingling. In an overbuilt 

system with common neutrals, a solid bond exists where the 

dotted tine is shown in the diagram. In the scenario of a simple 

crossing of two systems (not overbuilt along the right of way), 

or delta systems, a solid bond might not be present, and the 

fault current from MV1 will involve the earthing impedances 

shown in the diagram In that case, the intruding voltage Vi 

might be less than the system voltage MV1 but still enough to 

precipitate failure of an SPD on the secondary. 

Figure 4 - Commingling overvoltage applied to the distribution 

transformer primary and reflected on the LV side 
c) Double-voltage TOV (Loss of neutral) 

There are many situations where loss of neutral can occur. 

Some can be of a transient nature, such as a loose connection, 

while some might be permanent until repaired, such as a 

mechanical break or corrosion of the neutral conductor. While 

the latter might not linguistically fall under the label of 

'temporary', the consequences are the same. In a three-wire, 

single-phase system typical of North American practice, this 

condition has been observed many times. 

Figure 5 shows a system where one side of the supply (Ll) is 

lightly loaded, while the other side (L2) is heavily loaded, 

Under normal conditions, the two sides remain at normal 

voltage. Should the neutral connection be lost, then the voltage 

at mid-point is determined by the ratio of impedances on the 

two sides: the L1 side experiences an overvoltage that can 

approach twice nonnal. Any SPD connected to this side will 

then be exposed to the twice-normal voltage, with an available 

current determined by the impedance 22. This current, by the 

very design of the circuit, will not be interrupted by the 

overcurrent protection and is available to generate substantial 

heat in the SPD that has failed as the result of the overvoltage. 

A disconnector designed to clear larger fault currents, such as 

those occumng if the SPD fails while the neutral is connected, 

might not be capable of clearing the limited current. Other 

schemes are then necessary to ensure an acceptable failure 

mode, such as a thermally-activated disconnect. 

1996 National Electrical Code, 230-65, Availabk Short-circuit 

Cumnt 

"Service equipment shall be suitable for the short-circuit 

current available at the supply terminals." 

IEEE C62.341996, Standard for Performance of Low-Voltage 

Surge-Protective Devices (Secondary Arresters), Article 7.6 

"If the manufacturer claims a fault current withstand rating, 

then that rating shall be verified." 

IEC 61643-1 (FDIS November 1997) Surge protective devices 

connected to low-voltage power distribution systems - Part I: 

Performance requirements and testing methodr, Artick 6.2.11 

"The SPD shall be able to carry the paver short-circuit 

current until it is interrupted either by the SPD itself; by an 

internal or external overcurrent disconnector, or by the backup 

overcurrent protection." 

It is noteworthy that none of these documents specify a value 

for the available short circuit, but rather leave it to the 

discretion of the manufacturer, while imposing criteria of 

acceptability after the failure. The NEC tersely requires the 

device to be "suitable," without elaboration. The two standards 

applicable to a service-entrance SPD - where the available 

fault current can be quite high - acknowledge the possibility 

of failure and significance of the available fault current, but do 

not stipulate specific values. 

In an attempt to obtain information on what levels of fault 

currents should be considered, an informal survey was 

conducted among a few utility engineers. It turns out that very 

few utilities limit the available fault current at the service point 

of residential customers but many people are under the 

misconception, as cited below, that all residential service load 

centers and breakers are limited to an available fault current of 

10 kA and therefore they assume that actual available fault 

current must be less than 10 kA. 

Figure 5 - Three-wire, singlephase system 

where a broken or intermittent neutral connection 

creates a voltage imbalance 

V. AVAILABLE FAULT CURRENT 

As described in the preceding paragraphs, several scenarios can 

produce failure of the SPD, ultimately offering a very low (but 

not zero) impedance to the flow of the fault current that the 

power system can deliver. For each scenario, the available fault 

current at the point of connection of the SPD will have a very 

significant effect on the failure mode. 

The significance of available fault current is recognized in 

standards, but the value that should be considered is generally 

left undefined. The following statements can be found in 

published standards. 

Interestingly, none of the individuals consulted on this issue 

could cite a standard or even a document with the status of 

a consensus guide that does stipulate a current value. Two 

perceptions seem to prevail among the individuals consulted, as 

quoted below: 

Based on the observation that breakers for typical 

residential service panels (up to 200 A) generally have an 

interrupting capacity of 10 kA, it would be logical that 'the 

available fault current at the service entrance would be in 

the same order of magnitude. 

Based on the reality that a service entrance connected 

clo,e to a large distribution transformer (such as a garden 

apartment or high-rise) will have available fault currents 

in excess of I0 kA, it would be prudent to review the 

specifics of the situation. 

Furthermore, these standards do not require that the SPD 

application data state a limit of acceptable fault current. 
VI. EMERGING STANDARDS 

a) SPDs installed downstream from the service entrance 

In recognition of the issues raised by failure modes of the SPDs 

within the scope of UL Standard 1449 - downstream of the 

main disconnect - the second edition of this standard [6] now 

requires demonstration of an acceptable behavior in the failure 

mode of SPDs exposed to various overvoltage scenarios. 

Specifically, among the many tests required by UL, three tests 

address the issue: 

Temporary overvoltage with high available current - This test 

is stipulated un&r article 37.2 of UL 1449, calling for extended 

exposure to 125% of normal line voltage with either an 

acceptable temperature equilibrium being attained or until an 

internal disconnect device operates. This test will demonstrate 

capability of sustaining moderate overvoltages, primarily 

providing a margin against high system voltage, but not the 

higher levels of temporary overvoltages covered in the next 

test. The available fault current specified for this test is defined 

as a function of the ampere rating of the service over a range of 

200 A to 25 000 A. 

Fullphase voltage with high available fault current - This test 

is stipulated under article 37.3 of UL 1449, calling for exposure 

to the "full phase voltage" as shown on Figure 2(b) of this 

paper. The same criteria as above apply, namely acceptable 

temperature equilibrium or operation of an internal disconnect. 

The available fault current specified for this test is &fined as 

a function of the ampere rating of the service over a range of 

200 A to 25 000 A. 

Overvoltage with limited current - This test is stipulated under 

article 37.4 of UL 1449, with overvoltage values presumably 

corresponding to a loss of neutral scenario, and the associated 

low values of current supplied by the connected load, as in 

Figure 5. 

It is noteworthy that in the stipulations of these three tests, the 

emotionally charged word "failure" is not used. Instead, a list 

of unacceptable conditions is given, including emission of 

flame, molten metal, flaming particles, charring of adjacent 

material, ignition of enclosure, or creation of openings leaving 

live parts accessible. 

b) SPDs installed upstream from the service entrance 

For SPDs connected upstream from the service panel, the 

recently published IEEE Standard C62.34 does describes a 

loss-of-neutral scenario with limited current, similar to the UL 

37.4 test. However, a demonstration test is not mandated, as 

the consensus development process settled for a weaker 

statement: "if the manufacturer claims a loss of neutral 

withstand capability ... then that capability shall be venjied ..." 

Thus, the inference might be made that if no claim for loss-ofneutral withstand capability is made, no demonstration test is 

required. However, an additional paragraph in the standard 

does mention "...must fail in an acceptable manner. " 

From this brief overview of emerging standards, it appears that 

on the low side of available fault current, both the UL and the 

IEEE standards have recogruzed the issues of acceptable failure 

modes associated with temporary (or quasi-permanent) 

overvoltages. On the other hand, at the high side of available 

fault currents, it seems that insufficient recognition of the issue 

still prevails, as discussed in the preceding section on the 

significance of the level of available fault currents. 

Nevertheless, Figure 6, offered as background information in 

a tutorial addressing considerations on the revenue meter 

environment (Ward, 1980 [16]), shows typical values of fault 

current as a function of distribution transformer size and length 

of service drop. That figure clearly shows values in excess of 

10 kA, but somehow this information has not been fully 

recognized by the SPD community. 

- - 

AVAILABLE FAULT CURRENT 

WITH rOorr SERVICE COR 3 

TRANSFOWER SIZES 

tm AL SERVICE -CABLE LENOW -FEET 

Source: (Ward, 1980 [I 61) 

figure 6 - Fault current amplitude as a function of. 

transformer rating and length and size of service drop 

vn. POSSIBLE SOLUTIONS 

Among possible solutions, two approaches may be 

considered: making the SPD less sensitive to TOVs, and, 

in any case, ensure that if failure is unavoidable under 

extreme stress, it will be in an acceptable mode. 

The obvious way to desensitize SPDs to TOVs is to 

design them with a higher MCOV. However, as the 

higher MCOV in a varistorsnly SPD means a higher 

surge-limiting voltage, there is a limit beyond which such 

an SPD becomes useless (op cit., [2-51). 

A pos:.ble solution may be in reviving the concept of a 

gapped arrester for the upstream SPD of a "whole house" 

scheme (Mansoor et al., 1998 [17]). There, the initial 

let-through associated with the gap volt-time response 

can easily be mitigated by the downstream SPD, while 

the gap prevents the SPD from becoming involved with 

moderate TOVs. 
Of course, for the (rare) commingling scenario, little can 

be done but to ensure a graceful failure. This condition 

should be an implicit requirement, but, as discussed in the 

section on available fault current, the implications of such 

a requirement apparently have not been recognized by all 

interested parties. Even among the community of SPD 

engineers, there has been some reluctance to accept the 

concept that temporary overvoltages should be addressed 

in documents discussing the surge environment. 

VIII. CONCLUSIONS 

The dilemma of providing a suitable surge protection of 

load equipment by means of surge-protective devices, 

while ensuring acceptable response of these surgeprotective devices to unavoidable temporary overvoltages 

raises several application issues that demand attention. 

"Acceptable response" can be interpreted either as survival 

of the SPD (a challenge to the coordination of cascades) or 

as accepting failure, but within well-defined conditions of 

the failure mode (a challenge for applications where high 

available fault currents prevail). 

Coordinating a cascade of surge-protective devices can be 

solved by providing a gapped arrester at the service 

entrance, which will coordinate with the de facto situation 

of low limiting voltage SPDs inside the building. 

The need for a service-entrance arrester to withstand the 

scenario of lost neutral can be satisfied by a gapped 

arrester having sufficient maximum continuous operating 

voltage capability. 

Emerging standards for low-voltage SPDS have given new 

recognition to the importance of taking into consideration 

temporary overvoltages in the design of SPDs. 

Notwithstanding conclusion (3, SPD application standards 

as well as performance and test standards should be more 

explicit in defining how to deal with the issues raised by 

available fault current in case of unavoidable SPD failure. 

IX. REFERENCES 

Martzloff, ED. and Leedy. T.F., "Selecting Varistor Clamping 

Voltage: Lower Is Not Better!" Proceedings, 1989 Zurich 

International EMC Symposium. 

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

Devices: Coordination versus the IEC 664 Staircase," 

Proceedings. PQA 91 Conference. 

Stringfellow, M.F. and Stonely, B.T., "Coordination of Surge 

Suppressors in Low-Voltage AC Power Circuits," Proceedings, 

Fonun on Surge Protection Application, NISTIR-4657. August 

1991. 

Hostfet, O.T., Hervland, T., Nansen. B. and Huse, J., 

"Coordination of surge-protective devices in power supply 

systems: Needs for secondary protection," Proceedings, 

International Conference on Lightning Protection, Berlin, 

September 1992. 

Rousseau, A. and Perche, T., "Coordination of Surge Arresters 

in the Low-Voltage Field," Proceedings. 7th International 

Telecommunications Conference (IhTELEC), 9SCH35824. 

UL 1449 Standard for Safety for Transient Voltage Surge 

Suppressors, Second Edition, August 1996. 

Anderson. L.M. and Bowes, K.B., 'The Effects of Power-Line 

Disturbances on Consumer Electronic Equipment." IEEE 

Transactions PWRD-5, No.2, April 1990. 

Smith, S.B. and Standler, R.B., 'The Effects of Surges on 

Electronic Appliances," IEEE Transactions PWRD-7, No.3, 

July 1992. 

IEEE Std C62.34, IEEE Standard for Pe$ormance of LowVoltage Surge Protective Devices (Secondary Arresters), 1996. 

IEEE Project P62.62 - Application Guide - Low-Voltage SurgeProtective Devices (ongoing). 

IEC Document 37A163EDIS -Draft IEC 6 1643- 1 : Surgeprotective devices comected to low-voltage distribution systems 

Part 1: Performance requirements and testing methods, November 

1997. 

Martzloff, F.D., "Interpretation and Misinterpretation of TVSS 

Discomector Indications," Scheduled for publication in Power 

Quality Magazine, July/ August 1998. 

Darveniza, M., Turnma, L.R., Richter, B., and Roby, D.A., 

"Multiple Lightning Currents and Metal-Oxide Arresters," IEEE 

Transactions PWRD-12, No.3. July 1997. 

Stringfellow, M.F., "Fire Hazard of Surge Suppressors," 

Proceedings, Fiflh Annual Power Quality Conference, Irvine 

CA, 1992. 

EPRI Report An Assessment of Distribution System Power 

Qualify, Electric Power Research Institute. Palo Alto CA, 1996. 

Ward, D.J., "Secondary Fault Currents at the Service Entrance." 

Proceedings, 55* Annual Electric Meter School and Conference, 

University of Florida, Gainesville FL, 1980. 

Mansoor, A., Martzloff, F.D.. and Phipps, K.O.. "Gapped 

Arresters Revisited: A Solution to Cascade Coordination" Paper 

PE-114-PWRD-0-12-1997, IEEE Winter Power Meeting, 1998. 

Arshad Mansoor (M' 1995) is an 

Electrical Systems Engineer at the EPRI 

Power Electronics Applications Center 

(PEAC). He received his MS and Ph.D. 

in electrical engineering from the 

University of Texas, Austin in 1992 and 

1994 respectively. His areas of interest 

include power Quality, power systems 

transients analysis, harmonics, surge 

- propagation and protection, and EMTP - model development. 

Francois Martzloff (M'1956, F' 1983) 

Born and educated in France, with 

additional MS degrees from Georgia 

Tech and Union College, worked at 

General Electric for 29 years and now 13 

years at the National Institute of 

Standards and Technology. He is 

contributing to several technical committees for the development of standards 

on EMC, surge protection and Power 

Quality in the IEEE and the IEC.