Significance:

Part 4 – Propagation and coupling of surges

Part 7 – Mitigation techniques

Part 8 – Coordination of cascaded SPDs

Laboratory tests on the effect of distance for coordination between a surge-protective device (SPD) at the service

entrance and an SPD at the end of a branch circuit.

The service entrance SPD, 1960-1970 vintage, consisted of a silicon carbide disc with a series gap.

The branch circuit SPD consisted of a simple MOV disc incorporated in a modified plug-and-receptacle combination,

probably the first attempt at packaging an MOV for residential surge protection.

Tests were performed with a simple generator capable of delivering up to 8 kV peak open-circuit voltage of 2/60 :s

waveform and 2 kA peak short-circuit current of 30/50 :s waveform. These values – dating back to pre-IEEE 587

consensus waveforms – were at the time deemed to represent a severe surge associated with a lightning flash to the

power system, outside of the residence.

One objective of the tests was to determine the values of surge current and distance between SPDs that produced

the threshold from no sparkover of the service entrance SPD (maximum stress on the MOV) to sparkover, thus

limiting the stress on the MOV. This was one of the first illustrations of what became a series of experimental and

theoretical studies of the “cascade coordination” concept.

Filename: Coordination 1976
GENERAL ELECTRIC 

General Electric Company 

Corporate Research and Development 

Schenectady, New York 

I - - ,R:i:,":r' Electronic Power Conditioning CORPORATE RESEARCH AND DEVELOPMEN1 

and Control Laboratory SCHENECTAOY, N.Y. 

UMMARY Tests performed on a representative residential 

 iring system with a Home Lightning Protector (HLP) and 

1 Voltage Spike Protector (VSP) installed on the service 

)ox and an outlet, respectively, indicate good coordinatior 

letween the characteristics of the two devices. For surgt 

)f relatively small amplitude, the VSP performs all of the 

TECHNICAL Mff ORMATlON 

SERIES 

UTHOR 

Martzloff, FD 

~oltage clamping functions. As the energy (current) of tht 

surge increases, a point is reached where the HLP sparkIver voltage is reached, and this device takes over the 

'unction of diverting the surge energy while the VSP keeps 

;he voltage clamped at low levels. The current for which 

:his transfer takes place depends on the distance between 

;he two devices. For practical situations, enough distancc 

wiring length) will exist to limit the duty imposed on the 

V'SP to acceptable levels, giving the HLP an opportunity 

:o divert high energy surges. 

EY WORDS 

SUBJECT 

surge voltage 

suppression 

transients, spikes, lightning, arrestors, 

varistors, GE-MOV 

NO 

76CRD092 

%$ay 1976 ITLE 

;urge Voltage Suppression in Residential 

?ower Circuits 

INFORMATION PREPARED FOR 

GE CLASS 

1 NO.PAGES 11 

Additional Hard Copies Available From 

Microfiche Copies Available From 

RD-54 (10/70) 

Corporate Research 8 Development Distribution 

P.O. Box 43 Bldg 5 , Schenectady , N.Y., 123

Technical Information Exchange 

P.O. Box 43 Bldg. 5, Schenectady , N.Y,123
SURGE VOLTAGE SUPPRESSION 

IN RESIDENTIAL POWER CIRCUITS 

- F.D. Martzloff - 

Surge voltages occurring in residcntial power circuits have two origins: 

external surges, produccd by power system 

switching operation or by lightning, and 

internal surgcs produccd by switching of 

appliances in thc home. The voltage levels 

of these surgcs are sufficient to cause 

failure of sensitive electronic appliances, 

and some of thc highcr surges can even fail 

the morc rugged clcctromechanical devices 

(clocks, motors and heater^)^,^. 

For many years, the General Electric 

Company has offered a secondary surge 

arrester under the name of "Home Lightning 

Protector" (HLP), which is very effective 

in protecting non-electronic devices 

againsL high energy, high voltage surges 

associated wi Lh lightning or power syst.em 

swiLching. Huweve1-, the protective level 

of this arrester, consistent with the 

limitations imposed by the design of such 

a device, is still too high for sensitive 

el ectaonic devices. Furthermore, its installation requires a competent electrician. 

A new suppressor has been developed 

and introduced by the Wiring Uevicc Dcpartment under the name "Voltage Spike Protector" (VSP); this device incorporates a 

GE-MOW varistor in a plug-in device allowing purchase and easy installation by the 

user. The protective level of this device 

is substantially lower (that is, betLer 

protection is provided) than the HLP, so 

that protecLior~ 01 ..ensi Live electrnni c 

appliances is now possible. Howr-ver , the 

energy handling capabiliLy of this 

suppressor is lower than Lhat of Lhe HLP, 

so thaL large currents assoi: iated wi th 

lightning slrikes cannot 1~e handled by the 

device. 

The availability of these two different types of suppressors now makes it 

possible to obtain a coordinated protection 

of all the appliances in a home. Installation of the IILP at the service entrance 

will deal with the larger surges, while the 

VSP installed at a wall receptacle will 

protect the more sensitive dcviccs. For 

the lower surges, the VSP will clamp the 

voltage to a low level. For the higher 

surges, the VSP will first attempt to absorb all the surgc current, but the voltage 

developcd across the varistor plus the voltage drop in the wiring between the receptacle whcrc the VSP is installed and the 

O RrgisLrred trademark of the General Electric 

C~~rnpdny. 

servic.e box where the HLP is installed wi

reach the sparkover voltage of the HLP. 

The RLP then takes over, diverting the hi

current surgc trom thc VSP, so that no ex

cessive cncrgy is applied to the latter. 

This report describes how this coordination takes place, based on simulated 

surges in a representative wiring system. 

The lcvels of voltage and current in thes

tests show when the HLP and VSP respectiv

assume all of the protective function, an

where the transfer takes place, depending 

on the distance between Lhe VSP in an out

and the service box where the HLP is installed. 

11, THE HOME LIGHTNING PROTECTOR 

The Home Lightning Protector (HLP), 

produced by the Distribution Transformer 

Business Departmcnt. It is a surge arres

of the valve and series gap type (Fig. 1

Earlier designs involved lead oxide pelle

with the oxide pellet acting as a nonline

resistor and the multiple contact points 

between the pellets as a multiple gap. A 

more recent design uses a Thyrite@ disc i

series with a low voltage gap. 

This UL-listed arrester is rated for 

lighLning surge duty, and is described in 

the GE Handbook as having a sparkover of 

2 kV crest under a 10 kV/l~s impulse with 

discharge voltages of 1, 1.2 and 1.4 kV 

respec.tive1 y at 1500, 5000 and 10,000 A f

a 10 x 20 vs current wave (see Appendix I

Figure 1. Home Lightning Protector 

hlanuscript received May 3, 1976. 
As any gap-type arrester will, the HLP 

has a volt-time characteristic exhibiting 

some increase in the sparkover voltage as the rate of rise of the impinging surge increases. Typical sparkover voltages for 

the sample tested under the particular waveform used here were in the order of 2000 V 

or less. This represents an effective 

clamping to protect electromechanical appliances, heaters, etc. However, sensitive 

electronic appliances may well have failure 

levels below 2000 V. This is recognized in 

the box label which describes the HLP. as a protector for "home and farm non-electronic 

equipment, wiring appliances and water 

heaters". 

Thus, while the HLP offers reliable 

protection for non-electronic appliances 

and a respectable energy handling capability, a device with a lower voltage clamping characteristic is required to protect 

sensitive electronics. This need is now met through the Voltage Spike Protector, 

described in the next section. 

1111 THE VOLTAGE SPIKE PROTECTOR 

The heart of this device is a GE-MOVB 

varistor, connected line-to-line in a com- bination plug-socket (Fig. 2). This package, developed and produced by the Wiring 

Devices Department, makes it convenient for 

the user to install the protector at any 

outlet in the house, and the socket end 

allows the user to plug the protected appliance directly into the protector. In fact, 

protection is afforded to devices in all 

other wall outlets (to a varying degree, 

depending on the branch circuit configuration) and it is not mandatory to plug the 

appliance into the suppressor (it is a 

shunt, not a series device). One of the reasons for the socket end is just a convenience, so as not to lose the use of a receptacle or require a cube tap. 

Figure 2. VoZtage Spike Protector 

In addition to the varistor, a non- resettable, one-shot thermal protection 

inserted in series with the varistor, as insurance against thermal runaway of the 

varistor in case of excessive environmen

conditions. 

The protective characteristics of t

varistor are such that a 15 A surge, typ

cal of large internally-generated surges

will limit the voltage across the suppre

to 500 V, as opposed to values exceeding 

2000 V which have been recorded during 

monitoring of houses known to contain a 

switching device producing such surges1

For large current values such as those a

ciated with "lightning remnants", i.e. 

surge entering the house when a lightnin

stroke occurs near the house (but not a direct stroke), one can expect currents 

the order of 1000 to 2000 A. These woul

produce a voltage of 800 to 1000 V acros

the varistor. However, as we will see, 

presence of an HLP device at the service 

box, ahead of the varistor, will limit t

current flowing toward the varistor to a 

lower value, by diverting the current 

through the HLP because of the additiona

drop in the wire which raises the voltag

across the HLP to its sparkover voltage. 

IV, TEST CIRCUIT 

The test circuit (Fig. 3) consisted 

a terminal board from which two lines, o

25 ft. (7.5 m) and the other 100 ft. (30 

long were strung in the test area. A sh

10 ft. (3 m) line simulated the service 

drop. All of these were made of 3-condu

non-metallic sheath wire (Etcoflex type 

#12 AWG. The neutral and the ground wir

of the three lines were connected togeth

at the terminal board, and thence to the 

reference ground of the test circuit. 

All surge currents were applied bet

ween the line conductor (black) at the e

of the service drop and the reference 

ground. These impulses were obtained fr

a 5 UF capacitor, charged at a suitable 

voltage, and discharged into the wiring 

system by an ignitron switch. Figure 4 

shows the connections and parameters of 

surge generator circuit. The resultant 

open-circuit voltage waveform, a unidire

tional wave of 1 us rise time x 50 ps to 

1/2 value time, corresponds to the stand

test wave in utility systems. It is a m

more severe test than the recommended TC

wave~hape~,~ and as such provides very c

servative results. Figure 5 shows typic

open-circuit voltage and short-circuit 

current waveforms. Voltages were record

by a Tektronix 7633 storage oscilloscope 

through a P6015 attenuator probe (1000:l

currents by a Tektronix 7633 oscilloscop

through a current probe P6042 with a CT-

1000:l current transformer. Thus, the ca

brations displayed on the oscillogram ar

to be multiplied by 1000 for the voltage
GR~EEN 

(GROUND) 

Figure 3. Test Circuit 

while the current traces show the 50 mV 

setting corresponding to the rated output 

of the current probe, with the ampere per 

division shown corresponding to the current 

transformer ratio and current probe input 

setting for a direct reading. Sweep rate 

is also shown on the oscillograms, at 10 us/ 

div. for all the tests. 

V, TEST RESULTS 

Several test conditions were invest igated, with the varistor at the end of the 

short line or at the end of the long line. 

The HLP and VSP responses were established 

by connecting them one at a time, in addition to establishing the open-circuit voltage and short-circuit current for each 

Figure 

HVDC IGNITRON 

201+(6r

Figure 4. PuZse Generator Circuit 

condition. The results will be discuss

with reference to specific sets of osci

grams showing voltages and currents in 

various parts of the circuit, each time 

the same setting of the surge generator

1. HLP AND VSP RESPONSE 

Figure 5a shows a 3000 V open-circ

voltage surge at the service box, with 

neither suppressor connected. Figure 5

shows the corresponding 600 A short-cir

current for a jumper connected at the 

service box. Figure 6a shows the volta

across the HLP when subjected to the su

defined by Figures 5a and 5b. Note tha

the sparkover voltage reaches 2200 V wi

several oscillations before the voltage 

settles down to the impulse discharge 

voltage at about 1000 V at its start. 

Open Circuit VoZtage and Short-circuit Current 

(without any protector) 

3 
Figure 6 

Response of HLP & VSP 

Figures 6b and 6c show respectively the 

voltage and current across the varistor. 

Note that the maximum voltage is 600 V, for 

a 550 A current on the varistor. (The 

current in the varistor is lower than the 

available short-circuit current because of 

the reduced available voltage since the 

varistor holds off 600. 

2. PROPAGATION OF SURGES 

Figure 7 shows several oscillograms 

indicating how the surge propagates in the 

wiring in the absence of any suppressor, 

and how the installation of one VSP device 

at an outlet is reflected elsewhere in the 

system. Figures 7a and 7b show respectively 

the open-circuit voltage an3 short-circuit 

current at the service box. At the openended 25 ft. (7.5 m) line, the voltage is 

substantially the same a s a t the box (Fig. 

7c). However, at the end of the 100 ft. 

(30 m) line with a 50 R termination, a 

significant decrease of the slope is noticeable, while the crest remains practically 

unchanged (Fig. 7d). 

In Figures 7e-g, a VSP varistor has 

been added at the end of the 25 ft (7.5 m) 

line. Voltage and current at the varistor 

are shown in Figures 7e and 7f, with a 

maximum voltage of 500 V for a 200 A surge. 

Meanwhile, the voltage at the box is limited 

to 750 V, an appreciable reduction from the 

1500 V that would exist without the remote 

VSP under this surge condition (Fig. 7g

3. TRANSFER OF SURGES 

With the voltage limiting at the b

provided by the installation of a VSP, 

at a remote outlet (Fig. 7g), an HLP con

nected at the service box cannot reach 

sparkover voltage until substantial sur

currents are involved. For a short dis

tance between the serbice box and the V

a larger current will be required than 

a greater distance. The value of the c

rent required to reach sparkover as a 

function of the distance is therefore o

interest. 

For a distance of 25 ft. (7.5 m), 

threshold condition where sparkover of 

HLP just occurs is depicted in Figure 8

In Figures 8a and 8b, the open-circuit 

tage and short-circuit current are show

for this threshold setting of the gener

Inspection of the oscillograms shows an 

open-circuit voltage of 8.1 kV and a sh

circuit current of 1.9 kA, hence a calc

lated sourcc impedance of 4.2 fi.* Thi

low value of the source impedance (comp

* This is only a crude approximation since the 

current waveform does not match the voltage 

waveform. Therefore, the circuit impedance 

not a pure resistance or characteristic impe
fa) open-circuit voZtage - at box short-circuit current 

(el open-circuit voZtage - 25 ft. 17.5m) (d) open-circuit voltage - 100 ft. C

(el voZtage at VSP - 25 ft. 17.5m) (7) current in VSP - 25 ft. 17.5~

(g) voZtage at box with VSP L? 25 ft. 17.5m) 

Figure 7 

Propagation of Surges 
mance. For the same setting as Figures 8a 

and 8b, the oscillograms of Figures 8c and 

8d show the case where the HLP has sparked 

over, as indicated by its voltage (8c) and 

current (8d) traces. In Figures 8e and Sf, 

the traces show the voltage (8e) and current 

(Sf) in the VSP for a case where the HLP did 

not spark over (due to the scatter of sparkover or a slight difference in the output of 

the surge generator). This case represents 

the most severe duty to which the VSP would 

be exposed, for a distance of 25 ft. (7.5m), 

and in reality is already likely to be an 

actual lightning stroke on the power system, 

rather than just a "lightning remnant" 

associated with a remote or indirect stroke. 

Figure Sf indicates a crest current of 1200A 

in the varistor, which just exceeds the 

published surge rating of the varistor, 

during laboratory tests. As stated above

this level of current would be reached on

for direct strokes, and for a VSP connect

fairly close to the service box. In a ca

where there would be no HLP installed at 

the box, but only the VSP installed at an 

outlet, the voltage rise in the wiring an

the meter coils would most likely result 

a flashover of the system, which would th

divert the excessive energy away from the 

VSP, just as the HLP did in the test. Of 

course, this diversion may take place in 

undesirable manner, which is precisely wh

the HLP is supposed to eliminate when installed. On the other hand, the sale 

literature for the VSP also specifically 

excludes direct lightning strokes from th

protective ability of the VSP. 

(a) open-circuit voltage (bl short-circuit current 

fcl voltage at HLP when HLP does 

sparkover - VSP at 25 ft. 17.5~1) 

( dl current in HLP after sparkover - VSP at 25 ft. (7.5rnl 

(el voltage at VSP when HLP does not 

sparkover - VSP at 25 f t. 17.5ml 

if) current in VSP when HLP does not 

sparkover - VSP at 25 ft. 17. 5m) 

Figure 8 

Transfer of Surge Conduction 
and the service box, the surge transfer will 

occur at lower current. For instance, with 

100 ft. (30m), the oscillograms of Figure 9 

document the transfer of the surge to the 

HLP at much lower current levels. Oper,.. 

circuit voltage and short-circuit current 

are indicated in Figures 9a and 9b as 

previously. With the VSP at 25 ft., only 

the VSP carries tLe surge as indicated in 

removed 100 ft. (30m) away from the HLP

the latter takes over for this lower av

able current (700 A) and relieves most o

the surge from the VSP, as indicated in 

Figures 9e through 9h. The current flow

in the VSP is now only 125 A (Fig. 9f) w

500 A flowing in the HLP (Fig. 9h). The 

corresponding voltage at the VSP and HLP 

are shown in Figures 9e and 9%. 

'a) open-circuit voltage (b) short-circuit current 

(i.1 VSP at 25 ft. (7.5m) - Voztage of VSP (dl VSP at 25 ft. (7.5m) - Current in VSP 

(el VSP at 100 ft. (30m) - Voltage of VSP (fl VSP at 100 ft. (30m) - Current in VSP 

(gl VSP at 100 ft. f30ml - Voltage of HLP 

Figure 

Transfer of 

(hi VSP at 100 ft. (30ml - Current in HLP 

9 

Surges 
same generator setting as in Figure 9. 

Figure 10c shows the voltage at the end of 

the 100 ft. (30m) line, between the line 

wire and the ground wire (not the ground 

reference, but the ground carried with the 

wire); likewise, Figure lob shows the voltage at the same point between the neutral 

wire and the ground wire, both oscillograms 

recorded with the HLP at the service box 

and the VSP at that line end. These volt

of only 500 V recorded for the same surg

condition in Figure 9e. To check that 

these voltages were not spurious recordi

the oscillogram of Figure 10c was record

with the probe tip connected to its grou

connection, and both of these connected 

the ground wire at the 100 ft. line end

The noise background there is insignific

compared to the recordings of Figures 1

and lob. 

(a) VoZtage between line (black) to 

ground (green) VSP connected ho+.mon h7"nL nwn7 ,.h;er, urn 

at service box. 

(b) Voltage between neutral (whitel to 

ground (green) VSP connected 

between black and white. HLP at 

service box 

(el Noise background check 

Figure I0 

Voltages between Conductors and Ground 

at End of 100 ft. f30rnl Line 

VI, CONCLUSIONS 

The tests on simulated high energy 

surges indicate that a transfer occurs from 

the VSP to the HLP at some current level 

depending on the distance between the two 

devices. 

Even for a short length of wire, the 

VSP is relieved from the surge by sparkover 

of the HLP before excessive energy can be 

deposited in the varistor of the VSP. At 

lower current levels where the voltage in 

the system is clamped by the VSP and thus 

prevents sparkover of the HLP, the VSP absorbs all of the surge energy. 

In all instances, the voltage level 

the VSP is held low enough to protect al

electronic appliances having a reasonabl

tolerance level (600 V in most cases, 

1000 V in extreme cases). Furthermore, 

installatioc of only one VSP in the hous

already provides substantial protection 

other outlets, although optimum protectio

requires the use of a VSP at the most 

sensitive appliance, with additional VSP

if further protection is required for ot

sensitive appliances. 

Home Lightning Protector Specifications 

HOME LIGHTNING PROTECTOR 

Home Lightning Protector ( 5937 

Page I 

Listed by Underwriters' Laboratories (UL) 1/11 sepr L 1.75 Effective Am. 8, 1975 

DESCRIPTION 

The Home Lightning Protector is designed to prevent lightning surges (entering through the wiring) from damaging 

electrical wiring and appliances. The Protector is a sturdy. 

weatherproof, service-proven device that immediately drains 

lightning surges harmlessly to ground. Installed at either the 

weatherhead or service-entrance box, the Protector discharges 

a surge in a fraction of a second. It will perform this protective 

function ova and over again. without any maintenance required, possessing the same long-life valve-type characteristics 

obtainable in higher-voltage distribution arresters. 

The Protector is a two-pole, thrce-wire device designed 

primarily for single-phase 120/240-volt three-wire grounded 

neutral service. It can also be applied to protect three-phase 

circuits where the line-to-ground 60 Hertz voltage does not 

exceed 175 volts. Connection diagrams are included on the 

inside of each carton. 

WHERE TO USE 

Farmers-whose livelihood depends on milking machines. 

incubators, coolers, submersible pumps, and other electrical 

equipment. 

Suburbanites-with considerable dependency on (and investment in) electrical appliances of all sorts. 

Rural Homeownersaften far from fire-fighting equipment. 

and repair facilities. 

Everyone--with electricd equipment exposed to the destructive lightning surges that can enter through directlyconnected overhead secondary power lines. 

The Gmaal Electric Home Lightning LISTED 

Protector 

-can prevent costly appliance repair . ... --can help provide uninterrupted electrical service 

-1-year unit replacement guarantee 

a LIGHTNING PROTECTIVE DEVICE 

PRICES AND DATA Dinribulion TranshrmrcP(O32) 

0-175 ( 2 / 1.0 1 1.2 1 1.1 

' Average valucs. 

(Photo 1219173) 

Fig. 1. Worn- Llehlning Prot-ctor. H-rdwor. (not shown) Is Induded 

In carton ond d.toi4.d below. 

Note - Service protector moy be mounted either side up - with bmchet. It may be 

Suspended by its 

leoda or maunted in 

knockouts in load center or fuse box-. 

'I I 2 l block leads NO. 14 AWG LOd* 

ore (I~nel 

tlnnad (1) white lead No 14 AWG 

COPPS (ground) 

Sec note Na 4 

(21 0 18" holes 

Included rlth orotector 

I Alum~num fkntlng brocket 

2 Alumanurn screw wrlh 

slotted heod 

3 Aluminum mndwt locknut " I 4 An olurnmum nod I mch 1- 

1% furnished to more securely 

mount the arrester 

Nameplate 

Fig. 2. Model No. 9L15BCB002 Horn. Ll.hlnlng P.olrctor 

NOTE: Minimum order quantity is one (1) standard package 

containing twenty-four (24) units. Orders will be accepted for 

shipment from factory stock in- lots of one or more standard packages only. Orders for less than standard package quantities should be referred to local distributors. 

PUBLICATIONS: (Use latest issue) 

Descriptive Bulletin. . . . . . . . . . . GED-4835 

*Changed since May 13, 1974 Isrue. 

PM 7M). 701, 702, 711.714, 721.723, 731.737 
pp

large splkes - such as those which may occur durlng lightning storms -can destroy them instantty. 

SIMPLE, RELtABLE PROTECTION 

Plug the Protector ~nto an 125V AC receptacle. Plug equ~p ment Into the Protector. Sb protect me than one piece d 

equpment, plug a munlple outlet adaptor Into Protector 

The Vdta Spike Protector mths a GE-Movmvar~stor whch absorbs gogerm spkes but does not mtertere w~th normal current tlow. It is des~gned to protect sensltlve elactronic equipment from voltage spkes caused by the "sw~tch~ng of loads' or hghbl~ng str~king the power lines Prolector mll not protect agalnst those rare circumstances where I'ghtnmg strikes the house. paver serv~ce takeoff. or antenna dlrectb 

VOLTAGE SPIKE PROTECTOR HELPS PROTECT 

noME 

APPLIANCES 

N Sets 

Radms 

INDUSTRIAUCOMMERCIAL 

EQUIPMENT 

Computers 

Busmess - . . . . . Machines -. - - HVFI Equ~pmant lndustr~al Contrds 

Electronu: Organs Test Eau~oment 

Major Applia6xs ~dii Equipment 

Some TV manufacturers are incorporating GE-Mw' varistm &tfifhsi',~~,,~~&@,piuce remu rates. These sets 

'.Ti:= 0Dtlon.l 

.. ... .. Wiring Device Department 

Q GE General Electric Co.. Prov.. R. 1.02940 @ 

-7- LELECTRIC - 

cat. NO. VSP-ID