Reprinted from Proceedings, PQA’97 Conference, 1997

Significance: 

Part 2 Development of Standards – Reality checks

Caught among contradictory stories on the need for surge protection as well as unsupported anecdotes of surgerelated failures, the typical consumer is in a quandary on how to best allocate personal resources to protect the

expensive electronic equipment found in a modem household.

To help provide some answers to this quandary, a team of experts developed and engineering guide on the basics

of surge protection. One of the recommendations addresses the issue of ineffective configuration of utility

connections that are responsible for surge-induced failures. This paper served as a progress report, documenting

the status of the project at the end of 1996. An update on this project was reported under Key et al. 1999, which is

included in Part 6 of this Anthology
1. .-- ^ ^. . ^-. ^. .IN l HUUUL I IUN 

Each year !ightning is estimated to be responsib!e for 250 to 500 ml!!ion do!!ars in propew dama

in the United States. This estimate is based on an analysis of insurance claim cempared to clou

4- rrrnn mnrl I;ah+nina Flnnh An+n hnr nlrrnmtnr- nF thn hlntinnml I inhtninn nntnntinn hlnhamrl, An-nrihn

iu-y~uu~ IU II~I 111 III ~y II~OI uaia uy uy~~aiula UI 11 IG IV~LIUI tat LI~I ILI III ly YGLGCIIIUI I IIG~VVVI~, UG~~II

L. . I -4 I 4 i F:..-- -LA. 14 4 non 4~:- ......L..- h,, ,,.i~,rl , .,. ,,,, ,.,+ ,,, ,,b ,,A I,L. uy D~PI ley PL QI 1 I J. 311 I~G auuuL I 333 LI 110 OYOLGI I I I 140 ~IUVIUGU a VGI y ~GI~UI~LG ~UUI I QI IU 1ubail

r. A I A A A L 4 144 "A I A, : 4 1 A 4 C

UI II~IILIIIII~ 11as11e5 tu ~IUUIIU QIIU UI LIE IP~UIL~I IL ~IUUIIU IIQ~II UPI 1311~ 11I LI IP UIIILPU ~LQLP~. r

:-- AL- -1-1- I- I---- ..--A A- ---Z:"- -"A --.. I:-LA-:-- A -I-:-- 

surrw i~~sura~~~t: GUIIIC)~III~~ LIIP uatii I lave uewl useu tu bur IIIIIII UI UPI ly II~I I~IIIII~ ualllaye ulalrl
A iypicai modern residence contains many eiecironic and muiti pori appiiances. in order io iden

speciiic protection practicesj a typicai resiaence was deiinea -. wiin eiectronic appiiances and system

illustrated in various rooms 8s shown in figure 1. ! ne main systems are home entertainme

Inc!udlng c&!e TV, hnme ~fflce Ir\c!ndlng fp!pphQnpl and p!pcf:-QnIc klfchen app!lancec. Oth

cammen vu!nerab!e systems are home security, intercem, sate!!ite receiver, garage doer epene

and laundpj equipment. Generelly, my system with micrselectrmics plus expsure due t~ p~:v

and signal wiring can be found in lightning damage claim :epo;ts. 

:I : ...- "- --&I--"- -- AL- -..--- I ~GI lr 11ba1 11 ~put~ welt: gait wed UI I u ~e enpe~ted surge threat and the key eiemeiits of protectio
different experts had different backgrounds and experiences. At the end all agreed on essen

principles of how to protect sensitive equipment. However, specific devices and procedures th

could be applied case by case were more difficult to obtain. Also, there is currently no informat

aboiji compaiiGiiiv ieveis and points of -"iiiiierabiiiv for rnaiiji modern eieciro

appliances and systems. Consequently, specific installation methods and precise recommendatio

on how to protect these electronic systems from surge threats are not yet fully developed. 

A few appliances seem to have varying susceptibility to surges, The most notable losses, accord

to insurance claim records, are telephones and modems, computerized equipment, TV, VCR a

satellite receiver systems. These are generally multi-port appliances-that is, appliances connect

to several different systems, such as an entertainment center connected to power, cable, a

telephone or a security system connected to power, sensor, and control. These multip

connections, and the likelihood of potential differences between them, are believed to be ma

factors in surge damage susceptibility of many residential appliances and systems. 

Lightning is not the only threat, but remains a dominant one.. Most of the Continental United Stat

experience at least two cloud-to-ground (C-G) flashes per square kilometer per year. About one h

of the area will see three C-G flashes per km2, which is equivalent to about 10 discharges p

square mile per year. The maximum flash densities are found along the southeastern Gulf Coa

and the Florida peninsula, where the values approach 20/km2 or 50/mi2. Overall about 30 milli

C-G flashes strike the United States each year, and lightning is clearly among the nation's mo

severe weather hazards. 

In high lightning areas, perhaps a threshold of three C-G flashes per square km per year, som

degree of structural lightning protection is recommended. This threshold may be economica

justified by the growing value, and vulnerability, of residential electronic systems. There is go

:-L..--.+:-.- A,.-:I.-.C,l.-. n- I-.-.., +rr rrrrnrrm-l;rrC, +C,;- -rn+rr.-.+;n- Dm-;- I;rrh+m;-m -rrr+nrr+;n- -rrr.-.+:-rr- A

II IIUI III~LIVI I avallault: UI I I IUW LU abbull lp1131 I LI 113 ~IVLC~LIUI I. ua31b II~I ILI III ly ~IVLCLLIUI I plabi~b~a

well defined in the Lightning Protection Code, NFPA 780. An illustration of the basic elements 

this protection is provided in figure 2. These protection techniques will not eliminate surges th

enter the residence either via different wiring systems-including the grounding electro

syste~~: cwpled into :vi:ing from nearby flash.es. In additim to the lightning threg!, some bss

household appliances can act as surge generators, for example a light switch or a furnace ignit

Protection against these surges can take several forms. The possibilities are: preventing the sur

at its origin (impossible for lightning and difficult for surges associated with normal operation of t

power system), diverting the surge to ground as it impinges on the building, before it enters t

building (the most effective approach), and finally, clamping by a surge protective device (SPD) 

the equipment (either by an add-on, plug-in, or built in SPD). Of these three approaches, only t

service entrance and add-on SPDs are options available to the end-user. Service entran

protection may be offered by the local utility. If not, a licensed electrical contractor may off

installation service. In either case installation of service entrance protection must be done by 

professional. Various locations for power line or transient-voltage surge suppressors (TVSS) a

shown in figure 3. 
Legend - 

Air terminal spaced 6 meters (20 ieet) apart aiong ridges and within 0.6 meter (2 ieetj oi 

ridge ends 

Down conductors (minimum of two) 

Grounding rods; minimum of two, at least 3 meters (1 0 feet) deep 

Roof projections such as weather vanes connected to grounding system 

Air terminals located within 0.6 meter (2 feet) of outside corners of chimney 

Dormers protected with air terminals 

Antenna mast bonded to roof ground conductor 

Gutters and other metal objects bonded to grounding system 

Surge arrester installed at service panel to protect appliances 

10. Transient voltage surge suppressors installed at receptacles powering sensitive electronics 

Figure 2. Typical comprehensive lightning protection of a residence (reprinted with permission 

from Underwriters iaboratory inc.j 

\ 

Power Line Suree Protectors 

Service Entrance Arresters @,a,@,@ 

Branch Circuit Suppressor @ 

Receptacle Plug-in Suppressor @ 

Plug Strip with Suppressor 8 

Figure 3. Options for power-line surge protection in a residence 
A fundamental application issue in surge protection is grounding. Proper grounding is critical fo

the case of ground-seeking surges such as lightning currents. However, even more critical for mult

port appliances or systems is the difference in ground reference between port connections. Th

vuinerabiiiiy issue is addressed in the Nationai Eiectric Code (NFPA 70j, which requires that in

grounding conductors of all systems entering a facility be bonded together. As shown in figure 

(left), a split bolt is used to bond different system grounding conductors to the power system 

grounding electrodes. Unfortunately this bonding is not always done and a common, but incorrec

and dangerous to personne! 2nd equipme~f, scen=rrio is shwn ir! figwe 4 (right). 

#6 AWG to ground bus 

1- ,L .- .A. ., - -- 2 wrlw SKU LUIIUUI~ ail 

Driven ends of the conduit 

Ground Rod shall be bonded to the 

groundmg wlre. 

CATV and 

telephone 

Electnc services remote 

Meter 

? A single ground 

I not be less than 

rod, may or may Each service has its own 

ground rod and none are 

1 25 ohm, as connected together 

required by code 

Figure 4 - Minimum code-required service grounding (left) and commonly found, but incorrect 

grounding of existing house (right) 

The incorrect grounding of the house, figure 4 right side, was identified by the study group as th

primary problem in residential system surge protection. Even with independent surge protection o

the power and communications ports, smart electronic appliances are left vulnerable to surges

During a surge, an elevation of only one of the port reference potentials relative to the other(s) ca

upset or damage appliances. The problem is depicted in figure 5, which shows the connection o

a fa~siiiiil~ iiiachiiie (FAX), to bolh the power system and commi;nication syskm. The SPE (als

called TVSS in the industry jargon) on the power port of the FAX can be built-in or installe

externally by the end user. The arrester at the service entrance, shown in dotted lines, may or ma

not be present. According to standard practice, the telephone company has installed a networ

interface device [NID) at the point of entry. The NID is installed primarily to protect the telephon

system and human users from hazards of faults and surges that travel from the premises towar

the telephone system, rather than to protect from surges impinging from the telephone system int

the premises. Nevertheless, should a surge impinge on the telephone system, the NID will divert 

to ground, in this case the nearest cold water pipe. 

Consider the case of a surge impinging on the entrance of the telephone system. The surge curren

shown as "Surge i" in figure 5 flows in the long path from the entrance of the telephone system t

the grounding point in common with the power system entrance. The inductance of this path i

&.....:--ll.. &--- -5 -:-"- I--...-:-- .....A &LA -..,.-- -..""--& --- ":..A 4- --.,-"-I I-..-A--A ' LY~ILCIIIY L~II~ U IIIILIU-I I~IIII~~, CIIIU LI le ~UI ye LUII~I 11 MI I 115e LU aevela I IUI IUI~U allpelea iii on

microsecond. The resulting voltage drop along the current path from the telephone port to groun
y gppy y g

Assuming 10 pH for L and 500 Alps for dildt, the voltage drop that appears between the power po

and telephone port of the FAX is Vdifference = 10 pH x 500 A11 ps = 5000 V. This voltage is like

sufficient to cause a flashover on the printed circuit boards, or a semiconductor failure in the FA

Most FAX failures can be readily explained by the elevated reference potential associated wi

independent surge protection of the two ports. 

Power rL;; TVSS System l.4 Arrester 

Entrance 'I:' 

I T I L Cold Water Pipe Jt I 

Surge i 

Figure 5. Surge voltage potential difference develops between two protected ports of appliance 

1 TITmPnOIIPTFII nALTnTlr- lnt: 11~1~~3151~~ DW~VLJIIVU 

POINT for connection of 

telephone, television, and radio 

antenna grounding wires. 

Electric Meter 

ground. A 112" dia., 20'-0 long steel 

rod or #4 bare copper wire encased in 

the concrete footing. 

When steel conduit is used to protect 

grounding wire, all ends of the conduit 

shall be bonded to the grounding wire. 

Figure 6. Recommended service grounding for enhanced surge immunity 
g

ppy 

services, power and telephone, must enter at the same point and must be bonded together at th

point. The NEC requires bonding together the two service grounds, but does not require entry at th

same point. As shown in figure 5 system bonding is provided by the cold water pipe, which 

:I -- a- L : n..r r~, ..-I+,,, ,,c,,r:,~ ~:rr,,,,,, ,~:II ,,,. .,, L. ,,,. .,, ,I r

eleL;LrIC;ally LUIIIIIIUII tu UULI I selvIC;eb. DUL LII~ vu~~ayt: PULGI ILI~ UIIIGIGIIG~: WII UGGUI~ uetiauat: UI LI

separated entry points. Figure 7 shows the details of how an inter-service bonding point might b

constructed and installed. 

\TO GROUND BUS IN PANEL 

INTERSYSTEM BONDING POINR 6x 6 

x 3" weatherproof box with a 6 position 

grounding lug suitable for #14- #6 wire. Labels 

shall be permanently attached. This is for 

connection of telephone, television, and radio ELECTRICAL METER 

antenna grounding wires. 

G 

AWG BARE COPPER 

WEATHERTIGHT FITTING 

GROUNDING BUSHING USE1 

rOR iviETAiiiC 

Figure 7. Details of the essential intersystem bonding point 

Beyond grounding, for a surge-protective device (SPD) to be effective it must provide a protectiv

level, or surge clamping, below a level potentially harmful to the equipment. But the level shou

be so i()w that device absorbs energ.y i" its iife is or ii faiis premature

under the stresses resulting from a temporary overvoltage. This principle holds for power, signa

telephone or cable, albeit at different threshold levels. The SPD must also have a surge curre

handling capability commensurate with the surge currents that might occur at that location. 

The application of an SPD satisfying the criteria cited above must also take into consideration th

rest of the circuit where the device is to be applied. For instance, operation of the SPD must n

cause adverse side effects. In the case of protection of load equipment which is connected to th

power system as well as to a communication system (telephone, cable or satellite TV) particula

attention must be given to this issue. It is possible that protecting the two interfaces of th

equipment, each with a separate SPD, might leave the equipment in jeopardy as the result o

overvoltages appearing between the two separate systems, see Key, Martzloff, [2,3]. 

Because effective operation of an SPD invoives aiveriing tine surge to ground, the actuai groundin

system and its connections in a residence must be taken into consideration. The impedance of th
pats ote goudg systes oted eaete ost possbe staead a oatoote 

NEC-is to provide separate grounds for the power system and for the communications system

Even so, many instances are found of such multiple grounding practice in residences, eithe

intentionally, or by accident. A typical example is services such as cable TV that used the meta

_ -1 -..*_la I-. .--I -- :I- ---..--I:-- -----a I:-- TI-:^ ^"..^--^.^-^-. ... ^^ ^- ^^^^-&^I-l^ -"^..--I pipe or an uuruuur 1aur;eL as 11s yruur IUII ~y cur lr letiuur I. I r 11s ar rar lyer~ler 11 was ar I al;c;epiaule yruur IU 

at the time of installation, but can easily be defeated when the water piping inside or outside the 

house is replaced with plastic. So an improper separation of grounds is camouflaged by the shor

link of steel pipe going through the foundation wall and sealed in the concrete. 

I Arrester 

Suppressor I 1 (362.41 4 C62.41 

Category 

Location 

B Category 

Location 

A 

- 

Figure 8. Cascade arrangement of upstream and downstream SPDs 

OPEN AND UNRESOLVED ~SSUES 

Several issues remain open at this point and will be addressed in the Guide. We hope that 1 the 

Guide will resolve some of these issues, but others might take more research to resolve. In some 

cases an iterative process be among uiiiiiies, and eqLIipmeni inan"factLIrers 

to optimize the process instead of exchanging blame. 

One important problem that can be resolved by future research is the coordination of an SPD 

cacade, (see figure A). !f the se!ectinn nf a sewice entrance SPD is appropriately coordinated with 

the installation of appropriate SPDs within the residence, then the resources will be allocated in an 

effective manner, both technically and economically (see Martzloff, Lai [4,5]). Clearly, this 

coordination can only be achieved by cooperation of the utility, SPD manufacturers, and premise 

occupants and full knowledge of the characteristics of the SPD's and the surge itself. 

Another problem that can be resolved is the effective protection of equipment connected to two 

different systems. The concept of equalizing ground references has now been sufficiently 

advocated to motivate SPD manufacturers to offer SPDs with both power and telephone protection

or both power and i'v' protection, in the same enciosure (see figure 9j. The iEEE designation o

"Surge Reference Equalizer" was published in 1992, [6]. It has not yet found general use in the 
, ppy p

of surge reference equalizers. At this point, the user is left with some uncertainty as to how effectiv

a particular brand may be compared to another. In this intensely competitive market, claims an

counter claims need to be sifted via experiment, a role that some utilities might be willing to assum

REFERENCE \ 

\ EQUALIZER 

71 

I Service 

tntrance -1 

- I 

Branch Circuit I 

! I 

Ground I I u ! 0 

rod Cold Water Pipe 

Note: Local codes may require bonding the coaxial shield at the 

outside or inside of the building. 

Figure 9. Surge reference equalizer to protect multi-port appliances 

Last but mt !east, app!icatim of SPD or !ightning protection must consider risk ana!ysis. Protectio

of appliances against surges generated within a building, or impinging at the power servic

entrance, can be accomplished with relatively low cost. However additional investment may b

required if multiple services (telephone, TV, and power), and multiple grounds are present. Extern

protection against a direct lightning strike may also be needed with cost depending on the structur

and location. In any case good practice should be sought in the face of an "act of God" even

where damage can be minimized by observing appropriate rules of grounding, bonding, an

protection, as the Guide will propose. However, even with the best practices some degree of ris

will always remain. 

More aiieniion to siiige pi~i~~ii~ii practices is warranted bjj the increased iise and iiihei~iit SiiiCj

vulnerability of residential electronic systems and appliances. While there is consensus on the bas

principles of protection, specifics and installation procedures for cost-effective applications are no

readily available. By applying data and practices for grounding, lightning and surge protections t

specific appliance sets; these needed details are beginning to take form. To be successful 

Consumer-Oriented Guide on surge protection will have to address complex topics of whole-hous

protection including such techniques as multi-port devices and cascade coordination. Whe

complete, the Guide should provide a comprehensive document that insurance companies can us

to educate their policyholders, employees, and agents about how to reduce damage resulting from 

surges caused by lightning.