Electrical Protection of Cellular Radio Sites

François Martzloff

General Electric Company

Schenectady NY

Reprint of University of Wisconsin lecture handout, May 1983

Significance:

Part 6 – Textbooks, tutorials, and reviews

This invited lecture was presented at the Extension Division of the University of W isconsin at a time w

cellular telephone (hence the somewhat obsolete wording of the title) had not yet reached its wide

acceptance, but system designers were rightfully concerned with surge protection of that emerging

technology. One particular aspect of a cell phone relay tower is that it is often installed on hilltops wh

securing low-impedance earthing electrodes can be difficult.

The text handed out paralleled a slide presentation – not included in this reprint – calling attention to 

three ports where surges could impact operation and, at worst, integrity of a “cellular radio site” (hand

units were not included):

! connection to the power supply system

! connection to landline network(s)

! tower antenna acting as lightning air terminal

W ith now 20 years of experience in operation and protection of cell phone facilities, the protective

techniques might have evolved, but the concerns remain valid.
Cellular Radio 

ELECTRICAL PROTECTIO

Lectu

May 13, 198

University of Wisconsin-Extension 

Madison, Wiscons

Frangois D. Martzlo

Corporate Research and Developme

General Electric Compan

Schenectady, New York 1234

(518) 385-394
ELECTRICAL PROTECTION OF CELLULAR RADIO SITES 

INTRODUCTION 

Hardware installed at a cellular radio site will be exposed 

towtransient overvoltages which can upset the data 

processing or, worse, cause permanent damage of sensitive 

electronic components. 

The hazards associated with lightning or power system 

switching transient overvoltages (surges) have existed ever 

since electronic equipment began to displace the older 

electro-mechanical devlces. Therefore, these hazards are 

not a new threat to the successful operation of cellular radio 

systems; rather, the combination of three ports connected to 

the hardware presents some new problems, but they can be 

solved by proper application of known techniques and 

devices. The connection to the power supply, the connection 

to the telephone cable plant, and the exposure of the 

antenna to lightning strikes are three ports through whlch 

upsetting or damaging transient overvoltages can impinge 

on the hardware. While a click in a telephone conversation 

- would not be objectionable, an upset of digital commands 

might be. Permanent damage, of course, should be avoided 

as much as possible. 

This presentation will give an overview of the nature of 

the surges likely to enter by each of the three ports. A brief 

review will then be given of the techniques and devices 

available for diverting or attenuating these surges. The 

effectiveness of these techniques and devices has been 

demonstrated in other existing electronic systems; therefore, 

reliable protection of cellular radio hardware can also be 

expected under most operating conditions. 

IMPINGING SURGES 

Power Supply System 

The power supply system for a slte will be whatever the 

local electric utility supplies to its customers. Studies and 

standards have been published, describing the nature of the 

surges that can be expected to occur on such a power supply.('-3' 

Fortunately for the reliability of the cellular radio equipment, the actual power supply to the electronics is a dc 

source, needed to assure continuity of service in case of 

failure of the utility system. This supply takes the form of a 

dc battery with a charger powered by the utility grid. Provided that the charger can withstand the impinging surges 

from the utility supply, the battery will act as a very effective 

buffer for the disturbances, including surges, occurring in the - utility grid. 

The existence of power supply surges has been rec

nized in the telephone industry, and FCC regulations (P

68) do provide a standard for withstand capability of the 

input of electronics interfacing the power supply and the 

ble plant. Therefore, cellular radio hardware will be requi

to meet the same requirements as all other peripherals n

being used at subscribers facilities. The FCC standard i

voltage impulse of 2500 V peak with a duration of 10 

and a short-circuit current of 1000 A,'4' It is a severe te

but equipment designed to withstand that impulse has be

found to have satisfactory survival capability in serv

which is the ultimate proof that the standard is appropriat

Cable Plant 

The wire connection of the cell hardware to the te

phone system will present the same characteristics as 

conventional connection to a multi-line subscriber. The te

phone industry has a long and successful experience 

dealing with surges that can appear on the wlre pairs. 

course, there has been a downward trend in the withsta

capability of terminal equipment as old electromechani

equipment has been superseded by modern solid-sta

equipment. Fortunately, concurrent advances in protect

devices have enabled system operators to maint

reliability of these more sensitive components. A wlde ran

of protective devices is available, meeting requireme

designed specifically for this type of ser~ice.'~-~' 

Antenna Feed 

The very nature of an antenna, especially a top-mount

omni-directional antenna, makes it a very good lightning r

Thus, there is a definite likelihood that a lightning bolt w

from time to time, terminate on an antenna. It is possible 

provide some protection - mostly by diverting the lightn

current to earth - but some damage to the antenna by 

current burning effect, or to the electronics by the overvo

age, is still likely to occur. The probability of a tower be

hit by a lightning bolt can be estimated with reasonable 

curacy for the general case, but not with good precision 

any particular site. Equations, which are based on actual 

perience, relate the number of strikes terminating on a 

object to its height and geographical lo~ation.'~-"~ A rec

study has been published, assessing the lightning dama

threat in the United States,(12' which provides a better p

ture of the situation than the traditional "isokeraunic ma

based on the number of days where thunder is heard. 
Ground Potential Differential 

The three sources of surges discussed above have all 

been taken one at a time, with the implication that they 

might carry a surge voltage within themselves. This type of 

surge is the so-called "normal mode," or "transverse mode." 

In site hardware, the power supply and the antenna feed 

conductors include a connection to ground, while the telephone connection will be a balanced pair. There is another 

way for surges to appear, the so-called "common mode" 

where, for instance, two pairs of telephone cable are simultaneously elevated in potential above ground. However, as 

the telephone terminal equipment is connected across the 

pair, the amplifiers inputs are not stressed between terminals, but the insulation with respect to ground will be 

stressed. 

Each of the three ports at the cell can bring a surge with 

respect to the ground, and therefore produce different potentials with respect to ground, unless adequate common 

grounding is applied. It is a dangerous fallacy to proclaim 

that electrical noise can be avoided by using separate 

grounds. 

FUNDAMENTAL PROTECTION TECHNIQUES 

Protection of a power system, of a communication system, or of an electronic black box against the threats of the 

surge environment can be accomplished in different ways. 

There is no single truth or magic cure ensuring immunity 

and success, but, rather, there are a number of valid 

approaches that can be combined as necessary to achieve 

the goal. The competent protection engineer can contribute 

his knowledge and perception to the choice of approaches 

against a threat which IS imprecise and unpredictable, 

keeping in mind the need to balance the technical goal of 

maximum protection and the economic goal of realistic protection at an acceptable cost. However, just as in the case 

of accident insurance, the cost of the premium appears high 

before the accident, not after. 

A discussion of fundamental protection techniques that is 

limited in time and scope has the risk of becoming an inventory of a bag of tricks; yet, there are some fundamental 

principles and fundamental techniques that can be useful in 

obtaining transient immunity, especially at the design stages 

of an electronic system or circuit. All too often, the need for 

protection becomes apparent at a late stage, when it is 

much more difficult to apply the fundamental techniques 

which are most effective and economical when 

implemented at the outset. 

Protectlon techniques can be classified into several 

categories according to the purpose and the system level at 

which the engineer is working. For the system as a whole, 

protection is primarily a preventive effort. One must 

consider the physical exposure to transients - in particular, 

the indirect effects of lightning resulting from building 

design, location, physical spread, and coupling to other dis- 

- turbance sources - as well as such inherent susceptibility 

character~stics as frequency response and nominal voltage. 

For many system components or electronic black box

the environment IS often beyond the control of the design

or user, and protection becomes a curative effort - learni

to live and survive in an environment which is impose

Quite often this effort is motivated by field failures, so th

retrofit is needed. The techniques involved here tend to 

the application of protective devices to circuits or a sear

for inherent immunity rather than the elimination of surges 

their origin. However, in the case of cellular radio hardwa

the opportunity exists to integrate all protective measures 

the outset of the design and thus optimize the protection. 

Another distinction can be made in classifying protect

techniques. Granted that surges will be unavoidable, o

can attempt to block them, divert them, or strive to wi

stand them; the latter, however, is generally difficult 

achieve alone. 

SHIELDING, BONDING, AND GROUNDING 

Shielding, bonding, and grounding are three interrelat

methods for protecting a circuit from external transien

Shielding consists in enclosing the circuit wiring in a co

ductive enclosure, which in theory cancels out any ele

tromagnetic field Inside the enclosure; actually, it is more 

attenuation than a cancellation. Bonding is the practice 

providing low-impedance connections between adjace

metal parts, such as the panels of a shield, cabinets in 

electronic rack, or rebars in a concrete structure. Groundi

is the practice of providing a low impedance to "eart

through various methods of driving conductors into the s

Each of these techniques has its limitations, and each c

sometimes be overemphasized. 

Shielding 

Shielding conductors by wrapping them in a "grounde

sheath or shielding an electronic circuit by enclosing it in 

"grounded" conductive box is a defensive measure th

occurs very naturally to the system designer or laborato

experimenter anticipating a hostiie electromagnetic enviro

ment. Difficulties do arise, however, when the concept 

"grounded" is examined in detail and when the objectives 

shielding for noise immunity conflict with the objectives 

shielding for lightning surge immunity. 

A shield can be the slze of a matchbox or a building; 

can cover a few inches of wire, or kilometers of buried 

overhead cables. "Grounding" these diverse shields is n

an easy thing to do because the impedance to earth of t

grounding connection must be acknowledged. The situat

is made even more controversial because of the conflict b

tween the often-proclaimed design rule "ground cab

shields at one end only." a rule justified by noise immun

performance, in particular common mode noise reduction 

and the harsh reality of current flow and Ohm's law wh

lightning strikes. 

This conflict is actually very simple to resolve if reco

nized in time: provide an outer shield, grounded at bo

ends (and at any possible mtermediate points); inside t

shield the electronic designer is then free to enforce 
single-point grounding rules. In this approach, the only drawback is the hardware cost of "double shields." However, in 

many installations there is a metallic condult through whlch 

the cables are pulled; with simple but close attention to 

maintaining the continuity of this conduit path, through all 

the joints and junction boxes, a very effective outer shield is 

obtamed at negligible additional cost. In the case of underground conduit runs, the most frequent practice is to use 

plastic conduit, which unfortunately breaks the continuity. 

System designers would be well advised to require metal 

conduits where the circuits are sensitive or, at a minimum to 

pull a shielded cable in the plastic conduit where the shield 

is used to maintain continuity between the above-ground 

metal conduits. That additional cost, then, is the insurance 

premium, which is well worth accepting. 

Bonding 

We have already mentioned one aspect of bonding In 

describing the need for continuity of the outer shield. 

Another instance of bonding occurs where the shield of an 

incoming cable is connected to the box of the circuit or to 

the building ground. The principle is simple: the shield can 

be viewed as an extension of the box, and thus bonding of 

the shield to the box should be continuous over 360". In 

practice, unless special connectors are used, this is difficult 

to achieve, for often a shielded cable is terminated at a connection board with the shield peeled back and turned into a 

pigtail, which In turn is connected to the "ground" terminal 

of the connection board. One can imagine the many possi- - ble variations of current flow, with the shield current now 

flowing in the pigtail and the creation of the corresponding 

electromagnetic radiation at the point of cable entry. 

Adjacent cabinets in a lineup must be bonded together 

for safety as well as transient and noise immunity. In principle, a flat strap has a lower inductance than a round wire of 

the same area. Actually several strategically located smaller 

wires provide a much more effective bond than one massive 

strap either round or flat. The difficulty lies in implementing 

this alternate view, and overcoming the comforting sight of a 

large grounding strap at the bottom of the cabinet lineup. 

Such a strap does no harm and is a good safety practice, 

but it may not do as much good as expected from the point 

of view of surge protection. 

Grounding 

Grounding, which is also referred to as "earthing," has 

different meanings as well as different roles. The prlrnary 

definition is the connection of the circuit, shield, or reference 

to "earth." But what is "earth"? System designers, construction crews, inspectors, and technical conference authors are 

concerned with establishing, measuring, and maintaining a 

low ground "resistance," often determined by dc measurements on rods driven into the ground. Driving rods into the 

ground does not ensure a low ~mpedance under the transient conditions of high rate of current change associated 

with lightning discharges. This remark is not intended as a 

criticism of the efforts going into achievmg a low resistance 

but, rather, to alert the system designer that there is mor

it than just low resistance, and that one can overdo the 

of burying copper in the gro~nd.~'~-~~' 

When one deals with a reasonably compact system, b

cabinet-size, room-size, or building-size, it is more effec

to view the grounding as a well-bonded connection to 

outer shield (if any), building frame, or cabinet enclos

The resistance (impedance) from that reference to "earth

not very significant as long as other wires at "ground" po

tial are not brought to the system. This desirable situatio

best obtained with single-point grounding approaches

opposed to multiple grounding. There is a controversy 

the respective advantages and disadvantages of the two 

proaches for general cases, but examination of the cha

teristics of specific cases will resolve the controversy. S

there is little chance of dealing with an absolutely isol

system, the question is: What should be done with inc

ing wires? These wires can be isolated from the l

ground during normal operation, but one must recog

that, during transient conditions of lightning surge or po

system faults, high voltages will appear across these is

ed wires and local ground, voltages which, in some ca

are totally beyond the withstand capability of insula

That insulation, then, must be protected by suitable dev

which in fact do connect the wires to the local ground 

the duration of the transient. This type of grounding is 

function of transient suppressors. 

It is a dangerous illusion to believe that lightning eff

can be eliminated by the isolation of conductors or sub

tems. It is much safer and quite acceptable, if include

the design, to prov~de bonding during transient condition

suitable protective devices. The lmportant point 

remember is that while lightning is a fairly weil-def

phenomenon, with known characteristics and effects in 

eral, its probability of occurrence at a particular locatio

unknown. For the successful operation of a sys

foresight is needed In applying fundamental protect~on t

niques at the beginning. 

PROTECTIVE DEVICES 

Various devices have been developed for protec

electrical and electronic equipment against transients. T

are often called "transient suppressors" although, 

accuracy, they should be called "transient limite

"clamps," or "diverters" because they cannot really suppr

transients; rather, they limit translents to acceptable le

or make them harmless by diverting them to ground. 

There are two categories of transient suppressors: th

that block transients, preventing their propagation tow

sensitive circuits, and those that divert transients, limi

residual voltages. Since many of the translents origin

from a current source, the blocking of a transient may 

always be possible; the diverting of the transient is m

likely to find general application. A combination of diver

and blocking can be a very effective approach. This 

proach generally takes the form of a multistage circ
where a first device diverts the transient toward ground, a 

- second device - impedance or resistance - offers a restricted path to the transient propagation but an acceptable 

path to the signal or power, and a third device clamps the 

residual transient. Thus, we are primarily interested in the 

diverting devices. These diverting devices can be of two 

kinds: short-circuiting devices (crow-bar) or voitageclamping devrces. 

Because the technical and trade literature contains many 

articles on these devices, we shall limit the discussion of the 

details and refer the reader to References 16-29. We shall, 

however, make some comparlsons to point out the significant differences in performance. 

Crowbar Devices 

Tbe principle of crowbar devices is quite simple: upon 

occurrence of an overvoltage, the device changes from a 

high-impedance state to a low-impedance state, offering a 

low-impedance path to divert the surge to ground. Spark 

gaps, including gas tubes and carbon blocks extensively 

used in the telephone industry, are examples of crowbar 

devices. 

The major advantage of the crowbar device is that its low 

impedance allows the flow of substantial surge currents 

without the development of high energy within the device 

itself; the energy has to be spent elsewhere in the clrcuit. 

This "reflexion" of the impinging surge can also be a disadvantage in some circuits when the translent disturbance 

- associated with the gap firing is being considered. Where 

there is no problem of power-follow (discussed below), such 

as in some communicatron circuits, the spark gap has the 

advantage of very simple construction with potentially low 

cost. 

The crowbar device, however, has three major limitations. 

One is the volt-time sensitivity of the breakdown process. 

As the voltage increases across a spark gap, significant 

conduction of current - and hence the voltage limitation of 

a surge - cannot take place until the transition occurs to 

the arc mode of conduction, by avalanche breakdown of the 

gas between the electrodes. The load is left unprotected 

during the initial rise because of this delay time (typically in 

microseconds). Considerable variation exists in the sparkover voltage achieved in successive operattons, since the 

process is statistical in nature. This sparkover voltage, in 

addition, can be substantially higher after a long period of 

rest than after successive discharges. 

The second limitation is associated with the sharpness of 

the sparkover, which produces fast current rises in the circuits and, thus, objectionable noise. An effect of this fast 

current change can be found in some hybrid protective 

systems. The gap does a very nice job of discharging the 

implnglng high-energy surges, but the magnetic field associated with the high rate of current change (diidt) induces a 

voltage in the loop adjacent to the secondary suppressor, 

adding what can be a substantial spike to the expected secondary clamping voltage. 

A third limitation occurs when a power current from 

steady-state voltage source follows the surge discha

(follow-current, or power-follow). In ac circuits, this pow

follow current may or may not be cleared at a nat

current zero. Additional means, therefore, must be provi

to open the power circuit if the crowbar device is 

deslgned to provide self-clearing action within the speci

limits of surge energy, system voltage, and power-fo

current. This combrnation of a gap with a current-limit

nonlinear varistor has been very successful in the utility 

dustry as a surge arrester or surge diverter. 

Voltage-clamping Devices 

Voltage-clamping devices have varlable impeda

depending on the current flowing through the device or 

voltage across its terminal. These components show a n

linear characteristic - that is. Ohm's law can be applied, 

the equation has a variable. Impedance variation does 

contain discontinuities, in contrast to the crowbar dev

which shows a turn-on action. As far as their volt-amp

characteristics are concerned, these components are ti

dependent to a certain degree. However, unlike the sp

over of a gap or the triggering of a thyristor, time dela

not involved. 

When a voltage-clamping device is installed, the ci

remains essentially unaffected by the device before 

after the transient for any steady-state voltage below cla

ing level. Increased current drawn through the device as 

surge voltage attempts to rise results in voltage-clamp

action. 

The principle of voltage clamping can be achieved 

any device exhibiting this nonlinear impedance. 

categories of devices, having the same effect but opera

on very different physical processes, have found accepta

in the industry: the polycrystall~ne varistors and the sin

junction avalanche diodes. Another technology, the 

selenium rectifier, has been practically eliminated from 

field because of the improved characteristics of mo

varistors. 

Avalanche diodes, the Zener diodes, were initially app

as voltage clamps, a natural outgrowth of their applica

as voltage regulators. Improved construction, specific

aimed at surge absorption, has made these diodes 

effective suppressors. Large-diameter junctions and 

thermal impedance connections are used to deal with 

Inherent problem of dissipating the heat of the surge 

very thin single-layer j~nction.'~~~~~~ 

The advantage of the avalanche diode, generally a 

silicon junction, is the possibility of achieving low clam

voltage and a nearly flat volt-ampere characteristic ove

useful power range. Therefore, these diodes are wldely 

in low-voltage electronic circuits for the protection of 

15 V logic circuits, for ~nstance. For higher voltages, 

heat generation problem associated with single junct

can be overcome by stacking a number of lower vo

junctions, admittedly at some extra cost. 
The term varistor is derived from its role as a variable 

- resistor. It is also called a voltage-dependent resistor, but 

that description tends to imply that the voltage is the independent parameter in surge protection, which is not 

correct. Two very different devices have been successfully 

developed as varistors: silicon carblde disks have been 

used for years in the surge arrester industry, and, more recently, metal oxide varistor technology has come of age.(281 

In silicon carbide varistors, the physical process of nonlinear conduction is not completely understood, and the 

manufacturing of the material, successful as it is, has 

remained an art. It appears that the process takes place at 

the tips of the grains of silicon carbide which are held together by a binder. The story goes that the device action 

was found accidentally by having a grlndlng wheel, on a 

disorderly work bench, accidentally connected to an experimental circuit; for many years silicon carbide varistors 

indeed looked like grinding wheels, each complete with a 

hole in the center. 

Metal oxide varistors depend on the conduction process 

occurring at the boundaries between the large grains of 

oxide (typically zinc oxide) grown in a carefully controlled 

sintering process. The physics of the nonlinear conduction 

mechanism have been described in the literat~re.'~~-~~' 

COMPARISONS OF PROTECTIVE DEVICES 

Spark Gap Versus Varistor 

- The choice between these two devices will be influenced 

by the inherent characteristics of the application. Where 

power-follow is a problem, there is little opportunity to apply 

a simple gap. The operation of a gap on a power system 

can cause sags in the voltage when the crowbar action persists until the next current zero; varistors do not cause these 

sags. Where very steep front transients occur, the gap alone 

may let an excessive voltage go toward the "protected" 

circuit until the voltage is limited by sparkover. Where the 

capacitance of a varistor is objectionable, the low inherent 

capacitance of a gap seems attractive. If very high energy 

levels (compared to the lower levels inherent with the 

crowbar action of a gap) are likely to be deposited in a 

varistor by an impinging surge, then a high capaclty surge 

arrester near the service entrance may be combined with a 

lower clamping voltage varistor installed farther into the circuit. This combined protection, however, requires adequate 

coordination between the two suppressors.'301 

Avalanche Diode Versus Varistor 

The basic performance characteristics of these two 

devices are similar, and therefore the choice may be dictated by clamping voltage requirements (the avalanche diode 

is available at lower clamping voltages), by energy-handling 

capabilities (the varistor is generally higher in capability per 

unit of cost), and by packaging requirements (the varistor 

material is more flexible and does not require hermetic 

packaging). 

Failure Modes 

Failure of an electrical component can occur because 

capability was exceeded by the applied stress or beca

some latent defect in the component went by unnotice

the quality controi processes. While this situation is 

recognized for ordinary components, a surge protective 

vice, which is no exception to these limitations, tends to 

expected to perform miracles, or at least to fail gracious

a "fail-safe" mode. The term "fail-safe," however, may m

different failure modes to different users and, theref

should not be used. To some users, fail-safe means that 

protected hardware must never be exposed to an overv

age, so that failure of the protective device must be in 

fail-short mode, even if it puts the system out of opera

To other users, fail-safe means that the function mus

maintained, even if the hardware is left temporarily un

tected, so that failure of the protective device must be in 

open-circuit mode. It is more accurate and less mislea

to describe failure modes as "fail-short" or "fail-open,

the case may be. 

SPECIFIC APPLICATIONS 

Trial systems of cellular radar (AMPS and ARTS) as 

as conventional mobile radio base stations provide a b

for field experience in the techniques of protection. 

practices or recommendations described in this section 

flect the combined experience of three organizations 

volved in this technology: Bell Laboratories. Mobile R

Department of General Electric, and Motorola Commun

tions and Electronics. 

Actual damage experience has been limited to 

outage after a major lightning strike, but a single module 

placement by field personnel restored the normal opera

Automatic monitoring of the antenna performance has b

sufficient to detect minor antenna damage due to lightn

this type of degradation can then be corrected by rou

maintenance. 

This success story is the result of thorough applicatio

the principles discussed earlier. Inspection of a cell site 

veals a grounding scheme that includes extenslve ground

rods and well-bonded rings (called "halo" when installe

the top of the inside wall of the building, in contras

floor-level rings). Systematic bonding of conduits, cabin

and enclosures is mandatory. 

At a typical site, the power line protection starts at 

utility d~stribution transformer with a primary surge arre

The meter socket and service antenna panel are groun

to the local unit. Surge arresters are provided on the 

side of the service panel, protecting the rectifiers for the 

supply to the 24 V storage batteries. The limited 120 V 

loads (test instruments and fans) are supplied by an inve

fed from the battery. 

The cable input from the wireline plant is first protec

at the point of entry by conventional protectors. While 
some installations this has been the only protection, further 

-, protection is recommended by the use of three-electrode 

gas tubes, as a prudent and ultimately cost-effective backup 

protection. 

The major threat associated with lightning has been successfully overcome by extensive grounding and shielding. 

The tubular post construction for the antenna, rather than the 

lattice tower, offers a very effective method of shielding the 

antenna feed line. Lightning current flows on the outer shell 

of the post, leaving the coax cables unharmed inside. The 

extent of the outside grounding network (rods vs. mats or 

radials) can be determined by prudent practice, guided by 

cost-weighing factors involving the past history and practices of the general site area, and the water table condition 

of the site on a year-round basis. Both power companies 

and local telephone companies generally have 

well-developed experience in this area. 

Field experience has shown that problems arose when 

the antenna elements were not bonded to the overall ground 

("dc groundnas opposed to "RF ground") system. This bonding is done at the tower top, at intermediate tie points, and, 

most important, at the base of the tower and hatch plate 

entrance to the building. Some of the relatively small details 

in grounding practices, which can be described as 2% increments in protection costs, have been found to yield a 50% 

improvement in lightning withstand capability. 

When the precautions have been applied, operators and 

- manufacturers express confidence in the reliability. While 

none would be foolhardy to claim immunity, all have found 

that an effective protection can be achieved. 

Systematic application of protective techniques, including shielding, bonding, and grounding will allow diversion of 

lightning currents directly to earth, with a minimum amount 

of residual stress for the electronics. The residual stress can 

then be dealt with by suitable surge protective devices. 

CONCLUSIONS 

Electrical protection of cellular radio sites can be obtained by appropriate application of protective techniques 

and protective devices. The effectiveness of these has been 

demonstrated in trial systems of cellular radio as well as in 

their long-successful application in power systems, telephone wireline systems, and conventional mobile radio systems. 

Surge protective devices are available for protecting lowvoltage electronics. Two basic types offer different characteristics: crowbar devices have high-current capability but 

generally involve power-follow when applied on a power 

system; voltage clamping devices, either silicon avalanche 

or varistors, are free from the power-follow problem. 

Avalanche diodes offer low clamping voltage, which 

makes them most suitable for low-voltage, low-power electronics. Metal oxide varistors are now available in a wide 

range of clamping voltages and energy-handling capacities. - Spark gaps, while having some limitations, are wldely used 

on telephone circuits, mostly in the form of gas tubes. E

of these dev~ces has its own best field of application, in

ing greater reliability of the circuits in the electromagn

environment of power and communication systems. 

ACKNOWLEDGEMENTS 

The contribution of data and comments made by the 

lowing individuals and organizations are gratefully ackno

edged: W. Bryson, Phelps Dodge Communications C

pany; E.J. Cohen, Rural Electrification Administrat

F.A. Fisher and E.K. Guthrie, General Electric Compa

G. Fell, Motorola National Service; D. Horn, Motorola C

munications and Electronics; K.G. Nelson, AMPS of Illi

Bell; J. Nicholas, P.D. Speranza and T.K. Wingard, Bell T

phone Laboratories. 

REFERENCES 

1. IEEE Guide for Surge Voltages in Low-Voltage 

Power Circuits, IEEE Std 587- 1980. 

2. "Insulation Coordination Within Low-Voltage Systems 

cluding Clearances and Creepage Distances for Eq

ment," International Electrotechnical Commission Re

664, 1980. 

3. M. Goldstein and P.D. Speranza, "The Quality of 

Commercial Power," INTELEC Conference Proceedi

IEEE. 1982. 

4. Regulation, Section 68.302fe) Title 37; Telecomm

cations, Washington, D.C., U.S. Government Printing 

fice, 1977. 

5. Test Specifications for Gas Tube Surge Protective 

vices, IEEE Std C62.31-1982. 

6. Test Specifications for Low-Voltage Air Gap Su

Protective Devices. IEEE Std C62.32, 1981. 

7. Test Specifications for Varistor Surge Protective 

vices, IEEE Std C62.33, 1982. 

8. Test Specifications for Avalanche Junction Protec

Devices. IEEE Std C62.34, to be published in 1983. 

9. World Distribution of Thunderstorm Days, WMO-O

#21 TP6, World Meteorological Organization, Gen

1953. 

10. R.S. Valazquez, V. Gerez, D. Mukhedar, and Y. Gerv

"Probabilistic Calculations of Lightning Protection 

Tall Buildings," IEEE Transactions on Industry App

tions 1A-18 (3), MaylJune 1982, pp. 252-259. 

11. FA F~sher and D.W. Caverly, "Lightning Protection 

tems for Walt Disney World." General Electric Comp

Pittsfield. MA. 1969. 

12. J.F. Henz and E.W. Paul, "A Lightning Damage Ass

ment of the United States." US. Nuclear Regula

Commission, NUREGICR-2013. 1981. 

13. Recommended Guide for Measuring Ground Re

tance and Potential Gradients in the Earth, No

American Institute of Electrical Engineers, New Y

New York, May 1962. 
, 14. IEEE Recommended Practice for Electric Power Systems in Commercial Buildings, IEEE Std 241-1974. 

15. "Electrical Protection Grounding Fundamentals," REA 

Manual, Section 802, dune 1975. 

16. M.N. Smith, Practical Application and Effectiveness of 

Commercially Available Pulse Volage Transient 

Suppressors, Naval Civil Engineering Laboratory. Port 

Hueneme, CA, 1973. 

17. "Surge Voltage Protectors - Application Note and Suggested Applications," SERT. The Journal of the Society 

of Electronic and Radio Technicians 9 (41,pp. 85-91, 

April 1975. 

18. C.B. Barksdale, "New Gas Tube Protector Technique for 

Circuits," Telephony 171, pp. 21-28, 1970. 

19. A. Bazarian, "When Should You Use Gas-Discharge Protectors?" Electronic Design News, December 20, 

pp. 58-62. 1973. 

20. V.W. Vodicka, "Voltage Transients Tamed by Spark-Gap 

Arresters," Electronics 39, 1966, pp. 109-113. 

21. J.D. Harden. F.D. Martzioff, W.G. Morris, and F.B. Golden, 

"The GE-MOV Varistor - The Super Alpha Varistor," 

Electronics 45 (21). 1972. p. 91. 

22. G.D. Mahan, L.M. Levinson, and H.R. Philipp. "Theory of 

Conduction in ZnO Varistors." 7BCRD205, General Elec- 

- tric Company, Schenectady. NY, 1978. 

23. M. Matsuoka. T. Masa Yama, and Y. Lida, "Nonlinear 

Electrical Properties of Zinc Oxide Ceramics." Proc. of 

First Conf. Solid State Devices, Tokyo, 1969, J. Japan 

Soc. Appl. Phys. 39, 1970, Suppl., p. 94. 

24. M. Matsuoka, "Non-Ohmic Properties of Zinc Oxide 

Ceramics," Jap. J. Appl. Phys. 10, 1971, p. 736. 

25. S. Korn, "Transients and Transient Suppressors For 

Power Conversion Equipment," INTELEC Conference, 

Washington, D.C., 1982. 

26. O.M. Clark, and J.J. Pizzicaroli, "Effect of Lead Wire 

Lengths on Protector Clamping Voltages." Federal Aviation Administration-Florida Institute of Technology 

Workshop on Grounding and Lightning Technology, 

FAA-RD-79-6, March 6-8, 1979, Melbourne, Florida, US. 

Dept. of Transportation, Washington, DC 20590. 

27. "Data Book," General Semiconductor Industries, Tempe, 

AZ. 

28. Transient Voltage Suppression Manual, Third Edition, 

General Electric Company, Auburn, NY, 1982. 

29. D. Bodle. "Electrical Protection Gu~de for Land-Based 

Radio Facilities," Joslyn Electronic Systems. 1971. 

30. F.D. Martzloff, "Coordination of Surge Protectors in LowVoltage AC Power Circuits," IEEE PAS-99(1), Jan-Feb 

1980, pp. 129-133. 

FOR FURTHER READING 

Lightning 

H. Cavendish, W. Watson. B. Franklin, and J. Robertson, "

port of the Committee Appointed by the Royal Society 

Consider a Method of Securing the Powder Magazines 

Purfleet," Philosophical Transactions of the Royal Soci

London, 63, 1773, and 68, 1777. 

Golde, R.H., ed., Lightning, 2 vols., Academic Press, Lon

and New York, 1977. 

N. C~anos and E.T. P~erce. A Ground Lightning Environm

for Engineering Usage. Stanford Research Institute, Tec

cal Report, August 1972. 

M.A. Uman, Understanding Lightning, Bek Technical Pu

cations. Carnegia, PA 15106, 1971. 

E.W. Boehne, and R.H. Golde, eds., "Research on the Lig

ning Phenomenon," Journal of the Franklin Institute 2

(6), June 1967, pp. 451-478. 

Surge Occurence and Propagation 

F.D. Martzloff and G.J. Hahn, "Surge Voltage in Residen

and industrial Power Circuits," IEEE PAS 89(6),JuiylAug

1970, pp. 1049-1056. 

R. Hasler and R. Lagadec, "Digital Measurement of F

Transients on Power Supply Lines," Proc. 3rd Sympos

and Technical Exhibition on Electro-Magnetic Compati

ty, Rotterdam, Holland, May 1979, pp. 445-448. 

A. Greenwood, "Electrical Transients in Power System

Wiley Interscience. New York. 1971. 

F.D. Martzloff, "The Propagation and Attenuation of Su

Voltages and Surge Currents In Low-Voltage AC Circ

IEEE PAS-102(5). May 1983, pp. 1163-1170. 

Surge Suppression 

"The Protection of Telecommunication Lines and Equipm

Against Lightning Discharges," Comite Consultatif Inte

tional de TkIBgraphe et Telephone, International Teleco

munication Union, Geneva, Switzerland, 1974. 

Cellular Radio 

"Advanced Mobile Phone Service." The Bell System Tec

cal Journal 58 (1). January 1979. 

F.H. Blecher, "Advanced Mobile Phone Service," IEEE T

sactions on Vehicular Technology VT-29 (21, May 1980, 

238-244