Prepared by 

National Rural Electric 

Cooperative Association 

Cooperative Research Network 

4301 Wilson Boulevard 

Arlington, Virginia 22203-1 860 

and 

Fran~ois D. Martzloff 

National Institute of Standards and 

Technology 

100 Bureau Drive 

Gaithersburg, Maryland 20899 

C&N@ 

COOPERATIVE RESEARCH NETWORK 
The National rural Electric Cooperative Association (NRECA) is the national service organization of more than 900 rural electric 

systems. These cooperatively owned utilities own and operate about 44% of the miles of distribution lines in the nation to provide power to less than 10% of the nation's people, primarily in the sparsely populated, rural areas of 46 states. 

NRECA was founded in 1942 to unite rural electric systems in a way that would permit them to develop the servlces and 

support needed to properly serve rural America. NRECA is on of the largest, rural-oriented cooperative organizations in the 

United States. 

The Cooperative Research Network, a service of NRECA that was used to support this project, was created to conduct studies 

and carry out research of special interest to rural electric systems and thelr consumers. 
Contents - v 

Section 1 

Section 2 

Disturbances and Remedies 

Introduction 

The Nature of Disturbances 

Too Much Voltage 

Not Enough Voltage 

Other Power-Line Disturbances 

System Interactions 

Questions to Ask 

Customer-Owned Offenders 

How to Use the Worksheets 

Identifying Residential and Commercial Appliance Categories 

Worksheet EDE: Electronic, dual, external 

Worksheet EDI: Electronic, dual, internal 

Worksheet ES: Electronic, simple 

Worksheet HE: Heat, electron~c 

Worksheet HM: Heat, mechanical 

Worksheet ME: Motor, electronic 

Worksheet MM: Motor, mechanical 

Worksheet PLC: Power line conditioning 
vi - Illustrations 

ILLUSTRATIONS 

FIGURE PAGE 

1.1 Sine wave of an AC voltage supply. 2 

1.2 A surge induced by lightning on an AC voltage. 3 

1.3. Typical voltage on a distribution bus during capacitor bank energizing. 4 

1.4: Example of a customer's bus voltage during utility capacitor switching. 5 

1.5 A lamp and a rabbit-ear TV are examples of single-port appliances. 6 

A computer with a telephone modem connection is an example 

of a two-port appliance. An ordinary house offers many examples 

of both single-port and multiple-port appliances. 

1.6 A typical WSS with power and telephone protection. 7 

1.7 A meter-base arrester installed by the utility. 7 

1.8 Relative energy deposited in the suppressor by a typical high-energy 9 

surge for various combinations of 250-volt (H), 150-volt (M), and 

130-volt (L) ratings, as a function of separation distance. 

Division of surge current in a cascade of two 150-volt devices: I, 

is the current in a 40-rnm-diameter arrester and I, is the current in 

a 20-mm-diameter suppressor, with 10-meter separation for the 

same 3000-ampere surge as in Figure 1.8. 

1.10 A voltage swell lasting eight cycles. 10 

1.11 Unequal line voltages caused by an open neutral. 11 

1.12 A very brief outage (top) and a very long outage (bottom). 13 

1.13 A sag lasting 10 cycles with the line voltage reduced to 55% of normal. 13 

1.14 The original CBEMA curve (top) and the updated ITIC curve (bottom). 15 

1-15 Noise superimposed on an AC voltage. 16 
Illustrations - vii 

FIGURE PAGE 

- - -- . - -. 

1.16 An AC voltage distorted by harmonics. 16 

1.17 Commutation notches on an AC voltage. 17 

Power and telephone services enter the house at opposite ends. 

A personal computer is connected across the two systems. 

Voltage and current recorded with telephone and power services 19 

entering at opposite ends of the house. 

1.20 Mitigation obtained by inserting a surge reference equalizer in 

both the power line and the telephone line. 

1.21 Shifting reference potential can be remedied by inserting a surge 2 1 

reference equalizer on the communications and power lines (here, 

the appliance is a TV and the communications line 1s a TV cable, 

but a PC with a telephone modem connection presents the same 

problem). In the ideal situation, the commun~cations and power lines 

enter the house on the same side, and the SRE is most effective. 
viii - Tables 

TABLE PAGE 

2.1 Home-Based Disturbances, Causes, and Remedies 23 

- 

2.2 Categories of Equipment Victims 2 5 
Forward - ix 

FOREWORD 

Customer service representatives have a tough 

task when they have to respond to calls from 

consumers who are having problems with an 

appliance. "My television won't work. What's 

wrong?" "My computer lost its memory. What 

did the co-op do to cause this?" Complaints may 

be couched in vague terms, and the caller may 

tend to blame the electric cooperative. 

This manual was commissioned by the 

Cooperative Research Network to address these 

kinds of complaints. Written with the help of 

an expert in household and small-business electricity problems, it provides a series of worksheets that guide representatives through a 

question-and-answer session with a caller, leading the caller from the general to the specific 

with the goal of finding the exact source of the 

problem (which often is not attributable to the 

cooperative). 

Senrice representatives can use the worksheets in conjunction with the manual's simple 

explanations of the nature of disturbances and 

how to prevent or cure their effects to diagnose 

specific problems. On the basis of the diagnosis, 

the representative can tell the consumer what to 

do or can call in the cooperative's repair service 

to handle the problem. If the cause of a particular problem proves elusive, the representative 

can refer ir to a specialist. 

The manual should help representatives work 

more effectively and efficiently. It should help 

cooperatives avoid unnecessary service calls. And 

it should help consumers get quick solutions to 

their problems, whether utility-related or not. 

Martin E. Gordon, PE. 

Senior Program Manager 

Cooperative Research ivetwork 
Executive Surnrnarv - xi 

EXECUTIVE SUMMARY 

When an electricity consllmer has a problem 

with an appliance-a light bulb that flickers, a 

television that "burns out," a motor that overheats, for example-a natural tendency is to 

complain to the electric utility. In actuality. 

many such problems are not the fault of the 

electric utility, and indeed may be beyond the 

control of the electric utility. 

How does an electric cooperative, with limited customer-service resources, handle such 

complaints? How can it efficiently separate problems that it can fix from [hose that are beyond 

its control, and perhaps recommend cures or 

preventive measures to consumers for the latter 

problems? This manual suggests a way: It provides worksheets for customer service representatives to guide them through a dialogue with a 

customer calling for help. By following the guidance, a representative can ask the right questions, get at the root of a problem, and then 

decide on an appropriate action: send a repair 

crew, tell the customer how to fix the problem, 

or, for a problem that resists immediate solution, 

call in an expert in the field. 

The manual is organized in two parts: 

Part 1 reviews the nature of disturbances 

that can occur in the power supply to customers--disturbances such as voltage surges, 

lightning strokes, voltage swells, outages, 

brownouts, voltage sags, noise, harmonics, 

unbalanced phases, and interaction between 

the power system and a telephone or cable 

TV system. A customer service representative 

can learn in this part how the disturbances 

originate, how they affect electrical equipment, and what can be done about them. 

Part 2 helps the customer service representative troubleshoot over the telephone. It 

contains worksheets, eight in all, covering the 

major categories of equipment-heaters, 

motors, and electronics of various types. Each 

worksheet is a blueprint for a question-andanswer session with a customer, designed 

to arrive at the cause of the customer's problem and a possible cure. By applying the simple theory in Part 1 and following the stepby-step instructions, the representative should 

be able to diagnose many problems and 

decide whether intervention by the cooperative is warranted. 

The manual stresses a crucial fact: that problems with equipment connected to both an electric power system and a communication system-televisions with cable connections or personal computers with modem hookups, for 

example-can be caused by ezther system. Such 

problems are compounded when the two services enter at opposite ends of the building; 

physical separation of the entry point magnifies 

the disturbances. Such disturbances should 

never be blindly attributed to "power line 

surges"; often the communication link can be at 

fault, especially when it is improperly installed, 

as sometimes happens with cable connections. 

Scattered throughout Part 1 are short case histories drawn from ordinary experiences-a 

chandelier that inexplicably flickers, motor controllers that shut down when the electric utility 

adjusts its power factor. With such experiences 

and simple electrical theory as background, customer service representatives should be able to 

analyze many of the problems posed by disturbances and find a solution for the consumer, or 

know when to call in expert help. 
Disturbances and Rerned~es - 1 

Disturbances and Remedies 

In Thls Section: Introduction; the nature of disturbances; too much voltage; not enough voltage; 

other power-line disturbances; system interactions 

lnlroductlon Many people believe that upsets or damage to 

electrical equipment can be blamed on disturbances caused by the power distribution system 

or by lightning. However, such a belief is an 

incorrect generalization; many times the problem 

is in the equipment itself, not the power system. 

This manual can help cooperatives' customer 

service representatives distinguish between 

equipment-related and system-related problems, 

and either suggest a solution the customer or 

alert the dispatcher that the cooperative's assistance is needed. The manual presents in simple 

terms the principles underlying unwanted upsets 

and damage and offers remedies for them. 

This first part of the manual gives an 

overview of the disturbances that can occur in 

the power supply to the customer. It briefly 

describes the origins of the disturbances and 

explains which disturbances are avoidable, 

which are unavoidable, whch are predictable, 

and which are entirely random occurrences. The 

first part is organized in four sections. The first 

two are concerned with the most frequent but 

brief disturbances-too much or not enough 

voltage (energy). The third section addresses 

less frequent disturbances that are almost permanent, such as noise, harmonics, notches, and 

voltage unbalance. The fourth and last section 

describes the possible interaction between the 

power system and a communications system, 

which is believed to be the cause of many Failures that are often misinterpreted as caused by a 

"power line surge." 

The second part of the manual is formatted as 

a collection of worksheets that suggest interactions between the customer service representative and the customer reporting a problem. 

An important fact is that upset or damage to 

equipment that involves a communications system can also be caused by disturbances on the 

communications system and should not blindly 

be attributed to "power line surges." Ways to 

prevent this kind of upset or damage do exist, 

but some are beyond the control of the customer and the distributing utility. It is a matter o

recognizing the situation and selecting a technically correct and cost-effective remedy. There 

may be cases where the risk or consequences of 

such damage or upset might be low, compared 

to the cost of prevention. Therefore, the choice 

of protecting or not protecting should be made 

thoughthlly, not left to neglect or ignorance. 

Armed with thls knowledge, customer service 

representatives as well as customers will be 

guided toward a satisfactory resolution. 
2 - Sect~on One 

The Nature of Electric power is delivered to custonlers in the 

form of an alternating-current (AC) voltage that 

the utility strives to keep as constant as possible 

(Figure 1.1). However, disturbances can and will 

occur in this voltage, in the form of either too 

much or not enough. In turn, the energy consumed by the load-what the utility sells-is 

related to the voltage at which it is delivered. 

The AC voltage follows a sinusoidal pattern, 

with a complete cycle occurring 60 times per 

second-engineers call that a 60-hertz (Hz) AC 

voltage. This smooth waveform can be distorted 

under steady-state conditions, or have a translent overvoltage or undervoltage. 

Some disturbances are brief-from millionths 

of a second (microseconds) to thousandths of a 

second (milliseconds). Other disturbances can 

be long, lasting from seconds to hours in the 

worst cases of service interruption. 

FIGURE 1.1: Sine wave of an AC voltage supply. 

Too Much Too much voltage can be the result of a normal 

Voltage or abnormal utility operation, or the effect of an 

external influence. Under normal operating conditions, the steady-state voltage is controlled by 

the utility withm a narrow band. Deviations from 

this band are rare, and the utility can readily 

correct them, if informed of their occurrence, by 

acting on voltage regulators and tap changers. 

On the other hand, there are momentary 

(transient) disturbances that occur under the 

typical operating conditions of a power system. 

There are two types of transient excessive voltage that can occur under normal circumstances, 

although by themselves they would be described 

as "abnormal": 

1. A surge is an overvoltage that can reach 

thousands of volts, lasting less than one 

cycle of the power frequency, that is, less 

than 16 milliseconds. 

2. A swell is longer, up to a few seconds, but 

does not exceed about twice the normal 

line voltage. 

A third type of excessive voltage, a temporary 

oven/oltage, is not a part of normal operation, 

but is associated with a fault in the power system. Temporary overvoltages can last a much 

longer time, and generally do not disappear 

until the fault is cleared. 

SURGES 

Types and Origins of Surges 

Surges have been blamed as the cause of equipment upsets or damage under many names: 

power surges, spikes, glitches, impulses, and so 

forth. In this report, the term surge is used, with 

the understanding that it means events lasting 

less than one cycle of the power frequency. 

The two major causes of surges are 

Lightninean obvious and well recognized 

event (Figure 1.2) 

Load switchinea type of event that includes 

major power system operations as well as 

simple and seemingly benign switching by 

the customer 
Disturbances and Remedies - 3 

Next to outages, surges are the 

type of disturbance most frequently perceived by customers 

as the source of [heir problems, 

and therefore merit a detailed 

examination. 

Lightning Surges. There are four 

types of lightning surges, 

described here in order of severiFIGURE 1.2: A surge induced by ty. The first, rare but traumatic, is 

lightning on an AC voltage. a direct lightning stroke to the 

building. Unless special protection systems have been provided 

(lightning rods in plain language, air term~nals in 

protection jargon) with proper down-conductors 

and grounding, damage to the structure and 

equipment can be substantial. Of course, such 

an event cannot be blamed on the utility. Few 

residential customers go to the expense of 

installing a lightning protection system. Instead, 

they make an intuitive risk analysis: A typical 

lightning protection system can cost thousands 

of dollars, while the probability of a direct 

stroke (outside of known areas of high lightning 

activity) is about once every 200 years for a 

detached home. 

The second type of lightning surge occurs 

when a nearby stroke, and the resulting flow of 

current in the earth, elevates the potential of the 

ground references of the building, including the 

power system neutral that is bonded to ground 

at the service entrance. This situation is called 

ground potential rise. Meanwhile, the power 

supply phase conductors, which are referred to 

ground through the secondary winding of the 

distant distribution transformer (whose neutral is 

grounded there) remain essentially at the 

ground potential of that distant transformer. A 

large difference of potential can then occur 

between the neutral and the phase conductors 

at the service entrance of the building. That difference of potential appears to be a surge delivered by the utility connection, but has nothing 

to do with the utility operations. 

The third type of lightning surge is produced 

by the radiation of electromagnetic fields associated with a lightning strike at some distance 

from the building. Such a surge involves low 

energy but can still produce upsets and even 

damage in sensitive electronic circuits. The 

severity of these surges depends mostly on distance. Nearby strikes are rare but may have 

severe effects, distant strikes are more frequent 

(increasing with the area of collection, that is, 

with the square of the distance) but less severe. 

Again, these surges cannot be blamed on the 

utility, but some customers might believe that 

they came from the utility connection and 

attempt to place the responsibility on the utility. 

The fourth and last type of lightning surge is 

one that actually arrives on the service drop of 

the utility, as a result of a direct stroke to some 

element of the distribution system. A surge 

induced in the utility distribution circuits by a 

nearby stroke, just like the third type discussed 

above, can also appear at the service entrance. In 

contrast to the first three types, this fourth type is 

truly an excessive voltage delivered by the utility 

to customers. However, the general practice 

among utilities is to provide surge arresters on 

their systems, so that the residual surge that can 

appear at a customer's service entrance is somewhat limited. The rare exception would be a 

direct stroke to the pole or service drop, where 

the utility surge arrester would not intervene 

before a surge heads for the service entrance. 

Switching Surges. There are two types of 

switching surges: 

Those that result from normal switching of a 

load on or off by a customer or the utility 

Those that are incidental to an intended operation aimed at clearing a fault-a short circuit 

or severe overload. 

Switching Surgesfrom Normal Operations. 

The first type of switching surge ("normal" 

surge) occurs whenever a load-any type of 

load-is being switched, either within the distribution system or with the customer's installation

Therefore, these can occur quite frequently. 

Those associated with the switching of a local 

load, especially if it is an inductive load such as 

a motor, are generally short (a few microseconds) and do not involve a large amount of 

energy. However, there is another source of 
4 - Section One 

potentially large switching surges when capacitor banks are switched for power-factor correction. These can occur at random if the powerfactor correction bank is controlled by the 

instantaneous state of the system, or they can 

occur at fiied times in the day if the capacitor 

Capacitor Switching Surges 

Capacitor banks have long been accepted as a 

necessary part of efficient electric power systens. Switching capacitor banks on and off is 

generally considered a norm1 operation for 3 

utility system, and the transients associated 

with switching are generally not a problem for 

utility equipment. The low-frequency transients, 

however! can be magnified in a customer's 

facility (if the customer has !ow-voltage 

power-factor correction capacitors) or result in 

the nuisance tripping of power-electronic 

devices such as adjustable-speed drives. 

Actually. capacitor energizing is just one of the 

many switching events that can cause transients 

on a utility system, but? because of their regularity and impact on power system equipment. 

they quite oFten receive special attention. 

There are a number of transient-related concerns that are genemlly evaluated when distribution shunt capacitor banks 

are applied to a power system. 

However, these considerations 

are related to the system design 

rather than its operation, and 

the customer has no control 

over them. Remedies will essentially be to learn how to live 

with these unavoidable transients. When they originate from 

the switching of a large capacitor bank, it is unrealistic to 

expect that the typical surge 

suppressor has the energy-handing capability to absorb them. 

Characteristics of Energizing 

an Isolated Capacitor Bank. 

Energizing a capacitor bank 

results in an inunediate drop in 

system voltage toward zero. 

bank is switched on and off by a timer. 

Capacitor switching surges from the utility have 

been found troublesome in installations where 

the customer also has some power-factor correction capacitors: Magnification of the surges can 

occur. (See box, "Capacitor Switching Surges.") 

followed by an oscillating transient voltage 

superimposed on the fundamental power frequency waveform. The peak voltage magnitude 

depends on the instantaneous system voltage 

at the instant of energization, and can rise to 2 

times the normal system voltage under worstcase conditions. 

Ordinarily, though, other components of the 

system help to keep the voltage rise to 1.2 to 

1.8 times the normal value, and the transient 

oscillates at frequencies from 300 to 1,000,000 

Hz. Figure 1.3 shows an example. recorded in 

the field, of a transient created by energizing a 

capacitor bank. 

Tsdnsient overvoItages caused by capacitor 

switching are generally not a problem for utilities because their peak magnitudes are usually 

just below the level at which surge protective 

devices (SPDs) begin to operate. However, 

these transients will often be coupled through 

-1.5 ' I I I I I I 

0 10 20 30 40 50 60 70 

Time (milliseconds) - 

I RE 1.3: ~ypicxoltage on a distribution bus during 

capacitor bank energizing. 
Disturbances and Remedies - 5 

step-don-n tr.insfonners to cu,~xner loails The 5ize of the utilit! 's 5n-itched capacitor 

(Figuse I.+). \vhere they can ~1ifec.t poner- Ixunk is more thnn 10 times larger than tl~e 

quality-sensitive custonler ecluipment. i~rch c~~strxncr's customer haik. 

:IS cumputers. The frequrnc! of the energizing oscillation 

If the customer uses c:ipacitors for the cor- is close to the resonant freq~~enc!- of the 

rection of pon-er factor nn lhe lov-voltage circuit fol-med hk- the step-clorvn transside, higher transient or-ervoltages can rise former and the customer's porver-hctor 

e\ en higher. This effect-"\ oltagr inagnifica- correction capacitor Ixlnk. 

tion"+xcurs when a tmnsient oscillation. ini- The customer's load has relatively little 

tiated by the energization of a urilih cqxacitor resistance (this is t).pical of industrial p1:ltvs 

bank, excites a resonmt circuit in the low %-here motors represent the major part of 

voltage system (the circuit is a combination of the load). 

the inductance of the step-donn transformer 

and the capacitance of the customer's power- Orclinarily. these transient switching or-en.oltfactor correction bnnk). The result is a higher ages might simply clamage low-enern surgeoven-oltage at the lon-er voltage bus. The protective devices or cause a nuisance trip of 

worst ~nagnification occurs wl~en the follon-ing power-electronic equipment. Nevertheless. 

conditions exist: mcidents have been reported of complete 

failure of end-user equipment. 

I 

I 5 10 15 20 25 30 35 40 45 50 

Time (milliseconds) 

FIGURE 1.4: Example of a customer's bus voltage during utility capacitor switching. 

Switching Surges from Fault-Clearing. The sec- voltage, and their duration ranges from hunond type of switching surge, far less frequent, dreds of microseconds to a few milliseconds. 

occurs when a system fault is cleared, either by 

the opening of a circuit breaker or the operation Effect of Surges on Equipment 

of a fuse. The latter can generate high surges if Upset versus Damage. Surges impinging on 

the fuse is located at the end of a long cable, in equipment can cause upsets or permanent 

which the fault current can store substantial damage, with consequences ranging from barely 

energy in the cable inductance. noticeable to total destruction or consequential 

The magnitude of these fault-clearing surges damage. 

can reach several times the normal system Among upsets, there are several possibilities: 
6 - Section One 

Barely noticeable, with self-recovery: a click 

in a sound system or a flash on a video screen 

Pern~anent and noticeable, requiring manual 

reset: blinking clocks and VCRs 

Permanent but not readily noticeable: 

data corruption 

There are also several kinds of damage: 

Damaged components, repairable at a 

service shop 

Damaged components that are too costly 

to repair 

Obvious and irreparable damage requiring 

complete replacement of the equipment 

Damage such as internal equipment fire that 

could set other objects afire 

Insurance statistics provide information on the 

relative frequency of damage among insured 

appliances. It is significant that video equipment 

is at the top of the list, and the discussion of 

multiple-port equipment damage under "System 

Interactions" at the end of Part 1 will explain 

why. A potit is a connection between a piece of 

equipment and the outside world. The line cord 

of an appliance is a powerpolst. The modular 

telephone jack on a fax machine, or the UHF 

connector at the back of a W set is a communicationsport. In the modern home, both one-port 

and multiple-porc appliances abound (Figure 1.51, 

and the same situation exists in commercial and 

industrial installations. When the rime comes to 

understand the origin of the surge suspected to 

FIGURE 1.5: A lamp and a rabbi-ear N are examples of single-port 

appliances. A computer with a telephone modem connection is an example 

offers many examples of both 

have causecl damage to an appliance, it is 

imposcant to determine if the appl~ance 1s a single-port or a multiple-post type. 

Many appliances are still single-port equipment, in spite of the trend to provicle sophisticated controls: a simple kitchen range is a 

single-port appliance, but a range controlled by 

a smart-house computer system is a two-port 

appliance. A TV set with rabbit-ear antenna is a 

single-port appliance, but the same set with a 

roof antenna or cable TV connection becomes a 

two-port appliance. 

Multiple-Port Equipment. More and more electronic equipment in homes and businesses 

requires a communications link, hence a communications port in addition to the usual power 

supply connection, the power port. Examples of 

such two-port appliances include fax machines, 

telephone answering machines, personal computers with modem or printer connections, and 

cable-connected TV receivers and VCRs. 

A possible problem is tknt although each of 

the power and communications systems may 

include a scheme for protection against surges, 

the surge current flowing in the surged system 

causes a shift in the voltage of its reference 

point while the other, nonsurged, system reference point remains unchanged. The difference 

of voltage between the two reference points 

appears across the two ports. Depending on the 

nature OF the appliance and its immunity, this 

difference of voltage may have some upsetting 

or damaging consequences. The problem is so 

important that it is discussed in more detail in 

"System Interactions" at the end of Part 1. 

Remedies against Surges 

General Approach. At first glance, ~t would 

seem that if surges could be prevented from 

happening, many problems could be prevented. 

However, lightning cannot be eliminated. (There 

are some yet unproved schemes to dissipate the 

charges in a cloud and thus prevent lightning 

strokes.) Similarly, switching surges that occur in 

the utility system cannot be eliminated by the 

time they arrive at a customer's service entrance. 

Therefore, the general remedy is to install 

(insert) surge-protective devices at one or more 

points of a customer's installation. 
Disturbances and Remedies - 7 

Surge-Protective Devices: What's in a Name? 

The devices that can protect against surges are 

called surge-protectiue cleuices, or SPDs, by engineers, but that might sound too much like jargon to most customers. The name that seems to 

stick in the general public is surge suppressot: 

which many manufacturers use for their trade 

designation, with a variety of catchy trademarked names The Underwriters Laboratories 

chose to call them transient uoltage sulge suppressors (TVSSs), and that name or acronym 

generally appears next to the UL sign on the 

product. In the utility industry, the generic name 

used in the transmission and distribution parts of 

the system is surge arrester: 

Actually a surge cannot be suppressed nor 

arrested; the correct word to describe what happens is diverted. What these protective devices 

do 1s simply divert a surge to ground, where it 

can do no harm. So a name that makes sense 

would be surge divertel*, but it was not picked 

The consumer industry has settled on TVSS, 

while the utilities stay with the long-used word 

awester and use it for the more rugged devices 

that a utility installs a1 the service entrance. 

The surge protection schemes for residential 

customers are these: 

Insert a TVSS for each sensitive appliance 

(Figure 1.6) 

Accept the offer (if made) fl-onl the utility to 

provide "whole-house protection" (Figure 1.7) 

Wholehouse protection consists of a protective device at the service entrance complemented by TVSSs for sensitive appliances within the 

house. The service entrance protection is an 

adapter inserted by the utility between the revenue meter and its base. Variations exist, such as 

a separate box connected to the meter base box

With whole-house protection-that is, an 

arrester at the service entrance and one or more 

TVSSs inside the building-the issue of .'cascade 

coordination" arises. The concern is that, if the 

various protective devices are not selected with 

due consideration, he stress of incoming surges 

may not be shared according to the capability of 

each device. (See box, "Cascade Coordination.") 

This is a concept that the residential customer 

should not be expected to assess; it 1s the utility's responsibility to consider it and offer an 

integrated, coordinated package of service 

entrance protection and TVSSs. 

FIGURE 1.6: A typical NSS with power and 

telephone protection. FIGURE 1.7: A meter-base arrester installed by the utility. 
8 - Sectton One 

Cascade Coordination 

cisc:~ding s~lrge-protectiw cle\-ice is :I concept n.herehy two (or n~ose) protectix e &\-ices 

are connectecl :I[ tn-o (or 1nore1 different 

points of a pon-er sytem. The "upstrran~" 

device (the one closest to he utility's distribution system) is the first line of defene: it is 

designed to divert the IILIII< of an impinging 

surge. The "don-nstrealn" cle\.ices (those closest to the equipment to be protected) are 

intended 2s a final stage. cli\wting any remaining surges, including those generateil within 

the customer's wiring. 

Successful coordination of cascaded cle\.ices 

is achieved when the hea\-v-du~- upstream 

device does indeed divert the bulk of the 

surge. instead of letting the don-nstream 

devices attempt to divert an excessive amo~int 

of the surge current. In keeping n-it11 the terminology of this manual. the ~ipstseam cie7-ice 

n-ill be referred to as an armrer, while the 

lighter duv. don-nstream devices n-ill be 

referred to as s~lpprrssors. The basic and critiCJI parameters for successful coordination of 

the arrester suppressor cascade include the 

relative voltage clamping of the devices, their 

electrical separation through n-iring inductance. and the actual waveform of the impinging surge 

A w-ell-designed cascade arrangement maximizes the benefit of surge protection n-ith a 

minimum expenditure of hard%-are. Another 

benefit of a cascade is the diversion of large 

surge currents at the service entrmce. so that 

they do not flow in the building, and side 

effects are thus avoided. 

It is one thing to design a cascade based on 

optimurn coordination where all the parameters are under the control of the designer. 

Such an opportunity exists in utiliy systems 

implemented under centralized engineering. It 

is an altogether different challenge to attempt, 

after the fact, coordinating the operation of 

surge-protective devices connected to the 

power system by diverse and uncoordinated 

(and uninformed) users. 

Promoting a coordinated approach may 

come too late for the de facto sitiration in 

which millions of suppressors are in se~~ice 

n-ith a relati\dy lo\\. clampin3 voltage. This 

situarion will impose an upper limit to the 

clamping voltqe of a candidate retrofitted 

arrester. Therefore. close attention must Ix 

paid to the selection of the relative clamping 

\-oltage of the devices. in \-ien- of the contlicting requirenlents for performance undrr surge 

conditions-a successful cascade-and reliabl? 

n.ithstanding temporary power-frequency 

oven.olrnges. Nevertheless. coordination still 

IIYJ!- he possible if die arailable t~~cleoffs are 

understood. In the filrure. m-ell-informed users 

coulcl avoid the pitfalls of poor coordination 

01. the disappointment of implenlenting protection schemes that cannot pro\-ide the hopedfor results. 

.%I illusrmtion of [he effect of the relative 

volrages and device separation on the enerR 

sharing bern;een two devices appears in 

Figlire 1.8. The fig~lre shows 3 plot of the percentage of the total energy dissipated in the 

suppressor, as a function of the distance separxing the nvo devices. for \-arious cornbi~~ations of clamping voltages. In the plot. H. h1. 

and L correspond respectively to a high (250 

V). medium (150 V). and Ion- (130 V) voltage 

rating, in a 120-V rms circuit application. In 

the designations H-H. H-M. H-L. etc., the first 

letter is the rating of the arrester and the second letter is the rating of the suppressor. 

Figure 1.9 shows an example of a coordimted scheme where the current in the suppressor is indeed small compared to the current in the arrester. This encouraging result 

can sen.e as the basis for the selection of the 

two devices in a schenle that a utility can offer 

to its customers as an integrated package. 

The active element in most surge protective 

devices is one or several disks of metal oxide 

varistor (MOV) that perforn~ the current diversion function. The surge diversion capability of 

arresters and suppressors increases with their 

diameter. A typical cascade might consist of a 

40-millimeter-diameter arrester and a 20-millinieter-diameter suppressor, described as a 

40-mn1/20-mm cascade. 
Disturbances and Remedies - 9 

Distance between arrester 

and suppressor (meters) 

FIGURE 1.8: Relative energy deposited in the suppressor 

by a typical high-energy surge for various combinations 

of 250-volt (H), 150-volt (M), and 130-volt (1) ratings, as 

a function of separation distance. 

.-\itlios~~ii he rcnlit! of Ixl\ ing nun) 

millions or 130-\ ok suppressors 

in~tdlcil on 12o-\-olt systelns makes ;I 

\T ell-coorilinatetl casc:tde difficdt or 

puhaps ~un;~itninalAc. atleast in the 

nr;u future. n cooperative can still 

take cemin steps lo i~npro\.e coorclination in a protection sr-stem. .is a 

compromise. :I cascade n ~th equ:il 

\ oltage ntings 6s the arrester and the 

suppressor can offer successfi~l coorclinution. if the impinging ssurges :Ire 

rel:~ti\.ely short. The coordination of :I 

simple cascade of an arrester and :I 

suppxsor of equal voltage rating. 

hoth connected line-to-neutral. 1s 

slightly improwd b!- the larger diameter of the arrester. Mon-el-er. an unfdvoralAe ccimhinxtion of rt~lerances for 

the two devices can wipe out the 

impro\.ement-for example, if the 

arresrer clamping voltage is at the 

upper end of the tolennce band and 

the suppressor is at the Ion-er end of 

the tolerance band. effecti\.ely making 

the suppressor tl~r lower device 

hence the one that mill have to divest 

Inoa of the surge. 

-1 000 

0 10 20 30 40 50 60 70 80 90 100 

Time (microseconds) - - 

FIGURE 1.9: Division of surge current in a cascade of two 150-volt devices: I, is the current 

in a 40-mm-diameter arrester and I, is the current in a 20-mm-diameter suppressor, with 

10-meter separation for the same 3000-ampere surge as in Figure 1.8. 
10 - Section One 

In large business or industrial installations 

with internal feeders, suhpanels, and fairly long 

branch circuits, the question of cascade coorciination is more complex than for a simple residence. It should be assessed by the specialist 

responsible for the electrical installation. 

SWELLS 

Origins of Swells 

The disturbance called a swell is a brief increase 

in the line voltage, typically less than 20 or 30%, 

associated with load rejections and sluggish 

voltage regulation response. The AC voltage 

sine wave remains essentially undistorted, but ~ts 

amplitude is increased for a few cycles or a few 

seconds (Figure 1.10). 

FIGURE 1.10: A voltage swell lasting eight cycies. I 

Effect of Swells on Equipment 

Swells lasting only a few cycles are unlikely to 

cause any damage, and only the most sensitive 

electronic equipment might experience a 

momentary disturbance. On the other hand, 

swells lasting more than a few cycles can cause 

a trip-out of protective circuitry in some powerelectronic systems. Variable-frequency drives 

(also called adjustable-speed drives) often 

include an overvoltage sensor in their electronic 

control, which can cause a trip of the system, 

with or without restart. The safety issue of automatic restart versus mandated manual-only 

restart is well known among plant engineers. 

Remedies against Swells 

For the residential consumer, there is no concern about damage and only a small likelihood 

of some upset of an electronic appliance. A user 

of variable-speed drives (these are beginning to 

appear in residenrial heating and air-conditioning systems) might experience a trip-out during 

a swell. That possibility raises the question of 

ability to withstand swells, to be taken up with 

the vendor of the variable-speed drive. 

There is no device that can suppress a swell 

the way a suppressor "suppresses" a surge; the 

remedy must be inherent immunity of the 

equipment. Thus, there is little that the userresidential or industrial-can do short of 

requesting the vendor to provide appropriate 

designs for the equipment. 

TEMPORARY OVERVOLTAGES 

Types and Origins of Temporary Overvoltages 

Temporary overvoltages are abnormal disturbances, at the power frequency, that occur 

under the usual (normal or abnormal) operating 

conditions of a distribution system. The principal causes are system faults over which the utility has little or no control (animals, storms, vehicle collisions) and a troublesome situation of a 

lost (open) neutral connection in the service 

drop to customers, in particular the residential 

120/240-V three-wire systems. 

Distribution System Faults. Overvoltages on the 

distribution system originate from a variety of 

system faults such as line-to-ground insulation 

failure within the distribution transformer. 

Overvoltages caused by system faults can reach 

2.5 times the normal voltage. Depending on the 

settings of the protective schemes, it can take as 

long as 5 seconds to clear the circuits. 

A rare but possible system fault occurs when 

the same pole carries two systems at different 

voltages and a collision, high wind, or ice causes 

one set OF conductors to fall onto the other. This 

scenario will produce overvoltages proportional 

to the difference of the two system voltages. 

Open Neutral. An open neutral situation can 

occur as a result of corrosion in underground 

service drops, falling branches or ice on 

three-conductor overhead service drops, and 

even a loose connection of the neutral in a service panel. Service drops with aluminum neutral 

conductors are more prone to this type of fault. 
Disturbances and Remedies - 11 

Utility engineers can report many anecdotes 

about that type of disturbance. 

As the box "When a Neutral Opens" explains, 

what happens is that if the loads on the two 

When a Neutral Opens 

Open neutral connection. in 120 1-to-\. CLI.;- 

t0111er illdt;i~[:~tiOll~ can occur under wwral circumstance.;. including: 

W~en corrosion of ;un aluminum underground scnke re~cheb an acute Stag! 

\Yhen the neutral nke of n .;cparLlre-c.cxductor senicc drop is brnlien h!- Giling 

hranches or icing 

\Yl~en an intermittent loow connection 

exists in the service n:~nel 

(Note that all of the :~ho\e are .'\\-lien" C~~ILISes-not "if and n.hen"-hecause ;dl of these 

circu~~~stance~ are somcnh~t likel!. ro occur :it 

some point: it is onl!- a marlel- of pldxlxlir! 

and frequency of nccurl-ence. 1 

In 0-pica1 installations. the t\\o hal\.es of 

the pon-er suppl!.. on e~ch side of rlie centertap neutral connecrion, are dciom exactl!- 

I~alanceci. and 

sides of the 120/240-V custonier installation are 

not balanced. the side w~th the lightest load 

experiences a large increase from 120 V, theoretically almost up to the full 240 V 

(see Figure 1.11). l'he on[! remaining connei,- 

tion is the r\\c lines. Ll :ind 1.1. x.ross \\ hic.11 - the full 2tO-\- supply is niaintainccl. 

'[he putenlial xt the midpoint Iwt\veen thc 

tn-o Ioatls %, :mil Z2 \\-ill be w~~ie\\~I~ere 

i>et\\-em1 thc potential oi LI kind L1, in in\-ersc. 

proportion to thc \-alucs oi Zl mil Z2. If, for 

instance. Z2 i\ rn~~ch IOU el- than TI. a 'll SS 

connectecl on the L1 side \\-ill experience a 

se\.ere o\.en oltagt. (as \xi11 the equip~nent represented I>). ZI, Hone\-er. ~hile mosL equipmen1 h:is some toieranc'e hr 3 moilemre o\w- 

\ck~ge. TYShs. in prticul;i~- those that claim 

inn clamping \ ollnge. are quite wnsitil-e to that 

condition. Tlii:. sir~ution is prol,.,il>l!. the cause 

of most reported catastrophic Failures of T\-SSs. 

Some p~~ldications on powt.1- qualit!- include 

an illustration of n scren driver (presumalAy 

intended to tighten loose connections i n-it11 3 

caption that reads -'the most useful powerqiuali~ tool"! 

Effects of Temporary Overvoltages on Equipment 

Overvoltages, whether a result of distribution 

system faults or open neutrals, can be quite 

destructive for equipment if allowed to last more 

than a few cycles (~n which case they might fall 

in the category of swells). Power equipment is 

designed to survive these overvoltages: transformers are likely to saturate, providing some 

sometimes are 

voltage reduction on the secondary. Distribution 

arresters are generally selected for their ability to 

survive temporary overvoltages. However, many 

consumer-type nSSs are likely to fail during a 

temporary overvoltage [see box, "Lower Is Not 

(Necessarily) Better"]. In Fact, the major cause of 

TVSS failures is a temporary overvoltage, rather 

than an unusually large surge. 

highly unbalanced. 

If the insral1:lrion 

neutl-al beconics 

clisconnectecl from 

the utilih. neutral. 

voltages and I> 

appear on each 

side of the non-- 

disconnected 

Line 

240 , Neutral1 

pund yX voltages 

I~O v neutral v2 

Line 

inst:tllation IICL~XI FIGURE 1.1 1: Unequal line voltages caused by an open neutral. 
12 - Section One 

Not Enough 

Voltage 

Lower Is Not (Necessarily) Better! 

The funclanienral purpose of a surgc-protectlw 

device is to reduce tlie stress imposed on load 

equipment nkn surges occur on the :\C 

power system. Surge protective de\.ices (SPDs) 

do this by di~wting the current of an impinging surge to gro~ind through a low impedance. 

The effect is a subsrantial reduction of the 

impinging voltage surge. 

.b SPD is a volrage divider in n-hich the 

vo1t;lge on its low side (the side connected to 

the load) becomes lower as the surge current 

increases. "cla~nping" the ~olrage ilnpressed on 

the load. 

Before the proliferation of SPDs. made possible by the development of metal-oxide varistors (MOVs). the perception existed that the 

threat of surges was the voltage they can 

develop at the terminals of a load. Thus. 

people thought that clamping that voltage 

to a Ion- lexd was desirable and, intuitixdy 

but erroneously. the lower the better. This 

perception was reinforced by the decision of 

the Underwriters Laboratories to require manufacturers of TVSSs (UL Standard 1449) to 

show tlie clamping voltage of their product 

on the package. picking fi-om a List of discrete 

steps starting with 330 V for 120-V applications. This UL requirement triggered a 

Remedies against Temporary Overvoltages 

The nature of temporary overvoltages makes it 

difficult if not impossible to prevent them, and 

therefore they must be accepted as a probable, 

but hopefully rare, event. Surges can be diverted 

because the energy levels to be absorbed in the 

OUTAGES 

Outages represent the worst type of disturbance 

for the operations of a customer. They can have 

a duration as short as a few cycles, the typical 

situation when the breaker of a feeder trips out 

on a fault and the fault is cleared, with automatic reclosing (Figure 1.12). Other outages can be 

much longer, as when the distribution equipment suffers a major fault (downed lines, catastrophic failure of transformers or switchgear). 

tiown\~ard ,,auction' among mnnufacrurers 

who xwnced to be in the 330-V categor?. 

overlooking the undesirable side effects of 

such a tight clamping. 

Actually. most load equipment is more 

robust to surges than Tb5S manufacturers 

imply by offering these low clanlping \.olrages. 

For instance, a 500-V clamping voltage would 

be quite adequate for protecting equipment. 

Furthermore-the point of the axiom ,'Lower is 

not better!"-a n;SS clamping at 500 V would 

nor respond to most swells or temporary overvoltages, a characteristic that is highly desirable. Such a passix.e sinration would help in 

retarding the aging process of MO\'s. More 

important, it certainly would reduce the incidence of the catastrophic failures that are periodically reported in trade magazines. 

Some manufacturers have responded to the 

argument by offering guarantees or no-questions-asked replacement. Nevertheless, failure 

of a WSS from a temporary ovenoltage might 

still be a traumatic experience for a homeowner. Those few manufacturers who subscribe 

to the "Lower is not better" philosophy should 

be rewarded by being chosen when consumers go through the quanda~ of@.ing to 

select from the multitude of WSSs offered on 

the shelves. 

diversion are limited. In contrast, a temporary 

overvoltage involves the full power of the system, and no device can absorb that level of 

energy. As noted above, some equipment can 

be designed to withstand the overvoltages, but 

that decision is beyond the control of a utility. 

Outages rarely damage equipment directly. 

Indirectly, of course, industrial processing equipment (for metals, plastics, textiles, semiconductor 

devices, and so forth) shut down by an 

unscheduled outage can suffer damage. The 

material under process is not only mined but 

can also jam the equipment, with painful and 

time-consuming cleanup operations. 

Less dramatic consequences or cessation of 

operation can range from inconvenience to loss 
Disturbances and Remedies - 13 

FIGURE 1.12: A very brief outage (top) and a very long outage (bottom). 

of revenue. Individual consumers also can suffer 

from loss of power needed for heating, air conditioning, and food refrigeration. One utility, 

with a mixture of seriousness and facetiousness, 

used to describe the severity of outages by the 

number of claims filed for spoiled freezer loads 

of frozen raspberries! 

The obvious remedy against outages at the 

customer level is to provide a standby source of 

power, either a storage battery or an enginegenerator set. The battery-power approach, generally called an unintemptiblepower supply 

(UPS), is a very popular remedy. It is applied at 

all power levels, from the small package favored 

by reliability-conscious computer users, to a 

building-wide system where loads are segregated into essential and nonessential. There are 

various types of UPS offered by manufacturers 

in a highly competitive market, each with performance characteristics aimed at minimizing or 

avoiding altogether the momentary disturbance 

when power is transferred from the utility to the 

standby source. 

For large industrial 

loads, schemes of dual 

feeders with an automatic 

transfer switch have been 

applied successfully by 

mutual agreement 

between the customer 

and the utility. Such an 

approach is justified 

when the financial and 

operational cost of an outage justifies the investment in a dual feeder system. Pessimists have 

noted, however, that when an installation 

depends on two feeders, it might be subjected 

to twice as many sags because each feeder carries a likel~hood of sags. 

SAGS 

Power quality engineers call "sag" an event 

when the line voltage is reduced for a few 

cycles to a level of less than 80% of the normal 

voltage (Figure 1.13). This type of disturbance 

can trigger upset or shutdown of control circuits. 

Sags rarely cause equipment damage but are the 

cause of many complaints of malfunction. 

Sags have their source in faults in a feeder that 

cause a large current to be drawn in the feeder, 

hence a voltage drop in the bus from which 

other feeders draw power. Many power quality 

engineers consider sags as the major cause of 

equipment malfunctions-but rarely, if at all, of 

damage. Upsets affect primarily the information 

technology equipment. Also affected are simple 

power devices controlled by a magnetic motor 

starter, which can drop out and stop a process. 

Field studies of sag-related disturbances in processing equipment have revealed that the source 

of the problem can be a simple relay in the control system, rather than a major disturbance in the 

power equipment. In such cases, a very effective 

remedy is to provide the control system with a 

UPS, or even with a simple constant-voltage 

transformer that can ride through most sags. 

BROWNOUTS 

In periods of hlgh demand where the system 

capacity is reached and would be exceeded, utilities reson to the scheme of deliberately reducing 

the voltage by a few percent. The effect is a 

FIGURE 1.13: A sag lasting 10 cycles with the line voltage reduced to 

55% of normal. 
14 - Secton One 

reduction of the power consun~ed by most loads, 

with some exceptions in the case of process controls that include a voltage regulating scheme 

that defeats the objectwe of the brownout. 

SUSTAINED UNDERVOLTAGES 

A very severe brownout might cause overheating of compressor motors, and some people 

believe that domestic refrigerators therefore 

should be disconnected when the lights are very 

dim. This perception needs clarification, and utility engineers should quantfy the risks involved. 

Another damaging consequence might be the 

failure of some electronic voltage regulators built 

into computer-based equipment (generically 

called "information technology" equipment). 

Such equipment has an intermediate regulating 

stage that can become overloaded and overheat 

when attempting to compensate for the voltage 

reduction. Anecdotes have been circulated, and 

the phenomenon has been demonstrated in the 

laboratory, but is confined to isolated cases. It 

is recounted here as a yet another hint that 

equipment failures should not blindly be attributed to surges. 

CHARACTERISTIC CURVES 

The information technology industry has developed a characteristic curve describing the tolerance of equipment to undervoltages (mostly 

sags) and overvoltages (mostly surges). That 

curve, n ell known to power-quality speclalists 

as the CBfibk4 curve, has recently been updated 

ancl IS now called the Z77C cwve (for the 

Inforniatlon Technology Industry Council). See 

box. 'The CBMA Curve." 

FLICKER 

When light sources (mostly incandescent but 

also some fluorescent) are supplied from a 

power line in which repetitive sags occur, a 

flickering effect is produced that h~unans find 

annoying. The correct term to describe the 

The Case of the Flickering Chandelier 

In one nnecclote. a customer comphined of 

tlickering lights to the electric utilit!-. \\ liich 

installed a strip-cl~itr~ecortlcr :kt 111c sen ice 

entrance in response (:IS if that coulcl cletecr 

small tli~crualions!). Of course. none \yere 

cletected. It turned our 111x1 the customer l~atl 

left an enipt!. electric skillet on \vhile suppeln.ns king enjoyed in the dining room. 111 

that \.int:tge-era house. the sliillet ( 1500 n atrs 

on a =l-+.\KG wire) nnd the chandelier 

n-ere on the same Ixtnch circwit. The flicker 

n-as cnusrtl h!. the thermostat of the skillet 

cycling on and off. Flickering cmdles on the 

dining room tahle ma\. be ro~ixintic. hut :I 

flickering chandelier is declared :innoying. 

The CBMA Curve 

111 the 1:lre 19'0s. computer mnnuf;~cti~rers and users 

reached a consensus on the pawn quality (use of the term 

had just sta~~ed) that woulcl he necess:u.)- to ensure ~indisturbecl operation of computers. The concept-as a design 

god. not a specification-\~:ts first proposed as relev:~nt to 

mainfi:~me compurers and presented in the form of a cloiihle cun.e showing a lo~wr limit :II~ an upper limit for 

acceprahle mains \.oltage. or. in other n-orcls. the clesi~.ahlr 

rolel.ance of eq~~ipment to ponw supply rariations. This 

~IXIIT became known :IS the CBEALI curve and n-:IS soon 

consiclererl-perhaps nor an appropriate extension-as 

,~pplicahle to some eleclronic equipment other than computers. ancl n.as cited in sever:ll stand:ircls. The origin:ll 

cun.e nxs a ch:tlIenging consensus-building effort. It was 

:I committee agreement on what people thoi~ght the 

equipinent could stand. It was not rhoroughly tested or vetifiecl zit t1i:lt time. Although the ponw-supply ~echnologies 

of husiness equipment have improwcl. some m:tnuf~~cturers 

:[re still reluctant to incorporate them into thcir procli~cts 

hecause of competitive market constlxints. 

In the 1990s. incrr:ising intcrcst in solving ponw quality 

prohlems led to c.xtensive resr:trcli in thc tole~ince of various cclurpment to power supply clisturlxmcrs, in particular 

.;;igs. Changing technolog!- in computer equipment-non. 

classified as infomiation technology equiplnent (ITE) also 

led ro >I revision of the lin~its, anel :I re\-ised curie xis 

issued in 1996 17). the Information Technology Incli~st~~ 

Council IITIC). together with an qq>lication note (Figure 

I. 14). 

Cpdxez to this information may he found ;tt the x'eh sire 

http: w-~\~.chenla.org itic sire-map inclcs.lltml 
Disturbances and Remedies - 15 

breakdown concern 

106% 

100% tolerance envelope 

Lack of stored energy ~n 

some 

equipment 

manufactures' - . ' 30% 

096000~ obi I I1 I I I 

01 0510 610 30 1001 1000 

Time in cycles (60 Hz) seconds 

500 - ----- 1 

120 L --* Voltage tolerance - +-I - 1 

- envelope 

'O . t-- - -r I 

"& ' 'it, i ' I 'd I ""% ' 'I& ' .'i'doo' doc 

lms3ms Mrns 05s 10 s Stear 

Two scales on horizontal axis: 

1. Duration in cycles 

2. Elapsed time 

behavior of the power supply is uoltngejltictuntioiz, but jlickeriizg is often used to describe the 

quality of the power, even though it is only the 

effect, not the cause. 

Voltage fluctuations can be considered repetitive sags OF low amplitude (the human eye can 

detect light output variations caused by a fraction of a percent fluctuation in the voltage, 

when the fluctuations occur at rates ranging 

from a few seconds to about 20 per second). 

Typical sources are arc furnaces (not too many 

around) and welding machines (arc and resistance spot welding). 

There is no remedy that the customer can 

apply when the fluctuations come from an intermittent load of a neighbor. (Be sure that the skillet or flat-iron is not on!) If the complaint sounds 

serious, the only remedy is for the utility to 

investigate where the intermittent load is, and 

negotiate a solution with the offender. Power 

quality specialists are acquainted with a variety of 

solutions, but each is to be applied case by case. 

FIGURE 1.14: The original CBEMA curve (top) and the updated lTlC 

curve (bottom). 
16 - Section One 

Other Other disturbances, less frequent than the "too - - 

Powelcline much" and "not enough" lust described, can also 

occur as the result of the operation of the distrlDisturbances bution system and interactions wlth customel 

loads. ~hese disturbances include noise, harmonics, notches, unbalance, and carrier signals. 

NOISE 

The term noise is loosely used to describe small 

disturbances (a few volts at most) at high frequencies (note the plural). See Figure 1 15. The 

sources of noise include chattering relays (a 

short-duration event) and coupling of radio frequencies from a nearby broadcast antenna (a 

quasi-permanent situation). 

FIGURE 1.15: Noise superimposed on an AC voltage. 

In keeping with Federal Communications 

Commission (FCC) requirements, most domestic 

equipment has a filter in the power cord that 

limits the emission of high frequencies back 

into the power cord. Industrial equipment has 

similar FCC requirements, but less stringent. By 

reciprocity, this filter also limits the penetration 

of line-conducted noise into equipment; this 

fact is worth keeping in mind when considering 

the purchase of a TVSS making claims of 

adding noise filtering to its prime mission of 

surge protection. 

HARMONICS 

Harmonics are currents 

and voltages at frequencies that are multiples of 

the fundamental 60-Hz 

waveform (Figure 1.16). 

They are the result of 

normal operation of certain loads, called nonlinear because their 

Impedance is not constant or because they draw 

currents that are not proportional to their 

impedance. This type of load is becoming more 

widespread as consumer electronics proliferate 

and as new-, sophisticated power-control 

schemes aimed at improving efficiency are built 

into some major appliances. The presence of 

large harmonics is readily visible in the voltage 

waveform. Small, but potentially objectionable, 

harmonics require a more sophisticated instniment, such as a power-quality monitor, to detect 

and quantlfy them. 

Effect of Harmonics on Equipment 

As a result of the increase in occurrence of harmonics, the subject has become a hot topic (pun 

intended) because the effect on equipment can 

be severe overheating. The problem starts 

because nonlinear customer loads generate currents at harmon~c frequencies. (In the jargon of 

the applicable standards, this is called harmonic &. 

emission.) There are several undesirable results 

from this situation: 

1. Effective (root mean square, or RiiS) currents in conductors are increased, in particular in the neutral of three-phase systems. These increased currents can cause 

overheating because the wiring installation, done in accordance with earlier versions of the National Electrical Code 

(NECm, trademark of the National Fire 

Protection Association), made no provision for that situation. 

2. The harmonic currents clrculate in the 

deltz-connected secondary of wye-delta 

transformers but not in the primary side, 

therefore primary overcurrent protection 

is not effective and the secondary can be 

severely overheated. 

FIGURE 1 .l6:An AC voltage distorted by harmonics. 
Disturbances and Remed~es - 17 

3. If the harmonic currents are not filtered include the providing filters as a retrofit option. 

out or canceled at the point of common As of 2001, the issues are still the subject of 

coupling (as they are in 2 above), the much debate, and should be reviewed by 

currents flow in the utility distribution sys- power-quality specialists before expensive 

tem and cause a voltage distortion in the and possibly counterproductive measures 

supply of adjacent loads, proportional to are implemented. 

the current and the utility system impedance. In other words, systems with rela- NOTCHES 

tively low available short circuit capacity "Notches" can be created in the supply voltage 

will experience more voltage distortion when large power-electronic drives in adjacent 

for a given nonlinear load than systems loads cause a momentary short circuit between 

with high capacity. the phases that power the drive, each in turn. 

These are called commz~tation notches and occaRemedies against Harmonics sionally cause some interference with other 

Remedies against harmonics are essentially com- loads that use the 60-Hz power frequency as a 

promises in a range of extremes. One such com- controlling signal (Figure 1.17). 

promise is to control harmonic emission by In a sense, notches may be considered as a 

mandating limits for each and every piece of special case of harmonic emission, and the 

equipment, the approach presently taken by remedies, if interference is noted, are similar to 

some European countries. Another approach, those mentioned for harmonics in general. 

which has gained acceptance in the United States, 

is a voluntary compromise 

where limits for harmonic 

emissions at the point of 

common coupling are 

only recommended. 

Consumers have practically no control over the 

harmonics that their 

', ', 

FIGURE 1.17: Commutation notches on an AC voltage. 

equipment can generate, 

but the perception in the 

United States is that, for the moment, they do 

not pose problems. This laissez-faire attitude UNBALANCE 

mlght change if harmonic-generating loads such Voltage unbalance between phases occurs when 

as electronic ballasts and variable frequency dri- a three-phase system supplies single-phase loads 

ves for heating and air conditioning were to that draw unequal currents. Three-phase loads 

become a larger portion of the total consumer supplied under those conditions can be adverseload. ly affected, with overheating of motors in particIn commercial and office buildings with older ular as a symptom. Variable-frequency drive syswiring and a large amount of information tech- tems have a tendency to magnify the problem 

nology equipment, supplied single-phase from a by skipping some OF the six half-cycles that are 

three-phase system with shared neutral, harmon- expected, each in turn, to deliver power to the 

ics can cause overheating problems. Later ver- drive. Thus, a severe current unbalance can 

sions of the NEC recognized the problem and result from a moderate voltage unbalance. 

have mandated larger ampacity For shared-neu- The remedy for this situation is under the 

tral conductors. control of the end user and is simply to reassess 

Industrial customers are more concerned the allocation of single-phase loads from the 

about harmonics because some of their loads three-phase system. 

can have a significant emission. Remedies 
18 - Section One 

CARRIER SIGNALS These are isolated cases for which case-byOccurrences of interference fro111 carrier case remedies have been developed by powersignals have been described in anecdotes. quality specialists. 

System THE PROBLEM 

Interactions A special kind of surge problem is that of an 

interaction between the power system and a 

communications system, as briefly mentioned in 

the beginning section of this part, "Surges." This 

case merits special attention because it can be 

misinterpreted as being caused by the utility 

Shifting Reference Potentials 

To illustsate the problem of shifting reference 

potentials. a lal>orato~)- replica of a residential 

wiring system xvas used to malie nleas~11-ements during surge events produced hy injecting a surge into the wiring. In Figure 1.18. 11 

modern-equipped PC is connected 11). its 

pon-er porr to a lhranch circuit. and by ~ts 

tnocleni port to the telephone service of the 

house. For a worst-case scenario. the power 

ancl telephone se~~ices enter the house at 

opposite ends. 

.in open loop is formed by the copper pipe 

or ground concluctor used as a bonding cotld~ictor. the eq~~ipment grouncling concluctor of 

the branch circuit feeding the PC. and the telephone wires from the netn ork interhce device 

(KID) to rhe PC. If a surge impinges on the 

external telephone plant. it is 

diverted by the TID via the 

copper pipe to the cornmon 

grounding point of the house. 

:1t the poxer senice entrance. 

The surge current in the copper pipe creates a changing 

magnetic tlus around the pipe. 

which induces a voltage in the 

loop. This voltage xvill appear 

benveen the m-o I'C posts if 

they are separated by a high 

impetlance (of unknon-n surge 

power supply. Furthermore, the problem can 

arise even if both of the systems have been provided with surge protection, leaving a customer 

thus afflicted puzzled or disappointed. The effect 

of this interaction is to shift the reference potentials of the two ports during a surge, as explained 

in the box *'Shifting Reference Potentials." 

pip-n-l~icli can be espected in residenlial 

n.iring-a large loop is formed. embracing the 

fl~lx produced by the surge current in the copper pipe. 

Figure I 19 s11on.s the recording olh~ainecl 

in the laboratory replica of residential wiring. 

For a rate of change in the surge current of -5 

.A )IS (amperes per microaeconcl). typical of 

standard test wiveforms a peak of i.3 k\. is 

induced in the loop and appears betn-een the 

m'o ports. 

.\ relatively simple retrofit solution is to 

cq~lalize the difference of voltage bemeen the 

two systems by 3 device designed for the puspose and inserted in both communications ancl 

pon-er links j~lsr before they enter [he nppliance. This device, defined in IEEE Standard 

1100- 1992 as a "surge reference equalizer." is 

y Cold water ppe 

device 

-- 

volrage withstand capacity). FIGURE 1.18: Power and telephone services enter the house 

Wth the telephone wires rout- at opposite ends. A personal computer is connected across 

ed avay from the copper the two systems. 
0 

05 

OOL g 

0 

E 

OSL 8 

ooz 

OZ 81 91 PI ZL 01 8 9 I 0 

loimpuoa an!i3alold 3 

P 

pue uod auoqdalai 002 

uaawaq afieilon =A A 

xeu I\ 00z f OOP 

~oi3npu03 an!i>aio~d 

pue uod auoqdaja] 

uaamiaq afieilon =A 

61 - salpaluau pue sa3ueq~nisa 

D~sturbances and Remedes - 21 

REMEDIES AGAINST SYSTEM INTERACTIONS 

Fort~inately. indusq ha recogi~~zeil ihe problem and offen 3 line of devices spec~all!- 

designed to pl-ocect against rliose spec~al. but 

pre\ alent. surge pl-ohlems. Tlxs t> pe of deuce 

can be recognized easdy because it lm i 11 m 

inp~~t line cord with output ponei ieceptacles 

and (21 mo telephone modular i;icIis (or \.idea 

coax connectors) to insert In the telepllone connectlon (or video cable connection) The PI-ope1 

engineering term for this ilev~ce IS .iii/::e I-efeveuce eqz~nlizev (SRE). but here again, popular 

usage has not 3dopted the eng~neerlng jargon 

.sz~ppressoi- wirh added \\.ords to ciran- attention 

to the mo-port system. 

To place the operation of 3 surge equalizer in 

perspeitlve, visualize the m-o po~rs of the 

equipment and their ground rekrences, as In 

F~g~ire 1.21. During a surge event on one system. there 1s a transient unhdr~nce betn.een the 

m-o input references. wlhich cm be made worse 

n hen thc seivice entrances a]-e at opposite ends. 

Inaertq an SRE lust behind the T'v' set almost 

re-establishes a balance between the m-o ports 

The ideal sltuation wo~~lcl beto first haw the 

m;o sen-lces on the same sde. and as 3 finlsl-iing 

and rlie device is often called slmpl>- J sz~ige toach still provide an SRE 

Power Yideo 

Video 

Bad Better Best 

FIGURE 1.21: Shifting reference potential can be remedied by inserting a surge reference equalizer on the communications and 

power lines (here, the appliance is a TV and the communications line is a TV cable, but a PC with a telephone modem connection 

presents the same problem). In the ideal situation, the communications and power lines enter the house on the same side, and 

the SRE is most effective. 
Quest~ons to Ask - 23 

In This Section Customer-owned offenders; how to use the worksheets; identiFying residential 

and commercial appliance categories; Worksheet EDE: electronic, dual, external; Worksheet EDI: 

electronic, dual, internal; Worksheet ES: electronic, simple; Worksheet HE: heat, electronic; 

Worksheet HM: heat, mechanical; Worksheet ME: motor, electronic; Worksheet MM: motor, 

mechanical; Worksheet PLC: Power line conditioning 

This part of the manual is intended to facilitate 

the interactions between a customer and a cooperative's service representative in tracking down 

the cause of malfunction or damage and offering 

remedies when possible. Hopefully, this procedure will serve the common interests of both 

parties, but, as a note of caution, not all problems can be solved over the telephone, and in 

some cases it might be necessary to call in a 

power quality specialist to study the problem 

and identify possible solutions, just as some 

medical problems can be described over the 

telephone to the family doctor and a suitable 

prescription be picked up at the local pharmacy, 

but other problems require a visit to the doctor's 

office and even a referral to a specialist. 

While the main thrust of the manual is the 

effect of the utility supply on equipment-with 

the equipment characterized as "victim"-there 

are also cases of disturbed equipment that are 

associated with the customer's own operations 

where some other equipment can be characterized as a troublemaker or "offender." These 

offenders are listed in Table 2.1, for a quick 

check that the reported problem does not fall in 

that category, so that the dialogue can then 

focus on the suspected interaction between the 

utility power supply and the equipment problem. 

CustomerOwned some appliances generate disturOffenders bances that can cause a malfunction of other appliances in the 

same installation, or even in 

neighbors' installations. These 

disturbances are not attributable 

to the utility, but an uninformed 

customer might still make it a 

subject of complaint to the utility. Table 2.1 describes typical 

disturbances, their causes, and 

possible remedies. 

TABLE 2.1: Home-Based Disturbances, Causes, and Remedies 

TV remote disabled 

when lamp is on 

Fi~ckermg lamps 

Disturbance Cause Remedy 

Interference from 

fluorescent lamps 

Load cycling [electric 

skillet, laser ~rinter) 

Change type of lamp 

Plug loads in other 

branch circuits 
24 - Section Two 

HOW to Use 

the Worksheets 

The procedure of troubleshooting consists of 

the following steps: 

1. Obtain from the customer a description 

of the victim equipment, and categorize 

the type, using Table 2.2, a list of appliances likely to be found in residential 

and small-business installations. 

2. Turn to the diagnostic worksheets corresponding to the type of victim equipment 

identified in step 1. The worksheets are 

structured in three parts: 

a) History and symptoms 

b) Tentative diagnostics and remedies 

C) Disposition of case 

Identifying For the purpose of narrowing the tentative diagResidential and 

Commercial 

Appliance 

nosis, Table 2.2 lists several categories of equipment victims. To allow good understanding 

between the customer and the service representative, it will be useful to pin down, early in the dm 

Categories logue, what is the specific appliance category to 

be discussed. When the category is thus pinned 

down, the "script" for the dialogue can be found 

in one the the eight work sheets at rhe end of the 

manual. The customer representative should photocopy blank work sheets and keep a supply of 

them to be filled in as the dialogue progresses, 

then file them for future reference or additional 

review. For easy reference to the corresponding 

work sheet, the categories identified by the table 

are associated with a code that appears in bold 

type on the top right comer of the work sheet. 

MOTOR-DRIVEN APPLIANCES AND HEATING 

APPLIANCES 

For each category (motor-driven or heating), 

there can be two or more types, depending on 

the type of control used: 

Mechanical control (on-off, rotary, etc.- 

no sophisticated keypad or other electronic 

control) 

Electronic control (keypad, display, etc.) 

These different controls influence the tentative 

diagnosis. Consequently, motor-driven and heating appliances are divided into four kinds, with 

3. Obtain from the customer as much background information as possible, using 

Part A of the worksheet as a script for 

the dialogue. 

4. Reviewing the information thus obtained, 

ask further questions as appropriate 

according to Part B of the work sheet. 

5. Present to the customer a tentative diagnostic and possible remedy (some problems might be beyond simple remedies). 

the following codes in Table 2.2. 

1. Motor, mechanical MM 

2. Motor, electronic: ME 

3. Heat, mechanical: HM 

4. Heat, electronic: HE 

ELECTRONIC (COMMUNICATIONS) APPLIANCES 

This generic category includes telephones, audio 

and video equipment, and personal computers. 

Here again, two types must be recognized: 

1. Appliances with a simple, one-link connection to a power system (or to a telephone system for simple sets). 

2. Appliances with a dual connection to both 

power and communication. Such appliances 

can be subdivided further into two types: 

a) Appliances that are powered as well as 

linked to an external communication 

system such as telephone line, rooftop 

antenna, cable TV, or satellite dish. The 

exposure of this type of appliance is 

significant because surges of external 

origin can come in through either the 

power line or the communication link. 

They can be caused by system disturbances or by remote lightning strokes. 

b) Appliances that are powered as well as 

linked to an internal communication 

system, such a garage door opener, 

burglar alarm, intercom, thermostat, or 
Questions to Ask - 25 

computer-controlled appliance. The 

exposure of this type of appliance, 

even though it involves two systems, is 

lower than that OF systems with external links. Disturbance or damage associated with the internal communication 

links is limited to the rare case of a 

very close lightning stroke Inducing a 

voltage in those internal links. 

The absence of a communication link, or the 

type is a link is present, will influence the diagnosis. The types of electronic appliances can be 

assigned these codes in Table 2.2: 

Electronic, simple: ES 

Electronic, dual, external: EDE 

* Electronic, dual, internal: ED1 

POWER LINE CONDITIONING EQUIPMENT 

Surge suppressors and un~nterruptible power 

supplies are given the code PLC in Table 2.2. 

rABLE 2.2: Categories of Equipment Victims 

Codes: 

EDE = electron~c, dual, external HM = heat, mechanical 

ED1 = electronic, dual, internal ME = motor, electronic 

ES = electronic, simple MM = motor, mechan~cal 

HE = heat, electron~c PLC = power line conditioning 

Appliance I Category as victim I Work sheet 

Burolar alarm, indeoendent 1 Electronic dual, internal 1 ED1 

Air conditioner, central, conventional 

Air conditioner, central, variable speed 

Air conditioner, window 

Antenna rotating system 

Attic fan, thermostat controlled 

Automatic lawn sprinkler 

Boom box 

Burqlar alarm, telephone link 

Clothes dryer 

Motor, mechanical 

Motor, mechanical 

Electronic, dual, internal 

Motor, mechanical 

Electronic, dual. external 

Motor, mechanical 

Electronic, dual, external 

Electronic dual, external 

Electron~c, simple 

Electronc dual, external 

-- 

Cell phone charger 

Central computer for business 

Centrex telephone system 

Clock radio 

Motor, mechanical or electronic 

Heat, mechanical or electronic 

MM 

MM 

ED1 

MM 

EDE 

MM 

ED I 

EDE 

ES 

EDE 

Coffee maker I Heat, mechanical 

Electronic, simple 

Electronic, dual, external 

Electronic, dual, external 

Electronic, dual, simple 

ES 

EDE 

EDE 

ES 

Computerized thermostat system 1 Electronic, dual, internal I ED1 

I I 

Computer network ED1 or EDE 

Dehumidifier 

Desktop publishing system 

Electronic, dual, external only or internal 

Motor, mechanical 

Electronic, dual, internal only or external 

M M 

ED1 or EDE 
26 - Section Two 

Digital video disk player I Electronic, simple 1 ES I 

TABLE 2.2: Categories of Equipment Victims (Cont.) 

I Doorbell, sophisticated I Electronic, dual, internal I ED1 1 

Appliance 

Digital clock, electronic 

Digital clock, mechanical 

I Fax machine 1 Electronic, dual, external 1 EDE 1 

Category as victim 

Electronic, simple 

Motor, mechan~cal 

Distributed home entertainment system 

Electric car battery charger 

Exercise equipment 

Work sheet 

ES 

MM 

I Fluorescent light~ng system ( Electronc, dual, internal I ED1 I 

Electronic, dual, internal and external 

Electronic, simple 

Motor, mechanical or electronic 

Fire alarm system - 

Fluorescent lamp, compact 

Fluorescent liqht, maqnetic ballast 

I Fluorescent light, electron~c ballast, single I Electronic, simple 1 ES I 

€01 and EDE 

ES 

MM or ES 

Electronic, dual, internal and external 

Electronic, simple 

Heat, mechanical (eauivalent to] 

1 Garage door opener 1 Electronic, dual, internal 1 ED1 1 

EDE and ED1 

ES 

HM 

Food mixer 

Freezer 

Furnace 

I Heat pump / Motor, mechanical or electronic I MMorME I 

Motor, mechanical 

Motor, mechanical 

Motor, mechanical or electronic 

Ground-fault circuit interrupter, receptacle 

Ground-fault crrcuit interrupter, service panel 

Ham radio, transmitter w~th antenna 

Ham radio, receiver without external 

antenna 

M M 

MM 

MM or ME 

I Hot water heater, isolated I Heat, mechanical 1 MA 

Electronic, simple 

Electronic, simple 

Electronic, dual, external 

Electronic, simple 

Hi-fi system, concentrated 

Hi-fi system, distributed 

Home security system, telephone link 

ES 

ES 

EDE 

ES 

( Instant hot water for beverages I Heat, mechan~cal 1 HM I 

Electronic, simple 

Electronic, dual, internal and external 

Electronic, dual, external 

Hot water heater, computer controlled 

Humidifier 

HVAC (heating, ventilating, and 

air conditioninq) controls 

1 Intercom system 1 Electronic, dual, internal I ED1 I 

ES 

ED1 and EDE 

EDE 

Heat, mechanical 

Electronic, dual, internal 

Motor, mechanical 

Electronic, dual, internal 

HM 

ED1 

MM 

ED1 

Llght bulb, incandescent Heat, mechanical MH 
Cluestions to Ask - 27 

rABLE 2.2: Categories of Equipment Victims (Cont.) 

Appliance I Category as victim I Worksheet 

Light d~mrner / Electronic, s~rnple I ES 

Microwave oven I Electronic, simple I ES 

Personal computer, isolated I Electronic, simple I ES 

Personal computer, telephone modem 1 Electronic, dual, external I EDE 

Motion-detection lightng I Electronic, simple I ES 

Personal computer, cable modem 

Point-of-sale cash register 

Power tool 

Rechargeable flashlight/emergency Ighting I Electronic, simple I ES 

Electronic, dual, external 

Electronic, dual, external 

Motor, mechanical 

Sump pump 1 Motor, mechan~cal or electron~c I MMorME 

EDE 

ED1 

MM 

Range, k~tchen 

Refrigerator 

Satellite dish receiver 

Sink disposal 

Surge suppressor, permanent connection 1 Power line conditioner I PLC 

Heat, mechan~cal or electronic 

Motor, mechanical 

Electronic, dual, external 

Motor, mechanical 

Telephone desk set, powered I Electron~c, dual, external 1 EDE 

HM or HE 

MM 

EDE 

MM 

Surge suppressor, plug-in 

Surge suppressor, service entrance 

Surveillance camera system 

Telephone answering machine 

Telephone desk set, simple / Electronic, simple I ES 

Television receiver, cable input I Electronc, dual, external I EDE 

Power line conditoner 

Power line cond~toner 

Electronic, dual, external 

Electronic, dual, external 

PLC 

PLC 

EDE 

EDE 

TVSS, permanently connected I Power line conditioner I PLC 

Televis~on receiver, rabbt ear 

Television receiver, satellite input 

Trash com~actor 

WSS, plug-in I Power lhne conditioner I PLC 

WSS, surge reference equalizer 

Electronic, simple 

Electronic, dual, external 

Motor, mechanical 

Power line conditioner 

Electronic, dual, external 

ES 

EDE 

MM 

PLC I EDE 

Videocassette recorder, cable input I Electronic, dual, external 1 EDE 

Uninterruptible power supply 

Vacuum cleaner 

Vacuum cleaner, central system 

Videocassette recorder, satellite input 

Power line conditioner 

Motor, mechanical 

Motor, mechanical 

Electronic, dual, internal 

Electronic, dual, external 

PLC 

MM 

MM 

EDE 
28 - Section Two 

I Video conferencing I Electronic, dual, external I EDE 

TABLE 2.2: Categories of Equipment Victims (Cont.) 

I Washer, dishes 

Appliance 1 Category as victim 

Motor, mechanical or electronic 

Heat, mechanical or electronic 

Work sheet 

/ Water well pump, indoor, aboveground 1 Motor, mechanical or electronic 1 MMor ME 

Washer, clothes 

Water well pump, submersed 

Motor, mechanical or electronic 

Motor, mechanical or electronic 

Electronic, dual, external 

HM or HE 

MM or ME 

EDE 
Questions to Ask - 29 

EDE 

Worksheet EDE 

Electronic, dual, external 

A. HISTORY AND SYMPTOMS 

Appliance identity 

Name of customer 

Appliance in question 

C] Where located in building? 

Approximate age?years 

Symptoms 

Quit working during normal operation - 

C] Would not start when turned on - 

Smoke came out - 

Acrid smell - 

Blinking displays - 

Other - 

Has that condition happened before? 

Previous repair history - 

Did not report it - 

C] Reported it but no action - 

Suggested action failed - 

Don't know 

Weather at the time of the problem 

Blue sky - 

High winds - 

Ice storm - 

Distant thunder - 

Local lightning - 

C] Don't know - 

B. TENTATIVE DIAGNOSIS AND REMEDY 

Similar problem in neighbor's home? 

0 Yes - 

0 No - 

Don't know - 

Power system conditions 

Apparently normal - 

Problem occurred in conjunction with: 

A utility outage? 

Other incident? - 

Describe: 

Don't know - 

System interaction 

Proper bonding of power system and 

communications system? (Y/N) - 

Surge reference equalizer 

installed? (Y/N) - 

Other information and remarks by customer: 

I Diagnosis / Remedy 

I System interaction [most likely). See under A. I Install surge reference equalizer. 

I Temporan/ overvoltage I Repair if appliance is expensive, or replace. 

End-of-life burnout. (How old is equipment?) 

Mechanical switch failure 

Surge on the power line 

C. DISPOSITION OF CASE 

Replace. 

Repair 

Was there a surge reference equalizer? If yes, a temporay 

overvoltane is likelv. If no, install surse reference esualizer. 
30 - Sectron Two 

Worksheet ED1 

Electronic, dual, internal 

A. HISTORY AND SYMPTOMS 

Appliance identity Similar problem in neighbor's home? 

Name of customer 0 Yes - 

No - 

Appliance in question Don't know - 

Where located in building? Power system conditions 

Approximate age?years Apparently normal - 

Symptoms Problem occurred in conjunction with: 

Quit working during normal operation - A utility outage? - 

Would not start when turned on - Other incident? - 

Smoke came out 

Acrid smell 

- Describe: 

- 

Blinking displays - Don't know 

Other 

Has that condition happened before? 

Previous repair history 

Did not report it 

Reported it but no action 

Suggested action failed 

Don't know 

Weather at the time of the problem 

Blue sky 

High winds 

Ice storm 

17 Distant thunder 

Local lightning 

Don't know 

Other information and remarks by customer: 

How extensive are the communication links 

- (garage antenna, intrusion switches, thermostat controls, etc.)? 

( End-of-life burnout. (How old is equipment?) / Replace. 

B. TENTATIVE DIAGNOSIS AND REMEDY 

I Mechanical switch failure I Repair 

Diagnosis 

Surge on the power line 

Remedy 

- ~p 

Was there a surge reference equalizer? If yes, a temporary 

overvoltage is likely. If no, install surge reference equalizer. 

Temporary overvoltage I Repair if appliance is expensive, or replace. 

C. DISPOSITION OF CASE 
Lluestions to Ask - 31 

Worksheet ES 

Electronic, simple 

A. HISTORY AND SYMPTOMS 

Appliance identity 

Name of customer 

Appliance in question 

Where located in building? 

Approximate age?years 

Symptoms 

Quit working during normal operation - 

Would not start when turned on - 

Smoke came out - 

Acrid smell - 

Blinking displays - 

Other - 

Has that condition happened before? 

Previous repair history - 

Did not report it - 

Reported it but no action - 

Suggested action failed - 

Don't know - 

Weather at the time of the problem 

Blue sky - 

High winds - 

l"-J Ice storm - 

Distant thunder - 

Local lightning - 

Don't know - 

B. TENTATIVE DIAGNOSIS AND REMEDY 

Similar problem in neighbor's home? 

0 Yes - 

No - 

Don't know - 

Power system conditions 

Apparently normal - 

Problem occurred in conjunction with: 

A utility outage? 

Other incident? - 

Describe: 

Don't know - 

Other information and remarks by customer: 

Diagnosis 

End-of-life burnout, (How old is equ~pment?) 

Mechanical switch failure 

Temporary overvoltage I Repair if appliance is expenwe, or replace. 

C. DISPOSITION OF CASE 

Remedy 

Replace. 

Repair 

Surge on the power line Was there a surge reference equalizer? If yes, a temporary 

overvoltage is likely. If no, install surge reference equalizer. 
32 - Section Two 

Worksheet HE 

Heat, electronic 

A. HISTORY AND SYMPTOMS 

Appliance identity 

Name of customer 

Appliance in questlon 

Where located in building? 

Approximate age?years 

Symptoms 

Quit working during normal operation - 

Would not start when turned on - 

Smoke came out - 

Acrid smell - 

Blinking displays - 

Other - 

Has that condition happened before? 

[7 Previous repair history - 

Did not report it - 

Reported it but no action - 

Suggested action Failed - 

Don't know - 

Weather at the time of the problem 

Blue sky - 

High winds - 

Ice storm - 

Distant thunder - 

Local lightning - 

Don't know - 

B. TENTATIVE DIAGNOSIS AND REMEDY 

Similar problem in neighbor's home? 

0 Yes - 

No - 

C] Don't know - 

Power system conditions 

Apparently normal - 

Problem occurred in conjunction with: 

A utility outage? - 

Other incident? - 

Describe: 

Don't know - 

Other information and remarks by customer: 

C. DISPOSITION OF CASE 

Diagnosis 

End-of-life burnout. (How old is equ~pmentll 

Mechanical swtch failure 

Surge on the power line 

Temporary overvoltage 

Remedy 

Replace. 

Repair 

Was there a surge reference equalizer? If yes, a temporary 

overvoltage is likely. If no, install surge reference equalizer. 

Repair if appliance is expensive, or replace. 
(luestions to Ask - 3

Worksheet HM 

Heat, mechanical 

A. HISTORY AND SYMPTOMS 

Appliance identity 

Name of customer 

Appliance in question 

Where located in building? 

Approximate age?years 

Symptoms 

Quit working during normal operation 

Would not start when turned on - 

Smoke came out - 

Acrid smell - 

C] Blinking displays - 

Other 

Has that condition happened before? 

Previous repa~r history - 

Did not report it - 

Reported it but no action - 

Suggested action failed - 

Don't know 

Weather at the time of the problem 

Blue sky - 

High winds - 

Ice storm - 

Distant thunder - 

Local lightning - 

Don't know - 

B. TENTATIVE DIAGNOSIS AND REMEDY 

Similar problem in neighbor's home? 

0 Yes - 

No - 

Don't know - 

Power system conditions 

Apparently normal - 

Problem occurred in conjunction with: 

A utility outage? 

Other incident? - 

Describe: 

Don't know - 

Other information and remarks by customer: 

I Diagnosis / Remedy 

C. DISPOSITION OF CASE 

End-of-life burnout. (How old is equipment?) 

Mechanical switch failure 

Temporary overvoltage 

Replace. 

Repair 

Repair if appliance is expenwe, or replace. 
34 - Section Two 

Worksheet ME 

Motor, electronic 

A. HISTORY AND SYMPTOMS 

Appliance identity 

Name of customer 

Appliance in question 

Where located in building? 

Approximate age?-years 

Symptoms 

Quit working during normal operation - 

Would not start when turned on - 

Smoke came out - 

Acrid smell - 

Blinklng displays - 

Other - 

Has that condition happened before? 

Previous repair history - 

Did not report it - 

Reported it but no action - 

C] Suggested action failed - 

Don't know - 

Weather at the time of the problem 

Blue sky - 

C] High winds - 

C] Ice storm - 

Distant thunder - 

Local lightning - 

Don't know - 

B. TENTATIVE DIAGNOSIS AND REMEDY 

Similar problem in neighbor's home? 

0 Yes - 

No - 

Don't know - 

Power system conditions 

0 Apparently normal - 

[7 Problem occulred in conjunction with: 

A utility outage? - 

Other incident? 

Describe: 

Don't know - 

Other information and remarks by customer: 

I End-of-life burnout. (How old is equipment?) I Replace 

Diagnosis 

Mechanical overload 

Remedy 

Check for jamming or seized bearing; clean out or repair. 

I Temporary overvoltage I Repa~r if appliance is expensive, or replace. 

C. DISPOSITION OF CASE 

Mechanical switch faG 

Surge on the power line 

Repair 

Was there a surge reference equalizer? If yes, a temporary 

ove~oltage is likely. If no, install surge reference equalizer. 
Quest~ons to Ask - 35 

Worksheet MM 

Motor, mechanical 

A. HISTORY AND SYMPTOMS 

Appliance identity 

Name of customer 

Appliance in question 

Where located in building? 

Approximate age?years 

Symptoms 

Quit working during normal operation - 

Would not start when turned on - 

Smoke came out - 

Acrid smell - 

Blinking displays - 

Other - 

Has that condition happened before? 

Previous repair history - 

Did not report it - 

Reported it but no action - 

Suggested action failed -- 

Don't know - 

Weather at the time of the problem 

Blue sky - 

High winds - 

Ice storm - 

Distant thunder - 

Local lightning - 

Don't know - 

B. TENTATIVE DIAGNOSIS AND REMEDY 

Similar problem in neighbor's home? 

0 Yes - 

No - 

Don't know - 

Power system conditions 

Apparently normal - 

Problem occurred in conjunction with: 

A utility outage? - 

Other incident? - 

Describe: 

Don't know - 

Other information and remarks by customer: 

I Diagnosis / Remedy 

I Mechanical switch failure I Repair 

Mechanical overload 

End-of-life burnout. (How old is equipment?) 

C. DISPOSITION OF CASE 

Check for jamming or seized bear~ng; clean out or repair. 

Replace. 
36 - Section Two 

PLC 

Worksheet PLC 

Power line conditioning 

A. HISTORY AND SYMPTOMS 

Appliance identity 

Name of customer 

Appliance in question 

Where located in building? 

Approximate age?years 

Symptoms 

Quit working during normal operation - 

Would not start when turned on - 

Smoke came out - 

Acrid smell - 

Blinking displays - 

[7 Other - 

Has that condition happened before? 

Previous repair history - 

Did not report it - 

Reported it but no actlon - 

Suggested action failed - 

Don't know - 

Weather at the time of the problem 

Blue sky - 

High winds - 

Ice storm - 

Distant thunder - 

Local lightning - 

Don't know - 

6. TENTATIVE DIAGNOSIS AND REMEDY 

Similar problem in neighbor's home? 

0 Yes - 

0 No - Don't know - 

Power system conditions 

Apparently normal - 

C] Problem occurred in conjunction with: 

A utility outage? - 

Other incident? - 

Describe: 

Don't know - 

Other information and remarks by customer: 

C. DISPOSITION OF CASE 

Diagnosis 

Surge suppressor and uninterruptible power supply: 

End-of-life burnout 

Temporary overvoltage (most likely) 

"Large" surge (quite rare) 

Uninterruptible power supply only: 

Battery problem? 

Remedy 

Replace 

Replace