RECOGNIZING AND OF ELECTRICAL EQUIPMENT · When you look at an electric wire that could be...

INTRODUCTIONOver the past years there have been many docu-mented firefighter fatalities by electrocution. Thepurpose of this program is to:� give you a basic knowledge of how electricity

works,� help you to understand basic construction,� explain configurations of the electric utilities,� make you aware of the hazards of electricity. This chapter will help you better understand whatprecautions need to be taken when workingaround electrical equipment.

Electricity is invisible. When you look at an electricwire that could be energized from 120 volts all theway up to 500,000 volts, it seems harmless enough.That is why electrical energy is often referred to asthe “silent killer” and remains a hazardous form ofenergy that has to be dealt with safely.

No matter what the voltage is in an electrical con-ductor, it is dangerous and can injure and/or killemergency workers.

Some people believe that 120 volts (normal house-hold current) is harmless. However, throughout theelectrical industry there have been people killed whenthey have made contact with 120 volts. Any voltagecan kill! It all depends on the situation, the amount ofcurrent involved, the part of the body affected, the du-ration of contact, and environmental conditions (wetor dry) at the time of contact.

Electricity is a blessing that is often taken forgranted and must be treated with respect. Electrocu-

tion is the fifth-leading cause of workplace death.The majority of these fatalities are caused by the fail-ure to recognize and avoid electrical hazards.

ELECTRICITY—THE BASICS

This section provides a general summary of electric-ity and electrical equipment. Key safety and tacticalpoints are indicated.

Suppose nothing is coming out of a hose, but thereis water under pressure inside it. If you open thevalve, the force of that internal pressure releases aspray of water. An energized wire is similar. Theforce that causes electrons to flow is called voltage,and like water, the greater the pressure pushing elec-tricity through a line, the higher the voltage. In waterterms the pressure is measured in pounds per squareinch. With electricity, pressure is measured in volts.

� Voltage is the electric force that causes the freeelectrons to move from one atom to another. Justas water needs pressure to force it through a hose,electrical current needs a force to make it flow. Avolt is the measure of electric pressure. Voltage isusually supplied by a battery or a generator.

� Current is electricity in motion. It measures theamount of electrons that can flow through a ma-terial like a conductor. Electric current is mea-sured in amperes, or “amps” for short. Amperesis like the amount of water flowing through ahose in a certain amount of time or the amount ofelectricity flowing through a wire.

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50 � CHAPTER #

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I RECOGNIZING AND AVOIDING THE HAZARDS OF ELECTRICAL EQUIPMENT

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RECOGNIZING AND AVOIDING THE HAZARDS OF ELECTRICAL EQUIPMENT

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� Resistance—The opposition to electrical currentflow, measured in ohms.

� Conductors—These are made of materials thatelectricity can flow through easily.

These materials are made up of atoms whose elec-trons can move away freely.

Some Examples of Conductors Are� Copper� Aluminum� Platinum� Gold� Silver� Water� People and Animals� Trees

Electricity will always take the shortest path to theground. Your body is 70 percent water, and thatmakes you a good conductor of electricity. If a powerline has fallen on a tree and you touch the tree you be-come the path or “conductor” to the ground and couldbe electrocuted.

� Insulators are the opposite of conductors. Theatoms in these materials are not easily freed andare stable, preventing or blocking the flow ofelectricity.



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RECOGNIZING AND AVOIDING THE HAZARDS OF ELECTRIAL EQUIPMENT � 51

Some Examples of Good Insulators Are� Glass� Porcelain� Plastic� Rubber

The rubber or plastic on an electrical cord providesan insulator for the wires. By covering the wires, theelectricity cannot go through the rubber and is forcedto follow the path on the aluminum or copper wires.

As mentioned above, electricity flowing through aconductor is similar to water flowing through a pipe.

If you take a water pipe with the faucet shut off, thereis water in the pipe putting pressure (volts) on the pipe.However, there is no flow of water (amps) since thefaucet is turned off. This is the same situation found ina home when the electrical wiring is connected to a TVor other appliance and the switch is turned off.

When the faucet is opened, water starts to flow(amps). The rate at which the water flows depends ontwo things:

1. The size of the pipe. (electricalcomparison—resistance)

2. The pressure of the water. (electricalcomparison—volts)

Once you have pressure (volts) and flow (amps)you have accomplished work (power, watts). Just likethe water that comes out of a faucet to fill a pot, wa-ter the lawn, and so on, the electricity is running theTV, VCR, lighting, and so on. Electric power is theterm used for the product of the voltage and currentin a circuit.

The length of time that you let the water flow willdetermine the gallons that are used; this is measuredby the water meter. Likewise, the length of time thepower is used is measured in watts by the electric me-ter and billed as a kilowatt-hour (1 kw � 1,000 watts).

Electricity is always trying to reach earth, which isground, through the path of least resistance. In orderto control electricity, insulators are used to isolate theenergized conductors from all sources of ground po-tential. Air is a natural insulator; once an electrical archas started the air becomes ionized which is now con-taminated. The arc will continue until it is interrupted.

Tactical Point If you discover someonewho has made an electrical contact, do not attemptto pull the victim away from the source of con-tact with your hands. The power supply shouldbe disconnected by the power company first.This may be done remotely by phoning thepower company.

If someone is working from an elevated aerialapparatus and makes contact with an energizedelectrical conductor, do not climb onto the vehi-cle to lower the injured person by using thelower controls of the aerial apparatus until thepower source has been de-energized or the aer-ial apparatus is clear of the electrical conductor.

The risk of electrical shock or contact can bereduced by:

� being able to identify electrical wires andequipment as you arrive at the incident.

� maintaining a safe working distance from anyelectrical wires or equipment.

Caution Consider all downed wires as ENER-GIZED until the utility representative confirmsthey are safe.

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THE ELECTRIC SYSTEM

GenerationElectricity generating or power plants may be largeor small, and generation is produced by severalmeans: fossil, hydro, or nuclear. Generation is pro-duced by several means: fossil, hydro, or nuclear. Ap-pearances of the power plants differ, as does theequipment in the plant. However, there are certainconditions and equipment that are somewhat com-mon to all power plants, such as the turbine, boiler,condenser, and electrical switch rooms.

The voltage that is produced by the generators isstepped or raised up through the use of power trans-formers to levels used to transmit the power by elec-trical transmission lines to locations miles from thegenerating stations. These transmission line voltagesrange from 115,000 to 500,000 volts. Transmissionline towers are usually 100 to 200 feet high and runin a straight line along utility right of ways. In mostcases, the wires with the highest voltage are those atthe tops of utility poles. Keep in mind that mostpoles also have other utility wires, such as telephoneand cable.

The electrical power is carried great distances onthese towers to large substations. An electric substa-tion performs one or more of the following functions:(1) It transforms electric energy from one voltage toanother, (2) it serves as a control center and switch-ing facility, or (3) it serves as a center for distributingelectric energy to end-use customers.

Substations can be classified into three categories:inside, outside, and a combination of both. Some arehidden from site by constructing a three-sided housearound the station.

All substations contain electrical equipment, withsome being insulating mineral oil filled, and/or pressur-ized insulating gas, such as sulfur hexafluoride (SF-6).

At these substations the voltage is stepped down,again by the use of power transformers, to 34,500volts. The 34,500-volt electrical conductors are car-ried to smaller substations on high utility poles rang-ing from 60 to 90 feet in height that run along powerright of ways.

At these smaller substations, the voltage is onceagain reduced, this time to the primary voltage level(2,400 to 19,900) volts. These conductors are carried



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on smaller utility poles (40 to 50 feet in height) alongresidential streets.

The first objective of fire personnel is to size-upand communicate as much information to the utilityas possible. Transmission substations, located withgenerating stations, are used to step-up the voltagefrom the generator; for example, 24,000 volts up tothe transmission voltage of 115,000 volts or higher.

Distribution substations are located throughoutcommunities; it steps the voltage down for distribu-tion throughout neighborhoods. Distribution voltagemay vary from 2,400 to 34,000 volts.

In order to reduce the voltage for residential use,there are transformers located on these poles that stepthe voltage down to 120 volts. This is the voltage thatis carried on the wire running from the utility pole toyour home.

As you turn on a light switch in your home theelectrical power is transmitted to the light bulb. Elec-tric utility primary (higher voltage) lines contain 10to 500 amps and their secondary (household current)lines contain 60 to 400 amps. Even though the volt-age is lower in household currents the amperage isthe same or higher than in higher voltage lines. Thereis enough amperage in secondary lines to cause seri-ous injury or a fatality if contact is made.

At the top of a utility pole is the power company’sprimary conductors. These conductors may becovered with non-insulated weather jackets or bare.The voltage in these conductors could range from2,400 volts to 19,900 volts. There could be a singlewire or as many as four at this location on the pole.

The next area down from the primary location isthe power company’s secondary conductors. Thevoltage in these conductors is usually 120 volts (res-idential areas). However, in some situations the volt-age may be as high as 480 volts (industrial areas).

Voltage in the primary lines usually is 2,400 voltsto 19,900 volts and secondary voltages range from120 volts to 480 volts (Figure I-1).

Insulators are made from high di-electric or insu-lating materials, such as glass, porcelain, polymer,plastic, and so on. Insulators provide a mechanicalmeans of clearance to prevent voltage from trackingto ground or another energized phase.

The number of insulators ganged, or joined to-gether at any given point may give you a generalindication of the voltage level. The more insulatorson a single string, generally the higher the voltage.

In order to reduce the voltage for residential use,there are transformers located on poles that step thevoltage (2,400 to 19,900) down to secondary voltage(120 to 480). Power transformers are located be-tween the primary and secondary conductors. This isthe voltage that is carried on the wire running fromthe utility pole to your home.

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Safety Firefighters should never enter a sub-station property unless accompanied by a utilityrepresentative.


Overhead electrical wires are all installed understrain. That is one of the reasons fire apparatus shouldbe staged no closer than two pole lengths to eitherside of a pole that is involved in the incident.



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Pole-mounted equipment can contain mineral in-sulating oil; if there is a spill, immediately notify theelectric utility, Figure I-4.

Extreme caution should always be taken duringstorm conditions. Downed power lines may or maynot be energized.

PRIMARYHIGH VOLTAGE

POLEIDENTIFICATION

PRIMARYFUSE

PRIMARYRISER

TELEPHONEGUY WIRE

SERVICEWIRE CUSTOMER-OWNED

SERVICE ENTRANCE

GUY WIRE

ELECTRIC METER

SECONDARYRISER

FIRE ALARM

UNDERGROUND SECONDARY CABLE UNDERGROUND PRIMARY CABLE

CABLE TVTELEPHONE

TRANSFORMEROPEN WIRESECONDARY

(LOW VOLTAGE)TRIPLEX

SECONDARY(LOW VOLTAGE)

Figure I-1 Typical distribution system.

Primary Construction

The primarydistribution lineis installed invarious ways.

REMEMBER:The primary lineoperates at 2,400to 34,500 volts.NEVER attempt tohandle this.

Primary fuses may be seen alone, or in groups of two or three,depending on what is being protected. When possible, report if thefuse(s) appear to be OPEN or CLOSED.

CAUTION: An open fuse does not always mean that electricityis off. Consider ALL wires as energized and dangerous.

SINGLE-WIRECONSTRUCTION

THREE-WIRECONSTRUCTIONWITH CROSSARM

CROSSARM

CLOSED

OPEN

Primary Fuse

Figure I-2 Primary construction.

View lookingdown the road

PRIMARY

SECONDARY

WIRES AT THESEPOSITIONS ARE

COMMUNICATIONWIRES FORTELEPHONE,FIRE ALARM,

AND CABLE TV

SIDEWALK SIDE CURB SIDE

CABLE TV ORFIRE ALARM

TELEPHONE

View lookingacross the road

Figure I-3 Pole space construction.


Identifying the type of a downed wire (power,phone, fire alarm, or cable TV) is difficult when thelines are covered with debris, ice, or snow. Again,just stay away and call for help.

Whenever there is a downed energized electricalline, a phenomenon known as “step voltage” may bepresent on the ground around the fallen power con-ductor. The downed conductor may energize theground causing a rippling effect around the point whereit is making contact with the ground and the voltagedecreases as you go out from the center of this point.

In a residential underground system, the power,gas, phone, and cable television companies all haveunderground cables in certain areas to serve their cus-tomers. The first sign that you might be in an under-ground area is that there are no utility poles around.

The voltages in the power company’s undergroundsystem are the same as their overhead systems.

Many times the power, phone, cable television,and even the gas company’s lines and cables lookalike and identification may not always be easy. Un-derground distribution lines are distribution lines thatare directly buried underground to padmount trans-former installations. The voltages can range from2,400 volts to 34,500 volts. Pad mount transformersare locked and should only be handled or opened bya utility representative.

ELECTRICAL SHOCKElectrical shock remains the greatest hazard in anelectrical contact. Besides the pain that is suffered,there is often a loss of muscle control and continuedcontact could lead to a fatal injury.

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CapacitorInstallation

TransformerInstallation

SECONDARYWIRES

TRANSFORMER

CAPACITOR

SECONDARYWIRES

FUSE

Figure I-4 Pole top utility facilities.

Secondary Wires – Low Voltage (less than 600 volts)

There are two typesof secondary wires:

• Open wire construction• Triplex (wrapped) construction

Both SECONDARY(pole-to-pole),and SERVICES(pole-to-building)appear in one ofthese forms.

TRIPLEXSECONDARY

OPEN-WIRESECONDARY

Figure I-5 Secondary wires.

Safety Protect with diking techniques any waterrunoff area that could be affected by the oil spill.Do not attempt to wash away the oil spill.

Never position yourself or an apparatus di-rectly under a pole involved in the incident.

Positioning of aerial apparatus must be con-sidered upon arrival: survey the area, locateoverhead wires, and position the apparatus,maintaining a minimum of 10 feet from all over-head conductors.

Consider all downed wires as ENERGIZED un-til the utility representative confirms they are safe.

Safety Do not take chances: call the localpower company for help. During a storm, stayaway from any downed lines.

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Electric shock will occur when a person, by con-tacting an energized conductor or other energized ob-jects, provides a path for the flow of electricity to aground. Simultaneous contact with two energizedconductors will also cause electric shock, which mayresult in serious injury or death.

When you unintentionally become part of an elec-trical circuit, current flows through your body, whichcould cause electrical burns and/or death.

The human body provides limited protection fromelectricity. The first line of defense is our skin, whichhas a high resistance to shock. Recall that resistanceis measured in “ohms,” and dry, unbroken skin canhave up to 50,000 ohms in resistance. But inside thebody, which is about 70 percent water, this resistancedrops to only 300 to 500 ohms in resistance.

To measure the effect of electricity on the body,let’s take common household voltage, 120 volts, anddivide it by a resistance factor of 40,000 ohms, whichis typical for human skin. The result of voltage di-vided by resistance is “amperes,” the amount of cur-rent which flows through human skin. Only here, theamount is small, only 3/1000 of an ampere, or 3 mil-liamps of current.

Anatomy of an Electric Shock� Resistance of the human body� Voltage/Resistance � Ampheres

Current (amps) plays a major part in the electricalshock killing factor. Voltage is important only be-cause it determines how much current will flowthrough the resistance of the human body. The cur-rent necessary to operate a 10-watt light bulb is eightto ten times than the amount that would kill the aver-age person.

� Effects of current on body1 milliamp or less—Causes no sensation and is

not felt.1 to 8 milliamps—Sensation of shock, not

painful. Individual can let go at will, as musclecontrol is not lost (5 ma is the acceptable max-imum harmless current intensity).

15 to 20 milliamps—Painful shock. Cannot letgo. Muscle control is lost.

20 to 50 milliamps—Painful. Severe muscularcontractions. Breathing is difficult.

100 to 200 milliamps—Ventricular fibrillation. Aheart condition that could result in death.

The severity of a shock determines the severity ofthe injuries received. Three factors affect the severityof a shock:

1. The amount of current passing through abody. The higher the current, the more



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potential for injury. A current as little as 50 milliamps—50/1000 of an amp—cancause death.

2. The path of the current through the body. Ashock that takes a path through one fingerand out another finger on the same hand(such as when touching the prongs on aplug) might cause only a painful, temporaryinjury. However, the same current flowingthrough the chest can cause death throughventricular fibrillation.

3. The length of time that current flowsthrough the body. Obviously, the longer theduration of a shock, the greater the potentialfor an injury.

Voltage in the primary lines usually is 2,400 to19,900 volts and secondary voltages range from 120to 480 volts.

Electric arcs or flashes are another form of anelectrical hazard. Heat generated from an electricalflash could be as high as 43,000°F. This is equivalentto the temperature on the surface of the sun.

An electrical arc will occur when there is a fault ona line, usually caused by a tool or piece of metalequipment getting across the lines. The resultingelectrical arc is similar to an arc weld.

Electrical arcs or flashes may also be the result ofa failed or faulted piece of equipment.

Electrical burns are another form of an electricalhazard that results from contact with an energizedconductor or from the heat generated from an electri-cal arc.

Firefighter Fact A 7-watt night light draws 60 milliamps of current, enough to cause ven-tricular fibrillation.

Electric utility primary (higher voltage) linescontain 10 to 500 amps and their secondary(household current) lines contain 60 to 400amps. Even though the voltage is lower inhousehold currents the amperage is the same orhigher than in higher voltage lines. There isenough amperage in secondary lines to causeserious injury or a fatality if contact is made.

Firefighter Fact A small electric drill (1⁄4 HP)draws 1,550 milliamps. This is seven timesenough current to burn you and 31 times enoughcurrent to cause your heart to go into ventricularfibrillation.


RESPONDING TOINJURIES

Anytime someone has been shocked there are anynumber of possible injuries that you may need to ad-dress: first, second, and third degree burns; brokenbones from a fall due to electrical contact; and mostseriously cardiac arrest. Once you are certain the vic-tim is not still in contact with any energized item (en-ergized fence, ladder, car, etc.), you can then treat thevictim accordingly.

When electrical shock traumatizes a nerve centerin the brain, breathing often stops, and your responseneeds to be appropriate. Time is of the essence, butdo not sacrifice yourself in the process.

It is essential to protect yourself from disease. Theskin is a natural barrier protecting us from disease,but skin that’s broken (cut, scrapes, etc.) will not pro-tect you. Wearing rubber gloves, as well as a maskand eye protection, provides protection from disease.

When checking a victim for life signs remembernot to move the victim unless he/she is in imminentdanger. If no life signs are found (breathing or apulse), treat the victim accordingly.

Current entering the body produces heat, whichcan cause damage at the entrance and exit points.Electrical burns are doubly dangerous, because tis-sues and organs beneath the skin may also be burned.

For any burn, the burning process must first bestopped. For a major burn where skin has been de-stroyed, apply dry sterile dressings.

When a powerful electrical current passes throughthe air or gas and reacts with particles in it, an intensearc can result, instantly emitting huge amounts of ra-diation and ultraviolet light. Exposed skin can be se-verely damaged, as if from an intense sunburn, aswell as the eyes. By cooling the skin additional dam-age can be reduced. Superficial skin burns are treatedlike a sunburn, with cool compress.

Talk to the victim to assure him or her that youhave things under control. Talking also helps to



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calm victims down and helps keep them from goinginto shock.

APPROACHINGENERGIZED AREAS

OverviewAs a first responder, you are most likely to be onscene before the local electric company. Safety is ex-tremely important.

Coordination between the first responders and thelocal electric company is extremely important. Thesafest way to make sure that a wire is de-energized isto have the on-scene representative from the electriccompany do the actual disconnection of the wire. Theelectric company will de-energize their facilities and

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Caution Rain gear (jackets, boots, gloves,and so on) and firemen’s turnout gear providevirtually no protection against electricity.

Electricity, because it cannot be seen, mustbe approached with extreme care. To assumethat the wire is not energized could be a deadlymistake. Always assume the wire is energizeduntil it is tested by a qualified person.

Safety Points to remember (electric contact):

� Cardiac arrest� Electrical burns are another electrical hazard

that results from contact with an energizedconductor or from the heat generated from anelectrical arc.

� Protect yourself from electric arcs or flashes,which are other forms of electrical hazard.Heat generated from an electrical flash couldbe as high as 43,000°F. This is equivalent tothe temperature on the surface of the sun.

� An electrical arc will occur when there is afault on a line, usually caused by a tool orpiece of metal equipment getting across thelines. The resulting electrical arc is similar toan arc weld.

� Electrical arcs or flashes may also be the resultof a failed or faulted piece of equipment.

Electrical shock remains the biggest hazardfrom electrical contact. Besides the pain that issuffered, there is often a loss of muscle control;continued contact could lead to a fatal injury.Electric shock will occur when a person, by con-tacting an energized conductor or other ener-gized objects, provides a path for the flow ofelectricity to a ground. Simultaneous contactwith two energized conductors will also causeelectric shock that may result in serious injury or death.

Eye damage may not show up immediately,but symptoms to look for are burning and a sen-sation of sand irritation.


advise first responders that it is safe to proceed withtheir duties.

It is very important that the local electric utility benotified of any downed wires. Even if it is suspectedthat they are not electric lines (i.e., CATV or Telco),they could be energized due to a downed wire not insight of your location. It is better to be safe than sorryby having the local electric company come out andsecure it. Always consider all downed lines to be en-ergized; contact the electric company and wait untilthey have given notice that it is safe to proceed.

Precautions When ApproachingDowned LinesA long-held misconception is that the rubber in thetires of vehicles will insulate you from electric con-tact. This is not true. Due to steel-belted radials, thetires can actually conduct electricity. The rubber pro-tection that the utility uses is tested twice a year andis designed to protect against conductivity. The samegoes with rubber fire boots or rubber rain boots. Theyare not designed to protect against electric shock.

Regardless of whether or not you know if thedowned wire is CATV, telephone, or electric, youshould always consider the wire to be live. Youshould never attempt to move it or handle it in anyway. Let utility people do the work.

Circle of SafetyWhen approaching a downed wire, great care needs tobe taken. A general rule of thumb is to maintain a min-imum distance of 30 feet away. This is known as the“circle of safety.” When in doubt, keep away and wait.

Storm ConditionsExtreme caution should always be taken duringstorm conditions. Downed power lines may or maynot be energized. Do not take chances: call the localpower company for help. During a storm, stay awayfrom any downed lines.

Identifying the type of a downed wire (power,phone, fire alarm, or cable TV) is difficult when thelines are covered with debris, ice, or snow. Again,just stay away and call for help.

Whenever there is a downed energized electricalline, a phenomenon known as “step & touch” may be

RECOGNIZING AND AVOIDING THE HAZARDS OF ELECTRIAL EQUIPMENT ■ 57

experienced while walking on the ground around thefallen power conductor. The energized conductor hasa rippling effect around the point where it is makingcontact with the ground, and the voltage decreases asyou go out from the center of this point.

VEHICLE RESCUE FROMDOWNED POWER LINES

Vehicle accidents involving utility poles are verycommon. In cases where energized lines land on thevehicle the best practice is to instruct the driver andoccupants in the vehicle to remain in the vehicle. In-struct the occupants to remain in the vehicle and waitfor the power company to arrive. Remember the cir-cle of safety. Keep at least 30 feet away and try tokeep the occupants calm.

If the vehicle is operational, instruct the driver toattempt to move the vehicle. There are a few safetypoints to remember. Keep all personnel far away un-til the car is at least 30 feet away from the downedline. One important factor to remember is wire coilmemory. This means that the wire that may be pinnedunder a tire, when released, will recoil back to whereit is connected. Be very aware of this. Keep all per-sonnel far away until the wire comes to rest and stopsmoving.

A vehicle on fire with a wire downed and peopletrapped inside can be a very dangerous situation. Thefirst responder’s initial reaction may be to rush rightin to get the fire out and help the people. This can befatal. DO NOT USE WATER! If you do this the water,hose, engine, and all personnel making physical con-tact to it can become energized. If you have a situa-tion where you have to suppress the fire, use drychemical extinguishers. Don’t forget to keep a safedistance away from the vehicle. A dry chemical usu-ally has a stream of about 15 to 20 feet. Therefore,when you’re approaching, be very aware of your sur-roundings. Use a spotter/safety officer to keep extraeyes on the situation. Remember that foam has waterin it so it, too, can become energized. If there is noone in the vehicle and it is on fire, let it burn. Protectexposures and wait for the electric company.

Once the fire is out, wait. The lines still may be en-ergized; forgetting this may result in you becoming avictim or fatality.

Caution All downed wires should be treatedas if they were energized.

Safety Persons in vehicles that may be ener-gized should be told to remain in the vehicle.

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Step PotentialAs you take each step the voltage between your feetand the ground will vary. This is known as step po-tential. The difference of voltage from one foot to an-other is enough to stop your heart. If you suspect thatyou are in an energized area there are two ways toexit the area. One is a shuffle step. Keep both feet onthe ground and shuffle your feet while maintainingcontact with the ground. Another way is to hop away.With both feet tighter, making contact at the sametime, make very short hops. Remember, water is aconductor, so be very aware of puddles and streamsof water. Avoid them at all costs, Figure I-6.

Exiting the VehicleIf trapped persons must exit the vehicle, there are afew safety tips to remember. It is critical that they donot make contact with the ground and the vehicle atthe same time. Have them open the vehicle’s doorthe widest they can. Have them stand on the doorsillsof the car and jump clear away, landing with bothfeet together. Once they are clear have them hop orshuffle-step away. The best practice is to try andkeep the people in the vehicle until the electric com-pany representative on scene tells you that the elec-tric has been de-energized.

EMERGENCIESINVOLVING ELECTRICALFACILITIES

The common use of the term “electrical fire” (Class“C”) refers to a fire involving electricity. Once the elec-tricity is disconnected the fire becomes a Class “A” or“B” fire. Small Class “C” fires can be extinguishedsafely with carbon dioxide, dry chemical, or halon ex-tinguishers. Water in the form of fog is also safe.

If utility company equipment is burning, allowingit to burn is the best course of action. Once damaged,it will be replaced, and no utility company wants re-sponders to risk their lives to save a piece of equip-ment that won’t be repaired.

Attempting to extinguish a burning pole-mountedtransformer from the ground or a ladder is mostly fu-tile, and extremely dangerous. Remember that sinceelectricity seeks a path to the ground, the hose streammay provide that path through your body.

The utility company experts will advise you onwhat to do when they arrive. They may very well di-rect you to let it burn, or wait until power is shut off

58 ■ CHAPTER I

Figure I-6 Potential gradient/step potential.

Safety Securing the site: ONLOOKERS SHOULDBE KEPT BACK.

before trying to suppress the fire. This doesn’t meanthere are not actions that can be taken to provide asafer outcome. There are usually numerous expo-sures such as trees and buildings that need to be pro-tected from fire.

Making the scene safe also includes keeping thepublic at a safe distance until the emergency is re-solved. Dealing with burning transformers, the trans-formers on utility poles, high amounts of current movethrough this structure, and both contain oil for coolingwhich can present an additional hazard if released.

Considerations forUnderground ChambersThis is a “Padmounted transformer.” Similar to util-ity poles padmounted transformers are sometimessusceptible to vehicles accidentally smashing intothem. As before, all safety precautions regarding dis-tance, step potential, and the assumption that any-thing in contact (such as the vehicle) is energizedneeds to be followed.

If fire is involved, don’t use water or foam to sup-press it—only dry chemical. If a safe distance cannotbe maintained, let the electrical fire burn and con-centrate on protecting exposures while waiting forutility company assistance. As a rule, it is less expen-sive to replace damaged equipment than to repair it,so safety is the critical issue.

Much of the electrical distribution system, espe-cially in urban areas, is underground. Any number of


environmental changes can trigger fires in the pas-sages and vaults housing electrical wires and equip-ment. If you detect signs of fire, but don’t observeany workers, vehicles, or signs of work right here,most likely no one is in the underground vault ormanhole. Don’t make any attempt to investigate fur-ther, but report what you have seen to the utility com-pany: “Those covers got blown off by explodinggases.” Once on sight, the utility company, after de-energizing the area, may need some assistance fromthe fire department to clear the smoke out from thechamber so they can enter it to make repairs.

When work is being done, as a rule, someone fromthe crew will always be aboveground. Instinct maytell you to rush down into the chamber, but don’t; youhave no idea of what may be energized, and also suf-fer from poor visibility. Make sure the utility com-pany has been notified, and wait for them tode-energize the area.

Once power has been shut off, with full protectiveequipment and breathable air supplied and moni-tored, the chamber can be entered. All the rules forconfined space entry must be followed, and extracaution has to be taken to avoid any sparking, suchas from flashlights being turned on, or metalscraped, because of the possible presence of com-bustible gases.

ELECTRICITY INBUILDING FIRES

Most electrical fires are caused by excessive heat fromwires, machines, and appliances, which have beenoverloaded or poorly insulated. When fires break outin buildings, you’re almost always exposed to ener-gized electrical wiring and power lines. Industrial fa-cilities such as this have heavy-duty electrical systemswith equipment operating at over 10,000 volts.

Residential systems mostly have 120- and 240-volt service. While much lower than industrial volt-age, it is still very dangerous. Here are someguidelines that should be followed at all times:

1. When you enter a building, you may wantto keep power on to aid you in investigatingthe fire.



DESIGN SERVICES OF



2. However, because visibility is usuallylimited, keep your palms turned inward.Why? If you come into contact with anyenergized sources, and you experiencemuscle contractions, your arms and handswill be pulled toward your body, and awayfrom the source of electricity.

3. Many firefighters believe that whenresponding to fire emergencies, the pulling ofan electric meter is an acceptable procedure.It isn’t. Meters can arc and explode.

What you want to do if possible is locate the mainbreaker box, or panel, and shut off the power fromthere. When doing so, turn away from the powersource to avoid being burned if it arcs. All electricalwires should be approached as if they were ener-gized. As shown earlier, while electrical wires areweather coated, don’t make the mistake of thinkingthat means they are insulated. Firefighter gloves arenot designed to handle energized electric lines. Don’tbe fooled into thinking it’s safe to touch the lines—it’s not. Nor is it safe to use any of your tools to cutpower lines. This attempt to de-energize power to theburning structure is extremely dangerous.

Even after you have cut power, take care not tocome in contact with machinery or appliances. Espe-cially in commercial and industrial facilities, theremay be alternate or emergency sources still supply-ing electricity. When you’re fighting any kind of firewith overhead electric lines in the area, special pre-cautions need to be taken.

Dense smoke often has carbon particles and mois-ture in it, which can become energized and produce apotentially lethal arc. This guideline also applies toany equipment and tools you are using. Make ab-solutely sure you’re keeping that safe distance beforejumping into action. Because of these dangers, onlyessential crew members should be anywhere near ve-hicles exposed to this risk.

Large scale fires involving multiple vehicles andpossible different companies and agencies compoundthe complexities in responding.

Caution You should stay well clear of theopening, because underground gases and dam-aged cables are capable of exploding.

Firefighter Fact If a ladder or bucket exten-sion needs to go over or near any power lines, aminimum safe distance of 10 feet from the ener-gized line is required by OSHA regulations.

Caution Anyone working on the vehicle mustavoid any contact with the ground because of thepossibility of electrical arcing.


When the utility company experts arrive, they willprobably cut the service wire taps on the utility pole, oropen a switch to cut power to the area. Only when theytest to make sure all sources of electrical energy are re-moved will you get an all clear to move about safely.

SUBSTATION, PLANT,AND TRANSMISSIONFIRES

An electric power substation has transmission anddistribution lines coming in and out of it. Typically,some of the components include a control building,large transformers, structures to keep the lines ele-vated, and circuit breakers. Both transformers andcircuit breakers are filled with oil, which insulates theinternal electrical components. If a fire breaks out,the high voltage levels mandate special guidelines forresponding safely.

Components of a SubstationThe transmission and distribution substation consistsof many components such as transformers, distribu-tion breakers/reclosers, power circuit breakers, volt-age regulators, reactors, capacitors, circuit switchers,switchgear, and switches that should be located andarranged in the substation yard in the most effectivemanner. One should take into account the physicalaspects of the equipment as well as the operating,safety, and maintenance requirements when design-ing the electrical layout. The following subsectionsdiscuss the various aspects of the types of substationequipment used in the subtransmission and distribu-tion substation.

Power TransformersAll substation-type power transformers are liquid-filled transformers for two or three winding oil insu-lated, three-phase outdoor power transformers. Mostall transformers that are used are of the core form,circular coil winding construction. In the core formtype of construction, the transformer windings are

surrounded by the core steel. The liquid is generallyan oil and may be flammable.

Power Circuit BreakersA power circuit breaker is a device used to open orclose an electric power circuit either during normalpower system operation or during abnormal condi-tions. Circuit breakers used are vacuum, oil filled, orinsulating gas filled.

Distribution CircuitBreakers/ReclosersInterrupting devices used in the low voltage portionof a distribution substation consist of circuit breakersand/or circuit reclosers. These devices may use vac-uum, insulating oil, or SF6 gas as the interruptingmedium. Both devices are used to protect transform-ers, circuits, and other equipment in a distributionsubstation. Both have all relaying such as reclosing,phase, and neutral relaying included in their owncontrol cabinet.

Control BuildingsControl buildings are generally deemed necessarywhen the installation of large batteries and relaying/control equipment on switchboard control panels isrequired for substation operation. Both transmis-sion and distribution substations may have controlbuildings.

The overall size of the building is determined bythe number of switchboard frames required plus theamount and size of additional equipment that must behoused within the building. Both initial and future re-quirements must be considered. The near future re-quirements are generally accommodated in the initialsize of the building, while distant future requirementsare accommodated by allowing ample space for ad-ditions to the building and laying out the building sothat future expansion is practical.

The purpose of switchboard panels or frames is toprovide a convenient and vertical surface for mount-ing and wiring control, as well as protective equip-ment for the various line exits, transformer circuits,transfer circuits, and so on located within a particularsubstation, Figures I-7 and I-8.

Under no circumstances should you attempt to en-ter the substation before the utility company expertsare on the scene. Because of the high voltage andpossibility of explosion, the danger zone is extendedmuch further: a minimum of 300 feet.

Make sure your vehicles are parked at a safe dis-tance, and be careful to avoid putting them under-

60 ■ CHAPTER I

Safety A “prefire plan” should be in place toensure that everyone is aware of the location ofpower lines and other electrical sources, so co-ordination of all parties’ actions creates a safeoutcome.


neath a power line. When utility company personnelarrive, they will provide guidance in approaching allthe structures and equipment safely. They may decideto let the equipment burn itself out, while directingfirefighters to protect exposures. Metal laddersshould not be used, only ladders made of non-conducting materials. A good guideline to followwhen inside the substation is to have no equipmentextend beyond shoulder height, because any over-head equipment may be energized.

Upon entering an area involved in an event of thisnature, the responder needs to be immediately awareof the condition and presence of overhead conduc-


tors. The overhead conductors should therefore beconsidered to be energized until proven otherwise bythe owner or utility personnel. Isolation at the pointof the emergency should not be considered as soleevidence of safety as the conductors may be fed inboth directions and therefore may be energized at anytime. The best advice is to ensure that they are iso-lated from both ends by competent and authorizedpersonnel.

Most times the fire is coming from oil in the cir-cuit breakers or transformers. Because large amountsare housed inside, it is a major concern, which re-quires special guidelines.

With equipment de-energized, the oil fires can beextinguished by using protein foam sprays and waterfog streams. Never use a solid stream of water on oilor any pools of oil, which could actually spread thefire. However, the fire may continue burning insidethe equipment. Reignition is not uncommon, and theoil may burn for an extended period of time. Contin-ued burning on and off could go on for days. Beaware that the oil vapors are also capable of explod-ing, so full PPE and safe distances from equipmentneed to be maintained.

The high concentration of carbon particles thatgive the smoke its characteristic color will also con-duct electricity from high-level energized equipmentto the ground. Further, any firefighting operationswill add to the conductivity by providing a steamcomponent in the plume. Even dry chemical particleshave been known to become conductive in high hu-midity environments by absorbing moisture andtherefore acting like “airborne mud.” Typically, thiseffect is seen between high-energy points such as ex-posed conductors or bushings on transformers.

The utility company may de-energize only the af-fected section within the substation, choosing to keepas many customers as possible in service. Therefore,they will work with you to set up a safe corridor ofoperations, which avoids areas that will remain ener-gized. Following the advice of electric power expertsproduces the safest outcome.

The equipment, which has most likely been se-verely damaged by fire, will not be repaired, and theutility company doesn’t want anyone being injured intrying to rescue it. Therefore, unless it poses a widerthreat, it will be left to burn itself out. However, if theheat is intense enough, other structural systems maycollapse, so these exposures need to be protected.

Safety Complete personal protective equip-ment for operating personnel should be manda-tory including SCBA.

Caution Another danger: because glass andceramics are excellent insulators, this equip-ment, under intense heat, can explode when wa-ter is applied.

Figure I-7 Substation control room.

Figure I-8 Substation control room.


There are other hazards to be aware of, such astoxic gases that can arise from insulation or batteries,so it is best to limit the number of people involved toonly the most essential and to confine the fire withinthe substation fence line.

Transmission towers are constructed in “right ofway” corridors that isolate them from traffic, con-struction, and trees. A large fire and smoke can extendupward far enough to present a different and danger-ous scenario. Smoke contains carbon and carbon is aconductor of electricity. At a distance of approxi-mately 6 feet, with enough heat, the particles of smokecan trigger arcing, with an intense burst of electricalenergy flashing to the ground. Therefore, when yourecognize these conditions forming, put at least a hun-dred feet of distance between you and the fire.

Generating stations such as these that burn fossilfuels to produce electricity rely on you to bring fireemergencies under control. If such a facility is inyour coverage area, you need to be meeting with theutility company to discuss emergency preparedness

to deal with possible dangers associated with the gen-eration plant.

Inside these generating stations you could en-counter hazards from water, steam, natural gas, andtoxic substances. If a fire starts at a generating plant,you will be met by a utility company specialist. Thisperson will work with you to make sure that all of thecontingencies you have discussed for this situationare addressed so that the safest course of action canbe followed in a dangerous situation.

Power plants use some of the same equipment asfound in a substation. The same guidelines apply incarrying tools and equipment: be sure to keep every-thing at shoulder height or below.

62 ■ CHAPTER I

Safety Prefire plans include plant layout:know where chemical and oil tanks are located,as well as hydrant and fire pump locations.

Electric Dos and Don’tsDO DON’T

� Treat all utility lines as high voltage.

� Look for overhead lines when arriving atemergency scenes.

� Check for and avoid utility lines on theground, in trees, or on vehicles.

� Notify the electric utility when there aredowned lines or other electrical problems.

� Beware of step voltage and keep at least 30feet away from downed lines.

� Have occupants remain in vehicles that are incontact with downed lines until the “all clear”is given by the electric utility.

� Instruct occupants of energized vehicles tojump clear and hop or shuffle away from theirvehicles.

� When utility electrical equipment is on fire,let it burn, protect the exposures, andcontact the utility company.

� Park emergency vehicles under or nearoverhead lines.

� Touch downed lines, even with gloves, sticks,or tools.

� Assume the electric utility has already beennotified when you encounter downed lines.

� Allow aerial device equipment such as laddertrucks to approach closer than 10 feet to anoverhead utility line.

� Pull electric meters or cut service lines.

� Apply water or foam to burning electricalequipment.

� Enter electric utility substations without theOK from the electric company.

� Enter underground vaults or manholes untilthe “all clear” is given by the electric utility.


DEFINITIONSAC Voltage: Alternating Current changes

at a rate of 60 times a second, majorsource is generators.

Circuit: A conductor or system ofconductors through which an electriccurrent is intended to flow.

Communication Lines: The conductorsand their supporting structures fortelephone, telegraph, railroad signal,data, clock, fire, police alarm,community television antenna andother systems that are used for publicor private signal or communicationservice.

Conductor: A material, usually in theform of a wire or cable suitable forcarrying an electrical current.

Current: The flow of electricity througha conductor.

DC Voltage: Direct current steadyconsistent voltage, major source isbatteries.

Direct Contact: When any part of thebody touches or contacts an energizedconductor or an energized piece ofelectrical equipment.

Ground (noun): A conductiveconnection by which an electric circuitor equipment is connected to ground.


Ground (verb): The connecting of anelectric circuit or equipment to ground.

High Voltage: Greater than 600 volts.Indirect Contact: When any part of the

body touches any object that is in contactwith an energized electric conductor or anenergized piece of electrical equipment(EXAMPLES: Tree limbs, tools,equipment, trucks, etc.)

Insulated: Separated from otherconducting surfaces by a dielectricsubstance offering a high resistance tothe passage of current.

Low Voltage: 600 volts or lessManhole: A subsurface enclosure which

personnel may enter and is used for thepurpose of installing, operating andmaintaining submersible equipmentand or cables.

Step & Touch Potential: The areaaround an energized conductor that isin contact with the ground and how farthe voltage field extends from thecontact point.

Resistance: The opposition to the flow ofelectricity measure in ohms.

Voltage: The speed that electricity flowsthrough power lines.

REVIEW QUESTIONS1. What is the minimum electrical voltage that

can kill a human being?2. Electricity will always take the shortest path to

ground; if you get between the electrical sourceand the ground you would become a conductorand be __________.

3. What is the classification for a fire in energizedelectrical equipment?

4. What is the OSHA Standard that groundladders and aerial ladders should be kept fromhigh-voltage lines or equipment.

5. What is the only way to make sure that a wireis de-energized?


RECOGNIZING AND OF ELECTRICAL EQUIPMENT · When you look at an electric wire that could be...

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