Firefighter’s guide to facing electrical hazards

Firefighter’s Electrical Safety Guide

This booklet is created by BC Hydro for firefighters in B.C. It’s meant to inform and educate about the

hazards of the electrical power system, so you can protect yourself and the public in the event of a fire.

The most important thing to do when you respond to a fire or situation involving electricity is to call BC Hydro first.

Properly trained and equipped BC Hydro representatives will respond to the situation as quickly and

safely as possible.

Copyright © 2017 British Columbia Hydro and Power Authority.

Fourth Edition

All rights reserved. No part of this publication may be reproduced in any form, by any photographic, electronic, mechanical or other means, or used in any

information storage and retrieval system, without prior, written permission of BC Hydro.

Firefighter’s Electrical Safety Guide Page 1

Table of contents

Understanding basic electricity. ...........................................................................................................3

B.C.’s electrical power system.............................................................................................................. 7

Dealing with downed power lines ...................................................................................................... 11

The underground distribution system ................................................................................................. 21

Fighting structural fires ..................................................................................................................... 27

Fighting fires at substations and generating stations ............................................................................ 33

Fighting fires at outdoor substations .................................................................................................. 38

Fighting fires on transmission lines and rights-of-way. .......................................................................40

Firefighter’s Electrical Safety GuidePage 2


Understanding basic electricityVoltage, current, resistanceYou can compare what you already know about water with electricity. The difference is that you can see

and feel water, but you can’t normally see electricity, and you can be killed by it if you get too close.

Voltage - Current - ResistanceFACTOR ELECTRICITY WATER

Pressure Voltage (Volts) Pounds per square

inch (psi)

Rate of flow Current (Amperes) Gallons per minute

(GPM)

Resistance Resistance (Ohms) Pressure drop per

length of hose due

to friction loss

VOLTAGE - The force (like water pressure) that causes electricity to flow through the wire or conductor,

measured in volts, expressed as V.

CURRENT - The rate of flow or how much (like the rate of water flow in a fire hose), measured in amperes

or amps.

RESISTANCE - The diameter and length of the wire affecting the amount of electrical flow, measured in

ohms (similar to the effect of friction on the flow of water in a hose, i.e. it flows more freely

in a large hose than a small one).


Electrical conductionElectrical conduction is the process by which electricity is transmitted through a material when there’s a

difference of electrical potential from one part of the substance to another. Some materials don’t allow

electricity to flow through them, or they provide high resistance to electrical flow. These are called non-

conductors—or insulators—and are basically very high resistance materials that would require a very high

voltage, or pressure, to push any electricity through.

Insulators Conductors

0 Porcelain 0 Human body

0 Glass 0 Metal

0 Specific types of fibreglass 0 Water

0 Plastic 0 Wood

0 Inspected and tested rubber used as protective equipment

0 Rope

Fibreglass can be an insulator, but beware! 0 There are lots of fibreglass poles—you may carry some of them as equipment. You may be tempted to use

one of these to do a rescue, thinking that it’s non-conductive—perhaps to lift a power line off a vehicle to

get the occupants out. DON’T DO IT! Stay back!

0 Consider that fibreglass is conductive and that using the fiberglass pole could cause you to become a second

victim. The same applies to plastic and most rubber materials.

0 Tires generally contain steel belts and carbon—both are highly conductive. Don’t consider tires a safe

insulator; only natural rubber that’s tested for dielectric qualities can be considered an insulator.

Firefighters’ boots will not insulate you from electrical hazards. Consider everything conductive and stay

back and wait until a BC Hydro representative arrives and makes the site safe.

The amount of current

a person can withstand

depends on factors such

as the amount of time

the person is exposed

or in contact with the

electrical source (the

higher the current, the

less time the person can

survive) and the path the

hazardous energy takes

when passing through the

body (a path through the

heart or brain is more life

threatening than through

other parts). Electricity will

take all paths to ground.

Page 5Firefighter’s Electrical Safety Guide

Hazardous energy passing through the body can cause a variety of injuries and the following are important

considerations:

0 Electrical injuries which require special treatment are outlined in the “How to Treat Electrical Injuries”

pamphlet and poster material that was developed for medical professionals by the BC Professional

Firefighters’ Burn Unit.

0 It’s important to note that with high voltage contacts there are usually entry and exit burns on the body

and damage is visible, whereas damage is not always visible on low voltage contacts.

0 In the case of cardiac arrest, apply CPR and/or defibrillation in the first few minutes—this provides the

best chance of survival.

0 A large electric arc produces both intense heat causing severe burns, and ultraviolet rays. Both are

dangerous and the ultraviolet exposure can cause serious eye damage.

0 Any electric shock victim should be hospitalized for observation regardless of any lack of symptoms as

some symptoms can appear hours or days later.

Effects on the body

Ventricular fibrillationand/or cardiac arrest

Involuntarymuscle reaction

Damaged limbsrequiring amputation

Stoppage ofbreathing

Electricalburns

Psychological trauma,hearing damage,vision loss

Ground gradient ripple effectElectricity seeks all paths to the ground, and when it reaches ground, it spreads out like ripples in a pool of water.

This is known as ground gradient.

Voltage is very high at the point where the electricity makes contact with the ground and decreases as it gets

further from the point of contact.

For example, when two water containers are joined by a hose, any pressure differences forces a flow from one to

the other. The same thing may cause electricity to flow between the feet and the body when there is a difference

in voltage between each foot.

A tree, an un-insulated boom on a truck, or a broken power line that’s fallen to the ground or lands on a vehicle,

can bring undetermined voltage to the ground.

The decrease in voltage depends on the composition of the ground, such as the moisture and objects that

are in the ground.

Step potential“Step potential” has the potential for making you part of the circuit.

It is the hazard created when you step across a difference in voltage created by ground gradient as you move

toward or away from the electrical source. Electricity will flow between the feet and through the body —

called “step potential” — which in this example, could be lethal.


You should stay back from the

contact point at least 10 metres

(33 feet) and if you must move, shuffle

away (heels do not pass toes).

3,500 V 2,000 VContact point


ABC BUSINESS CORP

CAUTIONCAUTIONCAUTIONCAUTION


There are three parts to a typical electrical system:

1. Power generation

2. Transmission

3. Distribution

0 In B.C., the majority of our electrical energy comes from the power of falling water at hydroelectric dams.

0 From the dam the electricity is carried throughout the province by our transmission and distribution system.

0 The transmission lines come into our cities on wood structures or steel towers from generating plants

at voltages varying from 60,000 to 500,000 volts to local substations for further distribution.

0 From the substation the primary distribution voltages may range from 4,000 to 35,000 volts between

phases or between any two conductors.

0 Distribution transformers reduce the voltage to 120/240 volts for residential areas and up to 347/600

volts for commercial, light industrial and street lighting.

B.C.’s electrical power systemPower

generation

Substation Hydro dam

Step up transformer

Transmission 60,000 -

500,000 V

Distribution 4,000 - 35,000 V

347/600 V

120/240 V

24

Typical overhead service

24

Typical underground service

0 Normal primary voltages on city distribution

lines can vary from 4,000 to 35,000 volts.

0 Power lines are attached to insulators to

prevent the flow of electricity to ground.

0 Distribution transformers reduce

the voltage from primary to

secondary voltages between

120 and 240V for residential

and between 347 and 600V for

commercial, light industrial and

street lighting.

0 An underground

service is similar to an

overhead service with

the transformer(s)

housed in kiosks or pad

mounted transformers

which are fed by

buried cables.


Meter

Un-insulatedsecondary

distribution line120/240 V

Distributiontransformer

Primarydistribution line

4,000 -35,000 V

Secondarycable

120/240 V

4,000 -35,000 V

Primarycable

4,000 -35,000 V

Transformer

Overheadpower

supply tounderground

service Street light600 V

Street light cable

Servicecable

Service drop


24

24

Typical distribution 120/240 volts SERVING RESIDENTIAL AND SMALL BUSINESSES REQUIRING LIGHTING ONLY

0 The normal primary voltages on

distribution lines varies between

4,000 and 35,000 volts.

0 The above configuration reduces the

voltage from primary to secondary

voltages of 120/240.

0 Low voltage goes to the bottom two

lines on the rack of wires below the

transformers with the top conductor

being the neutral.

0 If present, telephone and cable lines are located

about 1 metre (3 feet) lower and normally don’t

carry line voltage.

0 Where required, distribution poles will have

either a single transformer for customers requiring

lighting and household appliances only, or three

transformers for customers requiring three phase

power—for such equipment as elevators, air

conditioning or industrial motors.

Primarylines

4,000or

35,000 V

Secondarylines

Telephoneand cable

Crossarm

Pininsulators

Servicedrop

Fusedcutout

Transformer


75 75

75

Typical three phase power pole 120/208 volts or 347/600 volts SERVING SMALL COMMERCIAL AND INDUSTRIAL BUSINESS

A typical three-phase power bank system has

three primary or high voltage lines (bare wires

without insulation) attached to pin insulators on

the top crossarm of a wooden pole, or standoff

insulators on concrete poles.

0 The normal primary voltages on distribution

lines vary between 4,000 and 35,000 volts.

0 If present, telephone and cable lines are

located about one metre (three feet) lower

and normally don’t carry line voltage.

Telephoneand

cable

Fusedcutout

Crossarm

Primarydrop leads

Transformers

Primaryhigh voltage

lines

Threephase low

voltagelines


Power lines can be brought down by storms, falling trees, motor vehicle accidents, mechanical failures,

and other incidents.

What to do at the scene of a downed power line0 If you encounter trees on power lines, keep your

vehicle or equipment at least 10 metres back.

0 Stay a minimum of one span length (the distance

between two poles), or more if possible, from the

spot where the line makes contact with the ground

and stay on the opposite side of the road. Examine

the whole site before you exit the vehicle, in particular look for any downed wires and wires that may be

on the crossarm instead of the insulators.

0 Your main role is to keep the public back at least 10 metres from a distribution line (33 metres from a

transmission line).

0 Assume that any downed wire is energized and treat it as such until you’ve been told face-to-face by a

BC Hydro representative that it is de-energized and grounded.

0 If the power line overhead is arcing, the conductor could break and fall to the ground or whiplash toward

you. Tell BC Hydro that it is arcing and keep a good, safe distance away.

0 Be aware that a fallen energized wire will not necessarily arc or spark, so it may look safe when it’s not.

0 Consider that both sides of the broken wire could be energized.

0 When there is a downed power line, there is a risk of injury to firefighters and the public due to step and

touch potential.

0 Power may be restored to the downed line at any time due to automatic reclosing equipment which is

designed to restore power to customers when there is a fault such as a temporary branch on the line.

Drooping or hanging wires, or broken or leaning

poles could come down at any time and easily

extend the hazard beyond the immediate area.

Dealing with downed power lines

Keep back minimum 10 m/33 ft if

you see a tree on power lines.

Approach the site safelyIt’s critical that you approach an electrically hazardous site cautiously and systematically.

0 The ground gradient shown at the pole is a reminder that there could be voltage to ground at that location

as well as from the downed wire.

0 Park your vehicle at least 10 metres (33 feet) from a fallen distribution line, and 33 metres (100 feet) from a

fallen transmission line.

• Keep everyone back from the scene at least 10 metres (33 feet) from a distribution line, and 33 metres

(100 feet) from a transmission line.

• Never park your vehicle under overhead lines that have been damaged.

• The downed wire may or may not be sparking/arcing.

The illustration below shows the poles quite close together to fit them into the drawing. In reality, they’re

usually about a few hundred feet apart.


Keep backminimum 10 m/33 ft

Do not parkunder lines

Examine suroundingsbefore exiting the vehicle


Don’t become a victimIf you’re involved in a rescue, resist the temptation to approach a

potential electrical contact victim.

0 You’ll quickly become the “second victim”.

0 Remember, the victim and the ground are

energized and the step potential rules apply.

0 Stay back at least 10 metres or 33 feet.

0 Chances are you wouldn’t even reach

the victim before being overcome

yourself by step potential.

0 Notify BC Hydro immediately, and make

sure they know the situation’s urgency.

Size up the hazardsAs you get closer to the scene, determine the scope of the hazards.

0 Be aware of leaning or broken poles or broken guy wires.

• These can cause the lines to sag.

• Check several spans along the line in both directions.

• Do not go underneath leaning poles.

• Look around for the exact location of all wire ends.

0 The ends may be on the ground or one could be hanging in the air that someone could walk into, especially

if visibility is poor.

0 Look up as a wire could be knocked off an insulator and resting on the crossarm.

• If the wire is on the crossarm, the pole can be energized.

• You should guard this pole accordingly, with its dangerous ground gradient or worse, a step and touch

potential hazard may exist.

• This expands the hazard scene from the broken wire location, to possibly hundreds of feet away to the

pole where the wire is on the crossarm. This is why you need to always keep the big picture in mind.

0 Both ends of a broken wire should be considered to be energized.

Leaningpole

Sagging wires

Look for wires restingon the crossarm

Keep backminimum 10 m/33 ft

Know what’s undergroundIf you’re attending an incident that requires working with any equipment that’s buried in the ground, like a

hydrant, it’s important that you know what’s underground.

0 Where’s the supply for the hydrant?

0 What other services are buried that may conduct electricity to where you’re working?

Electricity flows in all directions through the ground. The surface ground gradient we encounter when walking

is just one part of that.

0 This means that hazardous energy can reach conductive underground piping which can transmit electrical

current over wide areas.

0 Each conductor also produces its own gradient around it.

0 Underground piping can be damaged by the current, causing water or gas leaks.

• I f you suddenly smell gas in a downed wire situation, take it seriously.

Page 14 Firefighter’s Electrical Safety Guide

Do not touch a fire hydrant if there’s nearby underground electric conductor

Keep onlookers backKeep onlookers back, and use “Danger Electrical Hazard Do Not Cross” tape to cordon off the area at least

10 metres (33 feet) around a distribution line, and 33 metres (100 feet) around a transmission line from

broken or sagging wires or other objects which could conduct electricity.

0 Live wires in contact with objects on the ground or in the air may burn through.

0 This can cause the conductor to curl up or roll along the ground and move the ground gradient closer

to onlookers.

0 Note that the conductor may curl or roll up because the steel core in some aluminum conductors retains

a “reel memory” from being manufactured and wound on a reel.


Treat all conductorsas energized.

Keep public backminimum 10 m/33 ft

Wire contacting objectcan burn through.

Power lines can be energized from both endsA downed power line may be energized from both directions. Because of this, it’s important to treat

both ends as live.

0 In this situation, both the vehicle and the fence may be energized, each from different ends of the

power line.

0 This could extend the hazard around several blocks, a serious logistics problem. Take the situation

of a school yard for example:

• From inside the school it’s relatively easy to have the teachers lock down the school and keep

everyone inside.

• Outside, you have the public coming from all directions.


Downed wires and anything they

contact may be energized

Vehicle maybe energized

Fence maybe energized

Vehicle accidentsYou may attend a scene where a line is in contact with a vehicle. The line could be underneath the vehicle,

or on top of it.

0 After responding vehicles are positioned safely, conduct an outer circle check.

0 This includes inspecting the power pole insulators to determine if lines have fallen from their insulator supports.

Keep back the minimum 10 metres (33 feet) from the potentially energized area and secure the hazard with

“Danger Electrical Hazard Do Not Cross” tape to keep everyone back from the scene.

0 Do not approach the vehicle until a BC Hydro representative arrives on site to ensure that the area is

de-energized and grounded.

If the occupant can safely drive the vehicle without increasing the hazard, have them drive at least 10 metres

(33 feet) clear of the wire before anyone approaches the vehicle.

0 Consider that the wire may be hooked to the vehicle and the reaction of the wire.

If the vehicle can’t be driven clear, tell the occupants to stay calm and to remain where they are.

0 Keep them from any step and touch potential situations.

0 Normally this is the safest position for them until the line is de-energized and grounded.


If vehicle cannot be moved, and there’s no fire, occupants should remain inside.

If safe, vehicle should be driven clearof the wires a minimum of 10 m/33 ft


Evacuating the vehicleExiting a vehicle is a very high risk event. Motor vehicle accidents involving power lines can be fatal if a victim

contacts the vehicle and the ground at the same time.

In this scenario, the occupant is not injured but the vehicle has caught fire, which can’t readily be extinguished

from a safe distance.

Use your professional judgement to determine if the occupant(s):

0 Must get away from the vehicle

0 is capable of getting out of the vehicle

0 is able to understand and follow instructions.

If you deem the occupant(s) ready to leave the vehicle, give clear instructions for how to get to safety.

Jumping clear can be very dangerous because it’s easy to bridge across a voltage difference if the victim

stumbles and falls. This would cause serious or fatal injury.

0 Have the victim keep their feet together as they jump.

0 They must not contact the vehicle and the ground at the same time with any part of their bodies

or clothing.

0 They must land with both feet together and not stumble.

0 Once clear of the vehicle, they must slide one foot as close as comfortably possible to the other foot as

they shuffle, and not to allow the heel of one foot to move beyond the toe of the other to a minimum of

10 metres or 33 feet from the vehicle.

0 Avoid hopping as there is a greater chance of falling which could increase the step potential hazard.

0 Because so many things can go wrong, exiting the vehicle should be a last resort!

If there are signs of fire,jump clear of the vehicle.

Shuffle, heels do notpass toes, and don’t fall.

Fog sprayIf fire suppression is necessary at any incident involving the energized electrical system, apply water only

with a fog spray. Using a straight stream could conduct electricity back to the nozzle.

Water pressure must be maintained at 100 psi at the nozzle with a 30 degree fog pattern, from a distance of

at least 10 metres (33 feet).

0 Most fog nozzles need an inlet pressure of 100 psi to form an adequate fog discharge. At this pressure,

a fog discharge can be used on a wide range of electrical voltages.

0 Be aware of the ground gradient, especially if the ground is wet.

0 You must not use foam or surfacant until equipment is de-energized and grounded. Foam increases the

conductivity and is not appropriate for use on energized equipment.

If you’re attending a pole fire, remember to establish a safety perimeter.

0 Keep back a minimum of 10 metres or 33 feet from the point of contact, protect exposures, and keep an

eye on the fire. Many times these fires will self-extinguish.

0 Always be aware that burning transformers can explode which can result in an oil spill or gravity fed fire

and can significantly expand the fire hazard area.


Keep back minimum 10 m/33 ftfrom point of contact

Minimum 100+ psi 300 fog nozzle

Do not use foam


BackfeedWhen a broken line results in a downstream power outage, there’s always potential for the main line to become

re-energized upstream of the break, or it could remain energized—but the most dangerous example of

unexpected re-energization is backfeed.

0 Someone using a portable AC power generator or solar panels can re-energize the downstream side

of the line.

0 The generator and/or solar power energizes the building’s electrical wiring which is connected to

the distribution line.

0 Most users don’t think to turn off the power panel breaker or disconnect the switch in the building,

thereby allowing the alternative energy to travel back through the service drop, then through the

electrical transformer which now converts the low voltage into high voltage.

0 The distribution line is now energized with the same high voltage it had before the outage, and is

still dangerous.

• If you’re in a blacked out area and there’s evidence of electricity in use (lights on), be aware of

possible backfeed.

Main power source, wait for BC Hydroto de-energize and ground.Cause of

power outageSolarpanel

Backfeedfrom

portablegenerator


Typical above ground transformers

AB

H1A

H1B

DC

E

AB

H1A

H1B

DC

E

Kiosks are metal boxes installed at ground level.

0 They protect the above ground portions of

the underground electrical installations.

0 Voltage in kiosks can vary. They can be:

• Up to 35,000 volts on the primary side; and,

• Either 120/240 volts or 347/600 volts on the

secondary side.

0 If you come across a kiosk that’s been tampered with or damaged in any way, stay back a minimum

of 10 metres (33 feet), and call BC Hydro immediately.

• There may be damage to the structure, causing the outside case to become energized.

• Give the location and the kiosk number on the unit.

Very large areas of B.C. are served with a network of underground wires, which are brought to the

surface to various types of transformers and switching kiosks. This equipment has the same potential

for injury as overhead lines if it is moved or damaged.

The underground distribution system


Keep back minimum10 m/33 ft

Warn occupants tostay in vehicle

Primary voltage(4,000 - 35,000 V)

Vehicle contactIf a vehicle comes into contact with a kiosk, it’s possible the outer casing has been moved by the impact and

is making contact with the high-voltage equipment inside.

0 Treat this situation the same as you would downed power lines.

0 Call BC Hydro immediately.

• Stay back at least 10 metres (33 feet), and remember the hazards of step and touch potential.

• Do not approach or touch the kiosk or anything that may be touching it.

• Make sure the occupant stays in the vehicle until help arrives, unless there is a risk of fire.

0 After a vehicle accident, treat transformer kiosks as energized and extremely dangerous. Call BC Hydro

immediately.

Underground cable contactHere are two possible underground conductor contact situations. In both scenarios, when you arrive you may

not know if it’s an electrical scene. You need to decide if you can go in safely and assist this person.

0 Ask lots of questions. Construction workers may be able to say if there’s electricity around. They may be

able to gather more site information for you as well.

0 If it appears that electricity is not involved and that it may be a medical situation, you must still be very

cautious about moving in.

0 If you have any suspicion that it involves electricity, stay back a minimum 10 metres (33 feet) and treat it

just like an overhead situation.

0 Call BC Hydro immediately.


0 Now on the ground, the worker is in a step potential situation and current is passing through his body.

0 Rescue has step and touch potential hazards.

In the first scenario, a backhoe operator has struck and broken an underground electrical conductor.

0 The victim was touching the backhoe when

this happened.

0 Current went through the backhoe

and through the victim because of

touch potential.

0 The ground gradient may

exist if the conductor is still

touching the ground or the

backhoe. This can cause

rescue conditions with

step potential hazard.

0 Operator rescue follows

the same procedure as

the vehicle occupant

rescue we saw earlier.

0 Keep back a minimum of 10 metres (33 feet).

0 Don’t touch anyone or anything that is in contact with electricity and call BC Hydro immediately.

0 If you respond to a call involving a person injured or unconscious around digging equipment or

excavations, use extreme caution.

In the second scenario, a worker using a pickaxe has severed an underground conductor.

0 Current went directly through the tool and the worker.

Keep back aminimum 10 m/33 ft

Call dispatch to contactBC Hydro imediately


Typical manholes

0 Underground service in industrial or urban areas has high voltage transmission and distribution wires running

through cable ducts to vaults located under the pavement.

0 Transmission vaults may have a round manhole cover stating “BC HYDRO”, “BCHA”, “BCER”, or “LADWP”.

Typical transmission voltages in manholes are 60 kV or 230 kV. Most underground transmission cables are

pressurized and oil-insulated, and fires involving these cables are typically oil fires.

0 Distribution vaults contain cables under 60 kV and may have a round manhole cover stating “BC HYDRO”,

“BCHA” or “BCER”. Typical distribution voltages are the same as overhead wires (e.g. 12 kV or 25 kV).

0 Manholes can contain wires, splices, oil-insulated switches and other equipment.

0 Often there are several cables running through a manhole. When one cable has faulted, the others may

remain energized. They are also more likely to fault, due to damage from the first cable fault.

0 Some manhole covers are bolted down, but all manhole covers can become dislodged and must be considered

a safety hazard. Manhole covers have been known to be thrown up to 21 metres (70 feet) into the air.

Typical underground vaultsThere are two types of underground vaults: cable manholes and transformer vaults. Treat manholes and vaults

as confined spaces. Do not enter.

Typical transformer vaults

0 Transformer vaults contain mineral oil-insulated transformers and switch gear for circuits. Some of this

equipment may be exposed.

0 Electrical failure of any energized equipment may result in an explosion or fire.

0 This could damage wire insulation and result in all conductive materials within the vault becoming energized.

Manhole or vault fire/explosion0 Manhole fires often start as the result of a short circuit in a splice. Arc flash may take place and the

insulation on the cable may burn, causing smoke. In the illustrated scenario, smoke is discharging from

an electrical underground cable manhole or vault that has been blown out of the ground.

0 It is likely that a cable, transformer, or electrical switch has failed and the initial arc blast has blown out

at the cover and started a fire.


Do not approach a manhole after a fire or explosion. It may explode again.

Keep public backminimum 33 m/100 ft


Initial response

0 Contact BC Hydro immediately.

0 Locate apparatus upwind from the fire.

0 Keep everyone including all emergency personnel and the public at least 33 metres (100 feet) from the

manhole until a BC Hydro worker is on site.

• Be aware that the manhole may still contain energized high voltage cables and could experience

another fault at any time.

0 Evacuate any buildings or structures downwind of the manhole that may be exposed to smoke entering

air intakes, windows, doors and other openings.

0 Remember: Manhole covers have been known to be thrown up to 21 metres (70 feet) into the air.

If the manhole cover is in place, do not approach the manhole or remove the manhole cover, and

stand by until the fire burns out. Removing manhole covers from a vault or manhole that is involved

in the fire can cause the manhole cover to become a projectile at any time during a fire incident.

0 Note that about 80 manholes in Vancouver are equipped with a dry deluge system. If the manhole has

a dry deluge system the firefighters should follow their specific training procedures for this system.

Fire suppression

0 Do not initiate fire suppression until a BC Hydro worker is on site.

0 Once a BC Hydro worker is on site, set up a unified incident command system and formulate an incident

specific response plan.

How to respond to a fire or explosion in a manhole


Fighting structural fires

24







Most structures in a community have an electrical service or power supply, so firefighters often face potential

electrical hazards when they fight fires involving structures.

0 With structural fires, overhead power lines present one of the most significant electrical hazards to firefighters.

0 Direct body contact with energized wires, or contact through equipment, presents the greatest potential

for injury or death.

0 Observing a few basic rules can help you avoid injury or death.

Commercial Substation Substationhigh voltage

Transformer

Smallindustry Schools

Stores Homes

Largeindustry


Limits of approachWorkSafeBC regulations specify the minimum safe distances, the limits of approach, which must be maintained by

any worker, work, tool, machine, equipment or material when working near a power line. More information can be

found on the WorkSafeBC website.

BC Hydro recommends that first responders maintain a safe distance of 10 metres, or more in some circumstances,

to allow for:

0 Unknown voltages

0 Inadvertent movement

0 Uncontrolled situations

Maintaining safe distances from power linesWhen entering a situation that could involve a risk to electrical hazards and you do not know the voltage you’re

dealing with, stay back at least 10 metres (33 feet) and contact a BC Hydro representative to verify the voltage.

0 For manhole incidents, stay back at least 33 metres (100 feet) due to the risk of another fault and the danger of

the manhole cover becoming displaced.

0 For incidents near high voltage power lines or substations, also increase the distance to 33 metres (100 feet).

0 Depending on the voltage, the minimum distance that you must maintain from the hazard will be different.

0 The most common situations you will encounter—those involving small industry, schools, stores and homes—

may be fed by primary voltages of up to 60,000 volts.

0 If you’re working in an area with large transmission structures on a power line right-of-way, your safe distance

will have to increase as the voltage increases.

0 Only a BC Hydro representative can identify the voltage of the equipment.

0 In any uncontrolled situation you should keep in mind that there may be unexpected movement in the wire, for

mechanical or electrical reasons.

0 You must make sure you have enough room for a full range of motion without encroaching on the limits of

approach, including any equipment or tools.

0 Power may arc from energized equipment without physical contact.

Aerial ladder setupBefore you operate aerial equipment, make sure you know where all power lines are located – look ahead,

behind, below and above. When you move equipment or materials into the area, restrict entry to allow only

the necessary workers.

0 If you don’t know the voltage you are dealing with, use a spotter (safety watcher) to make sure you keep

equipment ladder back at least 10 metres (33 feet) from power lines. Your spotter must also stay at least

10 metres (33 feet) from the aerial equipment when you work in close proximity to power lines.

0 Safety watcher must always keep within visual and audible range of equipment operator.

0 Whenever moving the aerial ladder make sure no one gets off the truck or stands on the ground and

contacts the truck. Anyone on the ground touching the truck will be in a touch potential situation. In

circumstances where the aerial equipment operator must be on the ground, they must be standing on a

grounding mat which must be bonded to the fire truck or at the very least a safety watcher must be in place.

0 When a qualified BC Hydro representative arrives on site, they will verify the voltage and de-energize and

ground the line if necessary.

0 In addition to possibly damaging equipment and materials, dropping equipment could accidentally violate

the limits of approach by providing a conductor from inside the limits of approach to you or your equipment.

Be extra cautious when visibility is limited. Do not drop equipment.


10 m distance fromladder to power lines

Use safety watcher


Power disconnect 0 Conditions may require turning the power off to remove electrical hazards, most likely during cleanup

after a fire.

0 Contact BC Hydro to disconnect the power. They can cut the service drop at the pole or disconnect it

properly if it’s underground.

0 If the response from BC Hydro involves delays, you may be able to shut off the power to the customer’s

equipment at their main electrical panel.

• Keep in mind that if you’re disconnecting after a fire, the switch may be damaged.

• Always face away from the panel and, when applicable, use the back of your hand to trip the main switch.

• If 120/240 volts at a residence is connected firefighters can attack this fire while keeping 10 metres

away from the service so that if it drops it will not fall onto or near a firefighter.

• This helps you minimize injury from any arcing that may occur—and any involuntary movement you

may experience will force your hand toward you rather than causing it to clamp onto the switch.

Caution: Main switch may not shut off power, i.e. grow-openergy diversion. It could fault to ground causing potential injuries.


0 Use extreme caution when you use ladders and equipment around the service drop.

• You must maintain at least 1 metre (3 feet) from the service drop if you are going on the roof, so

place your ladder at least 2 metres (6 feet) away at the roof to account for inadvertent movement.

The conductors are not considered to be insulated and the plastic coating is only considered as

“weatherproofing”. You should never touch them. If they rub against something metal, like a

gutter, the metal may become energized.

• Make sure you look up and pay attention to all surrounding conditions, including nearby high

voltage lines.

• Often fires can be attacked even though the residential or commercial service drop is still

connected and energized.

0 If the service drop has a bare spot where the taping has worn off, if it rubs against something metal,

like a gutter, the metal becomes energized.

0 The most important thing to remember about low voltage service drops is to not touch them.

Maintain minimum distance of 1 m/3 ft

PRIVATE PROPERTY

NOTRESPASSING

Keep back: do not enter

grow-op building until

BC Hydro representative

disconnects the power.

Page 32 Firefighter’s Electrical Safety Guide

Grow-op exterior If you’re called to a fire at a suspected grow operation, use your standard procedures to confirm whether or not

it is, while keeping an appropriate distance from the building.

If the grow-op is confirmed:

0 Do not approach or enter the building.

0 Call BC Hydro

A qualified BC Hydro representative will be sent to the scene to disconnect the electrical supply wires to

de-energize the building service.

Grow-op interiorOnce the grow-op building is

de-energized, you can enter.

0 Usually, you’ll be working

in poor visibility.

0 Even though the building is de-energized,

the tangle of electrical wiring is still a

dangerous hazard that could trap you long

enough to use up your oxygen supply.

0 Meanwhile, if there are visible

open flames, attempt to extinguish

them with water, using a minimum

30 degree nozzle at 100 psi.

0 Keep back 10 metres (33 feet) from

the building.

0 It is only safe to move closer than

10 metres (33 feet) when the

BC Hydro representative confirms that

the building is de-energized from all

sources externally and internally.

Electrical wires and ballasts are an entanglement hazard.

Capacitors

Keep back: do not enter

grow-op building until

BC Hydro representative

disconnects the power.


Substation and generating station fires are rare, but when you respond to a fire at a substation or generating

station, call BC Hydro immediately.

Never under any circumstance enter a substation or generating station unless a qualified BC Hydro worker

is on site and has given you permission to enter. Once BC Hydro is on site, it’s important to set up a unified

command system with BC Hydro and first responders. Ensure everyone remains safe while you wait for a

qualified BC Hydro worker to arrive.

0 Keep the danger zone clear.

• Because of the risks of smoke, airborne toxic combustion products (PCBs), and explosion and debris being

blown over a large distance, keep back a minimum of 100 metres (330 feet) away, preferably upwind.

• Consider the need to evacuate occupants in adjacent areas.

0 Protect surrounding property.

0 Prepare your equipment and resources and establish a water supply.

• Do not park apparatus under transmission or distribution lines, or other structures.

• Metal ladders must not be placed against a substation fence or otherwise used in fighting substation fires.

• Metal tape measures, extension cords and other metal objects can also create a hazard and are not

permitted in any BC Hydro substations.

A BC Hydro representative will have an environmental response plan, drawings and drainage information and

will be able to inform you about any hazards specific to that station and guide you into the area.

2 feet

Fighting fires at substations and generating stations

Do not enter substation.Call BC Hydro immediately.Keep danger

zone clearof onlookers

minimum100 m/330 ft

Firefightersprepare

equipmentand protectsurrounding

property

Wait forarrival ofBC Hydro


2 feet



Typical outdoor substation

Substation components & hazardsAt a substation, you’ll normally find control buildings

with numerous types of computer and protection

hardware and battery banks. Outside are various pieces

of electrical equipment, such as transformers, circuit

breakers, capacitors, covered cable trenches, and

overhead bus bars that conduct electricity. Several of

these pieces of equipment are partly cooled with large

volumes of mineral oil. Transmission voltages are

present in most substations and you will need to

work closely with the on-site BC Hydro representative

and adjust your safe distance accordingly.

Substation ground gridAll equipment within all BC Hydro stations, including the perimeter fence, is grounded to a common grid

beneath the surface.

0 Never extend any equipment from the substation to an area outside the substation or vice versa.

0 All equipment and structures, including the fence, are connected (bonded) to the grid, which extends 1 metre

beyond the fence. The grid protects people from high voltage levels during fault conditions. Firefighting

vehicles that could contact live equipment must be connected to the ground grid while in the station.

If you bring any apparatus inside the substation, a BC Hydro representative must ground it to the grid.

Fence is 1 m/3 ftinside ground gridand is bonded to

ground grid

Ground grid (covered with 15 cm/6”

crushed rock) Allequipment and metal

structure in substationsare bonded to this

common ground grid.

Lightingarrester

Fromtransmission

tower

Busbars

Oilcircuit

breakerCable trenchto substationequipment

Controlbuilding

Transformer Access road


If you’re involved with a substation fire or emergency, be aware of these potential hazards:

0 Sulfur hexafluoride (SF6) is an insulating and arc quenching gas used in many types of electrical

equipment, including switchgear and bus work. In its pure state, SF6 is an odourless, tasteless, colourless,

non-toxic gas. Under normal operating conditions, the gas is totally enclosed within the equipment,

however, an arc fault in SF6 insulated equipment or a sudden release of SF6 can cause significant hazards.

The following potential hazards are associated with SF6-filled equipment.

• SF6 gas used in electrical equipment is usually pressurized at 140-700 kPa.

• SF6 gas is much heavier than air and given a few hours, it may collect in low points of enclosures or

the buildings housing indoor SF6-filled equipment, thereby creating a potential asphyxiation (oxygen

starvation) hazard in the affected area.

• If released suddenly, SF6 will linger at breathing zone heights for hours which creates an oxygen

starvation hazard.

• When exposed to temperatures over 200°C, SF6 will decompose and produce a complex mixture

of gaseous and white/grey dust-like solid by-products. Most of these SF6 by-products are highly

toxic and most are highly corrosive and irritating when they come into contact with moisture (e.g.

in the mouth, eyes or respiratory tract). This may include thionyl fluoride (SOF2), sulfur dioxide

(SO2) and hydrogen fluoride (HF).

• Some SF6 breaker enclosures are confined spaces and the requirements of BC Hydro OSH Standard

303 (confined spaces) must be met if they are entered.

• When SF6 is overheated, the gas will expand and may cause the pressure relief disc to rupture.

Pieces of the disc can be launched, and the released gas can create asphyxiation and chemical

exposure hazards.

• SF6-insulated equipment is present at most indoor and outdoor facilities. Always check with

BC Hydro representatives about the types and locations of SF6 insulated equipment, and maintain

a safe distance of 20 metres until you have been briefed and equipped to respond. Ensure that

the area(s) around the building’s exhaust point(s) are evacuated and, if necessary, secured with

barrier rope/tape to prevent access and exposure of workers and/or the public to SF6 and its

decomposition products.

0 Polychlorinated biphenyls (PCBs) can be still be found in oil-filled equipment to cool and insulate

transformers as they don’t support combustion. They’re an environmental contaminant and high temperature

fires may cause them to break down into extremely toxic components. The presence of PCBs is usually, but

not always, indicated by warning signs.

• If you suspect PCBs in a fire:

1. Wear SCBA and full turnout gear.

2. Position apparatus upwind and approach from upwind.

3. Use foam, dry chemical or CO2 if possible.

4. Provide for liquid runoff containment.

5. Evacuate people located in path of the smoke plume.

6. Follow standard decontamination procedures.

7. You and your gear should be tested after possible exposure.


0 Toxic gas can be released from polyethylene jackets when exposed to a fire. This dissipates quickly in open

air but can be extremely dangerous in enclosed areas. Wear breathing apparatus.

0 High pressure air systems and compressors can reach pressures of up to 3600 PSI (24 MPa).

0 Mercury is toxic and dangerous in contact with unprotected flesh. It’s rare and found only in small

quantities in generating stations and substations. Pre-planning will reveal its presence in your area.

0 Porcelain bushings are found at connections to transformers, circuit breakers, switching equipment

and bus work.

• When subjected to temperatures stresses, the porcelain material can explode.

• Hot insulators exposed to water or foam can shatter or explode.

• This could result in razor-sharp flying projectiles and more oil to fuel a fire.

0 Battery banks comprise of wet cell batteries that usually contain metal plates (e.g. lead, mercury or

cadmium) surrounded by a corrosive liquid/gelled alkaline or acid electrolyte at varying concentrations.

The most common type of electrolyte used in lead antimony and lead calcium batteries is sulphuric acid,

with concentrations typically ranging from 30 to 60 percent by weight.

0 Standby generators will start up and come online automatically in the event of a loss of system power.

0 Control/relay buildings at BC Hydro substations require special consideration when fighting fires. The

nature of the equipment installed within the station, and its high value and susceptibility to damage

from many extinguishing agents requires careful consideration in agent selection.

• Preference must be given to carbon dioxide or halon replacement extinguishers when using hand

portable extinguishers. Any use of water must be cleared by the BC Hydro incident commander.

• Fires inside substation control buildings may involve PVC-insulated cable as a fuel. The combustion

gases given off by PVC are extremely toxic and corrosive. Positive pressure type self-contained

breathing apparatus must be worn when fighting control building fires.

• Some control buildings have automatic fixed fire suppression systems. The most common type of

installation utilizes gaseous and/or preaction systems with full fire alarm/detection. Fire department

connections may be provided for these systems – the location of the FDC is available on the site plan,

or ask the BC Hydro representative where it is located.

• Some control rooms are protected with gaseous suppression systems such as Novec or Inergen.

• Operating sequences and characteristics must be reviewed at the pre-plan stage. The air handling

systems for control buildings, compressor buildings and other support facilities should be reviewed to

assess the start-up and shutdown requirements to prevent soot contamination from switchyard fires

migrating into buildings.

Switchyards

0 Transformers can contain large volumes of combustible insulating oil with a minimum flash point of 145⁰C.

If you need to know what types of oil you’re dealing with, get help from the BC Hydro representative on site.

• The primary and secondary windings inside these transformers are usually insulated with combustible

paper.


• For cooling and insulating purposes, transformer windings are placed in large metal tanks. Usually it’s

possible to extinguish transformer fires before all the oil has been consumed. This can save adjacent

equipment from damage.

• The main hazards on the exterior of transformers are conservators and porcelain bushings.

• Conservators - large tanks at the top of transformers that contain oil. They allow for expansion

and contraction of oil when the transformer is carrying load. Watch for explosion vents, the large

pipes with discs that can rupture. They’re designed to vent if pressure builds up in a transformer.

• Porcelain bushings - when subjected to temperatures stresses, the porcelain material can explode.

0 Circuit breakers are large switching systems in enclosures. Most are equipped with porcelain bushings and

they may contain oil, high pressure air or SF6.

0 Capacitors store energy and can produce deadly high voltages, even when the power is off. Capacitors are

a priority for BC Hydro personnel to make safe as soon as possible. They consist of banks of several small

units that are sealed, and could explode with heat. Some capacitors contain PCBs, which can be health and

environmental hazards. BC Hydro will handle containment and clean-up of any spills. Not every substation

has capacitors.

0 Overhead structures have a metal framework that supports high voltage insulators and conductors

between electrical equipment. Extreme temperature can cause structures to sag, and if they collapse

they could break the porcelain transformer bushings.

0 Synchronous condensers are only found in

a few substations, but use caution:

• Rotating mass

• Electrical hazard

• Hydrogen may be present

• Confined space

0 Control cables carry low voltage power to

fans, pumps and motors. Their insulation is

combustible and could cause fire to migrate.

0 Trenches for control cables start at the control

building and go to equipment in the switchyard.

These could allow burning oil to flow along the

trench, which could ignite and spread the oil fire back

to the control building. Under the direction of a BC Hydro

representative on site, use sand bags or other material in

the trenches to prevent the oil from spreading.

0 Workshops

• Some substations, and most generating stations,

have maintenance shops containing flammable and

combustible liquids. They may also contain herbicides.

• They are a typical industrial installation.

BushingExplosionvent

Conservatorytank

Radiators

Tank


Fighting fires at outdoor substationsFollow the directions given by the BC Hydro incident commander in fighting a fire and especially in applying

water on or near electrical equipment.

Recommended minimum distances for the use of water fog/spray under normal circumstances should be

maintained at 10 metres (33 ft). Water must never be discharged in the form of a straight stream. Fog or

water spray must be set at a minimum of a 30⁰ fog nozzle pattern setting, with a minimum pressure of

100 psi at the nozzle.

The majority of fires in substations involve combustible insulating oil used in transformers, circuit breakers

and capacitors. This insulating oil has a minimum flash point of 145°C (296°F) and will generate temperatures

in excess of 1850°F in the immediate fire zone. Some substations have oil filled equipment containing oil in

quantities in excess of 90,000 litres (20,000 imperial gallons) per unit. Some of the problems encountered

with these oil filled equipment fires concern the damage to adjacent equipment (within 10 m/33 ft) and

the re-ignition of the oil caused by hot metal surfaces. The effects of these problems can be minimized by

the continued application of water in a fog form onto adjacent equipment or hot metal surface areas. If the

equipment has been confirmed as de-energized and isolated, foam may also be used to prevent re-ignition.

Another serious potential problem with the combustible insulating oil is the entry of burning oil into cable trenches,

cable tunnels, and manholes. Trenches and drainage systems may act as conduit for spilled insulating oil. If the spill

fire flows away from the source, it can spread to adjacent equipment or buildings, making a spill fire very large and

extremely difficult to control. Spill containment should be reviewed on site, and consider the following:

0 Cable trench configurations in relation to slope and proximity to buildings and other oil-filled equipment

0 Site drainage systems

0 Surrounding city or municipal drainage system connections

0 Adjacent natural water courses

Keep back 10 m/33 ft

Use 300 fog pattern100 psi minimum


Equipment must be de-energizedand grounded prior to applying foam

Keep back at least 10m/33 ftfrom all energized equipment

Fires in these areas can be difficult to extinguish as the combustible cable insulation may ignite. Do not direct

water, fog or foam into these areas unless you have been requested to do so by a BC Hydro supervisor or

qualified electrical worker.

Fighting fires at generating stationsGenerating stations have similar equipment to substations plus additional hazards like storage dams or large

quantities of fuel and lubricating oils. Each plant has an emergency plan and plant personnel are trained in

these procedures and in the use of on-site emergency equipment.

Follow the same procedures as you would at a substation and in the event of a fire and wait for a qualified

BC Hydro crew to arrive.

Be aware of other potential hazards at generating stations.

0 Reservoirs and penstocks supplying pressurized water to the turbine

0 Large rotating mass including turbine, turbine shaft and generator

0 Electrical hazards including control and excitation systems and generator output

0 Large lubrication systems and oil reservoirs

0 High pressure water, air, steam and some toxic substances

0 Many underground levels and deep chambers. Firefighting may require unusual physical exertion and

rescues in confined spaces.


Transmission structures

Transmission lines can be supported on wood, concrete or steel structures. The design can vary from single

wood pole to multiple wood poles for 60 to 230 kV to steel structures for 138 to 500 kV.

InsulatorsPin type insulators carry the conductor on top and are used for 60,000

volts or less. Bell type insulators are suspended from the structure with

the conductor running on the bottom of the stack of insulators. Voltages

range from 60,000 to 500,000 volts.

Pin type

Up to 60,000 volts

Bell type

60,000 volts to 500,000 volts

Typical steel structure

500 kV self supporting 500 kV guyed tower

Typical wood structures

60 kV

138 kV

138 or

230 kV

Determining voltage

VOLTAGE SUSPENSION

60 kV 4 bells

138 kV 7 bells

230 kV 12/14 bells

287 kV 15 bells

360 kV 18 bells

500 kV 21-23 bells

By counting the numbers of

insulators on a string, the voltage

of the line can be determined by

using the chart.

The lines are supported or suspended from the structures on insulators.

BC Hydro transmits electrical energy from its generating stations to substations and major customers via high

voltage transmission lines at 60,000 volts (60 kV) to 500,000 volts (500 kV). These transmission lines

are located on corridors known as rights-of-way in urban, farm land and forested areas. Some right-of-way

also accommodate underground gas and oil pipelines. Transmission line rights-of-way may contain single or

multiple circuits of different voltages on separate structures.

Fighting fires on transmission lines and rights-of-way

Fuel

Working under linesIt is essential that you exercise extreme

caution when working under high voltage

transmission lines. Have a qualified

BC Hydro representative on site to advise

on equipment set up and movement.

A safety watcher may be required when

working on the right-of-way. Maintain

appropriate safe distances from conductors

keeping in mind the lines are prone to

sag either from load on the line or the

outside temperature. Never under any

circumstances dispense fuel on the

right-of-way.

Determining safe distances

VOLTAGE DISTANCE*

60 kV 10 m (33 ft)

138 kV 10 m (33 ft)

230 kV 14.5 m (47.5 ft)

287 kV 18 m (60 ft)

360 kV 22 m (72 ft)

500 kV 32 m (108 ft)

* Measured from base of tree

Trees on linesIf a tree falls against the line remember the dangers of electrical hazards due to step and touch potential.

BC Hydro’s electrical system has an automatic re-closing function that will re-energize the line without

warning. If you have moved close to the tree you may be putting yourself or others in great danger.

Maintain safe distances as per chart.


Sag

Flashover0 An intense fire burning on the right-of-way of a

power line may degrade the quality of the insulation

of the air to the point of producing flashovers to the

ground surface if the flames reach a distance of less

than 2 metres to the power line.

0 A high transient electric current then flows through the

ground and generates step voltage (the ripple effect).

0 These may be hazardous to firefighters working in the

vicinity of the arcing point.

0 Dense smoke can also be a problem on the right-of-way, especially if the smoke contains a high count of

particulates and/or moisture.

Flashover hazardous zoneVOLTAGE DISTANCE*

60 kV 10 m (33 ft)

138 kV 10 m (33 ft)

230 kV 14.5 m (47.5 ft)

287 kV 18 m (60 ft)

360 kV 22 m (72 ft)

500 kV 32 m (108 ft)

* Measured from either outer phase


Livewires

2 mor

less

Fire

Flashover hazardous zone0 Should intense fires be burning near live conductors a step potential hazard could occur within what is

called the flashover hazardous zone. The zone extends a certain distance from the outer phase conductors

depending on the voltage of the power line.

0 Even if the fire is under one outside conductor, the safe distance should also be applied to the other outside

conductor in case the flashover affects the tower or a grounded structure.

0 The same safe distance should also be applied to any guy wires attached to the tower at their point of entry

to the ground.


Other hazards0 Wood pole structures present an additional hazard due to their combustibility.

0 In situations where the fire has not reached the ROW, efforts should be made to soak down the area at

the base of the poles within 10 metres (33 feet). Note: Fire retardants can be used at the base of poles if

applied carefully.

0 If the right-of-way is fully involved with fire use the following guidelines:

• In the instance of a fire involving low level vegetation such as grass or bush, normal limits of approach

for step potential/application of water at 10 metres (33 feet) is safe.

• In fire situations with flame or smoke within 2 metres (6 feet) of conductors, safe distances for

flashover hazards must be observed.

0 If a fire has to be fought on or near a transmission line right-of-way, the distance that you can be to the

power lines depends on the intensity of the fire, smoke conditions, and the voltage involved.

0 The application of water requires special procedures. A ground level fire involving low fuel loads can be

fought safely with normal fire fighting procedures.

0 If there is a chance that water from the nozzle will come in contact with the conductor, a 30 degree fog

pattern with a 100 psi minimum pressure must be used.

0 High intensity fires involving high fuel loads producing significant flame and smoke require additional

precautions.


0 The safe distances with hose lines must be

increased as per the flashover hazardous zone.

Remember the dangers of step potential

because transmission lines are high voltage

and towers are very conductive.

0 Do not use class “A” foam unless the lines have

been de-energized and grounded.


Aerial tanker optimum safe zone0 Caution must be exercised when using air tankers to drop water/fire retardant on rights-of-way.

0 The retardant used is an extremely good conductor and is also highly corrosive.

0 When conducting tanker drops you should:

• Request BC Hydro to de-energize the lines if possible.

• If the lines cannot be de-energized, drop the retardant parallel to the lines (optimum safe zone).

Aerial tanker alternate safe zoneIf you must drop retardant across the right-of-way, do so at mid span - do not hit towers or insulators.


10 m

32 m

500 kVtower

500 kVtower

Conductivitythrough water

B16-119

Firefighter’s guide to facing electrical hazards - BC Hydro · PDF...

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