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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
Firefighter’s Electrical Safety Guide Page 3
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).
Firefighter’s Electrical Safety GuidePage 4
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.
Firefighter’s Electrical Safety GuidePage 6
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
Firefighter’s Electrical Safety Guide Page 7
ABC BUSINESS CORP
CAUTIONCAUTIONCAUTIONCAUTION
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.
Firefighter’s Electrical Safety GuidePage 8
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
Firefighter’s Electrical Safety Guide Page 9
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
Firefighter’s Electrical Safety GuidePage 10
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
Firefighter’s Electrical Safety Guide Page 11
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.
Firefighter’s Electrical Safety GuidePage 12
Keep backminimum 10 m/33 ft
Do not parkunder lines
Examine suroundingsbefore exiting the vehicle
Page 13Firefighter’s Electrical Safety Guide
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.
Firefighter’s Electrical Safety Guide Page 15
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.
Firefighter’s Electrical Safety GuidePage 16
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.
Page 17Firefighter’s Electrical Safety Guide
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
Firefighter’s Electrical Safety GuidePage 18
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.
Page 19Firefighter’s Electrical Safety Guide
Keep back minimum 10 m/33 ftfrom point of contact
Minimum 100+ psi 300 fog nozzle
Do not use foam
Firefighter’s Electrical Safety GuidePage 20
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
Firefighter’s Electrical Safety Guide Page 21
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
Firefighter’s Electrical Safety GuidePage 22
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.
Firefighter’s Electrical Safety Guide Page 23
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
Firefighter’s Electrical Safety GuidePage 24
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.
Page 25Firefighter’s Electrical Safety Guide
Do not approach a manhole after a fire or explosion. It may explode again.
Keep public backminimum 33 m/100 ft
Firefighter’s Electrical Safety GuidePage 26
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
Firefighter’s Electrical Safety Guide Page 27
Fighting structural fires
24
CAUTIONCAUTIONCAUTIONCAUTION
CAUTIONCAUTIONCAUTIONCAUTION
CAUTIONCAUTIONCAUTIONCAUTION
CAUTIONCAUTIONCAUTIONCAUTION
CAUTIONCAUTIONCAUTIONCAUTION
CAUTIONCAUTIONCAUTIONCAUTION
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
Firefighter’s Electrical Safety GuidePage 28
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.
Page 29Firefighter’s Electrical Safety Guide
10 m distance fromladder to power lines
Use safety watcher
Firefighter’s Electrical Safety GuidePage 30
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.
Firefighter’s Electrical Safety Guide Page 31
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.
Page 33Firefighter’s Electrical Safety Guide
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
Firefighter’s Electrical Safety GuidePage 34
2 feet
CAUTIONCAUTIONCAUTIONCAUTION
CAUTIONCAUTIONCAUTIONCAUTION
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
Firefighter’s Electrical Safety Guide Page 35
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.
Firefighter’s Electrical Safety GuidePage 36
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.
Firefighter’s Electrical Safety Guide Page 37
• 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
Firefighter’s Electrical Safety GuidePage 38
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
Page 39Firefighter’s Electrical Safety Guide
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.
Firefighter’s Electrical Safety GuidePage 40
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.
Page 41Firefighter’s Electrical Safety Guide
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
Firefighter’s Electrical Safety GuidePage 42
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.
Firefighter’s Electrical Safety Guide Page 43
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.
Firefighter’s Electrical Safety GuidePage 43
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.
Firefighter’s Electrical Safety GuidePage 44
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.
Firefighter’s Electrical Safety Guide Page 45
10 m
32 m
500 kVtower
500 kVtower
Conductivitythrough water
B16-119