Safety guidelines for emergency personnel The following presentation contains safety guidelines to assist police, fire and ambulance personnel in emergencies involving electrical facilities before the arrival of SaskPower personnel.
Electricity – some basic facts • Electricity is always trying to get to the ground. • If you touch two energized wires or if you touch an energized wire while standing on the ground, you’ll become part of an electrical circuit, which could result in your death or a serious injury.
Common electrical terms and definitions • Voltage – similar to water pressure, and is the force that causes the flow of electricity. • Current – can be likened to the rate at which water flows through a pipe. • Resistance – is similar to the effect of friction on the flow of water in a pipe.
Insulators, conductors and semi-conductors • Insulators – conduct electricity in small quantities and cannot normally be detected. • Conductors – conduct electricity in large amounts. • Semi-Conductors – water, wood, earth and rubber tires are classified as semi-conductors. In the right conditions, semi- conductors can conduct large amounts of electricity.
Low voltage hazards • Most electrical fires originate in equipment operating below 750 volts. • Home heating systems and appliances operate at 220 volts or less. • It is important for emergency personnel to realize the hazards of even relatively low voltage.
Voltage gradient on the ground surface • Electrical systems use conductive grounding rods to ensure stray electricity is returned to the earth safely. These rods are driven about 2.5 metres (or eight feet) or more into the ground. • If electricity is released into the ground surface (such as when a live wire lies on the ground), electricity will fan out from the point of contact.
Voltage gradient on the ground surface (cont.) • A rippling effect similar to dropping a pebble into calm water. • In water, the wave created gets smaller as the ring goes out. • Similarly, in this pool of electricity, the energy is at full system voltage at the point of ground contact, but as you move away from the contact point, the voltage drops. This effect is known as ground gradient.
Electrical installations • Electricity is generated at voltages ranging from 2,300 volts to 20,000 volts. • Some transmission lines operate as low as 72,000 volts, others as high as 230,000 volts. • Voltage is reduced at switching stations and is sent on distribution lines to customers.
Electrical installations (cont.) • Power plants, substations, underground vaults and other SaskPower installations vary greatly from other buildings. • These facilities present unusual hazards to you. • You will not be familiar with these surroundings, and good communication and co-operation between you and SaskPower is crucial.
Step potential and touch potential • Ground gradient, or voltage drop, creates two problems known as step potential and touch potential.
Step potential • If your feet are spread apart on energized ground (e.g. when an electrically charged wire is touching the ground), electricity can flow through your body from the area of higher voltage to the area of lower voltage (step potential). • If you must move on energized ground, always keep your feet together and touching--hop or shuffle (heels never pass toes).
Step potential and touch potential • If you touch something that is energized while standing on lower-voltage ground, electricity will flow through your body from the higher voltage source to the lower voltage ground. The difference in voltage in this instance is referred to as touch potential. One hand is at 9 kV while the feet are At 3.5 kV. The difference is 5.5 kV. kV (1000 volts) (Distance in metres) Contact point
Faulty electrical equipment • Electricity is safe as long as it’s properly controlled. • Hazards are created when electrical equipment wires become faulty due to: – wear or deterioration – improper installation – improper maintenance – damage or breaks • Any one of the above may cause arcing or overheating of electrical equipment causing an electrical fire.
Faulty electrical equipment (cont.) • An electrical arc is a sudden flash of electricity between two points of contact. • The majority of fires caused by overheating result from overloading electrical conductors and motors.
Injuries caused by electrical shocks • The effect of electricity on the body depends on the amount of current and length of time the body is exposed to it. • The path of the electricity through the body is also critical. • Most common household currents are one-two amps. • It takes approximately one amp of current to run a 100-watt light.
Average tolerance Can just feel it Can’t let go Electric Current in milliamperes Increasing pain Probably fatal
Effects of electricity on the body • A person exposed to household voltages may suffer from muscle spasms and become locked onto the electrical source. • At very high voltages, the victim is often blasted clear of the circuit. This may result in terrible surface burns. • A person exposed to a large electric arc may be injured by the intense heat or ultraviolet rays, which can cause serious eye damage. • Severity of the shock will be increased if the electric current touches moist or broken skin.
Victim of electrical shock • Any victim of electrical shock should be examined for the following: • cardiac arrest • temporary paralysis of the respiratory centre, causing breathing failure • ventricular fibrillation of the heart • burns to tissue at the current entrance and exit points • fractures caused by muscle spasms • Keep in mind that the electrical danger must be removed before any treatment can be given.
Inability to breathe Ventricular fibrillation Effects of electric current passing through the body Cardiac arrest Involuntary muscle reaction Electrical burns from current To ground To ground
Fallen power lines • Electrical distribution wires may be broken by storms and ice, or as the result of vehicles striking power poles. • If you encounter broken or fallen wires, always assume the wires are energized. • Inform SaskPower personnel immediately (call 310-2220).
Fallen power lines - action to be taken • Park far enough away from fallen wires. • Assess the situation before getting out of your vehicle. • If it’s night, use a flashlight to examine the surroundings.
Fallen power lines - action to be taken (cont.) • Locate all the wire ends. • Always assume fallen power lines are alive. • Supervise any public and keep them away to prevent further situations.
Fallen power lines - action to be taken (cont.) • Place a guard around the danger zone to keep the public away. • Call SaskPower for help (310-2220). • Supervise any public and keep them away to prevent any further situations.
Trapped in a vehicle by a fallen live wire • Wherever possible, SaskPower will handle these situations. • If SaskPower personnel are not yet on the scene, use the following guidelines in these emergency situations:
Trapped in a vehicle by a fallen live wire (cont.) • If a fallen wire lies under a vehicle with one or more people inside: • If the driver is unhurt and can move the vehicle, instruct the driver to move the car away from the fallen wire providing no further system damage will occur. • Remember, keep onlookers away and do not touch any part of the vehicle, you could be electrocuted.
Trapped in a vehicle by a fallen live wire (cont.) • If a fallen wire lies across the vehicle with one or more people inside: • If the driver is injured and cannot move the vehicle, instruct the driver to stay in place until SaskPower personnel arrive. • If the occupants are not injured, but the vehicle has a fire that cannot be easily extinguished and the vehicle cannot be moved, instruct the occupants to get out by a standing jump.
Trapped in a vehicle by a fallen live wire (cont.) • Tell them to keep both feet together as they jump. • Do not touch the ground and the car at the same time. • Hop with both feet together or take short shuffle steps away from the vehicle - this can be very dangerous and should only be used as a last resort. If you contact the car and the ground at the same time it may prove fatal.
Problems related to kiosks or pad-mount transformers • If a kiosk shows evidence of being tampered with, call SaskPower with details of the location. • If a kiosk is damaged in a vehicle accident, do not touch the kiosk or any vehicle that may be touching it. Instruct the driver to move the vehicle away from the kiosk if possible - if not, warn occupants to stay in the vehicle. • Call SaskPower (310-2220). Treat as energized, extremely dangerous
Electrical facilities and wildfires • There are many power lines and electrical facilities in the forest and on the prairies, and the result of coming into contact with any of these power lines or electrical facilities is almost catastrophic. • Always stay a safe distance from power lines. • When hand cutting trees, control their fall to avoid contact with power lines and other electrical apparatus.
Electrical facilities and wildfires (cont.) • When using a Caterpillar to excavate fireguard or build an access road, ensure trees are pushed away from power lines and electrical apparatus. • Exercise extreme caution to avoid hitting power poles and guy wires. • Most rural farms, acreages and businesses are dependent on electricity for operation and suppression of fire equipment.
Electrical facilities and wildfires (cont.) • When a forest, bush or prairie fire occurs in areas where electrical lines and facilities will be affected, SaskPower will attempt to keep these facilities alive after ensuring it is safe to do so. • SaskPower will facilitate shutdowns. • Always assume the power is still on.
Electrical facilities and wildfires (cont.) • If a grass fire erupts and engulfs a transformer, douse the fire with a mist or fog spray - do not use a steady stream of water. • If a tree has fallen onto a power line, call SaskPower with the details of the location - do not attempt to remove the tree by yourself.
Water and electrical fires • In a situation where broken wires are tangled around a power pole, do not shoot a steady stream of water on an electrical fire, conductor or apparatus unless under the direct supervision of SaskPower personnel. • Use a fog spray.
Substation fires • Upon arriving at a substation fire, you should be prepared to protect adjacent properties. • SaskPower will advise when the substation is electrically safe for you to proceed with conventional fire-fighting equipment. • If SaskPower personnel are not present when you arrive, call SaskPower (310-2220) to make sure staff have been dispatched.
Substation fires (cont.) • Only SaskPower personnel are familiar with substations they serve and can identify areas that are electrically safe. • If you have been called to a substation fire, do not enter the substation without SaskPower personnel. • Keep the danger zone clear of onlookers and await the arrival of SaskPower personnel.
Unauthorized persons in substations • Dangerous situations arise when people play around electrical installations and equipment.
Unauthorized persons in substations (cont.) • If people are seen climbing over a fence into a substation, warn them of the dangers and ask them to remain by the fence. Call SaskPower. • If the person in the substation is injured, call SaskPower immediately.
Fires and explosions in underground electrical vaults • Like many cities, SaskPower’s cables for transformers and switchgear circuits are situated underground, with access by manhole. • These underground systems are designed to withstand great stress. • Earth movement can crack concrete walls of cable tunnels, as well as adjacent sewer pipes, natural gas pipes and water mains.
Fires and explosions in underground electrical vaults (cont.) • The potential for hazardous conditions can result in the accumulation of explosive and toxic gases and dangerously high water levels. • Electrical failure of cable may result in an explosion or fire. • You should consult your OH&S confined space rules and regulations for guidelines regarding rescue.
Fires and explosions in underground electrical vaults (cont.) • If a victim is lying unconscious at the bottom of an open manhole, you should call SaskPower (310-2220) and indicate the location and number of manholes involved. • Request assurance that the cables will not be energized. • If there is a fire in the hole, use only non-conducting fire extinguishing substances.
Fires and explosions in underground electrical vaults (cont.) • Attach a non-metallic safety line. • Do not touch any electrical components. • Give first aid and wait for help to remove the victim.
Fires and explosions in underground electrical vaults (cont.) • If you have been called to the scene where smoke is escaping from the manholes, call SaskPower (310-2220) and give details of the location. • Stop traffic and keep public at a safe distance. • Do not attempt to remove the manhole covers. • Maintain precautions until conditions have been evaluated.
Fires and explosions in underground electrical vaults (cont.) • If you have been called to the scene where smoke is escaping from the manholes and you have to identify or aid a victim, approach the manhole with extreme caution as it may explode again. • Stop traffic and keep public at a safe distance. • Do not attempt to remove the manhole covers. • Maintain precautions until conditions have been evaluated.