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ELECTRICAL FACTS & SAFETY  Electricity
should be respected, not feared. Electricity will always seek the
easiest path to ground. This is true whether the electricity comes
from a household lighting circuit, a high voltage power transmission
line or from lightning. Any person who places themself between any two energized conductors, or any energized conductor and ground, will become part of an electrical circuit. This can kill or cause serious injury.
COMMON TERMS Voltage - the force that causes the flow of electricity (measured in volts). Current - is the rate of flow (measured in amps). Resistance - is effect of friction on the flow of electricity (measured in ohms). INSULATORS, CONDUCTORS AND SEMI-CONDUCTORS All materials conduct electricity in varying degrees. Insulators, such as glass, conduct electricity in quantities too small to be measured, whereas conductors, such as metal, conduct electricity readily in large amounts. Wood, earth and rubber tires are classified as semi-conductors and depending on conditions such as moisture content and contaminants can conduct large amounts of electricity. LOW VOLTAGE HAZARDS Most electrical fires originate in equipment operating below 750 volts. In the electric industry, this is referred to as low voltage. Home heating systems and home appliances operate at 120/240 volts. Although the hazard is increased with high voltage installations (greater than 750 volts), it is important for emergency personnel to realize the hazards for even relatively low voltages. VOLTAGE GRADIENT ON THE GROUND SURFACE Electricity always seeks the quickest, easiest path to ground. Electrical systems use conductive grounding rods to ensure that any stray electricity is returned to earth safely. These rods are driven eight feet or more into the ground to ensure deep dispersal of the power. If, however, electricity is released onto the ground, as when a live wire lies on the ground, the electricity will fan out from the point of contact. There is a rippling effect like dropping a pebble into calm water. In the pool of water, the wave created at the point of contact gets smaller as it rings 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 progressively. This effect is known as ground gradient and a knowledge of how it operates may some day save your life. BACK STEP POTENTIAL AND TOUCH POTENTIAL The ground gradient, or voltage drop, creates two problems known as step potential and touch potential. Assume that a live downed wire is touching the ground and has created a pool of electricity. If you were to place one foot near the point of ground contact (at x voltage) and your other foot a step away (at y voltage), the difference in voltage would cause electricity to flow through your body. This effect is step potential. Similarly, electricity would flow through your body if you were to place your hand on an energized source, while your feet were at some distance from the source. The difference in voltage in this case is referred to as touch potential. If you touch an energized wire or another energized object and the ground at the same time, you may be killed or injured. Before any treatment can be given to a victim, the danger must be removed. DEALING WITH FALLEN WIRES Don’t expose yourself to risk while trying to eliminate the danger. Always assume that wires are live and dangerous. Inform the utility as soon as possible and utility staff will be sent to remedy the situation. In some distribution systems the power lines may be fed from several sources or directions, therefore the ends may still be live and hazardous. The power may also be turned back on automatically through automated equipment or processes. ON ARRIVING AT THE SCENE Park your vehicle well away from any fallen wires, at least 20 to 25 feet and examine the surrounding area carefully. Locate all wire ends and ensure that no one makes contact with any energized objects. Keep people away from any object even those some distance away that may be energized by live wires. BACK THE EFFECT OF ELECTRICITY ON THE BODY The
effect of electricity on the body depends on the amount of current
and the length of time the body is exposed to it. The higher the
current, the less time a human can survive the exposure. The path
of electricity through the body is also critical. For example,
current passing through the heart or brain is more life-threatening
than current passing through the fingers. It takes approximately
1,000 milliamps (1 amp) of current to light a 100 watt bulb.
It is the amperage that kills or injures but the voltage which pushes the current through the body, is also important. When a victim is exposed to household voltages, he or she may suffer a muscle spasm and may be locked on to the electrical source until the circuit is turned off or until the victim is dragged clear, often by the weight of his or her body falling clear of the contact. Relatively long periods of contact with low voltages are the cause of many electrical fatalities in the home or at work. At very high voltages the victim is often quickly blasted clear of the circuit. This results in less internal damage, such as heart failure, but terrible surface burns on the body at the entrance and exit of the current. GFCI - Ground Fault Circuit Interrupter GFCI's are specified by the Canadian Electrical Code to be located on outdoor plugs, in bathrooms and washroom receptacles, around swimming pools, marinas and yacht clubs, used with submersible pumps, in-floor electric heating, bare element water heaters, landscape lighting in damp locations and with portable electric equipment. The prime function of a GFCI is to provide protection against hazardous electric shocks from leakage current flowing to ground (most likely through you!) from defective circuits or equipment. An example of an excellent application of a GFCI is its use with an electric lawn mower. Damp grass and a defective mower are a recipe for electrocution. It is highly recommended to use a GFCI when electrical equipment is used in damp or wet locations. A proper functioning GFCI will provide an additional level of protection in your safe use of equipment. VICTIMS OF ELECTRICAL SHOCK SHOULD BE EXAMINED FOR:
Here's an electrical safety tip: When decorating outside for Christmas season never carry aluminum ladders, poles or other long objects when you're near electrical lines. The results could be fatal.
Electric and Magnetic Fields (EMF) are invisible lines of force surrounding any wire or device that uses electricity. EMF are found everywhere electricity is used - from house wiring and appliances to electric power facilities such as substations and electrical lines. As your distance from a source of EMF increases, the force of the field decreases rapidly. |