Beware electrical hazards

Beware electrical hazards


Air circuit breakers. Top breakers are open; breakers directly under them are closed33,000-volt oil circuit breaker. This will open when there is trouble on the line

If a conductor is down and the squadman knows that it is deenergized, he should respect the wire just as much as he would if he knew the line were hot. All primary circuits are supposed to have oil circuit breakers on them that automatically open or deenergize the circuit if there is trouble on it.

Precautionary steps

When a line crew goes to work on a damaged circuit they take two precautionary steps: First they “put air in the line.” That is, they open a switch other than the oil circuit breaker so that as much as 3 feet of air is between the line and load side of the switch depending on the voltages involved. A cardinal rule for linemen is: “Never work behind an oil circuit breaker.” An oil breaker is a spring-loaded automatic switch, and even though it is supposed to “lock out,” malfunctions can and do occur and the switch just might reclose itself.

Secondly, the line crew will ground all the circuits on the line side of the break. A fireman cannot “put air into a line,” neither does he have the equipment to ground a line, so these two items alone are enough to make him stay clear of conductors on the ground.

It is necessary to know a little about power company procedures in locating and clearing a “locked out” circuit to understand the most important reason to stay clear of broken primary lines. If a lineman knows where and what the trouble is he will open air break switches and ground the lines immediately.

However, in about 95 per cent of his trouble calls, the only information he receives is that a certain substation or circuit is out. The first thing he does is to go to the oil circuit breaker, reset the switch and close the breaker. He is supposed to switch the breaker to manual operation which only allows the breaker to relay one time. There are indicators on the larger breakers which will show him what to look for, if there is still trouble on the line.

In about 25 per cent of the arses the breaker will hold, because some line trouble will clear itself, such as a limb falling across the line, or perhaps a fused tap line that has grounded or shorted conductors. If the oil circuit breaker is not set on “manual” and left on “automatic,” when a lineman trips it on, the breaker will relay or turn itself on three times before it locks out. The first relay will be instantaneous, the second in about a minute, the third in about two minutes later. Either one of these “shots” of electric current is enough to be fatal. Just remember that even though a conductor is deenergized when you arrive on the scene, there is a very strong possibility that it will not stay deenergized.

Another important factor to remember is that every conductive object that a live wire touches becomes a hot conductor. This could be an automobile, a fence, wet ground or pavement, guy wires, telephone lines, poles themselves and probably most important to us as rescue workers—people or animals. We have to disengage people from live conductors, but in far more instances we will need to recognize foreign conductors, or conductors other than the actual wires, and take the necessary precautions to keep ourselves and others away from these seemingly innocent hazards.

Emergencies involving vehicles

If live conductors touch a vehicle, the vehicle becomes a conductor. If the vehicle is upright the rubber tires act as an insulator, energizing the vehicle. Any person coming in contact with the vehicle while standing on the ground will, with his body, give the current a path from the energized vehicle to ground. This flow of electric current through the body can and often does prove fatal.

If the occupants of the vehicle remain inside, they are relatively safe from electric shock. When the victims are rational, and conditions permit, tell them to stay in the car. If, because of fire or injury, it is imperative to remove them at once, remember that as long as a person does not come in contact with both the conductor and the ground at the same time he is relatively safe.

If people inside of the vehicle can understand and carry out instructions, tell them to jump off, not step off. By the same principal, if squadmen get into a similar situation, they, too, should jump off, making sure that both hands and feet are clear of the vehicle before coming into contact with the ground.

Ground conductivity

It is impossible to give a set rule on how to approach an energized vehicle or conductor. The ground around a conductor is also energized. The amount of current and the size of the area are dependent upon the conductivity of the earth or pavement, which is determined by moisture and chemical content.

Continued on page 930

It is possible to receive a good shock by walking up to a grounded conductor. This happens when the legs and hips give the electric current a path of less resistance to pass through, than does the ground over which the person is walking. The wetness of the earth or pavement would probably be the more important factor in determining how close you can approach a grounded conductor. Always approach slowly with short step. Usually you will feel a small stinging or shocking sensation on the soles of your feet before you get close enough to get into serious difficulty.

Handling energized wires

When all other means of saving life have been expended, and it is necessary to move a person from a conductor of electricity, a fireman should have some idea about how to protect himself and others involved in the rescue. The handling of any conductor is a last resort. The term “any” is used because you should assume that “all” conductors are energized.

There are many instances when the risks involved in rescue are not justifiable. For example, if a person is in contact with a transmission or distribution conductor and is burned severely and quite obviously beyond help, it would be a foolhardy gesture on the part of a squadman to risk his life to save a body. One victim for a coroner is far more desirable than two or more. If high voltages are involved, 13,000 volts and up, the risks involved in moving a line are terrific. Rope should not be used on high-voltage lines unless it is dielectric rope and is absolutely dry. Even hot sticks that linemen use are kept in heated dehumidified trailers, and are tested regularly. Stay clear of extremely highvoltage lines regardless of the circumstances.

Moving lower-voltage lines

There are several methods of moving lower-voltage primary lines. One of these methods is to use a dry rope. Each end of a ¼-inch rope, 100 feet long, should be weighted with ½pound weights. Put one end of the rope on the ground about 30 feet from the conductor. Throw the other end of the rope under the conductor so that it will be at least 30 feet from the conductor itself. Then toss the end that is on the ground near you over the conductor. You now have the rope looped around the conductor. Go around the broken conductor to both ends of the rope and pull the conductor away from the object or area that you want to clear, being careful not to let the wire touch objects that would endanger the safety of yourself and others.

Dry boards can be used to move a conductor, but the board should be dry and clean and at least 12 feet long. Regular linemen’s rubber gloves are good to use if you happen to have them, but they should not be depended on when handling conductors carrying more than 5,000 volts.

“A slow hurry”

In rescue work every second counts. A good squadman will proceed in a slow hurry, evaluating the risks involved against the possible good he could do by taking these risks.

When a person has been lying on a conductor for only a matter of minutes, perhaps only three minutes will make the difference between life and death. The victim can be rolled off the conductor with hot sticks or dry boards, or he can be pulled off with a dry rope. If the conductor is grounded, care should be taken to keep it grounded, because the more current that flows into the ground the less current will flow through the victim’s body. Bystanders should be kept at least 100 feet back for their own safety and so that rescuers will have sufficient space in which to work. When a victim is removed from a conductor more burns may result, but the burns are not of primary importance at this time. Air exchange and blood circulation must be started immediately. Do not touch the victim or any part of his clothing with your hands or feet until he is clear of the conductor.

First-aid treatment of electric shock

Two immediate possibilities in electric shock cases make fast and precise first-aid treatment a vital necessity. When there is a possibility of saving the life of an electrocution victim two factors have to be determined almost immediately: Does the victim have a pulse? Is the victim breathing? Other complications such as burns and traumatic shock will have to be considered and are important, but the first and immediate problem is to restore blood circulation and put oxygen into the victim’s lungs so that the blood can carry oxygen to the brain and other vital organs. A knowledge of closed chest cardiac massage and mouth-tomouth resuscitation is a must at such time.

Beware electrical hazards


Beware electrical hazards

UNCONTROLLED ELECTRICITY is more dangerous than a gun in the hands of a maniac. Many professional linemen have been electrocuted working around electricity while it was in a controlled state. It is infinitely more dangerous for a fireman or rescue squadman, unskilled in the handling of electric current, to attempt a rescue, or to attempt to clear a hazardous situation involving uncontrolled electricity.

In most instances when a lineman is called out to work on wires that are down, and where the voltage exceeds that of house current, the current is shut off the damaged circuit until the lines can be repaired. A fireman cannot deenergize a hot circuit. This has to be done by power company personnel.

If conditions are such that life can be maintained or saved without having to get in the immediate proximity of energized conductors, the squadman should use all available means to keep himself and others away from fallen wires and objects with which the wires might be in contact. Notify the local power company as soon as possible.

If there is any danger of people coming into contact with energized wires or objects, do not leave the scene, but send someone else to notify the power company. Set up a safety zone around the danger areas and maintain this safety zone until relieved by police or power company personnel. Enlist help from passers-by, if necessary.

General procedures—wires down

Overhead conductors are usually broken somewhere in a community every time there is a wind or ice storm. During and after extremely bad weather, we all realize that there may be trouble and we are more or less alert for these emergencies.

Five types of conductors on pole: (From top to bottom) Static shield-grounded conductor; 33 kv on two top cross arms; 4,160 v on third cross arm, secondary conductors and a telephone drop. Sign attached reads: Danger High Voltage Overhead110,000-volt transmission line. Grounded static shield conductors are attached to tip of each pole

However, there are other situations which can and do cause overhead conductors to fall. Temperature changes over a period of time can cause a bad connection. The connection then generates enough heat to burn a line apart. Lightning can damage an insulator sufficiently for it to break down days, weeks, or even months later in good weather, burning apart a conductor. Overloaded circuits, faulty material or improper construction, malicious or innocent grounding of conductors with some object such as a chain or a piece of wire, and wrecks involving poles, are but a few of the many conditions which cause wires to fall to the ground.

Even though these conditions are not routine in a well-built distribution system, they are not unusual. When an energized conductor is on the ground, or low enough to be contacted from the ground, an emergency exists.

The question often arises whether or not a line is “hot” and if so, “how hot?” Lines on tops of poles and supported by three or more insulators carry as much as 110,000 volts. Lines supported by one large insulator carry as much as 33,000 volts. These lines are called transmission lines and are not usually built on highway right of ways. However, they do cross highways, and near or in towns and cities they are often located on street or highway rights of way.

Lines which parallel streets and highways and which have transformers on them are called distribution lines. They usually have smaller insulators and the lines are either attached to the top of the pole or on cross arms. They carry voltages varying from 2,300 volts to 13,000 volts and are called primary lines.

The difference between being electrocuted with 2,300 volts and 13,000 volts is comparable to the difference between being shot by a .45-caliber bullet and 90-mm shell. You have a slight chance of surviving a 2,300-volt shock if you have only received a brush or short charge. The chances of surviving higher voltages are practically nil.

Wires running below the primary wires carry voltages used in houses— 110-220 volts. You have heard of people who stick fingers into light sockets to see if the current is on, or to show off. When a squadman sees a secondary line, or a service wire down, he should be no less concerned about it than he would be about a primary line. Never forget this fact: More people are killed by 110 volts than all other voltages combined.

Telephone lines are usually strung under secondary lines. These are usually insulated and we might feel that we need not bother about them. In most cases, this assumption is correct, but there is always the possibility that a primary line may be in contact with the telephone line several miles away. This possibility becomes a real threat in bad weather.

There is one other term that should not be left out in any discussion of handling or protecting oneself and others from wires that are down. This term is “feed-back.” It is a nasty term even to experienced linemen. To explain it. let us use, for example, service wires leading into a house from a pole. The bottom wire breaks off at the pole. The wire is not feeding from the pole so we may be inclined to think that the line is dead. There are two lines still serving the house. One of these carries 110 volts into the house, where the current uses a water heater or electric stove element as a conductor, and travels out of the house through the downed wire. The downed wire has just as much current in it as the wire in the air. The same thing can happen to primary lines by feeding back through transformers.

The degree of grounding, or shortcircuiting, will determine the amount of heat dissipated. It a wire carrying 2.300 volts is lying on grass or dry dirt, a high-resistance ground will result. This means that the resistance between the wire and a physical ground will be so high that little or no current will flow to ground. The grass or dry dirt becomes an insulator.

Looking at this wire, it seems harmless, no smoke or areing. However, if it is touched by a person who is grounded, a shock or electrocution is the result. How well the person is grounded will determine the degree or amount of shock they will receive.

Volt is a unit of measure for pressure, or the driving force of electricity. Ampere is the working portion, or the heat of electricity”. The higher the voltage, the more the current flow. Only one-fifth of an ampere is needed to paralyze and kill a human, if that onefifth of an ampere passes through the heart. You do not have ammeters and voltmeters with you on emergency calls, so the best thing to do is not to come in direct contact with downed conductors, nor let anyone get close enough to come in contact with one.

In setting up a safety zone around a danger area, people and vehicles should be kept back at least one span from the break. They should not be allowed under overhead conductors because the wires might be loose and the conductor might sag enough to touch the vehicle or person under it. The heat of shorted wires could cause the same wire to burn a long distance from the actual trouble. Wires lying on the ground can be whipped all the way across a street by a tie wire releasing and slack going back into a tightly sagged span, or a vehicle might hit the conductor several spans back were there might be some slack in the wire. A wire could burn in two while it is lying on the ground and curl up and roll along the ground.

Continued on page 881

Cotinued from page 765

Eye injuries can result from electric arcs. Do not look at the flashes of an electric arc. This is the same arc used in electric welding.

(To be continued)