Sunday, April 1, 2012

Job Description for Electrical Lineman Duties

Duties of an Electrical Lineman

See also: Hot stick and Live-line working

Lineman replacing a transformer, wearing protective gear, including rubber gloves and sleeves
Power linemen can work on either electrically energized (live) or de-energized (dead) power lines. When working with energized power lines, linemen must use protection to eliminate any contact with the energized line. Some distribution-level voltages can be worked using rubber gloves. The limit of how high a voltage can be worked using rubber gloves varies from company to company according to different safety standards (often negotiated in the union contract) and local laws. Voltages higher than those that can be worked using gloves are worked with special sticks known as hot-line tools, with which power lines can be safely handled from a distance. Linemen must also wear special rubber insulating gear when working with live wires to protect against any accidental contact with the wire. The buckets linemen sometimes work from are also insulated with fiberglass.
Even de-energized power lines can be hazardous, owing to the complex nature of the electrical system. Even though one circuit may be ostensibly shut off, that circuit may still be conducting electricity from an interconnection with other live circuits. Thus, care must be taken to ensure that all possible sources of power to a circuit are removed. This can be especially dangerous when transformers are involved in the connection to another circuit, or one circuit is fed by more than one other circuit. For example: A higher-voltage distribution level circuit may feed several lower-voltage distribution circuits, using step down transformers. A step down transformer can also act in reverse as a step up transformer. If the higher voltage circuit is de-energized so it can be worked on, but any one of the lower-voltage circuits connected to it via a transformer remains energized, the transformer will convert the power in the lower-voltage circuit back to the higher voltage, and the higher voltage circuit will remain energized. This rarely[1] occurs after destructive storms such as hurricanes have damaged the local primary lines and someone wires a generator into their house wiring incorrectly (without an isolation switch). This is known as backfeed. Another problem can arise when de-energized wires become energized through electrostatic or electromagnetic induction from energized wires in close proximity. One precaution against this is to connect all the wires in a circuit to each other and to ground before working on it, hence the saying, "if it's not grounded, it's not dead."
Incredible as it seems, live high voltage transmission lines can be worked barehanded. The lineman must be isolated from the ground by using an insulated bucket truck or other method. The lineman wears special conductive clothing that is connected to the live power line, at which point the line and the lineman are at the same potential, allowing the lineman to handle the wire safely. Such work is often done from helicopters and is considered a highly specialized area of line work; few linemen have the special training to perform it. Barehanded live-wire work can theoretically be done at any voltage, but because better protective means are available for lower voltages, it is only used for transmission-level voltages and sometimes for the higher distribution voltages. Live wire work is extremely common on low voltage distribution systems within the UK as all linesmen are trained to work 'live'. Live wire work on high voltage distribution systems within the UK is carried out by specialist teams. These teams are sometimes referred to as 'Hot Glove' teams.
Linemen may perform a number of tasks associated with power lines, including installation or replacement of capacitor banks, distribution transformers on poles, insulators, fuses, etc. Because most of these devices are heavy and irregularly shaped, linemen and their ground crews must have a good knowledge of rigging techniques, use of ropes, knots, and lifting equipment. These skills may have to be adapted to primitive conditions where almost all work is done by hand, with tools and material that are carried to the worksite. Such conditions are common in rural or mountainous areas that are inaccessible to trucks. The public seldom witnesses this type of work, which leads to the misconception that the occupation consists predominantly of working from a bucket truck on paved streets.
Telephone and cable TV lines may sometimes be placed on the same utility poles as electric distribution circuits. They are placed below the electric lines so telephone and cable TV linemen can work those lines without potential contact with high-voltage electricity.
Not all who work in outdoor tower construction or wire installation are linemen. A crew of linemen will also include several helpers, known as groundmen or grunts. They help with the on-the-ground tasks needed to support the linemen, but may not do any work off the ground, nor any work that involves electrical circuits. Telephone linemen install cables above and below ground but, since telephone cables have many more conductors than power cables, cable splicers splice them.

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