Lineman (occupation)

A lineman is a tradesman who constructs and maintains electric power transmission and distribution facilities. The term is also used for those who install and maintain telephone, telegraph, and cable TV lines.

What they do

Linemen can work on either energized or 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 which 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 ensure against any accidental contact with the wire. The buckets from which linemen sometimes work are also insulated using rubber.

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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 anyway, because of possible 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 is known as backfeed. Another potential problem is de-energized wires can become energized through electrostatic induction from energized wires in close proximity. One precaution against this is to ground all the wires in a circuit to each other before working on it, hence the saying, "if it's not grounded, it's not dead."

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Incredible as it seems, live high voltage transmission lines can be worked barehanded. This is done with the lineman wearing a special conductive suit which is grounded to the live power line, creating a Faraday shield effect so the lineman is at the same potential as the energized wire, and 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.

Related Topics:
Faraday shield - Potential - Helicopter

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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.

Related Topics:
Capacitor - Insulator - Fuse

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Telephone and cable TV lines may sometimes be placed on the same 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.

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