Fault indicator

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A fault indicator is a device which provides visual indication of an electrical fault. They are used in electric power distribution networks as a means of automatically detecting and identifying faults.

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[edit] Basic principles

During an electrical fault on a grounded system, additional current flows through a conductor, which is picked up by the fault indicator causing a state change on the target flag, LED, or remote indication device. Ground fault indicators for ungrounded systems sense the vector sum of the current and look for an imbalance indicating a fault on one or more of the three phases.

[edit] Types

[edit] Overhead

Overhead indicators are used to visualize the occurrence of an electrical fault on an overhead electrical system.

[edit] Underground

Underground indicators are used to visualize the occurrence of an electrical fault on an underground electrical system. Often these devices are located in an underground vault. Some vendors provided a wireless interface to eliminate the need of entering the underground vault in order to check the status of the indicators.

[edit] History

The first fault indicators came onto the market from E. O. Schweitzer Manufacturing (USA) and Horstmann (Germany) in 1948-1950. The first fault indicators were manual reset devices. Later fault indicators automatically reset on system restoration or after a set period of time. More recent fault indicators communicate their status (tripped or reset) via cell signal or radio to a central station, handheld device, or pole-mounted receiver.

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