A fault indicator is a device which provides visual or remote indication of a fault on the electric power system. Also called a faulted circuit indicator (FCI), the device is used in electric power distribution networks as a means of automatically detecting and identifying faults to reduce outage time.

 

Overhead indicators are used to visualize the occurrence of an electrical fault on an overhead electrical system. Underground indicators, locate faults on an underground system. Often these devices are located in an underground vault. Some fault indicators communicate back to a central location using radio or cellular signals.

Basic principles

Typically fault indicators sense magnetic field caused by current flows through a conductor or cable. Some of them also use measurement of electric field caused by voltage in conductor.

History

The first fault indicators came onto the market from Horstmann (Germany) in 1946. The E.O. Schweitzer Manufacturing Company (now a division of Schweitzer Engineering Laboratories, Inc.) introduced a product to the U.S.A in 1948. 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.