What is an Autorecloser?

An autorecloser is a circuit breaker that is capable of resetting itself after having tripped or opened due to a line fault. These kinds of circuit breakers are typically used on main grid supplies although they are sometimes installed on industrial machine feeds. The concept behind the autorecloser is the automated resumption of electrical supplies where line faults are transient by nature. Faults include lightning strikes and bird or animal activity and would normally require manual intervention to reset, thereby leaving consumers without power for protracted periods. The autorecloser is programmed to make a preset number of attempts to resume the supply before remaining open should the fault persist.

A large proportion of overhead line faults on electrical supply grids are transient by nature and clear themselves almost immediately. Examples of these faults include lightning strikes, wind-borne objects, and animals climbing onto the lines. This type of fault is generally a once-off occurrence which requires no remedial action. If conventional circuit breakers are used, however, a technician must physically reset them before the power supply can be reinstated; often the result is consumers left without power for long periods. Autorecloser circuit breakers, on the other hand, reset automatically after a brief period and, should the fault have cleared, remain closed, thereby resuming the normal supply of power. Most are programmed to do this a number of times, typically three attempts, before staying open should the fault persist.

Autorecloser circuit breaker designs include both single and three phase types and cover most charge and latch methods such as vacuum, oil, and gas systems. The controls which drive the autoreclose function are programmable and range in sophistication from fairly simple electromechanical versions to sophisticated digital systems. Digital autoreclose systems typically include a range of additional diagnostic functions such as metering and event recorders. A wide range of breaker capacities are also available in autoreclose configurations and include line voltages from 2,400 volts to 38,000 volts or more and loads up to 1,200 amps. Typical fault current ratings on autorecloser breakers range between 500 and 12,000 amps.

These automated circuit breakers are also found in heavy industrial machines, particularly those located in remote areas, such as pumps and excavation drag lines. In these cases, autoreclose breakers are installed to counter intermittent trailing cable faults and supply overloads. In both these and grid supply environments, all personnel who may potentially be called upon to check or repair system faults should be made aware of the autorecloser status of a breaker to avoid being electrocuted should a breaker close unexpectedly.