These typically require a separate power source, such as a battery, although some high-voltage circuit breakers are self-contained with current transformers, protective relays, and an internal control power source. Circuit breakers for large currents or high voltages are usually arranged with protective relay pilot devices to sense a fault condition and to operate the opening mechanism. Typically, the heating and/or magnetic effects of electric current are employed. In small mains and low voltage circuit breakers, this is usually done within the device itself. The circuit breaker must firstly detect a fault condition.

OperationĪll circuit breaker systems have common features in their operation, but details vary substantially depending on the voltage class, current rating and type of the circuit breaker. By 1935, the specially constructed circuit breakers used at the Boulder Dam project use eight series breaks and pressurized oil flow to interrupt faults of up to 2,500 MVA, in three cycles of the AC power frequency. Simple air-break manual switches produced hazardous arcs when interrupting high voltages these gave way to oil-enclosed contacts, and various forms using directed flow of pressurized air, or of pressurized oil, to cool and interrupt the arc. Interconnection of multiple generator sources into an electrical grid required development of circuit breakers with increasing voltage ratings and increased ability to safely interrupt the increasing short circuit currents produced by networks. Stotz's invention was the forerunner of the modern thermal-magnetic breaker commonly used in household load centers to this day. Hugo Stotz, an engineer who had sold his company to BBC, was credited as the inventor on DRP ( Deutsches Reichspatent) 458392.

A modern miniature circuit breaker similar to the ones now in use was patented by Brown, Boveri & Cie in 1924. Its purpose was to protect lighting circuit wiring from accidental short circuits and overloads.

6.10 Carbon dioxide (CO 2) high-voltage circuit breakersĪn early form of circuit breaker was described by Thomas Edison in an 1879 patent application, although his commercial power distribution system used fuses.

6.9 Disconnecting circuit breaker (DCB).

6.8 Sulfur hexafluoride (SF 6) high-voltage circuit breakers.

6.4 Magnetic-hydraulic circuit breakers.

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