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Loose or poor connections in traditional electrical accessories and switchgear can cause heat to develop capable of starting a fire. This problem is known as High Resistance Connection (HRC) and safety devices such as fuses and Residual Current Devices (RCDs) are unable to disconnect the electrical supply because they cannot detect a HRC.
A ground conductor only carries significant current if there is a circuit fault that would otherwise energize exposed conductive parts and present a shock hazard. In that case, circuit protection devices may detect a fault to a grounded metal enclosure and automatically de-energize the circuit, or may provide a warning of a ground fault.
Such devices may be found in the form of either a circuit breaker, known as an earth-leakage circuit breaker (ELCB), or built into a socket (aka receptacle). Voltage-operated ELCBs can still be found in the wild, though these largely fell out of favour after the invention of the current-sensing based RCD (aka GFCI) technology.
A residual-current device (RCD), residual-current circuit breaker (RCCB) or ground fault circuit interrupter (GFCI) [a] is an electrical safety device, more specifically a form of Earth-leakage protection device, that interrupts an electrical circuit when the current passing through line and neutral conductors of a circuit is not equal (the term residual relating to the imbalance), therefore ...
In a "ground fault" or "earth fault", current flows into the earth. The prospective short-circuit current of a predictable fault can be calculated for most situations. In power systems, protective devices can detect fault conditions and operate circuit breakers and other devices to limit the loss of service due to a failure.
Circuit-breakers can be placed at portions of a circuit in series to the path of current it will affect. If more current than expected goes through the circuit-breaker, the circuit breaker "opens" the circuit and stops all current. A fuse is a common type of circuit breaker that involves direct effect of Joule-overheating.
A resistor removed from a high voltage tube circuit shows damage from voltaic arcing on the resistive metal oxide layer. Resistors can fail open or short, alongside their value changing under environmental conditions and outside performance limits. Examples of resistor failures include: Manufacturing defects causing intermittent problems.
A circuit breaker is an electrical safety device designed to protect an electrical circuit from damage caused by current in excess of that which the equipment can safely carry (overcurrent). Its basic function is to interrupt current flow to protect equipment and to prevent fire.