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Secondary breakdown is a failure mode in bipolar power transistors. In a power transistor with a large junction area, under certain conditions of current and voltage, the current concentrates in a small spot of the base-emitter junction. This causes local heating, progressing into a short between collector and emitter.
A short circuit fault current can, within milliseconds, be thousands of times larger than the normal operating current of the system. [2] Damage from short circuits can be reduced or prevented by employing fuses , circuit breakers , or other overload protection , which disconnect the power in reaction to excessive current.
In an electric power system, a fault or fault current is any abnormal electric current. For example, a short circuit is a fault in which a live wire touches a neutral or ground wire. An open-circuit fault occurs if a circuit is interrupted by a failure of a current-carrying wire (phase or neutral) or a blown fuse or circuit breaker.
The effect of too high short-circuit current is discussed in the previous section. The short-circuit current should be around 20 times the rating of the circuit to ensure the branch circuit protection clears a fault quickly. Quick disconnecting is needed, because during a line-to-ground short circuit the grounding pin potential on the power ...
A circuit protection device for overhead power distribution lines which briefly interrupts a circuit when a fault is detected, then restores the circuit in the expectation the fault has cleared. autotransformer A transformer where the primary and secondary circuits share some of the transformer windings. availability factor
SCMVA is defined as a product of the voltage before the 3LG fault and the current that would flow after the fault (this worst-case combination will not happen in practice, but provides a useful estimation of the capacity of the circuit). SCMVA is also called a short circuit level (SCL), [3] although sometimes the term SCL is used to designate ...
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 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 circuit breaker, 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 ...