Search results
Results from the WOW.Com Content Network
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 ...
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 .
While the fault current from a distribution or transmission system can usually be calculated or estimated with precision, calculation of the earth grid resistance is more complicated. Difficulties in calculation arise from the extended and irregular shape of practical ground grids, and the varying resistivity of soil at different depths.
While voltage and current on the protective earth conductor is usually fault current from a live wire, this is not always the case, thus there are situations in which an ELCB can nuisance trip. When an installation has two connections to Earth, a nearby high current lightning strike will cause a voltage gradient in the soil, presenting the ELCB ...
This allows calculation by an industrial customer of its internal fault levels within its plant. If the prospective short-circuit current from the utility source is very large compared to the customer's system size, an "infinite bus" is assumed, with zero effective internal impedance; the only limit to the prospective short-circuit current is ...
The power loss per square meter in the ground is proportional to the square of the transmitter current density flowing in the earth. The current density, and power dissipated, increases the closer one gets to the ground terminal at the base of the antenna, [14] so the radial ground system can be thought of as providing a higher conductivity ...
The leakage reactance (usually about 5 to 10% of the full load impedance) helps limit both the magnitude and rate of rise of the fault current. Short-circuiting a 3000 farad supercapacitor through an iron nail resulted in a 1000 amperes current. This caused the iron nail to melt, eject sparks, and eventually break, becoming an open circuit.
Provide a relatively low-impedance path to ground, thereby maintaining the system neutral at or near ground potential. [3] Limit the magnitude of transient over voltages when restriking ground faults occur. Provide a source of ground fault current during line-to-ground faults. Permit the connection of phase-to-neutral loads when desired. [2]