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In transmission line faults, roughly 5% - 10% are asymmetric line-to-line faults. [2] line-to-ground fault - a short circuit between one line and ground, very often caused by physical contact, for example due to lightning or other storm damage. In transmission line faults, roughly 65% - 70% are asymmetric line-to-ground faults. [2]
A residual-current device (RCD), residual-current circuit breaker (RCCB) or ground fault circuit interrupter (GFCI) [a] is an electrical safety device that interrupts an electrical circuit when the current passing through a conductor is not equal and opposite in both directions, therefore indicating leakage current to ground or current flowing to another powered conductor.
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.
(The principle of double fault to danger requires either basic and additional insulation to fail or basic insulation and the connection to the protective earth to fail simultaneously before danger arises.) A typical example for a PELV circuit is a metal cased computer with a Class I power supply.
A ground fault protection relay must trip the breaker to protect the circuit before overheating of the resistor occurs. High-resistance grounding (HRG) systems use an NGR to limit the fault current to 25 A or less. They have a continuous rating, and are designed to operate with a single-ground fault.
Ground-fault circuit interrupter (GFCI) protection is required on receptacles in wet locations and locations where there exists an easy path for fault current to travel to earth. This includes all receptacles intended to service kitchen counter surfaces, crawl spaces at or below grade level, basements, garages and accessory buildings, bathrooms ...
Presence of uninterrupted ground fault may pose a significant safety risk: if the current exceeds 4 A – 5 A an electric arc develops, which may be sustained even after the fault is cleared. [27] For that reason, they are chiefly limited to underground and submarine networks, and industrial applications, where the reliability need is high and ...
A line-to-ground fault will cause a voltage sag until the protective switchgear (fuse or circuit breaker) operates. [2] [11] Some accidents in power lines such as lightning or a falling object can cause a line-to-ground fault. [11] Sudden load changes or excessive loads [11] Depending on the transformer connections, transformers energizing [6]