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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.
Hot is any line or neutral conductor (wire or otherwise) connected with an electrical system that has electric potential relative to electrical ground or line to neutral. Ground is a safety conductor with a low impedance path to earth. It is often called the "ground wire," or safety ground. It is either bare or has green insulation. [1]
Each phase of the circuit is run in a separate grounded metal enclosure. The only fault possible is a phase-to-ground fault, since the enclosures are separated. This type of bus can be rated up to 50,000 amperes and up to hundreds of kilovolts (during normal service, not just for faults), but is not used for building wiring in the conventional ...
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.
In a high resistance grounded distribution system, a feeder may develop a fault to ground but the system continues in operation. The faulted, but energized, feeder can be found with a ring-type current transformer collecting all the phase wires of the circuit; only the circuit containing a fault to ground will show a net unbalanced current. To ...
NEMA L14 are three-pole and ground connectors rated for 125/250 V. Intended for three-pole, four-wire hot-hot-neutral-ground circuits with a nominal supply voltages of 240 or 208 V hot-to-hot and 120 V hot-to-neutral. These connectors are common on household backup generators, and on racks of power amplifiers in large audio systems.
When current flows from a line conductor to an earth wire, as is the case when a line conductor makes contact with an earthed surface in a Class I appliance, an automatic disconnection of supply (ADS) device such as a circuit breaker or a residual-current device (RCD) will automatically open the circuit to clear the fault. [7]
This three-wire single-phase system is common in North America for residential and light commercial applications. Circuit breaker panels typically have two live (hot) wires, and a neutral, connected at one point to the grounded center tap of a local transformer. Usually, one of the live wires is black and the other one red; the neutral wire is ...