What is a ground fault?

Question

In high voltage power distribution terms, what does "ground fault" mean?

angryman1... you are funny!

Answer 1

I work on diesel - electric locomotives .The power system and components ( high voltage and amperage ), such as the traction motors,are protected by a 'ground relay ' that 'trips' and cuts power when a ground fault exists.
In our terms a 'ground fault' means that the negative or positive cables or components are grounded, meaning the insulation is bad and the circuit touches the body at that bad spot, referred to as ground. (ground is referred to as the general mass of earth ) and the locomotive is basically on earth through the wheels on the rails.
We use a 1000 volt meggar meter , one lead coupled to the positive or negative power circuit, and the other lead coupled to ground, and then we send 1000 volts into the system and it indicates/reflects to what extent the circuit is grounded and by isolating different parts of the circuit we can detect exactly where the ground fault is situated by reading the power schematic .(electrical drawing or plan )Hope it explains enough.

Answer 2

The voltage of the system means nothing where a ground fault is concerned, other than that faults at hgiher voltages result in more damage.

A ground fault occurs when there is a conducting path between a "live" element (such as a wire or terminal connection point) and a "grounded" element (such as a motor frame, a structural beam, or a cabinet enclosure surface).

Normally this can occur as either a continuous fault (i.e. it simply doesn't go away ... a live cable is making contact with a structural member, for example) or it is an instantaneous condition (tracking occurs to temporarily produce a path from live to ground, but the passage of current from one potential to the other wipes out the path). Another way to look at it is that there is a breakdown of the insulation used to separate "live" from "ground".

If one is indicated, it is best to shut down the equipment and find the fault - before irreparable damage to either equipment or personnel occurs.

Answer 3

A residual current device (RCD), or residual current circuit breaker (RCCB), is an electrical wiring device that disconnects a circuit whenever it detects that the flow of current is not balanced between the phase ("hot") conductor and the neutral conductor. The presumption is that such an imbalance may represent current leakage through the body of a person who is grounded and accidentally touching the energized part of the circuit. A shock, possibly lethal, is likely to result from these conditions; RCDs are designed to disconnect quickly enough to prevent such shocks.

In the United States and Canada, a residual current device is also known as a Ground Fault Circuit Interrupter (GFCI) or an Appliance Leakage Current Interrupter (ALCI). In Germany, one is known as a FI-Schalter.

click here:http://en.wikipedia.org/wiki/Residual-current_device

Answer 4

It means a short circuit to what's called safety ground or earth ground. That long third prong on an electric plug connects to a metal rod that's in the ground. It directs current to earth rather than your body, hopefully.

Answer 5

Commonly used around water. It ensures that people don't get fried by allowing themselves to be "the path of least resistance."

They are set to trip (cut power) when there is a sudden drop in resistance. Much to the dismay of many a suicidal person.