How can i detect earth fault?

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xxtigerxx

Joined: 05 Jun 2001
Posts: 240
Helped: 5
Location: Greece

26 Jul 2006 13:55 dc earth fault

do you know any circuit so i can detect earth fault.

Razz

IanP

Joined: 05 Oct 2004
Posts: 6490
Helped: 1542
Location: West Coast

26 Jul 2006 14:21 dc earth fault relays

In AC circuits you can use RCDs (residual current device) or GFM (ground fault monitor) .. more info on both can be easily found googling ..

In DC circuits so far I haven't come across any reliable circuit ..

Regards,
IanP

jonw0224

Joined: 22 Nov 2004
Posts: 199
Helped: 28
Location: USA

27 Jul 2006 4:16 dc earth fault relay

For DC (ungrounded system), I have seen battery chargers with two bulbs wired in series from the positive terminal to the negative terminal. The bulbs are rated for the full DC voltage and divide the voltage fairly evenly and both glow dim.

Now, connect the common node (between the two light bulbs) to earth. If either the negative terminal or the positive terminal get shorted to ground, one bulb will go out and the other will glow bright (and depending on which one, you know where the fault is). In fact, if the fault is a soft fault (with some impedance) one bulb will glow brighter than the other. This is a good visual detection (but could easily be modified to generate an alarm etc).

Note, this is a specific case (ungrounded DC system, like on a car). Hope that helps some.

-jonathan

zenisle

Joined: 11 Sep 2005
Posts: 131
Helped: 2

27 Jul 2006 4:20 car earth fault

onnect the common node (between the two light bulb

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mcmangelo

Joined: 27 Jun 2009
Posts: 1
Location: Saudi Arabia

27 Jun 2009 19:37 how to detect earth fault

Its really hard to locate the actual location of earth fault in live condition of a DC power supply distribution board, specially with each circuit which has its own separate distributed load.
In one of the distribution board a DC Earth Fault relay was connected, this relay has a various current setting for supervisory of earth fault ranging 1mA up to 10mA.
We encountered earthfault in the system registering a 4.5mA fault, which is so hard to determine the location since we could not switched off/isolate the individual mcb's in the distribution board that could lead loss of power supply on each circuits. These circuits were used for switchgear control system, SCADA and Emergency lighting.
Is there a way to exactly determine which circuits in the distribution board has the earthfaulted connection?
DC earthfault has damaged some of our Battery Charger/Rectifiers.