RCB "not tripping" or "false tripping"

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isurunalaka

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have you ever encountered any faulty RCBs with issues like "not tripping" or "false tripping"?

if RCB was ok(not faulty) after troubleshooting for above 2 cases, what were the reasons which cause RCB not to trip of to trip unnecessarily?

thanks
 

A RCB can go faulty as any electronic component can. Have you fully tested the "faulty" one with a pulsed fault current. False tripping does happen with working and good RCBs . I believe the trip is caused by bad switching on the grid. The problem I think is tied up with the capacitance down stream of the RCB, as on a noisy switch of the grid, you get a large capacitive charging current down the live conductor, but as the neutral is tied to earth, there are no volts so no current. Hence a large current unbalance which trips the RCB.
Frank
 
I have had both.

False tripping due to RF pickup (Mainly a problem on the sort that have built in electronics), and I once had one completely fail to trip on a pulsating DC fault (Turns out you can get a special variant that does trip under these conditions).

Regards, Dan.
 

thanks for the input. but what do you mean by "by bad switching on the grid"?
 


thanks for the feedback. what do mean by "pulsating DC fault"? when can that happen? with what appliances?
 
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"Bad switching on the grid", I don't know exactly what it is I believe it was caused by a faulty (?) tap changer near to where I lived, because about twice a year Our domestic 30 mA RCD used to trip about 5 30 PM on a Friday night when the local industrial site closed down for the weekend. I changed it for a 100 mA one and it cured the problem.
Frank
 

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