RCB "not tripping" or "false tripping"

[isurunalaka]

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

 

[chuckey]

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

 

[Dan Mills]

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.

 

[isurunalaka]

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

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

 

[isurunalaka]

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 feedback. what do mean by "pulsating DC fault"? when can that happen? with what appliances?

 

[chuckey]

"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