storm tripping

[sparky-s-w]

dear fellow indulgers of the electrical disaplin, i would greatly value any ideas.

customers MCB for kitchen sockets tripped during the storm yesterday, and would not latch in for the custmer at the time. however on arival this morning, the breaker reset. all tests came out clear apart from the RCD trip time, both x1 and x5 tests triped without giving a milli second value. tried at 0 and 180, also tried at x1/2 same thing RCD tripped with no value displayed. strange as RCD hadnt rtipped with the origional fault

sockets are back on, and customer is happy, but i am not. would apreciate your thoughts.

 

[Strima]

Was it an electrical storm? Any ramp test done on RCD? Any earth leakage?

 

[sparky-s-w]

was an elec storm yes, no earth leakage, all other tests ok, the RCD hadnt triped origionaly, just the MCB, but did an RCD test as part of the course, which is when it kept tripping with no values showing on tester.

 

[Rockingit]

I'd have thought that the two most obvious contenders are, er, obvious:

1) water penetration somewhere
2) power surge / emf spike

why the RCD is now being a bit suss could be because it's now shafted (not beyond possibility it could be burnt out internally hence not tripping last night - if it's only a standard 6kA one that's nothing to a bolt of lightning)

 

[sparky-s-w]

yep i agree, my first thoughts were as you say water ingress or a strike, hadnt thought that the RCD might have beendamaged by it though. think ill get it changed anyway.

 

[Strima]

Could also depend on when the customer last tested the RCD, as we know they get tested every three months...

 

[sparky-s-w]

customer did say that the alarm went off, but breaker for that hadn't triped, so a surge is looking likely

 

[Silly Sausage]

Was the weather a bit like Newcastle yesterday?
14 secs in... BBC News - Flooding: North East hit by travel disruption

 

[sparky-s-w]

yep, was a funny old day

 

[Engineer54]

So, did to change out the faulty RCD, once you found it failed testing, ....You didn't say?? All you said was ''socket are back on, and customer happy''!!!

 

[telectrix]

customer is happy, but sparky isn't. i would advise replacing the RCD and then doing a RCD test, if similar results to the old one, then there is a circuit problem

 

[Richard Burns]

Also worth doing a check on your meter with another RCD to ensure that your meter is working OK and on the right settings, just in case you change the RCD for no reason.
However I would think it likely the RCD was damaged.

 

[MarkieSparkie]

Hi sparky, Did you remember to conduct the RCD tests with ALL loads disconnected from the RCD. A low impedance load on the RCD may drag the voltage down so quickly, that although the RCD trips, the meter is either unable to record & display a value or displays an unreliable short disconnection time. Conversely, in situations where the load has input capacitors (eg. RFI Suppression or reservoir capacitors) the voltage maybe artificially held up, causing the meter to display an unreliable long disconnection time.

 

[Knobhead]

The fact the MCB reset after a time would suggest a thermal O/L trip. Check out the RCD by all means, but have a close look at the kitchen RFC.