rcbo tripping before ramp test is complete

[matt12321]

hey all

i was wondering what reason would be behind an RCBO tripping out before the ramp test has finished and comping up with trp?

thanks

 

[trev]

Not sure what you mean with"before the ramp test is finished". The whole purpose of the ramp test is to find out what current will cause the device to operate, when your meter comes up with trp it should have some more info on there for you.

 

[matt12321]

what i mean is when i drop my test leads on the rcbo and press test. the rcbo will then trip out and the meter will say trp on the screen giving no result. the tester its a megger mft1552

ive changed the rcbo as well

all other rcbo's trip within in limits

 

[trev]

Why are you ramping it?

 

[Darkwood]

You are getting confused here with X.5 / X1 / X5 test and ramp testing you shouldn't need to ramp test a rcd unless you are trying to resolve tripping issues.

 

[matt12321]

i am trying to resove tripping issues

 

[Octopus]

Sounds like you need to unplug everything on the circuit and do an IR test on the circuit

 

[trev]

i am trying to resove tripping issues

So there's nuisance tripping on one RCBO?
What happens on the half test? If it's tripping immediately on a ramp I'd expect it to be but as Murdoch said have you made sure that all loads are removed and the IR is ok?

 

[matt12321]

i have and the reading was appauling between n and e, also all 27 lights have their own joint boxes burried under a garden spanning over 100 meters.

 

[matt12321]

to add to the last reply between neutral and grey (spare core), which will be used as a live is also down, which has nothing connected to it as of yet

 

[telectrix]

probably tripping due to fault on circuit and 1552 is aborting test.

 

[Darkwood]

Leave the garden lighting circuit off (physically disconnected)for a week if it stops tripping then probably water ingress in the fittings or joint.

 

[trev]

Disconnect the circuit completely and test the RCBO.

 

[matt12321]

well thats what i thought, but i sealed them pretty well in galv boxes covered in magic gel, been ok since christmas and had a lot of rain in that time

 

[matt12321]

so could that also be giving me 262v on a cable thats not connected

 

[Octopus]

i have and the reading was appauling between n and e, also all 27 lights have their own joint boxes burried under a garden spanning over 100 meters.

And you are wondering why the RCD tripped. Disconnect the circuit from the RCD and re-test

 

[matt12321]

the circuit is disconnected thats what im saying

 

[trev]

So this immediate tripping on a ramp is after you have disconnected the circuit completely? Also the cables are failing their IR?
You have a couple of problems in this scenario.

 

[Octopus]

Whats your Ze like?

 

[matt12321]

correct. so what would cause the rcbo to trip? earth leakage? induced voltage? earth acting as a neutral somwhere