Potential circuit faults - RCD/ Megger

[daveb]

Hi folks,

In your opinion, do you think there would ever be a situation where an RCD (presuming it worked) would not pick up a problem that a megger test would? i.e an RCD would trip if there was ever a L-E, N-E or L-N fault

 

[telectrix]

for a 30mA RCD it would take a leakage resistance 0f approx. 8000 ohms to trip it. this would be picked up on a IR test. L-N faults would not trip the RCD. the OCPD handles that.

 

[Pete999]

What megger test are you referring to? IR, RCD, ELI, Continuity.

 

[Wilko]

The IR test is much more sensitive than the RCD ...

 

[Midwest]

If a neutral earth fault is missed, then sometimes that can cause the RCD not to function.

 

[daveb]

good answers, thanks. Yes - was talking about an IR test

 

[The Ghost]

Wrong type of RCD can suffer from hysteresis and not function. Would not be noticed while in use but would trip when doing IR and nothing plugged in.

 

[PEG]

Hysteresis...the difference in length,between a pushed rope,and a pulled one (an old Physics teacher's quip...)