Sporadic tripping of Residual Current Circuit Breaker (RCCB) /Earth Leakage Circuit Breaker (ELCB)

[csubhas]

I am an electrical engineer myself and am facing an unexplainable technical issue at my residence. The complete electrical wiring (input 220V, 50HZ, single phase) at home has been carried out by separating the power consuming circuits powering Air conditioner, refrigerator, washing machine, microwave, pump etc. from the light power consumers like lights, fans, 5A sockets etc. The power circuits have their own adequately rated single pole Miniature circuit breakers (MCBs) protected by a RCCB/ELCB, 63 A, 2 pole with fault leakage current of 300 mA whereas the light power circuits have their own MCBs and another ELCB with leakage current 30 mA.

Since some days the power circuit ELCB, 300mA is tripping although all the MCBS remain in ON position. It is possible to reset the ELCB immediately until it happens again sometimes after 2-3 days or even a few hours. I have tried to trace the problem by physically disconnecting (pulling the plugs out) the loads one by one. I could not come to any conclusion and the tripping continues to happen sporadically. The light power circuits have no such problems with the 30mA ELCB remaining ON always.

To rule out any problem with the ELCB itself, I replaced it with a new one but the problem persists.
The wiring in my house is 35 years old. Will wiring insulation deterioration over a period of time cause this malfunction?
Any technical solutions????

 

[RedSnake]

One way of doing it is
You turn of the incoming power feed.
Then you disconnect the jumper that connects the Earth to the Neutral.
Check there is no connection (ohm measure).
Turn off all breakers but one, connect the phase to the neutral.
And use a megger between the Earth and the (Phase/Neutral) for that breaker to control if there is leakage to earth.
Buy connecting the phase and neutral together there is no potential difference in the machinery between phase and neutral so they want break.
Then you check the breakers one by one only having one on at the time.
That way you may narrow down the problem.

Best Regards A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[che12345]

Dear Mr. csubhas (Electrical)
"... the power circuit ELCB, 300mA is tripping although all the MCBS remain in ON position. It is possible to reset the ELCB immediately until it happens again sometimes after 2-3 days or even a few hours. I have tried to trace the problem by physically disconnecting (pulling the plugs out) the loads one by one. I could not come to any conclusion..."
1. I am of the opinion that:
a) ELCB [300mA] is adequate to handle the sum of all the leakage currents of {Power] loads. When the problem is solved, you may consider to replace it with a [30mA] for life and fire protection.
b) the wiring 35years, insulation deterioration over a period of time cause this malfunction, is unlikely; as the [Lighting] circuits with 30mA is not causing any problem.
2. When all the plugs are removed but tripping persists shows the problem is [not caused by any faulty load]. It is between the ELCB , MCB and up the the sockets outlets.
3. Carry out an insulation resistance test with 500V tester between Line to earth, Neutral to earth and Line to neutral. Attention: switch on all the power MCBs including the switch on the socket outlets, but with plug removed. In general, the insulation resistance shall be higher that 1M Ohm.
4. If the resistance is low, dismantle all socket outlets to check for any dirt , insect or water [moisture] that bridge to earth or any carbon trace.
This frequently happen on socket outlets in the kitchen and installed outdoor.
5. This symptom is typical of a high resistance flash-over any wet gap or dirt or any dead insect inside the socket outlets.
Che Kuan Yau (Singapore)