Subject: Sporadic tripping of Residual Current Circuit Breaker (RCCB) /Earth Leakage Circuit Breaker (ELCB).
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????