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simple sketch of electricity supply

We live in a community setup where a main feeder cable comes in from the street (city supply) and then is split up to each housing unit (blue on sketch). Between this point where the electricity is distributed and each housing unit there is a supply cable that then terminates into the house DB.

Now that you have some background - the cable indicated as yellow on the sketch was very slightly damaged during excavation. The earth leakage in the blue distribution tripped though. A repair was done on the yellow cable - resin join kit. However the distribution board in the housing unit trips randomly.

My question is two fold, if the cable still had damage where would the trip occur at the blue earth leakage or at the housing unit? Is there any way to test where the fault is causing the trip?

Thanks for your time.

  • Do the two earth leakage breakers have different trip thresholds? Was the feeder to the housing unit insulation tested (meggered) post-repair? – ThreePhaseEel Aug 5 '17 at 12:23
  • Also, can you tell if the ELCB trip is due to leakage or due to overcurrent? Tried putting a clampmeter on hot/neutral (together) coming out of the ELCB? – ThreePhaseEel Aug 5 '17 at 17:04
  • Yes the insulation was tested I have no idea what causes the trip - have not tried a clamp meter – JusAlwaysWondering Aug 6 '17 at 17:28
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You probably need to submit more detail to get a complete answer to your problem, but I will try and answer from the information you have given up to this point.

First I can't think of a situation or reason how an problem upstream would trip a downstream breaker. So the trip would occur at the main distribution area or just fault out or burn up at the original damage.

Second the you need to have an ammeter and check the amount of current flow at the breaker tripping in house DB.

Now here are some questions you need to answer to get further information. Which breaker is tripping in house DB? Is it the main or one of the branch circuits? Did you have breakers tripping before the repair? How old is your system? Has anyone tested the voltage at each phase and the neutral to ground (disconnected)?

Hope this helps

  • This is almost assuredly a ground-fault detection action. They're real into whole-house GFCIs over there in Europe, although they have fairly high thresholds so you definitely won't enjoy a ground-fault experience none too much! Best argument ever for an auxiliary battery solar system if you ask me! Having your fridge knock out due to a whole house trip, no thanks. – Harper - Reinstate Monica Aug 5 '17 at 17:27
  • The main breaker is tripping main breaker house tripped before the repair - so the cable was physically damaged a week before the repair was done The breaker in the house did not trip when the actual damage was done, only the breaker in the main First trip in the house occurred the day before repair, this day the cable was inspected breaker manually turned off during (distribution box). The house did not trip on the day of the repair. The day after the repair the breaker in the house tripped - although no interaction with the cable took place that day. – JusAlwaysWondering Aug 6 '17 at 17:38
  • I am starting to suspect the geyser in the house - it was replaced less than a month ago and it is the only other thing that changed recently Spoke to electricians irl and both think it should trip at the distribution box if a fault was on the cable, both seem to think the fault is in the house – JusAlwaysWondering Aug 6 '17 at 17:46

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