Main MCB tripping

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Main MCB tripping

Postby jack9 » Mon Dec 04, 2017 3:37 pm

hello

I have a 4 pole MCB (including neutral) installed as the main mcb in the house control panel. from the main mcb to the transformer there are no tall trees. outside, from the transformer to where it connects with the main grid and along the soi, there are many tall trees flanking the way and many of them their branches are 20-30cm from the bare uninsulated overhead wires.

i have been experiencing sporadic tripping of the main mcb for the past 2-3 years. during the dry season, it maybe trip once every 5 weeks and during the rainy season maybe once every 2 weeks. after tripping, it can be reset almost immediately( or maybe within 1-2 minutes)

few months ago, when PEA trimmed the trees for an event, i have enjoyed about 8-10 weeks on non-tripping until 2 days ago. after having the PEA technician come down and test the control panel and everything is ok.

i asked him could it be the tree branch touching the bare wire and causing my house breaker to trip. but he denied saying that if the tree branch were to touch the bare wire, it will cause power loss for only a few seconds or trip their own external mcb, but DEFINITELY it will NOT trip my house breaker.

i can only find 1 report online which recommends a clearance of 2m and the possibility that breaker may trip if not followed. but it does not specify this tripping will occur with the PEA(external) mcb or the house mcb. there are many reports which are specific on minimum clearance distance, but none of them talk about tripping of house mcb if the branches do come into contact with the wire.

may i have your opinion? thanks
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Re: Main MCB tripping

Postby Klondyke » Mon Dec 04, 2017 6:54 pm

In my view what the PEA man said is correct. It can be some other problem inside the house which occurs only sometimes, not permanently. Or your power demand is on the limit of the MCB. Or the MCB tripping function is not always correct.
BTW, the overhead lines of 400V are mostly not bare but insulated. Perhaps in your area are bare ones?
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Re: Main MCB tripping

Postby Roger Ramjet » Mon Dec 04, 2017 9:25 pm

jack9 wrote:i have been experiencing sporadic tripping of the main mcb for the past 2-3 years. during the dry season, it maybe trip once every 5 weeks and during the rainy season maybe once every 2 weeks. after tripping, it can be reset almost immediately( or maybe within 1-2 minutes)

few months ago, when PEA trimmed the trees for an event, i have enjoyed about 8-10 weeks on non-tripping until 2 days ago. after having the PEA technician come down and test the control panel and everything is ok.

I had the same problem with my EGAT power. After they had cleared the trees they also replaced the screws holding the cables in place at the box and that totally fixed the whole problem. The first problem was the trees, the second problem the cables were not properly pushed into the housing on the meter and when they tried to tighten them, they found one screw had stripped its thread.
I hope that helps.
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Re: Main MCB tripping

Postby Sometimewoodworker » Tue Dec 05, 2017 8:01 am

jack9 wrote:hello

I have a 4 pole MCB (including neutral) installed as the main mcb in the house control panel. from the main mcb to the transformer there are no tall trees. outside, from the transformer to where it connects with the main grid and along the soi, there are many tall trees flanking the way and many of them their branches are 20-30cm from the bare uninsulated overhead wires.

i have been experiencing sporadic tripping of the main mcb for the past 2-3 years. during the dry season, it maybe trip once every 5 weeks and during the rainy season maybe once every 2 weeks. after tripping, it can be reset almost immediately( or maybe within 1-2 minutes)

may i have your opinion? thanks


I would check and monitor the voltage on each of the 3 phases. It is possible that there is excessive power draw on one of them and that could be a contributing cause. You may need to balance your usage and anyone else's outside your property on one of them.

Assuming that your own usage is balanced
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Re: Main MCB tripping

Postby jack9 » Tue Dec 05, 2017 1:19 pm

thanks. i opened up the panel again and managed to identify a faulty circuit :)
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