I am an electrical power engineer and arranged power system
for a data center, I installed MCB, ELCB and erthing system
TN-C-S.
But some times several ELCBs Disconnect circuits at the
same time! what may be the reason? (the ELCBs are 25A ,30mA)

Answer Posted / pillay

the choice of 30 ma is correct,
or in fact we should be able to
decide what ma rating we want
to choose where.
It could be the fault current was
quite big but fault current could
not be grounded fast enough resulting
in the current floating into other
neighbouring cct resulting in triggering
of the elcb,s.The other solution would
be checking the grounding connections from
the earth pit to upwards and also the actual
earth resistance measurements.

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