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We use ungrounded DC system (220V/110V) for control and
protection system in substations etc. Suppose we have long
2 core DC cables running from our DCDB in control room to
the load (length of around 2 to 3 km). Do we need to
protect these long DC cables from earth leakages or not? If
yes how?
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Answer Posted / krishna
Usage of differential relay for 220V/110V is not an
economical idea. Differential protection is the costlier
protection. DC Cables should be protected from earthleakage
bacause of which voltage differences occurs and trips the
circuits due to large variations. I suggest to go for
MCCB/MCB of required rating which trips the circuit when
earth leakage occurs.
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