Answer / iamdon

In ACB(Air Circuit Breaker) arc extinguishing and
insulating is carried out in air medium where as in VCB
(Vaccum Circuit Breaker)it is carried out in low vaccum.
At high voltages, air inonises and losses its dieectric
properties which makes the ACB unsuitable at HT.Thats why
ACB is used at LT not at HT.

Vaccum can suastain high voltage(not ionises) and does not
losses its dielectric properties which makes the VCB
suitable for HT.

Since VCB is costlier and require more maintenance as
compared to ACB.So VCB is not employed for LT where cheaper
option as ACB is available.

Author:arbelectbit@yahoo.com

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