Why two main buses and one transfer bus scheme not using
for 400kV switchyard

Answer Posted / jkrocks

DMT scheme is used earlier in 400kV System but all new 400kv ss are made on one & half breaker scheme. it has many advantages over DMT scheme.
more reliable than DMT each time line or ICT remain connected through both buses I & II, reduces numbers of confusing isolator in system, reduce additional bus.
If one bus trip due to any fault , lines are transformer connected to that bus remains charged through another bus by means of Tie CB.

Only disadvantage is that this system require three breaker for 2 lines or transformer.
But It is nothing against lots of advantages of One & Half Breaker Scheme.

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