Answer / rishi

first of all who told u that main and transfer bus is not used in 400 kv substation.This scheme is used in many substations.

Answer / naresh.devarakonda

one and half breaker scheme is more reliable, simple
operation and reduces the no. of isolators, bus.

Answer / furqan ahmad

in one and halfbreker scheme scheme both breaker and bus
maintenance is possible.even though this scheme is costly
as compared to other schemes but becoz of reliability and
redundancy it is usually used for 400 kv switchyard

Answer / 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.

Answer / teju

one and half circuit breaker scheme is more reliable than
other schemes, simple operation and reduces the no. of
isolators, some electrical parameters & it is easy to handle.

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