8. There are two identical buses and two circuit
breakers per circuit are used. In normal state both
the buses are energized. Any circuit breaker can be
removed for maintenance without interruption of
the corresponding circuit.
the failure of one of the two buses does not
interrupt any circuit can be fed from the remaining
bus.
The substation with this configuration requires
twice as much equipment as single bus scheme.
This scheme has high reliability. But due to more
equipment this scheme is costly and requires more
space.
9.
10. In Main and Transfer Bus System every feeder is
directly connected to main bus via circuit breaker and
isolators and also connected to transfer bus through an
isolator.
The isolator between transfer bus and feeder line is
called bypass isolator.
There is one bus coupler couples transfer bus and main
bus through a circuit breaker and associated isolators
at both sides of the breaker.
The transfer bus can be energized by main bus power
by closing the transfer bus coupler isolators and then
breaker
The transfer bus fed to the feeder line by closing the
bypass isolator.
11.
12.
13.
14.
15. The breakers are so connected and form a ring. There
are isolators on both sides of each breaker and circuits
terminate between the breakers. The number of
breakers is same as the numbers of circuits. Each of the
circuits in ring bus system is fed from both sides.
Any of the breakers can be opened and isolated for
maintenance without interrupting any of the circuits. A
fault on any of the circuit is isolated by tripping of two
breakers on both sides of the circuit. This scheme has
good operational flexibility and high reliability.
The main disadvantage is that when a fault happens
and the ring is split and may result into two isolated
sections. Each of these two sections may not have the
proper combination of source and load circuits.
16.
17. The Breaker and Half scheme have two main
buses; both the buses are normally energized.
Three breakers are connected between the
buses and the circuits are terminated between
the breakers as shown.
Any of the breakers can be opened and
removed for maintenance purposes without
interrupting supply to any of the circuits.
Also one of the two buses can be removed for
maintenance without interruption of the
service to any of the circuits.
