TYPES OF BUS BAR SYSTEM
1 Single
Busbar System
Single busbar system is as shown below in figure
Single Busbar System
a. Merits
1. Low Cost
2. Simple to Operate
3. Simple Protection
b. Demerits
1. Fault of bus or any
circuit breaker results in shut down of entire substation.
2. Difficult to do any maintenance.
3. Bus cannot be extended without
completely deenergizing substations.
c. Remarks
1. Used for distribution substations
up to 33kV.
2. Not used for large substations.
3. Sectionalizing increases
flexibility.
2 Main & Transfer Bus bar System
Main & Transfer Bus is as shown below in figure
a. Merits
1. Low initial &
ultimate cost
2. Any breaker can be taken
out of service for maintenance.
3. Potential devices may be
used on the main bus.
b. Demerits
1. Requires one extra
breaker coupler.
2. Switching is somewhat
complex when maintaining a breaker.
3. Fault of bus or any
circuit breaker results in shutdown of entire substation.
c. Remarks
1. Used for 110kV substations where cost of duplicate bus bar system is
not justified.
3 Double
Bus bar Single Breaker system
Double Bus Bar with Double Breaker is as shown below in figure
a. Merits
1. High
flexibility
2. Half
of the feeders connected to each bus
b. Demerits
1.
Extra bus-coupler circuit breaker necessary.
2.
Bus protection scheme may cause loss of substation when it operates.
3.
High exposure to bus fault.
4.
Line breaker failure takes all circuits connected to the bus out of service.
5.
Bus couplers failure takes entire substation out of service.
c. Remarks
Most widely used for
66kV, 132kv, 220kV and important 11kv, 6.6kV, 3.3kV
Substations.
4
Double Bus bar with Double breaker System
Double Bus Bar with Double
breaker system is as shown below in figure
a. Merits
1. Each has two associated
breakers
2. Has flexibility in
permitting feeder circuits to be connected to any bus
3. Any breaker can be taken
out of service for maintenance.
4. High reliability
b. Demerits
1. Most expensive
2. Would lose half of the circuits for
breaker fault if circuits are not connected to both the buses.
c. Remarks
1. Not used for usual EHV
substations due to high cost.
2. Used only for very
important, high power, EHV substations.
5
Double Main Bus & Transfer Busbar System
Double
main bus & transfer bus system is as shown below in figure
a. Merits
1.
Most flexible in operation
2.
Highly reliable
3.
Breaker failure on bus side breaker removes only one ckt. From service
4.
All switching done with breakers
5.
Simple operation, no isolator switching required
6.
Either main bus can be taken out of service at any time for maintenance.
7.
Bus fault does not remove any feeder from the service
b. Demerits
1.
High cost due to three buses
c. Remarks
1.
Preferred by some utilities for 400kV and 220kV important substations.
6 ONE
& HALF BREAKER SCHEME
a. Merits
1. Flexible operation for
breaker maintenance.
2. Any breaker can be
removed from maintenance without interruption of load.
3. Requires 1 1/2 breaker
per feeder.
4. Each circuit fed by two breakers.
5. All switching by breaker.
6. Selective tripping.
b. Demerits
1.
One and half breakers per circuit, hence higher cost
2.
Any breaker can be removed from maintenance without interruption of load.
c. Remarks
1.
Used for 400kV & 220kV substations.
2.
Preferred.
7
RING OR MESH ARRANGEMENT
a.
Merits
Bus bars gave some operational flexibility.
b. Demerits
1. If fault occurs during bus maintenance, ring gets separated
into two sections.
2. Auto-reclosing and protection complex.
3. Requires VT’s on all circuits because there is no definite
voltage reference point.
4. Breaker failure during
fault on one circuit causes loss of additional circuit because of breaker
failure.
These VT’s may be required
in all cases for synchronizing live line or voltage indication
c. Remarks
Most widely used for very large
power stations having large no. of incoming and outgoing lines and high power transfer.
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