Switchgear Arrangements

 Single Busbar

Advantages

• The control system is straight forward

• Each bay practically independent

• No switching in current transformer   (CT) and voltage transformer (VT)   circuits

Drawbacks

• The object, line or transformer, out of   service for maintenance of the circuit   breaker (CB)

• The complete station is out of service   for a busbar fault

Double busbar

Advantages

•   Faults limited to objects on the   faulty bus

•   Reduced short circuit currents and   reduced network disturbance with   open bus-coupler

•   Busbar transfer without load   interruption

Drawbacks

•   The object, line or transformer, out   of service for maintenance of the   circuit breaker (CB)

•   Bus voltage and breaker failure trip   requires selection circuits

•   Switching of busbar CTs, tripping and   interlocking circuits

 Transfer busbar

Advantages

•   Maintenance of 1 CB without load   interruption

•   No switching in CT  and VT circuits

Drawbacks

•   Switching in trip and autoreclosing   circuits

•   Only one bay can be connected to the   transfer bus

• The complete station is out of service   for a busbar fault

Ring busbar

Advantages

•   Operation can be maintained with 1   circuit   breaker (CB) out of service

•   Simple interlocking

Drawbacks

• Two CBs have to be tripped at a   primary fault

•   Autoreclosing of two CBs in   sequence

•   Summation of CTs required

•   Switching in VT circuits

 1 1/2 breaker busbar

Advantages

• Operation can be maintained with 1   circuit   breaker (CB) out of service

• Simple interlocking

• No switching in current transformer   (CT) circuits

Drawbacks

• Two CBs have to be tripped at a   primary fault

• Autoreclosing of two CBs in   sequence

• Summation of CTs necessary