Busbar

1. BUS BAR PROTECTION
Sumeet Ratnawat
NCA Indore

3. OBJECTIVE OF STATION PROTECTION
 To protect all such elements or sections in
a substation which are not covered either
under line protection or equipment
protection
Station protection include
 Bus Bar protection
 LBB(Local Breaker back-Up) protection

4. CT CORES
 CORE 1  BUS BAR CHECK ZONE
 CORE 2  BUS BAR MAIN ZONE
 CORE 3  METERING
 CORE 4  MAIN I LINE PROTECTION
 CORE 5  LBB & MAIN II LINE
PROTECTION

5.  In Absence Of BUSBAR Protection,
Fault Clearance takes place
in Zone II of Distance Relay by
Remote End Tripping
 This Means Slow & Unselective Tripping
and wide spread blackout
NEED FOR BUS BAR PROTECTION

6.  Minimizing damage at fault location
 Maintaining system stability
 Localizing isolation to avoid wide
spread disruption
 Delayed clearance create shock to inter
connected equipment like Generator shaft
and windings of Transformer
NEED FOR BUS BAR PROTECTION

7.  High speed operation
 Selectivity – shall isolate the faulty bus bar only
 Stability – stable for through faults upto 40 KA
fault level
 Reliability – Check feature
 Applicable for any type of bus bar protection
 Shall provide zone indication
REQUIREMENT OF BUS BAR PROTECTION

8.  Continuous supervision for CT Secondaries
against any possible Open Ckt.
 In case of detection of any Open Circuiting of CT
secondary, after a time delay, the affected zone
of protection shall be rendered(provide) in-
operative and an alarm initiated.
REQUIREMENT OF BUS BAR PROTECTION

9.  Bus bar protection must be provided in all new 400kV and
220kV Substations as well as Generation Switch Yards
 For existing substations, provision of bus bar protection is
considered a must at 400kV level and for 220kV level it is
essential at substations having multiple feed.
 In case of radially fed 220kv substations, having more
than one bus it is desirable to have bus bar protection but
is not a must
RECOMMENDATIONS FOR PROVIDING BUS BAR
PROTECTION

10. BASICS OF BUSBAR PROTECTION
NEED FOR BUSBAR PROTECTION
In Its Absence Fault Clearing Takes Place In Zone-2 Of Distance Relay By Remote End Tripping. this means
slow and unselective tripping and wide spread blackout.
EFFECT OF DELAYED CLEARENCE
 Greater damage at fault point.
 Indirect shock to connected equipment like shafts of generator and windings of transformer.
BASIC THEORY
Kirchoff’s current law states that the sum of the currents entering a given node must be equal to the currents
leaving at that node.

11. TYPES OF BUS BAR PROTECTION
 Low Impedance
 High Impedance
Both use Circulating Current Differential
Principle - To isolate the entire bus bar section
by disconnecting all the feeders connected to
the bus.

12. HIGH SPEED DIFFERENTIAL PROTECTION
Simple Current Differential Circuit:

13. Simple Current Differential Circuit with Bus Fault

14. Simple Current Differential Circuit with Close in Line Fault

15. Simple Current Differential Circuit with Restraint Coils and a Close
Line in Fault
Simple

16. High Impedance Differential Relays ( Only Phase A shown)

17. Supervisory Circuit for Checking Bus Differential Protection

18. Typical Instantaneous Over-current Relay

19. IDMT Characteristic of a Relay