Primary and Backup Protection
•B,D,G,I are the primary protection.
•A,C,H,J are the backup protection.
•About 90% of faults are clear by Primary Protection.
•So remaining 10% fault are occurred due to failure in tripping of circuit breaker, failure in detection of fault, failure in current transformer or power transformer etc.
•In power system primary protection is the first line of defense.
•Backup protection start protecting the system when primary protection is fails.
•So the remaining 10% fault is cleared with the help of backup protection.
The types of Backup protection are
1.Relay backup (single relay consist of primary and backup)
2.Breaker backup (primary and backup are on same station)
3.Remote backup (primary and backup are on different station)
4.Centrally Co-ordinated backup (primary is at various station and backup is at control room with computer)