Question

What kind of challenges/consideration would you need to take into account with Primary and Backup protection schemes if the feeders have varying impedances and loadings?

66 kv 11 kV CB6 T1 feeder 1 R1 CB1 CB3 CB7 feeder 2

Answer 1

For different impedances and loading we can use current based protection relays so that out generation wouldn't be interrupted. following are the some current based protection relays:-

1. Time-overcurrent protection:- It basically works on ratio of minimum fault current to maximum load current. Relay should be operated in a specific time so that our load will not get disturbed.

2. Instantaneous overcurrent protection:- Instantaneous overcurrent can damage transformers and load. So, this relay protects load by limiting the current to the maximum value of equipment.

In power distribution we also use distance based feeder protection:- This protection instantaneously trip the elements and have fixed zone of protection. It is independent of system changing conditions.