380kV LINE VT FAIL

380 kV fail due to over voltage

The line VT rated 400KV for continuous  charging. Line length is more than 300 km. The voltage in sending end was 409 kv and due to line capacitance the  received end voltage was 420kv .

Because of over voltage the lie VT get damaged. The following protections are operated.

RED670

1. Zone-1,2,3 start

2. Zcom -Trip

3. DEF start

4. Fuse fail

Disturbance Report 

Micom 546

1. 21-2 SEND

2. 67N - SEND

3.21-2 RECV

4. 67N - RECV

PROTECTION FOR SPARE LINE

The spare line portion can protect as below during temporary Energization or close the all cross bay CBs to connect 1A and 2A buses. 

There are two way to protect this portion 

1. Take any spare CT below the middle breaker for Bus bar protection to cover the spare line.

2. Enable the Over current and Earth Fault with 0.2 or 0.4 minimum setting in the Breaker failure relay.