Am facing a problem with 2 IC:1BC PCC which am unable to rectify Request Please help.
1] Autochange over from BUS A is normal. (IC-1 trip on Undervoltage Buscoupler close).
2] Autochange over from BUS B is normal (with only 2 Motor running).(IC-2 trip on Undervoltage Buscoupler close).
3] If more than 3 Motors are running Bus transfer from IC-1 to BC is normal while
IC-2 to BC is creating problem. Buscoupler close & open frequently. Please
note UV in Motor relays are disable. None of the relays are registering any alarm
or fault. SEL-751 is used for IC & BC Feeder Protection.
4] I had checked the scheme , Relay Logic & Protections settings & found in line.
5] Some ACB open on surges without any fault on relays.
6] Am in opinion that Motor Residual Voltage is causing this problem but stuck up
for the cause of BC tripping.Am attaching BC tripping scheme for your reference, There are two trip commands,
a] K21 is BC relay & trip logic for same is 50P1T or 51P1T or 50N1T or 51N1T or G1T only.
b] K27 is Master trip & hand reset. There is no other source for tripping.