Philosophy of OVERCURRENT RELAY COORDINATION IN SUB STATION

After going through this course You will be able to understand how Relay Coordinator is done for IDMT Over current Relay in a Sub Station. A simple example has been taken with two nos 132/33 KV 50 MVA Transformer and in 33 KV System two nos of Feeders with One Bus Coupler CB has been considered. After going through this course viewers will be easily calculate TMS setting for OC Relay from Feeder to Bus Coupler to the LV Side of Transformer and to the HV Side of Transformer and hence how Relay Coordination is done for OC Relay in a Particular Sub Station. Here the Fault MVA for 132 KV Bus has been considered as 1000 MVA and %Impedance for Transformer is 10% each. CT Ratio for HV Side and LV side of Transformer are 400/1 and 1000/1 respectively and for BC and Feeder are 800/1 and 400/1 respectively. Time Margin has been considered for trip time from Feeder to BC to LV Side OC Relay to HV Side OC Relay. Two cases has been considered, one: considering two nos transformers are running under parallel condition and Case-2: One no. of Transformer is under Shuw down and other is running.