Modelling overcurrent protection

Are you a student ?

You have 30/5 A CTs .

That is relay is of 5 Amp range. - current operated, self powered.

All you require is to make a graph for each relay elements. ( 2 oc , 1 e/f )

X Axis ... Current injected in to the relay Ir - 20 Ir i.e. 5 A to 100A

Y Axis ... Time require to trip

Set PSM =1 and TSM = 1

make a graph. note specifically 10* Ir, trip time - 1.5 sec,or 3 sec ?

then change TSM = 0.5

make similar graph.

Change TSM = 0.25 .

This characterstic curves now helps you to set the relay for any kind of installation for protection.

Same procedure you continue for PSM = 0.5 and PSM = 0.25, PSM = 2