Protection of an industrial plant

[nasim khalilnejhad]

Hello
I am setting relay for an industrial plant.
I have some question about relay setting
I would be appreciative if someone help me
1. How can we set T.M.S of 51 o.c relay, time delay of 50 and 50g in capacitor feeder.
2.in multifunction relay setting, how can we set the second stage oc2
3.how can we coordinate the l.v circuit breaker and fuses with upstream relay.in my setting the downstream incoming circuit breaker acts before upstream relay
Thanks

 

[wcaseyharman]

I’ve used an engineering software tool like SKM powertools to coordinate overcurrent settings. The Time Current Characteristic (TCC) function automatically accounts for the voltage differences in the overcurrent curves, as well as adjustments to the transformer damage curve if using YD banks. I’d recommend an equivalent engineering tool if you have access to it.

 

[Parchie]

@nasim khalilnejhad (Electrical),
If you have the resources, please use software to plot the TCCs of CBs, both upstream and downstream.
Otherwise, you have to go back to the relay formulas and choose a trip time to solve for the TMS (each type of curve has different formula).