ZSI for cutler hammer MDS C-32 breaker

[sahelrahman]

Hi
I am currently working on the coordination study using SKM power tool analysis. Questions regarding the ZSI settings.

The SKM support told me that I have to input the Trip/Delay time(sec) for the breakers with ZSI module. The manufacturer said that the minimum trip time is 0.1. Please have a look at the attachment. The diagram shows five breakers (U1-utility, G1-Generator, T1-tie, C2 and C4) with the ZSI. I believe I should not input 0.1 sec for all five breakers.

C2 shall trip before U1 or G1 or T1
T1 shall trip before U1 or G1
C4 shall trip before U1 or G1 or T1

So I believe I shall input 0.1 for C2 and C4, 0.15 for T1, 0.2 for U1 and G1. Is that how it works?

 

[sahelrahman]

forgot to attach the drawing

 

[davidbeach]

I haven't looked at the diagram, but the whole concept behind ZSI is that the breaker closest to the fault is supposed to trip at 0.1 sec when it doesn't receive a blocking signal and trip at its trip time when it does receive a blocking signal. So for arc flash, each would have a 0.1 sec trip time, but for a coordination study each would have its set time.