feeders 51N protection 1

[mares2004]

I have a problem, in my pumping installation, I have a 480 V distribution panel with two buses linked with a breaker , this distribution panel feeds 4 loads, two of them feed a CCM ( with 5 pumps, 250 hp each one))one feeder en each bus, other two feeders feed two general services panels. every feeder has his own protection. when I start more than 3 pumps at time, both services feeders are triped by the 51N at same time, loosing the substation services supply, the pumps continue running. The tripping setting is 180 A and the normal current is 30 amps in each service feeders. I dont understand what is happening if the services feeders are independent to he pumps. may some body help me to understand what is happening?

 

[jbartos]

Suggestion: 51N trips on high neutral return currents. Apparently there is some larger ground fault leakage.
The pump feeders are tapped upstream of the interrupter that trips the substation via 51N. To alleviate this the proper ground fault protection needs to be implemented in the pump feeders and the root of ground fault leak troubleshooted.