Multiple grounding source at a substation

[Prot123]

What will be the impact of having multiple grounding source connected to Substation bus during normal/fault condition. the situation is:

a. 6.6kV generator connected to the bus with its neutral grounded
and
b. 6.6kV LV side of 3 winding transformer connected to the same bus. The LV neutral grounded through a NE Resistor. 3 winding transformer, HV(star ungrounded) of which being feed from another generating source few km apart. Tertiary buried delta to provide zero sequence compensation.

 

[davidbeach]

It would simply be what it is. If it’s properly modeled it shouldn’t cause the protection system any trouble.

 

[Prot123]

Hi Davidbeach,
Will the ground fault contribution from the generator increase because of additional grounding path and what will be the impact of circulating current and chances of mis/no operation of protection device?

 

[davidbeach]

It won't increase, it won't decrease; it just will be what it is for that system configuration. Do the fault calculations and determine the contributions from each source for each fault. Set the relays to work properly with those sources. Take a source out of service, rerun the fault calcs; does everything still work correctly?

The Protection Engineer rarely gets to pick the configuration, so that's always just a given. What ever it is you have to make it work. Good models make good settings.