Two neutrals of wye secondary transformers connected together

[mull982]

What would happen if the neutrals of secondary wye connected trasnformers were both connected to ground through a Neutral Ground Resistor but had their neutrals tied together on the line side of each ground resistor, or esentially at the neutral bushing of each transformer?

Could there be circultating currents that would result between this connection? What would cause these circulating currents?

 

[brian john]

Are there phase to neutral connected loads?

 

[mull982]

Are there phase to neutral connected loads?

No all loads off of each secondary are 3-phase loads and the phase conductors are completely seperate from each other (i.e. not paralleled)

 

[jghrist]

What are the primary-secondary transformer connections?

 

[mull982]

What are the primary-secondary transformer connections?

Primary Delta - Secondary Wye

I hope this is what you meant

 

[nollij]

I currently can not think of any reason why there would be any circulating currents or any other issues with this setup. (3-phase only loads, not paralleled XFMRs).

I can not comment on the use of a single Neutral Grounding Resistor for these two XFMRs as I do not have enough information to determine what type of system protection you are utilizing.

High Resistance? Would be better to seperate the neutrals to know which system has the ground fault.

Low Resistance? Would consider sizing the NRG were both systems to have a fault at the same time due environmental issues.

 

[jghrist]

With no zero-sequence connection to the primaries, I don't see a possibility of circulating currents. You will essentially be paralleling the NGRs, so the ground fault current will be twice as high. Any unbalanced load current will split between the two NGRs.