Are Neutral Ground Resistor for 100 MW + PV sites common and what are the pros/cons?

[DBL-E]

Most PV solar sites I have provided the relay settings range from 20-300 MW with a collector substation feeding multiple 12-34 kV circuits. At the substation there is typically a wye-delta-wye transformer without a neutral ground resistor. Discussing coordination with another engineer at a conference, most of the sites he worked with have an NGR in the design.

I have a couple questions to start-
1. Is it common for PV sites to have the NGR on the Wye-Delta-Wye MV side?
2. What steps should I take to evaluate suggesting an NGR or suggesting NGR be omitted?

 

[wcaseyharman]

My company is in the process of building a new solar farm and I asked the designer that very question, albeit for a high-resistance system. The designer mentioned that transient overvoltages resulting from single phase faults could exceed typical equipment ratings with the high resistance ground and did not recommend it.

They also mentioned that low reactance NGRs are often applied to limit the SLG fault current in order to protect the cable concentric neutral conductors during faults.