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The specific question is as under: If the generator is grounded through high impedance and the interface transformer is star/star solidly grounded at both HV and LV, then after openening of utility breaker for utility ground faults, the overvoltages on healthy phases are unavoidable. The...

Grounding of generator neutral: Generator: 1 MW; 3 phase; 600 V is connected to grid through interface transformer: 1.5 MVA; 27.6 kV star solid gnd/600 V star solid gnd and exports power to grid. How the generator neutral should be grounded? a) Solid; b)Low impedance; or c) High impedance. If...

Slavag Thanks for the complement. I am learning DGs and still there is long way to go. Traditional O/C;E/F protection are proven practices for typical radial distribution system, but are operational only when there is enough current to exceed the settings. I am not aware of Negative Phase...

Thanks Davidbeach and Slavag to be in loop: We are currently facing extremely high level of penetration of DG in sub transmission and distribution system (though majority of them are yet at cost estimate stage but around 250 MW is already connected). Davidbeach: Yes we also use Freewave radios...

Hi Davidbeach Sorry for the delayed response. YOU have touched the original question. There won't be any delay in tripping utility breaker. Usually the typical tripping time without DG ( across North America) should more or less look like: 4 ms (relay time) + 50 ms (electromechanical aux relay)...

Thanks jghirst for the link. Truely speaking all articles which I have come across on the subject till date are just of information level and there is no conclusion in any of them. I understand that there is always a trade off for interface transformer winding connection, because both connection...

Thanks Slavag I understand that it is not simple. However, I am involved in connection impact assessments of such DG. Distribution feeders have re-closers (1 and 3 phase), regulators (1 or 3 phase), fuses, and switches. There is always a trade off between grounded or ungrounded interface...

Slavag Ground switch is not an option. When DG is operating in parallel with grid and if utility side breaker opens for line to ground fault at matching loads it is extremely difficult for DG to sense any significant change in parameters to realize that utility breaker has opened.The over...

Hi Folks Apologies: I meant: 8 MW to be cummulative generation of DG (4 units of 2 MW each @ 600 V). However, the question remains the same even if we consider 8 MW generator (single unit)@ 13.8 kV for utility feeder voltage at 13.8 kV. HV gnd for GSU, is traditional and well practised...

Hello Slavag Thanks for the thread reference. However, I could not find any materialistic debate there. The details of system - as under: Utility supply: 27.6 kV 3 phase 4 wire, multigrounded Generating Facility interface transformer: HV delta 27.6 kV; LV star 600 V solid ground Generator: 8...

I apologize for the late reply. I was pretty busy in other commitments. However, thanks for your input and I would appreciate your comments on following arrangement: Interface transformer: utility side- delta and generating facility side- star solid ground. This releives utility from extermenly...

Distributed Generation: What should be the preferred interface transformer's winding configuration (utility side Delta, Star solid grd, or Star effectively grd. a) preferred by utility; b) preferred by generating facility. However I am interested in utility's preference particularly when...