I am sure you must have already given this a thought but I will go ahead and mention it..
It would seem to me that a standard GIS solution suitable for 50 deg C would still be cheaper than a customized or derated version of Air or Vaccum Insulated gear.
But if you must then I have worked...
As rraghunath pointed out a l-g fault will lead to an increased (by 1.732 times) current to pass through the balance two phases.
Also if I read it right the 12.47kV loads are connected via delta connected transformers.. Eeach of these transformers tend to have inrush currents during switching...
If the protections are electronic and settable to completely different settings, try connecting a temporary 110V supply (backed up by a GFCI) and simulate the fault.
The sparking from the viccinity of a grounded surface at the Breaker would be due to the discharging of charged capacitance of the overhead transmission line.
I would not take that as a confirmation of ground fault occurance.
I do not know the exact configuration of the system but have you...
It would be good to establish an occurance of a "ground fault" on the 12.47kVside before entering into a discussion about 50N tripping. As was stated the 50N is acheived via residually connected CTs. This type of protection responds to the residual currents (also called neutral or zero-sequence...
I am not sure I understand your question.
A Parameters Regulation could be defined as Change from no load to full load..
Regarding protection, which protection are you requiring? SC/OC? If you elaborate I might be able to assist.
