HIgh Resistance Grounding: sanity check on choosing cable sequence impedance

[brainsalad]

Hello:

I am working on sizing the neutral grounding resistor for a high resistance ( through a distribution transformer) grounded generator. In the first steps, the total system charging current must be determined. I am first gathering the contributions from large cables (500, 750MCM), and wondering if you can please verify that zero sequence capacitance of the cable should be used to determine the charging current. In general, is the zero sequence impedance (of any connected device) the correct to use? Thanks for your help.

 

[Marmite]

The resistor would normally be sized based on the maximum fault current and duration rather than the quiescent current.
Regards
Marmite

 

[davidbeach]

But that maximum fault current must be higher than the charging current, so the question is relevant.

I really don't know, but I suspect that positive sequence charging current is sufficient.

 

[odlanor]

ground resistor should be sized to reduce transient overvoltage to safe levels at healthy phases. in case a fault to ground in the generator.
see attached and IEEE-C62.92-Part II

 

[7anoter4]

See also:
GROUND FAULT PROTECTION ON UNGROUNDED AND HIGH RESISTANCE GROUNDED SYSTEMS-APPLICATION GUIDE
Post Glover Resistors
Appendix 1.Pg 15

http://www.google.co.il/url?sa=t&rc...urce=web&cd=2&sqi=2&ved=0CFUQFjAB&url=http://

http://www.postglover.com/Literatur..._pW_Cg&usg=AFQjCNGyhXtaRlTgGtTCF813t8hLYX1mhA