You need to use correction factor of temperature based on maximum operating temperature, typically standard ambient temp is 40C for above ground and 20 C for under ground installation. You can find it in IEEE 399
If you have the same generator size, it is allowed to make a Common Grounding Point because it is easy to applying selective relaying. Actually you can refer to IEEE 142 and ANSI C37.102
There is specific value for 3 winding TR, here is :
0 – 1000 kVA : 9.5 – 12 x In
1000 – 10000 kVA : 5.9 – 11.4 x In
10000-100000 kVA : 3.6 – 7.5 x In
> 100000 kVA : 2.5 – 4.8 x In
but there is no specific value for tow winding TR, it can reach for 40 x, you can refer to IEC 60076. The...
Kibz, here is my answer :
1. Is 10.5 kV line-line or line-ground voltage? The rated voltage of NGR is line-ground voltage of your generator
2. The purpose of using high-resistance grounding, according to IEEE 142 and ANSI C37.101 is to limit the level of over voltage and SC when there is fault...
