33kV System earthing

[RRaghunath]

Which is most common - Solid (or effective) earthing or Resistive earthing.

Thanks in anticipation.

 

[dpc]

What country and what is the system - utility distribution feeder, sub-transmission circuit, or industrial system?

 

[RRaghunath]

The intent is to know the practices world over. More specifically, for a system with 33kV Overheadline distribution circuits.

IEEE141 indicates Resistance earthing is common for 5-15kV systems. I don't think this applies to system with overhead line distribution circuits.

 

[isquaredr]

Raghun
Here in the uk the 33kv system is usually fed from 132/33kv Wye / delta transformers. This leaves the 33kv side un-earthed so a second transformer is introduced with a zig-zag primary whose star point is resistively earthed, an auxillary winding within the "earthing transformer" is used to feed sub-station house supplies etc.
The resistance value is usually set to allow a max earth fault current of 1000-1500 amps.

 

[dpc]

In the US, utility overhead distribution systems are almost always solidly grounded.

 

[RRaghunath]

Thanks isquaredr and dpc for your insight.

isquaredr,
Could you tell me whether the overhead line distribution at 33kV is common in UK or the arrangement you described is for cable distribution.

Thanks once again.

 

[alehman]

dpc - an exception I mention simply because I recently came across it and found it interesting. Detroit Edison operates a large 4800V delta system in the downtown area. Kind of caught me by surprised when I realized my client's large facility was served by this system.