zigzag not applied to HRG
zigzag not applied to HRG
(OP)
greenbook - IEEE Std 142-1991 estabilish on page 22 - 1.5.2
A zigzag transformer may be used for effective grounding, or an impedance can be................
........................................
This transformer is seldom employed for medium-voltage,
high-resistance grounding.
Does anyone knows why this restriction?
A zigzag transformer may be used for effective grounding, or an impedance can be................
........................................
This transformer is seldom employed for medium-voltage,
high-resistance grounding.
Does anyone knows why this restriction?






RE: zigzag not applied to HRG
RE: zigzag not applied to HRG
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: zigzag not applied to HRG
Zigzag grounding can be used to get solid (effective) grounding, which is not the purpose of an HRG. HRG is used to restrict the fault current.
Rafiq Bulsara
http://www.srengineersct.com
RE: zigzag not applied to HRG
Rafiq Bulsara
http://www.srengineersct.com
RE: zigzag not applied to HRG
We intend to ground 13.8kV delta system with resistor of 5A in order the first ground fault does not require process equipment to be shut down.
We intend to trip one hour after first ground fault ocorrence.
Tradicionally in Brazil , zigzag transformer is used in subtransmission delta system in order to ground delta and guarantee singlephase fault current be less than threephase fault.
RE: zigzag not applied to HRG
David Castor
www.cvoes.com
RE: zigzag not applied to HRG
A grounding impedance may be inserted either between the wye point and ground or the impedance may be inserted in the delta.
The transformers need only be sized for the impedance limited ground fault current.
The advantage over a zig-zag is that the transformers are not special order and most utilities using delta distribution will have suitable transformers in stock both for initial installation and for replacement.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: zigzag not applied to HRG
Not a restriction, but in the US a zigzag transformer is a very rare beast.
I guess one zig zag is less expensive and more easy installation than Three distribution transformers in wye/delta .
RE: zigzag not applied to HRG
In theory that should be true, but in reality, the zigzag will be more costly because it will be custom built.
Also, you don't need three single-phase transformers - a three-phase unit will also work.
David Castor
www.cvoes.com
RE: zigzag not applied to HRG
RE: zigzag not applied to HRG
The secondary delta is not earthed.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: zigzag not applied to HRG
RE: zigzag not applied to HRG
Rafiq Bulsara
http://www.srengineersct.com
RE: zigzag not applied to HRG
RE: zigzag not applied to HRG
Regular two winding design transformer,connected as a grounding transformer. It is still a grounding transformer by application, just not a zigzag one. This unit would not supply load on the secondary.
See section 1.5.3 in the attached link:
http://s
If it were to be used as distribution transformer to serve loads, it would typically be a delta/wye as you describe.
Rafiq Bulsara
http://www.srengineersct.com