HV transformer - neutral earthing resistor
HV transformer - neutral earthing resistor
(OP)
I have been told and have no reason to disbelieve that transformers above MV (in my country, 33kV)do not normally have NER's. I have been told that it has something to do with insulation and that it would make the manufacture of a high voltage transformer (i.e. 132/66kV 100Mva)cost prohibitive. I cannot find anything specifically about this on the web and unfortunately I am too curious to just let it go. This has quite a bit to do with a project i am working on at the moment. If someone could fill in the missing detail i would be very greatful.






RE: HV transformer - neutral earthing resistor
Regards
Marmite
RE: HV transformer - neutral earthing resistor
RE: HV transformer - neutral earthing resistor
The client is going to become a customer @ 132kV (previously 66kV) and they are raising questions as to step and touch potential as the TX's in their new substation will have solidly earthed neutrals. They are currently supplied at 66kv, the secondaries at their various substations have NER's. They seem to be comfortable with fault current limiting, so the fact that the new substation will have TX's that have neutrals that are solidly earthed seems to be giving them some reason for concern. I understand the processes etc that take place to ensure earthing at the substation is adequate however, what happens if a fault happens at the downstream substation where the secondary of the 66/(whatever)kv has an NER? Could ther be an issue of step or touch potential there if downstream substation earthing has been engineered for NER configuration? I am thinking that substation earthing is engineered for primary voltage fault current in which case it would make no difference BUT I am new to this so am asking for a little guidence. Thanks in advance.
RE: HV transformer - neutral earthing resistor
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If we learn from our mistakes I'm getting a great education!
RE: HV transformer - neutral earthing resistor
Regards
Marmite
RE: HV transformer - neutral earthing resistor
When you change your subestation from 66 to 132kV you have check:
1how much does was the increase of short circuit at switchyard of low level(<66kV)?
2 if you install reactor(more easy to manufacture, no loss)you have to change neutral NBI of your transformer.Your star winding(132kV) should be different NBI graduated.
3-if you do not install reactor, 132kV transmission line should installed with shield wire in all circuit and counterweight cable at beginnig of subestation (6km)you can reduce substantially the potentials at grounding grid subestation.
RE: HV transformer - neutral earthing resistor
RE: HV transformer - neutral earthing resistor
Great.
Slava
RE: HV transformer - neutral earthing resistor