AS2067

[Vincent Tai]

I have a question about the earthing requirement in AS2067. Figure B5 and B4 show that the earth cables from the HV substation should connect to the earth bar of the remote transformer. Since the HV substation is far away from the remote transformer, we do not need to equalize the potential. why do we need to connect the earth between them? The earth conductor could transfer the EPR (Earth Potential Rise) from the HV substation to the transformer location in the event of an earth fault. That could create a dangerous situation for the people near to transformer. Could anyone help me to answer this question? Thanks

 

[FacEngrPE]

Same discussion is here

https://www.physicsforums.com/threads/a-question-about-as2067.1012215/,

My opinion - not based on the standard, is that extending the earthing conductor will provide a low impedance path, make fault currents higher, and thus make the protection more likely to trip on the event of a fault.

Protection is a complicated subject, consult an expert.

 

[JezNZ]

To add to FacEngPE:

Earthing is a complicated subject, consult an expert.

If you choose not to interconnect the earthing, unless you have a very good remote electrode at the transformer you could have a high EPR on a fault at that end (say fault at the HV bushings to transformer enclosure).

It's a tradeoff and you need to consider both (all) fault scenarios and ensure they are both (all) safe.