Transformer Neutral Grounding

[charzree]

Should the neutral of the transformer be provided with separate ground rod or can it be interconnected with earth bar which also connects the transformer frame and other equipment frame grounding. Is it correct as per the European standards? ( See the attachment)

 

[TJ Anderson]

You will need an earthed reference for the neutral but surely, The MV designer mentioned in diagram would be responsible to specify that?

 

[davesparks]

I think this depends on the actual resistance to earth of the electrode network, if it is suitably low enough they can be linked otherwise they need to be kept completely seperate.
I don't work with this sort of thing but I have a read a lot on the subject out of interest.

 

[TJ Anderson]

Yeah, very interesting and specialist subject and well beyond me. Ive never worked on anything higher than LV and doubt I ever will.

 

[Carl S]

See my reply on CR4.

 

[davesparks]

See my reply on CR4.

What's a cr4?

 

[Carl S]

Conference room 4

 

[M4SSO]

It is normal practise to connect the low voltage star point (neutral) of the transformer to the neutral bar in the LV switchgear. A separate earth cable should then be connected to the star point of the transformer to a separate earth bar also contained within the LV switchgear. Two earth rods or earth mats of the correct impedance (be aware of the potential step voltages around the rods/mats) should then be connected to the earth bar in the LV switchgear (these are usually duplicated so that one side can be disconnected for testing whilst still maintaining the earth connection to the transformer on the other side). All the earth connections to the steelwork, transformer frames etc are also connected to the LV switchgear earth bar. These earth connections are also generally duplicated for testing purposes. Inside the LV switchgear there should be a removable copper link (for testing purposes) adequately sized connecting the earth bar to the neutral bar.
The earth connection on the MV side is usually connected via a neutral earthing resistor to limit the earth fault current to around 400 amperes. I assume you are looking at 13.8 kV for the MV and 480 V for the LV

 

[Bobster]

Are you asking for you're own self improvement or because you've got a contract doing this.

If its the latter an your asking this most basic safety question, then I'm afraid I'm not willing to help. If you're learning an this is theoretical I can tell you what you need to know.

 

[charzree]

Are you asking for you're own self improvement or because you've got a contract doing this.

If its the latter an your asking this most basic safety question, then I'm afraid I'm not willing to help. If you're learning an this is theoretical I can tell you what you need to know.

I'm asking this for my self improvement. I'm an Electrician who is trying to improve in his trade.