HV Transformer

[dave992]

Hi all,

Just a quick question about earthing arragements into a large building. We are unsure on the type of earthing system which been installed, all we can see is a HV Transformer which feeds our main panel
With 630mm tails and 70mm main earth. All I was asking, is there any way we can tell by looking at the HV transformer? Any advice and more knowledge about HV transformer would be great, I know we dog deal with HV transformer but information would be great to know. Thanks

 

[Pete999]

In my experience, no you would not be able to tell what the LV earthing arrangement would be, you would have to consider what the LV side is feeding, and in your case there doesn't seem to be much info, sorry for the lack of help, all of my HV experience was on MOD property.

 

[westward10]

Is the feed to your panel LV or HV.

 

[Pete999]

Is the feed to your panel LV or HV.

LV I would imagine, hence the transformer

 

[westward10]

LV I would imagine, hence the transformer

I assume so. The 70.0 earth maybe a return to the transformer with the earth derived from the supply neutral within the panel. Many of these supplies will have a copper bar linked from the supply neutral to the earth bar like TN-C-S.

 

[Pete999]

The LV from the TX how does it feed your panel, direct or through a LV switch fuse, or a feeder pillar arrangement, the sort of thing you tend to see on most HV/LV distribution systems

 

[Carl S]

It will be TN-S.


What you need to ascertain is who is providing the earth nest. There are quite stringent rules regarding HV/LV earthing separation. Talk to the DNO about this.

 

[westward10]

It will be TN-S.


What you need to ascertain is who is providing the earth nest. There are quite stringent rules regarding HV/LV earthing separation. Talk to the DNO about this.

That is not necessarily correct.

 

[Pete999]

That is not necessarily correct.

Why?

 

[westward10]

Why?

I suspect that within the switch panel the neutral is connected to earth and the 70.0 earth serves another purpose, to me the supply neutral is a PEN conductor and forms a PNB system however, the flip side is for it to be TN-S because as opposed to taking the earth from the star point of the transformer they have relocated it to within the switch panel which probably explains #7s statement. Theoretically it could be either and there is an argument for both.

 

[Carl S]

I would suggest you look at the UKPN requirements for LV earthing.

For a private network you can’t decide it’s anything other than TN-S without home office approval.