Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


11/0.4 kV transformer neutral earthing

11/0.4 kV transformer neutral earthing

11/0.4 kV transformer neutral earthing

1500 kVA transformer, 11/0.4 kV Dyn11 installed in a substation
what is the standard or practice for earthing the LV side neutral point ?
is it required that the neutral point should have a separate earthing point/system or it can be connected with the substation earthing system?
what is the advantages, and disadvantages in both cases (separate earthing or earthing with the substation earthing)?

RE: 11/0.4 kV transformer neutral earthing

Its better to separate neutral point from substation earthing system. But in my country we use to connect neutral and substation earthing together. Only lightning protection grounding remain separate from all. For LV side you must have separate earthing system for your equipment.


RE: 11/0.4 kV transformer neutral earthing

Normal practice is to bond the LV neutral point to the substation earth grid. If the earth potential rise due to an 11kV fault at the substation is excessive then the LV earth can be separated, but this can be problematic as segregation of the HV and LV earths has to be maintained for some distance away from substation.

RE: 11/0.4 kV transformer neutral earthing

In the US, the neutral would be bonded to the substation ground grid. Separation introduces other problems as Marmite indicates. "Isolated" grounds are not really totally isolated in most cases. And lightning strikes will laugh at your "separation".

RE: 11/0.4 kV transformer neutral earthing

REF is more important with impedance grounded transformers because winding faults close to the neutral are harder to detect. The normal transformer differential protection will adequately protect solidly grounded transformers, but normally I would use REF if a neutral CT is available and the relay has the REF element built in.

RE: 11/0.4 kV transformer neutral earthing

I agree with dpc. However, according to IEC [or BS EN 50522/2012] there are some conditions in order to use the same grounding grid for high voltage and low voltage installations- chapter 6 Measures to avoid transferred potential.
See Table 2 Minimum requirements for interconnection of low voltage and high voltage earthing system based on EPR limits.
Following Annex A and B one may calculate the touch voltage.
The lightning protective grounding it is recommended to be connected with the substation grounding grid .See Annex F for further details.
You may read also IEEE 80/2013. chpt.17.9 Transferred potentials.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close