Contact US

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!

*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

Generator earthing (standby generator)

Generator earthing (standby generator)

Generator earthing (standby generator)

Hi guys just trying to get my head round generator earthing. I understand we earth the alternator to earth usually by means of electrode and have the neutral tied to this. This then goes through the changeover switch or ACB through to the installation. I don’t know if I’m overthinking this one but what’s in place for earth fault protection between the generator and breaker. Say if an earth fault occurred at the generator I can see the earth electrode will be pulled up to whatever voltage it’s exposed to but what prevents persons receiving a shock in these instances?

RE: Generator earthing (standby generator)

It sounds like your earth connection is made in your supply transformer. With a standby generator you now have two sources of power. The best solution is to make the earth/neutral connection in your switchboard. The generator and transformer enclosures should be electrically bonded to the switchboard to prevent shock hazard and provide a fault current patch back to neutral in the event of a fault.

RE: Generator earthing (standby generator)

If you ground the generator neutral at the generator, you must then switch the neutral in the transfer switch.
If you ground at the switchboard you may use a solid neutral in the transfer switch.
Then ground fault current will return to the generator through the existing ground fault protection.

Ohm's law
Not just a good idea;
It's the LAW!

RE: Generator earthing (standby generator)

Thanks guys for your replies. I’m just trying to get my head round what protects the actual outgoing cables from the generator before the overload protection. So if there was an earth fault before the main breaker. I hope my question makes sense.

RE: Generator earthing (standby generator)

I hope that your generator has a breaker on the output as part of the generator skid.
On many standby and some prime sets, there is no protection between the windings and the first breaker, wherever the first breaker is located.
On larger sets you may use differential protection but that is rare on smaller sets.
I remember a 75 KVA set with a ground fault in the windings.
The set ran to destruction.
I was responsible for a small existing power plant with sets up to 1500 KVA that had no protection between the sets and the breakers in the main switchboard.
I recommended differential protection on a new 1500 KVA set, but was overruled by the budget department.

Ohm's law
Not just a good idea;
It's the LAW!

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! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

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