Generator Earthing

[AECproject]

Does anybody know about the correct and legal method using 17th edition to connect a generator to earth?

I need to clarify my understanding, can anyone help...

 

[ScottyUK]

Islanded generator, paralled generator, what voltage, three wire or four wire, solidly earthed or not, etc?

Furnish some information if you want anything other than 'with green / yellow earthing cable' as an answer. A drawing would be even better.


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If we learn from our mistakes I'm getting a great education!

 

[AECproject]

Islanded generator - Wot is meant by this?

paralled generator - No, it's single standby genset

what voltage - 415V

three wire or four wire - ???

solidly earthed or not - ??? I know it mus be earthed but how is part of what I'm asking...

There are several sets of various sizes, avarage about 100kVA. They are all single standby generators, I am not interested in cable sizing just on the correct method to connect the gene to a good earth...

thanx

AEC Power Control - Uninteruptable Power Supply Solutions, backup power specialists...for more information see our website -

http://www.aeceuro.co.uk

 

[powerwagon75]

How are they being connected? Cable & plug, 3-pole transfer switch, 4-pole transfer switch, and where are you located (AHJ issues) will all make a difference.

eric

 

[AECproject]

I assume by where located you mean which country ?

I'm in the UK the generator is hard wire connected to the buildings mains incomer DB using 4 pole transfer 3phases & Neutral being switched.

hope this helps a bit more

AEC Power Control - Uninteruptable Power Supply Solutions, backup power specialists...for more information see our website -

http://www.aeceuro.co.uk

 

[ScottyUK]

Islanded generator - it is on its own providing power, so its governor and AVR are configured to provide fixed frequency, fixed voltage.

Paralleled generator - one of a number of generators operating as group, or a generator providing power to the utility grid. Governor and AVR settings are designed to allow load sharing or load control.

3-wire / 4-wire - the machine can be delta connected or star connected. Delta machines in the UK are 3-wire, star machines are either 3-wire or 4-wire. The neutral is the fourth wire, if it is used.

In the UK any LV system neutral must be solidly connected to earth, usually at the origin of the supply. Does your building / facility have its own earth electrode or does it rely on a PME earth from the utility? If you have a private earth then bond the generator neutral to the building main earth bar. The changeover switch will need to be a four pole break-before-make type. If you are using the PME earth from the utility then I am pretty sure you will need a separate earth electrode for the genset, but hopefully one of the guys who works with the DNOs (DNO - distribution network operator) might comment further on this. We have a private LV system where I work so I don't get involved with the DNO requirements.


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If we learn from our mistakes I'm getting a great education!

 

[powerwagon75]

Most 4 pole systems where the neutral is switched, are considered separately derived sources. The neutral and generator frame ground are bonded at the genset, and usually the genset system will have its own earth electrode.

Determine the kind of existing utility/building grounding connections already in place as ScottUK mentioned, and check with your inspecting authority to see which arrangement is agreeable with them.

eric

 

[AECproject]

So basically,

When the utility provides the earth I must make sure a separate earthing rod is used for the genset.

If the building has its own independant earthing then it is acceptable to connect to this.


To ensure my installations are correct I need to speak with each of my site facilities to confirm which way each site's earth is established...

would you agree?

Would there be any serious implications if these were connected incorrectly?
ie: earthing rod not used when utility is supplying earth

AEC Power Control - Uninteruptable Power Supply Solutions, backup power specialists...for more information see our website -

http://www.aeceuro.co.uk

 

[AECproject]

Sorry, also

Are there any tests/checks that an engineer could do when onsite to find out which is true?

AEC Power Control - Uninteruptable Power Supply Solutions, backup power specialists...for more information see our website -

http://www.aeceuro.co.uk

 

[ruggedscot]

Keep an eye on the protection used on the generator - you may have the neutral earth link positioned relative to protection so you need to watch out for that one.

Rugged

 

[FreddyNurk]

Your thread questions are concerning, given your handle and the signature present in your posts.