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Topic Title: LV Generator Star point earthing - UK
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Created On: 01 April 2014 04:01 PM
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 01 April 2014 04:01 PM
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Posts: 15
Joined: 30 March 2009

Hi all,

Should the star point (neutral) of LV embedded generator that runs long term parallel with utility be directly connected to then customer's LV earth?

The situation is that the customer has LV (PME) supply from utility transformer. At site customer has installed a CHP LV generator which will run parallel with utility all times. On certain occasions the CHP could export power onto utility's network. At customer's site the utility earth electrode and its own earth system are bonded together.

We have following options:
1. solidly connect star point to customer's earth
2. leave star point ungrounded and customer supplies use utility neutral. This will counteract circulating harmonics
3. insert resistance in the star point earthing to restrict harmonics circulating currents.

I would require explanation to above question both from technical as well as UK regulation prospective.

I would like to know what is utility acceptable practice regarding of star point earthing of LV embedded generator.


Musa Shah
 02 April 2014 08:35 PM
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Posts: 6189
Joined: 27 December 2005

With the generation running in parallel with the public electricity supply, there must be no earth connection to the customers neutral. If the generation can run islanded, then an earth must be connected to thr customers neutral during this mode of operation only. It would be usual to apply the earth using a contactor depending on the running arrangements at the time.



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