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Topic Title: GENERATOR EARTHING
Topic Summary: Need for electrode?
Created On: 02 October 2017 02:09 PM
Status: Read Only
Linear : Threading : Single : Branch
 GENERATOR EARTHING   - John Peckham - 02 October 2017 02:09 PM  
 GENERATOR EARTHING   - OMS - 02 October 2017 04:02 PM  
 GENERATOR EARTHING   - AJJewsbury - 02 October 2017 04:48 PM  
 GENERATOR EARTHING   - John Peckham - 02 October 2017 04:52 PM  
 GENERATOR EARTHING   - aligarjon - 02 October 2017 05:18 PM  
 GENERATOR EARTHING   - OMS - 02 October 2017 05:09 PM  
 GENERATOR EARTHING   - davezawadi - 02 October 2017 06:08 PM  
 GENERATOR EARTHING   - mapj1 - 02 October 2017 07:39 PM  
 GENERATOR EARTHING   - John Peckham - 08 October 2017 12:21 PM  
 GENERATOR EARTHING   - mapj1 - 08 October 2017 02:21 PM  
 GENERATOR EARTHING   - AJJewsbury - 08 October 2017 02:32 PM  
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 02 October 2017 02:09 PM
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John Peckham

Posts: 8783
Joined: 23 April 2005

I wonder if the brains on the forum could help me with this?

BS7430 requires generators rated at 10kW or more to have an electrode with an Ra of 20 ohms or less.

If the generator star point is connected to earth and neutral and these are distributed, a sort of TNS without the "T", what is the purpose of the electrode and why is this required for more than 10kW given the electrode is not in the earth fault path? I am thinking about site temps. and temporary installations.

My thoughts are.

1. Larger than 10kW is likely to have a larger installation connected to it and there will be capacative coupling to the general mass of earth, so the could be a potential difference between the supply earth and the general mass of earth.
2. If the generator has earth fault protection then a fault to the general mass of earth MAY (not certain) cause ADS where the over current protection may not operate.
3. For IR testing we we require the installation to be connected to earth so IR faults can be detected.
4. Regulation 8 of the EAWR probably requires a connection to the general mass of earth.

Any thoughts?

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
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