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Topic Title: Earthing and LPS at a wind turbine
Topic Summary: Earthing and LPS
Created On: 16 May 2013 04:42 PM
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 16 May 2013 04:42 PM
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Has anyone had experience on the best way to earth a wind turbine (needed at the turbine for control electronics) and LPS (needed to protect against lightning strike or induced surges) of which both are required at the wind turbine. The wind turbine in question is the range of 100kw to 500kW. The DNO provided earth cannot be extended.

How this has been done previously is for a combined LPS and earth, with SPD protection. But I'm concerned that should a direct lightning strike occur, the SPDs will operate, but may not protect the turbine electronics from a direct strike.

However, if the two earthing systems are separated, how much separation distance is required from the edge of the LPS system to the earthing system?

Any help or documents to refer to would be greatly appreciated.
 16 May 2013 10:57 PM
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I don't have any experience with wind turbines but from BS EN 62305-3:

"From the viewpoint of lightning protection, a single integrated structure earth-termination system is preferable and is suitable for all purposes (i.e. lightning protection, power systems and telecommunication systems)."

Also per the Wiring Regs the lighting protection system down-conductors are generally classed as extraneous conductive parts so they must be bonded to the main earthing terminal of the installation. Even if the systems are bonded together at one point I would still avoid physical separation of the systems as it is probably impractical and I probably doesn't yield any advantage anyway. The best strategy is to reduce the combined earth termination resistance to a low a value as possible to protect the physical structure and to used zoned protection of SPDs to protect sensitive electronics.

Regards, Tim

Everyone loves a fireman - but hates the fire inspector.
 17 May 2013 09:31 AM
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American site but might help with ideas.

Telecom buildings could have up to eight down conductors from the lightning protection system, it was not difficult to get the magic figure below 10 ohms for the combined earthing rod system, and you do not have that luxury. Copper test link, I suppose you would need to fit one for testing purposes.
 17 May 2013 03:19 PM
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Thanks for the replies.

Timothyboler - that clears it up for me what you've quoted from BS-EN-62305. I agree physical separation is impractical, so can be discounted.

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