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Topic Title: Earthing/Bonding of Ground Mount System
Topic Summary: solar farm
Created On: 03 December 2012 02:51 PM
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 03 December 2012 02:51 PM
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dimcha

Posts: 3
Joined: 10 May 2012

Hi Everyone,

I would like to ask you if anyone's got experience with earthing/bonding of a ground mount solar system. Currently, I am working on a ground mount solar farm and I was wondering if the frames (buried in the ground) need to be bonded together and then connected back to the main earthing bar. It seems to me that as long as the frames are buried in the ground, they are earthed and in case of a current leakage or fault there is no danger. Am I correct?

I would really appreciate your help.
 04 December 2012 01:55 PM
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fshillit

Posts: 18
Joined: 14 August 2002

The frames will need to be bonded back to the main earth bar (equipotential bonding), as the metallic frames can become live during fault conditions. If your installation in the UK, the wiring regulations apply: see section 411.3 on protective earthing. I'm assuming there is an HV substation on site? If so, you'll need the services of an earthing specialist to ensure there can be no danger to humans or livestock under HV earth fault conditions. Francis Shillitoe
 05 December 2012 03:03 PM
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dimcha

Posts: 3
Joined: 10 May 2012

Thank you very much for this answer.

I understand that the frames can become live under fault conditions and this requires bonding of the system. On the other hand, I am struggling to understand why it's not appropriate earthing as long as the frames are straight buried into the ground.

I reckon that both LV and HV earthing bars should be joined together in the switchhouse.

In terms of the bonding conductor between frames, what variables dictate the required cross section area of this conductor?

thank you in advance.
 05 December 2012 03:44 PM
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OMS

Posts: 19455
Joined: 23 March 2004

Originally posted by: dimcha

Thank you very much for this answer.

I understand that the frames can become live under fault conditions and this requires bonding of the system.

Are they likley to be come live ? - class 2 panels and class 2 cabling coupled with a transformer invertor or an an invertor providing the equivalent seperation would suggest you would be wiser to leave the frame floating

On the other hand, I am struggling to understand why it's not appropriate earthing as long as the frames are straight buried into the ground.

The frames into the ground will probably give you adequate lightning protection - earthing them to the Main earthing terminal is another matter

I reckon that both LV and HV earthing bars should be joined together in the switchhouse.

Steady - you need to know what HV earthing arrangements are in place - I wouldn't assume that they should be connected without checking the relevant HV and LV impedances


In terms of the bonding conductor between frames, what variables dictate the required cross section area of this conductor?

Well code copmpliance would be a start (normally a minimum of 6/10mm2 but possibly up to 25mm2 or even larger. The LPS issue may well drive them up to minimum of 70mm2 - but see my initial comment

thank you in advance.


Regards

OMS

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