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Topic Title: USE of SWA as a DC conductor in PV system
Topic Summary: How/where do you earth the exposed conducting part
Created On: 28 November 2012 08:49 AM
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 28 November 2012 08:49 AM
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PatHammond

Posts: 215
Joined: 04 December 2008

I was involved in installing a metal framed ground mount 10kwp PV system recently The inverters were sited 100m away in the property and the DC was run to the inverters from the ground mount in standard SWA in to a double insulated DC isolators at both ends of the cable run and then double insulated flex to the inverter and flex to the panels.

The property was PME.

There didn't seem to be any consideration in the design about the earthing/grounding of the SWA or array frame in the case of it becoming live in a fault NB this would be on the DC side.

Any thoughts.

-------------------------
4.5 day wonder...had to start somewhere
 28 November 2012 09:17 AM
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AJJewsbury

Posts: 11251
Joined: 13 August 2003

Given that the d.c. side is normally separated from earth, then protection probably isn't by EEBADS (even if it was fused at the panel end, the variability of supply current would make ADS pretty unreliable anyway).

So presuming the d.c. is separated, it would take two faults to pose a danger (1st fault would simply earth one of the live conductors, TN style) - it wouldn't obviously pose an unacceptable risk.

I guess we can debate whether it comes under section 413 or 418.3 (personally if there several exposed-conductive-parts within reach of each other, I might be tempted to bond them together (but not deliberately to earth), in case of two faults of opposite polarity).

- Andy.
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