UV protection query for earth cables

Question

Hi 
 I'm seeking confirmation if there is a reasonable engineering response to avoid the requirement for the installation of metal covers as UV protection for large G/Y CPC cables that are installed for external generators and transformers on a metal cable rack system. The cables are 400 sq mm 6491B H07Z-R, and do not have inherent UV protection in the sheath (the accompanying phase conductors do). External portion of cable route is approximately 40m with lots of bends and would be difficult to retrofit with protective covers. I understand there is a requirement to provide UV protection to cables exposed to sunlight, however I would question if there is an argument to claim that the lack of such protection on these large cables would not pose any degradation of their functionality as protective conductors, and that compliance with the regulation in this case would not be reasonably practicable?

mapj1 · Accepted Answer

In the past I think others have argued that in locations like this, where bare copper is acceptable for earthing, while it looks a bit rubbish for the insulation to flake off after a decade or two, it is not actually a problem. Any where it would matter can be taped or painted. at 400mmsq I cannot see there being a corrosion risk of hte cable snapping ;-) 
 Mike.

AJJewsbury · Answer

Just to add that sometimes the insulating properties of G/Y is needed - e.g. to keep LV and HV earths separated on a "hot" transformer site or simply to keep earthing systems out of touching distance of each other. But as Mike says, if the situation is such that a bare conductor would be acceptable, the G/Y is pretty much just cosmetic. 
 - Andy.

mapj1 · Answer

if anyone is that worried they can schedule a shorter re-inspection cycle. In my experience in most of the UK outdoors wiring the layers of dead leaves lichen and general grot serve as an adequate UV screen in many cases, and in the other half it is in the shadow of something else - I assume this is most unfortunately on the unobstructed south facing side of something without a fence to offer any shade ;-) 
 Mike

AMK · Answer

My interpretation of 522.11.1 requires the wiring must be of a suitable type or shielded when exposed to significant solar radiation or a medium level (AN2) of solar irradiance, which ranges from 500 W/m2 to 700 W/m2. Nevertheless, protective conductors exceeding 6 mm in cross-sectional area do not need covering as per regulations 543.3.201. So does it really matter if the insulation is degraded?

UV protection query for earth cables

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