Should this SY cable's amour be earthed? This is today’s Q & A of the Day as answered by experts from Prysmian. It’s all about the earthing of cable armouring or screen as in SY type cable. Read on (theme Cables and Wiring):
Question: I recently tested an electrical installation and failed a SY type supply cable to a three-phase roller shutter door because the braided screen wasn't earthed. In fact, each end had heat shrink fitted to insulate it from contact.
Although a separate circuit protective conductor (CPC) was used in the multicore, I believed that if a conductive object pierced the cable and came into contact with a single live conductor, then the braided screen and piercing object would become live. However, as there was no return path for the fault then any protection fitted wouldn't work.
When I informed the contractor who carried out the work, he said that earthing the screen wasn't required as it wasn't an exposed conductive part and a separate CPC had been used for circuit protection and, therefore, was not required under BS7671:2008.
What are your thoughts?
Answer: The cable industry has always recommended that any screen/armour be earthed out. If it is not earthed, induced voltages occur.
However, as we are not inspectors but purely component manufactures, we cannot comment directly on the installation you have described.
To see many more Q & A in Voltimum UK's Experts Area, please click on the link: www.voltimum.co.uk/consult.php?universe=consult.index.questions
|
BookmarkThis
Back