Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 52 replies
  • Subscribers 30 subscribers
  • Views 10966 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

Extra Low Voltage (ELV)

Former Community Member
Former Community Member
Guys,


BS7671:2018 is classing cables extra low voltage (ELV) as an operating voltage not exceeding 50Vac or 120V ripple-free dc.


BS7671 goes on to further categorize ELV cables into SELV, PELV, FELV.


For single core green/yellow insulated equipotential bonding cables lets say originating from an earth bar and bonding some structural steel work, are these classed as FELV under BS7671:2018 ?
Parents
  • 0

    Mike M:



    The conclusion that we had arrived at was that was with nominal voltage being defined as voltage by which or part of an installation is designated we would have to say that the equipotential bonding cables do not form part of a system that has a designated voltage and therefore are not ELV or LV



    I don't agree with your conclusion under all circumstances.


    If the cable is correctly connected at BOTH ends then it can definitely be classed as having Earth potential, and there's not always a need to even insulate it. Protective conductors do not always require insulation.


    HOWEVER, if one end is disconnected for whatever reason, then a hazardous condition may be prevalent.


    So, as I have previously intimated, it depends why you are asking the question. There are two cases in particular which must be highlighted:


    1. For electrical and electronic system maintenance activities, protective conductors and functional earthing conductors may have to be treated like live LV conductors when they are disconnected at one end.

    • Also common is the case where a screen, armour, etc., is connected to one earthing system at one end, and the other end is presented at part of an installation with a different earthing system. Again, we need to treat that protective conductor or functional earthing/bonding conductor in the case of a screen, at the very least in the same manner as a live conductor - gapping and insulating against contact.



    I apologise for having to restate this point, but it's very important if someone is reading this thread because they are assessing risks for certain work activities.

Reply
  • 0

    Mike M:



    The conclusion that we had arrived at was that was with nominal voltage being defined as voltage by which or part of an installation is designated we would have to say that the equipotential bonding cables do not form part of a system that has a designated voltage and therefore are not ELV or LV



    I don't agree with your conclusion under all circumstances.


    If the cable is correctly connected at BOTH ends then it can definitely be classed as having Earth potential, and there's not always a need to even insulate it. Protective conductors do not always require insulation.


    HOWEVER, if one end is disconnected for whatever reason, then a hazardous condition may be prevalent.


    So, as I have previously intimated, it depends why you are asking the question. There are two cases in particular which must be highlighted:


    1. For electrical and electronic system maintenance activities, protective conductors and functional earthing conductors may have to be treated like live LV conductors when they are disconnected at one end.

    • Also common is the case where a screen, armour, etc., is connected to one earthing system at one end, and the other end is presented at part of an installation with a different earthing system. Again, we need to treat that protective conductor or functional earthing/bonding conductor in the case of a screen, at the very least in the same manner as a live conductor - gapping and insulating against contact.



    I apologise for having to restate this point, but it's very important if someone is reading this thread because they are assessing risks for certain work activities.

Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines