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

  • State Helpful Answer
  • Replies 8 replies
  • Subscribers 41 subscribers
  • Views 183 views
  • Users 0 members are here
Options
You may also be interested in

Metal street furniture without an electrical supply: can it be omitted from a simultaneous-contact assessment?

Sam Kindred

Hi everyone, looking for a bit of help and guidance.

We install on-street EV charging supplied from a dedicated feeder pillar with a three-phase 69 kVA supply. Where the DNO permits PME, open-PEN protection is installed; otherwise, a TT arrangement is used.

My reading of the EV Charging Code of Practice, fifth edition, is that metalwork introducing true-Earth potential needs consideration. However, I regularly see metal crash barriers and signs close to chargers.

Can metal signposts, post boxes and bollards embedded in the ground within 2.5 m of a charging vehicle be omitted from the simultaneous-contact assessment, assuming no electrical equipment or connection to another electrical earthing system, even where they may introduce true-Earth potential?

Does the answer differ between TT and PME? Relevant regulation or guidance references would be appreciated.

Thanks.

 

Parents
  • 0


    These sort of things are usually considered extraneous conductive parts, and if it was say an indoor car park, with clear boundaries then they would/ should  be bonded to the MET if simultaneous contact between them and something earthed via the mains was credible. It often is not credible for things like brackets for metal drain pipes and odd bollards, and these could safely  be left electrically 'free floating'. 
    Now I think what you are looking at is more of an outside situation where escaping the true earth potential is more or less impossible, as even the act of stepping into a puddle  connects the person to terra-firma. (one reason for the gravel at substations, so there are no puddles.)

    My suspicion is that reality and the 'pure' advice often diverge here, and in theory it should all be bonded, but in practice it really cannot always be, especially where the lead plus the length of the car extends the 'zone' in some rather odd shapes, or ownership of the bits of metal mean it is not yours to touch.

    We have one of the authors of the guidance (Graham) who frequents this forum, and I would not be surprised if he  adds some additional comments shortly.


    Mike,

Reply
  • 0


    These sort of things are usually considered extraneous conductive parts, and if it was say an indoor car park, with clear boundaries then they would/ should  be bonded to the MET if simultaneous contact between them and something earthed via the mains was credible. It often is not credible for things like brackets for metal drain pipes and odd bollards, and these could safely  be left electrically 'free floating'. 
    Now I think what you are looking at is more of an outside situation where escaping the true earth potential is more or less impossible, as even the act of stepping into a puddle  connects the person to terra-firma. (one reason for the gravel at substations, so there are no puddles.)

    My suspicion is that reality and the 'pure' advice often diverge here, and in theory it should all be bonded, but in practice it really cannot always be, especially where the lead plus the length of the car extends the 'zone' in some rather odd shapes, or ownership of the bits of metal mean it is not yours to touch.

    We have one of the authors of the guidance (Graham) who frequents this forum, and I would not be surprised if he  adds some additional comments shortly.


    Mike,

Children
No Data

Community Rules & Guidelines