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tank/hv earth electrode and nearby concrete pad with mounted lighting column

psychicwarrior
Hello - good day to all !


Any experience/experiences that might provide a few tips/watch out fors etc, most gratefully received.


Contemplating the run of buried SWA cabled over 100m for outdoor lighting (and electric gates) passing by a pole mounted transformer, where it's been confirmed by the distributor that there is a Tank/HV earth electrode setup  at the pole. Whilst explaining this was not a rigid rule (more a guide and just as well as it shuts off the only feasible route), it was suggested best [in this case] to stay out of a 9m radius if burying cables - but the situation would be helped if this had to be compromised, by running the cabling in ducting/conduit when in the ground.


What are opinions on the siting of concrete pads with threaded rod to secure [conductive] column lighting in this context; this would seem a more serious concern within the 9m advice, is it a no-no, is there anything that can be done to mitigate (aside to using all non-conducting materials), or is it a non-issue (I feel not) ? 


I have no experience of such a long distance, but any tips and advice on pulling SWA along duct for over 100m would be uiseful too :-)   \\m/


Thank you all

Habs

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  • 0
    @Sparkingchip it is...


    It is the concern about the HV voltage being impressed (to use the distributor word) onto *any* grounded metal work (inc. the cable armour) in the vicinity, particularly the closer any of it is to the HV electrode.


    My thoughts have been:


    To understand where an uncleared harmful potential diff. might be that someone might unfortunately experience on this circuit  (presume the whole thing is TT'd, as intended)  ?


    Any LV fault on this circuit should be cleared as required, so it is really about this 'impressed' HV fault voltage on the circuit's earthed equipment until that is cleared in whatever time ?   It's more like a bonding exercise I feel ?


    Is there going to be any harmful potential difference from something touching the lamp post or other connected metal work along the circuit and in contact with the ground (as not likely to be anythng else I imagine) ?    It would seem to be worst case closer to where the impressed voltage is picked up ie. if < 9m from the HV pole electrode ?


    I don't see what can be done about reducing the effects at the lamp posts, so avoiding the 9m is the best bet unless limiting the impressed voltage is possible (as with the comments of putting insulating barriers in place for the SWA in the ground eg. plastic ducting etc)...which does not seem possible with  concrete pads threaded rods and posts into the ground. 


    Perhaps the 9m is a good starting point where by the voltage impressing effects, in this case of a fault passing down the the HV electrode, on metal work are considered not to be an issue.... I wonder on the maths (gulp) !


    What does anyone else think further, if anything .  Thanks all.
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  • 0
    @Sparkingchip it is...


    It is the concern about the HV voltage being impressed (to use the distributor word) onto *any* grounded metal work (inc. the cable armour) in the vicinity, particularly the closer any of it is to the HV electrode.


    My thoughts have been:


    To understand where an uncleared harmful potential diff. might be that someone might unfortunately experience on this circuit  (presume the whole thing is TT'd, as intended)  ?


    Any LV fault on this circuit should be cleared as required, so it is really about this 'impressed' HV fault voltage on the circuit's earthed equipment until that is cleared in whatever time ?   It's more like a bonding exercise I feel ?


    Is there going to be any harmful potential difference from something touching the lamp post or other connected metal work along the circuit and in contact with the ground (as not likely to be anythng else I imagine) ?    It would seem to be worst case closer to where the impressed voltage is picked up ie. if < 9m from the HV pole electrode ?


    I don't see what can be done about reducing the effects at the lamp posts, so avoiding the 9m is the best bet unless limiting the impressed voltage is possible (as with the comments of putting insulating barriers in place for the SWA in the ground eg. plastic ducting etc)...which does not seem possible with  concrete pads threaded rods and posts into the ground. 


    Perhaps the 9m is a good starting point where by the voltage impressing effects, in this case of a fault passing down the the HV electrode, on metal work are considered not to be an issue.... I wonder on the maths (gulp) !


    What does anyone else think further, if anything .  Thanks all.
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