Point to ponder

[the pict]

Outside cabinet to power private estate street lights, cabinet is suppllied from mains PME,d standard 1361 cut out and independant meter, two way C/U, outgoing cables are 2.5 3 core SWA,
where is the EPZ ? and if within the cabinet,then I cannot take the earthing outside it, if I take it to each lamp in turn (15 in total) I am theoretically exporting the PME or am I
Pict

 

[Silly Sausage]

biff's the street lighting expert...I think!

Are they not just exposed conductive parts, so just need earthing?

 

[telectrix]

the lights are part of the installation and so the EPZ extends to all points.

 

[Engineer54]

Outside cabinet to power private estate street lights, cabinet is suppllied from mains PME,d standard 1361 cut out and independant meter, two way C/U, outgoing cables are 2.5 3 core SWA,
where is the EPZ ? and if within the cabinet,then I cannot take the earthing outside it, if I take it to each lamp in turn (15 in total) I am theoretically exporting the PME or am I
Pict

In fact, you Don't EXPORT an equipotential zone, you EXTEND it!! Low and behold, ...everything actually makes sense then too!!

 

[the pict]

Well put Eng 54
Pict

 

[Hants-Spark]

In fact, you Don't EXPORT an equipotential zone, you EXTEND it!! Low and behold, ...everything actually makes sense then too!!

I'm hoping a simple logical question for one who knows little about this sort of installation, what if there is a street sign fed from a different supply adjacent to a lamp post, how would that effect the situation?

 

[Guest55]

EPZ doesnt really apply to highways power & street lighting furniture in the traditional sense
in a domestic its easy to define the zone by virtue of the property / building and any metallic services entering it that may require earthing / bonding.

but go out onto the public highway with a street lighting circuit that can stretch for hundreds of yards then all gets a bit difficult to establish.

and if you consider metal lamposts to be part of the epz you would need to run 10mm earth bonds to each unit , which obviously isnt really feasable , so earthing is provided by your swa , as is the industry norm.

on the whole i'd say it doesnt really apply to this type of installation although others may disagree.

 

[Knobhead]

Section 7.7 of this may help

http://library.ukpowernetworks.co.u...017+Customer+Installation+Earthing+Design.pdf