exporting the earth 50kw solar pv system

[jonnycondon]

hi new to this but seems like a good site to swap info and practices,
ok my problem or question is 50 kw solar pv on a farm (or anywhere) but it is ground mounted usually in a field some 50mtrs away. so the main incoming earth to the farm is tn-cs after any advice on how to earth the system, we have a feeder piller in the field with the various dbs ,isolaters and meters inside. inverters are outside ip rated of course what we have been doing is exporting the earth to the feeder piller to protect the armoured feeding the array however not terminating the earth at the feeder piller side so the cable is protected (also 300ma rcd at supply end and seperate isolater) then we are spiking the feeder piller and array and anything in the field with potential any help or thoughts would be welcome !!

 

[malcolmsanford]

Is there a technical reason your wanting to earth the array ?

 

[jonnycondon]

its more for the feeder piller in the field which is basically a new sub db with its own circuits feeding inverters and and i know you cant export a tn-cs so have terminated in armoured glands so its protecting the cable and nothing else the rest of the equipment is protected from spikes however was a little worried about the two potentials

 

[malcolmsanford]

I have to ask you ............is this another rule made up by the DTi concerning extending the equipotential zone, as there is noting in the regulations barring you doing this.

 

[jonnycondon]

haha i think its to many bodies all with there own ideas this was what a niceic rep told us to do ! was just making sure it was right or best practice, or if there was anyone doing differnet i undersatand about the domestic pv side where only if its in the equipotential zone ie velux windows ect but commerical pv is a grey area thanks for ur help malcolm

 

[jason121]

If you follw the old DTI guide should spike the Array
If you follw the new guide you dont.
The earth in the SWA or Seperate earth from Dist board should sized for disconnection time of .4 sec for the inverter AC side
As for the feeder piller should be on an 30ma rcd for sockets outlets and being outside the equip zone

 

[BruceB]

There is no reg that says you cannot export TN-C-S.

There is a small risk if you do from a broken PEN conductor, but normally miniscule unless overhead cables coming through trees.

The PV circuit is a distribution circuit not final cicuit, so disconnection time is 5s not 0.4s.

There are no sockets mentioned by the OP in the feeder pillar so 30mA rcd not required.

Regards
Bruce