Hi
I have ben asked to complete a design for a Solar installation on 3 of the 8 units within a commercial building. Where all 8 units share the common metal cladding and steel frame.
Each Unit has a PME 100A 3 phase head (the 3 units I'm working on, assumed the rest are the same). All fed from the same Substation. 2 of the units are on one radial from the Substation, the other is on a separate radial which feeds other units across the road.
In installing the Solar system, the required earthing will inevitably connect the PME Earths for the 3 Units together. As the PV Modules will be connected to the metal roof, which in turn is connected to the steel structure. (A functional earth required for the arch fault detection, and to comply with manufactures instructions).
I know connecting 2 PME Earths is bad, (a great deal of previous experience with Multiple Earths) so under 132.16 "including that of the distributor" lead me to UKPN document EN 06-0017, which lead me onto EREC G87. All of which agree in the connecting of PME earths to be bad, and site a steel frame building as the example. With Notes on previous practices, and what would be accepted today.
I could argue, although the steel frame is a extraneous-conductive-part and should have been bonded to the MET (the PME Earth). It has not been. So the current installation is not going to be affected by Diverted Neutral Currents.
In adding the PV Installation, the bond will be created and Neutral Currents can now be diverted.
My opinion, any action which would allow the installation to become unsafe. Which I believe it is, as it does not comply with EN 06-0017 or EREC G87, and BS7671 542.1.3.3. Would be unwise.
EN 06-0017 5.14.4 has a "as last resort" statement "consultation with "asset management" (which I'm still waiting for them to respond to my enquiry).
Sorry for the long winded explanation.
1. Am i justify in raising this issue, (which I have done in some force) and recommended the installation does not proceed, until the DNO have had an input.
2. Has anyone come across a similar situation, and have a solution.
Thank you
