2 supplies to single building

[EricMark]

Where I work it was at one point start up units, and as a result there are I think 4 x 3 phase supplies, the cost to remove them was silly, so we are now using three of them, one general for building, one for an EV charging point, and one for a compressor.

We have considered the TN-C-S supply, but the metal of the building and the 8 miles of railway track are likely such a good earth the only worry with loss of PEN is can the earth bonding take the current, and the supply transformer is not that big, so highly unlikely to cause a problem.

It does seem the DNO does not like two supplies to one building from different transformers, but if all from the same transformer then no real problem.

 

[mhar]

I recently had similar but my 2 supplies were from different transformers going into different ends of a long property divided in two. Western Power were ok with this and with it being PME as long as the two sections were completely electrically seperate. Unfortunately they shared the same oil boiler and all pipework was in copper. A plumber inserted plastic couplers in the places where it was obviously connected (the idea being that these would then be doubled up and distanced if successful so that the two different earthing systems couldn't be touched at the same time) but we still had continuity between the two buildings.
The situation was then referred up to the senior protection officer in Bristol (I believe) who would then only allow us to have tt systems on each with upfront 100mA time delayed rcds. Rodding was a nighmare on one of the sides (except for when going through the drain!!) so they sent out a digger with an operator so that he could use the pneumatic hammer that they attach to the digger to drive in rods for me.
We had just spent nearly 30k on a new installation of a 315kV 3 phase transformer and allowed them to lay a 185? mm wavecon cable from our transformer to an existing pole for them to connect in the event of a failure of that part of the system