Hi there Alan and kiwi,
This sort of thing is very rare here, as it is looked upon as bad practice to parallel cables up.
This only came about after an apprentice Electrician was sent out to do his first Industrial job and mucked it up from start to finish.
Instead of using a single cable for a Submain to a new building, he ran two seperate cables, in conduit to the panel.
I was asked to come in and take over as an Electrician, as Faults work is a little slow at the moment.
Here's an outline of what I have:
- Circuit length is 65 metres.
- Supply cables are 95mm2 4C Aluminium (shaped) with XLPE insulation on both cores and sheath.
- Current draw required is 300A per phase.
- Cables are buried in PVC Ducting.
- Soil temperature is 15C.
- Protection will be a Merlin Gerin NS series 400A moulded case Breaker, with Electronic Trip Unit.
I personally would have used a single 150mm2 cable and saved all the hassle.
The apprentice must have had a telling off from higher up, as the last time I saw him, he wasn't saying much.