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lyledunn

I have an interesting little project. Running two parallel TPN circuits of 150mm2 pvc/pvc single core non armoured conductors on 300mm cable tray for 120m. Neutrals as per lines. Resistive heating load. To ensure equal current share I was going to use L1,2,3,N,N,3,2,1 in flat formation on tray which, according to table 4C5 would warrant a de-rating factor of 0.91. However, I have just been told that there is another large cable on the tray so we will have to run with a double-decker stack with 4 conductors on top of 4 conductors L1,2,3, N on bottom and L3,2,1, N on top. However, not sure of the detracting factor applicable. Load is only 600A per phase so full capacity won’t be used. 

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  • 0

    If this is a long hour load, then you/your customer should also consider the ongoing energy cost represented by cable losses. Presuming standard supply voltage, then 600 amps per phase is about 430 kw. 

    Reducing cable losses from say 2% down to 1% will therefore save about  4.3 kw or at present electricity prices at least £1-30 an hour.

    For a long hour load used for 5,000 hours a year, that is about £6,500 a year. A larger cable size could well pay for itself in reduced losses.

  • 0 in reply to broadgage

    Very good point Broadgage. Another good reason why one should be armed with the load characteristics rather than an instruction to just stick a 600A supply in please!

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  • 0 in reply to broadgage

    Very good point Broadgage. Another good reason why one should be armed with the load characteristics rather than an instruction to just stick a 600A supply in please!

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  • 0 in reply to lyledunn

    Hi Lyle, if you are worried about the terminal temperature, you can always join to larger ends with bolt terminals in a big box close by. This might be a good idea anyway as single cables to the switchgear are generally easier and short lengths of big cable are fairly easily handled. Are you fitting an MCCB at the supply end or fuses? An MCCB with Earth trip would save you a lot of Earth conductor cable too and no problems with Zs at the load.

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