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Main switch short circuit capacity.

wessex
Some guidance please.

Three phase TN-S supply from a private 800 kVA transformer. Distribution via a 240mm2 4 core SWA approx 20m in length from a transformer mounted feed pillar and protected by 315A fuses. At the intake position 100A BS 1361 type II fuses are fitted. I was looking to install a REC 4 main switch down stream from which would be three phase distribution by 10kA rated MCB's. My question is about the suitability of the main switch and its short circuit capacity at it's point of installation with regard to prospective fault current at this point which will be greater than 16kA or do the BS 1361 afford adequate protection for the switch ? Your thoughts please.
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    Actually that is a point - there could be some wiring error or damage to the cables between the REC4 and the load so closing onto a fault is possible. mea culpa.


    But the contacts will not be required to interrupt a multi kA fault current, which is certainly the most damaging act with MCBs if they are repeatedly closed and instantly re-trip due to a fault. This sometimes  happens as frustrated gorillas try to make the fault disappear, and sometimes succeeds in vaporising enough of the screw/nail/cable to get the power back on, leaving a damaged installation and no evidence. If it is the CPC that has burned back first this can be quite dangerous.
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  • 0
    Actually that is a point - there could be some wiring error or damage to the cables between the REC4 and the load so closing onto a fault is possible. mea culpa.


    But the contacts will not be required to interrupt a multi kA fault current, which is certainly the most damaging act with MCBs if they are repeatedly closed and instantly re-trip due to a fault. This sometimes  happens as frustrated gorillas try to make the fault disappear, and sometimes succeeds in vaporising enough of the screw/nail/cable to get the power back on, leaving a damaged installation and no evidence. If it is the CPC that has burned back first this can be quite dangerous.
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