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TN-S with and without Neutral conductors

Nick Parker

Hello everyone,

What are the advantages/disadvantages of using TN-S system with and without Neutral conductors?. Where does it find its application?

ef55b21f1eb9a73bb3f7e8e85eaf7368-huge-tns_without-neutral.png
Without Neutral
387a1fc1393546c05a30da338234ce61-huge-tns_with-neutral.png
With Neutral
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    Actually there are only a few cases where you would omit neutral and it is normally only in the last hop to a motor or some other thing that has no need for it. 

    Sometimes you find a 400v to 230 transformer down the back when they realized they needed it for the instrumentation or interlocks only after a 4 wire feed was fitted.

    You may encounter 400v floodlights on big stadia that get two lives and no neutral, but that is all about the voltage drop and the size of the installation, to get the same number of KVA a greater distance. Its the same reason you occasionally see 690V/400 3 phase instead of 400/230 in really big factories, but in the UK that is quite rare.

     (Germans seem to love it though, as well as a 1k2/690 variant, so mind your fingers when abroad.)

    In general assume 5 wires, but note that neutral should carry less than the lives if the loads are well behaved.

    Mike.

     

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  • 0

    Actually there are only a few cases where you would omit neutral and it is normally only in the last hop to a motor or some other thing that has no need for it. 

    Sometimes you find a 400v to 230 transformer down the back when they realized they needed it for the instrumentation or interlocks only after a 4 wire feed was fitted.

    You may encounter 400v floodlights on big stadia that get two lives and no neutral, but that is all about the voltage drop and the size of the installation, to get the same number of KVA a greater distance. Its the same reason you occasionally see 690V/400 3 phase instead of 400/230 in really big factories, but in the UK that is quite rare.

     (Germans seem to love it though, as well as a 1k2/690 variant, so mind your fingers when abroad.)

    In general assume 5 wires, but note that neutral should carry less than the lives if the loads are well behaved.

    Mike.

     

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