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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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    It is not that the neutral is omitted.. in first case Neutral is combined with protective earth and in the second case , both are separate.

    Perhaps it looks that way. But in TNS no loads will be connected between a Live and a protective earth (*), while a load current will flow in a neutral, if it is needed, as part of normal operation, not just during a fault.

    TNS without neutral is not to be confused with TNC, where we do allow a shared neutral and earth, but at least in the UK, only permitted for distribution networks, and with additional precautions taken. - you cannot have an RCD-like function in a TNC system, as fault current and load currents share a wire.

     

    Mike

    (*) Well, it is sometimes seen actually, but is very naughty - load currents flowing in the earthing wiring are considered a very bad thing, and in a well designed system Automatic Disconnection of Supply (ADS) will operate in some form to remove the power should the earth current be more than a fraction of a percent of the full load current. 

     

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  • 0

    It is not that the neutral is omitted.. in first case Neutral is combined with protective earth and in the second case , both are separate.

    Perhaps it looks that way. But in TNS no loads will be connected between a Live and a protective earth (*), while a load current will flow in a neutral, if it is needed, as part of normal operation, not just during a fault.

    TNS without neutral is not to be confused with TNC, where we do allow a shared neutral and earth, but at least in the UK, only permitted for distribution networks, and with additional precautions taken. - you cannot have an RCD-like function in a TNC system, as fault current and load currents share a wire.

     

    Mike

    (*) Well, it is sometimes seen actually, but is very naughty - load currents flowing in the earthing wiring are considered a very bad thing, and in a well designed system Automatic Disconnection of Supply (ADS) will operate in some form to remove the power should the earth current be more than a fraction of a percent of the full load current. 

     

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