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DC HV transmission

May I ask for a bit of advice, purely from personal interest?

When one sees a HV transmission line with four conductors, one can be pretty sure it's DC, probably for the railways. First question: why four conductors and not two? Second question: do DC lines exist with two or six conductors? How would I recognise this?

Many thanks
  • I think that, if this were the case, they wouldn't have used HV insulators.
  • Reply to Michael Wrigley


    Without a photo or sketch it is difficult to know what conductor geometry you are describing.  And where have you seen it?


    To the best of my knowledge, there are no HVDC circuits on overhead lines here in the UK, and I think not many in Europe.  This may change in future.  So, if you saw this conductor arrangement in UK it was almost certainly AC and not DC.


    Hope that helps


    David Ward


     

     


     


     


  • HVDC transmission lines are to be seen in plenty of places across Europe but maybe not in the UK or France where AC is prefered for long distance rail traction. In Austria a plate at ground level explains the voltage and the fact that it is destined for railway use. In Germany and Czechia I have never seen such a plate. Lines have four identical conductors.

    The configuration with four conductors is pretty definitive - it is DC! But I don't see why the transporter decides to use four and, in fact, he may also have lines with two or six conductors but I'm unable to recognise these. There are so many different insulator designs across Europe but I would guess that this would be a clue as to the nature of the current.
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  • Former Community Member
    0 Former Community Member
    It looks you are referring to  either double
    circuit DC  tower which  will have 4 conductors or
    2,  two phase supply circuits for  Railway traction .
    Generally,  Railways get supply through A and  B or B and
    C phase s of 132kv system, which is stepped  down to suit
    traction supply,   Thanks... Umesh 
  • I'm very grateful to Umesh who confirmed my ideas about four conductor lines. On the LinkedIn article about the same subject, there is a picture of a two conductor HV DC line. No way this can be mistaken for a 22kV single phase line.

    However, my thirst for knowledge is not yet totally slaked when it comes to a line with six conductors. Can anyone tell me what to look for to know if the line is AC or DC? It looks like the insulators are very similar, if not identical. In some countries such as Austria, it's written on a plate on the mast but to get to the mast I would often need to take my bike across a field or make some other detour.

    Many thanks in advance

    Mike (in Czechia)