Eddy Currents with single power cables

Question

Hi 
 Question on Eddy Currents with single power cables. 
 From a generator there are 4 singles per phase which are split in 2 sets and enter a building through 2 steel frames. So each frame has 2 of each phase and 2 x neutral. Will having the cables split ac 
 We have conducted a survey of a site and noted: 
 The site has had a generator upgraded and the cabling has been split between 2 steel frames 
 There is approx. 500mm between frames in a steel wall 
 Each Frame has 2 of each phase cable and 2 x neutral 
 As the cables are split will this cause Eddy currents between the steel frames.

mapj1 · Answer

You may have far more of an eddy issue with the currents that will be induced in each of the aluminium armours. (*) 
 As above, so long as things are bunched in a way that flow and return currents are side by side and more or less balanced there will be no issues from the wiring frame or steel wall. As an example if you wanted to sabotage things, you would have had to put phases L1 and L2 through one path, and phase L3 and neutral through the other path - and even that may work if there were only single phase loads on L3 and only 400V cross bar loads on L-L2, but of course that is not what has been done. Mike * each individual armour runs parallel to one current far more than it runs parallel to any other so a voltage will appear between one end of the armour and the other in proportion to the current in the inner core. Then either all 3 armours need to be so well connected at the ends, that although a large current flows there is no heating, because the resistance of glands and gland plate is low, or the 3 armours need to not connect at one end or the other, so that current up one armour and back down the others does not flow. One either finds massive conductive gland plates, or insulating ones, both approaches are valid. That problem disappears again for multi core armoured cables, so long as the currents in the cores enclosed within one armour are more or less zero-sum as with 3 phase +N or single phase L+N - they usually are.

Eddy Currents with single power cables

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