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11 KV cables.

broadgage
Until fairly recently, underground 11 KV cables were invariably 3 core, paper insulated, lead covered, with an earthed steel wire armouring. Then came the more modern plastic insulated cables, with earthed armour and a red plastic over sheath to distinguish them from LV cables.


However the modern trend seems to be a bundle a 3 single core cables, each with an aluminium core, plastic insulation, copper wire armouring and a red plastic sheath.

Why is this used ? It seems to me that 3 single core cables would be more costly to manufacture, and more labour intensive to joint or terminate, than one 3 core cable.

I fail to see the advantage, but presume that there must be some advantage, or why make the change ?
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    broadgage:

    DNOs tend where possible to run  11Kv cables in a ring formation, in order that any substation on that ring may receive power from either direction.

    Contrary to domestic ring final circuits, DNO practice is often to run with the ring "open" at one point, this point being selected so as to minimise losses. If a fault occurs, then the faulty section of the ring can be isolated by operation of the "ring main switches" in the substations, and supply restored before repairs are completed.


    Hmm I had assumed that in normal operation the ring was closed and only opened at two isolators if one (or more than one adjacent) point at the substation required isolation.. 


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  • 0
    broadgage:

    DNOs tend where possible to run  11Kv cables in a ring formation, in order that any substation on that ring may receive power from either direction.

    Contrary to domestic ring final circuits, DNO practice is often to run with the ring "open" at one point, this point being selected so as to minimise losses. If a fault occurs, then the faulty section of the ring can be isolated by operation of the "ring main switches" in the substations, and supply restored before repairs are completed.


    Hmm I had assumed that in normal operation the ring was closed and only opened at two isolators if one (or more than one adjacent) point at the substation required isolation.. 


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