AusPowEng
Electrical
- Jul 19, 2003
- 28
I have an industrial client who has suffered a cable failure whereby the screen bond on a single core cable (6.6kV Cu/XLPE) at the end of a short run had a ‘thermal excursion’ burning through the termination kit and cable insulation. Eventually, the protection activated with a phase-earth fault.
Amazingly the single core was manufactured with steel wire armour instead of Al or Cu armour. The screen is also Cu. For the purposes of this discussion, the cables are at least 240sqmm.
The armour was earthed (grounded) at both ends via to the armour clamping glands used on the switchgear cubicle entires. The gland plate is non-ferrous. The screens were also earthed at both ends of the cable.
The cables were in service for 12 months before the failure. What would happen if a 1C cable has steel-wire armour? I would have thought the armour heating (due to eddy currents associated with the current induced in the armour) would have caused cable failure almost immediately after being placed into service.
Initial evidence indicates a manufacturing fault. In my industry, sending someone off to find such a cable is a good joke to play on graduate engineers. Right now however, I am open to worldwide experience, even if to eliminate the obvious. Has anyone else ever seen steel-wire armour on a single core MV cable?
Amazingly the single core was manufactured with steel wire armour instead of Al or Cu armour. The screen is also Cu. For the purposes of this discussion, the cables are at least 240sqmm.
The armour was earthed (grounded) at both ends via to the armour clamping glands used on the switchgear cubicle entires. The gland plate is non-ferrous. The screens were also earthed at both ends of the cable.
The cables were in service for 12 months before the failure. What would happen if a 1C cable has steel-wire armour? I would have thought the armour heating (due to eddy currents associated with the current induced in the armour) would have caused cable failure almost immediately after being placed into service.
Initial evidence indicates a manufacturing fault. In my industry, sending someone off to find such a cable is a good joke to play on graduate engineers. Right now however, I am open to worldwide experience, even if to eliminate the obvious. Has anyone else ever seen steel-wire armour on a single core MV cable?