AJJewsbury:
During faults singles can be thrown violently apart due to the large currents and the resulting magnetic fields interacting. I wonder if it might be possible for the harsh switching of the current by the arcing fault to set up some small sympathetic vibrations between the singles within the trunking along the circuit length - which might then become audible at some point where the packing allowed a little movement and the cable happened to be close enough to the trunking wall for the sound not to be absorbed by the other cables.
- Andy.
Wouldn't that level of movement imply quite a substantial fault current such that the OCPD should have tripped, and hence there shouldn't have been many vibrations to hear?
It seems IR tests are showing the circuit as clear.
Perhaps once Dave BP is back on site some current measurements could be taken (clamp meter or better, an oscilloscope) with that suspect circuit switched-on but at first under no load, then subject to load. That might at least show up if there is some odd cable fault. Maybe have a thermal camera at the ready too.
AJJewsbury:
During faults singles can be thrown violently apart due to the large currents and the resulting magnetic fields interacting. I wonder if it might be possible for the harsh switching of the current by the arcing fault to set up some small sympathetic vibrations between the singles within the trunking along the circuit length - which might then become audible at some point where the packing allowed a little movement and the cable happened to be close enough to the trunking wall for the sound not to be absorbed by the other cables.
- Andy.
Wouldn't that level of movement imply quite a substantial fault current such that the OCPD should have tripped, and hence there shouldn't have been many vibrations to hear?
It seems IR tests are showing the circuit as clear.
Perhaps once Dave BP is back on site some current measurements could be taken (clamp meter or better, an oscilloscope) with that suspect circuit switched-on but at first under no load, then subject to load. That might at least show up if there is some odd cable fault. Maybe have a thermal camera at the ready too.
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