I have got two cables running vertical shaft turbine pumps(480 VAC). Both identical 300 HP, one is fed by a 500 MCM type TC cable. The other a 350 MCM type TC cable, both 1200 foot in length. These systems were designed by an electrical engineer. Although I disagree with the application. They are in a stone quarry, subject to damage from falling rock. And they have been hit numerous times.
MY issue is the 500 MCM cable, I am always fighting shorts. The 350 MCM never gives me any problems. They both run parallel to and from the same location. The 500 MCM keeps blowing out. The last two have been within 2 feet of another splice.
Now, I don't understand what is causing the problem. When I expose the area, it has always been arcing between phases or phase to ground(which is uninsulated). Sometimes it looks like the insulation has just been "chewed off". Is it possible that this cable has been exposed to some sort of a surge and weakened it. Or is this a "bad" cable. (both cables installed at same time-August 2004)
I am looking for any suggestions on what might be causing this(before I pull all my hair out).
Thanks, Merlin
