rossfox
Member
- Location
- Chattanooga, TN USA
Hello all. I have been asked by a local manufacturer plant, to look into ground currents that are measured by their maintenance man on the service grounding conductor - specifically the grounding conductor to the building steel, which is a 3/0 copper. The service is an underground in PVC 3000 amp, 480/277 wye, paralleled service. The neutral is not being used in this plant for anything, but it has been brought to the service gear, and terminated on the neutral bar. The neutral bar is then connected by a buss bar to the equipment grounding bar, which in turn has the grounding conductor going to building steel and cadwelded. There is also a grounding conductor going to a ground rod and then unbroken on to a second ground rod 8 feet away. Their electrician tells me he is measuring from 160 amps to 230 amps on this grounding conductor. He goes on to say that as he turns things off in the plant, the current on the grounding conductor to building steel diminishes to around 30 amps. With all of the breakers off in the service gear he says he is reading around 30 amps. I am thinking that maybe one of the paralleled phase conductors underground in damaged and leaking current to ground, which is finding its way back to building steel, thru the grounding conductor, to the equipment ground bar, the neutral bar and back to the pad mount. Any opinions? rossfox