Ground Fault Problem
Hey guys,
I am a part time BSEE student while I work my full time job as an industrial electrician. I ran into a problem that is stumping me that I am hoping to see if any of you have ran into the same issue.
A building that houses manufacturing equipment was commissioned about one year ago, so everything under the roof is new. Twice now, I have run into two ground faults months apart on two seperate pieces of equipment. One was a 480V 3 phase exhaust fan that had a shorted phase to ground, and the other was a heating rod (277V) that also shorted to ground. My problem is that even though each piece has overloads, fuses, and breakers for circuit protection, the short never tripped any of these protections. When the problems occurred, it affected other equipment attached to the same MCC distribution panel. That's when I noticed that when I checked voltages to ground, instead of reading 277 on each phase, I would read 480V on two legs and 0V on a third leg.
I checked the earth ground to make sure everything was properly grounded and found the case of the MCC had 0 Ohms to the grounding rod, as well as the building structure and the equipment. Not sure what would cause the circuit protections to be bypassed like this.
Thanks for any help you can give.
I am a part time BSEE student while I work my full time job as an industrial electrician. I ran into a problem that is stumping me that I am hoping to see if any of you have ran into the same issue.
A building that houses manufacturing equipment was commissioned about one year ago, so everything under the roof is new. Twice now, I have run into two ground faults months apart on two seperate pieces of equipment. One was a 480V 3 phase exhaust fan that had a shorted phase to ground, and the other was a heating rod (277V) that also shorted to ground. My problem is that even though each piece has overloads, fuses, and breakers for circuit protection, the short never tripped any of these protections. When the problems occurred, it affected other equipment attached to the same MCC distribution panel. That's when I noticed that when I checked voltages to ground, instead of reading 277 on each phase, I would read 480V on two legs and 0V on a third leg.
I checked the earth ground to make sure everything was properly grounded and found the case of the MCC had 0 Ohms to the grounding rod, as well as the building structure and the equipment. Not sure what would cause the circuit protections to be bypassed like this.
Thanks for any help you can give.
0