ptonsparky
Tom
- Occupation
- EC - retired
Trying to get rid of ground loops at a dairy owned transformer 480 to 208 Y.
Existing installation had three taps coming from the secondary of the transformer with a system bonding jumper in place.. Bonding occurred again at 4 locations. Grounding electrode was not present at transformer but is at two remote locations. To be changed.
We removed the bonding at two of the panels that are in/on the same building that houses the transformer. We installed two rods and attached the GEC to both the 480v GC and the XO of the xfmr. We now have 5 wire feeders to each local panel or disconnect location. EGs to each are located in a series of stacked lugs attached to the left inside of the enclosure. I did not want to rely on the 10-32 screw threads so a #4 cu ties the EG lugs to the same location as the system bonding jumper. Bottom right.
We were really surprised to find 6 amps of current flow on that short jumper. This is with the xfmr energized and no loads connected. No current flows on the GEC to/from the rods. Lesser amounts flow on each of the EGs but don?t total 6 amps. Is this normal to have that kind of circulation at a Xfmr? If it means any thing the current waveform looks like the wave on a slop bucket.
Existing installation had three taps coming from the secondary of the transformer with a system bonding jumper in place.. Bonding occurred again at 4 locations. Grounding electrode was not present at transformer but is at two remote locations. To be changed.
We removed the bonding at two of the panels that are in/on the same building that houses the transformer. We installed two rods and attached the GEC to both the 480v GC and the XO of the xfmr. We now have 5 wire feeders to each local panel or disconnect location. EGs to each are located in a series of stacked lugs attached to the left inside of the enclosure. I did not want to rely on the 10-32 screw threads so a #4 cu ties the EG lugs to the same location as the system bonding jumper. Bottom right.
We were really surprised to find 6 amps of current flow on that short jumper. This is with the xfmr energized and no loads connected. No current flows on the GEC to/from the rods. Lesser amounts flow on each of the EGs but don?t total 6 amps. Is this normal to have that kind of circulation at a Xfmr? If it means any thing the current waveform looks like the wave on a slop bucket.