Ground harmonic currents
Ground harmonic currents
(OP)
I work for at a production facility for a petroleum company. We have an uninterruptible power supply UPS feeding an offices block (computers, printers, communication systems and so on). The UPS is supplied through a 480/208 D/y transformer (secondary solidly grounded plus neutral conductor). I measured neutral and ground currents and found that the values are almost equal (2 Amperes). Furthermore, those currents were found to be triplen harmonics (180 Hz) althogh their values were negligible when compared to phase currents (65 Amperes,60 Hz). The question is, Why neutral and grounding conductors carry similar currents?. Could be that situation dangerous despite the low values of the currents?. I think that a bond between neutral and ground might be downstream the transformer, What's your opinion?
All comments and suggestions are welcome






RE: Ground harmonic currents
Equal currents = parallel paths.
That is there is a neutral-ground bond
somewhere downstream. It should not be difficult to track
down, but will probably require an outage.
RE: Ground harmonic currents
RE: Ground harmonic currents
One value the doesn’t seem to be mentioned is the current on the transformer-secondary bonding jumper between the grounded-circuit conductor {“neutral”} and (“green”) equipment-grounding conductor. If 2 amperes is not causing any unsafe or inefficient operation, particularly if the loads are substantially 1ø switchmode power supplies, it's probably best forgotten, or checked again in a month or a year.
RE: Ground harmonic currents