| I put a clamp on meter on the main cable from the meter into the panel and | noticed an imbalance (should read 0). Next, I checked the ground cable going | to a water pipe and found the same current flowing. I checked the pipe from | the ground clamp side to the house and the clamp to the water main and all | the current was heading to ground. | | The houses on the street are delivered power from a low voltage bus on the | poles. What I mean is each house does not have its own transformer. There is | a transformer on every other pole that is connected to the LV bus line. I'm | thinking, imbalance current on the neutral line is getting carried back to | the transformer through the water line (city water system), back up | someone's ground to the transformer since the other houses are connected on | a different part of the bus. Does this make sense? Is that excessive | current? Should the utility check it? | Thanks
There should be a connection between the neutral on the bus wires between the poles, and the transformer neutral terminal, as well as a ground wire to earth at the pole the transformer is on. If the connection between the bus and the transformer is broken, then the only return path for imbalance current is through earth. Since every house should have the neutral that comes off the pole grounded, each one of those serves as a parallel path through earth back to the earth ground wire at the transformer.
A neighbor has a broken or loose neutral in their service drop, but their neutral in the panel is still grounded (perhaps through the water pipe). Their current imbalance is flowing out the earth ground (maybe water pipe) and using parallel paths back to the transformer, some through the ground wire at the transformer, and some through each neighbor (and you) entering via the ground and going back up the service drop to the transformer.
Same as scenrio 2, but you are the one with the broken or loose neutral in the service drop.
The neutral wire of the medium voltage distribution circuit connected to the transformer primary is typically connected to the secondary neutral, and both connected to ground. Thus, there is a metallic path between your neutral wire and the neutral of the medium voltage distribution wires. If there is a broken neutral between the transformer primary and the distribution, either at the transformer, or further down the line, then the primary current trying to return to the upstream source will flow through the ground wire on the pole, and find parallel paths back to the source. In the simplest case, the neutral is broken at that transformer, and each service drop, plus the pole ground, are parallel paths through earth to other service drops of houses on other transformers with OK neutrals, providing a working return path. At medium voltages, typical earth resistances divided by all these parallel paths can still result in a working system with little voltage drop.