back feed thru ground

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Tom@aecom

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Tamps, Florida
I recently had a partial power outage at my own residence. Half of the house was powered and half was not. I thought a phase had gone out on the power pole transformer. Duke power arrived and it turns out that one phase of my incoming power at the service loop at the drip head was out. There was an apparent loose connector on one phase and it melted the connector. The broken phase wire was dangling from the service loop separated by about four inches between the connector and the wire coming off the power pole. The loads on half of the house were coming on and off at regular intervals while the other half of the house that was still powered by the intact phase conductor stayed on steady. I asked the line man that was there to do the repair how was it possible for one side of the power panel loads to continue to be powered intermittently. That is coming on and off about every 15 or so seconds. He said that it was being back fed thru the ground! He proceeded to install a new connector to one side of the phase wire. I could see the power going on and off inside the house from where I was standing outside. Right before he connected the other side of the phase wire to the connector he asked if the lights were still going on and off. They were and after he made the final connection the lights came on steady.
Can you explain how this is possible? I don?t see how the circuit was completed thru a back feed and if it was why it would go on and off like it was.
 
My thought would be that once any load that was connected to both phases (water heater, heat, range, ect) switched "on" there would be "feed thru" voltage flow from the live phase back to the open phase.
 
If you have 240 volt loads such as an electric water heater then one phase is hot and feeds thru the element back to the breaker which in turn energizes the other phase. Since there is an element involved the resistance of the element makes it so that the current available is lower and the lights generally will not light as brightly as it should. Other loads coming on and off will make the lights flash and change in intensity
 
As others have said it is backfeed, but from the other line via 240 volt loads, not via the ground.

Water heater is one of biggest culprits for this to happen, maybe followed by electric heaters direct controlled by a thermostat. Most other appliances need full 240 volts to power controls/control transformers or other things to happen before there is a closed circuit in which backfeed can occur.

Now that circuit breakers are dominant overcurrent protection method for most dwellings or light commercial applications you don't see this too often, but you used to see it a lot when there were more fuses used as service or feeder protection and you had a blown fuse as the same situation would occur then.
 
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