Gentlemen:
In my understanding, it has been speculated in this thread that current can flow from one terminal of an AC source to an insulated conductive body and that this does not rely on capacitance, which is defined as two conductive bodies seperated by an insulator.
An experiment was posted in which an AC high-pot tester had one lead attached to a suspended conductive body and an ammeter did indeed indicate a current flow back and forth to the conductive body. It was speculated that this current flow has nothing to do with capacitance. The term "electron reservoir" was used in conjunction with the conductive body.
Now, during this experiment, it was said that the other terminal of the high-pot tester was connected to the earth.
If I am viewing this experiment from the moon, then it is obvious to me that the earth is nothing other than a huge conductive body. In actuality, it is no different than the other conductive body, only much larger. There is nothing special about the earth in this experiment. And it (the earth) is attached to one terminal of the high voltage source. Whatever laws of physics are acting on the small conductive body and causing current to flow to it must also be acting on the other conductive body too (the earth).
This leads to the following:
1) The lead going to the conductive body is always of opposite polarity compared to the lead connected to the earth. It follows that the conductive body will always be of opposite polarity to the earth. Anytime that the conductive body is negative, the earth will be positive, as compared to each other. And anytime the conductive body is positive, the earth will be negative compared to each other. Now, the very definition of a capacitor is two oppositely charged conductive bodies seperated by an insulator. The conductive body and the earth form a capacitor.
2) If we remove the small conductive body from the experiment, we still have the earth connected to one side of a high voltage source and this source is constantly changing polarity in respect to the other terminal of the source. It follows that the earth is also constantly changing polarity in respect to the other side of the source. If the speculated theory is correct (and using the exact same mechanism which caused current to flow to the small conductive body), then a current must flow between the earth and the terminal of the high-pot tester. After all, what is the difference between one terminal of the source connected to the small body , or the other terminal of the source connected to earth? (It isn't because that terminal is grounded. The ground connection is simply a connection to a large conductive body and all the laws of physics still apply. The earth is in fact, simply a conducting body and no different than the other conductive body except for size.)
3) I suspect that the metal chassis/enclosure of the high-voltage tester is connected to one side of the high voltage source. If this is true, and assuming the speculated mechanism is true, then current must be flowing continuously between the chassis/enclosure and the source terminal that it is connected to. This would be regardless of whether the small conductive body was connected to it or not. And the speculated theory says this current is not due to capacitance.
4) If the specualtion is true, the high-pot probe itself is actually a conductive body attached to a source terminal. So current should be flowing back and forth from the probe to the source terminal it is connected to. The high-pot meter should read something even when nothing is in the vicinity of the lead. It would probably be said that since the probe is relatively small, it doesn't take much current to equalize it to the changing polarity of the terminal. The current may be so small, it can't be measured.
5) Let us consider the speculation to be true that it only takes one wire to a conductive body to cause current to flow and "equalize" the voltage on the terminal and the conductive body, and that this does not require capacitance. An extremely small conductive body would not require very much current to equalize it to the terminal it is connected to, as in #4. A slightly larger body would require somewhat more equalizing current. It follows that a larger conductive body would require even more current to "equalize" the body. Now, the current required to "equalize" the earth to the terminal it is connected to would be tremendously huge, possibly thousands of amps.
If there is a hang-up with "but you are wrong because one of the high-pot leads is grounded and ground is the reference, and therefore doesn't change", well you are wrong. It is just as perfectly valid to claim the small conductive body is going to be the reference as it is to claim the earth is going to be the reference. The same laws of physics and the same current flows will occur regardless of what point I choose as the reference.
For example, take the service at your house. We can use the neutral point as the reference for all voltages and current flows in the system. But we could just as easily claim that one of the phase terminals is to be the reference, and the physics and math would still be the same. Sure, some polarites would change, some of the data would be different, but any equations and laws would still compute to the same answers for any variable in the system.
Another point to consider - take a delta 3-phase 3-wire system. According to the speculated theory, any conductive body attached to a phase wire is going to experience a continuous equalizing current flow that has nothing to do with capacitance. To keep this body at the same potential as the phase wire, there must be a constant current flow.
If we connect a conductive body to only "C" phase, the specualtion is that non-capacitive current should flow. If we connect a larger "electron reservoir" to "C" phase, even more current would flow. It follows that if we connect "C" phase to a conductive body larger than the earth, then a very large current should flow.
If we connect "C" phase to the earth as in a grounded phase delta, then "C" phase must keep the earth at the same potential as the phase. To do this, a current must flow between the phase and the earth.... most likely a huge current flow. And it isn't capacitive current according to the speculation.
Now, again, to defend the speculated theory, a person may say that the earth is the reference and doesn't change polarity. But that is only because we are standing on earth. If I was standing on a conductive body connected to "A" phase, then I would say THAT conductive body is the reference, not the earth. My physics and calculations done from my perspective would derive the exact same current flows as someone else from a different reference point.
There is nothing special about the earth that makes it different from any other conductive body we connect to a phase wire. It just so happens it is convention to accept the earth as reference. It doesn't mean we have to. We can choose anything we want to for the reference. As long as we are consistent, the calculations will all derive the exact same results.
It appears that the specualted theory leads to some absurdities. I therefore believe the specualted theory is false. Capacitance is the mechanism behind the current flows.
For anyone who has bothered to read this far: There are some more points to be made based on the movement of electrons to the conductive body and where these charges are coming from. Whenever electrons move, there will be positive charges left behind. These positive charges in turn attract more electrons. And so on and so on, all the way back to the source, then through the source, and in the case of the high-pot, then to the earth, and then through the earth from the point where the negative charge in the conductive body is repelling those very electrons in the earth.
Hi-pot experiemnt: Capacitance between the conductive body and earth and any other grounded items in the area.
Helicopter: Capacitance between individual phases, the earth, and the helicopter.
Thanks for reading!:smile:
