As far as single point voltage indicators, this Wiki page gives a description.

https://en.wikipedia.org/wiki/Test_light

It's possible that the measurement van is using the capacitive reactance of the vehicle itself as a coupling method to ground.

There's a LOT of 60Hz a.c. floating around. If a circuit doesn't have equal currents flowing to and from the device wires, it will radiate 60Hz. That's the difference between a transmission line and an antenna at radio frequencies. Given enough amplification, I think 60Hz could be measured/sensed.

This is a slip shod method for checking ground fault failure in street lighting and ignores physics. There are devices called electroscopes and these are widely used in any environment that uses explosive gases. They determine static charge by sensing the efield. But the static efield varies with relative humidity. The average efield value of the efield of AC is zero. We have to measure the instantaneous value or the Root Mean Square value and adjust for distance as the efield varies with distance and relative humidity.There is no AC electroscope that can do this. There are good EMF devices that can measure EMF fields but the overpowering EMF signal would come from arcing because of its wide wave band. Great advances have been made in signal analysis and I can not rule That useful information can be scanned. However, this can not in anyway replace direct contact inspection. By the way while the electroscope can sense voltage directly the multimeter has to do a measurement indirectly. That is why the old Simpson meters loaded the circuit. Solid state devices such as the FET load also but to an insignificant degree.

My I agree with you Mike, stray voltage sounds like my dog ran away.. The wife calls it, "Voltage gone wild" which may just a more accurate desription

Can't wait for this technology to evolve to my multimeter

that was very interesting.

More usefull info from Mike Holt.

Mike,

The IEEE is working on a new document to help clarify the difference between Stray voltage and Contact voltage but it will take time before people truly understand the difference.

I thought that "Stray Current" was a more appropriate term, but I could be wrong.

Please, if anyone knows of a commercial or scientific device That can pick up electrical potential difference between two points from that distance I sure would like to know about it.The implication is that this device can determine if there is an alternating electrical potential difference between the pole and the earth whose cause could only be a failure in the prescribed fault carrying conductor. The on board screens show a typical signature one would get from the wide frequency band of an arcing circuit.

Who is the intended audience of this video? If it is trained electrical professionals, then I agree, contact voltage would be the more appropriate term. If it is the public at large, stray voltage is probably a better and more meaningful term. The word stray indicates that there is voltage in a place where it should not be. Thanks for sharing the video Mike!

I think it is pretty clear from the pole example that they are not picking up arcing. What is mounted on the truck seems to be just a very sensitive non-contact voltage tester which is tuned to 60Hz. If the energized surface was just, for example, the small handhole cover plate it would be less sensitive. Live wires not shielded within a raceway would also be picked up (the overhead mentioned), while service wiring with a concentric neutral acting as a shield or an L1-L2 pair with balanced voltage would not show up at that distance.

I think this test / remedy should be followed by another trip around the block and a 'final pass' with the equipment that first indicated the hazard.

Well said Mike Holt.I also dislike what is often intentionally miss used terminology solely for dramatic affect.

Yes, I'd agree that the reference to this being stray voltage is misleading. Correct terminology would be contact voltage although the condition ideally results in an energized structure situation.

They are picking up the electromagnetic signal of arcing and not fault voltage or the potential difference of the pole to the earth. To measure or detect voltages at least two reference points are needed. There can not be a voltage difference if you do not have a difference. One may argue that they are detecting an electric field which does not rely on a current. That is possible but a universal axis of multiple detectors are needed. The electric field is polarized. I know of no electric field detectors that would work at the distances shown and do it while moving. Magnetic fields or electromagnetic fields can be detected and that is what they are detecting from something serving as an antenna but most probably from arcing.