Consider: a line worker 'bonded on' to a high voltage line. They are working bare handed on that line. What is the danger mechanism if they use a clamp meter on the line?
There is, of course, the separate question of getting an accurate measurement. What would the electric field do to the meter, and are there any concentric neutral or semiconductive layers that are part of the insulation system and carrying current?
I have used a clamp-on meter for many years on MV systems but I have always been in a tested, rated bucket or at a point where the conductor is insulated (less the CN, of course). In modern times, I added the use of tested, rated gloves. Of the untold times and number of meters I have used, no meter has ever been harmed. By being in the bucket and using the gloves, the meter is "bonded" to the line and the voltage isolation takes place across the bucket truck and gloves, not the meter.
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DO NOT EVER DO THIS WITHOUT BEING ELECTRICALLY ISOLATED. MOST METERS CAN ONLY HANDLE 1KV AT MOST ACROSS THEIR INSULATION. THE METER IS NOT RATED TO INSULATE YOU AT THESE VOLTAGES. THAT IS WHAT THE BUCKET AND GLOVES ARE FOR.
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For voltage measurements, we have portable meters that are designed to handle the high voltages.
I figure that the problem is that you have parts of the meter/measuring circuit that are at relatively high impedance, and thus not presenting a very big load. Put them in the kV/cm electric field that we are talking about, and the voltage induced might screw up the measurement or even damage the meter.
I have never had a problem. I suspect it would be an issue at high voltages but not at 4 kV. I would not attempt it at 500kV as I have heard the static is awful (and hurts). I have done it on 25 kV systems but would not be concerned even on a 46 kV system.
I have used flexi-cts snapped around the base of higher voltage bushings with no problems but at the higher voltages, there is usually a CT at the interesting points of the system.
Here is how the MV guys do this, find a CT, they will be everywhere. Take a clamp on reading on the seconday side of the CT and multiply the reading by the CT ratio. Do not open the secondary of the CT. And you lwill need the correct PPE, that can vary greatly depending on where you can access the CT secondary.
While they may be everywhere in some settings, CTs are certainly not everywhere on a utility distribution system.
In fact if you read my post I wrote "I am guessing a smoked meter".
If you do this while not isolated from other sources and ground, that would be a good guess but add a smoked person to the list.
