Stray Voltage on Incoming Power, is this a Problem?

[dalmatiangirl61]

I returned to the home/shop last night to find I had lost 1 leg of the 240v single phase power coming into building, power co was called and they found a wire connector at transformer on pole was burnt, quick easy fix. After repairing that connector they wanted to check power coming into my place so they pulled the power meter and started probing terminals. L1 to L2 240v, L1 to ground 120v, L2 to ground 120v. But when they probed L1 input terminal to L1 output terminal it showed 27v, and L2 input terminal to L2 output terminal showed 20v??? The guys first comment was "you must have forgotten to turn off a breaker", I then pointed out that main disconnect was 10ft away, and it was open.

So I'm trying to figure out why there would be voltage the way he tested it if the main disconnect was open, it makes no sense to me. Next question is, is this a problem? If it is a problem, what should I be looking for?

 

[SomeoneSomewhere]

Measuring voltage on floating conductors often gives you weird readings. Many meters have a low-impedance/Lo-Z function specifically to avoid this.

They were essentially ending up with a voltage divider between the meter's 10Mohm internal resistance, and the leakage resistance/capacitive coupling to ground, of the output wires.

 

[dalmatiangirl61]

Measuring voltage on floating conductors often gives you weird readings. Many meters have a low-impedance/Lo-Z function specifically to avoid this.

They were essentially ending up with a voltage divider between the meter's 10Mohm internal resistance, and the leakage resistance/capacitive coupling to ground, of the output wires.

So nothing to worry about? He also made some comment about "losing voltage" and that had my mind wondering. Normally I would have queried him more, but after 2 hours outside in sub freezing weather I'd lost my chatty nature. Thank you.

 

[SomeoneSomewhere]

I wouldn't worry about it. Ideally the conductors should be meggered to ground and each other with the meter removed and the disconnect opened, but a) no-one in the US bothers with actual proof testing, and b) the meter is now installed so good luck with that.

What's being described there is possible insulation issues - nothing to do with loose connections, heating, or volt drop.

 

[Donkey Hotey]

If you want to be super sure, make a test load with an incandescent light bulb and two lengths of wire (old trouble light, table lamp or?). Hook the lightbulb up between each input and output terminal and then measure for voltage. If it lights the bulb, you have a problem. If you hook it up and then touch the leads of the multimeter and show zero, it was super low wattage noise being capacitively or inductively picked up in the wires.

 

[JST]

Yes.

Use a

I wouldn't worry about it. Ideally the conductors should be meggered to ground and each other with the meter removed and the disconnect opened, but a) no-one in the US bothers with actual proof testing, and b) the meter is now installed so good luck with that.

What's being described there is possible insulation issues - nothing to do with loose connections, heating, or volt drop.

Mostly it is likely capacitive current between the wires of the power cable to the service entrance box. With a 10 meg meter resistance, it does not take much current to make a reading.

If you use a n instrument such as a "Wiggy", it will respond only to genuine currents, ignoring even minor resistive leakages.

Just as "everything is made of rubber", in electrical terms, "everything is a conductor of electricity". In both cases, it is a matter of "how much" like rubber or a conductor the thing is.