Voltage detection in electrical cables

• QuentinChe
In summary, the student is looking for a way to detect voltage on power transmission lines. The tester they are proposing uses magnetic fields or measuring the heat produce with Joule effect.

QuentinChe

Hello guys!
I am a student who currently works on a project based on electrical detection and voltage measurement in electrical cables remotly. So in order to accomplish my work, I'm seeki ng for new ways to detect voltage. I already have some ideas such as using magnetic fields or measuring the heat produce with Joule effect, but it isn't enough (for me at least ) to make good comparaisons, so any ideas will be well welcomed!

Quentin

Welcome to PF.
How far away is "remote" ?
What is the voltage ?
What is the current ?
Is the the current DC or AC, how many phases ?

Also, voltage means a difference in potential between two reference points.
In your project, if one point is a cable, what is the other point? Ground/Earth?
Or are you talking about voltage across a pair of cables?

Voltage does not create heat. Current does.

If you could figure out how to remotely measure voltage on 2 million km of power transmission lines world wide, you could be rich.

dlgoff

I should have been a little more precise, so here's all the informations. We want to make something (a glove or anything else we don't know yet) that will warn an electrician if there is still current flowing in the cable he's going to manipulate. Of course we are not going to work on high voltages instalation, we'll use circuit you can build at school and because it aims to be a modele of the national electricity grid, the current will AC but we haven't make any experiment yet so I can't give you any values (even though I think it will not be over 20V). And last, we don't need to have a 2 kilometer measuring radius, only enough to warn the electrician before he touches the wire

Quentin

QuentinChe said:
I should have been a little more precise, so here's all the informations. We want to make something (a glove or anything else we don't know yet) that will warn an electrician if there is still current flowing in the cable he's going to manipulate. Of course we are not going to work on high voltages instalation, we'll use circuit you can build at school and because it aims to be a modele of the national electricity grid, the current will AC but we haven't make any experiment yet so I can't give you any values (even though I think it will not be over 20V). And last, we don't need to have a 2 kilometer measuring radius, only enough to warn the electrician before he touches the wire
Sounds like the non-contact AC voltage detectors that electricians already use...

https://engineering.electrical-equi...tion/non-contact-ac-voltage-testers-work.html

anorlunda
That's a huge clarification. Thank you. But you need to stop confusing voltage and current. Current can flow even at low voltages. High voltage can be dangerous even when nearly zero current is flowing.

I suggest great caution on this project. Safety for line workers is a very big, very serious topic. A student proposing something unsound and with fuzzy notions about electricity or safety will loose all credibility. In fact, I suggest that you recruit an electric lineman to work with you as an advisor on your project. Contact your local power company and explain your request.

In the link provided by @berkeman, it says the following. Pay attention especially in the parts I marked in red.

Magnetic induction testers
The inductive coupled tester comprises of a sensor winding at the tip. When this winding is placed within the electromagnetic field, a voltage is induced in the winding and used to light or sound an alarm though a circuit within the tester.

A current will only creates an electromagnetic field if it is flowing. And since this tester works by detecting the magnetic field around conductors, it will only work in a if the conductor is part of a complete where current is flowing. As such, it will not indicate anything when there is an energized wire, but the circuit is not complete.

Capacitive sensor element
The tester uses capacitor coupling to detect an electric field and is capable of detecting energized conductors whether in a complete circuit or not.

For the tester to work, the person must touch the metal part of the tester so as to provide a ground reference and allow the stray capacitance from the live conductor to flow to the ground. Placing the tester near a live conductor forms a capacitive voltage divider network. This comprises of the parasitic capacitance between the sensor tip and the live conductor, and the capacitance between the sensor and the ground through the body of the user.

Once the current flows to the ground, the tester will indicate the presence of the voltage through the light or sound.

sophiecentaur and berkeman
anorlunda said:
Safety for line workers is a very big, very serious topic.
I have an account with https://www.ecmweb.com/ and I just downloaded this attached ebook: ECM_Ebook_(Lethal_Combination_final081618.6017fb3b69a40.pdf) that I'm sure ecmweb wouldn't mind me sharing:

[After a discussion between the Mentors and @dlgoff we've decided that instead of posting the PDF, we will just show what is in the document and refer you to their website if you would like to download a copy]

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