Eliminate Induction Voltage

Reduce the separation to 2.8 meters, deenergize the supply to the 6.6 kV line, and let the induction do the job for free, until you get caught.

3 opyions exist for any radiation situation where exposure cannot be avoided.

1 ) Limit Distance of exposure

2 ) Limit time of exposure

3 ) Use Shielding.

You have only one option at your disposal, you must install shielding between the two lines. The shielding will drain inducted energy to ground before it can be pickd up by the other line.

Shielding with Copper/Aluminium Wire Drid is the Best Solution

And you need not ground the Shield .

Induced emfs will drive Currents in the Shield and stop fields inducing emf's into the 6.6KV line .

Thank you; that is correct.

If nothing is grounded, where do the currents go?

Assuming the wires are interconnected in a mesh, any induced currents will be in shorted loops and thus dissipated. As the mesh is also buried, its contact with the earth could also drain induced charges, but most will be in the loops. Buried plate acts as infinitely small loops.

My initial read of the OP was that the lines are not parallel but crossing.

For parallel runs it might be required to place the line in a metal conduit;( a shielded cable) or increase distance of spacing until the induction is within tolerance.

Ah, I see it now; Reading the OP it is unclear whether the word LAID refers to burial or not.

My answers ass u me d buried lines.

I'm assuming that the 4.8m separation is derived from a recognised standard or normal work practice where you are and that this coupling doesn't normally happen?

I recall something about phase conductor positions being alternated mechanically every so often on long parallel runs to help negate the effect. Sorry no reference or citation, just a dim recollection and something observable if you look closely at how these lines are strung up around the country side....not sure about what happens in your neck of the woods though.

Are you the first to have attempted such an installation where you are? Or the first to notice the coupling?

Just how much induction voltage are you getting and how are you measuring it..(feeling it?)?

I had almost the same situation when I came back to open an engineering office for my company in the same area I grew up in. Ironically the facility was where I worked starting college and at that time I tended the only source of power: Generators running 24 hours per day, and in my spare time pumping gas at the service station. The facility had changed owners several times and was now a multimillion dollar casino, but I got involved because the Voltage on the lines 13.2 KV was unballanced. They were going beneath another utilities 230 KV line. (actually 3 parallel 3 phase lines) We measured the voltages before the crossover and after and proved to the utility that this was the problem. (Our contract was with the Utility) The problem was solved by putting a transposition in the middle of the 13.2 KV line so the voltage rise was balanced. Separating it further did little to affect the voltage rise, but the transposition took care of it. We actually did 2 transpositions but I'll let you think about that.

GA! Same solution as using twisted pair wire to minimize noise pickup for signals. The laws of induction are the same.

Hello

we have a crossing place at overhead lines between 170 kV and 420 kV. When 170 kV line was deenergized. We measure 600 Volt at per phase of 170 kV line. Clearence is 7 meters between the two lines. I think there is no solution.

Is the voltage induced magnetically or capacitively? The solutions are different. Twisted pairs or phase exchanges minimize the magnetic pickup while electro-static shields are used to minimize capacitive coupling. In control we use both on the signal cables (it is cheap and easy).

In your case, everything is a lot more involved... But, you should be able to take the proper measurements to define the cause and maybe find a solution to mitigate it.

Otherwise, use a dummy load or a short to ground to reduce this pick-up voltage when the line should be de-energized as per your electrical code and best lineman procedures. Talk to your local experts, They are the ones who can really solve this problem if it is a problem.

WOW!

A little more complicated than twisting two conductors...

I am not qualified to comment on this type of installation.

As I said before, you need to ask real experts in this field.

Have you contacted IREQ? They deal with this all the time.

http://www.hydroquebec.com/innovation/en/index.html

Quote: we have a crossing place at overhead lines between 170 kV and 420 kV. When 170 kV line was deenergized. We measure 600 Volt at per phase of 170 kV line. Clearence is 7 meters between the two lines. I think there is no solution.

Are the line arranged vertically or horizontally? Is it possible to arrange them differently? At that high a voltage is it still possible to have a ground blead off between the two? (height might be a problem) What about going underground through the cross point for the lower voltage line. I see that done a lot in the dessert southwest of the US. The other thing is that the voltage is not that high that the phase in-balance is extreme. About 1/3 % but then you didn't say what the difference between phases was so I assume all the 3 phases are rising some, what is the difference between phases? I would guess that it is less than 0.1 % if that much. what does the metering say on each end of the line. Losses to ground might make more difference than this if it is a long line. 600 volts for a crossover on a 170KV line in unloaded condition may not be all that bad once loads are taken into account. It is the difference between phases that count. I know a lot of lines that require grounding switches to ground the line if both ends are disconnected. Watching them operate when the arc forms, the voltage is way higher than 600 volts. And that is with no lines crossing. If a lineman grounded them manually, it would be really exciting.

We had a 1500 volt difference between phases on the 13.2KV cross of the a 230KV line that was way more than 10% phase in-balance on the example on my previous post. I don't think I would worry too much about 600V out of 170,000, even if it was an in-balance, which from you description it probably is not. But that doesn't mean that you couldn't do anything about it, you could, but I doubt you need it.

< I think there is no solution.>

There IS a solution

Shield With Science of Induced Fields

And Analysis of Induction Vectors.