Induced voltage on parallel transmission lines
Induced voltage on parallel transmission lines
(OP)
Hello,
Is there a way of calculating what induced voltage would be present on an adjacent de-energized line that runs parallel to another line that is energized? both lines are 345kV.
Is there a way of calculating what induced voltage would be present on an adjacent de-energized line that runs parallel to another line that is energized? both lines are 345kV.






RE: Induced voltage on parallel transmission lines
How long are they in parallel, and how far apart are the two centers of the lines? (tower-tower distance)
Is the de-energized line grounded out on all phases and all lightening wires so seldom that there there is appreciable voltage buildup between the parallel section and the grounding point?
RE: Induced voltage on parallel transmission lines
RE: Induced voltage on parallel transmission lines
I've done this calculation using the matrix function in Excel and it works fine.
There's also information on this in the EPRI Red Book.
RE: Induced voltage on parallel transmission lines
both lines are 345kV. Line energized with 890A loading with 35km in parallel with 50A induced current at de-energized grounding line. Ground line switch were changed
RE: Induced voltage on parallel transmission lines
RE: Induced voltage on parallel transmission lines
RE: Induced voltage on parallel transmission lines
One utility flagged a 50 foot square area so that no-one could approach within 25 feet or more of the temporary field ground rod.
Bill
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"Why not the best?"
Jimmy Carter
RE: Induced voltage on parallel transmission lines
Assume a thirty mile run, with the two lines in parallel for only 4 miles of the 30. The entire line becomes charged from the induced EMF, doesn't it?
RE: Induced voltage on parallel transmission lines
When a line is initially isolated deenergized, the conductors may have a trapped DC charge. The trapped DC voltage may takes cycles to minutes to decay depending upon how much leakage occurs across insulators and through instruments transformers & surge arresters.
Yes, the entire line would have induced voltage. If you measured the voltage on the entire ungrounded 30 mile line, it would probably have a lower voltage than if you isolated just the 4 mile section and measured the voltage on just the parallel section.
RE: Induced voltage on parallel transmission lines
Attached is an example of what can happen when things go wrong.
Regards
Marmite
RE: Induced voltage on parallel transmission lines
One is the capacitive effect. The energized conductor and the de-energized conductor separated by an insulator, air, form one capacitor. The de-energized conductor and the ground form a second capacitor. The simplified circuit is two capacitors in series.
The second effect is magnetic induction. The lines of force caused by the current in the energized conductor cut the de-energized conductor and induce a voltage in the second conductor.
The capacitive effect depends mostly on spacing. The magnetic induction effect depends mostly on spacing and on the magnitude of the current in the energized line.This is in accord with my understanding of the magnetic induction effect.
We have mostly been considering the open circuit voltage. The current sourced by each type of induction will increase with the length of the line.
Bill
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"Why not the best?"
Jimmy Carter