Induced voltage on pipeline parallel to overhead conductor 2

[ASimmons23]

Hi all,

I have a problem where I need to calculate the induced voltage of a pipeline running parallel with a 34.5kV 600A unshielded transmission line (500kcmil) and the pipe is approx. 20m from the line. I have read many articles about the effects of induced voltage on pipeline but have yet to find any articles calculating the actual induced voltage. Any suggestions? Thanks..

 

[dpc]

The pipeline is above grade?

This will also be somewhat dependent on the configuration of the overhead line and the current magnitude, possibly.

 

[ASimmons23]

yes pipe is above grade for a short run and is grounded to the existing piperack. overhead configuration is 3 unshielded single conductors and a ground but I am trying to solve the problem as if it were a single unshielded transmission line. It has to do with the magnetic field creating an induced voltage on the pipe I just can't seem to find any calculations of this kind.

 

[davidbeach]

You should get very little induced voltage for normal load current. What you need to be concerned with is the induced current (and the voltage that will create) during ground faults (earth faults) seen by the power line. If you can determine the "conductor" properties of the pipe the calculations are just the same as they would be for coupling with another line. The big problem will be determining the [Ω] per unit length and the equivalent GMR.

 

[ASimmons23]

Thanks for the quick response, david you have reaffirmed what I have been thinking about short circuit analysis being most important here. Now to find me some conductor properties..

 

[davidbeach]

Good luck. Calculating the GMR of a copper or aluminum conductor is a mathematical exercise. Calculating the GMR of a conductor that includes a steel core is far more involved and that of a completely steel conductor even more so. For the steel core case I understand you can make a reasonable approximation (I've never tried, I always just use tables of properties) by assuming that all of the current flows in the aluminum strands and the steel is only for strength, but if all you have is steel you have to let the current flow in the steel and then you are into the ferro-magnetic properties of the steel.

 

[jghrist]

See

http://www.sestech.com/Products/SoftPackages/ROW.htm

 

[veritas]

Hi ASimmons23

I have been studying this myself for a while and have a spreadsheet that can do excatly what you want. But as davidbeach pointed out, there will be very little induced voltage under normal balanced load conditions but there will be some, depending on how far the pipe is from the transmission line. The induced voltage is not dependant on the the pipe itself (the resulting current is if there is a closed circuit)and thus you need not worry about pipe GMR if you only wish to calculate the induced voltage.

You will need the GMR of the overhead conductors and the spacing of the conductors from each other and earth (including any overhead earth wires). As davidbeach also pointed out when the transmission line is carrying EF current then the flux enveloped by the pipe due to the current in the conductor(s) is much larger as there is no cancellation effects between the fluxes from the conductor's phases as is the case with positive sequence current.

This zero sequence mutual coupling is of more concern as part of the EF return current can also flow in the pipe.

With regards to my spreadsheet, I am willing to share it with you but it is in metric units as that is what I work with here in Australia. If you are willing to do any conversions necessary then you are welcome to it.

Regards.

 

[ASimmons23]

Thanks again for all the contributions. I have since found confirmed that under normal conditions (non fault) there is minimal induced voltage (something like 7 micro volts). I would still be interested in studying your spreadsheet though.

Thanks!

 

[resqcapt19]

The documents posted here may be of some interest.

http://www.icc.illinois.gov/e-docket/reports/browse/document_view.asp?id=7209&did=108504

These were posted in oposition to the routing of a proposed 138kV line in my area.