Engineering Transmission line 3 phase double circuit problem

[toup]

Hi, i just need some help with something, I have been given a question to solve. I need to find a) sending end current, b) sending end power factor c) full load active power losses of a three phase "double Circuit" transmission line...I know how to calculate all of those for a three phase "single circuit" transmission line...but how do you calculate for a "double circuit" three phase transmission line...the transmission line is medium length with following parameters

50Hz, 330kV, 360MW at 0.82 power factor lagging load is to be
supplied by 330kV, 50Hz, 160-km three phase double circuit. Each circuit has
a per phase resistance of 0.00012pu/km, reactance of 0.00099pu/km, and shunt
susceptance to neutral of 0.46174pu.

Please no need to calculate all of the above...just help me out on what a double circuit 3 phase transmission line is and how to calculate its parameters.

Any help is much appreciated...thank you

 

[gerbi]

Isn't that a line with two wires per phase ?

 

[toup]

wouldnt that make it a "bundled" circuit?...the question specifically says "double circuit" and not bundled circuit...so I am just a little confused

 

[toup]

thanks for the reply btw

 

[gerbi]

How about looking here:
http://en.wikipedia.org/wiki/Overhead_power_line

A double-circuit transmission line has two circuits. For three-phase systems, each tower supports and insulates six conductors. Single phase AC-power lines as used for traction current have four conductors for two circuits. Usually both circuits operate at the same voltage

http://en.wikipedia.org/wiki/File:Pylon_ds.jpg

 

[toup]

ok so when the question says Each circuit has a per phase resistance of 0.00012pu/km...the total per phase resistance would be 2 x (0.00012pu/km)...this sounds too simple to be true though

 

[gerbi]

Connecting wires in parallel means dividing resistance not multiplying it my friend.
And one more thing, I'm not an expert.. but what happends when two 3-phase 160 km long systems operates so close ? Aren't they electromagnetically coupled ?

 

[toup]

yep you are right about both being parallel and the magnetic coupling makes sense...but not sure how to calculate that