Transmission line 3 phase double circuit problem

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Discussion Overview

The discussion revolves around the calculation of parameters for a three-phase double circuit transmission line, specifically focusing on sending end current, power factor, and active power losses. Participants are exploring the differences between single and double circuit configurations and the implications of these differences on calculations.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant seeks clarification on how to calculate parameters for a double circuit three-phase transmission line, having prior knowledge of single circuit calculations.
  • Another participant suggests that a double circuit line consists of two wires per phase, leading to confusion about the terminology used in the question.
  • There is a distinction made between "double circuit" and "bundled circuit," with participants expressing uncertainty about the correct interpretation.
  • A participant references external sources to explain that a double-circuit transmission line has two circuits, with each tower supporting six conductors for a three-phase system.
  • Concerns are raised about the calculation of total per phase resistance, with one participant questioning whether it is simply double the resistance of a single circuit.
  • Another participant corrects the misunderstanding about resistance in parallel circuits, emphasizing that connecting wires in parallel results in reduced resistance.
  • Participants discuss the potential electromagnetic coupling effects when two three-phase systems operate in close proximity, indicating a need for further exploration of this phenomenon.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of "double circuit" versus "bundled circuit," and there is no consensus on how to approach the calculations for the parameters in question. The discussion remains unresolved regarding the specifics of the calculations and the implications of electromagnetic coupling.

Contextual Notes

Participants have not reached a consensus on the definitions and calculations related to double circuit transmission lines. There are also unresolved assumptions regarding the effects of electromagnetic coupling between closely operating systems.

toup
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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
 
Last edited by a moderator:
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Isn't that a line with two wires per phase ?
 
wouldnt that make it a "bundled" circuit?...the question specifically says "double circuit" and not bundled circuit...so I am just a little confused
 
Last edited by a moderator:
thanks for the reply btw
 
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
 
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 ?
 
Last edited:
yep you are right about both being parallel and the magnetic coupling makes sense...but not sure how to calculate that
 
Last edited by a moderator:

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