Voltage drop in parellel circuits 2

[Mbrooke]

How do parallel circuits effect voltage drop? How would you go about modeling the mutual coupling terms of voltage drop? Or do I just model them as a single circuit when factoring VD?

 

[davidbeach]

The only mutual coupling that has any particular significance is between zero sequence currents. The rest exist, whether in the phase domain or the sequence domain, but they’re orders of magnitude smaller.

Assuming your voltage drop calculation is for load conditions rather than fault conditions you can safely ignore the affects of the mutual coupling.

 

[Mbrooke]

Thank you- this is load voltage drop on a sub-transmission circuit. Reason for my ponder is because of this graphic I came across in a distribution engineering handbook.

https://files.engineering.com/getfi...a-bc14-50d3fd99cc47&file=mutual_induction.jpg

 

[davidbeach]

Yep, that's true, but only in the zero sequence is there enough coupling to matter. Looking at one section of a two line right-of-way picked at random from our line data I see the zero sequence mutual coupling being 0.00018+0.00062j while the other mutuals (nine total for two lines) range from 8.36777*10^-7+4.80292j*10^-6 to 5.26882*10^-6+4.56966j*10^-6. With the uncertainties in modeling, the two or three orders of magnitude difference means that the rest are almost always ignored.

 

[waross]

If the circuits are in parallel then the final voltages must be equal.
If the parallel circuits are not the same route, length and spacing, the PF of the voltage drops in each line may not be equal.
In that case the current sharing may not be equal.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[HamburgerHelper]

If you have ATP-EMTP you can model it and see the magnitudes of all the coupled components. You should see just what David says. The only time I have seen the other coupled components even mentioned was for some methods used for fault location.

http://www.ece.mtu.edu/faculty/bamork/ee5200/LineConstantsHKH.pdf

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If you can't explain it to a six year old, you don't understand it yourself.

 

[Mbrooke]

Thank you for all the replies I am saving the PDf to the hard-rive.