Power World - Transmissions Line Parameters From Table Data

Welcome to CR4.

Its a good question and I am pretty sure if there is someone with experience in Powerworld you get an answer.

I have none but I had a quick look and there seem to be a handful tutorials available.

Like this one.

Have you looked at those?

Good luck.

Yes, looked at a few, including that one, but didn't find a satisfying answer for the transmission line parameters.

Thanks for your reply.

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First of all, welcome! You don't have be crazy to join us, by the way. We train you!

Does your conductor resistance take into account skin effect? For aluminum conductors at 60 Hz the skin depth is about 10.5 mm (~11.6 mm @ 50 Hz). This means that for a 1 1/2" (38.1 mm) diameter transmission line only about 2/3 of the conductor's cross section is carrying the (bulk of the) current, more at 50 Hz, but both increase the effective resistance.

Isn't PowerWorld supposed to take this into account?

I think OP should add up the impedances, and consider how many strands are needed, right? Probably multiplying by 1.5 is a good design practice if he wants a reliable TL.

I dunno about PowerWorld, but I know RealWorld does.

LOL, I have to provide you a GA for that one! I think we will have many good conversations in the future.

You would split capacitance into two halves to make Pi-equivalent.

I would assume basic units are ohms for reactance, resistance. Make a basic series R, shunt L or C network. Make R =10, X = +/- 10. See if output amplitude = 1/√2 of input with +/- 45 degree phase angle and input current corresponding to 10√2 ohms.

Or you could work from simple shunt resistance etc versus current drawn to identify units.

The TL parameters that you have are simply the starting point in determining the quantities that you seek. The resistance and reactance shown account for the affect of frequency, temperature, and skin effect. Two conductors in free space with a one foot center to center spacing is chosen since reactance also depends upon the physical arrangement of the conductors.

So the question should be, "Why two conductors when we're talking about a three phase system?" That's because the modeling starts with a single phase system (hot wire and return) and gets extended to a three phase system (three conductors and a ground return) by a whole series of arcane calculations that take into account things like: the arrangement of the conductors, their actual spacing, their height above the earth (ground return), whether there is a second circuit on the same tower (proximity effect), whether there is a lightning protective conductor, if the line has any transpositions and how they are made, the soil resistivity, etc., etc.

Simplified(?) explanations and derivations can be found in the 30+/- pages of Chapter 3 in the Westinghouse T&D Reference Book; otherwise you can consult any good textbook on transmission line engineering. There you will find such interesting terms as GMR (Geometric Mean Radius) and GMD (Geometric Mean Diameter) that are essential in determining the electrical characteristics of an overhead transmission line.