Zero Sequence Impedance Calculation
Zero Sequence Impedance Calculation
(OP)
Does anyone know of a tech literature source that describes a way to calculate the zero sequence impedance of three phase circuits in grounded steel conduit? The process for overhead circuits is straight forward, following the methods in "Symmetrical Components" by Wagner&Evans, however it doesn't cover what I'm looking for.






RE: Zero Sequence Impedance Calculation
see Thread238-99311
RE: Zero Sequence Impedance Calculation
RE: Zero Sequence Impedance Calculation
Paper is "Let's be more specific about equipment grounding" from Proceedings of the American Power Conference, 1962, by R.H. Kaufmann. I would highly recommend trying to get a copy.
RE: Zero Sequence Impedance Calculation
Caculations of fault current is very complex due to the fact that the affect of the steel on the impedance of the cable varies with the magnitude of the fault. This site
http://www.atcelectrical.com/links.php is the site of Allied
Conduit. They along with Ga. Tech University developed a program that will caculate fault currents within steel conduit. I hope this will be of some help to you.
RE: Zero Sequence Impedance Calculation
RE: Zero Sequence Impedance Calculation
1- Determine the Positive/Negative cable impedance using the conventional resistance and reactance equations with actual electrical and physical cable parameters provided by cable manufacturer.
As alternative to calculate positive reactance, use the enclose nomogram:
http:
2- For magnetic conduit, a simple approximation may be estimated as follow:
Zo= Ro+j.Xo =π.(R+)+ 2.5j(X+)
Other simplified approach is to obtain directly the impedance from table. For example consider the enclose information for 3-conductor zero sequence impedance with galvanized steel interlocked armor. This may be similar than the 3-single conductor cables in steel conduit but add additional allowance (ex. 20% to 25%) to compensate for cable random lay and transposition.
Please see the enclose impedance data and assumptions how this information was developed.
http://