Recent content by relayman1000

jghrist, Thank you. Yes, as I see it if you assume that there is a return path of 0.0 ohms the only difference between the positice and zero sequence impedances is because of the mutual coupling between 3 phase currents that are 120 degrees out of phase and the different mutual coupling...

Magoo2, yes that helps. In fact, based on your previous explaination I had come to the same exact conclusion that the difference between the two impedances if you have a 0.0 impedcance return path is the different mutual coupling between the conductors due to Z1 currents being 120 degrees...

magoo2: "For zero sequence, you apply a single-phase source to all the conductors at one end, add the 3 CTs and jumper the other ends together with a low impedance connection back to the source and measure V/I again." Still trying to understand: Are the "conductors" the actaul cable...

magoo2: When you say "add" the three CTs in the zero Sequence tests do you mean parallel the CT outputs or series them? I see that the external circuit of the cable should not be included in the cable Z0 for just the cable only Z0. It looks like the total circuit zero sequence impedance...

I see your point but then how would the positive and zero sequence impedance differ for a ground fault that has no impednace in the ground return path?

What is the zero seq. impedance of a cable that has a ground fault to a a zero impedance grd plane? In other words, if a cable is in a plant with a very good ground mat so that a ground fault has a zero impedance return path what is the value of a the cable zero sequence impedance? Is it...

thread238-248906 What are test times for shielded and nonshielded cable using AC at 60HZ? What are 60HZ AC test voltages for 5KV and 15KV cable?

Gianoli, Thanks for your commments . You are right I should have said air magnetic breaker because I am talking about switchgear. Do you or anyone else know of a device that will cut down on the voltage wave slope but that is not a capacitor. An arrestor just cuts down on the magnitued of...

Thanks for your input.

Thank you for taking the time ot give me some comments . This is valuable. What do you think about using surge arrestors or limiters at the motor as opposed to capacitors?

Comparing the voltage spikes produced with interruption of a medimum voltage vacuum bottle with those produce by an air blast breaker. Are they the same in new vacuum gear? What about in older vacuum gear? I know that the early ventage vacuum gear had surge capacitors but I have gotten...