Sequences

[ggunn]

I am reading a paper about short circuit current calculations; the author speaks of positive, negative, and zero sequences but doesn't define them. I have heard the terms before but I never truly understood them; can someone enlighten me as to what they mean? I would appreciate it. I can see that they have something to do with AC impedances.

Mods: please remove the duplicate from the General Electrical forum.

 

[LarryFine]

Just the first one I found:

What is Symmetrical components Positive, Negative, Zero Sequence | Electrical4u

Symmetrical components are nothing but a mathematical modeling which is used to analysis the unbalanced three phase power system both Normal and abnormal

www.electrical4u.net

 

[jim dungar]

Larry is correct, sequences are part of symmetrical components. Kind of hard core engineering.

These are very helpful when analyzing unbalanced 3-phase circuits. We can use the negative sequence to look at if a utility fuse has blown causing our transformer to develope a phantom voltage thus fooling phase loss relays. Zero sequence currents are used with GF systems and 'artificial neutral and grounding' transformers.

 

[Hv&Lv]

From the masters..

https://selinc.com/api/download/100688#:~:text=The%20method%20of%20symmetrical%20components,%2C%20and%20zero%2Dsequence%20components.

Even if you don’t actually do any calculations it's a real easy way to make sure a relay is set correctly with respect to rotation and/or displacement

 

[electrofelon]

Oh darn, I thought you were talking about math sequences, and if that was the case I would have directed you to this, The On-Line Encyclopedia of Integer Sequences® !

Welcome - OeisWiki

oeis.org

 

[LarryFine]

And then there's this kind: