×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

generator - thevenin impedance

generator - thevenin impedance

generator - thevenin impedance

(OP)
I'm using some software to perform a fault study on a distribution system.  When I input a substation (ie. generator) I have to specify the 3 phase fault current and and the short circuit ratio (X/R).  From this, the program determines the positive and negative thevenin impedances....the zero sequence is left blank.  

My question is how do I determine the correct zero sequence impedance ? If the configuratin is "star" is the zero component 0+jX (where jX is the same as the positive and negative sequence components)?  When I do this, my calculated values and the ones the computer spits out are quite different.  

Any help would be much appreciated

Thanks

RE: generator - thevenin impedance

Generator zero and negative sequence impedance is not same as positive. You will have to look up in the generator data.

P.S. do not forget to consider the grounding resistance/impedance if any. Many programs would take this value as a separate input.

RE: generator - thevenin impedance

I suspect the program you are using may have a default assumption that somewhere in the real system between your real generators and this substation where the generation is being modelled there will be a break in the zero sequence path and is therefore not including any zero sequence impedance path in the machine equivalent to represent this (an impedance of zero is often treated (not very logically) as an indicator of no zero sequence path).
Which program are you using ?
Your zero sequence path at distribution levels will usually be dominated by transformer earth paths (either Neutral earth impedances or earthing transformers) close to the busbar.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources