×
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

Modeling SC Current on Substation Transformer Secondary

Modeling SC Current on Substation Transformer Secondary

Modeling SC Current on Substation Transformer Secondary

(OP)
We know the Utility Available Fault Current on the 115 kV Substation Side (@100 MVA base), also, source impedances are known as well as the Substation Transformer Z% (%8).

How do I Calculate the Fault Current on 13.2kV Secondary Side of the Substation Transformer (115/13.2, 21 MVA, %Z=8)

Thanks in advance for your help and time

RE: Modeling SC Current on Substation Transformer Secondary

This is no place for home work !!!!

Read up the text books or IEEE "Buff" or "Red" Book.

RE: Modeling SC Current on Substation Transformer Secondary

hint: try Ohm's Law

Bung
Life is non-linear...

RE: Modeling SC Current on Substation Transformer Secondary

Comment: Everyone is innocent unless proven guilty.
1. Convert the transformer Z to 100MVA and 115V bases.
Z115kV,pu=Z13.2kV,pu x (100MVA/21MVA) x (13.2kV/115kV)^2
2. Calculate the short circuit current on the transformer primary side Ip,pu:
Ip,pu=1.0pu/(Zsys,pu+Z115kV,pu)
3. Transfer the short circuit current Ip,pu to the secondary side
Is,pu=Ip,pu x 115kV/13.2kV
4. Express the Ip,pu in Ip,amps
Is,amps=Is,pu x Is,base
where
Is,base=21000kVA/(sqrt3 x 13.2kV)=919A

RE: Modeling SC Current on Substation Transformer Secondary

jB,

Not on my monitor screen, they aren't!! Guilty until proven innocent - and this question just can't be from a practising engineer working on substation design because it is such a basic question.

Buy a book and study it like we had to!

-----------------------------------

Start each new day with a smile.

Get it over with.

RE: Modeling SC Current on Substation Transformer Secondary

(OP)
Thanks Jbartos for your feedback and decency. For all the critics, what prompted me to post my thread was to confirm the model I followed, I compared my calc.s with the outcome of trans/dist. analysis software that we use here, the discrepenies were significant, I found the reason was the software uses 'Main' system voltage 'Below' the source as the 'Base' and not the source voltage itself!! I checked with them today and that was their answer!!

There was no need for the harsh words!! anyway, thanks all.

RE: Modeling SC Current on Substation Transformer Secondary

lol...guys, all it takes is clicking on the person's username to see what else they have posted...tmaly1 is obviously for real...check out the other posts.  Don't be goofy!

RE: Modeling SC Current on Substation Transformer Secondary

Sorry mate - I'm usually happy to pitch in and help anyone where I can but from a safety angle I have to say I'm with Scotty on this one as there are many many aspects to consider.

Get professional help (engineering that is).

_______________________________________
Colin J Flatters BSc(Hons) IEng MIEE MIIE
Electrical Engineer / Project Manager
Email - cflatters@colin7.demon.co.uk.

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