Modeling SC Current on Substation Transformer Secondary 1

[tmaly1]

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

 

[rbulsara]

This is no place for home work !!!!

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

 

[Bung]

hint: try Ohm's Law


Bung
Life is non-linear...

 

[jbartos]

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

 

[ScottyUK]

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.

 

[tmaly1]

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.

 

[musicguy1800]

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!

 

[CJFlatters]

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.