Sequence Network / Fault Current Calculation

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jcbeck

Member
Location
UK
Hi Guys

Need some assistance to improve my knowledge and skills in understanding fault calculations. Go easy on me - I'm a mech eng who after 30 years since graduating has just started to study for an M.Sc. in Power Distribution Eng! I can't get my head around to calculate the equivalent parallel reactances in this diagram. I have inserted comments on the numbers I can't reconcile - trying again with diagram.
All assistance very gratefully received!

Worked Example 5.1.jpg

John
 

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mivey

Senior Member
Hi Guys

Need some assistance to improve my knowledge and skills in understanding fault calculations. Go easy on me - I'm a mech eng who after 30 years since graduating has just started to study for an M.Sc. in Power Distribution Eng! I can't get my head around to calculate the equivalent parallel reactances in this diagram. I have inserted comments on the numbers I can't reconcile - trying again with diagram.
All assistance very gratefully received!

John
Sorry but I can't read your drawing. Need better resolution.
 

jcbeck

Member
Location
UK
Link to attachment

Link to attachment

You can find the attachment here: <a href=http://www.filedropper.com/workedexample51><img src=http://www.filedropper.com/download_button.png width=127 height=145 border=0/></a><br /><div style=font-size:9px;font-family:Arial, Helvetica, sans-serif;width:127px;font-color:#44a854;> <a href=http://www.filedropper.com >online backup storage</a></div>
 

Julius Right

Senior Member
Occupation
Electrical Engineer Power Station Physical Design Retired
I think smart% is right.
If we?ll take the three-point configuration only and we?ll transform the Delta into Star we?ll get:
X1=X12*X31/(X12+X23+X31)
X1=0.6*0.25/(0.6+0.53+0.25)=0.1087
X2=X23*X12/(X12+X23+X31)
X2=0.53*0.6/(0.6+0.53+0.25)=0.2304
X3=X31*X23/(X12+X23+X31)
Z3=0.25*0.53/(0.6+0.53+0.25)=0.096
There are differences due calculation error [I guess].
 

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kingpb

Senior Member
Location
SE USA as far as you can go
Occupation
Engineer, Registered
I very good document that may help you understand the basics of this is to find a copy of the "MVA Method" by Moon H. Yuen

if you have difficulty locating it, PM me.
 

jcbeck

Member
Location
UK
Thanks and new circuit attached

Thanks and new circuit attached

Thanks to all for assistance - I also came to the conclusion that the j0.12 should have read j0.11! Working on a loop power network problem and having difficulty knowing how to incorporate the impedances on the loop with the load. I've a delta / wye transformation but cannot get the numbers to work out to the correct answer. Any assistance much appreciated - thanks!
 

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