×
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

Short Circuit Value

Short Circuit Value

Short Circuit Value

(OP)
I have carried out ANSI 30cycle Short Circuit Study in SKM but the Values of ANSI_30cycle_3P & SLG is 20A & 12A respectively at 13.8kV. The utility is rated as 500MVA.

What might be the problem.Why the Value is so small? I cannot do the settings for the relays unless I rectify this.

RE: Short Circuit Value

More information is required.  One-Line Diagram ?
Is the Utility 3 phase short-circuit contribtuion of 500 MVA at 13.8kV ?     3P SC = 500 MVA / ( sqrt(3*13800 ) = 20.92kA

RE: Short Circuit Value

Look more closely at the units of all data that you put in as well as output.

Rafiq Bulsara
http://www.srengineersct.com

RE: Short Circuit Value

(OP)
In the attach link you can see that the value of I30cycSLG is 2231.75A. The FLA of Chiller#1 is 873.6A at 380V with starting inrush of 5.88 x FLA.

Now the starting inrush for Chiller#1 is much higher then the minimum fault current (I30cycSLG i.e. 2231.75), so I want to now at how many times of FLA of Chiller, the Instantaneous Protection shall be set at???  

RE: Short Circuit Value

In the attachment the 3 phase fault is 60kA and only SLG is 2.2kA.

What does chiller starting kA has to do with SLG fault current? Motor starting will not be seen by the ground fault element.

As for actual settings, it depends on your objectives. Low as possible but high enough to coordinate and avoid nuisance trips.



 

Rafiq Bulsara
http://www.srengineersct.com

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