×
Follow Us
Results 1 to 5 of 5

GE SR745 Protective Relay

 Jump to latest post
    #1
  1. ElectricalTestTech's Avatar
    ElectricalTestTech is offline NETA Level IV
    Affiliate Member
    Pro Subscriber
    Join Date
    Sep 2017
    Location
    Washington, DC
    Posts
    69
    Reputation

    GE SR745 Protective Relay

    I was wondering if anyone had any type of spreadsheet or formula on how to calculate the currents needed to operate different parts of a differential slope. I am looking to be able to type in a primary winding current, and have it calculate the amount of secondary current needed to trip on differential. I have contacted GE and they do not have anything and basically state that we should just trust the relay. I have had so many relays fail in the past year that I do not trust their relays.

    .2*CT diff p/u
    25% slope1
    1*CT break
    98% slope 2

    16MVA, 1200:5 primary, 3000:5 secondary, 13.8kV-4.16kV, Dyn1

    I have a spreadsheet that allows me to input Winding 1 test amps and Winding 2 test amps. Based off of those it will tell me if I will see a trip or no trip. But I want to know the specific calculated pick up instead of having to continuously change my current values in the spreadsheet to get an approximate pick up.

    Thanks

  2. #2
  3. Relay1's Avatar
    Relay1 is offline
    I use to be disgusted, now I'm just amused!
    Junior Member
    Join Date
    Nov 2017
    Location
    Central Texas
    Posts
    17
    Reputation

    Diff Spreadsheets

    Quote Originally Posted by ElectricalTestTech View Post
    I was wondering if anyone had any type of spreadsheet or formula on how to calculate the currents needed to operate different parts of a differential slope. I am looking to be able to type in a primary winding current, and have it calculate the amount of secondary current needed to trip on differential. I have contacted GE and they do not have anything and basically state that we should just trust the relay. I have had so many relays fail in the past year that I do not trust their relays.

    .2*CT diff p/u
    25% slope1
    1*CT break
    98% slope 2

    16MVA, 1200:5 primary, 3000:5 secondary, 13.8kV-4.16kV, Dyn1

    I have a spreadsheet that allows me to input Winding 1 test amps and Winding 2 test amps. Based off of those it will tell me if I will see a trip or no trip. But I want to know the specific calculated pick up instead of having to continuously change my current values in the spreadsheet to get an approximate pick up.

    Thanks
    I sent a couple of spreadsheets to your e-mail address. Hope they help!

  4. #3
  5. ElectricalTestTech's Avatar
    ElectricalTestTech is offline NETA Level IV
    Affiliate Member
    Pro Subscriber
    Join Date
    Sep 2017
    Location
    Washington, DC
    Posts
    69
    Reputation
    Quote Originally Posted by Relay1 View Post
    I sent a couple of spreadsheets to your e-mail address. Hope they help!
    Thank you. I will check them out tomorrow. I am trying to figure out this algorithm. It makes me mad that GE can’t provide a tool that other manufacturers do. I’ll be back at it tomorrow morning

    Thanks again

  6. #4
  7. Join Date
    Mar 2015
    Posts
    1
    Reputation
    Quote Originally Posted by Relay1 View Post
    I sent a couple of spreadsheets to your e-mail address. Hope they help!
    Would you mind sharing them with me as well. I've ran into this same issue.

  8. #5
  9. Relay1's Avatar
    Relay1 is offline
    I use to be disgusted, now I'm just amused!
    Junior Member
    Join Date
    Nov 2017
    Location
    Central Texas
    Posts
    17
    Reputation

    387 Spread Sheet

    Quote Originally Posted by Reef Donkey View Post
    Would you mind sharing them with me as well. I've ran into this same issue.
    Hello Reef Donkey,

    Hopefully there is a SEL-387 spread sheet attached here that may help you.

    Relay1
    Attached Files Attached Files

Subscribe

Share this thread

Related Topics

  1. CL protective device cycles?
    By Havik21 in forum NETA Level 4 Exam
    Replies: 4
    Last Post: November 2, 2018, 12:36 PM
  2. Silent sentinel protective relay book by Westinghouse
    By Larry5443 in forum Technical Documents
    Replies: 2
    Last Post: December 21, 2015, 12:13 PM
Follow us


Explore TestGuy


NETA Certification Training


NICET Electrical Power Testing


Help and Support




You are viewing the archives. Enjoy new features and join the conversation at wiki.testguy.net