×
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

Sensitive earth fault reset times

Sensitive earth fault reset times

Sensitive earth fault reset times

(OP)
We use sensitive earth fault protection set at around 8A pickup on our 400A (CT primary) 11kV feeders supplying overhead lines.  The idea is to detect and trip downed conductors.  The time setting is 10 second definite time.
The problem is that in the past the relays used have an instantaneous reset characteristic.  The advent of digital relays means that we know more about what faults rreally look like.  The recordings from an actual fault showed us that a downed conductor at the side of a road (about a metre of conductor lying on dry sand) resulted in a fair bit of arcing, the conductor jumped around a bit, but the fault current was being interrupted before the full 10 sec time-out was  reached.  The feeder was eventually tripped by remote SCADA ops from the control room.  The fault current was not enough for the standard e/f relay to pick up.

Has anybody any experience with using a slow reset function on SEF relays?  This will extend the total time to trip where on-again off-again arcing occurs, but is better than no trip at all.  What reset function was used (linear, fixed time etc?), problems encountered etc.

(BTW, conductors on sand make these really cool little glass tubes! (and no, don't try it at home, folks))

thanx

Bung

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