×
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

High Impedance Bus Differential Relay (KAB)

High Impedance Bus Differential Relay (KAB)

High Impedance Bus Differential Relay (KAB)

(OP)
I've come across an odd situation in a switchyard outside of a power plant.  An electro-mechanical high impedance differential relay (KAB) is used as bus differential protection.  As is practice, a lockout contact is used to short-circuit the varistor in order to prevent it from overheating.

I would understand completely, if the KAB tripped this lockout, but the unit differential (a separate device) actually trips the lockout that shorts across the varistor of the KAB.  I just can't think of a reason this would be done.

I assume this was done in error long ago, but I would like some confirmation.

RE: High Impedance Bus Differential Relay (KAB)

Normally, the KAB would trip a lockout that would both trip all bus breakers and short out the varistors.  If the generator differential shorted out the varistors, then the bus protection would be disabled when the generator differential operated.  Also, the varistors would not be shorted out if only the bus differential operated.  This can't be right.

RE: High Impedance Bus Differential Relay (KAB)

(OP)
Thanks jghrist, I just wanted to be sure I wasn't missing something.  I am positive this is just one of those things that has been wrong for years.

It looks like it might have come about from a lack of contacts on the bus differential lockout, but there is no way the unit differential lockout is serving the intended purpose.

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