×
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

IEEE Over Current Relaying Standard

IEEE Over Current Relaying Standard

IEEE Over Current Relaying Standard

(OP)
Can anyone tell me which IEEE Standard gives guidelines on overcurrent relaying?  I'm thinking it is C37.90-1989 (R1994), but I'm not sure.  

I'm looking for the standard minimum coordination time buffer between time/current curves.  I"m thinking it is 0.3 seconds, but I'm not sure.

RE: IEEE Over Current Relaying Standard

IEEE Std. 242 (Buff Book) gives a suggested grading margin of .3 seconds (Sect. 14.2.2) but suggests tight systems could are sometimes decreased to .25 or increased upto .4 seconds for mechanical relaying systems.

RE: IEEE Over Current Relaying Standard


Gordon has nailed it.  IEEE Std 141-1993 ยง5.7 is another reference.  

[C37.90 seems to deal more with surge-withstand capability in relays.]  
  

RE: IEEE Over Current Relaying Standard

Suggestion: Reference:
1. IEEE Std 242-2001 Buff Book
states in Chapter 15 on page 602:
When coordinating overcurrent relays with one another or with any other device, considering the location of the relays with respect to other devices is necessary. The CTI desired between the characteristic curves is usually 0.3 s to 0.4 s when coordinating induction disk overcurrent relays in series with one another. This interval is measured between the relay characteristic curves at the lesser value of either the instantaneous pickup setting of the downstream device or the maximum fault-current level that can be experienced simultaneously by both relays (see Figure 15-12).

RE: IEEE Over Current Relaying Standard

Clarification: CTI is Coordination Time Interval

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