×
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

Plotting undervoltage and overcurrent relays on same amps base

Plotting undervoltage and overcurrent relays on same amps base

Plotting undervoltage and overcurrent relays on same amps base

(OP)
Greetings:

Wondering if anyone can share more examples or experiences with coordinating undervoltage and overcurrent relays. The paper

"Allowing for decrement and fault voltage in industrial relaying", Arnold Kelly
Industry and General Applications, IEEE Transactions on
Date of Publication: March 1965
Volume: IGA-1 , Issue: 2
Page(s): 130 - 139

has a nice example (picture attached) but I'd be interested in your opinions. Thanks for your thoughts.

RE: Plotting undervoltage and overcurrent relays on same amps base

Are you trying to independently coordinate 2 separate relays (27 & 51 - for motors (?)) or are you looking into generator protection such as 51/27R?

If the later, Basler has some application notes available on their website Basler 51/27R. You will have to register to download. There also appears to be a mathcad file available for download.

The intro of the paper is:

"VOLTAGE RESTRAINED TIME OVERCURRENT RELAY
PRINCIPLES, COORDINATION, AND
DYNAMIC TESTING CONSIDERATIONS
INTRODUCTION
The coordination of voltage restrained time overcurrent relays is usually based on static
characteristics in which the time-current plots assume constant current. This assumption
greatly simplifies the coordination process but fails to account for the slow-down effect due
to the decrement in generator fault currents. This paper addresses the dynamic response
of 51/27R relays in which the overcurrent element conforms to the dynamic characteristic
defined in the ANSI C37.112 standard. The purpose of this analysis is to compare the
results obtained from a proposed approximation to the exact timing results derived from a
relay model and actual test."

The reference section may also be useful.

[1] Baker, Davis S., Generator Backup Protection, IEEE Transactions on Industry
Applications, Nov/Dec 1982.
[2] Ventruella, Del, and Pete Stectuk. A Second Look at Generator 51V Relays, IEEE
Transactions.

RE: Plotting undervoltage and overcurrent relays on same amps base

(OP)
smallgreek: thanks for your response. I am coordinating incoming feeder phase overcurrent relays with 4.16kV bus undervoltage (loss of voltage) relaying.

RE: Plotting undervoltage and overcurrent relays on same amps base

Are you using the undervoltage as a backup to the overcurrent relays, or just to open the circuit breaker in the event of loss-of-supply?

If the latter, I generally choose a maximum clearing time for any fault (often around 5 seconds), and set the undervoltage relay delay to something longer than this. I'm not typically concerned with momentary loss-of-supply, perhaps you are which is why you need better coordination?

RE: Plotting undervoltage and overcurrent relays on same amps base

(OP)
Thanks mgtrp. The undervoltage relays are only supposed to transfer the source when there is truly a loss of voltage situation, not when there is a dip from a phase fault. So I'm in the process of coordinating these devices...

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