×
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

25kV Bus Fault clearing time

25kV Bus Fault clearing time

25kV Bus Fault clearing time

(OP)
Hi,

Just curious (if anyone knows) what are typical clearing times for a 25kV bus fault from the protections?

zone1 and zone2?

Does adding an NGR change this? (Assuming Zone 2 will come upstream form the TX prot)

Does the choice of having a high impedance vs low impedance relay affect these?

EDIT: Sorry forgot to add, im in Canada, AB., also mainly (but not only) interested in Phase to ground or phase to phase to ground or 3-phase to ground.

Thanks.

RE: 25kV Bus Fault clearing time

If you want fast fault clearing, (under 5 cycles) a dedicated bus differential scheme is the way to go. Low impedance vs high impedance does not matter much when set correctly in my experience.

RE: 25kV Bus Fault clearing time

For a bus dont worry about zone 1 and zone 2. Use differential as Mbrooke suggests. Bus blocking is gaining popularity at that voltage level, but personally i would stay with differential.

NGR won't have any impact.

Decent differential protection with a decent breaker will give you sub-5 cycle clearing time.

Whether or not to use a high-impedance differential set up depends if fault levels are high enough such that a close in (but out-of-zone) fault doesn't saturate the Bus CTs, which would cause an over-trip of the Bus.

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