×
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

Phasing Test & equipment for MV Power system

Phasing Test & equipment for MV Power system

Phasing Test & equipment for MV Power system

(OP)
We have a 13.8KV MAIN1-TIE-MAIN2 Switchgear Fed from Utility's Two, 20MVA, 115KV/13.8KV Delta-Wye Grounded transformers both fed from single utility 115KV line. Upon fault on one of the transformer 13.8KV Bus to MAIN1 breaker we closed the tie breaker.

Question is when we replace the failed 13.8KV bus duct the plant does not want another outage. A colleague is insisting that we should first open the TIE before closing the MAIN1. He thinks that not knowing if the phasing verification was ever done on the two 13.8 KV buses this would be safest approach. I looked at Hubbell-Chance Phase tester see link. http://www.hubbellpowersystems.com/lineman/meters/digital-phasing-testers.asp

Which tests the phase sequence on both the Transformer (Line) and Bus (Load) side of MAIN1 breaker. I am not sure if this instrument will also identify A B and C buses on both sides of the breaker Can I also use this equipment to measure phase angles between phase As on Line and Load side of the breaker?

Thanks to all my learned colleague.

RE: Phasing Test & equipment for MV Power system

As part of the commissioning of the site you would expect the phasing to have been proven. Have the utility transformers never been taken out on a planned basis for maintenance by closing the tie and opening the transformer 13.8kV C/B without a complete site shutdown? That being said, if there are any doubts, by all means get hold of some phasing sticks and prove it again. If there was any chance of the connections being altered during the fault repair then this should be done anyway. If the circuit breaker is isolatable and the spouts are accessible then phasing sticks like those in your link would do the job. They work by comparing voltages rather than phase angle, but this is exactly the application they are used for.
Regards
Marmite

RE: Phasing Test & equipment for MV Power system

Your colleague is right and engage services of a testing company to perform "Hot Phasing" check across the open breaker(s).

You need to get both the phase rotation and the sequence right. Relying on instrumentation alone is dangerous.
 

Rafiq Bulsara
http://www.srengineersct.com

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