×
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

Switchgear Issues

Switchgear Issues

Switchgear Issues

(OP)
Hello, I just received an email from a customer having issues with a piece of mining switchgear. This unit has a 2750 KVA XFMR with a delta 13.8 KV primary, a delta 2.3 KV secondary @ 2000 KVA, and a wye 480 V secondary @ 750 KVA. The secondaries both feed busses. The 2.3 KV bus supplies power to a continuous miner. The 480 V bus supplies power to various smaller loads. The 480 V feeder bus is protected by a main breaker and each branch has its own breaker. The customer claims that the miner was running along with various unknown 480 V loads when the 480 V main breaker tripped (the 15KV main breaker on the primary of the XFMR DID NOT TRIP). The customer then removed the lids from the unit and saw that there was "some smoke coming from the XFMR". They said that they used a 5KV megger on the secondaries and everything checked out ok. They removed the main breaker's cover and found no physical damage. I will be going to this customer's site in the near future to inspect the equipment. Other than an issue with the XFMR that caused a voltage drop that dipped below the breaker's UV coil threshold on a control XFMR, I can't think of any issue with the main XFMR that would cause the downstream 480 V main breaker to trip (I don't even know that this breaker has a UV coil... Just a possibility). Just off the top of my head, I would think that there is an issue between the 480V main and the 480V feeders to cause the trip but this doesn't explain the "XFMR smoke". It is very possible that there is more than one problem with this switchgear. Has anyone ran into any similar issues out in the field that may shed some light on these problems? Thanks in advance!

I am an engineer, so the glass is twice as big as it needs to be.

RE: Switchgear Issues

In my opinion, if the transformer does not present any sign of damage then the low-voltage cable could be damaged. A short-circuit on this cable could be the cause of breaker tripping. The heat produced smoke and may-in some cases- isolate the damaged insulation permitting further operation.

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