Forums » Electrical Engineering

Buchholz relay issue

    • 2 posts
    August 18, 2019 2:42 AM PDT

    A 12.5MVA transformer was installed 1 year ago but for the last 3 months I see regular buchholz tripping within 10 to 15 days. There is no air trapped in this buchholz relay, but after some days relay operates suddenly, after checking and releasing air, it comes to normal operation for some days and trips again.
    One reason I am thinking, can oil creating this problem, is it possible?
    what could it be?

    • 62 posts
    August 18, 2019 11:45 PM PDT

    Do a vaccum oil filtration

    • 33 posts
    August 19, 2019 9:28 AM PDT

    Disclaimer:  I've never worked on a transformers with a conservator, which are the only ones I have seen that have Buchholtz Relays.

    One of the lessons we got from Three Mile Island was, "Believe  your instrumentation."

    Setting that aside, I have some minor confusion:

    Bradley Easter said:

    A 12.5MVA transformer was installed 1 year ago but for the last 3 months I see regular buchholz tripping within 10 to 15 days. There is no air trapped in this buchholz relay, but after some days relay operates suddenly, after checking and releasing air, it comes to normal operation for some days and trips again.

    1.  When you say "trip", is that the upper float coming in, or the lower float?

    2.  The first part of your statement says there is no "air" in the BR.  The second part of your statement says you are releasing "air" and then the relay "comes to normal operation".  So which is it - Gas, or No Gas?

    Pull an oil sample, see if the analysis indicates to an internal arc.  (This would be following the part about believing your instrumentation)

    3.  My understanding is the BR can trip on oil flowing rapidly from the conservation tank to the main or from the main tank to the conservation tank.  About the only thing I can think of to cause that is step loading the transformer.  Is that happening?

    In any case, this is where I get the MFG documentation on the relay operation..  And yes, you want the documentation specific to the manufacturer - not generic descriptions.

     

    My inclination is to put Buchholtz relays into the same category as a Rapid Pressure Rise relay.  If these trip and it is not a false positive, you likely don't have a transformer to save, you have a fire to put out.

    carl