Bucholtz Trip
Bucholtz Trip
(OP)
Hello Everybody
We have a 30MVA, 132/33KV transformer that is tripping on bucholtz. We carried out Insulation resistance, magnitisation and short circuit tests which all shows a satisfactory result. The magnitisation and short circuit tests were carried out using 415V and the Insulation resistance test using 5KV Megger. We dont have the facility for anlysing the gas being evolved but the gas coming out is colourless. What could be the problem with this transformer?
We have a 30MVA, 132/33KV transformer that is tripping on bucholtz. We carried out Insulation resistance, magnitisation and short circuit tests which all shows a satisfactory result. The magnitisation and short circuit tests were carried out using 415V and the Insulation resistance test using 5KV Megger. We dont have the facility for anlysing the gas being evolved but the gas coming out is colourless. What could be the problem with this transformer?






RE: Bucholtz Trip
RE: Bucholtz Trip
RE: Bucholtz Trip
Collect the gas if possible and get it analysed. Definitely get an oil sample and send it for DGA at a reputable oil lab. If your transformer is gassing then you have a fault within the tank. The DGA results should give some idea what type of fault you are looking at, although trending the DGA results would be even better. As your transformer appears to be sick, sample at least monthly and trend the results. If the results show a deteriorating condition then plan to take it out of service for an internal inspection and repair before it takes itself out of service on a more permanent basis.
You should find a link under an external cover which allows you to separate the core from the tank earth. Megger the insulation at the manufacturer's recommended voltage - 500V should be enough. The core should not be earthed to the tank with the link removed.
A 30MVA transformer is probably just large enough to enter without detanking the core if you remove the oil, otherwise it will likely be a detanking job. Either way hire in some expertise to assist you with the inspection.
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If we learn from our mistakes I'm getting a great education!
RE: Bucholtz Trip
Does the tapchanger have a separate buchholz?
Is there a history of Buchholz gas alarms? Is the gassing load related?
Regards
Marmite
RE: Bucholtz Trip
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If we learn from our mistakes I'm getting a great education!
RE: Bucholtz Trip
I agree with Marmite and Scotty that you are playing with fire because you're Bucholz, after replacing, again tripping transformer. In the past, I made simple test with lighter. If gas from rele burning it is sign of carbonmonoxid or severe problem with transformer and you have to overhaul the transformer.
Good luck!
RE: Bucholtz Trip
RE: Bucholtz Trip
Isquaredr we are sure of the oil level.
However I obsered that, when meggering the HV side the insulation resistance will drop at a certain stage and then rise again.
RE: Bucholtz Trip
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If we learn from our mistakes I'm getting a great education!
RE: Bucholtz Trip
Measure the winding reistances (micro-ohmmeter) of HV winding (on all taps) and the LV winding to detect loose connections.
I wouldn't take any Buchholz trip lightly. I have seen enough disastrous transformer failures to be afraid of the silent beast.
RE: Bucholtz Trip
RE: Bucholtz Trip
Buchholtz relay operated---isn't joke.
But.. as Marmite wrote, are you have some history of Buchholtz alarm? Are trips was together with Buchholtz alarms?
Are you see Buchholtz trip on the relay and de-latch it, or see only on the some panel indication?
RE: Bucholtz Trip
Good luck
RE: Bucholtz Trip
I think the insulation resistance drop might indicate some kind of incipient damage. While you are testing insulation resistance, the HV isolation of the xformer acts like a big condenser charging, so, the more time you apply Vcd, the higher insulation resistance will become.
It seems you have a hot spot inside the xformer, so ask for technical assistance in order to check resistance of the windings, transformer ratio, power factor, partial discharge test and DGA to confirm the diagnosis.
Regards.