Dear all, i want to top-up the low level of transformer oil without isolating the transformer. Plz suggest the methods....

Ashish,

You didn't say what the voltage is but typically that is a job for a trained crew who has done this sort of thing before. There are two issues involved here, personnel safety and equipment integrity/safety.

There's always a chance that someone or something makes inadvertent contact with something that's energized. You didn't say how the equipment is protected but if you bottom fill and your flow rate is too high you might triger the SPR or Bucholz, and there's always the chance that you stir up sediment from the bottom or that your new oil is contaminated.

A professional organization knows how to take the necessary precautions. This is not a do it yourself project but a case of "if you have to ask how to do it then you are not qualified to do it."

Alan

Hi Ashish,
for indoor, distribution transformers generally the HV and LV terminals are closed, and there is no any personal safety issue, however to fill the transformer oil in transformer you must use the transformer oil filtration machine, which filters the oil, raises its temperature, near to transformer temperature, remove sediments etc. this is the correct practice generally followed

First of all, as per the statutory requirements you are not suppose to carryout any maintenance work on Transformer without shutting it down. As far as filtration of oil is concerned, it involves applying high vacuum, so if there is any weak joint, oil will start leaking and you will have no control over it. Sometimes during vacuum filtration of oil the buchhloz relay may operate and trip the circuit breaker, there by isolating the transformer and then your very purpose of carrying out job online will be defeated. From safety and statutory point of view, it is not at all advisable to carry out filtration when the transformer is energised. Still if you want to take risk then go ahead.

This question is not specific on some issues.
1. If you want to top up oil in the conservator of a transformer on load, some transformers have a down pipe from the top of the conservator which you connect to and fill up. There is no chance of tripping the transformer.
2. If however you want to filter the oil in the transformer on load that should be left to trained people but what is normally done is to reduce the load on the transformer to less than 50% and disable the buccholtz relay.

well, depending on voltage and safety, the best way to do this is pull a vacuum at the top and suck the oil in at the bottom..

I have done this on an energized 1500kVA 13.2kv - 480v/277. I will tell you that it is a bit scary. If sludge is dislodged during the process, it might get very exciting. You must disable the sudden pressure relay also.

Once filled to desired level, terminate the oil flow and disconnect. Then break the vacuum with nitrogen to a positive pressure of 1 psi..

Well, We filtered oil on line on a generator transformer using portable moisture removing machine. however, we took a small outage and rigged the equipment drawing moisture laden oil from bottom and out put from filter into the conservator.
Once the pipeline established the transformer was charged and oil circulated through the transformer. I believe the transformer is 40MVA single phase 13.8kv/ 220kV

I guess to top up oil transformer don't need to be isolated.you can safely do it online.