The utility model discloses a
transformer vacuum-pumping device which comprises an air-pumping main
pipe, a first-stage pump, a second-stage pump, a third-stage pump, an oil-gas separator and a vacuum gauge are sequentially connected in series from the upstream end to the downstream end of the air-pumping main
pipe, and a first bypass
pipe connected with the second-stage pump in parallel and a second bypass pipe connected with the third-stage pump in parallel are further arranged on the air-pumping main pipe. The first bypass pipe is provided with a first
electromagnetic valve, the second bypass pipe is provided with a second
electromagnetic valve, the first-stage pump is a
rotary vane pump or a
screw pump, the second-stage pump is a roots pump, and the third-stage pump is a molecular pump. Firstly, a first-stage pump is started to pump the interior of a
transformer oil tank to a first set
vacuum pressure value, then a second-stage pump is started to pump to a second set
vacuum pressure value, and finally a third-stage pump is started to pump to a set target
vacuum pressure value, so that water and dissolved gas remaining in an insulating plate and
transformer oil are pumped out; the extracted gas enters the pump set after oil is separated through the oil-gas separator,
pollution to the main gas extraction pipe and the pump set is effectively avoided or relieved, and the service life of the vacuumizing equipment is prolonged.