The invention relates to the technical field of transformers, in particular to an oil-immersed power
transformer which comprises a hollow rod, a first round rod, a first
piston, a first spring, a cylinder, a second round rod, a second
piston, a limiting block and a ventilation
assembly. A hollow rod is fixedly connected to the diaphragm; a first round rod is slidably connected to the hollow rod. A first
piston is fixedly connected to the first round rod and makes contact with the lower end of the hollow rod. A cylinder is fixedly connected to the box body; through cooperation of the hollow rod, the first round rod, the first piston, the first spring, the cylinder, the second round rod, the second piston, the second spring and the limiting block, pressure relief operation can be automatically completed when pressure in the
transformer body is increased abnormally, and therefore the
transformer body can be protected; and the
transformer oil sprayed out at a high speed can be intercepted and prevented from being sprayed to the outside to pollute the environment, the intercepted
transformer oil is gathered on the upper side of the diaphragm, manual collection of the
transformer oil can be facilitated, and waste is avoided.