Why Oil immersed transformer use oil pillows
When the oil-immersed transformer is in operation, the temperature of the oil will increase due to the heating of the iron core and the windings. The volume expansion of the oil will cause the mailbox to receive a lot of pressure. If you do not set the oil pillow, the oil will not be able to fill the mailbox, so you must leave enough space to attack expansion. As the cross-sectional area of the mailbox is large, when the transformer load decreases, the oil temperature drops, the volume Shrinking, the oil surface will accelerate the moisture absorption and oxidation of the oil. After the oil pillow is installed, an expansion chamber is provided for the transformer, which reduces the contact area between oil and air, greatly relieves the speed of oil absorption and oxidation, and prevents the explosion of the box due to the expansion of the oil due to the high pressure.
In addition, after the oil pillow is set, the height of the oil surface can exceed the height of the tank cover and the casing, so that the insulating casing is also filled with transformer oil to increase the insulation strength of the outlet wire. The oil pillow is connected to the tank via a connecting pipe via a gas relay and a butterfly valve. An oil level meter for monitoring the oil level is arranged on the oil pillow, a grease hole is arranged on the upper end of the oil pillow, a tube connected to the atmosphere is installed in the oil pillow, and the lower end of the oil tube is provided with a respirator. The height of this pipe should be higher than the oil level when the oil temperature of the transformer is highest, to prevent oil spillage.
In addition, after the oil pillow is set, the height of the oil surface can exceed the height of the tank cover and the casing, so that the insulating casing is also filled with transformer oil to increase the insulation strength of the outlet wire. The oil pillow is connected to the tank via a connecting pipe via a gas relay and a butterfly valve. An oil level meter for monitoring the oil level is arranged on the oil pillow, a grease hole is arranged on the upper end of the oil pillow, a tube connected to the atmosphere is installed in the oil pillow, and the lower end of the oil tube is provided with a respirator. The height of this pipe should be higher than the oil level when the oil temperature of the transformer is highest, to prevent oil spillage.