Water Intake Judgment and Prevention of Transformer

After the distribution transformer has been operating for a period of time, the transformer oil pressure drop will occur, and even a small amount of water will be released from the oil pillow of some transformers. In severe cases, after the water enters the transformer tank, the insulation resistance of the winding will decrease. When the insulation resistance falls below the line voltage, the insulation will breakdown and the transformer burns.

First, the way water enters the transformer According to the situation of dismantling the transformer, the water is usually transferred to the transformer under the action of breathing and capillary action. In addition, because the transformer seal is not strict, the gasket and the fastener are not sealed, and moisture can also leak into the transformer when it rains. However, this situation is rare.

The temperature of the transformer in operation will change due to load and weather influences. When the transformer temperature rises or falls, the oil level in the oil pillow rises or falls. In order to promptly remove more air from the oil surface when the oil surface rises, and to supplement the air in time when the oil level drops, the distribution transformer leaves a breathing tube at the upper part of the oil pillow. The breathing tube of the old-fashioned transformer is directly connected to the atmosphere. The new transformer is equipped with a dry handler between the breathing tube and the atmosphere, in which the absorbent silicone is placed. When the silicone fails, it will lose its proper moisture absorption. When the ambient temperature drops, the water will form a ring of water around the breathing tube and enter the transformer oil pillow along the breathing tube through capillary action. Accumulated for many years, the water inside the pillow will enter the transformer.

On sunny days, transformers can also be affected by the temperature difference between day and night. During the day, part of the air inside the transformer's oil pillows expands due to heat and is expelled from the body. At night, air enters the oil pillow due to cold shrinkage. Air will have some of the water dissolved in the oil. Once the dissolved water in the transformer oil is saturated, when the temperature drops, the solubility of the oil to water decreases, and part of the dissolved water is precipitated; although the solubility increases when the gas m rises. Part of the water that has settled at the bottom of the oil pillow is to be dissolved in the transformer oil, but the rate of precipitation is greater than the rate of resolubilization. Therefore, this is the reason why some small amounts of moisture are released from the underside of an unused power distribution transformer's oil pillow.

Second, the determination of the transformer due to water burn out due to water and make the transformer burn out judgment is relatively easy. The precipitation of water in the oil pillow enters the transformer. The first is the moisture of the C phase high voltage coil. This is because the C phase high voltage coil is close to the lower lip of the oil pillow and the connecting pipe. When the C phase high voltage coil is damped and the dielectric strength cannot withstand the line voltage or line overvoltage, the phase coil is first burned out. Therefore, most transformers that are damaged due to the influx of water are the C-phase high-voltage coils.

Third, prevent water from entering the transformer How to prevent water from entering the transformer? There are the following four measures:

(1) Strengthen the inspection of transformers, especially in the season, check the rubber gaskets and gaskets of transformers frequently. Tighten loose parts in time.

(2)Distribution transformers equipped with respirator should be filled with discolored silica gel for observation in the respirator.The color of the commercially available discolored silica gel is blue when water is anhydrous, and is pink after absorbing water. Remove the silicone and bake it before use.

(3) Some old-fashioned transformers do not have respirator installed. They should try their best to modify the respirator. Old-fashioned transformers that cannot be modified at one time should be based on the size of the transformer. After inflating, put on the upper cover of the oil pillow (to loosen the lid 3-4 laps), use a wire to tie the interface, and then use a plastic bag with no leakage under the bottom, put the mouth down on the transformer oil pillow, and tie it with a rope. Good plastic pocket under the mouth. In this way, on the one hand, it is possible to protect the inflatable balloon while preventing water from entering the transformer.

(4) There is a height difference of about 3cm between the upper mouth of the connecting pipe of the transformer oil pillow and the tank and the bottom of the oil pillow, and the water is precipitated in the bottom of the oil pillow after entering the oil pillow.

Can be used glycerin, vegetable oil, phenolphthalein, calcium oxide and other preparation of water indicator cream. In this way, it is possible to check whether there is water and the depth of the water layer in the oil pillow without removing the oil end cover.