Common defects of oil transformers

Casing defect. This kind of defect is common in blow up, flash off and oil leakage. The reasons are:

① Poor sealing, moisture-inferior ratio of insulation, or oil leakage;

② Improperly equipped respirator or inhalation of water is not handled in time;

③ Capacitor bushings are generally used on the high voltage side of the transformer (110kV and above), and there are trachoma or cracks due to poor porcelain;

④ There are defects in the production of the capacitor core, and there is free discharge inside;

⑤The casing fouling is severe.

Core defect

① The insulation between the silicon steel sheets is damaged, causing the iron core part to overheat and melt;

② The insulation of the through bolts that clamp the iron core is damaged, causing a short circuit between the core silicon steel sheet and the through bolts;

③ The residual welding slag forms two points of the iron core to be grounded;

④The top and middle of the transformer tank, between the flange, barrel skin and the bushing of the upper part of the tank. The internal iron core, winding clamps, etc. heat due to partial magnetic leakage, causing insulation damage.

After the transformer has a defect in operation, if it is found to be a winding or iron core defect, the core should be suspended for inspection. First measure the DC resistance of each phase winding and compare it. If the difference is large, it is a winding defect. Then check the appearance of the iron core, and then measure the insulation resistance between the sheets by DC voltage and ammeter. If the damage is not serious, paint on the damaged area.