Common faults of current transformers

1. The thickness of the insulation part of the current transformer is relatively large, and some insulation layers also have wrinkles, and the insulation part is wrapped and loose. In addition, the vacuum treatment effect is not good, and the impregnation is incomplete and causes air-containing cavities. A fault that is easy to cause partial discharge.

2. The size and arrangement of the capacitive screen do not meet the design requirements. For example, the smoothness and flatness of the capacitor plate is poor, the capacitor screen is less placed, and the capacitor is broken or dislocated, so that the voltage equalization characteristics of the current transformer are destroyed. Therefore, when the electric field strength along the surface of the local solid insulation of the current transformer reaches a certain value, partial discharge will be caused.

3. Creeping discharge may occur on the surface of the current transformer due to unclean insulating material or high humidity content. This situation is more common in the case where the primary terminal lead discharges along the surface of the pad.

4. Spark discharge occurs due to the potential suspension and loose connection of the metal parts of the transformer in the store. For example, if the primary winding support nut is loose, it will cause the contact of the end screen lead, the potential suspension of the primary winding shielding aluminum foil, or poor welding, or even disconnection, which will cause the current transformer to fail.

5. The faults of increased contact resistance of the current transformer and local overheating are generally caused by the looseness of the ground nut of the end screen, the looseness of the tap fastening nut, and the looseness of the primary connecting nut, bolt, and splint. In addition, improper on-site maintenance and management should also be paid attention to. For example, the problem of water entering the transformer and getting damp may be related to the sealing structure and sealing material of the manufacturer, but it may also be a maintenance management problem.

Generally speaking, the on-site vacuum degassing is insufficient or the vacuum drying is not carried out during the maintenance, resulting in the situation that the dissolved gas in the oil is easily saturated, or the residual air bubbles in the oil-paper insulation and the high moisture content occur. These factors will leave a security risk to the device.