Basic fault of current transformer

- Oct 11, 2019-

1. The insulation part of the current transformer is thicker, some insulation layers are wrinkled, the insulation part is loosely wrapped, the vacuum treatment effect is poor, the impregnation is incomplete, and the air cavity is generated, which is easy to cause partial discharge failure.

2. The size and layout of the capacitive screen do not match the design requirements. For example, the capacitor plates are smooth and flat, the capacitive screen is small, the capacitors are damaged or misaligned, and the current transformer voltage equalization characteristics are broken. Therefore, when the electric field strength current transformer of the surface solid insulation reaches a certain value, partial discharge is caused.

3. Due to the unclean or high humidity of the insulation material, surface discharge may occur on the surface of the current transformer. This is often the case with primary terminal leads that discharge along the surface of the pad.

4. Due to the potential suspension of the metal parts of the transformer in the workshop, the connection is loose, resulting in spark discharge. For example, the looseness of the primary winding support nut will cause the latter structure to be the wire lead contact, and the primary winding shields the aluminum foil from potential suspension, or poor soldering, or even wire breakage, thereby causing the current transformer to fail.

5. Current transformer contact resistance increase and local overheat fault is usually caused by the looseness of the end shield ground nut, the looseness of the thread tightening nut and the looseness of the main connecting nut, bolt and splint. In addition, improper on-site maintenance management should be taken seriously. For example, the problem of moisture ingress into the transformer may be related to the manufacturer's sealing structure and sealing material, but it may also be a maintenance management issue.

In general, on-site vacuum degassing is insufficient or vacuum drying is not performed during maintenance, resulting in saturated gas in the oil or residual bubbles in the oil-paper insulation layer, and the water content is high. These factors can leave potential safety hazards to the device.