Typically, common faults in miniature current transformers are often associated with manufacturing defects that exist on their own.
For example, if the current transformer insulation is very thick, some insulation wrap around loose, insulation layer between wrinkles, coupled with poor vacuum treatment, impregnation is not complete and caused by air cavity, which is relatively easy to cause partial discharge failure. And if in the design, about the micro-current transformer capacitance screen size and arrangement does not meet the design requirements, or even less capacitive screen, capacitive plate is not smooth and flat, or even dislocation or fracture, which will cause the uniform pressure characteristics of the damage. Therefore, when the electric field strength of the local solid insulation along the surface reaches a certain value, it will cause partial discharge.
In view of this situation, it is necessary to deal with it in time to avoid the characteristics of arc discharge. In the process of manufacturing a miniature current transformer, if the insulating material used is contaminated, or if it is high in moisture, then the discharge along the surface may be generated on its surface. This condition is more common when the terminal lead discharges along the surface of the cushion block.
Similarly, if some connections loose or metal parts potential suspension will lead to spark discharge, such as a winding support nut loosening, resulting in a winding shielding aluminum foil potential suspension, the end screen lead contact or poor welding or even disconnection, will cause such a failure. In the combination of connection, if the micro-current transformer connection splint, bolts, nuts loose, the end screen grounding nut loose, tap fastening nut loosening, etc., may increase the contact resistance, resulting in local overheating failure.
In addition, improper maintenance management on site should also be given attention. This is because if the micro current transformer water is damp, it may be related to the sealing structure and sealing material used in the manufacturing process, but also has the maintenance management problem. Generally speaking, the field vacuum degasification is not sufficient or the maintenance does not carry out vacuum drying, resulting in the oil dissolved gas is easy to saturation or oily paper insulation in the remaining bubbles and moisture content is higher. All of this will leave a safety hazard to the miniature current transformer.