1.Common faults of voltage transformer
For voltage transformer, the most common reason is that the design structure is unreasonable, which causes the potential suspension and discharge of the core bolt in operation. This kind of failure was common in the 1980s. At present, with the improvement of domestic design structure, the voltage transformer newly put into operation has been greatly improved in this respect. Another common fault of voltage transformer is poor insulation support, followed by poor sealing at the end, which causes water intrusion and dampness.
2. The common faults of current transformer are often related to manufacturing defects. Here, it is briefly described as follows:
1) The insulation of current transformer is very thick. Some of the insulation is loose, and there are wrinkles between the insulation layers. In addition, the vacuum treatment is poor and the impregnation is not complete, resulting in gas cavity, which is easy to cause partial discharge fault.
2) The size and arrangement of the capacitor screen do not meet the design requirements, and even the capacitor plate is not smooth and flat, even dislocation or fracture, so that its voltage sharing characteristics are damaged. Therefore, when the electric field strength along the surface of partial solid insulation reaches a certain value, it will cause partial discharge.
The direct result of the above partial discharge is that the insulating oil is cracked and a large amount of X wax is formed between the insulating layers, and the dielectric loss increases. This kind of discharge has cumulative effect. If it is allowed to develop, the gas analysis in oil may have the characteristics of arc discharge.
3) Because of the uncleanness or high moisture content, surface discharge may occur on the surface of the material. This situation is often seen in the primary terminal lead along the pad surface discharge.
4) Some loose connections or potential suspension of metal parts will lead to spark discharge, such as loose primary winding support nut, potential suspension of primary winding shielding aluminum foil, poor contact or welding of terminal screen lead, or even broken wire will cause such faults.
5) Loose clamping plate, bolt and nut of secondary connection, loose grounding nut of terminal screen and loose fastening nut of tap may increase contact resistance and cause local overheating fault. In addition, attention should also be paid to improper maintenance and management on site. For example, the transformer water into the damp, although may be related to the manufacturer's sealing structure and sealing materials, but there are also maintenance and management problems. Generally speaking, insufficient vacuum degassing on site or no vacuum drying during maintenance may cause the dissolved gas in oil to be saturated or the residual bubbles and moisture content in oil paper insulation are high. All of these will leave a potential safety hazard to the equipment.
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