Causes of current transformer failure

1. Structure
Usually, when the voltage is higher than 32kv, the materials used to make the internal structure of the transformer generally use thin paper insulating materials, and when the voltage reaches 220kv, the internal materials of the transformer usually use capacitive materials.
2. Root cause of transformer failure
(1) Failure caused by thermal breakdown of insulation. Generally speaking, the stability of a current transformer that can withstand high voltage is better, but in some cases, when a large current can also pass through, but the temperature of the insulating medium will rise due to high voltage, once it exceeds its At the limit of the temperature that can be tolerated, the insulating material will be broken down by high temperature, which will cause the current transformer to fail.
(2) Failure caused by partial discharge. Under normal circumstances, the operation of the main capacitance of the 220kV circuit transformer is evenly distributed, but if the technical process is not up to the standard, the smoothness of the capacitor plate cannot meet the requirements due to process reasons, which will lead to the tightness of the insulation wrapping if it cannot be mastered Well, then it will cause the uneven displacement of the capacitive screen. If the U-shaped clip is too tight, the insulation will be deformed. At the same time, the integrating bubble will easily cause the voltage distribution to change, which will make the Among others, the field strength of some capacitive screens is higher than others, resulting in partial discharge. If it cannot be found and dealt with in time, the capacitor mandrel will fail.
(3) Humid environment. Due to its poor sealing, a strong discharge phenomenon will occur inside the transformer, destroying the insulation of the transformer, and the liquid generated in a humid environment will deposit on the bottom of the capacitor mandrel, so the capacitor mandrel The bent part becomes the place with the worst insulation effect. Because it is in a long-term working state, it is easy to cause breakdown of the capacitor mandrel, causing it to generate power failure.
(4) Reasons for insufficient drying and degassing. The current transformer must be filled with vacuum oil, otherwise the gas will not be able to be discharged, making it unable to form a vacuum state. In addition, the short degassing time leads to incomplete degassing. Under the bidirectional action of voltage and temperature, the current sensor will continue to heat up, resulting in electrical aging breakdown and failure.
(5) Mistakes in personnel operation. The most common faults of transformers are more likely to be caused by personnel. Most of them are caused by personnel mistakes in operation, which make the lead wire joints loose, and the secondary windings appear due to poor workmanship during vacuum oiling. Open circuit and other conditions will cause these errors in operation to cause overheating or discharge in some parts of the power system. The occurrence of these conditions will lead to abnormal results in the analysis of dissolved gas chromatography in oil.
3. Preventive test and partial discharge measurement
my country still attaches great importance to the power system. From the relevant regulations on current transformers, it can be seen that relevant regulations have also been made on the development of transformer prevention experiments. The capacity and dissolved gas chromatography in oil are analyzed, and the insulation resistance in the winding and the last screen is measured. These results can clearly see that the problem is caused by various factors such as moisture or insufficient craftsmanship. potential failure. The local defects in the transformer cannot be clearly detected during the routine insulation test, but if the partial discharge measurement method is used, good measurement results can be achieved. After the transformer discharge measurement is overhauled, the relevant regulations have also been changed.