Analysis of High Voltage Divider Breakdown Failure Mode

Author： GOZ Electric Time：2024-05-22 09:34:30 Read：13

    High-voltage voltage dividers have extensive and important uses in high-voltage components: on the one hand, they serve as high-voltage voltage divider monitoring to reflect whether the high-voltage output of high-voltage components is normal; on the other hand, they serve as high-voltage voltage stabilizing feedback to ensure that the high-voltage component outputs high voltage stability. Since the system has high requirements for the pressure indication accuracy and stability of the high-voltage voltage divider, we proposed a development project for a high-voltage and high-stability voltage divider. Initially, the overall infusion epoxy resin solution was adopted, as shown in the structure. After many improvements to the potting materials, the temperature stability of the samples basically meets the requirements. In order to further improve the temperature stability of the high-voltage voltage divider and reduce the weight of the product, the product structure has been improved and a technical solution is adopted to cover the ceramic shell without perfusion. The structure is as shown. The temperature stability of the high-voltage voltage divider with this structure is significantly improved. However, after this high-voltage voltage divider was officially installed into the high-voltage components, serious breakdown failure occurred. We conducted in-depth analysis and experimental research on this.

1. Fault phenomenon

     After the high-voltage divider was installed into the high-voltage component, a power-on check was performed before the silicone gel was poured into the whole. All technical indicators were normal. Then. To fully inject silicone gel into high-pressure components, the process is as follows: 1) Prepare, stir the filling material, and vacuum to remove air bubbles in the filling material: 2) Slowly inject the filling material into the high-pressure component under normal pressure; 3) Place the high-pressure component into the Place in a vacuum tank. Vacuum for 5 to 8 minutes. Eliminate air bubbles: 4) The high-pressure component filling material is cured at normal temperature and pressure for 24 hours. After the silicone gel was poured and solidified, the high-voltage components were tested for normality. An abnormality was found during the power-on process: there was sparking in both sets of circuits, and the high-voltage partial voltage indications were both zero. High-voltage components mainly include high-voltage inverters, high-voltage capacitors and high-voltage voltage dividers. After pulling out the above components. The re-power test found that one high-voltage voltage divider ignited at 2.8 kV: the voltage indication of the other high-voltage divider was always zero, both sets of converters were damaged, and the two high-voltage capacitors had normal voltage resistance.

2. Failure analysis and verification

     Sparking during the power-on process can easily lead to damage to the inverter. Therefore, first analyze and find the cause of sparking. When the high voltage voltage divider is applied to a high voltage, the partial voltage indication is zero, and sparking occurs at 2.8kV. These are very rare phenomena. Therefore, it is necessary to focus on the anatomical analysis of the high-voltage voltage divider and conduct experimental verification. Regarding the fault analysis and verification situation when the partial voltage indication is zero: Since the high-voltage voltage divider adopts a non-perfusion structure with a ceramic shell as shown in Figure 2, the voltage dividing resistor can move inside. After the two points a and b are in contact and connected, the Resulting in a partial pressure indication of zero. After dissecting multiple high-voltage voltage dividers, it was found that points a and b were in close contact with each other. Regarding the fault analysis and verification of low-voltage breakdown ignition: dissect the high-voltage divider with 2.8 kV ignition. It was found that there was an obvious accumulation of black carbon dust on the surface of the high-voltage resistor. It was initially suspected that the insulation damage of the high-voltage resistor body caused the high-voltage divider to ignite. However, after the carbon dust on the surface of the high-voltage resistor was removed, the withstand voltage and voltage indication of the high-voltage divider returned to normal. , eliminating the possibility of insulation damage to the high-voltage resistor body. The only possibility is that air breakdown has occurred inside the high voltage divider.