Optimal Design of Insulation Structure of HV-HF Transformer Based on High-Frequency Insulation Properties of Gas-Solid System

Abstract

Although the increase in frequency brings many advantages such as the higher transmission efficiency and lower volume for high-voltage high-frequency (HV-HF) transformers, the insulation performance of dielectric is noticeable degraded. Through a high-frequency test platform, the insulation tests on gas-solid insulation system were performed under the frequency of 1 kHz~20 kHz. The breakdown characteristic of polyimide films in air and the flashover characteristic of gas-solid insulation system were studied. Subsequently, the insulation structure of the dry-type HV-HF transformer was designed in consideration of volume and insulation performance. Finally, the applied voltage withstand test was performed on a simple dry-type transformer model. Experimental results show that the applied voltage vs. durable time $({V}-{t})$ curves of polyimide films shift with the increase of frequency due to the high-frequency thermal effect, and the flashover voltages are decreased with increasing frequency. The reliability of the insulation structure design results was confirmed by the applied voltage withstand test on the dry-type transformer model.