Measurement of discharge channel based on background oriented schlieren technique using an optimized algorithm

Thermal ionization is the main characteristic of long air gap breakdown. Using the thermal characteristics of the discharge channel can not only analyze the formation and development mechanism of the leader discharge but also better reflect the insulation recovery process of the discharge channel. The background oriented schlieren (BOS) technique is a method generally used for diagnosing flow fields. It can also be used to extract the gradient profile of the refractive index field in long-gap discharge channels, which can then be inverted to yield the temperature field. Based on the BOS, a 1-m rod–plate gap discharge observation system was built and the discharge test was carried out. By optimizing the refractive index reconstruction algorithm, a more accurate temperature field distribution of the discharge channel was obtained. By analyzing the evolution process of the discharge channel, the shock wave radius variation law and insulation recovery time of the channel were obtained, which had a guiding significance for the reclosing time setting.