Air is the most important insulating medium in the power system

but the lack of relevant experimental results after air gap breakdown currently restricts the understanding of the insulation recovery process. In this paper

the schlieren observation technology was used to quantitatively observe the gas density change of the discharge channel after air gap breakdown

to analyze the morphological changes of the discharge channel

and to calculate the recovery degree of gas density in different areas of the discharge channel based on the schlieren images. The test results show that

after the gap breakdown

the shape of the discharge channel changes from bending to straight and then gradually becomes irregular.The gas density recovery rate in different areas of the discharge channel is different

and the gas density in the area near the rod electrode recovers faster than other areas; based on the gas density recovery degree proposed in this paper

the gas density of the discharge channel recovers within 200 ms after the gap breakdown under the experimental condition. The experimental method and results in this article can provide a reference for the research of the discharge channel deionization time in the power system’s reclosing time.