Driven by China’s “14th Five-Year Plan”

the UHV project is expanding into higher altitudes

where ball-plane gaps ranging from 0.75 to 2.5 m are widely used in converter station valve halls. However

current external insulation designs rely heavily on extensive test data. Therefore

a mathematical and physical model of the whole process of ball-plane gap streamer-stable leader transition considering the influence of altitude is proposed

which has important engineering application significance. This paper focuses on three critical processes during the 3 m gap discharge of a 1.3 m diameter ball-plane in a UHV converter station at altitudes of 50 and 2 200 m: initial streamer initiation

streamer-leader transition

and distorted electric field recovery. In the initial streamer stage

the dome cone distribution model of space charge dome is proposed

enabling the quantitative calculation of both the space charge distribution σ(x) in the streamer region and the injected charge Qz. During streamer-leader transition

this paper proposes a calculation method for the initial streamer simulation injection current under various altitude conditions

and the whole process simulation of conversion is realized. For the recovery stage of the distorted electric field

the dark period stage is organically combined with the initial streamer stage and the streamer-leader conversion stage

and a numerical calculation method of electric field recovery time is proposed. Finally

this paper constructs a mathematical and physical model of streamer-stable leader transition considering the influence of altitude

which lays a foundation for future research and improvement of the mathematical and physical model of the whole process of long air gap discharge.