High voltage power capacitors are operated in power systems and can be used to compensate inductive reactive power in the power system, filter harmonics in the power system, and so on. Capacitor units are generally produced and sealed in an environment below 1000 m above sea level, and the products may be operated in plain areas or in plateau environments at an altitude of 3000–4000 m [1, 2]. Due to plateau environments, the atmospheric pressure is low, which may cause the expansion of the capacitor case, resulting in deformation of the product shell. Tests show that: the plateau environment of the low pressure on the deformation of the capacitor case is small, room temperature, low air pressure capacitor case deformation is close to zero; high temperature, by the volume of the internal material expansion of the capacitor, resulting in a certain amount of deformation of the case products, used to compensate for the change in the internal volume, but the case deformation of the different air pressure differences in deformation is small, the largest deformation is not more than 1 mm.