Insulation Sleeve Design Ideas

Referencing national standards is the basis. The domestic standards are mainly based on GB/T 4109 "Technical Conditions for High-voltage Bushings" and DL/T 593 "Common Technical Requirements for High-voltage Switchgear and Control Equipment Standards", which provide detailed regulations for creepage distance and dry arc distance of different types of bushings. For example, the creepage distance of 110kV oil-immersed bushings in the Class II contaminated area is required to be no less than 31mm/kV.
Dynamic simulation verification is necessary. By establishing a three-dimensional model through electromagnetic field simulation software, the electric field distribution under different humidity and temperature conditions can be simulated to find the risk points of excessive local field strength. A design institute once found the problem of electric field concentration at the edge of the flange through simulation in the design of 550kV GIS bushings, and adjusted the insulation distance from the original design of 1850mm to 2100mm.
Leaving a safety margin is an experience. In actual design, a margin of 10%-15% is usually added to the calculated value, especially for important hub substation equipment. In a converter station project, designers increased the insulation distance of Switchgear Insulating Bushing from the theoretical value of 6.3 meters to 7.1 meters, successfully withstanding the test of once-in-a-century wet snow weather.