In the power frequency withstand voltage test of a 12 kV vacuum circuit breaker for plateau

the airspaceof coupling bolt is susceptible to breakdown. In this study

a simulation model was established by the 3-dimensionalmodeling software Solid Works

and the electrostatic field was simulated by Ansys Workbench to obtain the distribu-tion diagram of the equipotential lines of the circuit breaker and the distribution of the electric field. Th

e concentra-tion location of the electric field and the reason why the breakdown occurred in the voltage withstand test of the prod-uct were found by analyzing the distribution diagram of the equipotential lines and the distribution of the electricfield—the unreasonable designs of the insulation rod and the pole umbrella skirts resulted in distribution distortion ofhigh and low potentials. A method for optimizing the insulation rod and the umbrella skirts was proposed to increasethe air clearance on the premise of guaranteeing safe operation of the equipment and minimum cost. Finite elementsimulation of the optimized model was conducted with the software ansys

and the result indicates that the maximumfield strength in the air domain decreases by 14.8%

from 3.31×106 mV/mm to 2.82×10

6

m V/mm. According to the na-tional standard GB/T 20635—2006 special environment condition—technical requirements of high-voltage appara-tuses for plateau

insulation withstand voltage test of the optimized equipment was conducted

and the result show that the power frequency withstand voltage level gets up to 51 kV

completely meeting the operation requirements forthe altitude of 2 000 m. It is proved that the proposed optimization solution can effectively solve the above breakdownproblem of the 12 kV vacuum circuit breaker. And this solution needs minimal change of the original structure

leastreconstruction

and lowest cost. This study may offer a reference for optimization design of insulation structure of me-dium voltage switchgear for plateau.