Optimization of Intense Electric Field Electrodes for Pantograph Support Insulators of CRH2 High-speed Train under Overvoltage Conditions

The bolt above the 1 ^st umbrella skirt of the pantograph post insulator of the high-speed train will distort the electric field in its vicinity, and the overvoltage during the high-speed train passing from one electric section to another may cause arcs, and the partial arcs will burn the umbrella skirt or even induce flashover fault, so it is necessary to install a grading ring with a rational structure to reduce the local electric field intensity, and consider the change of the streamline distribution near the 1 ^st umbrella skirt after installing a grading ring, an elliptic grading ring (EGR) and rod shaped bolt shielding cover (SC) were designed in this paper. Then, the structural parameters of the grading rings were optimized by using the orthogonal test method, and the tests were carried out to obtain the change of corona inception voltage, 50% lightning impulse voltage, and power frequency dry flashover voltage. The results show that the installation of EGR and SC, meanwhile the maximum electric field strength at the root of the 1 ^st umbrella skirt decreased by 88.7%, the flashover voltage of the insulator model complies with the relevant specifications after optimizations. The corona discharge inception AC voltage value at the bolt end for the original model is 60 kV, no obvious discharge faculae can be seen around the ring surface when the voltage is up to 110 kV. The results can provide a reference for the structure selection and parameter optimization of the grading devices in high-speed airflow environment.