Study on Insulation Characteristics Between Thyristor Radiators in Converter Station Valves at Different Altitudes

The converter valve based on thyristor level is one of the core equipment of HVDC transmission. However, due to the high failure rate of power components in the whole system, it is urgent to carry out research on the gap insulation characteristics of thyristor radiator inside the converter valve at different altitudes. The switching impulse, lightning impulse, DC and AC discharge tests of thyristor radiator gap in converter valve were carried out in Beijing (altitude of 55 m), Qinghai (altitude of 2500 m) and Tibet (altitude of 4300 m). The discharge voltage and its margin of various thyristor small gaps at different altitudes are compared and analyzed. The results show that with the increase of altitude, the air density decreases, and the discharge voltage between thyristor radiators decreases. At the same altitude, the 50% lightning impulse discharge voltage is the largest. Compared with the lightning impulse discharge voltage, the 50% switching impulse discharge voltage decreases by about 6.06%, the DC discharge voltage decreases by about 15.15%, and the AC discharge voltage decreases by about 51.61%. For the four voltage types of small gap between radiators, the equipment parameters provided by manufacturers in China have a large margin, and the margin is greater than 148%, which can meet the actual needs of engineering at different altitudes.