Overvoltage and insulation coordination for ±1100 kV UHVDC converter station

In order to specify the overvoltage and insulation level of equipments in ±1100 kV UHVDC converter stations, the arrester configuration scheme and some basic parameters for ±1100 kV Zhundong converter station are proposed. Overvoltage of equipments in AC system, valve hall, DC busbar, and neutral busbar are also calculated in accordance with the fundamental principles of arrester configuration for UHV converter stations and the existing experiences in insulation coordination of ±800 kV UHVDC converter stations. The work is done also for specifing insulation levels for ±1100 kV UHVDC converter stations of the ±1100 kV UHVDC power transmission project from Zhundong to Sichuan in China. Thus, the recommended insulation margins that determine the insulation levels of converter station equipments are proposed: the insulation margins for thyristor valves are 10%/10%/15% for switching impulse/lightning impulse/steer front impulse; the insulation levels of lighting and swtiching impulses are recommended as 2600 kV and 2150 kV respectively for 1100 kV DC buses, and as 2250 kV and 2100 kV respectively for equipments at the valve side of high-voltage Y/Y converter transformers.