A survey of the flashover performance of HVDC converter station insulators

The operational experience of most of the HVDC converter stations in the world has been investigated, summarized and analyzed with regard to external flashovers across station insulators and apparatus. At some stations, some of the insulators have caused several flashovers soon after commissioning. The maximum flashover frequency occurred between 1987-1989, totalling about 20 flashovers per year at the 24 to 32 stations in operation. Several efficient countermeasures or maintenance methods have been developed. After the introduction of such measures, flashover frequency has normally been reduced to almost zero. During the last four years, the number of flashovers per converter station has been about 0.10, corresponding to about 0.05 per pole.