Overvoltages caused by blocking twelve pulse h.v.d.c. schemes

This paper describes the results of studies carried out to investigate the steady-state overvoltage which can occur if an h.v.d.c. scheme is blocked in the absence of fifth and seventh harmonic filters. The results of analytical and model studies show that the saturation of the convertor transformer caused by regulation can cause high resonant overvoltages. The sensitivity of the overvoltages to parameter changes is also shown.