Research on the transient characteristics of current and voltage during zero crossing natural shutdown of anti parallel thyristors in hybrid on-load tap changer

Abstract The thyristor-assisted arc-quenching hybrid on-load tap changer (OLTC) integrates the benefits of both mechanical and power electronic OLTCs, utilizing anti-parallel thyristors to aid in mechanical contact switching. However, this hybrid OLTC faces challenges such as high di/dt during thyristor conduction and significant peak voltages and du/dt at thyristor turn-off. This paper presents a simulation study on the transient current and voltage characteristics during thyristor conduction and natural turn-off. It also determines key technical parameters like the critical du/dt and di/dt for the thyristor in a 35 kV hybrid OLTC.