Unsimultaneous reclosure technique to reduce torsional torques and enhance system transient stability

In this paper, torsional torques on a turbogenerator shaft induced by three-pole high-speed circuit breaker reclosure are deduced and analysed. The results show that shaft torsional torques may be aggravated when reclosing onto permanent faults and the reclosing time also has significant effects on shaft torsional torques. To solve this problem, the paper presents a new method “unsimultaneous reclosure” for three-pole reclosing, in which each phase of the three-phase circuit breaker recloses sequentially with a fixed time delay in between. Theoretical analysis and simulation studies show that the proposed method can greatly reduce the torsional torques in the case of unsuccessful reclosure, thereby improving power system transient stability