Influence of three-phase reclosure sequence on transient voltage stability

Larger effect of three-phase re-closure sequence on system's transient voltage stability when re-closing to permanent disturbance is discovered. A single load infinite bus system is taken as an example to discuss this mechanism. The transient process starts from a permanent fault occurred, then a three-phase breaker is tripped, then reclosed to permanent fault, till the three-phase breaker is tripped again. Load bus voltage transients of this process are calculated and the corresponding analytical expression is also derived. By comparing the bus voltage under the two re-closure sequences, it is discovered that under constant impedance load model, constant current load model, and dynamic load model, bus voltage can be increased by re-close to head terminal of transmission line and slip ratio can be decreased when breaker is tripped again, which is beneficial to transient voltage stability of the system; while under constant power load model, re-closure sequence depends on fault distance, and the corresponding analytic expression is derived. In view of the difficulties in solving it, a practical setting strategy by combining off-line calculation and on-line setting is proposed. The correctness and effectiveness of re-closure strategy is verified by simulation results in single load infinite bus system and 2010 Southern China power gird. This work is supported by National Natural Science Foundation of China (No. 50847043, 90610024, 50467002, 50347026), Natural Science Foundation of Yunnan Province (No. 2005F0005Z) and Foundation of Yunnan Provincial Department of Education (No. 07Y40615).