Safety strategy of power transmission channel coordinated with transfer capability support for power system emergency

Abstract

The overload endurance capability (OEC) of transmission equipment in power system emergency not only relates to the safety of equipment itself but also affects the security of the power system. The action threshold of the existing backup protection (such as distance protection zone 3) reacting to the overload condition is determined by the static thermal rating. The action time is set according to the sequence coordination of upstream and downstream transmission lines. This strategy ineffectively adapts to the surge overload current after power flow transferring, may cause backup protection false trip and accelerate the cascading trip of power system. The parameters and their influential factors that represent the OEC of transmission equipment were clarified in this study. The dynamic OECs of the switchgear, current transformer, and overhead line on the transmission channel were analyzed. The heavy load warning method of the transmission section based on the predicted continuous overload endurance capability (COEC), and the load adjustment and overload protection strategy based on the short-time overload endurance capability (SOEC) were proposed. Finally, the feasibility and validity of the proposed methods were verified through a case study. The proposed safety strategy can effectively utilize the SOEC to protect the safety of the power equipment and provide transfer capability support for the security of power system in emergency conditions.