The Approach To Adaptive Sequential Reclosure In Transmission Lines

We must proceed from two aspects of adaptive sequential reclosing: effectively identify the nature of the fault and accurately capture the time of arcing if we want to improve the safety and reliability of power system.The former can avoid the breaker reclosing on permanent fault blindly to protect the power system from a more severe shock;the latter can avoid the circuit breaker reclosing on the secondary arc stage of transient fault,and reduce reclosing time interval and the unnecessary open-phase operation time.Two adaptive sequential reclosing methods are proposed in this paper: the phase angle difference criterion of terminal voltage at open-phase and the criterion of amplitude ratio change of fundamental component terminal voltage at open-phase.Firstly,the research background and current situation of single-phase,three phase and adaptive sequential reclosing are introduced,and the characteristics of arc and recovery voltage under single-phase adaptive reclosing and adaptive sequential reclosing are analyzed.Aiming at the single-phase and multi-phase faults occurring on transmission lines with or without shunt reactors,the model is built by ATP-EMTP software,and the waveform diagram of terminal voltage at open-phase is obtained through simulation.Secondly,an adaptive sequential reclosing method based on the change of the amplitude ratio of open-phase voltage and the reference phase voltage is proposed.the variation rule of the fundamental wave amplitude ratio between the phase terminal voltage at open-phase and the reference phase voltage is analyzed under the condition of two phase short circuit and two phase short circuit when the transmission line without shunt reactors is also connected with the adaptive sequential reclosing.The principle and implementation steps of using this criterion to capture two times of arc quenching time is briefly introduced.The method is simple and reliable,and the amount of calculation is small.ATP-EMTP and MATLAB simulation verify the correctness of the criterion under the condition of different power source angle difference,fault point position and transition resistance value.Finally,an adaptive sequential reclosing method based on phase angle difference of open-phase voltage is proposed.The phase difference between terminal voltage at open-phase and reference phase voltage is studied under two phase short circuit and two phase short circuit under transmission lines with or without shunt reactors.The sudden change of phase angle before and after the arc fault is used to identify the nature of the fault and capture the arc extinction time.The method is simple to realize,can effectively distinguish between permanent and instantaneous faults and accurately capture the extinguishing time of two arcs.This method is not only suitable for transmission lines without shunt reactors,but also for transmission lines with shunt reactors.The correctness and effectiveness are verified by ATP-EMTP and MATLAB simulation.