Study On The Algorithm Of Wide Area Longitudinal Protection In High-voltage Power Grid

Wide area protection is a new subject in recent years, it uses more information in power system to achieve wide area protection. Wide area protection can solve some of the issues in the traditional relay, and coordination with the traditional protection to ensure the security and stability of the power system operation. In this dissertation, the background and research situation of HV transmission line protection and the wide area protection are introduced, and various wide area protection systems proposed at present are summarized. Wide area protection algorithm based on longitudinal direction and current differential are proposed.First of all, according to the difference between energy integral function of different fault direction, a wide area longitudinal protection based on energy integral directional principle is proposed. Combined with phase-mode conversion of fault voltage and fault current, energy integral function is used to determine the fault direction, and the longitudinal direction fault identification algorithm and the wide area protection strategies of longitudinal direction are given. Theoretical analysis and simulation results show that the algorithm has high sensitivity and accuracy.Secondly, according to difference of the values of transient energy between different lines of the substation after the system fault, a wide area longitudinal protection based on the transient energy directional principle is proposed. The current of lines is decomposed by wavelet in order to achieve the value of transient energy to determine the fault direction, combined with the algorithm of longitudinal direction fault identification and the wide area protection strategies of longitudinal direction for fault location and cutting. Theoretical analysis and simulation results show that the algorithm has high sensitivity and accuracy.Finally, in the funditional of study of existed wide area current differential protection, a wide area longitudinal protection algorithm based on regional of protection matrix is proposed. Through a series of operations of system matrixs such as incidence matrix, the regional of protection matrix and the network topology tree are derived, then a wide area differential protection strategies and the working process of protection are given. Theoretical analysis and simulation results show that the algorithm has high sensitivity and accuracy.