Research On Graded Controllable High-resistance Power Protection Technology

The controllable shunt reactor(CSR)is an important reactive power compensation device in the EHV/UHV transmission system.The stable and reliable operation of the CSR is of great significance to the high voltage transmission system.The stepped controllable shunt reactor(SCSR)has been widely used in engineering because of its simple working principle,high response speed and high reliability.This dissertation focuses on the research on the working principle,model establishment,fault characteristic analysis,and protection scheme of the SCSR.It focuses on the fault characteristics of the SCSR in turn-to-turn short-circuit fault,and puts forward the corresponding electrical quantity protection scheme.Firstly,the dissertation introduces the principle of the CSR,analyzes the body structure and working principle of different types of CSR,and compares the advantages and disadvantages of different types of CSR.Taking the SCSR as the research object,the mathematical model is established,and the simulation model configured with actual engineering needs is built in the MATLAB/Simulink environment.It lays the foundation for next research.Secondly,the dissertation analyzes the fault characteristics of the common faults in grid-side winding,control winding and load reactors respectively,and illustrates the causes of the fault characteristics.According to the fault characteristics of different parts mentioned above,the electrical quantity protection scheme of SCSR body structure is proposed.The working principle of the configured protection is described,and the protection scope of each protection and the coordination relationship between different protections are studied.Finally,the electrical quantity protection for turn-to-turn short-circuit of SCSR control winding is studied,and the improved negative-sequence power directional protection is configured.The negative-sequence current of the control winding is selected as the protection start threshold,and the adaptive start threshold is set according to the compensation capacity.The negative-sequence current of the winding is detected to determine whether the system has faults,and the negative-sequence power directional angle calculated by the negative-sequence voltage and the negativesequence current at the head end of the grid-side winding is used to determine the location of the fault.When a small turn-to-turn short circuit occurs in the control winding,the directional angle of the negative-sequence power fluctuates.The negativesequence phase angle smoothing method based on dynamic average is used for processing,and the obtained negative-sequence power directional angle fluctuation is smaller and more stable,which can improve the protection reliability.Through simulation verification,compared with the traditional zero-sequence power directional protection,the improved negative-sequence power directional protection can increase the sensitivity of the SCSR control winding inter-turn protection.