Coordination Study On 220kV Saturated Iron Core Superconducting Current Limiter And Distance Protection Of Transmission Lines

With the expansion of power network scale and the increase of grid interconnection,the increase of power load and the improvement of power quality are fulfilled,at the same time the short-circuit current of some certain nodes are seriously exceeded in the system.When the short-circuit current exceeds the maximum capacity of the circuit breaker,the security of the system is threatened.Although traditional current-limiting measures can limit the short-circuit current to a certain extent,they have many disadvantages of reducing power supply reliability,flexibility,increasing network loss,the issue cannot resolved fundamentally by these methods.With the arising of high temperature superconducting materials and development of superconducting technology,the SISFCL is gradually caught the attention of industry and academia with many advantages,such as low impedance in steady-state,impedance changes rapidly when the fault occurs,high impedance in current-limiting state,keep superconducting state during the whole current-limiting process.The access of SISFCL can not only preserve the benefits brought by the power interconnection,but also the system is always in a safe and stable state by limiting the short-circuit current effectively.The SISFCL acts as an inductive impedance when the power system is short-circuited,the measurement of electrical quantities are interfered while the current is limited by SISFCL.In order to promote the application of SISFCL in power systems,it is necessary to study a series of compatibility issues with the power system,such as the coordination of problem between SISFCL and transmission lines distance protection.The cooperation of 220 kV SISFCL and transmission line distance protection are analysed in this thesis.Firstly,the development and application of superconducting technology and the classification of superconducting fault current limiter are summarized.Secondly,the development of SISFCL and the research status at dometic and foreign are summarized.Thirdly,the structure and working principle of SISFCL are introduced in detail.The geometric model of SISFCL is established in ANSYS Maxwell finite element analysis software.The impedance of SISFCL changes with the AC winding current is calculated by the analytical method and the energy method in steady-state and current-limited state.The simulation model is established in the PSCAD software using geometric parameters and mathematical models,the fault current reduction rate is simulated after the SISFCL connected to the high voltage transmission line,and the influence of SISFCL on differential current pilot protection and zero-sequence current protection of transmission lines are analyzed.Finally,the influence of SISFCL on the distance protection of each section of transmission line are analyzed by taking the single power supply system as an example.Three ways are introduced to improve the coordination between SISFCL and transmission line distance protection: resetting impedance,adjusting the impedance circle in real time and changing the connection mode.Simulation verification of three methods is carried out,which provides reference for the application of SISFCL in power system.