Influence Of Shunt Capacitor Based On Secondary Arc Suppression On Power System

In order to guarantee the operational stability of the power system,the role of single-phase auto-reclosing(SPAR)in the high-voltage system is particularly important.The single-phase-to-ground(1PG)fault instantaneous occurs in ultra high voltage(UHV)transmission lines,and the extinction of secondary arc plays a key role in SPAR and it is one of the crucial technical challenges for UHV power transmission.Presently,the methods for suppressing secondary arc include the four-legged shunt reactor(FLSR)and the high-speed grounding switches(HSGS).The FLSR costs much and the neutral reactor must have a high insulation.It may not work on closely coupled parallel lines due to the possibility of resonance.The HSGS is complex and needs a special protection system.The shunt capacitor of circuit breaker is studied as a simple and effective arc suppression technology.It has theoretical significance and technical value for the popularization engineering application of shunt capacitor.This thesis firstly combines China's UHV AC demonstration engineering transmission lines,establishes theoretical and simulation models,and uses equivalent circuit method and vector analysis:to obtain the mathematical relationship between secondary arc current and recovery voltage at fault location.The EMTP simulation is used to analyze the recovery voltage rise rate(RRRV)and secondary arc extinction time.It is concluded that the shunt capacitor has a certain effect on the gentle RRRV and the shortened extinction time,and the downward trend of the two is basically the same,which is beneficial to the secondary arc zero-off.The effects of other factors on the RRRV are further studied,and the results show that it can be minimized when the line can be connected to its own parameters to install the shunt capacitor,and good consistency is achieved through simulation analysis and theory.Secondly,the structural model and topology principle of the shunt capacitor of the circuit breaker are expounded.For the simple power system with shunt capacitor,the internal fault current flow of the system under 1PG fault is analyzed,and its transient process is studied in detail based on the equal area rule.The MATLAB platform is used to build a simulation model of single machine infinite(SMIB)bus power system and a multi-machine power system.The effects of circuit breaker with or without shunt capacitor and different faulting clearing time on transient stability of system are simulated.Theoretical analysis and simulation results show that installing the shunt capacitor of the circuit breaker can effectively reduce the swing amplitude and attenuation period of the power angle,and increase the critical clearing angle,which is beneficial to make the transient process of the system recover stably quickly.In this thesis,the research on the influence mechanism of shunt capacitor on the breaking characteristics of UHV double-break circuit breakers(CBs)is carried out.Based on the actual UHV transmission lines in China,an equivalent model analysis circuit under 1PG fault is established.The calculation equation of transient recovery voltage(TRV)and RRRV of extra-high voltage CBs before and after the installation of CG is obtained.Based on the CG equivalent model,the voltage characteristics of CBs under long line fault(LLF),near-field fault(SLF)and out-of-line fault(BTF)are simulated.It is concluded that the circuit breaker RRRV decreases linearly with the increase of CG under the LLF and BTF faults,and decreases exponentially under the SLF fault condition.The simulation calculation is in good agreement with the theoretical analysis.The results show that the addition of CG to UHV CBs can enhance the breaking performance of the circuit breaker,facilitate the rapid zero-crossing of the secondary arc current,improve the operational reliability of the UHV system,and improve the performance of the circuit breaker,and the performance requirements of the circuit breaker are the most demanding when breaking the SLF fault.The research results can be used as the analysis and theoretical basis for the test and design of UHV transmission line CBs.