| Traction power supply system is an important part of heavy-haul railway,Lightning strike is one of the important factors that causes traction power supply system to trip.The impact of lightning strikes on the traction power supply system can be divided into faulty lightning strikes（lightning fault）and non-faulty lightning strikes（lightning disturbance）.The faulty lightning strike is a permanent fault,and the relay protection should act quickly and reliably.Lightning disturbance means that it doesn’t cause a permanent fault in the traction power supply system.As a transient fault,although the relay protection device will also act,when the lightning current leaks through the ground path,the power can be restored by automatic reclosing.It can be regarded as a kind of interference of traction power supply system.However,the lightning disturbance wave formed by the lightning in traction power supply system is often a unipolar pulse wave.Due to its extremely short rise and decay time,it contains a lot of high-frequency components.The lightning disturbance signal contains a lot of high-frequency components,which belongs to high-frequency interference.Line protection based on traveling waves or transients can’t identify such high-frequency interference sources as lightning disturbance accurately,and the protection will inevitably suffer from interference and malfunctions.It can be seen that not all lightning strikes will cause permanent failure of the system.If the lightning disturbance signals can be effectively identified,unnecessary trips can be greatly reduced,and the possibility of relay protection misoperation can be greatly reduced,thereby it can improve the economic benefits and the reliability of power supply in the railway system effectively.Therefore,focusing on the problem of lightning disturbance in heavy-haul railways,the lightning disturbance recognition method for heavy-haul railway traction power supply systems has been studied.The main work is as follows:First of all,a simulation model of a heavy-haul railway traction power supply system was built in PSCAD/EMTDC to simulate normal operation,lightning disturbance,lightning strike failure,grounding and short-circuit fault and parallel capacitor compensation device switching transient processes.Based on this,transient voltage and current frequency characteristics is analyzed by FFT,and studies the impact of the lightning strike distance,short-circuit distance,transition resistance and other factors on the frequency distribution characteristics and content,which will lay the foundation for the research on the identification method of the lightning disturbance of the heavy-haul railway traction power supply system.Secondly,based on the wavelet energy distribution coefficient,a method for identifying lightning disturbance is studied.Combining the measured signals with the simulation signals,the transient signals such as lightning disturbance with actual operating characteristics are obtained,wavelet energy distribution coefficients are used to solve the energy statistics of each signal.According to the energy distribution difference of each transient and other signals,three thresholds of K1=20,K2=14 and K3=11 are used to identify five types of transient current signals quickly,and using multiple sets of simulations to verify that the identification method is accurate and effective.Finally,prototype verification of lightning dsiturbance identification method is achieved.Lightning disturbance identification prototype of the heavy-haul railway traction power supply system at a traction substation is installed.The identification algorithm in the prototype system is verified.The verification results show that the identification prototype can correctly identify normal operation,lightning disturbance and lightning strike failure,and it has certain accuracy and engineering practicability.It can effectively identify transient signals such as lightning disturbance and reduce unnecessary trips in traction substations.It is extremely important for ensuring the reliability of power supply for heavy-load railway traction power supply systems. |
