Research On A New Method Of Longitudinal Protection And Fault Location For Outgoing Lines Of Wind Farms

To accelerate the green energy industry development,the provinces have issued guidance policy document to support sustainable and healthy development of green energy,new energy become the main plate,there will be installed has expanded gradually.the transmission line as an important channel of green clean energy delivery,operating reliability and rapidity of longitudinal protection and rapid positioning and troubleshooting is extremely critical to the safe operation of the line stability.Based on the mathematical model,equivalent circuit and control strategy of doubly-fed induction generator,this paper deduces and analyzes the analytical formula of short-circuit current including the pry bar input and the RSC control under the condition of three-phase short-circuit fault.According to the structure and control strategy of grid-connected inverter,the analytical formula of three-phase short-circuit current under the control of GSC is analyzed and derived.Based on the analytic expression of doubly-fed type power supply,inverter power supply fault current component is complex,analysis of doubly-fed type power supply fault current was found to contain the rotational speed of frequency components and freedom,inverter type power source shows fault current of power frequency,fault current weak feed characteristics and contains a lot of harmonic will result in a wind farm stand out of line protection method based on the amount of power frequency of failure.The existing fault model-based correlation protection neglects the influence of phase electromagnetic coupling,cannot reflect all fault types and is not strong in resisting transition resistance.The protection method based on waveform similarity has adaptability problems,such as false fault pulse,data missing,data not synchronized at both ends,etc.,which may lead to misoperation and rejection of protection.Extract terminal side fault current high frequency component found under the influence of wind power station fault features,the high frequency current component spectrum aliasing,wave head identification to bring huge difficulties,also exist wave head error calibration time,solution of time domain differential equation of range finding principle also not considering the influence of line capacitance,thus fault location reliability is low.To solve the above problems,this paper proposes the longitudinal protection of the sent line based on the time domain modulus identification line parameters and the time domain full current spatial trajectory identification.The time domain modulus identification line parameters are mainly based on the fault in the zone and outside the zone,the line equivalent model is different,and the stability of the identification parameters is different.Combined with the E-DTW distance detection identification parameter stability,the protection action criterion is constituted.Time-domain trajectory recognition relies mainly on the normal operation of the full amount of current space and external fault cases full time-domain current fault phase space track in the second,four quadrant,internal fault in the first,the characteristics of the three quadrants,computing into the first,the second,four quadrant three quadrants and trajectory into points constitute the criterion of protection operation ratio of full time domain fault phase current space trajectory fitting straight slope half cycle of positive and negative protection action of criterion.The simulation results show that the two proposed longitudinal protection methods have good performance and strong adaptability.This paper proposes and proves the correctness of the theory of post-test simulation time reversal focusing for double-ended and single-ended fault location of the transmission line.The simulation and measurement results show that the proposed methods have high reliability and practical significance in engineering.