Study On Fault Location Of Lightning Strikes On High-voltage Overhead-cable Hybrid Transmission Lines

Lightning strike fault is the highest proportion of fault type that causes tripping of high voltage transmission line.Under the current situation that high voltage overhead cable hybrid transmission line is more and more applied to the transmission grid,while there is no special study on lightning strike fault location of high voltage hybrid transmission line at present,although the principle of traveling wave location of hybrid transmission line has already been widely applied in power system,but there are still exist the following problems:wave velocity inconsistency,identification of reflection wave,the accurate extraction of the wave head,long distance transmission attenuation serious distortion,etc.At the same time,although non-fault lightning strike does not cause short circuit,it will produce traveling wave with high energy,which will cause interference to the traveling wave device and lead to the misjudgment of the traveling wave ranging device.Therefore,the study of lightning fault location of high voltage hybrid line has a great impact on ensuring the safe and stable operation of electric power system.Based on the analysis of the traveling wave transmission theory,combining the existing fault location methods and the law of traveling wave transmission and refraction in hybrid transmission lines,a five-point traveling wave fault location principle based on current phase comparison is proposed in the paper,and it is applied to the fault location of high voltage double-circuit overhead-current hybrid transmission lines on the same tower,aiming at solving the problem of long distance and high voltage,the traveling wave attenuation of hybrid transmission lines and the errors caused by capacitance distribution to the ground,aiming at solving the positioning errors caused by the inconsistency of overhead-cable wave velocities.The fault section of hybrid transmission lines can be reliably judged by multi-point phase comparison,and the velocity of hybrid transmission lines can be solved online by five-point ranging using near-end measuring points.Fault location can still be accurately achieved when polarity of measuring points is reversed in hybrid transmission lines.It can be shown that the proposed ranging method is accurate and feasible according to the simulation results.In this paper,a simulation model for lightning stroke is established to simulate non-fault lightning stroke,counterattack,shielding and single-phase grounding faults.By analyzing the simulation results of traveling wave components,reliable criteria for lightning stroke identification are obtained.It shortens the time of fault detection.In this paper,the principle of local characteristic scale LCD decomposition is applied to the identification of traveling wave head of lightning strike fault in hybridtransmission lines to improve the accuracy of traveling wave head recognition.It can be shown that the method improves the accuracy of traveling wave ranging according to the simulation results.