Single-ended Traveling Wave Identification And Fault Location Of Transmission Lines Based On Waveform Projection Characteristic

As the national economy advances and develops,and with the comprehensive promotion of the "dual carbon" strategy objectives,the role of electricity in national economic development is becoming increasingly prominent.As the link between the western energy base and the eastern load center,the importance of transmission lines is self-evident.Rapid and accurate positioning of transmission line faults is of practical significance for improving power supply reliability and power system stability.Therefore,improving the reliability of transmission line protection and improving the robustness of line distance measurement results are of great significance.The traveling wave fault location method is widely used for high-voltage,long-distance,and large-capacity power transmission line fault location due to its high theoretical accuracy and immunity to factors such as transition resistance and line topology.The single-ended fault location method has the advantage that it does not rely on communication and time synchronization between both ends,which is irreplaceable by the double-ended fault location method.The reliable identification of the second wavefront position and characteristics is a key factor in the effectiveness of the single-ended fault location method.However,the current single-ended fault location methods still have shortcomings in automatic wavefront detection and accuracy verification under complex fault conditions.In addition,in the case of a near-end fault,the reflected wave at the fault point is mixed with the high-frequency oscillation noise caused by the resonance of CT and the secondary-side cable,making it difficult to automatically identify the wavefront,which leads to the easy failure of the fault location method.Therefore,this paper proposes a single-ended traveling wave fault detection method based on waveform graph projection features and a near-end fault identification and location method based on waveform graph core sub-features.The specific contents include:(1)This text discusses the analysis of fault wave generation,propagation,reflection,and refraction processes from the perspective of wave processes for single-ended traveling waves in AC systems.The composition of the single-ended fault wave group at the observation point is analyzed,and the reflection wave group at the fault point and the transmission wave group of the opposite end busbar are examined from the perspective of identifying the dominant characteristics of wave head relative polarity and amplitude.It proposes the use of the single-ended ranging principle of the same polarity wave head group,which can fully utilize waveform information and has self-checking ability for ranging and results.At the data level,the influence of factors such as high-frequency noise and data loss on the fault wave is analyzed.Visualizing the traveling wave data can enhance the sharp features of the wave head mutation and enhance macroscopic insight into the waveform features.The interval,mutation strength,inclination angle,and other features of the wave head can all be quantitatively represented by the waveform projection.(2)In response to the limitations of the single-end traveling wave distance measurement method for reliable and effective identification of the second wavefront,a single-end traveling wave identification and distance measurement method based on waveform group sensitive angle detection is proposed.First,the attenuation and distortion in the propagation process of the line fault traveling wave are analyzed,and it is found that the local waveform of the wavefront exhibits sensitive angles and non-axisymmetric characteristics.Then,it is proposed to use the Radon transform to detect the most sensitive angle and distinguish the non-axisymmetric characteristics on both sides of the most sensitive angle,to achieve reliable identification of the initial traveling wave of a single fault and multiple same-polarity wavefront groups.Finally,a multi-distance measurement formula is constructed based on the time difference of multiple same-polarity wavefront arrivals,and the most reasonable distance measurement result is output.The proposed method transforms the time-domain wavefront identification into the detection of the most sensitive change direction and geometric axis symmetry in the waveform image space,with strong anti-interference ability,greatly improving the detection reliability and subsequent wavefront identification capability,and enhancing the redundancy of the single-end distance measurement formula.A large amount of actual measurement and simulation data testing shows that the algorithm is effective,reliable,intuitive,and widely applicable,providing a new way for single-end traveling wave fault analysis and distance measurement and its extended application.(3)Due to the lack of effective identification methods for near-end faults in transmission lines,and the shortcomings of standalone traveling wave measurement in detecting dead zones,a method for identifying and measuring near-end faults in transmission lines based on the projection features of the waveform core subdomain is proposed.Firstly,the wave processes of near-end and non-near-end faults are analyzed.It is found that there is a core subdomain composed of a calculation subdomain and an identification subdomain in the fault traveling wave,and there is a significant difference in the existence of the wave head between near-end and non-near-end faults in the identification subdomain.Then,the range of the core subdomain is determined by Radon projection,and the existence of the wave head is examined by the variance of the projection value in the identification subdomain,thus achieving the identification of near-end faults.Finally,the waveform mutation position sequence is preliminarily extracted by Radon variable angle projection,and the additional oscillation is eliminated based on the periodic reflection characteristics of the fault point reflection wave,thus achieving the measurement of near-end faults.The proposed method proposes the existence of the core subdomain from the perspective of wave processes.A large number of actual and simulated data tests show that the method based on the projection features of the core subdomain can reliably identify near-end faults and calculate the fault distance,providing a new idea for improving the reliability and effectiveness of single-end traveling wave measurement.Extensive testing and simulation data have shown that the single-ended traveling wave identification method based on waveform angle projection and the near-end fault identification method based on waveform core discriminant projection feature are effective,reliable,and intuitive,with a broad range of applications.They can effectively achieve waveform detection,fault location,and near-end fault identification.