Bergeron Model Based Phase Segregated Current Differential Protection Principle For Half-wavelength Transmission Lines

In recent years,our society and economy have developed rapidly,and demand for electricity is also growing.However,the distribution of energy resources in our country is extremely unbalanced,energy production centers and energy consumption centers are far apart,and the delivery scale gradually increased.The reversed distribution of energy centers and load centers has given rise to long-distance and large-capacity transmission technologies.Half-wavelength AC transmission technology is one of the long-distance and large-capacity transmission technologies.Due to its good transmission characteristics,it has gradually attracted the attention of domestic and foreign research institutes.Therefore,the research on half-wavelength AC transmission technology has the dual meaning of theory and practical application.However,the current-voltage characteristic of the half-wavelength line is different from that of the conventional transmission line,which will inevitably bring challenges to the protection principle and method based on the traditional transmission line.Therefore,a protection principle need to be customized according to the characteristics of the half-wavelength transmission line.This paper focuse on the principle of split phase current differential protection for half-wavelength transmission lines based on the Bergeron model.This paper first analyze the characteristics of the half-wavelength transmission line and its mathematical model,and study the applicable model of its protection—the single-phase and three-phase Bergeron model of transmission lines.The Bergeron model is introduced into the half-wavelength line to take into account the influence of the line distributed capacitance on the current differential protection.Based on the calculation method of the three-phase motion quantity based on the Bergeron model,the relationship between the three-phase motion quantity and the short-circuit current is deduced.For the short circuit near the midpoint of the half-wavelength transmission line,the difference between the action amount of the fault phase and the non-failure phase action is not obvious,and the calculation reference point is introduced.The analysis shows that when the calculated reference point and the short-circuit point coincide,the dynamic current of the fault has the largest difference and the non-faulted phase has the smallest dynamic current.A new method of phase-differential current differential protection for half-wavelength transmission lines based on the Bergeron model,using the constructed time difference method to protect the starting element to quickly estimate the approximate short-circuit point after a short-circuit fault at any half-wavelength line,and use this as the best calculation reference point.Using the Bergeron model,the electrical quantities on both sides after the short-circuit fault are reduced to the calculation reference point,and the three-phase action amount capable of accurately characterizing the short-circuit point current can be obtained,and the action amount of the fault phase and the non-fault phase can be effectively distinguished,and achieve the protection of the full-length range of half-wavelength transmission lines.Finally,the effectiveness of the proposed method is verified by a numerical example.The research results can provide a certain theoretical reference for the protection of the half-wavelength transmission from the perspective of relay protection.