A Dice similarity coefficient-based pilot protection method for 500kV transmission lines of large-scale integrated photovoltaic power supply.

• The quantitative expression of the current phase difference between both sides of the PV transmission line for faults with transition resistance is analyzed. • A Dice similarity coefficient-based pilot protection method for 500 kV transmission lines is proposed, considering the angle difference and magnitude difference between currents on both sides of the line. • The proposed method has a higher sensitivity than existing protection methods and performs better to transition resistance. • The effectiveness and accuracy of the proposed method under different fault locations, fault types, transition resistances, fault inception angles, line lengths, PV power supply capacities, have been verified by simulation and field data tests. Due to the shortage of fossil fuel resources and energy transformation efforts, the installed capacity of photovoltaic (PV) power supplies has been steadily increasing, resulting in the problem of low sensitivity for PV transmission line segregated-phase current ratio differential protection. Furthermore, there are increasing cases of large-scale gigawatt-level PV power supply integrated into the 500kV grid, bringing new challenges to the security and stability of the grid. In this paper, according to the fault characteristics of photovoltaic power supply, the current phase characteristics on both sides of the line are quantitatively analyzed during internal faults with transition resistance, and then the phase and amplitude differences of the currents on both sides of the line are used to propose a Dice similarity coefficient-based pilot protection method for photovoltaic transmission lines. PSCAD/EMTDC simulation and field data test results show the proposed method can accurately identify internal faults under the conditions of different fault locations, fault types, transition resistances, fault inception angles, line lengths, PV power supply capacity, and levels of noise. The method also performs well with CT saturation, simultaneous faults, evolving faults, and channel asymmetry. Additionally, the proposed method has a fast operation speed and a great performance to transition resistance. [ABSTRACT FROM AUTHOR]