An improved time domain protection considering the effect of distributed capacitance for ground fault in renewable energy transmission line

After a fault occurs in the grid, the short-circuit current of renewable energy sources presents a weak feedthrough, and strongly controlled fault characteristic and also has a large number of interharmonics due to the influence of fault ride-through control strategies and inverter current limiting, which is different from the fault characteristics of traditional synchronous generators, resulting in the decline of the reliability of conventional frequency distance protection. Recently, time domain distance protection has received more attention because it is less affected by the fault characteristics of the renewable energy sources. However, when the transmission line connected to the renewable energy station is long, the influence of line distributed capacitance cannot be ignored, resulting in large deviations in fault distance calculation. To solve the above problem, this paper proposes an improved time domain distance protection scheme for a long-distance transmission line, taking into account the influence of line distributed capacitance. The solution is based on a π-type equivalence model of the line, which improves the accuracy of the fault distance solution and forms the protection criterion by modifying the fault circuit equations to take into account of the effect of distributed capacitance. Finally, the effectiveness and feasibility of the proposed time-domain distance protection scheme are verified by extensive simulations based on PSCAD/EMTDC.