Transmission Line Differential Protection Based on Numerical Solution of Partial Differential Equations

Current differential protection is a widely adopted and effective high-voltage AC transmission line protection scheme. The long distance of the transmission line determines that the distributed parameters and corresponding capacitive currents are not negligible. In fact, the physical laws of a distributed parameter transmission line can be expressed as a set of partial differential equations (PDEs). In this paper, a time-domain current differential protection method based on two-terminal electrical quantities and the PDE line model is proposed. The method does not depend on the power frequency phasors, can accurately compensate line capacitive current, and can effectively improve the protection speed and sensitivity. Numerical experiments validate the effectiveness and reliability of the proposed method. Additionally, the proposed method demonstrates satisfactory real-time performance under relatively low sampling rates (4k Hz).