Coupling characteristic analysis and a fault Pole detection Scheme for single-circuit and double-circuit HVDC transmission lines

Abstract The mis-operation and protection issues associated with non-fault poles caused by electromagnetic coupling effects threaten the security and stability of HVDC power systems. Based on the distributed parameter model, the coupling characteristics of single-circuit HVDC transmission lines and double-circuit HVDC transmission lines are studied in this paper. The decoupling method of double-circuit HVDC transmission lines that are structurally unbalanced is discussed. Based on waveform and frequency characteristic analyses of electrical quantities considering coupling effects, a fault pole detection scheme is proposed. A rapid fault pole detection criterion is formulated based on the backward travelling wave, and an adaptive threshold selection method is proposed. A reliable fault pole detection criterion is formulated using the low-frequency component voltage, and a short-window fast-filtering method is proposed. The travelling wave-based fault pole detection method can be rapidly applied using only the electrical quantities of the protected line, and the sensitivity and reliability of the method are enhanced by using adaptive thresholds. Based on the frequency characteristics of the coupling effects, the fault pole detection method can be reliably applied using only the electrical quantities of the protected pole. Simulations demonstrate the feasibility and validity of the fault pole detection scheme.