A new protection scheme for HVDC transmission lines based on discrete-domain Digital Filter modeling

To solve the problem of insufficient tolerance of fault resistance in transmission line protection under remote faults, a single-ended protection scheme for HVDC systems based on discrete domain Digital Filter model is proposed. Through detailed analysis of the frequency characteristics of internal and external faults, it can be concluded that the boundary of HVDC lines can cause differences in the characteristics between internal and external faults. Therefore, this paper analyzes the frequency domain characteristics of the DC boundary in detail, and introduces a new type of Digital Filter to extract the high-frequency component of transient voltage. The algorithm is simple, and it does not rely on time-frequency analysis methods to obtain the frequency component of fault traveling wave. The simulation results show that the scheme can reliably identify internal and external faults, has strong ability to withstand fault resistance, and has high sensitivity and selectivity.