Fast Differential Protection for HVDC Transmission Line Based on Current Control Compensation

As the backup protection of DC lines, the current differential protection will lose its function in the DC control transient process because of its small setting value and long delay. In this paper, the influence mechanism of DC control characteristics on fault current is studied, and the DC compensation considering DC control is further deduced to weaken the influence of DC control on differential current. A fast differential protection for high voltage direct current (HVDC) transmission line based on current control compensation is proposed. The results in PSCAD/EMTDC simulationshow that the proposed protection highlights the fault characteristics of differential current, has the characteristics of large setting value and fast operation, and can correctly identify the internal and external faults under various fault conditions. Compared with the traditional current differential protection, the proposed protection can quickly remove the fault in the DC control transient process without delay. Its operation time decreases with the increase of DC control compensation to differential current, which has a certain inverse time characteristic and can be used as a fast backup protection for HVDC lines. © 2021 Automation of Electric Power Systems Press.