Cable Protection in HVDC Grids Employing Distributed Sensors and Proactive HVDC Breakers

Protection of HVDC grids against short circuits must act in the order of milliseconds to avoid damage to power electronic components and maintain a stable dc voltage. Therefore, ultra-fast protection algorithms are needed that detect the fault and identify its location. Recently developed communication-less HVDC grid protection algorithms provide high operation speed but are inherently limited in reach to provide selectivity. In this paper, a new method for protecting HVDC grids with long cables is proposed. The method combines protection algorithms, sensors integrated in the cable joints, and proactive hybrid breakers to achieve increased performance compared with the state-of-the-art without adding to the overall fault clearing time. This paper describes the proposed method, provides the theoretical basis for the algorithms, and presents the results of an in-depth analysis using electromagnetic transient (EMT)-type simulations. The simulations were performed in a detailed test system implemented in EMT-type software. Simulation results show that long cables can be protected along their entire length through a combination of the proposed algorithms, although the reach of the individual algorithms is limited.