• Energy Research

The ground current of rail transit contains direct and harmonic components, which will lead to many undesirable effects on substation transformer neutral points. The traditional suppression strategy can only suppress the direct current in the ground current. At the same time, the traditional switching strategy does not consider the dynamic changes of the direct ground current and may cause the direct ground current at the surrounding neutral point to passively exceed the limit. Firstly, in this paper, the change of the direct and harmonic ground current and the influence of the rail transit passenger load on ground current were analyzed based on the measurement data. Then, considering the harmonic ground current of rail transit, a suppression strategy of harmonic ground current was designed. Besides, a calculation model for neutral point direct ground current distribution was established. Finally, an optimal switching strategy of the blocking device was presented to minimize the global direct ground current and maximize the economy of overall devices. Using the test case of 220kV substations surrounding an actual metro line, the ability of suppressing the harmonic ground current was verified. Compared with conventional switching strategy, the effectiveness and correctness of the optimal strategy for the direct ground current based on blocking devices were verified.

This paper summarizes the technical endeavors undertaken by the Task Force (TF) on Cyber-Physical Interdependence for Power System Operation and Control. The TF was established to investigate the cyber-physical interdependence of critical power system elements and their influence on the operation and control of energy systems. State-of-the-art analysis techniques, including co-simulation and digital twin technologies, are employed to address various layers of interdependence between cyber and physical systems, facilitating the identification of potential threats and vulnerabilities. The paper examines prospective trajectories for resilient cyber-physical systems and outlines the educational and workforce training imperatives for addressing cybersecurity threats in contemporary power systems. Furthermore, concluding remarks and future recommendations are provided to mitigate the inherent vulnerabilities within the extensively interoperable grid infrastructure.