Protecting the Future Electric Power Systems

直流电网是一种潜在效益显著的新兴电力系统。高压直流电网提高了大容量输电系统的可靠性和效率，也促进了大规模可再生发电系统的并网。中低压直流电网和直流微电网促进了分布式能源的整合。然而，尚未解决的保护问题限制了直流电网的利用。现有的保护系统(继电器)不能完全保护直流电网免受故障(短路)和干扰的不利影响。*拟议的研究计划的长期目标是通过开发高速、可靠、稳健和选择性的保护策略来确保直流电网在未来电力系统中的安全运行。在短期内，拟议的研究计划将解决高压直流电网和直流微电网的主要保护问题，如下所述。*1)高压直流电网保护*目前还没有商业上可用的技术用于网状高压直流电网中输电线路的故障保护。将制定一项保护战略，以便能够在高压直流电网中及时可靠地检测和定位故障线路(识别故障线路)。建议的保护策略将适用于具有不同配置、接地类型和换流技术的高压直流电网。此外，还将开发广域系统保护计划(SPS)，通过检测和抵消可能导致连锁停电的线路过载情况来保护高压直流电网的完整性。*2)直流微电网保护*现有的保护策略不能满足直流微电网应用的速度和可靠性要求。该研究计划将为直流微网馈线的高速、可靠的故障保护开发一种保护策略。此外，还将开发SPS，以保护直流微电网的完整性，使其免受电压崩溃的影响。在并网和孤岛运行模式下，SPS将能够及时采取补救措施，抵消可能导致电压崩溃的干扰。*拟议的研究计划将推动高压直流电网和直流微电网保护的最先进水平，从而：*1)导致保护这些直流电网免受故障和系统范围扰动的首批继电器的开发和商业化；*2)在包括加拿大在内的大国以更高的可靠性和效率促进大容量电力的远距离传输；*3)通过防止广泛的灾难性故障，如2003年加拿大和美国的停电，改善现代化电网的动态和稳定性；以及*4)增加可再生能源系统在加拿大配电系统中的渗透率。

Direct Current (DC) grids are emerging electric power systems with remarkable potential benefits. The High-Voltage DC (HVDC) grid improves reliability and efficiency of bulk power transmission systems and also facilitates grid integration of large-scale renewable generation systems. The medium-voltage and low-voltage DC grids and the DC microgrid facilitate integration of distributed energy resources. However, unresolved protection issues have constrained utilization of DC grids. The existing protection systems (relays) do not fully protect DC grids against adverse effects of faults (short-circuits) and disturbances.*** The long-term objective of the proposed research program is to ensure secure operation of DC grids in the future electric power systems by developing high-speed, reliable, robust, and selective protection strategies. In the short-term, the proposed research program will address the main protection issues of the HVDC grid and the DC microgrid, as explained below.***1) HVDC Grid Protection*** Currently there is no commercially available technology for fault protection of transmission lines in the meshed HVDC grid. A protection strategy will be developed to enable timely and reliable fault detection and location (identification of the faulted line) in the HVDC grid. The proposed protection strategy will be applicable to HVDC grids with different configurations, grounding types, and converter technologies. In addition, a wide-area System Protection Scheme (SPS) will be developed to protect integrity of the HVDC grid by detecting and counteracting line overloading conditions that can lead to cascading outages. ***2) DC Microgrid Protection*** The existing protection strategies do not meet the speed and reliability requirements for DC microgrid applications. The proposed research program will develop a protection strategy for high-speed and reliable fault protection of DC microgrid feeders. Besides, a SPS will be developed to protect integrity of the DC microgrid against voltage collapse. The SPS will be capable of taking timely remedial actions to counteract the disturbances that can lead to voltage collapse, under both grid-connected and islanded operation modes. *** *The proposed research program will advance the state-of-the-art in protection of the HVDC grid and the DC microgrid, and thereby:***1) lead to development and commercialization of the first relays to protect these DC grid against faults and system-wide disturbances;***2) facilitate long-distance transmission of bulk power with higher reliability and efficiency, in large countries including Canada; ***3) improve dynamics and stability of the modernized power grid by preventing widespread catastrophic failures, e.g., the blackout of 2003 in Canada and USA; and ***4) increase penetration of renewable energy systems into Canadian distribution systems.