Enhancing Substation Protection Reliability Through Economical Redundancy Schemes

This paper proposes an economical scheme to provide redundancy for protection in digital power sub-transmission and distribution substations. The scheme is based on Ethernet communication networks and uses the International Electrotechnical Commission (IEC) standard 61850 sampled values (SV). This redundancy scheme develops a method for alternative sources of the SV measurements for feeder and bus relays. The objective is to use the same number of intelligent electronic devices (IEDs), also referred to as merging units (MUs), while improving the overall reliability of substation protection. The multisource-based proposed scheme does not require two sets of MUs for redundancy. Instead, each MU is used to back up an adjacent MU. For instance, in a substation using IEC 61850, the protection relay can automatically switch to another available SV stream without interrupting the protection function if an MU fails. This dynamic reconfiguration capability, which ensures the system’s adaptability to changing conditions, is particularly valuable in maintaining system reliability during equipment failures. It allows for real-time adaptation to changing conditions within the substation. The paper evaluates the reliability of the proposed scheme using fault tree analysis (FTA). For demonstration, commercially available MUs and relays are connected to the Real-Time Digital Simulator (RTDS) for hardware-in-the-loop testing.