Improvements in Power System Integrity Protection Schemes

As the existing transmission system infrastructure is challenged to support loads beyond original design limits, the implementation of "wide area" Power System Protection Systems (PSPS) also called System Integrity Protection Schemes (SIPS) are often needed to maintain transmission system integrity. Such a system, with stringent performance and availability requirements, has been designed and installed in the UK (in 2008), and specifically on the Interconnection between Scottish Power and National Grid. The strategy to maintain transmission system integrity is based on the determination of circuit connectivity in the interconnection and, according to pre-defined criteria obtained from different system stability studies, to selectively issue a trip command to Scottish Power generating units in less than 20 ms. This paper starts by presenting the need for the PSPS and the resulting design requirements. It discusses afterwards the architecture that resulted from the requirements and the subsequent implementation and testing issues. Actual operation and performance results, including end-to-end timing tests, will be presented. The paper concludes with a discussion of desired improvements in the architecture and new solutions that are available through the Generic Object Oriented Substation Event (GOOSE), Virtual LAN (VLAN), and priority messaging technologies that are now available through the IEC 61850 communication standard. The following conclusions were found during the project execution at Scottish Power Real time control schemes will increasingly play a role in maintaining the security, stability, and integrity of the electric power network. Today\´s digital relays in close integration with advanced communication networks promise to provide solutions for remediation of identified power system problems.Implementation