Automated Protection Security Assessment of Main and Backup Protection for Distribution Networks

This paper demonstrates a case study on the 110kV distribution system of the German cities of Mainz and Wiesbaden using SIGUARD R PSA methodology [1], [2] for an automated system-wide protection security assessment (PSA). Selected findings are presented. An identified weak spot and a solution for that will be explained in detail.textbfSIGUARD R PSA is an automated and system-wide approach to simulate and assess the performance of a protection system integrated with a primary network. It enables an automated and structured fault placement. Furthermore, the protection system is simulated and assessed automatically. Protection system responses are rated and visualized. In this way, weak spots of the protection system in response to various combinations of contingencies, network configurations, and operation conditions are detected. This method can also identify limitations of protection concepts and setting guidelines. Highly aggregated results with a user friendly visualization provide a system-wide quick overview of protection system to network operators. Network planners can begin with this highly aggregated view and dive to detailed simulation results to identify the root-cause of identified weakpoints in a protection system.For the assessment of main protection system performance a 3-phase short-circuit fault was placed automatically along all distribution lines in this case study. Other fault types and considering a non-zero fault resistance were also possible. In addition to the possibility of checking the protection behavior during operation, this method also allows optimizing the installation of new protection equipment. Hereby the technical needs as well as the economical relevance can be investigated.The assessment of remote backup protections has fault placement and assessment method same as explained for the main protection assessment. Additionally, it considers that individual breakers near to each fault location fail to trip. This is a challenging task due to the high number of possible malfunctions to be assessed. In this case study all combinations of 3-phase fault scenarios and malfunction scenarios were assessed to verify remote backup protection performance.