Case Study: A Subtransmission-Level Fault Location, Isolation, and Service Restoration (flisr) Scheme

Fault location, isolation, and service restoration (FLISR) techniques can efficiently improve reliability levels by rapidly identifying and responding to events in the system. As soon as a fault occurs and protective actions are exhausted, FLISR uses field device measurements and the network topology, in a centralized or distributed arrangement, to properly locate the fault. Through switching maneuvers, the damage is isolated and the network is reconfigured to restore (entirely or partially) the remainder of the system that is still de-energized. As an automatic solution, all the relevant decisions and actions must be achieved within minutes and should not depend on any operator’s interference. Additionally, FLISR must also be capable of performing a return-to-normal operation whenever the damage is repaired, a feature that reduces the need for operators’ reconfiguration planning. FLISR was designed for networks with meshed topology but that operate in radial configuration. However, FLISR has been primarily applied, but not limited, to distribution systems. This paper presents how Huntsville Utilities has been developing and implementing a project for Redstone Arsenal, in which FLISR is being applied to a 46 kV subtransmission system, with the aim of fast outage detection, isolation, restoration, as well as return-to-normal capabilities. Even though the final state of the FLISR scheme is to be operated in an autonomous mode, Huntsville Utilities finds it beneficial to deploy the solution in steps that can enable testing and validation without compromising safety and reliability of the system. Based on that, the case study presented in the paper follows a phase-by-phase deployment approach, in which the FLISR scheme is developed, simulated, operated in advisory mode, operated in isolation mode, before finally being fully deployed and operated in autonomous mode. The paper details each of these phases and highlights the importance of performing them to securely achieve a subtransmission-level FLISR scheme. The perspectives, challenges, and solutions of companies are explored along with the technical discussion.