Riding the Next Wave of Smart Grid Automation New Approaches to Fault Detection, Isolation

& Restoration

By Gary Ockwell, Chief Technology Officer Efacec Advanced Control Systems As the wave of AMI and smart meter deployments begins to crest, many utilities are poised to turn their attention to what is widely anticipated to be the next major focus area for Smart Grid projects - Distribution Automation. In particular, the automated isolation and restoration of distribution feeder faults is one application that can have significant impact on improving system reliability and quality of service, while laying the foundation for additional feeder optimization. After all, how valuable will the bevy of new intelligent power meters and home area networks be if the distribution system is unable to reliably and efficiently deliver quality power to the consumer? The good news is that there are now more options available when it comes to the implementation of automated feeder restoration systems - particularly solutions that use a model-driven scheme. This article will discuss some of the basics of this technology, and highlight some recent advancements that will give utilities more flexibility in its application.

Smart Grid App... Before Its Time

"Self-healing" feeder networks are typically implemented using two approaches - scripted (rules-based) and modeldriven. The model-driven approach is often referred to by various acronyms, including FDIR (Fault Detection, Isolation and Restoration) and FLISR (Fault Location, Isolation and Service Restoration) This automated detection of feeder faults and reconfiguration to restore power to un-faulted sections is a Distribution Automation application that has now been around for many years. It can be argued that FDIR (the acronym we'll use for this discussion) is a true Smart Grid application that was somewhat ahead of its time. While this level of unattended feeder reconfiguration was somewhat slow to gain traction in North America, some international utilities have embraced the technology early on with positive results. As early as 1998, the Taiwan Power Company implemented what is generally considered the first fully automated DA/DMS system, using FDIR on approximately 40 ElectricEnergy T&D MAGAZINE I january-February 2011 Issue 800 distribution feeders to cut typical service restoration times on un-faulted sections from 60 minutes down to only 20 seconds.

Increased Focus on Reliability &

Performance

Since the late 1990s, utility performance regulations (reward/ penalty structures) and increasing penetration of distributed energy resources and microgrids have increased pressure on utilities to respond efficiently to distribution faults and quickly restore power to as many customers as possible. The automated fault handling performed by FDIR provides many benefits to the utility and the customer that are well chronicled. These benefits include: * Shorter outage durations * Fewer sustained outages * Improved performance indices * Enhanced operational efficiencies * Improved service quality

Feeder Automation Approaches

Diverge; Goals Remain

Across North America, utilities have deployed many different solutions to achieve the fault isolation and restoration functionality. Some use distributed rules-based applications that rely on pre-determined topology and fault scenarios; others have more robust control-center configurations with a three-phase unbalanced load-flow model to enable additional feeder optimization functionality. Ultimately, all restoration technologies share the same core objectives; that is, to: * Accurately detect and locate feeder faults * Isolate the faulted portion(s) of the feeder * Restore power as quickly as possible (upstream and/or downstream of the faulted section). FDIR is traditionally deployed as an advanced system-level application running on the distribution management system (DMS) in the control center. In recent years, some other methods of applying feeder restoration technology have entered the marketplace. There are still essentially two basic types of self-healing feeder architectures in use - distributed and centralized.

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