OVER THE PAST TWO DECADES, smart grid-related initiatives have directed our gaze toward customers and the edge of the system. Intelligent equipment and processes now pervade the electric system. They are dramatically affecting electricity customer investments in smart equipment. Initiatives are underway to reimagine distribution system operations. And this trend is not stopping. While committed to developing issues on a diverse set of themes that cover the power and energy industry landscape,

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... eping our readers abreast of the latest developments in integrating and coordinating the operation of customer and distribution system resources continues. The microgrid concept represents a collection of ideas for organizing operating principles and imagining new ways for customer-managed systems to integrate with the distribution system. The ideas recognize a boundary of responsibility between the utility electric power system and a collection of resources managed by the customer (or a surrogate). While people continue to debate the definition of a microgrid, it usually involves an integrated set of power-producing and powerconsuming resources. With full capability, a microgrid can either run independent of the regional power system (island mode) or run synchronously with the power system (connected mode), and smoothly transition between these two modes. The elegance of the concept lies with agreements on codes and standards of operation that ensure safe, coordinated operation that designers can replicate in a variety of situations. These agreements recognize the different parties responsible for operations on either side of the interconnection. While technical approaches to achieve this coordination have been well demonstrated, there still are areas where experience and socialization of ideas need to mature. In response to power system disturbances, safety is job one. Minimizing impacts to electric service follows close behind. Whether faults occur in the microgrid or regional power system, ensuring the protection schemes on either side of the interconnection respond properly is critical to safely clear these disruptions and minimize service interruptions. In This Issue A motivating factor for the microgrid concept is to improve resiliency for withstanding high-impact, low-probability events. To do this, microgrids use operational mechanisms that support the reliable operation of the microgrid footprint as well as the electric grid infrastructure. The integration of a large amount of distributed solar power and battery energy storage systems is accelerating microgrid technology development. This breakthrough technology aims to transform microgrid islanding operation from a tentative, emergency option used during system faults into a general solution for improving grid reliability and resiliency in both normal and abnormal situations. By smoothly switching between grid-connected and grid-disconnected modes, microgrids can supply loads and support grid services as needed. One of the major hurdles for interconnecting microgrids into the electric system is the effective integration of microgrid protection systems with the electric