**Preface to "Situation Awareness for Smart Distribution Systems"**

Smart distribution systems are the next-generation large-scale, interconnected electric power grids equipped with numerous widely distributed intelligent nodes. Their operations—ranging from power delivery to voltage regulation, fault response, outage management, and many others—are strongly affected by electricity users, and vice versa. As modern societies accelerate toward a future with massive electrification, the power distribution domain is also embracing a fast-changing landscape, with new systems and technologies for distributed generation, storage, consumption, sensing, control, control, protection, and optimization. Over the last decade, we have witnessed enormous opportunities, challenges, efforts, and progress toward an electrified future with smart distribution systems. Situation awareness, a term originating from military operations, is based on the inclusive view of the environment to provide comprehensive perception, comprehension, and prediction. Situation awareness in SDS transforms complex and intangible situation information into bases for making decisions through signal processing, data mining, knowledge engineering, and, more recently, artificial intelligence, which enables and/or empowers automated decision making in the next-generation power distribution systems.

While it is encouraging to witness extensive efforts in this field, situation awareness remains an emerging research direction for smart distribution systems, with many open yet important questions to answer in the future, making it a timely topic to focus on in this Special Issue. In this Special Issue, we present 10 recent studies on a wide range of topics in situation awareness for smart distribution systems.

**Integrated energy systems:** Efficient and accurate situation awareness is the key to the effective management of integrated energy systems. However, the traditional situation awareness of power systems cannot fully adapt to the strong nonlinearity and uncertainty. We are pleased to present four papers related to this topic in this Special Issue.

**Fault management:** The prognosis, diagnosis, and responses of faults also play an important role in smart distribution systems, which have recently attracted significant attention due to the need for a more resilient and reliable grid. We are pleased to present two papers on fault detection of generation systems and secondary equipment.

**Non-intrusive load monitoring:** As the last mile of the electric power infrastructure, smart distribution system operations critically rely on non-invasive load monitoring to understand the patterns of users' energy consumption in a privacy-preserved manner. We are pleased to present one paper related to this topic.

**Load forecasting:** Accurate prediction of load demand—considering diversified generation and consumption profiles in the distribution grid—is the basis of efficient, flexible, and reliable operations in smart distribution systems. We are pleased to present two papers on the latest load forecasting techniques in this special issue.

**Operation and maintenance:** Proactive operation and maintenance is an effective strategy to ensure non-disrupted power distribution and extend the lifecycle of power systems. Our Special Issue is pleased to conclude with a review of operation and maintenance for situation awareness in smart distribution systems.

> **Leijiao Ge, Jun Yan, Yonghui Sun, and Zhongguan Wang** *Editors*
