**Preface to "Steady-State Operation, Disturbed Operation and Protection of Power Networks"**

With the ongoing energy transition, distributed energy resources (DERs) and new loads (e.g., electric vehicles, EVs) are emerging in modern power systems, which highly impacts the operation of the latter. Indeed, in addition to an increased uncertainty in power system management, DERs as well as EVs can significantly affect the power quality level and contribute in multiple manners to faulty currents. Many algorithms and tools have been developed in recent years to ensure the safe operation of the system while fostering the integration of renewable energy-based generation. Moreover, the current advances in artificial intelligence and computation resources offer new prospects for related research.

This Special Issue offers a wide panel of up-to-date research that aims to ensure the enhanced operation of the electricity system. The first three contributions investigate how artificial intelligence (both machine and reinforcement learning) and new local business models (e.g., renewable energy communities) can assist in an effective managemen<sup>t</sup> of modern distribution systems. In addition, it is essential to have an accurate knowledge of the network parameters when analyzing the stability and power quality of a power system. In this way, the network impedance versus frequency characteristic is a key element to monitor, involving a huge amount of data to be processed. Hence, the fourth paper of this Special Issue investigates how lossy compression techniques impact the network impedance determination. Finally, high voltage–direct current technologies are emerging candidates when electricity needs to be distributed over large distances. Consequently, modern interconnected power systems are becoming increasingly hybrid with both AC and DC subsystems. It is therefore of key importance to ensure the dynamic resilience of such hybrid systems in emergency situations through advanced control strategies. This topic is the central theme of the fifth contribution of this Special Issue.

Ultimately, the whole content of the Special Issue tackles research not only applied to the different voltage levels of power systems, but also focusing on different time scales (from steady-state disturbed operation to close-to-real-time stability matters), allowing one to have a good overview of the main research issues when dealing with the safe operation of modern power systems. Enjoy the reading!

> **Fran¸cois Vall´ee** *Editor*
