Advanced Protection Concepts in Future Distribution Grids with a High Level of Distributed Generation

Abstract

The increasing penetration of photovoltaic (PV) generation in modern power systems raises critical questions about the effectiveness of traditional protection schemes. How does the location of PV generation influence fault current contributions and relay tripping times? What are the limitations of distance protection in systems with high PV penetration, and how can these be addressed? This thesis seeks to answer these questions by investigating overcurrent and distance protection in medium-voltage grids with distributed PV generation. Using the Cigre MS grid model in PowerFactory, various fault scenarios were simulated to evaluate the impacts of PV integration on protection coordination and relay operation.

The results reveal that upstream PV generation enhances fault current contributions and reduces relay tripping times, while downstream PV leads to delayed fault clearance, potentially compromising system stability. For distance protection, the inability to model accurate short-circuit contributions from grid-following inverters highlights significant challenges in adapting traditional schemes for renewable integration. The study emphasizes the need for advanced technologies such as phasor measurement units (PMUs) and robust communication infrastructures to enable adaptive protection schemes capable of addressing these limitations.

By exploring the limitations of current models and identifying key areas for improvement, this thesis provides a foundation for addressing protection challenges in renewableintegrated grids. Furthermore, it sets the stage for future research into grid-forming inverters, representing the next frontier in renewable energy integration and protection engineering.