BLACKOUT IN THE ELECTRICAL GRID CAUSED BY FLUCTUATIONS OF RENEWABLE ENERGY –CASE STUDY

Abstract

The rapid integration of renewable energy sources into modern electrical power systems has created new operational challenges for transmission system operators worldwide. Renewable energy sources such as solar and wind power are inherently intermittent and weather-dependent, causing fluctuations in power generation that can significantly affect grid stability. In weak or developing transmission systems, sudden variations in renewable energy production may lead to voltage instability, frequency deviations, power oscillations, and ultimately large- scale blackout events. This paper investigates the impact of renewable energy fluctuations on the electrical grid of North Macedonia, with a particular focus on the role of the transmission system operator, MEPSO. The study analyzes the operational challenges faced by MEPSO during periods of high renewable energy penetration and examines the partial blackout event that occurred on 18 May 2025.The research evaluates the relationship between high photovoltaic generation, low system demand, overvoltage conditions, and transmission instability within the Macedonian power network. According to investigations conducted by ENTSO-E, unusually high voltages in the transmission system contributed to the separation of the 400 kV and 110 kV networks, resulting in the loss of approximately 79% of the country’s electrical load. The paper further discusses the technical limitations of traditional transmission infrastructure when integrating large quantities of variable renewable energy sources. Particular attention is given to insufficient reactive power compensation, lack of energy storage systems, reduced system inertia, and inadequate flexibility mechanisms. The study also reviews preventive measures adopted by MEPSO, including temporary disconnection of photovoltaic plants during periods of low demand and excessive solar generation.