Power System Operation Management Challenges Caused by High-Voltage in the South-Eastern European Region

Abstract One of the goals of Transmission system operators (TSOs) is to maintain the voltage profile of the transmission network within acceptable voltage ranges defined in Commission Regulation (EU) 2017/1485, which ensures safe and reliable operation of the transmission system. Following the successful completion of the SINCRO. GRID project in September 2022, the Slovenian (ELES) and Croatian transmission system operator (HOPS) have secured their own sources of reactive power for voltage regulation, in addition to the operating production units. During the SINCRO.GRID project planning phase, it was estimated that these devices would be sufficient to maintain the voltage profile within acceptable limits in the transmission network of both operators. However, a growing trend of high reactive power flows has been observed in European transmission networks connected to the south-eastern region, leading to overvoltage’s in the area. Due to the increasing number of incidents where transmission network voltages exceed acceptable levels, this issue has been given high priority within ENTSO-E. In this paper, we will analyse the voltage conditions in the Slovenian and Croatian transmission networks, identify the causes of excessive voltages, and present potential strategies to reduce the number of operating hours during which voltages remain too high.