Extended reconfiguration of passive anti-islanding protections of RES stations in Greek distribution network

In Greece, with total renewable energy sources (RES) capacity exceeding 16 GW—around 8.5 GW of which is connected to the distribution network—the evolution of disturbances in the electrical system depends significantly on the response of RES stations connected to both the transmission and distribution networks, particularly their Fault-Ride-Through (FRT) capability. Serious disturbances, such as faults in the transmission network, on August 22, 2023, and February 15, 2024, resulted in the significant disconnection of RES stations primarily connected to the distribution network, with total power losses of 700 MW and 1,000 MW, respectively. This occurred despite most of these stations being equipped with FRT capability. The disconnections were mainly attributed to the sensitive settings of passive anti-islanding protections (over/under voltage and frequency) applied either on RES equipment (e.g. inverters) or on the Automatic Interconnection Switch (AIS) at the grid connection point, which compromised their FRT capability. Consequently, it was decided to check and reconfigure these protection settings for all photovoltaic and wind parks, which account for most of the RES capacity connected to the medium-voltage (MV) network. This project impacted nearly 7,500 stations across the country. The reconfiguration logic and the measures taken by HEDNO to complete this complex project within six months are detailed in this paper.