Automatic Load Shedding Schemes against Voltage Instability in the Hellenic System

Based upon the experience gained from the 2004 blackout and the on-line voltage security assessment operation that is in service since 2005, the Hellenic transmission system operator (HTSO) decided to automate the process of load shedding in the Hellenic Interconnected System, in order to reduce the risk of voltage collapse in the event of critical contingencies. Analytical description of the design and implementation of two individual load shedding schemes in the Hellenic System is presented in this paper. Analysis and simulation results that investigate and validate the efficiency of these protection schemes are included in the paper.