A systematic and up-to-date approach for protection and control of the capacitive power compensation elements in the hellenic transmission network

The paper refers to the 250 MVAR capacitor arrangements being installed recently at the high voltage (150 kV) buses of several substations of the Greek (Hellenic) Transmission System. The applied capacitor configuration is exhibited and the principal technical parameters for the proper simulation of its operation are analyzed. The permissible tolerances of the capacitor withstanding against overcurrents and overvoltages, comprising the limit conditions for the determination of the setting of their protection relays, are cited, and the settings´ procedure is presented. Transient phenomena, which are important for the correct study and simulation of the capacitors, are analyzed, the appropriate closed form expressions are given and the application of computer aided calculation tools is described. Actual values for case studies are contributed. Design of devices used for the reduction of inrush currents is conducted. Finally, some suggestions concerning the application of modern flexible control and protection schemes for high voltage capacitors are contributed.