Automated control of residential area transmission system for enhancing the security of supply

Specificity of residential area transmission system is a highly meshed network with combined overhead and cable sections. In center of Zagreb town, control of transmission system is additionally complicated by a special operation of the 110 kV cable link between two power plants important for town's heat and electricity supply. Cable link has to be opened in order to control the power flows and to reduce short circuit current level. The consequence is a radial supply of two major substations in central Zagreb. The paper proposes an implementation of System Integrity Protection Scheme for automated control of Transmission System of central Zagreb. Proposed solution provides closed cable loop and possibility of island operating state of central Zagreb power system according to specific disturbances in bulk power system.