Centralized coordination of load shedding and protection system of transmission lines

The power system integrity is vulnerable to thermal limit of transmission lines due to overloading and consequently activation of their protection devices following severe contingencies. In this paper, the loading rate of transmission lines is monitored online and is considered in the centralized load shedding to concentrate the control action on loads causing line loading rate violation to prevent cascading failure of lines. To this aim, the loads are ranked based on a criterion called Outage Sensitivity Index (OSI) considering the loading rate of line, the apparent power of the line prone to outage (event scale/severity), and the voltage magnitude. The load shedding as the available control action is localized to focus on the loads with higher OSI, ie, higher impact on the critical elements prone to outage. The efficiency of proposed approach is validated using severe contingency scenarios including cascading events leading to islanding situation performed in DigSilent Power Factory software on 39 bus IEEE standard test system.