Special protection scheme against voltage collapse

The safe and continuous operation of power systems necessitates the implementation of special protection schemes (SPSs) against severe disturbances that may lead to a system breakdown. This study proposes a new SPS to mitigate voltage collapse against predetermined contingencies that can significantly lessen the voltage stability margin (VSM) of the system. The proposed SPS is based on an effective load shedding scheme that uses a multi‐objective optimisation framework including the objectives of load cut, VSM and the integral of the deviation from nominal voltage. Moreover, a new diversely distributed multi‐objective fuzzy‐based theta gravitational search algorithm is proposed to solve the optimisation problem. Khorasan area of Iran's power system in 2014 peak load time is used as a test case for the suggested SPS. Effectiveness of the proposed approach is shown by comparing its simulation results with the results of the current SPS and other solution approaches.