Abstract
The aim of this study is to introduce a tool to improve wide area power system stability. The proposed approach is called Statistical Standard Score ( SSS) technique, it is based on the empirical three sigma statistics rule. The proposed technique is used to predict and classify the system stability of the measured power angle value of each system area. The power system grid is previously classified into coherent areas; each angle measurement in area will represent its own stability limit. The proposed system has the features of minimizing the interruption area, increase system security against severe contingencies in the power system and maximize the performance of remedial control actions. These features will be achieved by giving the grid operator a list of the recommended actions that must be taken in wide area system to immune system instability. The PSSE software is used to simulate the IEEE 39 bus system to validate the suggested tool.