This paper presents different contingency ranking and screening methods using linear sensitivity factors for the faster response of the system operators to estimate the post- contingency active power flow for all the system transmission lines. The study depends on the Powerworld simulator to investigate the single contingency scenario and rank the most critical lines using different formulas of performance indices. Then, by applying the multiple contingency scenarios using the bus outages, an investigation was performed using the complex power performance index to specify the critical system substations, that could happen because of any such missile attack on the critical substation or for any natural reasons such as earthquakes, hurricanes, floods, etc. Finally evaluate the critical buses voltage stability using PV and QV curves and assess the system stability under the highest PI contingences