Artificial Neural Networks (ANN) based Pattern Recognition for Steady State (SSA), Transient (TSA) and Dynamic security assessment (DSA) of the Power systems is presented. Conventional methods for Security Assessment take lot of time to assess the security of Power Systems when nil contingencies are considered. Artificial Neural Networks based Pattern Recognition is used to solve SSA, TSA and DSA and its effectiveness against conventional methods is presented. In addition Contingency Ranking and Generator severity ranking is used to measure the Severity of various Contingencies which allows an operator to take preventive control (generator rescheduling) or to be ready for corrective actions. Direct methods are fast compared to Numerical methods but proper choice of Lyapunov function is difficult. ANN based PR for SSA, TSA and DSA effectiveness is compared with other conventional methods like Pattern Recognition, which confirms that ANN not only gives accurate results but also is adaptive to the topology changes of the Power system. In addition Contingency Ranking and Generator severity ranking has been addressed which allows the operator to take preventive control actions like generator rescheduling. © 2005 IEEE.