Abstract: The paper deals with probability analysis to estimate of reliability level for therepairable system and expected time to failure and time that required to repairing the system. The study applied on thepart of 400 KV super grid power systemto find a weak point in the network.Using numerical techniques to calculate the reliability indexes in qualitative analysisPath Tracing Method (PTM) which analyze the complex network to give minimum cut sets and quantitative analysis Fussell algorithm thatgives over predict characteristic for the failureprobabilityby using MATLAB program. Then submitting suggestions and solutions to improve the power system in theplanning stage to investments of energy as a cost and reduce a losses energy so obtain network more stable and reliable. Results can show the zones have low-reliability and discuss the factors cause to it and their importance to ensure exploits the energy between regions and stability whole a power system.

Keywords: Failure Probability, Reliability Analysis, PTM Techniques, Fussell Model.