The outage factors of components are divided into three kinds: 1）. protection break tripping when components are in abnormal operating conditions; 2）. random failures of components; 3） others such as external circumstances， artificial mal-operation and mal-tripping of protection components. The first two are related to operating conditions. The outage rate model for the first factor based on operating conditions is then established with respect to the time delay of relay protection. The outage rate model for the second factor is obtained from the relation of component’s failure rate to operating conditions. By taking into account all outage factors， the outage rate models of components based on the single operating and multi operating conditions are theoretically established， respectively. Moreover， the generator’s outage rate model based on the voltage and frequency is developed using the modeling method proposed. Evaluation results of IEEE RTS-79 show that the outage rate model can reflect the impact of operating conditions on the system’s real-time reliability.