Reliability Assessment of EAST Poloidal Field Power Supply System with Piecewise Failure Rate

The poloidal field power supply (PFPS) system plays an important role on the functions and safety of the Experimental Advanced Superconducting Tokamak (EAST). Its reliability assessment is important to ensure the success and efficiency of the physical experiment. When the disturbance during the operation period is considered, the failure rates of the components are not constant. The traditional frequency & duration method and the fault tree analysis are not suitable. In this paper, the state space (SS) model of the PFPS system is built by dividing it into seven subsystems to build their models respectively and then aggregating and combining these models. The piecewise failure rate is proposed by considering the operational and nonoperational conditions and utilized to the thyristors. The semi-Markov process is applied to calculate the reliability. The aggregation algorithm for the series system with the piecewise failure rate is newly derived. Numerical results show that, the reliability indices are all piecewise when the piecewise failure rate is utilized. The calculated reliability indices with the nonoperational failure rates are all higher than those with the operational ones, no matter steady or instantaneous.