The switching devices in a distribution system can effectively improve the operational reliability of the system. The types of switching devices and their locations have great effects on the operational reliability of the distribution system. Given this background

the optimal placement strategy for switching devices is addressed taken the reliability indices into consideration. Firstly

the method of calculating the customers' failure time under different contingencies is proposed. Subsequently

an optimal placement model for switching devices is presented to minimize the sum of investment cost

the operation and maintenance cost

as well as interruption cost of customers considering two reliability indices within tolerable thresholds respectively. Secondly

the proposed model is transformed into a mixed integer linear programming model by linearizing the interruption cost function

and then solved efficiently by commercial solvers. Finally

the proposed method is tested with the IEEE RBTS-Bus 4 distribution power system and an actual medium voltage distribution network. Simulation results illustrate the basic characteristics of the presented model and solving method.