Abstract: This paper studies the influence of the replacement of the disconnecting circuit-breaker for the bus-side disconnecting switch, the circuit-breaker and the line-side disconnecting switch on the power supply reliability. Taking a 110kV single bus with one incoming and four outgoing lines as an example And using the Poisson distribution to characterize the distribution of equipment faults, the reliability analysis model of the outgoing line based on the regular switch and the disconnecting circuit-breaker is established. The model takes into account the impact of bus withdrawal on the power supply reliability of the whole station, in which the model parameters are obtained from investigatigation. The model is used to analyze the total maintenance time of the outgoing line based on the regular switch and the disconnecting circuit-breaker respectively under different maintenance methods and different planned maintenance cycles. It is found that if the whole station is overhauled simultaneously, the power supply reliability of the outgoing line based on the disconnecting circuit-breaker is significantly better than that of the conventional switching. The reliability of power supply is not reduced due to the bus affected outage. The disconnecting circuit-breaker is worthy of being widely used.