The closed-loop operation mode and features of medium voltage distribution networks at home and abroad are described. With both reliability and economy considered

a net profit model for upgrading the distribution network from open-loop operation to closed-loop operation is developed

including a simplified evaluation model of system average interruption duration index (SAIDI) for a medium voltage cable feeder. The difficulties and applicable scopes of closed-loop operation are discussed. The study results show: i) further improvement of power supply reliability is impeded because of the existing power supply mode of closed-loop design and open-loop operation for domestic distribution networks; ii) for areas of developed economy

large load density

distributed generation and high reliability requirement

the closed-loop operation mode (mainly one of two feeders from the same bus) can be considered for use conditions permitting. Despite a higher cost for the power supply company owing to the use of the closed-loop operation mode

power supply reliability is improved while good social and economic benefits are ensured at the same time.