The original power

network

and load structures will change as distribution facilities such as distributed resources

stochastic load and energy storage battery access to the distribution system. The operation method

flow level and direction of distribution network are complicated and changeable. Therefore

the protection principle and configuration scheme of traditional distribution network give a challenge. Consequently

the influences of distribution equipment penetration on distribution network are summarized

and the pros and cons of existing measures are reviewed. Meanwhile

the research direction and key of relaying protection under the new environment of active distribution network are described. Some problems that need solving are pointed out

and all those work provide references for the further research of distribution system protection.