Faced with the network redundant problem when real-time ethernet for plant automation(EPA) standard is applied to smart substation, communication mechanism, failure detection and recovery mechanism of distributed redundancy protocol(DRP) are analyzed. Ring network module is studied and designed for treating link failure recovery of smart substation system. Making a comparison between media redundancy protocol(MRP) and parallel redundancy protocol(PRP), the test results show that the designed ring network module based on DRP can achieve less self-healing time when link failure happens, and the requirements of link failure recovery time limit in smart substation based on real-time EPA are met.