University implements distribution automation to enhance system reliability and optimize operations

This paper describes the objectives and operating principles of a centralized distribution automation system (DAS) developed for the underground distribution system at Texas A&M University. The DAS detects electric faults based on information from fault indicators and automatically reconfigures the distribution system topology to isolate faulted sections and restore service to the maximum number of loads possible. It is a modular, scalable system that combines fast protection with flexible automation. The communications network is based on Ethernet rings conjoined in a ladder topology that allows reliable network operation. Rapid Spanning Tree Protocol (RSTP) in the managed network switches provides faster recovery and convergence after a topology change caused by link or device failure. The multi-ring/ladder network combined with RSTP provides the DAS with a loop-free, redundant communications path with minimum network downtime. A unique Internet Protocol (IP) address range and a virtual local area network (VLAN) were assigned to groups of equipment based on their geographical locations. Internet Protocol Security (IPsec) virtual private network (VPN) tunnels were established between network gateways to provide security through authentication and encryption.