Development of line current differential relay over native Ethernet

Packet/frame-based communication services have been in general use for utility communications for a number of years with the exception of communications for protection and in particular line current differential protection. Recently, a number of utilities have begun to investigate the possibility of applying packet/frame-based communication supported by Ethernet Layer 2 (L2) for protection signaling between substations because of the high-speed performance, flexibility and maintainability it promises. However, tele-protection communications applications have been retained on legacy circuit-switched services such as PDH or SDH/SONET because of concerns with regard to jitter and channel asymmetry. Currently, dedicated multiplexers are provided for line current differential relays to utilise communication routes provided for power systems. If general communications services such as Ethernet can be applied to communication routes for protection purposes in the same way as for other power system communication services, then we can expect to reduce total system costs including that of the communication infrastructure. Therefore, we have developed a new line differential protection relay system using native Ethernet. In this paper, we will introduce the development specifications and evaluation test results.