Residual current monitoring based on DeviceNet

Residual current protective devices play an important role in electrical safety engineering. Under normal conditions, it is discovered that there exists leakage current during power transmission and it can change dramatically due to insulation fault or electrical shocks. Possible reasons for leakage current in power system are analyzed. Efforts have been made to monitor such leakage current. A residual current relay based on DeviceNet fieldbus is designed. Its controller, drive circuit and DeviceNet interface are introduced. The relay is connected to Rockwell NetLinx network. Despite of its monitoring function on the filed, the measured values are transmitted to the monitor workstation for recording and analysis. The result shows its reliable communication and perfect performance.