The DL300 series power monitoring instrument is mainly used in the field of medium and low voltage substation and distribution system (6～35kV and 0.4kV) and industrial automation. It has powerful data acquisition and processing functions, and the measurement accuracy is better than 0.5. It can realize the functions of measurement and calculation of three-phase alternating current parameters, electrical measurement accumulation, switching value acquisition, 2 to 31 harmonics, SOE recording and other functions. DL300 series electric power monitoring instrument adopts liquid crystal display, which can display various electric parameters in real time. At the same time, through the RS485 interface, MODBUS communication protocol and the background computer monitoring system connection, real-time upload of various electrical parameters, forming a complete automated monitoring network.