The DDSU666 Single-phase electronic type guide rail mounting electric energy meters. It is used to monitor and display the grid power (voltage, current frequency and energy), and transfer this info to solar inverter via RS485 communication in zero-export system. The DTSU666 series three phase four wire electronic energy meter (din-rail) is designed based on power monitoring and energy metering demands for PV power plants etc. Mainly applied into the measurement and display for the grid parameters in the zero-export system, including grid voltage, current, active power, reactive power, frequency, etc.