MQ31 three-phase power quality analyzer, externally connected with open type Rogowski coil or voltage type CT, it can realize no dismantling wire test, simplify test steps, save construction cost, and is more convenient for engineering test as well as the inspection and maintenance of distribution system. MQ31 supports systems of single-phase and three-phase, it can measure multiple electrical parameters such as current, voltage, power factor, harmonic, active power, electric energy on the power grid of phase A, B, C and Neutral phase. With standard configuration of RJ45 interfaces (RS485 communication interfaces could be customized), through standard Modbus TCP (could be Modbus RTU protocol), it can be compatible with various configuration systems and transmit the electrical parameters collected by the front end to the system data center in real time.