The JNKJ series network power instruments are used for continuous monitoring and control of distribution systems. Capable of analyzing 2-31 harmonics, total harmonic distortion rate THD of phase/line voltage, total current wave distortion rate THDi, and three-phase voltage imbalance ε u. Unbalance of three-phase current ε I. It can measure various commonly used power parameters, active and reactive energy, demand, remote control, limit exceeding alarm, and has analog quantity transmission and output functions. And it also has the function of measuring 8 time periods and 4 rates by time. DO output can be used for over limit alarm or remote control. The threshold value of the alarm can be remotely controlled. Some data can be read out using the MODBUS protocol through the RS-48S communication port, and the switch input DI can be used to monitor the status of the switch. The HF series instruments combine high-precision electricity measurement, intelligent energy metering and management, and a simple human-machine interface.