Three-phase Digital Phase Voltmeter is a multifunctional, digital and intelligent instrument specially developed by our company for field testing. It has the characteristics of high accuracy, high stability, low power consumption and convenient to use etc. Under the condition of the tested circuit does not open-loop, it can measurement of three-phase AC voltage, current, phase between voltages, phase between current, phase between current and voltage, frequency, phase sequence, active power, reactive power, apparent power, power factor, current vector sum, judge transformer wiring group, sensibility and capacitive circuit, test the secondary circuit and differential bus protection system, read the phase relationship between differential protection between each groups CT, check watt hour meter wiring correctly or not, maintenance line equipment, etc., to provide a safe, accurate and convenient new power meter for electricity inspectors.