This product is specially used for measuring the capacity of distribution power transformer measuring the no-load and short-circuit loss of transformer and has the function of harmonic analysis which is convenient for analyzing the quality of on-site power network. The device can automatically check whether the wiring is correct and display the vector diagram of the three-phase current and voltage when testing the three-phase transformer. At the same time necessary correction (such as waveform correction temperature correction unrated voltage correction calibration unrated current correction) is introduced to make the test results more accurate.