The KFA300 handheld mini relay protection tester not only serves as a device for testing relay protection equipment but also functions as a high-precision three-phase standard source. Within the range of 1% to 100% of its capacity (4x300V, 4x10A), its output accuracy surpasses 0.05 class. Powered by batteries, it produces highly pure output signals with minimal harmonic distortion, making it suitable for calibration purposes of various single-phase or three-phase meters.