The relay protection test set adopts microcomputer technology, consisting of a microcontroller, logic control unit, AC/DC current and voltage output unit, high-precision data acquisition unit, LCD display, real-time clock, printer, etc. It features high measurement accuracy and good repeatability. The instrument also has the advantages of beautiful appearance, reliable performance, simple operation, and complete functions, making it an ideal testing instrument for calibrating relay protection devices. It can test various AC/DC currents, voltages, phases, signals, reclosing, differential, and other individual relays as well as complete relay protection panels. It can test the pickup voltage (current) value, release voltage (current) value of various relays, and the pickup time and release time of various contacts (normally open, normally closed, changeover, time-delay), all automatically tested three times, automatically calculating the average of three measurements, and can print test results. With the main body unchanged, the weight is only 10 kg, using a stainless steel or plastic-aluminum case, which is beautiful, sturdy, and has good shock absorption performance. It uses a dual carbon brush voltage regulator (i.e., double-sided voltage regulator), with a large knob to adjust heavier AC/DC voltage and current loads, and a small knob to adjust lighter AC/DC voltage and current loads, allowing two outputs simultaneously. It uses a 0.5-class digital meter and high-precision sensors for measurement, and a six-digit electric stopwatch for time measurement, truly a good tool for relay protection personnel working in the field.