The relay protection tester is a new type of intelligent testing instrument developed in the past ten years. The previous relay protection test tools were mainly composed of voltage regulators and phase shifters, which were bulky and bulky. The accuracy is not high and cannot meet the verification work of modern microcomputer relay protection.

Modern microcomputer relay protection testers can be divided into two forms. One is using the traditional OCL power amplifier, which is large in size and weighs about 25Kg. It is relatively bulky. The power amplifier tube works in the amplification area and takes a long time. It is easily damaged, has a narrow dynamic range and low accuracy. The other is to use switching power supply, and the power amplifier adopts digital power amplifier, which is small in size, light in weight and high in efficiency. It is the development direction of relay protection tester.