Microcomputer relay protection tester is a new type of intelligent testing instrument. The former relay protection testing tools are mainly composed of voltage regulator and phase shifter, which are bulky and have low accuracy, and can no longer meet the verification work of modern microcomputer relay protection. With the continuous development of science and technology, microcomputer relay protection has been widely used in line protection, main transformer differential protection, excitation control and other fields, and substation integrated automation has become the mainstream. Modern microcomputer relay protection tester can be divided into two forms. One is the traditional OCL power amplifier, which is huge and weighs about 25 kilograms. The power amplifier tube works in the amplification area, which is easy to be damaged after a long time, with narrow dynamic range and low precision. The other is switching power supply and digital power amplifier, which are small in size, light in weight and high in efficiency, and are the development direction of relay protection tester. It can manually or automatically test various types of relays, such as voltage, current, frequency, power, impedance, harmonic, differential, synchronization, etc., can simulate various fault types for distance, zero sequence protection device setting value verification and protection device whole group test, can automatically scan the braking curve of microcomputer, digital transformer and generator-transformer differential protection, and has GPS trigger function. Microcomputer relay protection test device is an important test tool to ensure the safe and reliable operation of power system. With the rapid development of computer technology, microelectronics technology and power electronics technology, it is an inevitable trend of technological progress to apply the latest technological achievements to continuously introduce new high-performance microcomputer relay protection testing devices. Relay protection test device is an important test tool to ensure the safe and reliable operation of power system. With the continuous expansion of the scale of modern power system, the reliability and efficiency of power system operation management are constantly improved, and the testing work of relay protection personnel becomes more frequent and complicated. With the rapid development of computer technology, microelectronics technology and power electronics technology, it is an inevitable trend of technological progress and the responsibility entrusted to us by the times to continuously introduce new high-performance relay protection testers by applying the latest technological achievements. The relay protection tester is a new type of miniaturized microcomputer relay protection tester, which is based on People's Republic of China (PRC)'s "Technical Specification for Relay Protection Microcomputer Testing Device" (DL/T 624 ── 1997) and China's electric power industry standard, and makes full use of modern advanced microelectronic technologies and devices. It adopts an advanced structure, which can run independently on a single machine or be connected with other computers. The host has built-in high-performance industrial computer and high-speed digital signal processor, true 16-bit DAC module, new modular high-fidelity power amplifier, TFT true color LCD screen and embedded microcomputer keyboard. It can be operated independently by a single machine or connected to a laptop. Powerful operation function, small size and high precision. It not only has the superior performance and advanced functions of large-scale tester, but also has the advantages of small and flexible tester, simple operation and high reliability.