Full use of modern advanced microelectronics technology and the implementation of a new type of device miniaturization of microcomputer relay protection tester. Microcomputer relay protection tester with a large screen LCD display and flexible and convenient rotating mouse controller. Stand-alone operation has a strong function, can carry out most of the tests, connected to the computer operation has a more powerful operation function. Small size, high accuracy.Not only has the large tester superior performance, advanced function, but also has the small tester compact and flexible,easy to operate, high reliability, performance and cost. lt is a good tool for the maintenance workers.