【正文】 nt microputer phase voltage pensation type direction high frequency protection, Xi39。an Jiaotong University and Xuchang relay factory cooperation development positive sequence breakdown ponent direction high frequency protection also one after another in 1993, in 1996 through appraisal. Hence, the different principle, the different type39。s microputer line and the main equipment protect unique, provided one group of new generation performance for the electrical power system to be fine, the function was plete, operation reliable relay protection installment. Along with the microputer protective device39。s research, in microputer aspects and so on protection software, algorithm has also made many theory progresses. May say that started our country relay protection technology from the 90s to enter the time which the microputer protected. 二 、 future development of Relay protection The future trend of relay protection technology is to puterization, working is intelligent, protect, control, measure and data munication developing by integration. The principles of protection of electric power circuits are quite independent of the relay designs which may be applied. For example, if the current to an electric circuit or a machine is greater than that which can be tolerated, it is necessary to take remedial action. The device for recognizing the condition and initiating corrective measures would be termed as an overcurrent relay regardless of the mechanists by which the function would be acplished. Because the functions of electromechanical devices are easily described, their performance wills ever as a basis for presenting a description of relays and relay systems in must have the following characteristics: ReliabilityThe nature of the problem is that the relay may be idle for periods extending into years and then be required to operate with fast responds, as intended, the first time. The penalty for failure to operate properly may run into millions of dollars. SelectivityThe relay must not respond to abnormal, but harmless, system conditions such as switching transients or sudden changes in load. SensitivityThe relay must not fail to operate, even in borderline situations, when operation was planned. SpeedThe relay should make the decision to act as close to instantaneously as possible. If intentional time delay is available, it should be predictable and precisely adjustable. InstantaneousThe term means no intentional time delay. There are several possible ways to classify relays: by function, by construction, by application. Relays are one of two basic types of construction: electromagic or solidstate. The electromagic type relies on the development of electromagic forces on movable members, which provide switching action by physically opening or closing sets of contacts. The solid state variety provides switching action with no physical motion by changing the state of serially connected solid state ponent from no conducting to conducting(or vice versa). Electromagic relays are older and more widely used。 solid state relays are more versatile, potentially more reliable, and fast. 1） Computerization With swift and violent development of puter hardware, puter protect hardware develop constantly even. The power system is improving to the demand that the puter protects constantly, besides basic function protected, should with trouble information of the large capacity and data the longterm parking space also, fast data processing function, strong munication capacity, work in order to share the whole system data , information , ability , work of resource with other protection , control device , dispatcher, highlevel language programming ,etc.. This requires puter protector to have function which is equivalent to a pc machine. In puter is it develop initial stage to protect, is it make with one mini relay protection install to imagine. Because the smallscale anism was accumulated greatly, with high costs at that time, dependability was bad, this imagined it was unrealistic . Now, exceed the miniputer of those years greatly with puter protector size similar worker function , speed , memory capacity of accusing of machine, so make with plete sets of worker person who accuse of opportunity of relay protection already ripe, this will be one of the developing direction that a puter is protected . Tianjin university is it spend whom transformation act as continue the electric protector with puter protector structure selfsame one worker person who accuse of to develop into already. The advantage of this kind of device is as follows, (1)it have functions of 486pc,it can meet to