The invention relates to a directional relay, which consists of a phase sequence detector, an automatic phase sequence corrector, a correction signal magnifier and an executing component. The directional relay is characterized in that the directional relay has the functions of automatic tracing and phase sequence choice. The invention can be combined with an AC contactor and a switch and so on and is suitable to a 380V three phase AC power user. After buying an assembled machine, the user needs not detecting the direction of an electric motor in idle running, which eliminates completely the trouble of turning wire terminal manually when the running direction of moveably electric appliance (such as a pump, an electric welding machine and a compressor, etc) is incorrect. The invention can assure the electric motor running in accord with the preset direction absolutely wherever so as to prevent reversion and guarantee reliable work of all equipment with strict requirement of phase sequence. |