FIELD: contact-free relay protection apparatuses for electric power plants. SUBSTANCE: apparatus has sensitive 1, time-setting 2 and actuating 3 devices. The apparatus is characterized by the use of threshold element 4, first 5 and second 6 delay elements, first 7 and second 8 AND gates, OR gate 9. The output of the latter is connected to the input of actuating device 1 and inputs are connected to the outputs of time-setting devices 2, first 7 and second 8 AND gates. The first input if first AND gate & is connected to the output of sensitive device 1 and second one is connected to the output of threshold element 4 and input of first delay element 5. The output of first delay elements 5 is connected to the RESET input of threshold element 4. The first input of second AND gate 8 is connected to the output of second delay element 6 the input of which is connected to the output of sensitive device 1 and the second input of second AND gate 8 is connected through communication line 10 (blocking one) to a lower-stage protection device. EFFECT: enhanced reliability. 1 dwg
