DETECTION CIRCUIT OF PT FOR SECONDARY VOLTAGE DISAPPEARANCE

摘要

PURPOSE:To simply detect the disappearance of the secondary voltage of a transformer for measuring instrument, by rectifying the output of the transformer for the measuring instrument and that of a current transformer to differentially compare both of them. CONSTITUTION:The secondary voltage of the transformer 4 for a measuring instrument connect to a main circuit 2 is rectified by a rectifying circuit 3 and the value differentiated through a voltage differentiation circuit 1 is inputted to a deviation comparing circuit 8. The secondary current of the current transformer 7 provided to the circuit 2 is inputted to a current differentiation circuit 5 through a reactance 6 and the rectifying circuit 3 and the value differentiated in the circuit 5 is inputted to the circuit 8. The voltage differential value from the circuit 1 and the current differential value from the circuit 5 are introduced into as comparator 11 and compared with the set value introduced into the comparator 1 from a setting device 9 to make it possible to detect the disappearance of the secondary voltage of the transformer 4.