| 摘要 |
PROBLEM TO BE SOLVED: To simplify a harmonic signal generating circuit, in other words, to meet both the requirements of the improved reliability of a controller and the improved precision of protection/control functions. SOLUTION: A digital protective controller has a harmonic signal generating circuit and inputs a harmonic signal to an analog input circuit to monitor the controller of its own automatically. The harmonic signal generating circuit 6 comprises an adder consisting of an operational amplifier Q1. A control signal consisting of a TTL signal designating the timing of the harmonic signal is inputted to one input terminal 11 of the adder and a negative reference voltage is inputted to the other input terminal 12. The time base parameter of the control signal is varied and the following characteristics of the harmonic signal which are extracted at that time are used as conditions for judging the detection unnecessary. |
