| 摘要 |
PROBLEM TO BE SOLVED: To improve detection sensitivity without delaying detection time. SOLUTION: For the monitoring of an analog input circuit 2 using the output obtained by making inputs with a prescribed monitoring signal superimposed on the quantity of electricity of a system, an adder 71 is provided which extracts the monitoring signal for a three-phase sum without doing the quantity of electricity separately, so that a ratio of the monitoring signal to the higher harmonics of the system is equal to or higher than for a conventional system in the quantity of electricity of the system such as current and voltage and the detection sensitivity can be improved without the need of an additional means like a delay circuit. |
