| 摘要 |
PROBLEM TO BE SOLVED: To provide a protective-relay monitoring device for surely detecting failures, even in a filter circuit. SOLUTION: A first monitoring signal at a cut-off frequency fa or a nearby frequency f1≈fa related to the characteristics of a low-cut high-pass filter included in an integrator 19, and a second monitoring signal at a cut-off frequency fb or nearby frequency f2≈fb related to the high-cut low-pass characteristics of an analog filter 5, are entered into a monitoring winding 18 of an input transformer 15. The factors for the frequencies f1 and f2 are extracted by a digital processing unit 12, and the digital processing unit 12 generates an apparatus abnormality signal, when a change of amplitude is exceeds a prescribed range. |
