| 摘要 |
<p>The device has a processing unit (12) including an analyzing unit providing signals (H1) representing fundamental frequency of current and providing signals (H2) representing a second harmonic of current. A retaining unit (16) blocks detection of earth fault when a rate of the second-harmonic is reached. Detectors (17, 17A, 17B, 17C) detect single-phase current having the individual second harmonic rate greater than high threshold for enabling detection of earth fault and/or blocking actions of the retaining unit. An independent claim is also included for a method for earth-fault protection of a three-phase electrical apparatus.</p> |
