| 摘要 |
A distance-selective short-circuit monitoring device with a low response time (FIG. 3, FIG. 5) results from sequence detection of first and second monitoring signals (US1, US2) which are selectively allotted to the zero cross-overs of detection signals (Ud1-Ud4) which determine a polygonal triggering zone, the selective allocation being in accordance with the sign of the signal change rate, and by counting the alternations between first and second monitoring signals (US1, US2) within a predetermined monitoring interval (Tu), the duration of which corresponds at least approximately to a half-period of the mains frequency. |
