| 摘要 |
PROBLEM TO BE SOLVED: To detect instantaneous drops in system voltage having harmonic contents, at a high speed with reliability, without detection delays. SOLUTION: System voltage waveforms are stored, and past waveform information is extracted to generate an ideal waveform Vo. The differential voltage Vx between the ideal waveform Vo and the system voltage Vs is integrated, only when it exceeds the Th1 level allowed in normal operation. This integration is carried out so that it is reset at the zero-cross point of the differential voltage Vx. When the integration value exceeds a preset detection level, instantaneous drop is detected. Thus, harmonic contents are removed beforehand, and integration is carried out without the use of filters. Even if there is phase shift in the system voltage, instantaneous drops can be detected with high reliability. COPYRIGHT: (C)2005,JPO&NCIPI
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