| 摘要 |
PURPOSE:To make it possible to judge a tidal current direction without being affected by the variation in the frequency of a power system, by performing predetermined operation by using current and voltage data which are obtained by sampling the current and voltage of the power system at 90 deg. intervals. CONSTITUTION:Three current data Ai, Ai-1, Ai-2 and three voltage data Bi, Bi-1, Bi-2, which are obtained by sampling the current and voltage of a power system at a predetermined sampling cycle and mutually continue, are respectively used to operate a sum xi=Ai+Bi and difference yi=Ai-Bi. When a judge formula xi-1<2>-xi.xi-2>yi-1<2>-y1.yi-2 is formed, it is judged that the current and the voltage are same phase relation. In this case, the predetermined sampling cycle is set by arbitrary sampling frequency selected so as to contain a 90 deg. phase position.
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