| 摘要 |
PURPOSE:To perform digital processing which does not exert much influence upon variation in system frequency by obtaining a prescribed odd number of sampled values of the quantity of electricity or more and finding their sum of squares, and utilizing the mean value. CONSTITUTION:An even number of >=4 sampled values of the quantity of electricity of a system at intervals of time which is one-fourth as long as cycles for a rated frequency, and the mean value of the sum of squares of those sampled values is found. Namely, an AC input value (i) is passed through an analog filter 1 for a countermeasure to a return error and then sampled by a sample holding circuit 2 at prescribed cycles. Then, the obtained value is converted by an analog-digital converter 3 into a digital value, which is inputted to the input circuit 4 of a computer. Then, this digital information is used to perform arithmetic processing circuit 5, and the result is outputted through the output circuit 6. A control circuit 7 is a circuit for controlling respective circuits. |
