| 摘要 |
<p>PROBLEM TO BE SOLVED: To eliminate the need for a communication line exclusive for transmitting power data by measuring a power value from the level of PT and CT being installed at a power line, modulating the transmission data of the power value, and then superposing it or inputting it to the power line via the PT. SOLUTION: Since the frequencies of a power line are low, namely 50 or 60 Hz, the signals of PT2 and CT3 are inputted to level converters 4 and 5 via low-pass filters 13 and 14. Then, the output of the level converter 4 is inputted to an A/D converter that is incorporated into a microcomputer 16. By multiplying the values of voltage and current being read by the A/D converter, an instantaneous power can be calculated. One period of the instantaneous power is averaged to measure a effective power value, which is transmitted to a modulation circuit 17 as a transmission signal. The transmission signal is modulated by a signal with a higher frequency (for example, 150 kHz) than a commercial frequency and is superposed on the power line via a clamp diode 18 for protection, a limiter resistor 19, and the PT2.</p> |
