| 摘要 |
PURPOSE: To measure an earth current by measuring a zero phase current accurately by simple adjustment by adjusting and correcting the output of a current measuring system so that the vector synthesizing and adding result of respective line currents becomes a zero vector. CONSTITUTION: The measuring system of an optical sensor part 1 measuring the A-phase among three phases is set to a reference measuring system. When a current flows to a conductor, the lights from light emitting elements 12, 13, 14 are modulated and the current value signals detected by light detection elements 15, 16, 17 are respectively supplied to an adding part 28 through wavelength correcting amplifiers 18, 19, 20 and vector synthesis and addition is performed. The result of this vector synthesis and addition is supplied to a digital signal processor(DSP) 31 through a BPF 29 and an A/D converter. The outputs of other two current measuring systems other than the reference measuring system are adjusted and corrected so that the result of the vector synthesis and addition becomes a zero vector. An actual earth current is measured at a relatively short time interval after output adjusting and correcting processing. |
