| 摘要 |
PURPOSE: A method is provided to prevent erroneous operation of a relay, by detecting, in a real time basis, the erroneous operation through the use of current of each phase sampled from a secondary side of a current transformer. CONSTITUTION: A method comprises a step(S10) of sampling secondary currents of a current transformer of each phase; a step(S20) of obtaining an image current by using secondary currents of each phase; and a step(S30,S40,S50) of judging whether each of the secondary currents of each phase is lower than a predetermined threshold value, and judging that only the phase lower than the threshold value is opened, if one of the secondary currents of each phase is lower than the threshold value and the differences between the absolute values of the secondary currents of the other phases and the absolute values of three times of the phase current are lower than the predetermined threshold value. |
