| 摘要 |
PURPOSE:To improve the sensitivity and defect detecting accuracy regardless of balance and unbalance of load by calculating a different current between an absolute value of vector current resultant by combinations of respective two-phases among three-phase digital current data and the current data of the remaining one-phase and then by detecting a maximum different current and comparing to a judged value. CONSTITUTION:Among simultaneous series three-phase digital current data IR, IS and IT digital-converted with A-D conversion means 22, difference currents IA, IB and IC between absolute values of vector current resultants by respective two-phase combinations and the remaining one-phase current data are calculated by first to third difference current calculating means 23 to 25. Then, the maximum difference current IABCMAX is detected out of each difference current by maximum difference current detection means 26. Then, the maximum difference current IABCMAX is compared to defect detection judged value Ki by input defect judging means 27 for each phase. Then, if IABCMAX>Ki is valid, then error in connected polarity in an instrument transformer, disconnection, defective sampling data, etc., is detected by a state defect judging means 30. |
