| 摘要 |
PROBLEM TO BE SOLVED: To provide a differential relay system for protecting transmission line, capable of performing countermeasure against excitation inrush current of a branch load, irrespective of a system condition, without damaging protection performance.SOLUTION: The system is provided with a self-end current measurement unit 200a measuring self-end current, a self-end current transmitting part 200b transmitting the measured self-end current to a counter end relay system and a counter end current receiving part 200c receiving a counter end current. A differential current generating part 201 obtains a difference between the self-end current and the counter end current. A content calculation unit 202 and a decision unit 203 are disposed as excitation inrush current decision elements 20. In the content calculation unit 202, a fundamental wave component included in differential current and a second harmonic component are extracted, and a content of the second harmonic component with respect to the fundamental wave component is calculated. The decision unit 203 determines whether the content is larger than a prescribed value or not. An output inhibiting part 204 sets an output inhibition signal based on decision results and inhibits output of a current differential relay element. |
