| 摘要 |
A direct current, high-speed circuit breaker which is connected in series at the direct current side of one of a plurality of inverters connected in parallel in a high voltage transmission system, and which is caused to open when the magnitude of the direct current to the one inverter exceeds a threshold value, is further controlled to open in response to the occurrence of a commutation failure only when such failure occurs simultaneously with reduction of the commutation voltage of the one inverter below a rated value by more than a first predetermined magnitude such that proper operation of the one inverter is no longer assured, and the threshold value of the direct current is increased from a normal value to a selected higher value in response to a reduction of the commutation voltage below the rated value by more than a second predetermined magnitude which is less than the first predetermined magnitude.
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