| 摘要 |
<P>PROBLEM TO BE SOLVED: To stably perform protection operation by surely determining an overcurrent of an AC feeder cable. <P>SOLUTION: The AC feeder cable overcurrent protection device includes: A/D conversion means 21 which converts a current that flows in an AC feeder cable for supplying power to a train into a digital current; current addition means 22 which adds the digital current for a period of first predetermined time t1; average current calculating means 23 which calculates an average current of the first predetermined time t1 from an addition current, and repeatedly calculates the average current for the period of second predetermined time t2, to store it in a current storage means 24; likelihood average calculation means 25 to acquire an average current which takes the impedance change from current to past of the AC feeder cable into account, from the average current stored during the second predetermined time; overcurrent detection means 26 which detects that an overcurrent is flowing in the AC feeder cable when the likelihood average current is at a set value or higher; and trip output means 27 which receives a current detection signal and outputs a trip command to an AC circuit breaker. <P>COPYRIGHT: (C)2012,JPO&INPIT |
