| 摘要 |
PURPOSE:To surely identify overcurrent by recognizing that a trolley passes through an air section on the criteria of the sum of momentary variation ratios of respective one feeder current and opposite one and a ratio at which the opposite feeder current varies with time. CONSTITUTION:When feeders 21 and 22 which directly run from a bus and are separated at an air section 2A via respective breakers 1A and 1B are electrified, voltages of currents i1 and i2 which flow from the bus through the feeders 2a and 22 are detected by shunt resistances 4A and 4B, respectively. Those detection signals are fed through ampere detection circuits 15A and 15B into an arithmetic digital relay 12 at the ground site. On the criteria of the ampere detection signals i1 and i2, a dicision tree which contains a digital relay 12 (or analog relay) recognizes that a trolley passes through the air section. Based on the recognition, detecting sensitivity is refixed low in comparison with normal level, whereby flowing current may be surely identified. |
