Phase control device
The present invention provides a phase control device applied to a three-phase circuit including a three-phase transformer and a three-phase breaker that turns on/off the transformer. The device suppresses an excitation rush current generated in the transformer. The device includes a controller that closes any one phase of the breaker as a closing first phase and subsequently closes the other phases, a determiner that determines the closing first phase based on residual magnetic fluxes of the respective phases in the transformer, a determiner that determines, based on a pre-arc characteristic and a closing time variation characteristic of the breaker, target closing phases and target closing times of the closing first phase and the other phases, a calculator that calculates a closing time of each phase of the breaker, and an operation time table that stores, as a median of the variation characteristic represented by a normal distribution, the calculated time.
1. A phase control device to be applied to a three-phase circuit comprising a three-phase transformer including star-connected primary windings having a grounded neutral point and delta-connected secondary or tertiary windings, and a three-phase breaker that allows the three-phase transformer to be turned on by a three-phase power supply and disconnected from the three-phase power supply, the phase control device suppressing an excitation rush current generated in the three-phase transformer when the three-phase breaker is turned on, the phase control device comprising:
a closing controller that outputs a closing control signal to the three-phase breaker to close any one of three phases of the three-phase breaker as a closing first phase earlier than the other phases and close the remaining two phases after the closing first phase is closed;
a closing-order determiner that determines the closing first phase on a basis of residual magnetic fluxes of the respective phases in the three-phase transformer;
a target-closing-phase/time determiner that determines, on a basis of a pre-arc characteristic and a closing time variation characteristic of the three-phase breaker, a target closing phase and target closing time of the closing first phase and target closing phases and target closing times of the remaining two phase, wherein the closing time variation characteristic of the three-phase breaker includes a closing time variation characteristic of the closing first phase and closing time variation characteristics of the remaining two phases;
a closing-time calculator that monitors the closing control signal to thereby detect a start timing at which the closing of an individual phase of the three phases starts, and monitors a current through the individual phase to thereby detect a completion timing at which the closing of the individual phase is complete, the closing-time calculator calculating a closing time of each of the three phases of the three-phase breaker, the closing time being a time from the start timing to the completion timing; and
a storage device including a table that stores an average of the closing time of each phase calculated by the closing-time calculator a plurality of times;
wherein the target-closing-phase/time determiner calculates, from the stored averaged calculated closing times, the closing time variation characteristic of the closing first phase and the closing time variation characteristics of the remaining two phases, and
wherein the target-closing-phase/time determiner uses the respective calculated closing time variation characteristics of the closing first phase and the remaining two phases to thereby determine the respective target closing times of the closing first phase and the remaining two phases.
2. The phase control device according to claim 1 , further comprising:
a closing-first-phase setter that sets, in accordance with an instruction from an outside source, any one of the three phases of the three-phase breaker as the closing first phase; and
an operation switch that selects the closing first phase determined by the closing-order determiner or the closing first phase set by the closing-first-phase setter and notifies the target-closing-phase/time determiner of the selected closing first phase, wherein
the target-closing-phase/time determiner determines the target closing phases and target closing times of the notified closing first phase and the remaining two phases.
3. The phase control device according to claim 2 , comprising a telegraphic-message receiver that receives a telegraphic message instructing update of the table, controls the closing-first-phase setter to set the closing first phase, and controls the operation switch to notify the target-closing-phase/time determiner of the closing first phase set by the closing-first-phase setter.