Inrush-current suppressing device and inrush-current suppressing method

An inrush-current suppressing device, applied to a configuration of supplying and shutting off of outputs on a secondary side of a three-phase transformer via a three-phase circuit breaker, a three-phase alternating-current power supply being supplied to the secondary side of the three-phase transformer, for suppressing a magnetizing inrush current possibly generated in the three-phase transformer during actuation of the three-phase circuit breaker, the device comprising:

• a residual-magnetic-flux calculating unit that calculates a residual magnetic flux in a reference phase of the three-phase transformer while assuming a maximum magnetic flux level generated at a time of applying a rated voltage as 1 PU based on voltages generated at the secondary side of the three-phase transformer before and after opening the three-phase circuit breaker;
• a stationary-magnetic-flux calculating unit that calculates a stationary magnetic flux in the reference phase of the three-phase transformer with reference to the maximum magnetic flux level obtained as the 1 PU based on voltages on an output side of the three-phase circuit breaker by the outputs on the secondary side of the three-phase transformer, in response to a closing command to the three-phase circuit breaker;
• and
• a control unit that actuates a switch of the three-phase circuit breaker corresponding to the reference phase at a timing when the stationary magnetic flux in the reference phase calculated by the stationary-magnetic-flux calculating unit matches the residual magnetic flux in the reference phase calculated by the residual-magnetic-flux calculating unit, in response to the closing command.

An inrush-current suppressing device, applied to a configuration of supplying and shutting off a three-phase alternating-current power supply to and from a three-phase transformer via a three-phase circuit breaker, for suppressing a magnetizing inrush current possibly generated in the three-phase transformer during actuation of the three-phase circuit breaker, the device comprising:

• a residual-magnetic-flux calculating unit that calculates a residual magnetic flux in a reference phase of the three-phase transformer while assuming a maximum magnetic flux level generated at a time of applying a rated voltage as 1 PU based on voltages generated at a secondary side of the three-phase transformer before and after opening the three-phase circuit breaker;
• a stationary-magnetic-flux calculating unit that calculates a stationary magnetic flux in the reference phase of the three-phase transformer with reference to the maximum magnetic flux level obtained as the 1 PU based on voltages applied by the three-phase alternating-current power supply to the three-phase circuit breaker, in response to a closing command to the three-phase circuit breaker;
• and
• a control unit that actuates a switch of the three-phase circuit breaker corresponding to the reference phase at a timing when the stationary magnetic flux in the reference phase calculated by the stationary-magnetic-flux calculating unit matches the residual magnetic flux in the reference phase calculated by the residual-magnetic-flux calculating unit, in response to the closing command.

An inrush-current suppressing method, applied to a configuration of supplying and shutting off a three-phase alternating-current power supply to and from a three-phase transformer via a three-phase circuit breaker, for suppressing a magnetizing inrush current possibly generated in the three-phase transformer during actuation of the three-phase circuit breaker, the method comprising:

• a first-voltage measuring step of measuring voltages applied to the three-phase transformer;
• a residual-magnetic-flux calculating step of calculating a residual magnetic flux in a reference phase of a primary side of the three-phase transformer while assuming a maximum magnetic flux level generated at a time of applying a rated voltage as 1 PU based on a measurement result of the first-voltage measuring step before and after opening the three-phase circuit breaker;
• a second-voltage measuring step of measuring voltages applied to the three-phase circuit breaker by the three-phase alternating-current power supply;
• a stationary-magnetic-flux calculating step of calculating a stationary magnetic flux in the reference phase of the three-phase transformer with reference to the maximum magnetic flux level obtained as the 1 PU based on a measurement result of the second-voltage measuring step, in response to a closing command to the three-phase circuit breaker;
• and
• a circuit-breaker controlling step of actuating a switch of the three-phase circuit breaker corresponding to the reference phase at a timing when the stationary magnetic flux in the reference phase calculated at the stationary-magnetic-flux calculating step matches the residual magnetic flux in the reference phase calculated at the residual-magnetic-flux calculating step, in response to the closing command.

An inrush-current suppressing method, applied to a configuration of supplying and shutting off of outputs on a secondary side of a three-phase transformer via a three-phase circuit breaker, a three-phase alternating-current power supply being supplied to the secondary side of the three-phase transformer, for suppressing a magnetizing inrush current possibly generated in the three-phase transformer during actuation of the three-phase circuit breaker, the method comprising:

• a first-voltage measuring step of measuring voltages generated at the secondary side of the three-phase transformer before and after opening the three-phase circuit breaker;
• a residual-magnetic-flux calculating step of calculating a residual magnetic flux in a reference phase on the secondary side of the three-phase transformer while assuming a maximum magnetic flux level generated at a time of applying a rated voltage as 1 PU, based on a measurement result of the first-voltage measuring step before and after opening the three-phase circuit breaker;
• a second-voltage measuring step of measuring voltages on an output side of the three-phase circuit breaker by the outputs on the secondary side of the three-phase transformer;
• a stationary-magnetic-flux calculating step of calculating a stationary magnetic flux in the reference phase of the three-phase transformer with reference to the maximum magnetic flux level obtained as the 1 PU based on a measurement result of the second-voltage measuring step, in response to a closing command to the three-phase circuit breaker;
• and
• a circuit-breaker controlling step of actuating a switch of the three-phase circuit breaker corresponding to the reference phase at a timing when the stationary magnetic flux in the reference phase calculated at the stationary-magnetic-flux calculating step matches the residual magnetic flux in the reference phase calculated at the residual-magnetic-flux calculating step, in response to the closing command.

An inrush-current suppressing method, applied to a configuration of supplying and shutting off a three-phase alternating-current power supply to and from a three-phase transformer via a three-phase circuit breaker, for suppressing a magnetizing inrush current possibly generated in the three-phase transformer during actuation of the three-phase circuit breaker, the method comprising:

• a first-voltage measuring step of measuring voltages generated at a secondary side of the three-phase transformer before and after opening the three-phase circuit breaker;
• a residual-magnetic-flux calculating step of calculating a residual magnetic flux in a reference phase of the secondary side of the three-phase transformer while assuming a maximum magnetic flux level generated at a time of applying a rated voltage as 1 PU, based on a measurement result of the first-voltage measuring step before and after opening the three-phase circuit breaker;
• a second-voltage measuring step of measuring voltages applied by the three-phase alternating-current power supply to the three-phase circuit breaker;
• a stationary-magnetic-flux calculating step of calculating a stationary magnetic flux in the reference phase of the three-phase transformer with reference to the maximum magnetic flux level obtained as the 1 PU based on a measurement result of the second-voltage measuring step, in response to a closing command to the three-phase circuit breaker;
• and
• a circuit-breaker controlling step of actuating a switch of the three-phase circuit breaker corresponding to the reference phase at a timing when the stationary magnetic flux in the reference phase calculated at the stationary-magnetic-flux calculating step matches the residual magnetic flux in the reference phase calculated at the residual-magnetic-flux calculating step, in response to the closing command.