JP6713942B2 - Excitation current suppressor and power switchgear - Google Patents

Description

The present invention relates to an exciting inrush current suppressing device and an electric power switchgear for suppressing an exciting inrush current generated when a power source of a transformer is turned on.

In a power switchgear in which a three-phase power is turned on to a three-phase transformer, a three-phase circuit breaker for turning on and off the three-phase power is provided. In such a power switchgear, an exciting inrush current suppressing device that suppresses an exciting inrush current generated when a three-phase power source is turned on to a three-phase transformer may be used. One of the methods by which the exciting inrush current suppressing device suppresses the exciting inrush current is a phase control closing method in which the three-phase circuit breaker turns on the three-phase power at a specific phase of the three-phase power.

The exciting inrush current is likely to occur when the absolute value of the difference between the residual magnetic flux remaining in the iron core of the transformer when the three-phase power supply is cut off and the steady magnetic flux generated by the phase when the three-phase power supply is turned on is large. Therefore, the excitation inrush current suppressing device described in Patent Document 1 measures the terminal voltage of each phase that transiently changes when the three-phase power supply is cut off by the transformer voltage measuring means. The residual magnetic flux of the transformer's iron core is calculated by time-integrating the transiently changed voltage by the residual magnetic flux calculation means. The circuit breaker is controlled at the phase where the calculated residual magnetic flux and the steady magnetic flux match, and the three-phase power supply is turned on.

JP, 2013-62196, A

However, in the conventional phase control closing method, it is necessary to measure the terminal voltage of the transformer when the three-phase power supply is cut off.Therefore, when the voltage measuring device that measures the terminal voltage is not provided in the power switchgear, Has a problem that it is difficult to perform phase control.

The present invention has been made in view of the above, and an object of the present invention is to provide an exciting inrush current suppressing device that can perform phase control closing without measuring a terminal voltage.

In order to solve the above-mentioned problems and to achieve the object, the present invention provides a three-phase transformer when the three-phase power supply is opened, based on an exciting inrush current generated after the three-phase transformer is turned on. Residual magnetic flux calculating means for calculating the residual magnetic flux that is the magnetic flux remaining in the iron core of the container, and error calculating means for calculating the closing magnetic flux error that is the difference between the steady magnetic flux and the residual magnetic flux caused by the change in the phase of the three-phase power supply Target closed-pole phase calculating means for determining a target closed-pole phase, which is a phase for applying the three-phase power to the three-phase transformer based on the applied magnetic flux error, and control for turning on the three-phase power to the three-phase transformer at the target phase And means.

According to the exciting inrush current suppressing device of the present invention, there is an effect that the phase control can be performed without measuring the terminal voltage.

The figure which shows typically the electric power switchgear concerning Embodiment 1 of this invention. The figure which shows the relationship between the residual magnetic flux of the iron core of a three-phase transformer, and the magnetizing inrush current. The schematic diagram which shows schematic structure of the power switchgear concerning Embodiment 2 of this invention. Diagram showing the relationship between the opening phase and the residual magnetic flux Diagram showing the relationship between the opening phase and the residual magnetic flux

Hereinafter, an exciting inrush current suppressing device and a power switchgear according to an embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

Embodiment 1.
1 is a diagram schematically showing a power switchgear according to a first embodiment of the present invention. The power switchgear 50 includes a three-phase power supply 2, a three-phase circuit breaker 3, a three-phase transformer 1, a voltage measuring device 17, an instrument current transformer 21, and an exciting inrush current suppressing device 40. The excitation inrush current suppressing device 40 includes a residual magnetic flux calculating means 6, a closing magnetic flux error calculating means 8, a target closed pole phase calculating means 13, and a control means 15.

The three-phase power supply 2 generates respective power supply voltages ypa, ypb, ypc of the A-phase, B-phase and C-phase and outputs them to the contacts 3a, 3b, 3c of the three-phase circuit breaker 3, respectively. The contacts 3a, 3b, 3c of the three-phase circuit breaker 3 are connected to the three-phase transformer 1. The contacts 3a, 3b, 3c of the three-phase circuit breaker 3 are contacts that can be opened and closed. By closing the contacts 3a, 3b, 3c, the three-phase power supply 2 is turned on to the three-phase transformer 1. Further, the contacts 3a, 3b, 3c are opened, so that the three-phase power supply 2 to the three-phase transformer 1 is shut off. In the following description, closing the contacts 3a, 3b, 3c is also referred to as closing pole, and opening the contacts 3a, 3b, 3c is also referred to as opening pole.

The contacts 3a, 3b, 3c of the three-phase circuit breaker 3 are responsive to the opening control signal 20a and the closing control signal 20b from the control means 15 and are interlocked to substantially three simultaneously opening and closing. To be done. When the three-phase circuit breaker 3 is closed in response to the closing control signal 20b, the three-phase circuit breaker 3 outputs to the residual magnetic flux calculating means 6 a closing phase signal 4 indicating a closing phase which is a phase when the three-phase power supply 2 is turned on. To output.

The voltage measuring device 17 measures the ground voltage of the A phase, which is the reference phase, and outputs the power supply voltage signal 18 indicating the measurement result to the control means 15. The power switchgear 50 is provided with the voltage measuring device 17 for measuring the ground voltage of the A phase, which is the reference phase, but is not provided with the measuring device for measuring the ground voltage of the B phase and the C phase.

The measuring instrument current transformer 21 which is a current measuring device has measuring instrument current transformers 21a, 21b and 21c for measuring the currents of the respective phases. The instrument current transformer 21 measures the current flowing in each phase and outputs a main circuit current signal 5 indicating the measurement result to the residual magnetic flux calculation means 6. A secondary current transformer may be provided between the instrument current transformer 21 and the residual magnetic flux calculating means 6 so that the main circuit current signal 5 is output from the secondary current transformer.

The residual magnetic flux calculating means 6 calculates the residual magnetic flux remaining in the iron core of the three-phase transformer 1 before closing the pole based on the input main circuit current signal 5. This can be rephrased to calculate the residual magnetic flux remaining in the iron core of the three-phase transformer 1 at the previous opening. FIG. 2 is a diagram showing the relationship between the residual magnetic flux of the iron core of the three-phase transformer and the magnetizing inrush current.

When the turn-on time when the three-phase power supply 2 is turned on to the three-phase circuit breaker 3 is t ₀ , the generation time of the exciting inrush current generated immediately after that is t ₁ , the residual magnetic flux is Δφ, and the three-phase transformer 1 When the saturation magnetic flux threshold of the iron core is φ ₀ and the steady magnetic flux waveform which is the magnetic flux waveform on the power source side caused by the change in the phase of the three-phase power source 2 is φ(t), the elapsed time t after the three-phase power source 2 is turned on is t. The subsequent magnetic flux waveform Φ(t) is expressed by the following mathematical expression (1). The steady magnetic flux is a magnetic flux generated by a change in the phase of the three-phase power supply 2.
Φ(t)=φ(t)+Δφ−φ(t ₀ ) (1)

Here, the steady magnetic flux waveform φ(t) is represented by the following mathematical expression (2). The magnetic flux peak value was standardized as 1 PU.
φ(t)=sin(ωt) [ω=2πf (f: frequency)] (2)

When the iron core of the three-phase transformer 1 is saturated and an inrush current is generated at the generation time t ₁ ,
Φ(t ₁ )=Φ ₀ (3)
Becomes

The residual magnetic flux Δφ of the iron core of the three-phase transformer 1 is calculated by the following mathematical expression (4) using the mathematical expression (1), the mathematical expression (2), and the mathematical expression (3).
Δφ=φ ₀ −φ(t ₁ )+φ(t ₀ )
=φ ₀ −sin(ωt ₁ )+sin(ωt ₀ )(4)

That is, by grasping the closing time t ₀ and the generation time t ₁ , the residual magnetic flux in the open phase is obtained. After the relationship between the open pole phase and the residual magnetic flux is obtained, the residual flux Δφ of the iron core of the three-phase transformer 1 is calculated by the above formula (4) by performing the open pole control with the same open phase. It is estimated that In the first embodiment, the closed pole phase is basically a fixed value. Therefore, if the residual magnetic flux Δφ is calculated based on the above equation (4), it can be estimated that the residual magnetic flux Δφ having the same value remains in the iron core of the three-phase transformer 1 even after the subsequent opening of the pole. it can. The closing phase control is executed by setting the target phase based on the residual magnetic flux value calculated here.

The residual magnetic flux calculating means 6 grasps the generation time t ₁ based on the input main circuit current signal 5. Further, the residual magnetic flux calculation means 6 grasps the closing time t ₀ based on the input of the closing phase signal 4. The residual magnetic flux calculating means 6 outputs a residual magnetic flux signal 7 indicating the calculated residual magnetic flux to the closing magnetic flux error calculating means 8.

Here, the contacts 3a, 3b, 3c of the three-phase circuit breaker 3 have the same pre-arc characteristic and closing-pole time variation characteristic. In the following description, when the contacts 3a, 3b, 3c are not distinguished, they are simply referred to as contacts or three-phase circuit breaker 3. The contacts 3a, 3b, 3c of the three-phase circuit breaker 3 are closed in response to the input closing control signal 20b after the mechanical operation time has elapsed. The mechanical operation time from the input of the closing control signal 20b to the closing is called the closing time. The closing time depends on the ambient temperature of the three-phase circuit breaker 3, the operating oil pressure, the control voltage and the rest time. Further, it is known that the main circuit current starts to flow in the contact due to the preceding discharge before the closing. This preceding discharge is called pre-arc, the timing at which the main circuit current starts to flow is called input, and the pre-arc characteristic of the contact is called pre-arc characteristic.

Further, the contacts have mechanical operation variations, and when the closing control signal 20b is input, the probability distribution of the timing at which the contacts are actually closed is the closing control signal 20b input. The normal distribution fluctuates around the closed pole time corresponding to the timing. The characteristic of the variation in the closing time of the contact is the variation characteristic of the closing time. The contacts 3a, 3b, 3c have the same closing-pole time variation characteristics. Similarly, the contact opening times of the contacts 3a, 3b, 3c also have a variation characteristic, which is called an opening time variation characteristic.

The closing magnetic flux error calculating means 8 calculates the closing magnetic flux error for each phase based on the residual magnetic flux of each phase of the three-phase transformer 1, the pre-arc characteristic of the three-phase circuit breaker 3, and the closing time variation characteristic. To do. The closing magnetic flux error is the absolute value of the difference between the steady magnetic flux value and the residual magnetic flux value at the closing time t ₀ of the three-phase power supply 2. The closing flux error calculating means 8 outputs a closing flux error signal 12 indicating the calculated closing flux error to the target closed pole phase calculating means 13.

The target closed pole phase calculation means 13 determines the target closed pole phase based on the applied magnetic flux error. Since the stationary magnetic flux has a phase shift for each phase, the target closed pole phase may be determined so that the average value of the applied magnetic flux errors of each phase becomes the smallest. The target closed pole phase calculation means 13 outputs a target closed pole phase signal 14 indicating the target closed pole phase to the control means 15. Even if all the contacts 3a, 3b, 3c are controlled so as to be closed at substantially the same time, the B-phase and C-phase closing times are different from the A-phase closing time. It deviates by the amount of deviation of the time average value. The target closed-pole phase calculating means 13 may determine the target closed-pole phase in consideration of the deviation amount of the closing-pole time average value.

When an opening command 19a is input from a higher-order control device (not shown), the control means 15 sends an opening control signal 20a to the three-phase circuit breaker 3 so as to open the target opening phase which is a fixed value. To output.

When the closing command 19b is input from a higher-order control device (not shown), the control means 15 outputs the closing control signal 20b so as to close the target closing phase calculated by the target closing phase calculating means 13. Output to the three-phase circuit breaker 3.

Here, as shown in FIG. 2, when the magnetic flux in the iron core of the three-phase transformer 1 exceeds the saturation magnetic flux threshold value φ ₀ of the iron core after the turn-on time t ₀ of the three-phase power source 2, as shown in FIG. Occurs in. Magnetic flux waveform after on time t ₀ has a waveform obtained by adding the steady-state magnetic flux waveform absolute value of the difference between the steady-state magnetic flux o'clock residual magnetic flux and the input time t ₀ remaining in the core of the three-phase transformer 1. Therefore, when the difference between the residual magnetic flux remaining in the iron core of the three-phase transformer 1 and the steady magnetic flux at the closing time t ₀ , that is, when the closing magnetic flux error is large, the exciting inrush current is likely to occur. Therefore, by determining the target closed-pole phase so that the average value of the magnetic flux inrush current for each phase is minimized, it is possible to perform the phase control injection that suppresses the generation of the exciting inrush current.

In the first embodiment, the closing magnetic flux error is calculated based on the generation time t ₁ and the closing time t _{0 of} the exciting inrush current. That is, since the closing magnetic flux error is calculated based on the current value measured by the instrument current transformer 21, the phase control closing can be performed without measuring the terminal voltage. Therefore, it is not necessary to provide the power switchgear 50 with means for measuring the voltage in order to calculate the applied magnetic flux error. The power switchgear is generally equipped with a current transformer for measuring instruments. Therefore, even in the power switchgear which is not provided with the means for measuring the voltage, it is possible to suppress the generation of the exciting inrush current by performing the phase control by using the exciting inrush current suppressing device 40 described above. .. In particular, even in the case of the power switchgear in which it is difficult to add a means for measuring the voltage, it is possible to perform the phase control closing by using the exciting inrush current suppressor 40.

In the power switchgear 50 according to the first embodiment, the residual magnetic flux calculation means 6 calculates the residual magnetic flux based on the time t ₁ of the actually generated exciting inrush current. Therefore, the residual magnetic flux is not calculated in the power switchgear 50 that has never been turned on. That is, the residual magnetic flux is unknown when the power switchgear 50 is installed and the three-phase power source 2 is first turned on, that is, when the power is initially turned on. Therefore, the closing magnetic flux error calculating means 8 calculates the closing magnetic flux error assuming that the residual magnetic flux value is 0 at the initial closing. As a result, it becomes possible to perform phase control closing even at the time of initial closing.

Further, in the first embodiment, the residual magnetic flux is calculated based on the exciting inrush current generation time t ₁ and the closing time t ₀ to calculate the closing flux error. The residual magnetic flux may be calculated based on the time from the generation of the exciting inrush current to the convergence thereof, and the closing magnetic flux error may be calculated. If the duration of the exciting inrush current is Δt, the equation (4) for calculating the residual magnetic flux Δφ is represented by the following equation (5).
Δφ=φ ₀ −sin(tan ⁻¹ (sin ωΔt/(1-cos ωΔt)))+sin(ωt ₀ ) (5)

Embodiment 2.
FIG. 3 is a schematic diagram showing a schematic configuration of the power switchgear according to the second embodiment of the present invention. 4 and 5 are diagrams showing the relationship between the opening phase and the residual magnetic flux. It should be noted that the same components as those in the first embodiment are denoted by the same reference numerals and detailed description thereof will be omitted. Although the above-described first embodiment shows an example in which the opening phase is a fixed value, the power switchgear 51 according to the second embodiment includes the target opening phase setting unit 22 that corrects the target opening phase.

The residual magnetic flux signal 7 is input from the residual magnetic flux calculating means 6 to the target opening phase setting means 22. Further, the target opening phase setting means 22 receives the opening phase signal 23 indicating the opening phase from the three-phase circuit breaker 3. The target opening phase setting means 22 determines the opening phase and the residual magnetic flux as shown in FIGS. 4 and 5 from the residual magnetic flux value indicated by the residual magnetic flux signal 7 and the opening phase indicated by the opening phase signal 23. Data indicating the relationship of is generated for each phase.

As shown in FIGS. 4 and 5, when the control for opening the three-phase circuit breaker 3 at the target opening phase is performed, the phase that is actually opened varies due to the variation in the opening time. The target opening phase setting means 22 calculates, for each phase, a residual magnetic flux error which is a difference between the minimum value and the maximum value of the residual magnetic flux when the contacts are opened within the variation range. When the residual magnetic flux error exceeds the predetermined threshold value, the target opening phase setting unit 22 performs a correction to shift the opening phase and recalculates the residual magnetic flux error. When the residual magnetic flux error is within the threshold range, the opening phase is set as the target opening phase. The residual magnetic flux error is smaller when the three-phase circuit breaker is opened at the target opening phase shown in FIG. 5 than when the three-phase circuit breaker is opened at the target opening phase shown in FIG. ing. The target opening phase setting means 22 outputs a target opening phase signal 24 indicating the target opening phase to the control means 15. When the opening command 19a is input, the control means 15 outputs an opening control signal 20a to the three-phase circuit breaker 3 so as to open at the target opening phase.

A large residual magnetic flux error means that the difference between the residual magnetic flux calculated by the residual magnetic flux calculating means 6 and the actual residual magnetic flux is likely to be large when the opening magnetic phase is shifted within the range of the opening time variation. Means That is, when the three-phase circuit breaker 3 is closed at the target closing phase determined based on the residual magnetic flux calculated by the residual magnetic flux calculating means 6, the closing magnetic flux error becomes large and an exciting inrush current is generated. More likely.

In the second embodiment, the target opening phase setting means 22 can keep the residual magnetic flux error within the range of the threshold value, so that it is possible to suppress the occurrence of the exciting inrush current due to the opening time variation. it can.

In addition, in order to generate the data indicating the relationship between the opening phase and the residual magnetic flux, it is necessary to acquire the residual magnetic fluxes at a plurality of different opening phases. For example, it may be configured such that the opening phase is changed in advance to obtain the residual magnetic flux and the data indicating the relationship between the opening phase and the residual magnetic flux is generated. Further, when the residual magnetic flux error exceeds a preset threshold value, by performing control to shift the open phase, it is configured to accumulate data indicating the relationship between the open phase and the residual magnetic flux. May be.

In the first and second embodiments, a three-phase batch type three-phase circuit breaker that simultaneously turns on each phase of the three-phase power source 2 has been described as an example, but the turn-on order is changed for each phase. It may be a circuit breaker of each phase operation type. In the case of the circuit breaker of each phase operation type, the three-phase power supply 2 is first turned on in the phase in which the residual magnetic flux is larger than the other phases.

The configurations shown in the above embodiments show an example of the content of the present invention, and can be combined with other known techniques, and the configurations of the configurations are possible without departing from the gist of the present invention. It is also possible to omit or change parts.

1 three-phase transformer, 2 three-phase power supply, 3 three-phase circuit breaker, 3a, 3b, 3c contactor, 4 closing phase signal, 5 main circuit current signal, 6 residual flux calculation means, 7 residual flux signal, 8 closing flux Error calculating means, 12 applied magnetic flux error signal, 13 target closing phase calculating means, 14 target closing phase signal, 15 controlling means, 17 voltage measuring device, 18 power supply voltage signal, 19a opening command, 19b closing command, 20a Opening control signal, 20b Closing control signal, 21, 21a, 21b, 21c Current transformer for instrument, 22 Target opening phase setting means, 23 Opening phase signal, 24 Target opening phase signal, 40 Excitation inrush current suppression Equipment, 50,51 Power switchgear.

Claims (6)

Residual magnetic flux for calculating the residual magnetic flux, which is the magnetic flux remaining in the iron core of the three-phase transformer when the three-phase power source is opened, based on the magnetizing inrush current generated after the three-phase power source is turned on. Calculation means,
An error calculating unit that calculates a closing magnetic flux error that is a difference between the steady magnetic flux generated by the change in the phase of the three-phase power source and the residual magnetic flux,
Target closing phase calculating means for determining a target closing phase which is a phase for applying the three-phase power to the three-phase transformer based on the input magnetic flux error,
Control means for causing the three-phase transformer to turn on the three-phase power at the target closed-pole phase ,
The residual magnetic flux calculation means, the transformer inrush current suppression apparatus wherein the three-phase power supply and generating time magnetizing inrush current is generated is characterized that you calculate the residual magnetic flux based on the entered on time. The residual magnetic flux calculating means sets the residual magnetic flux to Δφ, the saturation magnetic flux threshold of the iron core of the three-phase transformer to φ ₀ , the closing time to t ₀ , and the generation time to t ₁ ,
Δφ=φ ₀ −sin(ωt ₁ )+sin(ωt ₀ )
The magnetizing inrush current suppressing device according to claim 1 , wherein the residual magnetic flux is calculated from the relationship Residual magnetic flux for calculating the residual magnetic flux, which is the magnetic flux remaining in the iron core of the three-phase transformer when the three-phase power source is opened, based on the inrush current generated after the three-phase power source is turned on. Calculation means,
An error calculating means for calculating a closing magnetic flux error which is a difference between the steady magnetic flux generated by the change in the phase of the three-phase power source and the residual magnetic flux,
Target closing phase calculating means for determining a target closing phase which is a phase for applying the three-phase power to the three-phase transformer based on the input magnetic flux error,
Control means for causing the three-phase transformer to turn on the three-phase power at the target closed-pole phase, the residual magnetic flux calculating means calculating the residual magnetic flux based on the duration of the excitation inrush current. excitation磁突input current suppressing device characterized. The residual magnetic flux, which is the difference between the residual magnetic flux and the residual magnetic flux that may occur during actual opening due to the variation in the opening time, based on the relationship between the open magnetic phase, which is the phase when the three-phase power source is open, and the residual magnetic flux. The excitation rush according to any one of claims 1 to 3 , further comprising target closing phase setting means for calculating an error and setting a target opening phase based on the residual magnetic flux error. Current suppression device. The magnetizing inrush current according to any one of claims 1 to 4 , wherein the target closed-pole phase calculating means determines the target closed-pole phase on the assumption that the residual magnetic flux is 0 at the initial closing. Suppressor. A three-phase transformer to which the three-phase power is turned on,
A three-phase circuit breaker for turning on and off the three-phase power source to the three-phase transformer,
A current measuring device for measuring the current to the three-phase transformer,
A magnetism inrush current suppressing device according to any one of claims 1 to 5 , and a power switchgear.

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