JP2002260476A - Three phase switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a three-phase switch which decreases exciting inrush current of a three-phase transformer. SOLUTION: It contains first - third terminal t1-t3 and switch S1-S3 connected in order to supply and break voltage to terminal t1-t3 of three-phase transformer 7 provided with U phase connected between the terminal t1 and t2, V phase connected between terminal t2 and t3, and W phase connected between terminal t1 and t3. It is a three-phase switch 100 connected to three-phase ac power supply 3, and in the condition provided with switch S1-S3, it breaks switch 2 after a first fixed time from break instruction after breaking switch 1 based on the breaking instruction of switch. It is provided with break control means which breaks switch S3 from break instruction after second fixed time, and switch control means which switches switch S1-S3 based on switch instruction of the switch. V phase of three-phase transformer delays for third fixed time than U phase or W phase and supplies three-phase ac power supply 3 to terminal t1-t3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a three-phase switch for turning on and off a transformer in a power supply, and more particularly to a three-phase switch for reducing an inrush current of a three-phase transformer.

[0002]

2. Description of the Related Art A substation to which a conventional three-phase switch is applied will be described with reference to FIG. In FIG. 4, the substation 1
Is connected to the three-phase AC power supply 3 and the switch S
A three-phase switch 7 for simultaneously turning on and off the first, S2, and S3, and a three-phase transformer 7 having terminals t1, t2, and t3 connected to the switches S1, S2, and S3, respectively. Consists of

In the substation having the above-described configuration, when the switches S1, S2, and S3 of the three-phase switch 5 are simultaneously turned on to apply the voltage of the three-phase AC power supply 3 to the three-phase transformer 7, It is known that an inrush current of several tens times the rated current flows, which varies depending on the residual magnetic flux of the phase transformer 7 and the like, and attenuates with time to become a steady state.

The maximum value _I0max of the excitation inrush current is applied when the instantaneous value of the power supply voltage is zero, and the direction of the residual magnetic flux in the iron core of the three-phase transformer 7 and the direction of the magnetic flux immediately after the _application of the voltage match. In this case, the maximum is obtained by the following equation. _{I 0max = K · (2B m} + B r -B S) ····· (1) Here, K: proportional constant, _{B m:} steady state flux density (T) _{B r:} residual magnetic flux density (T), B _S : Saturated magnetic flux density (T) Here, the saturated magnetic flux density B _S is generally about 2 Tesla, so the above equation (1) becomes the following equation. I _0max = K · (2B _m + B _r −2) (2) Since the exciting rush current causes a malfunction of the protection device, reduction measures are taken, and the exciting rush current is reduced. , said (2) steady-state magnetic flux density B _m from the _equation, there is a means for reducing the residual magnetic flux density B _r.

[0005]

However, when the steady-state magnetic flux density _Bm is reduced to, for example, half, the cross-sectional area of the core of the three-phase transformer 7 is doubled, and the coil wound around the outer periphery of the core, The tanks for storing coils etc. have also become larger,
There is a problem that the three-phase transformer 7 becomes large and it is difficult to obtain predetermined transformer characteristics.

In order to reduce the residual magnetic flux density Br,
A butt joint may be provided to the iron core of the three-phase transformer 7, but a large vibratory force acts on the gap of the joint to generate noise, and in order to withstand the vibratory force. However, there has been a problem that a three-phase transformer having an iron core tightening structure which is extremely stronger than that of a general transformer must be used.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and appropriately reduces the inrush current by exciting the so-called standard transformer into and out of the three-phase AC power supply. It is intended to provide a phase switch.

[0008]

The three-phase switch according to the first invention has first to third terminals and is connected between the first and second terminals. First
A first phase, a second phase connected between said second and third terminals, and a third phase transformer of a three-phase transformer comprising a third phase connected between said first and third terminals. A three-phase switch connected to a three-phase AC power supply, the switch having first to third switching units respectively connected to input and cut off voltage to and from the terminal, and In a state in which the opening / closing section is turned on, the first opening / closing section is shut off based on the shutoff command for the opening / closing section, and then the second opening / closing section is shut off after a first predetermined time from the shutoff command. Shut-off control means for shutting off the third opening / closing section after a second predetermined time from the shut-off command; and a second phase of the three-phase transformer being a third predetermined phase higher than the first phase or the third phase. The opening / closing section is turned on so that the three-phase AC power is supplied to the first to third terminals with a time delay. On the basis of the command is characterized in that and a input control means for turning on the third switching unit from the first. Here, the first predetermined time may be longer or shorter than the second predetermined time. According to such a three-phase switch, by shutting off the first switch before the second and third switches in a state where the three-phase transformer is excited, two of the three phases are turned off. After reducing the residual magnetic flux of the phase, the second switching unit and the third switching unit are shut off after a predetermined time, and the three-phase transformer is shut off from the three-phase AC power supply. When the three-phase transformer is excited, the second phase having a large residual magnetic flux is turned on by the opening / closing part with a delay of the third predetermined time from the first phase or the third phase, and all phases of the three-phase transformer are turned on. Apply voltage. Therefore, when the power is first turned on to one phase of the three-phase transformer in which the residual magnetic flux density is reduced, the exciting rush current is reduced, so that there is an effect that the exciting rush current can be reduced while using a general transformer. .

A three-phase switch according to a second aspect of the present invention has first to third switching parts connected to a three-phase transformer,
A three-phase switch connected to a three-phase AC power supply, wherein after the first to third switching units are turned on, the first switching unit is shut off based on a shutoff command for the switching unit. Shut-off control means for shutting off the second opening / closing section after a first predetermined time from the shut-off command and shutting off the third opening / closing section after a second predetermined time from the shut-off command;
After the first opening / closing section is closed based on the closing command, the second opening / closing section is closed after a third predetermined time from the generation of the closing command. And a closing control means for closing the third opening / closing section after a fourth predetermined time different from the predetermined time. Here, the third predetermined time is
It may be longer or shorter than the fourth predetermined time. According to such a three-phase switch, by shutting off the first switch before the second and third switch in a state where the three-phase transformer is excited, two of the three phases are turned off. After reducing the residual magnetic flux of the phase, the second switching unit and the third switching unit are shut off after a predetermined time to shut off the three-phase transformer from the three-phase AC power supply. When the three-phase transformer is excited, the first switching unit is first turned on, and then the second switching unit is turned on, for example, after a third predetermined time, so that the single phase of the three-phase AC power supply is reduced to one phase having a small residual magnetic flux. After applying the phase voltage, the third switch is turned on to apply a three-phase AC voltage to the three-phase transformer. Therefore, when the power is first turned on to one phase of the three-phase transformer in which the residual magnetic flux density is reduced, the exciting rush current is reduced, so that there is an effect that the exciting rush current can be reduced while using a general transformer. .

[0010] A three-phase switch according to a third aspect of the present invention has first to third switching parts connected to the three-phase transformer,
A three-phase switch connected to a three-phase AC power supply, wherein after the first to third switching units are turned on, the first switching unit is shut off based on a shutoff command for the switching unit. Shut-off control means for shutting off the second opening / closing section after a first predetermined time from the shut-off command and shutting off the third opening / closing section after a second predetermined time from the shut-off command;
After closing the first opening / closing section and the second or third opening / closing section based on the closing command of the opening / closing section, the third or the third or not opened after a third predetermined time from the generation of the closing command. And a closing control means for closing the second opening / closing section. According to such a three-phase switch,
When the three-phase transformer is energized, the second and third
Prior to the opening / closing section, after the first opening / closing section is shut off to reduce the residual magnetic flux of two phases of the three phases, the second opening / closing section and the third opening / closing section are moved after a predetermined time. Disconnect to disconnect the three-phase transformer from the three-phase AC power supply. When the three-phase transformer is excited, a power supply voltage is first applied to one phase having a small residual magnetic flux by the first switching unit and the second or third switching unit. Alternatively, the second switch is turned on to apply a voltage to all phases of the three-phase transformer. Therefore, when the power is first turned on to one phase of the three-phase transformer in which the residual magnetic flux density is reduced, the exciting rush current is reduced, so that there is an effect that the exciting rush current can be reduced while using a general transformer. .

A three-phase switch according to a fourth invention is characterized in that the first and second predetermined times are the same in the first or second invention. According to the three-phase switch, since the first and second switching units are shut off after the same predetermined time after the first switching unit is shut off, the three-phase transformer is immediately shut off from the three-phase AC power supply. There is an effect that can be.

A three-phase switch according to a fifth aspect of the present invention is the three-phase switch according to any of the first to fourth aspects, wherein the first to fourth predetermined times are at least one cycle of the frequency of the three-phase AC power supply. It is a feature. According to the three-phase switch, the first to fourth predetermined times are equal to or longer than one cycle of the frequency of the three-phase AC power supply. Since the section can be turned on or off, there is an effect that the exciting rush current can be surely reduced.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 An embodiment of the present invention will be described with reference to FIGS. 1 is a connection diagram of a substation according to an embodiment, and FIG. 2 is a connection diagram of a three-phase switch shown in FIG. 1 and a three-phase transformer including an iron core and a coil. An embodiment applied to a substation will be described. 1 and 2, a substation 1 includes a three-phase AC power supply 3 as a switch S1,
The first terminal t1, the second terminal t2, and the third terminal t3 of the three-phase transformer 7 are connected via a three-phase switch 100 that independently turns on (closes) and shuts off (opens) S2 and S3. Terminal t3
The three-phase switch 100 includes a first switch S1 as a first switch, a second switch S2 as a second switch, and a third switch as a third switch. A control unit 105 that controls opening and closing of S3 independently is connected. Further, the three-phase transformer 7 has a U-phase serving as a first phase between terminals t1 and t2, a V-phase serving as a second phase between terminals t2 and t3, and W serving as a third phase between terminals t1 and t3. Phase coils are connected to each other, and a right-end iron leg 7a forming a U-phase, a center iron leg 7b forming a V-phase, and a left-end iron leg 7c forming a W-phase are provided. It has a coil 7n wound around 7a to 7c.

The three-phase switch 100 is of an electromagnetic type and has a switch S
, S2, and S3 have independent coils C1, C2,
C3, and the control unit 105 has functions of a shutoff control unit and a closing control unit.
The coil C1 is connected to a direct-current control power supply via a command switch Sa for turning on and off commands. One end of an auxiliary normally open contact S11 that opens and closes in synchronization with the switch S1 is connected to a signal power source, and the other end of the auxiliary normally open contact S11 is connected to an input of a timer A107.
Output 07 via a resistor R ₁ is connected to the base of the transistor Tr _1, the collector of the transistor Tr ₁ is connected to the control power supply through the coil C2. Switch S
One end of an auxiliary normally open contact S21 that opens and closes in synchronization with the second terminal is connected to a signal power source, and the other end of the auxiliary normally open contact S21 is connected to an input of a timer B109.
Output 9 is connected to the base of the transistor Tr ₂ via the resistor R _2, the collector of the transistor Tr ₂ is connected to the control power supply through the coil C3. Note that the emitters of the transistors Tr ₁ and Tr ₂ are grounded.

The timer A107 generates an ON signal immediately after the auxiliary normally open contact S11 is closed, and continuously generates an ON signal while the auxiliary normally open contact S11 is closed. The off signal is generated after a time ta from the opening of the normally open contact S11. Timer B10
9 generates an ON signal at time tb after the auxiliary normally open contact S21 is closed, and once the ON signal is generated,
The ON signal is continuously generated while the auxiliary normally open contact S21 is closed, and the OFF signal is generated immediately after the auxiliary normally open contact S21 is opened. Here, the times ta and tb are preferably set to one cycle or more of the power supply frequency of the three-phase AC power supply 3. This is the switch S
In order to establish a magnetization by circulating the hysteresis loop in the iron core legs 7a to 7c of the three-phase transformer 7 once by setting the time lag between the turning on and off of S1, S2 and S3 to be one cycle or more of the power supply frequency. It is.

The operation of the above-configured substation will be described with reference to FIGS. FIG. 3 is a time chart showing the operation of each unit of the substation. Three-phase switch 100
Switches S1, S2 and S3 are all turned on,
Electric power is supplied from the three-phase AC power supply 3 to the three-phase transformer 7, and each of the iron core legs 7a to 7c has the same size and the same phase.
When the command switch Sa is released from the closed state at time t _sf in the state where the magnetic fluxes φu, φv, and φw deviated by 20 ° flow, the excitation of the coil C1 is released, the switch S1 is cut off, and the auxiliary normally open contact is released. S11 is opened.

In this state, since the line voltage E is applied from the three-phase AC power supply 3 to the V-phase terminals t2 and t3 of the three-phase transformer 7, the U-phase terminals t1 and t2 and the W-phase The voltage at the terminals t1 and t3 becomes E / 2. Therefore, the magnitude of the magnetic flux of each phase of the three-phase transformer 5 is expressed by V phase | φ
If v | = φm, the U and W phases are | φu | = | φw | = φ
m / 2. That is, the magnitude | φv | of the magnetic flux at the center iron leg 7b is not different from the magnitude φm of the magnetic flux when the terminals t1 to t3 are connected to the three-phase AC power supply 3, but the iron core legs at both ends are not changed. The magnitudes of magnetic fluxes | φu | and | φw | at 7a and 7c are φm / 2.

[0018] After the auxiliary normally open contact S11 is the閉放, the output of the timer A107 from the open after time ta the transistor Tr ₁ occurring off signal is also turned off,
Switch S2 by the excitation is canceled time _{t 1} of the coil C2
Cut off. That is, the switch S2 is turned off after the first predetermined time from the shutoff command. Blocking at the same time the auxiliary output of the normally open contact S21 is open timer B109 of switch S2 transistor Tr ₂ to generate an OFF signal is also turned off, to cut off the switch S3 exciting coil C3 is released at time t ₂ . That is, the switch S3 is shut off after the second predetermined time from the shut-off command. Accordingly, a residual magnetic flux proportional to the magnitude of the magnetic flux before interruption remains in each of the iron core legs 7a to 7c of the three-phase transformer 7, and the residual magnetic flux is formed by the rightmost iron core leg 7a and the leftmost iron core leg 7b at the center of the iron core. It is 1/2 of the leg 7c.

Next, when the command switch Sa is closed from open at time _tsN , the coil C1 is excited, the switch S1 is turned on, the normally open auxiliary contact S11 is closed, and the output of the timer A107 is output. transistor Tr ₁ and generates an on signal is also turned on, at time t ₃ by exciting the coils C2, turning on the switch S2. That is, the switch S2 is turned on a third predetermined time after the turn-on command. When the switches S1 and S2 are turned on, the terminal t of the three-phase transformer 7 is turned on.
1, t2 to a voltage of three-phase AC power supply 3 magnetizing inrush current I ₀ is generated. In a state where the single-phase voltage E is applied to the terminals t1 and t2, a magnetic flux | φu | = φm is generated in the leftmost iron leg 7a in the U phase, and the center iron legs 7b and W phase in the V phase. Since a voltage of half the single-phase voltage E / 2 is applied to the rightmost iron leg 7c, the magnetic flux | φv |, |
φw | = φm / 2 occurs. Therefore, the maximum magnetizing inrush current _{I 1max} occurs at U phase, a steady state flux density _{B m} 1.7 (T), the remanence _{B r} 0.9B
wherein a and _{m /} 2 (2) becomes the following equation from the equation. I _1max = K (2 × 1.7 + 0.9 × 1.7 / 2−
2) = 2.165K

Next, when the switch S2 is turned on and the auxiliary normally open contact S21 is closed, and after a time tb, the timer B1
The output of 09 is generated an ON signal transistor Tr ₂ is also turned on, the turning on the switch S3 at time t ₄ to energize the coil C3. That is, when the switch S3 is turned on after a fourth predetermined time from the input command, the terminal t2,
The voltage is applied from the three-phase AC power supply 3 with a delay of t3 from the terminals t1 and t2 by a predetermined time (a third predetermined time in claim 1). When the switch S3 is turned on, a large exciting inrush current does not occur. This is already the switch S1,
When S2 is turned on, a single-phase voltage E is applied from the three-phase AC power supply 3 to the terminals t1 and t2 of the three-phase transformer 7, and each iron leg 7a
This is because the residual magnetic flux disappears because the magnetic flux flows through the 7c.

Meanwhile, conventional transformer inrush current _{I 0max} 1.7 is the steady-state magnetic flux density _{B m} (T), the residual magnetic flux density _{B r}
The following equation from the a and 0.9B _m (2) expression. I _0max = K (2 × 1.7 + 0.9 × 1.7-2) =
2.93K determining the ratio n between the magnetizing inrush current _{I 1max} and conventional transformer inrush current _{I 0max} of this embodiment. n = I _1max / I _0max = 2.165K / 2.93
K ≒ 0.74 That is, the exciting rush current is reduced by 26% as compared with the conventional case.

In the above embodiment, when the three-phase transformer 7 is energized, that is, when the switches S1 to S3 are turned on, the switch S1 is turned off, and after a predetermined time has elapsed, the switch S2 is turned off. The switch S3 is turned off, but the switches S2 and S3 may be turned off at the same time after the switch S1 is turned off and a predetermined time has elapsed. Further, the switch S2 may be turned off after the switch S3 is turned off after a lapse of a predetermined time after the switch S1 is turned off. Similarly, the three-phase transformer 7 is in a non-excited state, that is,
In a state where the switches S1 to S3 are turned off, the V phase (second phase) is longer than the U phase (first phase) for a predetermined time (claim 1).
The switches S1 to S3 are turned on so that the voltage of the three-phase AC power supply 3 is applied with a delay of a third predetermined time in
The switches S1 to S3 are set so that the voltage of the three-phase AC power supply 3 is applied with a predetermined time (the third predetermined time in claim 1) delayed from the V phase (the second phase) with respect to the W phase (the third phase). You may put in. Similarly, after the switch S1 is turned on in a state where the three-phase transformer 7 is not excited, the third
The switch S2 is turned on after a predetermined time, and the switch S3 is turned on after a fourth predetermined time from the input command.
After the switch S1 is turned on, the switch S3 may be turned on a third predetermined time after the turning-on command, and the switch S2 may be turned on a fourth predetermined time after the turning-on command. Further, the switches S1 and S2 may be turned on at the same time, and the switch S3 may be turned on after a predetermined time. Further, after the switches S1 and S3 are simultaneously turned on first and a predetermined time has elapsed,
The switch S2 may be turned on. Further, in the above-described embodiment, the three-phase transformer 7 has a delta connection, but even in a star connection, the exciting inrush current is reduced as compared with the related art. Note that the switches S1 to S3 may be configured by semiconductor elements.

[Brief description of the drawings]

FIG. 1 is a connection diagram of a substation according to an embodiment of the present invention.

FIG. 2 is a connection diagram of the three-phase switch shown in FIG. 1 and a three-phase transformer including an iron core and a coil.

FIG. 3 is a time chart illustrating an operation of each unit of the substation illustrated in FIG. 1;

FIG. 4 is a connection diagram of a conventional substation.

[Explanation of symbols]

S1 first opening / closing section, S2 second opening / closing section, S3 third
Opening and closing section, t1 first terminal, t2 second terminal, t3
3rd terminal, 3 three-phase AC power supply, 7 three-phase transformer, 100
Three-phase switch, 105 control unit (cutoff control means, closing control means).

Claims (5)

[Claims] A first phase connected between the first and second terminals; a second phase connected between the second and third terminals; The first phase transformer of a three-phase transformer having a third phase connected between the first and third terminals.
And first to third opening / closing sections respectively connected to turn on and off a voltage to and from a third terminal,
A three-phase switch connected to a three-phase AC power supply, wherein after the first to third switching units are turned on, the first switching unit is shut off based on a shutoff command for the switching unit. Shut-off control means for shutting off the second opening / closing section after a first predetermined time from the shut-off command and shutting off the third opening / closing section after a second predetermined time from the shut-off command;
The second phase of the three-phase transformer supplies the three-phase AC power to the first to third terminals with a delay of the third predetermined time from the first phase or the third phase. And a closing control means for closing the first to third opening / closing sections based on the closing command of the opening / closing section. 2. A three-phase switch having first to third switching units connected to a three-phase transformer and connected to a three-phase AC power supply, wherein the first to third switching units are provided. In the state where is turned on, after shutting off the first opening / closing section based on the shutting down command for the opening / closing section, the second opening / closing section is shut off after a first predetermined time from the shutoff command, and Shutoff control means for shutting off the third opening / closing section after a second predetermined time from the command, and closing the first opening / closing section based on the closing command for the opening / closing section; After a time, the second opening / closing section is turned on,
And a closing control means for closing the third opening / closing section after a fourth predetermined time different from the third predetermined time from generation of the input command. 3. A three-phase switch having first to third switching units connected to a three-phase transformer and connected to a three-phase AC power supply, wherein the first to third switching units are provided. In the state where is turned on, after shutting off the first opening / closing section based on the shutting down command for the opening / closing section, the second opening / closing section is shut off after a first predetermined time from the shutoff command, and Shut-off control means for shutting off the third opening / closing section after a second predetermined time from the command; closing the first opening / closing section and the second or third opening / closing section based on the closing command for the opening / closing section; And a closing control means for closing the third or second opening / closing portion that has not been turned on after a third predetermined time from the generation of the turning-on command. 4. The substation according to claim 1, wherein the first and second predetermined times are the same. 5. The substation according to claim 1, wherein the first to fourth predetermined times are at least one cycle of the frequency of the three-phase AC power supply.