JPH0576143A - Low voltage uninterruptible switchgear and switching mehtod for transformer - Google Patents

Abstract

PURPOSE:To provide a low voltage uninterruptible switching method for switching banks uninterruptibly through only one switchgear. CONSTITUTION:A nonfuse breaker NFB closed when AC switch sections 7, 9 in a bypass circuit B are opened, and the phase detecting circuit in a control circuit 8 detects phase rotation on input and output sides. Output voltage of an inverter circuit 5 is then converted to have same phase and magnitude as those of an output terminal voltage. Subsequently, the AC switch section 7 is closed and the primary cut-out switch PC in bank B is opened to feed the loads in bank B with power from a switchgear S. A reverse conversion switch is then operated to convert the output voltage of the inverter circuit 5 to have same phase and magnitude as those of the input terminal voltage through the control circuit 8 thus turning the AC switch section 7 OFF while the AC switch section 9 ON and feeding the loads in bank B with power from the bypass circuit B of the switchgear S.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low voltage uninterruptible switching device for a transformer and a switching / returning method thereof.

[0002]

2. Description of the Related Art In recent years, due to the diversification of lifestyles and the rapid progress of an advanced information society, the power system, which is one of the cores supporting them, has been increased in scale and complexity. Higher stable supply is required. From these requirements,
A low-voltage instant switching method is being promoted in power equipment construction. For example, as shown in FIG. 8, when the pole transformer Trb of one of the B and B banks is to be replaced, the load LB of the B bank is switched to the A bank and the B bank is under construction. Power is supplied from the bank A to the load LB of the bank, and the load LB is switched back to the bank B after the construction is completed.

As a method of switching the load LB of the B bank to the A bank, when the load side becomes non-voltage with respect to the low voltage switch LS connected to the low voltage side of the B bank, the switch section is automatically operated (corresponding to that). There is a method of connecting a switching switch K1 having a closing action within 10 msec), connecting a switching switch K2 having the same configuration as described above to the branch points of both banks A and B, and then switching according to the following operation. ..

In this method, first, the switching switch K1 is manually turned on. The low-voltage switch LS is manually turned off. The switching switch K1 is manually turned off. Switching switch K2 is load LB
It detects that there is no voltage on the
Within), the state becomes ON, and the current IA starts to flow from the bank A to the load LB side.

Also, the load L that has been switched to the A bank
To switch back B, follow the procedure below. Switching switch K
2 is manually turned off. Switching switch K
1 detects that there is no voltage on the load LB side, and is instantly turned on (within 10 msec), and the current IB flows from the B bank to the load LB side. The low-voltage switch LS is manually turned on. The switching switch K1 is manually turned off. Remove the switching switches K1 and K2.

[0006]

However, the above method has a problem that an instantaneous power failure (within 10 msec) cannot be avoided. In addition, since a low-voltage switch (low-voltage branch box) is required on the secondary side (low-voltage side) of the transformer, this method should be implemented in a system that does not have a low-voltage switch (low-voltage branch box) on the low-voltage side of the transformer. There is a problem that you can not. In addition, two switching switches are required, and there is a problem that it takes time to connect the switching switches and remove the switching switches after the completion of the work.

As a method of avoiding the momentary power failure and switching the load of the B bank to the A bank, there is a loop switching method, which will not be described in detail here. This method has a problem that the loop cannot be performed if the two types of grounding phases of the transformers of both banks that are looped are different.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and the purpose thereof is to carry out completely uninterrupted power supply, and further, to reduce the low voltage of a transformer requiring only one switching device. It is to provide an uninterruptible switching device and a switching / returning method.

[0009]

A low-voltage uninterruptible switching method for a transformer according to a first aspect of the present invention is an inverter circuit having a first switch, and a second circuit connected in parallel to the inverter circuit. A switching device including a bypass circuit having a switch is connected between one bank and the other bank, and when switching between one bank and the other bank, first open the first switch and the second switch. In the inverter circuit, after the output voltage has been converted to the same voltage and phase as the voltage on the one bank side on the output side, the first switch is closed, and then the primary cutout of one bank is opened. After that, the inverter circuit gradually returns the output voltage so that it has the same voltage and the same phase as the voltage on the input side which is the other bank side, and after returning the voltage, the second switch Closed, it is to its gist to supply power via the bypass circuit to open the first switch on the load side of one bank from the other bank.

According to a second aspect of the present invention, there is provided a low voltage uninterruptible fail-back switching method for a transformer, which includes an inverter circuit having a first switch and a bypass connected in parallel to the inverter circuit and having a second switch. A switching device including a circuit is connected between one bank and the other bank, and while power is being supplied from the other bank to the load of the one bank via the bypass circuit, the other bank When switching back to the bank, turn off the second switch to cut off the bypass circuit and close the first switch so that the same voltage and phase as the voltage of the input terminal side which is the other bank side First, the inverter circuit is activated, and then the output voltage is gradually returned to the same voltage and the same phase as the voltage on the output terminal side, which is the bank side, by the inverter circuit. After returning to the output terminal side of the voltage of the click is complete, it is to that closing the primary cutout of one of the banks and the gist thereof.

A low voltage uninterruptible switching device for a transformer according to a third aspect of the present invention comprises an inverter circuit having a first switch, and a bypass circuit connected in parallel to the inverter circuit and having a second switch. , Controlling the conversion of the inverter circuit so that the output voltage has the same voltage and the same phase as the voltage of the bank side which is the output side, and makes the output voltage have the same voltage and the same phase as the voltage of the bank side which is the output side. Then, the first control means for controlling the inverter circuit so as to gradually return the output voltage so that the output voltage becomes the same voltage and the same phase as the original input terminal side voltage, and the output voltage becomes the input side. The inverter circuit is conversion-controlled to have the same voltage and the same phase as the bank side voltage which is, and the output voltage becomes the same voltage and the same phase as the bank side voltage which is the input side. After that, second control means for controlling the inverter circuit so as to gradually return the output voltage so that the output voltage becomes the same voltage and the same phase as the output bank voltage, and the first control means and The gist of the present invention is to include switch control means for turning on and off the first switch or the second switch during operation of the bypass circuit of the first control means.

[0012]

With the above structure, according to the first aspect of the invention, when the switching device switches between one bank and the other bank, the output voltage is first output by the inverter circuit with the first switch and the second switch opened. After completing the conversion to the same voltage and phase as the voltage of one bank on the output side, close the first switch, and then open the primary cutout of one bank, The output voltage is gradually returned to the same voltage and the same phase as the voltage on the input terminal side, which is the bank side, and after the voltage is returned, the second switch is closed and the other voltage is passed through the bypass circuit. Supply power from one bank to the load side of one bank,
Switching is performed without power failure.

According to a second aspect of the present invention, there is provided a low-voltage uninterruptible switching back method for a transformer, in which a power is supplied from the other bank to a load of the one bank through a bypass circuit, and the other bank is operated to When switching back to the bank, first cut off the bypass circuit and close the first switch to operate the inverter circuit first so that it has the same voltage and phase as the voltage on the input terminal side which is the other bank side, and then The inverter circuit gradually returns the output voltage so that it has the same voltage and the same phase as the voltage on the output side of one bank, and after the return to the voltage on the output terminal side of one bank is completed, By closing the primary cutout of the bank, the switchback is performed without interruption. In the low-voltage uninterruptible switching device for a transformer according to the third invention, the bank switching is performed by the uninterruptible transformer according to the methods of the first invention and the second invention.
Switch back is performed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment embodying the present invention will be described below with reference to FIGS. As shown in FIGS. 1 and 2, a primary cutout PC is connected to each phase U, V, W of the high voltage side distribution line L of the transformers Tra, Trb provided in both banks A, B. . Also, A,
A low voltage uninterruptible switching device S is detachably connected via a bypass cable K between the low voltage sides of both banks B.

The low voltage uninterruptible switching device (hereinafter referred to as switching device) S will be described. The switching device S is composed of two systems, a first conversion circuit 1 and a second conversion circuit 2.

A rectifier unit 3, a waveform correction unit 4, an inverter circuit 5, a waveform correction unit 6, an overcurrent limiting circuit 11, an AC switch unit 7 as a first switch, and a control circuit 8 are provided for each of the conversion circuits 1 and 2. I have it. And the first conversion circuit 1
, The input terminal is connected to the P-C1 terminal (power transformer side) of the A bank, and the output terminal is connected to the P-C1 terminal of the B bank.

The input terminal of the second conversion circuit 2 is A
The bank is connected to the C1-C2 terminal (common transformer side) via the changeover switch 10, and the output terminal is connected to the C-N-C2 terminal of the B bank. The rectifier unit 3
Is composed of a single-phase bridge rectifier circuit and full-wave rectifies the input voltage from the A bank. The waveform correction unit 4 corrects the waveform, and the inverter circuit 5 converts the phase of the voltage and the voltage value. The waveform correction unit 6 further corrects the waveform of the electric power output from the inverter circuit 5.

The overcurrent limiting circuit 11 includes a current sensor such as CT, and after bank A and bank B are connected in a loop,
During the parallel operation of the switching device S and the B bank transformer until the primary cutout PC of the bank is opened, an excessive current is generated from the inverter circuit 5 due to the voltage difference due to the difference between the voltage waveform of the switching device S and the voltage waveform of the B bank. The overcurrent is detected so as not to flow out, and a detection signal is output to the control circuit 8. The AC switch unit 7 is composed of a triac or a thyristor, and is turned on / off by operating various switches such as a bypass / inverter changeover switch 12a as a switch control means provided on the operation panel 12 of the switching device S, and a bypass circuit described later. The AC switch section 9 as the second switch of B can be switched.

The control circuit 8 as the first control means and the second control means includes a central processing unit (CPU), a voltage detection phase detection circuit and an inverter control section, and is connected between the input side and the output side of the system. Has been done. The control circuit 8 has a readable / writable memory (hereinafter referred to as RAM) 8a and a read-only memory (hereinafter, referred to as R) that stores a control program and the like.
8b). When the input and output terminals of the system are applied, the voltage detection phase detection circuit of the control circuit 8 has voltage values applied to both terminals,
The phase and phase rotation can be detected. Further, the inverter control unit can control the inverter circuit 5.
The inverter control unit controls the inverter circuit 5 based on the detection signal from the overcurrent limiting circuit 11 to lower the inverter output voltage.

Further, the control circuit 8 converts the input voltage waveform from the A bank of the operation panel 12 provided in the switching device S into the B bank voltage waveform and the inverter output voltage waveform of the switching device S into the A bank. The inverter circuit 5 is controlled by operating an inverse conversion switch (both not shown) for matching the input voltage waveform. By this control, the phases of the single-phase input voltages on the common transformer side and the power transformer side can be individually varied within a range of −180 ° to + 180 °.

Further, the control circuit 8 controls the display unit 13 provided on the operation panel 12 to display various message displays. When the phase applied to the input / output terminals is reverse rotation based on the detection result of the phase rotation, the control circuit 8 controls the changeover switch 10 so that the input terminals C1 and C2 of the second conversion circuit 2 are connected. The connection to the rectifier unit 3 is switched.

The bypass circuit B is connected between the input terminal and the output terminal of each system, and the switching operation of the AC switch section 9 enables efficient operation of the switching device S during operation. The AC switch unit 9 is composed of a triac or a thyristor, and is provided in the switching device S and can be turned on / off and switched to the AC switch unit 7 by operating the operation panel 12.

The no-fuse breaker NFB is provided on the input and output terminal sides of the first conversion circuit 1 and the second conversion circuit 2, and is connected to the connection terminals P and C1 by an external operation from the operation panel provided in the switching device S. , C2 are openable and closable, and are opened when the switching device S has an internal short circuit and the B bank has a short circuit or an overload.

Now, a case will be described in which the load LB of the B bank is switched to the A bank in a state where the switching device S is connected between the A and B banks via the bypass cable K as described above.

First, with the first conversion circuit 1, the second conversion circuit 2 and the AC switch parts 7 and 9 of the bypass circuit B in the switching device S open, the no-fuse breaker NFB is operated by an external operation from the operation panel. Close. In this state, the phase detection circuit of the control circuit 8 detects the phase rotation on the input side and the output side. If the phase rotation is reverse rotation, the changeover switch 10 is controlled to control C1 and C2 on the input terminal side. Swap the connection with. In this embodiment, bank A has the connection shown in FIG. 4A, and bank B has the connection shown in FIG. 4C. In this case, since the phase rotation is the reverse rotation, C1 and C2
Are reversely connected (see FIG. 5B). Then, the output voltage of the inverter circuit 5 is converted into the same phase and the same voltage as the output terminal voltage. That is, as shown in FIGS. 5B and 5C, the vectors between the phases are converted by 120 °. When this conversion is completed, the converted voltage value and phase will be R
The control circuit 8 stores the data in the AM 8a and the operation panel 12
The conversion completion is displayed on the display unit 13 of.

After this display, the operator operates the operation panel 12 to turn on the AC switch section 7. Therefore, in this state, the load LB of the B bank is applied from both the switching device S and the B bank.
Is powered. Then, the primary cutout PC of bank B is opened. After this, the switching device S
Power is supplied from the B bank to the load LB of the B bank. In this embodiment, the vector between VW and UV as shown in FIG. 5 (c) is different from that in FIG. 4 (c), but there is no problem in actual use.

Next, when the reverse conversion switch of the operation panel 12 is turned on, the inverter control section of the control circuit 8 gradually returns the output voltage of the inverter to the same phase and voltage value as the input terminal voltage. When the inverse conversion is completed, the control circuit 8 shows an indication of conversion completion on the display unit 13. After confirming this display, the worker confirms the bypass / inverter changeover switch 12a on the operation panel.
To the bypass side. By this operation, the AC switch unit 7 is turned off and the AC switch unit 9 is turned on. Therefore, thereafter, electric power is supplied from the bypass circuit B of the switching device S to the load LB of the B bank.

In this state, the switching is completed, and after that, the construction of Bank B may be performed. Next, the cutback operation will be described. When the bypass / inverter changeover switch is set to the inverter side after the construction of Bank B is completed, the AC switch unit 7 is turned on and the AC switch unit 9 is turned off. Therefore, after this, from the inverter side of the switching device S to B
Power is supplied to the load LB of the bank. Next, when the conversion switch is turned on, the control circuit 8 gradually converts the inverter output voltage into the voltage value and phase stored in the RAM 8a. When this conversion is completed, the control circuit 8 displays on the display unit 13
Indicates that the conversion is complete.

After that, the primary cutout PC of bank B is inserted. Therefore, in this state, the switching device S
Power is supplied to the load LB of the B bank from both the B bank and the B bank. After that, the no-fuse breaker NFB is opened by an external operation from the operation panel 12, and the switching device S and the bypass cable K are removed from both banks.

Although the phase rotations on the input side and the output side are reverse rotations in the above embodiment, for example, the connection of the transformer of bank A is shown in FIG. 4 (a), and the connection of the transformer of bank B is Figure 4
Since the same rotation occurs in the case of (b), in such a case, the control circuit 8 controls the vector between each phase to rotate the phase by 120 ° in the opposite direction to that described above as shown in FIG. ..

In this embodiment, when the phase detection circuit of the control circuit 8 detects that the phase rotations on the input side and the output side are reverse rotations, the changeover switch 10 operates under the control of the control circuit 8 C1 and C on the input terminal side for the second conversion circuit 2
2 and 2 can be connected in reverse.

Further, in this embodiment, after the bank A and the bank B are connected in a loop, the switching device S and the bank B transformer are operated in parallel until the primary cutout PC of the bank B is opened. Even if a voltage difference occurs due to the difference between the voltage waveform and the voltage waveform of the B bank, the overcurrent limiting circuit 1
Since 1 detects an overcurrent and the control circuit 8 lowers the inverter output voltage, an excessive current does not flow out from the inverter unit 5 and damage to the inverter unit 5 can be prevented.

Next, a second embodiment will be described with reference to FIG.
The same components as those in the above-described embodiment and the corresponding components are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, the second conversion circuit 2 and the changeover switch 10 of the above embodiment are omitted, and instead, the rectifier unit 3 of the conversion circuit 1 is constituted by a three-phase bridge circuit, and its input terminal is P of A bank.
-C1 terminal (power transformer side) and C1-C of A bank
It is connected to two terminals (common transformer side), and the output terminals are B-bank P-C1 terminals and B-bank C1-N-C2.
The part connected to the terminal is different. Then, the detection phase detector of the control circuit 8 detects the voltage value, the phase, and the phase rotation of the input side and the output side, and the inverter circuit 5 can be controlled based on the detection result. That is,
The phase of the three-phase input voltage on the shared transformer side and the power transformer side can be changed.

The operation of the second embodiment will be described. Now,
A case where the load LB of the B bank is switched to the A bank in the state where the switching device S is connected between the A and B banks via the bypass cable K as described above will be described.

First, with the conversion circuit 1 and the bypass circuit B of the switching device S open, the AC fuses NFB are closed by an external operation from the operation panel 12. In this state, the phase detection circuit of the control circuit 8 detects the phase rotation on the input side and the output side. If the phase rotation is positive rotation, the input terminals C1 and C2 are connected as they are, and the phase rotation is reversed. In case of rotation, if C1 and C2 on the input terminal side are reversely connected, the output voltage of the inverter circuit 5 is also converted into the same phase and the same voltage as the output terminal voltage. When this conversion is completed, the converted voltage value and phase are stored in the RAM 8a, and the control circuit 8 controls the display unit 1 of the operation panel 12.
The conversion completion is displayed at 3.

After this display, the operator operates the operation panel 12 to turn on the AC switch section 7. Therefore, in this state, the load LB of the B bank is applied from both the switching device S and the B bank.
Is powered. Then, the primary cutout PC of bank B is opened. After this, the switching device S
Power is supplied from the B bank to the load LB of the B bank.

Next, when the reverse conversion switch of the operation panel is turned on, the inverter control section of the control circuit 8 gradually returns the output voltage of the inverter to the same phase and voltage value as the input terminal voltage. When the inverse conversion is completed, the control circuit 8 shows an indication of conversion completion on the display unit 13. After confirming this display, the worker
The bypass / inverter changeover switch 12a of the operation panel is set to the bypass side. By this operation, the AC switch unit 7 is turned off and the AC switch unit 9 is turned on. Therefore,
After that, electric power is supplied from the bypass circuit B of the switching device S to the load LB of the B bank.

In this state, the switching is completed, and after that, the construction of Bank B may be performed. Next, the cutback operation will be described. When the bypass / inverter changeover switch 12a is set to the inverter side after the construction of Bank B is completed,
The AC switch unit 7 is turned on and the AC switch unit 9 is turned off. Therefore, thereafter, electric power is supplied from the inverter side of the switching device S to the load LB of the B bank. Next, when the conversion switch is turned on, the control circuit 8 gradually converts the inverter output voltage into the voltage value and phase stored in the RAM 8a. When the conversion is completed, the control circuit 8 displays on the display unit 13 that the conversion is completed.

After that, the primary cutout PC of bank B is inserted. Therefore, in this state, the switching device S
Power is supplied to the load LB of the B bank from both the B bank and the B bank. After that, the no-fuse breaker NFB is opened by an external operation from the operation panel 12, and the switching device S and the bypass cable K are removed from both banks.

In this embodiment, when the phase detection circuit of the control circuit 8 detects that the phase rotation on the input side and the output side is reverse rotation, the control circuit 8 automatically controls the input terminal side. The same effect can be obtained by connecting C1 and C2 in reverse.

It should be noted that the present invention is not limited to the above embodiment, and for example, in the first embodiment, the phase rotation on the input side and the output side in the phase detection and detection circuit of the control circuit 8 is reverse rotation. When it is detected, the control circuit 8 switches the changeover switch 10
Although C1 and C2 on the input terminal side are automatically connected in reverse to each other, they can be arbitrarily changed without departing from the spirit of the present invention, such as manually connecting instead.

[0042]

As described above in detail, according to the present invention, bank switching / reverting can be carried out without complete uninterruption, and since only one switching device is required, the operation of bank switching / reverting is simple. Since the difference between the voltage taps of the transformer can be absorbed by the switching device, there is an excellent effect that the switching connection between the banks in which the two kinds of ground phases of the transformers in both banks are different cannot be disabled. ..

[Brief description of drawings]

FIG. 1 is a circuit diagram of a concept in which a switching device is connected to a low voltage side between both banks, showing a first embodiment in which the invention is embodied.

FIG. 2 is an electric circuit diagram of a switching device.

FIG. 3 is an electric circuit diagram of an operation panel.

4 (a), (b), and (c) are explanatory diagrams showing various wirings of the transformer by vectors.

FIG. 5 is an explanatory diagram for conversion from converter connection (a) to converter connection (c).

FIG. 6 is an explanatory diagram for conversion from converter connection (a) to converter connection (b).

FIG. 7 is an electric circuit diagram of a switching device according to a second embodiment of the present invention.

FIG. 8 is a circuit diagram showing a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1st conversion circuit, 2 ... 2nd conversion circuit, 3 ... Rectifier part, 4 ... Waveform correction part 5 ... Inverter circuit, 6 ... Waveform correction part, 7 ... AC switch part as a 1st switch, 8 ... Control circuits as first control means and second control means, 9 ... AC switch section as second switch, 10 ... Changeover switch, 12a
... Bypass / inverter changeover switch as switch control means, Tra, Trb ... Transformer, L ... Distribution line, PC
… Primary cutout, K… Bypass cable,
B ... Bypass circuit, S ... Switching device, NFB ... No fuse breaker.

Claims (3)

[Claims] 1. A switching device comprising an inverter circuit having a first switch and a bypass circuit having a second switch and connected in parallel to the inverter circuit between one bank and the other bank. When switching between one bank and the other bank, first connect the output voltage of the inverter circuit to the same voltage as the output side of one bank with the first switch and the second switch opened. After the voltage and in-phase conversion is completed, the first switch is closed, and then the primary cutout of one bank is opened, and then the same voltage as the voltage on the input side, which is the other bank side, is applied in the inverter circuit. The output voltage is gradually returned to the same phase, and after returning the voltage, the second switch is closed, the first switch is opened, and the other circuit is opened via the bypass circuit. Low uninterruptible switching method of a transformer and supplying power to the load side of one of the banks from the bank. 2. A switching device comprising an inverter circuit having a first switch and a bypass circuit connected in parallel to the inverter circuit and having a second switch between one bank and the other bank. When switching back from the other bank to the one bank while supplying power from the other bank to the load of the one bank via the bypass circuit, turn off the second switch to bypass The circuit is cut off and the first switch is closed to operate the inverter circuit first so that it has the same voltage and phase as the voltage on the input terminal side on the other bank side, and then one of the inverter circuits operates. After gradually returning the output voltage so that it becomes the same voltage and the same phase as the voltage of the output terminal side which is the bank side, and returning to the voltage of the output terminal side of one bank is completed, Low pressure uninterruptible switchback method of the transformer, characterized in that closing the primary cut-out of the square of the bank. 3. An inverter circuit having a first switch, a bypass circuit connected in parallel to the inverter circuit and having a second switch, and an output voltage equal to a voltage on a bank side which is an output side. The inverter circuit is conversion-controlled to have the same voltage and the same phase, and after the output voltage has the same voltage and the same phase as the bank side voltage which is the output side, the output voltage is the original input terminal side voltage. And a first control means for controlling the inverter circuit so as to gradually return the output voltage so as to have the same voltage and the same phase, and the output voltage has the same voltage and the same phase as the bank side voltage which is the input side. The inverter circuit is converted and controlled so that the output voltage becomes the same voltage and the same phase as the voltage of the bank on the input side, and then the output voltage becomes the same voltage as that of the bank on the output side. A second control means for controlling the inverter circuit so as to gradually return the output voltage so that the output voltage and the output voltage become the same phase, and the first control means and the first control means while the bypass circuit is operating, the first control means Switch on or second switch on,
A low voltage uninterruptible switching device for a transformer, comprising a switch control means for controlling off.