Non-excitation inrush current closing control method for secondary control loop of circuit breaker

Abstract

The invention discloses a circuit breaker secondary control loop non-excitation inrush current closing control method, which is realized based on a transformer non-excitation inrush current closing control device, and comprises the following steps: S1, connecting the device to a circuit breaker secondary voltage loop bus to realize power supply side A-phase voltage detection; a closing control contact of the device is connected in series with a common entry point of remote mode closing and local mode closing of a secondary control loop of the circuit breaker, and an opening control contact is connected in series with a common entry point of remote mode opening and local mode opening of the secondary control loop of the circuit breaker; s2, starting the device and inputting the pre-measured opening / closing time of the circuit breaker; and S3, when the device detects the arrival of the opening / closing operation voltage, immediately detecting the A-phase voltage, when the rising edge of the A-phase voltage is detected to cross the zero point, calculating the delay time X1mS / X2mS, then starting the corresponding control contact to be switched on, powering up the opening / closing coil of the circuit breaker, and realizing the opening / closing of the highest point of the A-phase voltage. According to the invention, the closing excitation inrush current of the transformer can be reduced to the maximum extent.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a method for controlling non-excitation inrush current closing of a secondary control circuit of a circuit breaker. Background Art

[0002] Power transformers are key equipment in power systems and play an extremely important role in the safe operation of power grids. However, due to the influence of the magnetic characteristics of the transformer's internal core, when the transformer is put into operation without load, an excitation surge current will appear, which can sometimes reach 6-8 times the rated current of the transformer.

[0003] When the transformer is put into operation, excessive excitation inrush current will cause the transformer vibration and sound to increase significantly, generate a large number of asymmetric even harmonics in the excitation current in a short time, and the zero-sequence current will increase several times. This not only increases the risk of transformer damage, but may also cause the transformer's protection device to operate, resulting in a closing failure; abnormal vibration of the transformer will affect the transformer's structural parts and reduce the transformer's reliability; the increase in zero-sequence current will seriously affect the normal operation of nearby transformers, and even trip, threatening the safe operation of the power grid.

[0004] At present, the main research directions at home and abroad are to eliminate the influence of transformer residual magnetism on the excitation inrush current; the other is to control the closing angle to minimize the excitation inrush current. However, due to the synchronous closing of the three-phase power supply, the closing angle is random when the power transformer is closed at no load. Due to the different closing angles, the excitation inrush current generated is also sufficient to cause the differential protection of large transformers to operate, resulting in closing failure. At the same time, the current method to solve the closing angle control of power transformers is mainly to study the closing angle control device, the main principle of which is to detect the opening angle of the transformer and close the switch at the opening angle. The principle structure of this control device is complex and the cost is high. Moreover, after the transformer is overhauled, the principle of reducing the non-excitation inrush current fails and may cause a larger excitation inrush current (when closing at the voltage zero point). Therefore, this control device is rarely used in power systems.

[0005] Patent ZL202211269405.6 discloses a method for reducing the excitation inrush current of a large transformer, which proposes to reduce the excitation inrush current by using the residual magnetism of the transformer and controlling the closing angle. However, the circuit breaker control circuit currently used to power large transformers generally does not have a closing angle control device, and there is no specific and practical installation and application solution for the equipment in the secondary circuit.

[0006] Patent ZL202410251359.X discloses a transformer non-excitation inrush current closing control device and test method. Although it can realize basic functions by controlling the opening and closing angles of the portable control device, it is inconvenient to operate and may bring risks such as wiring errors.

[0007] Therefore, it is necessary to develop an online circuit breaker secondary control circuit non-excitation inrush current closing control method and an online installed transformer non-excitation inrush current closing control device to better promote and apply the transformer non-excitation inrush current closing technology. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a method for controlling the closing of a secondary control circuit of a circuit breaker without an excitation inrush current, which can directly realize the opening / closing at the highest point of the A-phase voltage amplitude without affecting the normal operation of the circuit breaker remotely / locally, thereby minimizing the excitation inrush current.

[0009] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows.

[0010] The circuit breaker secondary control circuit no-excitation inrush current closing control method is implemented based on the transformer no-excitation inrush current closing control device, and includes the following steps:

[0011] S1. Connect the device to the busbar of the secondary voltage circuit of the circuit breaker to realize the voltage detection of phase A on the power supply side, connect the closing control contact of the device in series to the common entry point of the remote mode closing and local mode closing of the secondary control circuit of the circuit breaker, and connect the opening control contact in series to the common entry point of the remote mode opening and local mode opening of the secondary control circuit of the circuit breaker;

[0012] S2. Start the device and input the previously determined circuit breaker opening / closing time through the device;

[0013] S3. When the device detects the arrival of the opening / closing operation voltage, it immediately detects the A-phase voltage. When it detects that the rising edge of the A-phase voltage passes through the zero point, it calculates the delay X1mS / X2mS based on the stored circuit breaker opening / closing time, and then starts the corresponding control contact to connect, energize the circuit breaker opening / closing coil, and realize the highest point of the A-phase voltage opening / closing.

[0014] Preferably, the transformer non-excitation inrush current closing control device includes an opening / closing operation detection unit for continuously detecting the opening / closing operation voltage signal of the circuit breaker secondary control circuit, an opening / closing control unit for being connected in series to the circuit breaker opening / closing control circuit to realize the opening / closing of the circuit breaker, a synchronous voltage detection unit for being connected to the secondary side voltage bus of the A-phase voltage transformer on the power supply side and converting the sinusoidal wave voltage on the secondary side of the voltage transformer into a square wave, an opening / closing time input unit for inputting the circuit breaker opening / closing time determined in advance, and a CPU control unit integrating the functions of reading opening / closing time, monitoring opening / closing operation, collecting synchronous voltage and starting / stopping the circuit breaker opening / closing control unit connection; the input end of the CPU control unit is respectively connected to the output ends of the opening / closing time input unit, the opening / closing operation detection unit and the synchronous voltage detection unit, and the output end of the CPU control unit is connected to the input end of the opening / closing control unit.

[0015] Preferably, the opening / closing control unit includes an opening control contact and a closing control contact.

[0016] Preferably, the opening / closing control unit is a high-power contact with zero delay.

[0017] Preferably, the control contacts of the opening / closing control unit are passive contacts that can operate all the time and will not malfunction.

[0018] Preferably, the opening / closing control unit comprises an opening pressure plate for realizing short circuit of opening control contacts and a closing pressure plate for realizing short circuit of closing control contacts.

[0019] Preferably, the opening / closing time input unit comprises a key for inputting a previously determined opening / closing time of the circuit breaker and a liquid crystal display screen for displaying the opening / closing time.

[0020] Preferably, the transformer non-excitation inrush current closing control device also includes a control panel, on which is provided a terminal block for externally connecting a circuit to realize the connection of an opening / closing control unit in series with the opening / closing control circuit of the circuit breaker and the connection of a synchronous voltage detection unit to the secondary side of the A-phase voltage transformer on the power supply side; the opening pressure plate, closing pressure plate, buttons and liquid crystal display are all arranged on the control panel.

[0021] Due to the adoption of the above technical scheme, the technical progress achieved by the present invention is as follows.

[0022] The present invention realizes a method for controlling the closing of a secondary control circuit of a circuit breaker powered by a control transformer without an excitation inrush current and a method for modifying the secondary control circuit of an existing circuit breaker powered by a control transformer. The method can directly realize opening / closing at the highest point of the A-phase amplitude without affecting the normal operation of the circuit breaker remotely / locally, thereby minimizing the excitation inrush current.

[0023] The present invention is highly efficient: compared with the complicated operation of using a portable device to control the opening and closing angle controller, the present invention does not need to connect the control line of the controller to the secondary control circuit of the circuit breaker every time the switch is opened / closed, thus avoiding the possibility of operational errors during temporary wiring.

[0024] The present invention has reliability: passive contact control is adopted to fundamentally avoid the possibility of false triggering; after the pressure plate is short-circuited, the operation can be stopped, and after an unexpected failure of the output line of the device, the normal opening and closing operation function is not affected.

[0025] The device used in the present invention is directly connected in series to the secondary control circuit of the circuit breaker, and can automatically realize the opening / closing at the highest point of the A-phase voltage during manual and remote opening / closing, with a delay time of tens of milliseconds, which is imperceptible to the operator.

[0026] The serial connection position of the device used in the present invention can realize the opening / closing of the highest point of the A-phase voltage manually / remotely and automatically without affecting the reaction time of the protection tripping and the function of the existing protection device. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a principle block diagram of the transformer non-excitation inrush current closing control device in the present invention;

[0028] Figure 2 A control panel layout diagram of the transformer non-excitation inrush current closing control device in the present invention;

[0029] Figure 3 A circuit diagram of an opening / closing operation detection unit of a transformer non-excitation inrush current closing control device in the present invention;

[0030] Figure 4 A circuit diagram of an opening / closing control unit of a transformer non-excitation inrush current closing control device in the present invention;

[0031] Figure 5 The invention provides a diagram showing the connection position of the opening / closing control unit of the transformer non-excitation inrush current closing control device in series with the existing circuit breaker opening / closing control circuit.

[0032] Figure 6 The circuit diagram of the synchronous voltage detection unit of the transformer non-excitation inrush current closing control device in the present invention.

[0033] Among them: 1. Opening pressure plate, 2. Closing pressure plate, 3. LCD display, 4. Buttons, 5. Terminal block. DETAILED DESCRIPTION

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] The circuit breaker secondary control circuit no-excitation inrush current closing control method is based on the transformer no-excitation inrush current closing control device, combined with Figure 1 to Figure 2 As shown, it includes an opening / closing operation detection unit, an opening / closing control unit, a synchronous voltage detection unit, an opening / closing time input unit and a CPU control unit, wherein the input end of the CPU control unit is respectively connected to the output ends of the opening / closing time input unit, the opening / closing operation detection unit and the synchronous voltage detection unit, and the output end of the CPU control unit is connected to the input end of the opening / closing control unit.

[0036] The opening / closing operation detection unit is used to continuously detect the opening / closing operation voltage signal of the secondary control circuit of the circuit breaker. When the operation voltage is detected in the secondary control circuit of the circuit breaker, the CPU control unit starts the opening / closing program at the highest point of the synchronous voltage signal through the step-down optical isolation. When the opening / closing operation detection unit detects that the opening / closing operation voltage of the secondary control circuit of the circuit breaker disappears, the CPU control unit controls the disconnection of the opening / closing control unit contact. The circuit diagram of the opening / closing operation detection unit is shown in FIG. Figure 3 shown.

[0037] The opening / closing control unit is a high-power contact with zero delay, which can be connected with zero delay after receiving the instruction from the CPU control unit. The contacts of the opening / closing control unit are connected in series to the opening / closing control circuit of the circuit breaker. When the zero-delay contacts are connected, the opening / closing coil of the circuit breaker starts to be energized to realize the opening / closing of the circuit breaker. Specifically, the opening / closing control unit includes an opening control contact and a closing control contact, wherein the opening control contact is connected in series to the opening control circuit of the circuit breaker; and the closing control contact is connected in series to the closing control circuit of the circuit breaker. The circuit diagram of the circuit breaker opening / closing control unit is shown in the figure below. Figure 4 As shown. Figure 5 As shown, taking the schematic diagram of an ordinary transformer secondary protection circuit as an example, the access positions of the opening control contacts and the closing control contacts are explained (refer to this principle method to determine the modification access position on site).

[0038] Figure 5The microcomputer protection of the secondary circuit transformer has no protective closing function and does not consider the protective closing circuit. Therefore, there is only one closing entrance for the transformer. The front end of the closing entrance is divided into remote mode, local mode and maintenance mode. The principle is to connect the closing control contact in series to the common entrance point of the remote mode closing and local mode closing of the secondary control circuit of the circuit breaker to ensure that in various modes, closing can be achieved at the highest point of phase A voltage.

[0039] by Figure 5 For example, the protection terminal XB1:5 is the local closing point, the protection terminal In527 (the closing switch when YHJ-1 is remotely controlled) is the remote closing point, and the protection terminal In507 is the common point for local closing and remote closing. Therefore, the closing control contact should be connected in series to the entrance of the protection terminal In507 to achieve closing at the highest voltage point of phase A.

[0040] The transformer microcomputer protection has a protection tripping function. Considering the rapidity and safety of the protection tripping, the tripping control contact should be modified on the premise of skipping the protection tripping circuit. The front end of the tripping entrance is divided into remote mode, local mode and maintenance mode. The principle is to connect the tripping control contact in series to the common entrance point of the remote mode tripping and local mode tripping of the circuit breaker secondary control circuit. By connecting in series at this position, it can be strictly separated from the protection tripping circuit without affecting the reaction time of the protection tripping (BTJ-1 is the protection tripping switch), thereby not affecting the normal operation of the protection tripping circuit, ensuring that the tripping can be achieved at the highest point of the A phase voltage in various modes.

[0041] by Figure 5 For example, the protection terminal 1KK:4 is the local trip point, the protection terminal In526 (closing switch when YTJ-1 is remotely controlled) is the remote trip point, and the protection terminal In504 is the common point for local closing and remote closing. Therefore, the trip control contact should be connected in series to the entrance of the protection terminal In504 to realize the separation protection trip circuit. The manual trip and remote control trip are opened at the highest voltage point of phase A. And BTJ-1 is the protection trip exit, and the access position of the trip control contact has no effect on the protection trip of BTJ-1.

[0042] The control contacts of the opening / closing control unit are passive contacts, which can operate all the time without malfunction. When the opening / closing operation detection unit detects that the opening / closing operation voltage of the control circuit disappears, the CPU control unit controls the disconnection of the opening / closing control unit contacts. The circuit breaker opening / closing control unit includes an opening pressure plate 1 and a closing pressure plate 2. Both the opening pressure plate 1 and the closing pressure plate 2 are hard pressure plates, wherein the opening pressure plate 1 is used to achieve a short circuit of the opening control contacts; the closing pressure plate 2 is used to achieve a short circuit of the closing control contacts. When the circuit breaker opening / closing operation is completed, the opening pressure plate 1 and the closing pressure plate 2 can be used to short-circuit the opening control contacts and the closing control contacts to exit operation (or it can run all the time).

[0043] The synchronous voltage detection unit is connected to the secondary voltage bus of the A-phase voltage transformer on the power supply side, and the voltage is isolated and reduced through the voltage transformer. The synchronous voltage detection unit includes a detection circuit, which is connected to the secondary voltage circuit bus of the circuit breaker and converts the sine wave voltage on the secondary side of the voltage transformer into a square wave, which is provided to the CPU control unit. The CPU control unit detects the zero crossing point of the sine wave based on the square wave. The circuit diagram of the synchronous voltage detection unit is shown in FIG. Figure 6 shown.

[0044] The opening / closing time input unit adopts a combination of liquid crystal and buttons, including buttons 4 and liquid crystal display screen 3, wherein button 4 is used to input the previously determined opening / closing time of the circuit breaker; and liquid crystal display screen 3 is used to realize the opening / closing time display. After the device detects the operating voltage signal, it calculates and delays the high-power contact of the opening / closing control unit to connect the opening / closing voltage operation circuit according to the phase of the synchronous voltage signal and the previously input opening / closing time value, and realizes the voltage phase at the time of opening / closing the opening / closing circuit breaker.

[0045] The CPU control unit uses a high-speed 8-bit single-chip microcomputer to complete each functional unit module. The CPU control unit includes the functions of reading the opening and closing time, monitoring the opening and closing operation, collecting the synchronous voltage, and starting / stopping the circuit breaker opening / closing control unit connection.

[0046] The device also includes a control panel, on which a terminal block 5 is provided, and the terminal block 5 is used for external connection lines, so as to realize that the circuit breaker opening / closing control unit is connected in series with the circuit breaker opening / closing control circuit and the synchronous voltage detection unit is connected to the secondary voltage bus terminal of the A-phase voltage transformer on the power supply side. Specifically, the opening pressure plate 1, the closing pressure plate 2, the button 4 and the liquid crystal display screen 3 are all arranged on the control panel.

[0047] When the device is in use, the overall working principle is as follows:

[0048] 1) When the opening pressure plate 1 and closing pressure plate 2 of the opening / closing control unit are short-circuited, the device will not function at all, and the opening / closing control signal will pass directly through the opening pressure plate 1 and closing pressure plate 2, which is equivalent to the device exiting operation.

[0049] 2) When the opening pressure plate 1 and closing pressure plate 2 of the opening / closing control unit are opened, the device is put into operation. The previously determined opening / closing time of the circuit breaker is input and saved to the CPU control unit through the button 4 and the LCD screen 3. The CPU control unit continuously detects whether the opening / closing operation voltage appears through the opening / closing operation detection unit. When the opening / closing operation voltage is detected, the synchronous voltage detection unit is immediately started to detect the A-phase voltage. When the rising edge of the A-phase voltage is detected to pass through the zero point, the delay X1mS / X2mS is calculated according to the stored circuit breaker opening / closing time, and then the opening / closing control unit is started to control the contact to connect, and the circuit breaker opening / closing coil is energized to achieve the highest point of the A-phase voltage opening / closing; when the opening / closing operation voltage is detected to disappear, the CPU control unit disconnects the circuit breaker opening / closing control unit control contact and waits for the next operation.

[0050] 3) This device uses passive contact control and there is no possibility of malfunction; when the device fails, the built-in opening pressure plate 1 and closing pressure plate 2 can be used to short-circuit the device and make it stop running, without adversely affecting the original control function.

[0051] The principle of closing the circuit breaker without excitation inrush current is divided into the following two cases:

[0052] 1) Closing of large transformers after maintenance: After maintenance, large transformers are pre-magnetized according to the methods of patent ZL202211269405.6 (three-phase split transformer) and patent ZL202410251359.X (three-phase integrated transformer). When closing the transformer manually or remotely, the device delays closing so that the closing point is at the highest amplitude of the A-phase voltage, realizing closing without excitation inrush current.

[0053] 2) Closing of power-off transformers that do not require maintenance: When a transformer that does not require maintenance is locally / remotely powered off, this device is used to delay power off so that the power-off point is at the highest point of the A-phase voltage amplitude; when closing the transformer, this device is also used to close the transformer at the highest point of the A-phase voltage amplitude, thus achieving non-excitation inrush current closing.

[0054] Application of the five-time impact closing test for new transformers / inductors:

[0055] First closing: After the handover test, the large transformer is pre-magnetized according to the method of patent ZL202211269405.6 (three-phase split transformer) and patent ZL202410251359.X (three-phase integrated transformer). When closing manually or remotely, the device delays closing so that the closing point is at the highest amplitude of the A-phase voltage, realizing non-excitation inrush current closing.

[0056] The last four closing times: When the local / remote power outage occurs, the power is delayed by this device to make the power-off point at the highest point of the A-phase voltage amplitude; when closing the circuit, the circuit is also closed at the highest point of the A-phase voltage amplitude through this device to achieve closing without excitation inrush current.

[0057] The device has strong versatility and the same functions can be integrated into microcomputer protection devices.

[0058] A circuit breaker secondary control circuit no-excitation inrush current closing control method is implemented based on a transformer no-excitation inrush current closing control device, which can realize transformer power supply control, and includes the following steps:

[0059] S1. Connect the device to the busbar of the secondary voltage circuit of the circuit breaker to realize the A-phase voltage detection on the power supply side, connect the closing control contact of the device in series to the common entry point of the remote mode closing and local mode closing of the secondary control circuit of the circuit breaker, and connect the opening control contact in series to the common entry point of the remote mode opening and local mode opening of the secondary control circuit of the circuit breaker.

[0060] S2. Start the device and input the previously determined circuit breaker opening / closing time through the device.

[0061] S3. When the device detects the arrival of the opening / closing operation voltage, it immediately detects the A-phase voltage. When it detects that the rising edge of the A-phase voltage passes through the zero point, it calculates the delay X1mS / X2mS based on the stored circuit breaker opening / closing time, and then starts the corresponding control contact to connect, energize the circuit breaker opening / closing coil, and realize the highest point of the A-phase voltage opening / closing.

Claims

1. A circuit breaker secondary control circuit non-excitation inrush current closing control method is implemented based on a transformer non-excitation inrush current closing control device, and is characterized by: The following steps are involved: S1. Connect the device to the busbar of the secondary voltage circuit of the circuit breaker to realize the voltage detection of phase A on the power supply side, connect the closing control contact of the device in series to the common entry point of the remote mode closing and local mode closing of the secondary control circuit of the circuit breaker, and connect the opening control contact in series to the common entry point of the remote mode opening and local mode opening of the secondary control circuit of the circuit breaker; S2. Start the device and input the previously determined circuit breaker opening / closing time through the device; S3. When the device detects the arrival of the opening / closing operation voltage, it immediately detects the A-phase voltage. When it detects that the rising edge of the A-phase voltage passes through the zero point, it calculates the delay X1mS / X2mS based on the stored circuit breaker opening / closing time, and then starts the corresponding control contact to connect, energize the circuit breaker opening / closing coil, and realize the highest point of the A-phase voltage opening / closing.

2. The circuit breaker secondary control circuit non-excitation inrush current closing control method according to claim 1, characterized in that: The transformer non-excitation inrush current closing control device comprises an opening / closing operation detection unit for continuously detecting the opening / closing operation voltage signal of the secondary control circuit of the circuit breaker, an opening / closing control unit for being connected in series to the opening / closing control circuit of the circuit breaker to realize the opening / closing of the circuit breaker, a synchronous voltage detection unit for being connected to the secondary voltage bus of the A-phase voltage transformer on the power supply side and converting the sine wave voltage on the secondary side of the voltage transformer into a square wave, an opening / closing time input unit for inputting the opening / closing time of the circuit breaker determined in advance, and a CPU control unit integrating the functions of reading the opening / closing time, monitoring the opening / closing operation, collecting the synchronous voltage, and starting / stopping the opening / closing control unit of the circuit breaker; The input end of the CPU control unit is connected to the output ends of the opening / closing time input unit, the opening / closing operation detection unit and the synchronous voltage detection unit respectively, and the output end of the CPU control unit is connected to the input end of the circuit breaker opening / closing control unit.

3. The circuit breaker secondary control circuit non-excitation inrush current closing control method according to claim 2, characterized in that: The opening / closing control unit comprises an opening control contact and a closing control contact.

4. The circuit breaker secondary control circuit non-excitation inrush current closing control method according to claim 3, characterized in that: The opening / closing control unit is a high-power contact with zero delay.

5. The circuit breaker secondary control circuit non-excitation inrush current trip control method according to claim 3, characterized in that: The control contacts of the opening / closing control unit are passive contacts that can operate all the time and will not cause malfunction.

6. The circuit breaker secondary control circuit non-excitation inrush current closing control method according to claim 3, characterized in that: The opening / closing control unit comprises an opening pressure plate (1) for realizing a short circuit of an opening control contact and a closing pressure plate (2) for realizing a short circuit of a closing control contact.

7. The circuit breaker secondary control circuit non-excitation inrush current closing control method according to claim 6, characterized in that: The opening / closing time input unit comprises a key (4) for inputting a circuit breaker opening / closing time determined in advance and a liquid crystal display screen (3) for realizing opening / closing time display.

8. The circuit breaker secondary control circuit non-excitation inrush current closing control method according to claim 7, characterized in that: The transformer non-excitation inrush current closing control device further comprises a control panel, on which a terminal block (5) is provided for connecting an external circuit to realize the connection of an opening / closing control unit in series with a circuit breaker opening / closing control circuit and the connection of a synchronous voltage detection unit to a secondary voltage busbar of an A-phase voltage transformer on the power supply side; the opening pressure plate (1), the closing pressure plate (2), the buttons (4) and the liquid crystal display screen (3) are all arranged on the control panel.

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