Non-magnetizing inrush current switching-on control device for on-line installed transformer

Abstract

The utility model discloses a non-excitation inrush current switching-on control device of an on-line installed transformer. The opening / closing operation detection unit is used for continuously detecting opening / closing operation voltage signals of a secondary control loop of the circuit breaker; the opening / closing control unit is connected in series into the opening / closing control loop of the circuit breaker to realize opening / closing of the circuit breaker; the synchronous voltage detection unit is used for being connected with a secondary side voltage bus of a power supply side A-phase voltage transformer and converting sine wave voltage of the secondary side of the voltage transformer into square waves; the opening / closing time input unit is used for inputting opening / closing time of a circuit breaker, which is measured in advance; and the CPU control unit integrates the functions of monitoring the opening and closing operation, collecting the synchronous voltage and starting / stopping the connection of the breaker opening / closing control unit. The excitation circuit is simple in structure and low in cost, and excitation inrush current can be reduced to the maximum extent.

Description

Technical Field

[0001] The utility model relates to the technical field of power systems, and in particular to an online-installed transformer no-excitation inrush current closing control device, which is applied to the technical transformation of the secondary control circuit of the circuit breaker for controlling the power supply of the existing transformer and the design, installation and application of the secondary control circuit of the circuit breaker for controlling the power supply of the transformer in a new substation. 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 magnetic properties of the transformer's internal core, magnetizing inrush current occurs when the transformer is operated at no load. Sometimes, this inrush current can reach 6-8 times the transformer's rated current.

[0003] When a transformer is put into operation, excessive inrush current can cause a significant increase in transformer vibration and noise, briefly generating a large number of asymmetric even-order harmonics in the excitation current, and multiplying the zero-sequence current several times. This not only increases the risk of transformer damage but can also trigger the activation of transformer protection devices, causing closing failures. Abnormal transformer vibration can affect the transformer's structural components and reduce its reliability. In severe cases, the increase in zero-sequence current can affect nearby normally operating transformers, causing them to trip and threaten the safety of power grid operations.

[0004] Currently, the main research directions at home and abroad are to eliminate the impact of transformer residual magnetism on magnetizing inrush current; another approach is to control the closing angle to minimize magnetizing inrush current. However, due to the synchronous closing of the three-phase power supply, the closing angle when closing the power transformer under no-load conditions is random. Due to the different closing angles, the magnetizing inrush current generated is sufficient to trigger the differential protection of large transformers, causing closing failure. At the same time, the current approach to controlling the closing angle of power transformers mainly involves the development of closing angle control devices, whose main principle is to detect the opening angle of the transformer and close the circuit at the opening angle. The principle structure of this control device is complex and costly. Moreover, after the transformer is repaired, the principle of reducing the non-excitation inrush current fails, and may cause even greater magnetizing inrush current (when closing at the voltage zero crossing point). Therefore, this control device is rarely used in power systems.

[0005] Patent ZL202211269405.6 discloses a method for reducing magnetizing inrush current in large transformers, proposing to utilize transformer residual magnetism and control the closing angle to reduce magnetizing inrush current. However, circuit breaker control circuits currently used to power large transformers generally lack a device for controlling the opening and closing angles, and there is no specific, practical installation solution for equipment in the secondary circuit.

[0006] Patent ZL202410251359.X discloses a transformer no-excitation inrush current closing control device and test method. It is a portable control device that controls the opening and closing angles. Although it can achieve basic functions, it is inconvenient to operate and may bring risks such as wiring errors. Utility Model Content

[0007] The technical problem to be solved by the utility model is to provide an online-installed transformer non-excitation inrush current closing control device, which has a simple structure and low cost. It can directly realize opening / closing at the highest point of the A-phase amplitude without affecting the normal operation of the circuit breaker remotely, thereby minimizing the excitation inrush current without affecting the normal protection tripping function of the circuit breaker.

[0008] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows.

[0009] A transformer no-excitation inrush current closing control device for online installation includes an opening / closing operation detection unit for continuously detecting the opening / closing operation voltage signal of a circuit breaker secondary control circuit, an opening / closing control unit for being serially connected 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 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 a pre-determined circuit breaker opening / closing time, 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 circuit breaker opening / closing control unit.

[0010] Preferably, the opening / closing control unit includes an opening control contact connected in series to the circuit breaker opening control circuit and a closing control contact connected in series to the circuit breaker closing control circuit; the closing control contact is connected in series to the common entry point of the remote mode closing and local mode closing of the circuit breaker secondary control circuit; the opening control contact is connected in series to the common entry point of the remote mode opening and local mode opening of the circuit breaker secondary control circuit, and is separated from the protection tripping circuit.

[0011] Preferably, the opening / closing control unit is a high-power contact with zero delay.

[0012] Preferably, the control contacts of the opening / closing control unit are passive contacts that can operate all the time and will not malfunction.

[0013] Preferably, the opening / closing control unit includes an opening pressure plate for achieving short circuit of the opening control contacts and a closing pressure plate for achieving short circuit of the closing control contacts.

[0014] Preferably, the opening / closing time input unit includes a key for inputting a pre-determined opening / closing time of the circuit breaker and a liquid crystal display screen for displaying the opening / closing time.

[0015] Preferably, the device also includes a control panel, which is provided with a terminal block for external connection lines to realize the connection of the circuit breaker opening / closing control unit in series with the circuit breaker opening / closing control circuit and the connection of the synchronous voltage detection unit to the secondary side voltage bus of the A-phase voltage transformer on the power supply side; the opening pressure plate, closing pressure plate, buttons and LCD display are all arranged on the control panel.

[0016] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is as follows.

[0017] The utility model has a simple structure and low cost. Through the provision of an opening / closing operation detection unit, a circuit breaker opening / closing control unit, a synchronous voltage detection unit, an opening / closing time input unit and a CPU control unit, the opening / closing at the highest point of the A-phase amplitude can be directly realized without affecting the normal operation of the circuit breaker remotely and on-site and the protection tripping function. The pre-magnetization method of the patent ZL202211269405.6 and patent ZL202410251359.X (three-phase integrated transformer) is combined to achieve the maximum reduction of the excitation inrush current.

[0018] The utility model is highly efficient: compared with the complicated operation of using a portable device to control the opening and closing angle controller, the device does not need to connect the control line of the controller to the secondary control circuit every time the switch is opened / closed, thus avoiding the possibility of operational errors during temporary wiring.

[0019] The utility model has reliability: the device adopts passive contact control, which fundamentally avoids the possibility of false triggering; after the pressure plate is short-circuited, the device can exit operation, and after an unexpected failure of the output line of the device, the normal opening and closing operation functions are not affected.

[0020] The utility model is directly connected in series to the secondary control circuit, and automatically realizes opening / closing at the highest point of phase A voltage during manual and remote opening / closing. The delay time is tens of milliseconds and the operator cannot feel it.

[0021] The serial connection position of the utility model can realize the opening / closing of the highest voltage point of phase A manually / remotely controlled automatically without affecting the reaction time of the protection tripping and having no influence on the function of the existing protection device.

[0022] The utility model has a small size and can be directly installed in an existing protection screen / cabinet without the need to reinstall a new screen / cabinet. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a principle block diagram of the utility model;

[0024] Figure 2 This is a layout diagram of the control panel of the present utility model;

[0025] Figure 3 This is a circuit diagram of the opening / closing operation detection unit of the utility model;

[0026] Figure 4 This is a circuit diagram of the circuit breaker opening / closing control unit of the present utility model;

[0027] Figure 5 This is a diagram showing the connection positions of the circuit breaker opening / closing control unit of the present invention in series with the existing circuit breaker opening / closing control circuit.

[0028] Figure 6 This is a circuit diagram of the synchronous voltage detection unit of the present utility model.

[0029] Including: 1. Opening pressure plate, 2. Closing pressure plate, 3. LCD display, 4. Buttons, 5. Terminal block. DETAILED DESCRIPTION

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0031] An online installed transformer no-excitation inrush current closing control device, combined with Figures 1 to 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 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 opening / closing control unit.

[0032] 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 operating 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 the figure below. Figure 3 shown.

[0033] The opening / closing control unit is a high-power contact with zero delay. After receiving the instruction from the CPU control unit, it can be connected with zero delay. 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 contact is 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; 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 as follows: Figure 4 As shown. Figure 5 As shown, taking the schematic diagram of the ordinary transformer secondary protection circuit as an example, the connection positions of the opening control contacts and the closing control contacts are explained (refer to this principle method to determine the modification connection position on site).

[0034] Figure 5 The 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. This 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 circuit breaker secondary control circuit to ensure that in various modes, closing can be achieved at the highest point of phase A voltage.

[0035] 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 input of the protection terminal In507 to achieve closing at the highest voltage point of phase A.

[0036] The transformer microcomputer protection has a protection tripping function. Considering the rapidity and safety of the protection tripping, the tripping control contact should be designed based 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. This 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, and ensuring that the tripping can be achieved at the highest point of the A-phase voltage in various modes.

[0037] by Figure 5For example, consider the following analysis: Protection terminal 1KK:4 is the local trip point, protection terminal In526 (the closing switch when YTJ-1 is remotely controlled) is the remote trip point, and protection terminal In504 is the common point for both local and remote closing. Therefore, the trip control contact should be connected in series to the input of protection terminal In504 to separate the protection trip circuits. Manual and remote trips occur at the highest voltage point on phase A. Furthermore, BTJ-1 is the protection trip output, so the location of the trip control contact has no effect on BTJ-1's protection tripping.

[0038] The control contacts of the opening / closing control unit are passive contacts and can operate continuously 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. The opening pressure plate 1 is used to short-circuit the opening control contacts; the closing pressure plate 2 is used to short-circuit 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, and then exit operation (or continue to run).

[0039] 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 stepped down by 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 the figure below. Figure 6 shown.

[0040] The opening / closing time input unit utilizes a combination of liquid crystal and buttons, including buttons 4 and an LCD display 3. Buttons 4 are used to input the pre-determined opening / closing time for the circuit breaker, while LCD display 3 displays the opening / closing time. After detecting the operating voltage signal, the device calculates and delays the high-power contacts of the opening / closing control unit based on the phase of the synchronous voltage signal and the pre-entered opening / closing time value, connecting the opening / closing voltage operating circuit. This ensures that the opening / closing circuit breaker is opened / closed at the highest point of the synchronous voltage amplitude.

[0041] The CPU control unit uses a high-speed 8-bit single-chip microcomputer to complete each functional unit module. The CPU control unit includes functions such as reading opening and closing time, monitoring opening and closing operations, collecting synchronous voltage, and starting / stopping the circuit breaker opening / closing control unit connection.

[0042] The device also includes a control panel equipped with a terminal block 5 for connecting external circuits, enabling the circuit breaker opening / closing control unit to be serially connected to the circuit breaker opening / closing control circuit and the synchronous voltage detection unit to be connected to the secondary voltage bus terminal of the A-phase voltage transformer on the power supply side. Specifically, the opening pressure plate 1, closing pressure plate 2, buttons 4, and liquid crystal display 3 are all located on the control panel.

[0043] When the utility model is in use, the overall working principle is as follows:

[0044] 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 have any effect, 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 being out of operation.

[0045] 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 pre-determined circuit breaker opening / closing time is input and saved to the CPU control unit through the button 4 and the LCD display 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 disappears, the CPU control unit disconnects the circuit breaker opening / closing control unit control contact and waits for the next operation.

[0046] 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.

[0047] The principle of closing the circuit breaker without excitation inrush current is divided into the following two cases:

[0048] 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 manually or remotely, this device delays closing so that the closing point is at the highest amplitude of the A-phase voltage, achieving closing without excitation inrush current.

[0049] 2) Closing of power-off transformers that do not require maintenance: When a transformer that does not require maintenance experiences a local / remote power outage, this device delays the power outage so that the power-off point is at the highest point of the A-phase voltage amplitude; when closing the transformer, this device also closes the transformer at the highest point of the A-phase voltage amplitude, achieving closing without excitation inrush current.

[0050] Application of the five-stroke closing test for new transformers / inductors:

[0051] 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 closing without excitation inrush current.

[0052] The last four closing times: When there is a local / remote power outage, the power is delayed by this device so that the power-off point is at the highest point of the voltage amplitude of phase A; when closing, the circuit breaker is also closed at the highest point of the voltage amplitude of phase A through this device, realizing closing without excitation inrush current.

[0053] The utility model has strong versatility and can integrate the same functions into a microcomputer protection device.

Claims

1. An online transformer no-excitation inrush current closing control device, characterized by: The invention 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 with 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 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 pre-determined opening / closing time of the circuit breaker, and a CPU control unit integrating the functions of reading opening / closing time, monitoring opening / closing operation, collecting synchronous voltage, and starting / stopping the connection of the circuit breaker opening / closing control unit; 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 circuit breaker opening / closing control unit.

2. The online-mounted transformer no-excitation inrush current closing control device according to claim 1, characterized in that: The opening / closing control unit includes an opening control contact connected in series to the circuit breaker opening control circuit and a closing control contact connected in series to the circuit breaker closing control circuit; the closing control contact is connected in series to the common entry point of the remote mode closing and local mode closing of the circuit breaker secondary control circuit; the opening control contact is connected in series to the common entry point of the remote mode opening and local mode opening of the circuit breaker secondary control circuit, and is separated from the protection tripping circuit.

3. The online transformer no-excitation inrush current closing control device according to claim 2, characterized in that: The opening / closing control unit is a high-power contact with zero delay.

4. The online-mounted transformer no-excitation inrush current closing control device according to claim 2, characterized in that: The control contacts of the opening / closing control unit are passive contacts that can operate all the time and will not malfunction.

5. The online-mounted transformer no-excitation inrush current closing control device according to claim 2, 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.

6. The online-mounted transformer non-excitation inrush current closing control device according to claim 5, characterized in that: The opening / closing time input unit comprises a key (4) for inputting a pre-determined circuit breaker opening / closing time and a liquid crystal display (3) for realizing opening / closing time display.

7. The online-mounted transformer non-excitation inrush current closing control device according to claim 6, characterized in that: The device further comprises a control panel, on which a terminal block (5) is provided for connecting an external circuit to connect a circuit breaker opening / closing control unit in series with the circuit breaker opening / closing control circuit and to connect a synchronous voltage detection unit to the secondary voltage bus of the A-phase voltage transformer on the power supply side; the opening pressure plate (1), closing pressure plate (2), button (4) and liquid crystal display (3) are all provided on the control panel.

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