A system for calibrating transformer test equipment

Abstract

The present invention relates to a system for calibrating a transformer test device, comprising a control module, an AC voltage output module and a current detection module; the control module is configured to generate a first control signal according to the impedance modulus value of the transformer to be simulated, generate a second control signal according to the phase angle of the transformer to be simulated, and send the first control signal and the second control signal to the AC voltage output module; the AC voltage output module includes a sine function table, a first digital-to-analog conversion module and a second digital-to-analog conversion module, and is configured to output a voltage signal corresponding to the impedance of the transformer to be simulated; the current detection module is configured to acquire the current of the transformer test device to be calibrated and perform feedback control on the AC voltage output module according to the current. The technical solution provided by the present invention can improve the accuracy of calibrating the transformer test device.

Description

Technical Field

[0001] The present invention belongs to the technical field of transformer metering calibration, and particularly relates to a system for calibrating transformer test equipment. Background Art

[0002] At present, the specific process of a transformer test equipment for testing the capacity of a transformer is that the three-phase alternating current output terminals and the alternating voltage measurement terminals of the capacity measurement function part of the test equipment are respectively connected to the high-voltage side wiring terminals of the three-phase transformer, and the low-voltage side of the transformer is short-circuited. When starting the capacity test, the three-phase alternating current of the test equipment is output to the high-voltage side of the transformer. At the same time, the voltage measurement terminals of the test equipment collect the voltage of the high-voltage side of the transformer, and then the test equipment determines the capacity of the transformer. The working principle of the transformer test equipment is to sample the three-phase alternating voltage / current of the high-voltage side of the transformer, calculate the effective values of the three-phase voltage / current and the phase angle between the voltage and the current, and then obtain the actual capacity of the transformer from the capacity calculation formula.

[0003] In order to ensure the accuracy of the test results of transformer equipment, it is necessary to calibrate the transformer test equipment. The problems existing in calibrating the parameters of the transformer test equipment in the prior art are as follows: First, since the output current time of the three-phase current terminals of the capacity test function part of the transformer test equipment is very short (only a few seconds), it is impossible to measure its voltage and current with conventional instruments; Second, if the impedance simulating the actual capacity of the transformer is used for testing, due to the variety of transformers, the impedance and impedance angle of each transformer are different, and it is very difficult to have such an actual impedance in reality; Finally, even if there is such an impedance, since the actual impedance itself will generate heat, it will cause the measured data of the voltage and current to be unstable.

[0004] In summary, it can be seen that there is a problem of poor accuracy of the calibration result when calibrating the transformer test equipment in the prior art. Summary of the Invention

[0005] The present invention provides a system for calibrating transformer test equipment to at least solve the problem of poor accuracy of the calibration result when calibrating the transformer test equipment in the above prior art.

[0006] To solve the above problems, the present invention provides the following technical solutions:

[0007] A system for calibrating a transformer test device, comprising a control module, an AC voltage output module and a current detection module; the control module is configured to generate a first control signal according to the phase angle of a to-be-simulated transformer, generate a second control signal according to the impedance modulus value of the to-be-simulated transformer, and send the first control signal and the second control signal to the AC voltage output module; the AC voltage output module has a sine function table, a first digital-to-analog conversion module and a second digital-to-analog conversion module, and the second digital-to-analog conversion module is configured to send a reference signal to the first digital-to-analog conversion module; the AC voltage output module is configured to: control the first digital-to-analog conversion module according to the first control signal and the sine function table, so that the phase of the voltage signal output by the first digital-to-analog conversion module corresponds to the phase angle of the to-be-simulated transformer; and control the second digital-to-analog conversion module according to the second control signal, so that the amplitude of the voltage signal output by the first digital-to-analog conversion module corresponds to the impedance modulus value of the to-be-simulated transformer; the current detection module is configured to obtain the current of the to-be-calibrated transformer test device, and perform feedback control on the AC voltage output module according to the current.

[0008] According to an embodiment of the present invention, the control module is further connected with a voltage detection module, the voltage detection module is connected to the output end of the AC voltage output module, and is configured to detect the output voltage of the AC voltage output module and send it to the control module, and the control module is further configured to correct the second control signal according to the output voltage.

[0009] According to another embodiment of the present invention, the control module is further connected to the current detection module, and is configured to calculate the detection result of the to-be-calibrated transformer test device according to the detection results of the current detection module and the voltage detection module.

[0010] According to still another embodiment of the present invention, the control module is further connected with a temperature detection module, the temperature detection module is configured to detect the temperature of the to-be-calibrated transformer detection device, and the control module is further configured to correct its detection result according to the temperature of the to-be-calibrated transformer detection device.

[0011] According to another embodiment of the present invention, the current detection module further has a plurality of matching resistors, and the control module is further configured to select the matching resistors connected to the current detection module according to the impedance modulus value of the to-be-simulated transformer.

[0012] According to still another embodiment of the present invention, the control module is further connected with a human-computer interaction device, and the human-computer interaction device is configured to input the impedance angle of the to-be-simulated transformer.

[0013] According to another embodiment of the present invention, the human-computer interaction device includes a touch screen.

[0014] According to another embodiment of the present invention, it further includes a power supply module, and the power supply module is connected to the power supply terminal of the control module for supplying power to the control module.

[0015] According to another embodiment of the present invention, the power supply module includes a power switch. The input end of the power switch is used to connect to the commercial power, and the power switch is used to convert the commercial power into low-voltage direct current.

[0016] According to still another embodiment of the present invention, the control module is further connected with a communication interface, and the communication interface is used to connect to an external device for information interaction with the external device.

[0017] In the technical solution provided by the present invention, the control module can generate corresponding first and second control signals according to the impedance of the analog transformer, and the AC voltage output module can generate an output quantity corresponding to the impedance of the analog transformer to be measured according to the first and second controls. In the technical solution of the present invention, on the one hand, since the AC voltage output module can output an output quantity corresponding to the impedance of the analog transformer according to the first and second control signals of the control module, different transformers can be simulated, and the versatility of the system can be improved; on the other hand, the AC voltage output module is not affected by impedance heating, so the obtained voltage and current data have high stability, and the accuracy of calibrating the transformer test equipment can be improved. Description of the Drawings

[0018] By reading the following detailed description with reference to the drawings, the above and other objects, features, and advantages of the exemplary embodiments of the present disclosure will become readily understood. In the drawings, several embodiments of the present disclosure are shown in an exemplary rather than restrictive manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0019] Figure 1 is a schematic structural diagram of a system for calibrating a transformer test equipment according to an embodiment of the present invention;

[0020] Figure 2 is a schematic structural diagram of an AC voltage output module according to an embodiment of the present invention;

[0021] Figure 3 is a schematic structural diagram of a system for calibrating a transformer test equipment provided with a voltage detection module according to an embodiment of the present invention;

[0022] Figure 4 is a schematic structural diagram of a system for calibrating a transformer test equipment provided with a matching resistor according to an embodiment of the present invention;

[0023] Figure 5Schematic structural diagram of a system for calibrating a transformer testing device with a human-machine exchange module according to an embodiment of the present invention;

[0024] Figure 6 Schematic structural diagram of a system for calibrating a transformer testing device with a power supply module according to an embodiment of the present invention;

[0025] Figure 7 Schematic structural diagram of a system for calibrating a transformer testing device with a communication module according to an embodiment of the present invention. Detailed implementation manners

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the embodiments described in this specification are only some embodiments provided by the present invention for the convenience of clearly understanding the solution and meeting the requirements of the law, rather than all the embodiments that can implement the present invention. All other embodiments obtained by those skilled in the art based on the embodiments disclosed in this specification without creative efforts belong to the scope of protection of the present invention.

[0027] Please refer to Figure 1 , Figure 1 shown is a system for calibrating a transformer testing device of the present invention, and this system can simulate the impedance of a transformer to calibrate the transformer testing device.

[0028] As Figure 1 shown, the system for calibrating a transformer testing device of the present invention includes a control module, an AC voltage output module, and a current detection module. The control module includes a main control chip (i.e., the MCU in Figure 1 ), and this main control chip can be implemented by a logic control device such as an ARM single-chip microcomputer or a DSP single-chip microcomputer. And this main control chip is connected with an encoder, a FLASH ROM, an SDRAM, and a first FPGA chip (i.e., FPGA1 in Figure 1 ) through a bus. The encoder is used to encode the main control chip, the SDRAM and the FLASH ROM are used to store computer instructions, the first FPGA chip is connected with the AC voltage output module and is used to send control signals to the AC voltage output module. And in order to achieve electrical isolation between the control module and the AC voltage output module, a first opto-isolator (such as an opto-coupler) can be set between the first FPGA and the AC voltage output module.

[0029] The AC voltage output module includes an A-phase AC voltage output module, a B-phase AC voltage output module, and a C-phase AC voltage output module. The signal input terminals of the A-phase AC voltage output module, the B-phase AC voltage output module, and the C-phase AC voltage output module are respectively connected to the pins in the first FPGA chip, and the output terminals are respectively connected to the voltage channels of the A-phase test interface, the B-phase test interface, and the C-phase test interface of the transformer test equipment, so as to output test signals to the voltage channels output by the A-phase test interface, the B-phase test interface, and the C-phase test interface respectively. The structures of the above-mentioned A-phase AC voltage output module, B-phase AC voltage output module, and C-phase AC voltage output module are the same, and the A-phase AC voltage output module will be taken as an example for description in the following text.

[0030] As Figure 2 shown, the A-phase AC voltage output module includes a first digital-to-analog conversion module ( Figure 2 DAC1 in Figure 2 ), a second digital-to-analog conversion module ( Figure 1 DAC2 in

[0031] ), a sine function table, an operational amplifier module D1, a resistor R1, a resistor R2, and a first operational amplifier module. The above sine function table has multiple sine functions. After receiving the first control signal from the control module, the sine function corresponding to the first control module can be called from the sine function table, and the starting address of the sine voltage signal output by the first digital-to-analog conversion module can be determined according to the sine function. The reference terminal of the second digital-to-analog conversion module is connected to the first FPGA chip, and the output terminal is connected to the reference terminal of the first digital-to-analog conversion module. The second digital-to-analog conversion module can convert the control signal received from the first FPGA chip from digital quantity to analog quantity and send it to the reference terminal of the first digital-to-analog conversion module to control the amplitude of the voltage signal output by the first digital-to-analog conversion module. The input terminal of the first operational amplifier module is connected to the output terminal of the first digital-to-analog conversion module, and the output terminal is used to connect to the A-phase voltage channel ( Figure 1 DUT1 in Figure 1 of the transformer test equipment, and is used to amplify the signal output by the first digital-to-analog conversion module and send it to the A-phase voltage channel of the transformer test equipment.

[0031] The A current detection module includes a current transformer, a second operational amplifier module, and a first analog-to-digital conversion module. The current transformer is connected to the current channel of the transformer test equipment to be calibrated (i.e., Figure 1 the DUT current channel in Figure 1In the FPGA2), the second FPGA chip is connected to the main control chip through a bus. In order to achieve electrical isolation between the current detection module and the control module, a second opto-isolator (such as an optocoupler) can be set between the second analog-to-digital conversion module and the second FPGA chip. The current transformer in this embodiment can detect the current signal in the current channel of the transformer test equipment to be calibrated and send it to the second operational amplifier module. The first operational amplifier module can send the current signal to the first analog-to-digital conversion module. The first analog-to-digital conversion module can convert the current signal from analog quantity to digital quantity and send it to the second FPGA chip. The second PFGA chip can then send the current signal to the main control chip.

[0032] The working principle of the system provided by the present invention is as follows: The main control chip sends information to the first FPGA according to the impedance modulus value and phase angle of the transformer to be simulated. The first FPGA generates a first control signal according to the phase angle of the transformer to be simulated, generates a second control signal according to the impedance modulus value of the transformer to be simulated, and sends the first control signal to the sine function table and the second control signal to the reference terminal of the second digital-to-analog conversion module. The sine function table determines the starting address of the sine function according to the first control signal, so that the phase of the voltage signal output by the first digital-to-analog conversion module corresponds to the phase angle of the transformer to be simulated; the second digital-to-analog conversion module generates a corresponding reference signal according to the second control signal and inputs it to the reference terminal of the first digital-to-analog conversion module to adjust the amplitude of the voltage signal output by the first digital-to-analog conversion module, so that the amplitude of the voltage signal output by the first digital-to-analog conversion module corresponds to the impedance modulus value of the transformer to be simulated; the first operational amplifier module can amplify the output voltage signal of the first digital-to-analog conversion module to make it consistent with the impedance of the analog transformer.

[0033] In summary, for the technical solution provided by the present invention, the control module can generate corresponding first and second control signals according to the impedance angle of the analog transformer. The AC voltage output module can generate an output quantity corresponding to the impedance of the transformer to be tested according to the first and second controls. Since the AC voltage output module in the present invention is not affected by impedance heating, the obtained voltage and current data have high stability, and the accuracy of calibrating the transformer test equipment can be improved.

[0034] The above text gives an overall introduction to the system for calibrating transformer test equipment of the present invention. Next, in combination with specific application scenarios, the system for calibrating transformer test equipment of the present invention will be further introduced in detail.

[0035] Such as Figure 3As shown, in one embodiment, the system for calibrating a transformer test device of the present invention further includes a voltage detection module, which includes an A-phase voltage detection module, a B-phase voltage detection module, and a C-phase voltage detection module. The A-phase voltage detection module is used to detect the output voltage of the A-phase AC voltage output module, the B-phase voltage detection module is used to detect the output voltage of the B-phase AC voltage output module, and the C-phase voltage detection module is used to detect the output voltage of the C-phase AC voltage output module. Hereinafter, the A-phase voltage detection module will be taken as an example for illustration. In Figure 3 In the structure shown, the voltage detection module includes a sampling resistor, a third operational amplifier module, and a second analog-to-digital conversion module. The sampling resistor is arranged at the output end of the AC voltage output module and is connected in series with a voltage-dividing resistor. The input end of the third operational amplifier module is connected to the sampling resistor, and the output end is connected to the input end of the second analog-to-digital conversion module, which is used to detect the voltage signal across the sampling resistor and perform amplification processing, and then send the amplified voltage signal to the second analog-to-digital conversion module; the output end of the second analog-to-digital conversion module (i.e., Figure 3 the ADC2 in) is connected to the above-mentioned first FPGA chip, which can convert the voltage signal from analog to digital and send it to the first FPGA chip. In order to achieve optoelectronic isolation between the voltage detection module and the control module, a third optoelectronic isolator (such as an optocoupler) can be arranged between the second analog-to-digital conversion module and the first FPGA chip. The first FPGA chip or the control chip can determine whether the amplitude of the voltage signal is consistent with the impedance modulus value of the transformer to be simulated. If not, the second control signal is adjusted to achieve feedback control of the A-phase AC voltage output module.

[0036] In another embodiment, after obtaining the current signal in the current channel of the transformer test device, the main control chip can calculate the impedance of the transformer detected by the transformer test device according to the current signal and the voltage signal at the output end of the AC voltage output module. This impedance is the impedance measurement value. This calculation method belongs to the prior art and will not be described in detail in this embodiment; then, the impedance measurement value is compared with the true value of the impedance of the transformer to be simulated to obtain the error of the transformer test device, so as to obtain the performance of the transformer test device.

[0037] Further, in yet another embodiment, the control module is further connected to a temperature detection module, which is used to detect the temperature of the transformer test device to be calibrated; the control module is also used to correct the impedance of the transformer detected by the transformer measurement device calculated according to the temperature of the transformer test device, so as to improve the accuracy of judging the performance of the transformer test device. Let the set simulated impedance modulus value be Z SET , and the impedance modulus value after temperature correction be |Z|. Among them, the impedance modulus value |Z| is obtained by reverse deduction from the capacity formula, and the set phase angle is φ A, where T is the reference temperature value and t is the temperature value of the transformer detection device to be calibrated. Then

[0038]

[0039] In another embodiment, the current detection module is also connected to the AC voltage output module, and the AC voltage output module is also used to adjust the amplitude of the output AC voltage according to the current detected by the current detection module. Taking the A-phase current detection module as an example, in Figure 4 In the structure shown, the output end of the second operational amplifier module is also connected to the reference end of the second digital-to-analog conversion module. The second digital-to-analog conversion module can adjust the amplitude of the voltage signal output by the first digital-to-analog conversion module according to the output signal of the second operational amplifier module.

[0040] As Figure 5 shown, in one embodiment, the current detection module also has a plurality of matching resistors, and the controller is also used to select a matching resistor according to the modulus value of the impedance of the transformer to be simulated. The matching resistors ( Figure 5 R in) include high-precision resistors with resistance values of 2Ω, 10Ω, 100Ω, and 1KΩ. Each resistor is connected in series between the current transformer and the current channel of the transformer test equipment through a switching switch. The control chip is connected to the switching switch and can deduce the impedance modulus value based on the rated capacity of the transformer to be simulated, and control the switching switch to automatically switch the resistance gear according to the impedance modulus value. When the impedance modulus value is between (0 - 2)Ω, the circuit automatically selects a 2Ω high-precision resistor. When the impedance modulus value is between (2 - 10)Ω, it will switch to a 10Ω high-precision resistor, and so on. There are mainly two reasons for selecting these four high-precision resistors. One is that the resistors themselves have high precision and small temperature drift, ensuring the stability of data and the accuracy of current measurement. The other is that the four resistors are divided into grades, making the impedance of the current measurement channel closer to the actual impedance of the transformer, so that the measured current is also closer to the actual current during the capacity test of the transformer, and at the same time ensuring that the voltage output by the voltage channel can always be between (1 - 10)V, ensuring the accuracy of the output voltage.

[0041] As Figure 5 shown, in one embodiment, the control module of the present invention is also connected to a human-computer interaction device, and the human-computer interaction device can be a touch screen or devices such as a keyboard, mouse, and display. The human-computer interaction device is connected to the main control chip in the control module. The user can perform human-computer interaction with the control module through the human-computer interaction. For example, the user can input information such as the impedance angle of the transformer to be simulated through the touch screen, and the control module controls the AC voltage output module according to this information; the control module can also display the calculated impedance angle on the touch screen or the display for the user to view.

[0042] In one embodiment, the system for calibrating a transformer test device of the present invention further includes a power supply module. The power supply module can use a storage battery, and the power supply module is connected to the power supply terminal of the controller to supply power to the controller.

[0043] As Figure 6 shown, in another embodiment, the power supply module may include a power switch. The input terminal of the power switch is connected to the commercial power, and is used to convert the 220V commercial power into ±24V direct current. The output terminal of the power switch is connected to the input terminals of a first DC / DC converter, a second DC / DC converter, and a third DC / DC converter. The output terminal of the first DC / DC converter is connected to the power supply terminals of the ADC device and the DAC device in the system, and is used to convert the ±24V direct current into ±8V direct current and supply power to the analog-to-digital conversion module and the digital-to-analog conversion module devices; the output terminal of the second DC / DC converter is connected to the power supply terminal of the operational amplifier module in the system, and is used to convert the ±24V direct current into ±15V direct current to supply power to the operational amplifier module; the output terminal of the third DC / DC converter is connected to the voltage power supply terminals of the main control chip, the first FPGA chip, and the second FPGA chip, and is used to convert the ±24V direct current into ±5V direct current to supply power to the main control chip, the first FPGA chip, and the second FPGA chip.

[0044] As Figure 7 shown, in one embodiment, the control module further includes a communication interface. The communication interface may include one or more of a USB interface, an RS232 interface, and a LAN interface. The main control chip is connected to the communication interface and can be connected to an external device through the communication interface to interact with the external device. For example, after calculating the modulus value of the analog impedance, it can be sent to the external device, or information can be received from the external device or a program can be burned, etc.

[0045] The terms "first", "second", or "third", etc. used in this specification to refer to numbered or ordinal terms are only for descriptive purposes and cannot be construed as explicitly or implicitly indicating relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", or "third" may explicitly or implicitly include at least one of such features. In the description of this specification, the meaning of "a plurality" is at least two, such as two, three, or more, etc., unless otherwise specifically defined.

[0046] Although this specification has shown and described multiple embodiments of the present invention, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Those skilled in the art will think of many changes, alterations, and alternative ways without departing from the spirit and concept of the present invention. It should be understood that various alternatives of the embodiments of the present invention described herein can be adopted in the practice of the present invention. The appended claims are intended to define the scope of protection of the present invention and thus cover the device components, equivalents, or alternatives within the scope of protection of these claims.

Claims

1. A system for calibrating transformer test equipment, characterized in that, It includes a control module, an AC voltage output module and a current detection module; The control module is used to generate a first control signal according to the phase angle of the transformer to be simulated, generate a second control signal according to the modulus of the impedance of the transformer to be simulated, and send the first control signal and the second control signal to the AC voltage output module; The AC voltage output module has a sine function table, a first digital-to-analog conversion module and a second digital-to-analog conversion module. The second digital-to-analog conversion module is used to send a reference signal to the first digital-to-analog conversion module. The AC voltage output module is used to: control the first digital-to-analog conversion module according to the first control signal and the sine function table, so that the phase of the voltage signal output by the first digital-to-analog conversion module corresponds to the phase angle of the transformer to be simulated; and control the second digital-to-analog conversion module according to the second control signal, so that the amplitude of the voltage signal output by the first digital-to-analog conversion module corresponds to the modulus of the impedance of the transformer to be simulated; The current detection module is used to obtain the current of the transformer test equipment to be calibrated and perform feedback control on the AC voltage output module according to the current.

2. The system for calibrating a transformer test device according to claim 1, wherein The control module is also connected with a voltage detection module. The voltage detection module is connected to the output end of the AC voltage output module and is used to detect the output voltage of the AC voltage output module and send it to the control module. The control module is also used to correct the second control signal according to the output voltage.

3. The system for calibrating a transformer test device according to claim 2, wherein The control module is also connected to the current detection module and is used to calculate the detection result of the transformer test equipment to be calibrated according to the detection results of the current detection module and the voltage detection module.

4. The system for calibrating a transformer test device according to claim 3, wherein The control module is also connected with a temperature detection module. The temperature detection module is used to detect the temperature of the transformer detection equipment to be calibrated. The control module is also used to correct its detection result according to the temperature of the transformer detection equipment to be calibrated.

5. The system for calibrating a transformer test device according to claim 1, characterized in that, The current detection module also has a plurality of matching resistors. The control module is also used to select the matching resistors connected to the current detection module according to the modulus of the impedance of the transformer to be simulated.

6. The system for calibrating a transformer test device according to claim 1, wherein The control module is also connected with a human-computer interaction device. The human-computer interaction device is used to input the impedance angle of the transformer to be simulated.

7. The system for calibrating a transformer test device according to claim 6, wherein The human-computer interaction device includes a touch screen.

8. The system for calibrating a transformer test device according to claim 1, wherein, It also includes a power supply module. The power supply module is connected to the power supply end of the control module and is used to supply power to the control module.

9. The system for calibrating a transformer test device according to claim 8, wherein, The power supply module includes a power switch. The input end of the power switch is used to connect to the mains. The power switch is used to convert the mains into low-voltage direct current.

10. The system for calibrating a transformer test device according to claim 1, wherein, The control module is also connected with a communication interface. The communication interface is used to connect to an external device to perform information interaction with the external device.

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