A transformer energy efficiency detection device and detection method with optimized non-linear zero-crossing points

Abstract

The present invention relates to a transformer energy efficiency detection device and detection method with optimized non-linear zero-crossing points, belonging to the technical field of power equipment detection. The device is composed of a three-phase fixed-frequency power supply, an integrated wiring module, and a detection system module. The integrated wiring module includes a controller, a MOSFET switch, a 1 kV switch, and a 10 kV switch. The detection system module is composed of an electrical parameter measurement module, a central processor, a power supply voltage and current control module, and a temperature sensor. The central processor includes a microprocessor, a data optimization module, and an over-current threshold database. The implementation of its detection method includes five steps. The over-current threshold database realizes over-current protection. The integrated wiring module realizes rapid switching and detection of the test wiring for no-load and load losses. The one-key process control of the detection system module enables simultaneous detection of multiple different types of transformers. The central processor realizes the non-linear zero-crossing point optimization method, without setting a zero-crossing point detection circuit, with good optimization effect, strong anti-interference ability and safety, and high detection efficiency and accuracy.

Description

Technical Field

[0001] The present invention relates to a transformer energy efficiency detection device and a detection method with optimized non - linear zero - crossing points, belonging to the technical field of power equipment detection. Background Art

[0002] Reducing the power loss of distribution transformers can save a large amount of energy. Therefore, accurately determining the energy efficiency level of transformers is crucial for timely detecting and upgrading high - energy - consuming transformers. Currently, for the energy efficiency level detection of power transformers, neither independent project test instruments nor fixed test equipment is equipped with transformer short - circuit protection. When actually detecting the energy efficiency of transformers, accidents that are likely to burn out transformers and endanger the safety of test personnel are very likely to occur. Independent project test instruments need to use a combination of various test equipment, which is prone to wiring errors, resulting in inaccurate measurement results, and even damaging the measuring instruments and the transformers under test. Moreover, due to the dispersion of test instruments and measurement data, manual recording of test results is required multiple times, which is prone to recording errors, seriously reducing the credibility of test results. At the same time, the cumbersome detection steps also greatly reduce the detection efficiency. Fixed test equipment is bulky and not specifically designed for detecting the energy efficiency level of transformers. There is a lot of non - effective test content, and the disconnection and connection of wires are cumbersome. When detecting, each transformer needs to be hoisted and transported sequentially. After one transformer test is completed, another transformer can be moved in. It takes at least 30 minutes to complete the energy efficiency level test of a single transformer, and the detection efficiency is extremely low. There are also safety risks and it cannot undertake the heavy task of detecting the energy efficiency levels of a large number of transformers.

[0003] Transformer energy efficiency detection methods are related to the accuracy of measurement data. Currently, the following two methods are usually adopted: one is the analog measurement method, and the other is the sampling measurement method. The sampling measurement method includes the DC sampling measurement method and the AC sampling measurement method. The analog measurement method is easy to implement, but has low accuracy and single function, and cannot achieve real - time measurement of multiple electrical parameters. The DC sampling measurement method has a simple design and convenient and fast calculation, but the measurement accuracy is not high, the real - time performance is poor, and in the case of harmonic pollution, the measurement accuracy is generally not high and cannot reach the accuracy required for transformer energy efficiency detection. The AC sampling measurement method samples the instantaneous value of the signal at a certain period, and then obtains the values of various electrical parameters through numerical calculation. Different algorithms such as the zero - crossing point algorithm, fast Fourier transform, wavelet transform, neural network, frequency measurement algorithm based on the equal - ratio principle, and smooth weighted phase difference method can be used to analyze and detect harmonics. Among them, the zero - crossing point algorithm has a relatively simple principle, but is only applicable to static systems with constant frequency. The calculation result completely depends on the measurement value at the zero - crossing moment, and this measurement value is easily affected by power grid harmonics and faults. For AC voltage zero - crossing detection, a special zero - crossing detection circuit needs to be designed, with high hardware costs, and the components of the detection circuit cannot fully reach the ideal level, and errors will also be introduced during the detection process, affecting the measurement accuracy. Summary of the Invention

[0004] The purpose of the present invention is to provide a transformer energy efficiency detection device and a detection method with nonlinear zero-crossing optimization in view of the deficiencies of the above-mentioned prior art. The device of the present invention is provided with an overcurrent protection threshold database and an integrated wiring module to realize real-time monitoring of the voltage and current values of the transformer under test and compare them with the overcurrent protection threshold database, effectively prevent overcurrent from occurring during the test process, and effectively protect the safety of the transformer under test, the device and the test personnel; the device of the present invention realizes centralized and rapid switching and detection of no-load loss and load loss of transformers of different models through an integrated wiring module, realizes centralized and corresponding display of detection data, avoids time-consuming disconnection and wiring and errors in manual scattered recording, and has the functions of automatic voltage rise and fall, temperature detection and transformer no-load power detection, which fully meets the requirements for batch energy efficiency grade detection of transformers.

[0005] The detection method of the present invention realizes AC voltage zero-crossing point detection by improving the zero-crossing point data processing algorithm, and data optimization can be completed without designing a zero-crossing point detection circuit, thereby improving the data optimization effect by nearly 20 times, effectively saving hardware costs, and having strong anti-interference ability. The data error is reduced by 10 times compared with the traditional zero-crossing point detection method, and the optimized data is close to the true value, which greatly improves the accuracy of transformer energy efficiency grade detection.

[0006] The present invention achieves the above-mentioned object through the following technical solutions:

[0007] A transformer energy efficiency detection device and detection method with nonlinear zero-crossing optimization, characterized in that: the transformer energy efficiency detection device with nonlinear zero-crossing optimization is composed of a three-phase fixed-frequency power supply, an integrated wiring module and a detection system module, the three-phase fixed-frequency power supply is connected to the transformer through the integrated wiring module, the three-phase fixed-frequency power supply and the integrated wiring module are respectively connected to the detection system module, so as to realize the automatic switching of the transformer no-load loss test and load loss test wiring and the collection of test data; the integrated wiring module includes a controller, a metal-oxide semiconductor field effect tube switch, a 1kV vacuum AC contactor switch, and a 10kV vacuum AC contactor. The detection system module consists of an electrical parameter measurement module, a central processing unit, a power supply voltage and current control module and a temperature sensor; the electrical parameter measurement module includes a three-phase voltage and current sensor, a signal conditioning circuit and an A / D converter, and the central processing unit includes a microprocessor, an LCD display, a data optimization module and an over-current threshold database; the electrical parameter measurement module is connected to the central processing unit to complete the acquisition, correction, conversion and transmission of analog electrical signals; the power supply voltage and current control module is connected to the microprocessor to control the output of the three-phase fixed-frequency power supply; the temperature sensor is connected to the microprocessor to collect the temperature parameters of the transformer.

[0008] The controller of the integrated wiring module outputs three signals to control respectively the on and off of the metal-oxide-semiconductor field effect transistor switch, the 1 kV vacuum AC contactor switch, and the 10 kV vacuum AC contactor switch, meeting the wiring requirements for no-load loss test and load loss test, and eliminating the need to manually disconnect and reconnect the lines during no-load loss test and load loss test. During no-load loss test: the controller controls the metal-oxide-semiconductor field effect transistor switch to close, and the 1 kV vacuum AC contactor switch and the 10 kV vacuum AC contactor switch to open, forming a wiring for no-load loss test with three-phase voltage applied to the low-voltage side of the transformer and the high-voltage side open. During load loss test: the controller controls the metal-oxide-semiconductor field effect transistor switch to open, and the 1 kV vacuum AC contactor switch and the 10 kV vacuum AC contactor switch to close, forming a wiring for load loss test with three-phase voltage applied to the high-voltage side of the transformer and the low-voltage side short-circuited.

[0009] The three-phase voltage and current sensors of the electrical parameter measurement module collect electrical parameters during no-load loss test and load loss test. The voltage and current measurement accuracy levels are 0.1 level, meeting the requirements of national and industry standards. The signal conditioning unit combines the measured values of the three-phase voltage and current sensors with the non-linear zero-crossing optimization algorithm to automatically correct the test data, greatly improving the accuracy of the measured values. The A / D converter converts the analog electrical signal calibrated by the signal conditioning unit into a digital signal and inputs it into the central processor to complete data transmission.

[0010] The microprocessor of the central processor communicates with the LCD display screen to achieve the control, data analysis and calculation, and human-machine interaction of the entire device system. The data optimization module realizes the non-linear zero-crossing optimization of the measured values of the three-phase voltage and current sensors through the microprocessor in combination with the over-current threshold database, automatically correcting the test data, making the detected voltage amplitude and frequency approach the ideal values. Compared with the traditional zero-crossing detection method, the measurement voltage amplitude error is reduced by 48 times, and the frequency error is reduced by 10 times, greatly reducing the error, enhancing the anti-interference ability of the device, and improving the accuracy of the measured values. The over-current threshold database is set with the following data columns: the first column records the transformer material, the second column records the rated capacity of the transformer, the third column records the rated high-voltage side voltage, the fourth column records the rated low-voltage side voltage, the fifth column records the connection group number, the sixth column records the no-load loss, the seventh column records the load loss, the eighth column records the short-circuit impedance, the ninth column records the no-load current, the tenth column records the no-load test current limit value, the eleventh column records the load test reference voltage value. Each row of the over-current threshold database represents a type of transformer. The connection group number is the connection method of the high-voltage winding and the low-voltage winding of the transformer. The no-load test current limit value is 1.5 times the rated no-load current value of the transformer. The load test reference voltage value is 0.85 times the impedance voltage value of the transformer.

[0011] The described three-phase voltage and current sensor and the central processor form an experimental overcurrent protection module. The magnitude of the current detected by the three-phase voltage and current sensor is transmitted to the central processor. By comparing it with the overcurrent threshold database in the central processor, it is determined whether the current signal exceeds the limit value. If it exceeds the limit value, the central processor controls the experiment to stop; otherwise, the experiment continues.

[0012] The overcurrent threshold database is set with no-load experiment current limit values and load experiment reference voltage values. During the no-load test, the microprocessor sets the no-load experiment current limit value and monitors the current value of the transformer under test in real time through the three-phase voltage and current sensor. Once its current value is greater than the no-load experiment current limit value, the microprocessor cuts off the three-phase fixed-frequency power supply through the power supply voltage and current control module to protect the safety of the transformer under test, the energy efficiency detection device, and the test personnel. During the load test, the microprocessor sets the load experiment reference voltage value and monitors the voltage and current values of the transformer under test in real time through the three-phase voltage and current sensor, enabling the voltage to rise rapidly to the set voltage. After reaching the set voltage, the microprocessor controls the power supply voltage and current control module to change the voltage in small steps until the experimental current reaches the rated current of the transformer, greatly shortening the detection time.

[0013] The described power supply voltage and current control module receives the central processor control signal and completes the automatic adjustment of the output voltage and current of the three-phase fixed-frequency power supply, improving the detection efficiency.

[0014] Multiple temperature sensors are installed to achieve distributed real-time temperature detection. The average temperature is selected as the temperature for the transformer DC resistance detection and the load loss test respectively, improving the accuracy of the measurement data.

[0015] The described controller is respectively connected to the metal-oxide semiconductor field effect transistor switch, the 1 kV vacuum AC contactor switch, and the 10 kV vacuum AC contactor switch to control the on-off states of the three switches. The upper end of the metal-oxide semiconductor field effect transistor switch is connected to the first group of the low-voltage side of the transformer through a bushing, and the lower end is connected to the three-phase fixed-frequency power supply through an electrical compartment. When the metal-oxide semiconductor field effect transistor switch is closed, the first group of the low-voltage side of the transformer is powered by the three-phase fixed-frequency power supply. The upper end of the 1 kV vacuum AC contactor switch is connected to the second group of the low-voltage side of the transformer through a bushing, and the lower end is short-circuited through the copper bar in the electrical compartment. When the 1 kV vacuum AC contactor switch is closed, the low-voltage side of the transformer is short-circuited. The upper end of the 10 kV vacuum AC contactor switch is connected to the third group of the high-voltage side of the transformer through a bushing, and the lower end is connected to the three-phase fixed-frequency power supply through an electrical compartment. When the 10 kV vacuum AC contactor switch is closed, the high-voltage end of the transformer is powered by the three-phase fixed-frequency power supply. When the 10 kV high-voltage power supply switch is closed, the three-phase fixed-frequency power supply circuit of the 10 kV vacuum AC contactor switch is connected.

[0016] A detection method for a transformer energy efficiency detection device with optimized non-linear zero-crossing points, characterized in that: the transformer energy efficiency detection device with optimized non-linear zero-crossing points is composed of a three-phase fixed-frequency power supply, an integrated wiring module, and a detection system module. The three-phase fixed-frequency power supply is connected to the transformer through the integrated wiring module, and the three-phase fixed-frequency power supply and the integrated wiring module are respectively connected to the detection system module to realize the automatic switching of the wiring for the no-load loss test and the load loss test of the transformer and the acquisition of test data. The integrated wiring module includes a controller, a metal-oxide semiconductor field effect transistor switch, a 1 kV vacuum AC contactor switch, a 10 kV vacuum AC contactor switch, and a 10 kV high-voltage power supply switch. The detection system module is composed of an electrical parameter measurement module, a central processor, a power supply voltage and current control module, and a temperature sensor. The electrical parameter measurement module includes three-phase voltage and current sensors, a signal conditioning circuit, and an A / D converter. The central processor includes a microprocessor, an LCD display screen, a data optimization module, and an over-current threshold database. The electrical parameter measurement module is connected to the central processor to complete the acquisition, correction, conversion, and transmission of analog electrical signals. The power supply voltage and current control module is connected to the microprocessor to control the output of the three-phase fixed-frequency power supply. The temperature sensor is connected to the microprocessor to collect the temperature parameters of the transformer. The detection method is realized through the following steps:

[0017] Step 1. When batch-detecting different types of transformers, first detect the DC resistance and record the temperature of the current detection environment.

[0018] Step 2. Set the working parameters of the no-load loss test and the load loss test through the setting interface of the detection system module, input the corresponding DC resistance value, and adjust the voltage and current output by the three-phase fixed-frequency power supply through the power supply voltage and current control module to meet the requirements of the transformer no-load and load loss tests. For the no-load test, detect with the rated voltage. For the load test, detect in the full-current mode. The detection data in the full-current mode of the load test does not need to be converted and can be directly calculated using the transformer energy efficiency detection formula to ensure the detection accuracy.

[0019] Step 3. Through the microprocessor, data optimization module, and over-current threshold database of the central processor, construct a non-linear zero-crossing point optimization model to realize the automatic correction of the detection data of the three-phase voltage and current sensors, ensuring good anti-interference performance and high-precision detection effect. The construction method of the non-linear zero-crossing point optimization model is as follows:

[0020] 3.1) Obtain the maximum value Umax and the minimum value Umin of the collected signal, Vpp = Umax - Umin, and calculate Vpp / 2 as the rough estimated value Un of the amplitude.

[0021] 3.2) Use the zero-crossing detection method to determine the phase φ0 and the rough estimated value T0 of the period of the sine wave signal.

[0022] 3.3) Establish the objective function, obtain the correction parameter x, and optimize the measurement data;

[0023] The specific operations are as follows:

[0024] 3.3.1) Establish the objective function

[0025] The detected sine waveform under ideal conditions satisfies u = U n sin(t / T + φ), and the following objective function is established:

[0026]

[0027]

[0028] where i is the number of sampling points, and t i and u i are the sampling time and sampling value respectively; the function g is defined as the sum of squares of the differences between the actual measured values and the corresponding values calculated according to the set sine function mathematical model. When the function g has a minimum value, the sine function is closest to the ideal value, that is, the test data is more accurate after non-linear optimization;

[0029] 3.3.2) Solve the above objective function by using the Newton iteration method;

[0030] Let The linearized equation of f(x) is expressed as:

[0031]

[0032] where x0 is the set initial value;

[0033] When , the function reaches an extreme value, that is

[0034]

[0035]

[0036] 3.3.3) Obtain the correction parameter x. At this time, the △x obtained by using formula (5) and the initial value x0 can be used to solve the correction parameter x through the formula x = x0 + △x. Substitute x into the function g to find the value of g(x); substitute the previously solved x as the initial value into formula (5) to solve △x, and repeat the above process until the value of g(x) is greater than the previous x value, then stop the whole process. The previously obtained x value is the data after non-linear zero-crossing optimization. At this time, the objective function is closest to the ideal value, that is, the most accurate;

[0037] Step 4, one-click detection starts, and the central processor automatically remotely controls the logic switching of the metal-oxide semiconductor field effect tube switch, 1kV vacuum AC contactor switch and 10kV vacuum AC contactor switch of the power supply and the integrated wiring module to realize automatic detection of the transformer no-load; the central processor controls the integrated wiring module to automatically complete the no-load loss test wiring of the transformer, obtains the voltage and current test data through the three-phase voltage and current sensor, and automatically corrects the test data through the signal conditioning unit combined with the nonlinear zero-crossing optimization method to ensure the accuracy of the detection data; the corrected test data is converted into a signal through the A / D converter and transmitted to the central processor, and the rated no-load loss is directly calculated by the central processor; during the transformer load test, the integrated wiring module is controlled by the controller to automatically complete the switching of the transformer load loss test wiring, and the voltage and current data and temperature parameters are obtained and corrected through the electrical parameter measurement module, and then transmitted to the central processor, and the rated load loss and short-circuit impedance are calculated using the energy efficiency data calculation formula;

[0038] Step 5: Use the central processing unit to aggregate, display and generate test data reports.

[0039] The beneficial effects of the present invention compared with the prior art are:

[0040] A transformer energy efficiency detection device and detection method with nonlinear zero-crossing optimization, by setting an overcurrent protection threshold database including no-load test current limit value and load test reference voltage value, to achieve real-time monitoring of the voltage and current values of the transformer under test and the overcurrent protection threshold database, effectively prevent overcurrent from occurring during the test process, and effectively protect the safety of the transformer under test, the device and the test personnel; through an integrated wiring module, fast switching and detection of no-load loss and load loss test wiring of transformers of different models can be achieved, and the detection data can be displayed in a centralized manner to avoid manual wiring errors and manual scattered recording errors; through the detection system module, one-button operation, programmed process control, automatic test report generation, simple operation, and multiple Different types of transformers can be tested simultaneously, and the testing time for a single unit does not exceed 10 minutes, which greatly improves the efficiency of transformer energy efficiency level testing. Compared with the traditional AC voltage zero-crossing method, the nonlinear zero-crossing optimization data processing algorithm is implemented through the central processor, and there is no need to preset the zero-crossing detection circuit, which effectively saves hardware costs and improves the data optimization effect by nearly 20 times. It has strong anti-interference ability and high detection data accuracy, which fully meets the requirements of national standards and industry standards. By comparing the input parameters of the three-phase voltage and current sensors with the overcurrent protection threshold database, adaptive overcurrent protection is achieved, and real-time monitoring of the current of the transformer being tested in the energy efficiency test is achieved to prevent large currents, improve the safety of the entire device system, and effectively ensure the safety of the transformer being tested and the testing personnel. The invention solves the problems that the existing energy efficiency testing equipment has no transformer short-circuit protection device, and the overcurrent threshold database lacks no-load test current limit value and load test reference voltage value settings, cannot prevent overcurrent phenomenon in the detection process, cannot protect the safety of the tested transformer, equipment and test personnel, cannot realize fast switching and detection of no-load loss and load loss test wiring of transformers of different models, cannot avoid time-consuming disconnection and errors in manual scattered records, and does not have automatic voltage rise and fall, temperature detection and transformer no-load power detection functions, making it difficult to meet the requirements of transformer batch energy efficiency grade detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a block diagram of the working principle of the present invention;

[0042] Figure 2 It is a schematic diagram of the working principle structure of the integrated wiring module of the present invention;

[0043] Figure 3 It is a circuit wiring diagram of the integrated wiring module of the present invention;

[0044] Figure 4 It is a schematic diagram of the installation structure of the present invention;

[0045] Figure 5It is a comparison result diagram of the sampling signals detected by the non - linear zero - crossing optimization algorithm and the zero - crossing method of the present invention;

[0046] Figure 6 It is a comparison result diagram of the voltage amplitudes detected by the non - linear zero - crossing optimization algorithm and the zero - crossing method of the present invention;

[0047] Figure 7 It is a comparison result diagram of the voltage frequencies detected by the non - linear zero - crossing optimization algorithm and the zero - crossing method of the present invention.

[0048] In the figure: 1. Three - phase fixed - frequency power supply, 2. Integrated wiring module, 3. Detection system module, 4. Transformer, 5. Bushing a, 6. Bushing b, 7. Bushing c, 8. Electrical cubicle;

[0049] 20. Controller, K1. Metal - oxide semiconductor field - effect transistor switch, K2. 1kV AC contactor switch, K3. 10kV AC contactor switch, K4. 10kV high - voltage power supply switch;

[0050] 30. Electrical parameter measurement module, 300. Three - phase voltage and current sensor, 301. Signal conditioning circuit, 302. A / D conversion circuit;

[0051] 31. Central processing unit, 310. Microprocessor, 311. LCD display screen, 312. Data optimization module, 313. Over - current threshold database;

[0052] 32. Power supply voltage and current control module, 33. Temperature sensor;

[0053] V1. Ideal sine - wave waveform, V2. Signal waveform measured by traditional zero - crossing method, V3. Signal waveform measured by non - linear zero - crossing optimization method;

[0054] V4. Ideal value of voltage amplitude, V5. Measured value of voltage amplitude by non - linear zero - crossing optimization method, V6. Measured value of voltage amplitude by traditional zero - crossing detection method;

[0055] f1. Ideal value of signal frequency, f2. Measured value of signal frequency by non - linear zero - crossing optimization method, f3. Measured value of signal frequency by traditional zero - crossing detection method. Specific embodiments

[0056] The following further elaborates on the specific embodiments of the transformer energy - efficiency detection device and detection method with non - linear zero - crossing optimization in conjunction with the accompanying drawings (see Figures 1-7 ):

[0057] A transformer energy efficiency detection device with optimized non-linear zero-crossing points, characterized in that it includes a three-phase fixed-frequency power supply 1, an integrated wiring module 2 and a detection system module 3. The three-phase fixed-frequency power supply 1 is connected to a transformer 4 through the integrated wiring module 2 for the test power supply. The integrated wiring module 2 and the three-phase fixed-frequency power supply module 1 are respectively connected to the detection system module 3 for automatic switching of the wiring for no-load loss test and load loss test of the power transformer 4 and for acquisition of test data.

[0058] The three-phase fixed-frequency power supply 1 is used for the test power supply and system power supply, inputs a 50Hz, 220V single-phase sine wave voltage, and outputs a 50Hz, three-phase sine wave with continuously adjustable voltage of 0 - 450V through power electronic conversion for use as the test power supply. The integrated wiring module 2 is used to switch the wiring for no-load loss test and load loss test of the transformer 4. Since the wiring of the transformer 4 for no-load test and load test is different, in the traditional test process, the operation of manually removing and connecting the lines is cumbersome and time-consuming. The integrated wiring module 2 greatly improves the energy efficiency detection efficiency.

[0059] The integrated wiring module 2 includes a controller 20, a metal-oxide semiconductor field effect transistor switch K1, a 1kV AC contactor switch K2, a 10kV AC contactor switch K3 and a 10kV high-voltage power supply switch K4. The controller 20 outputs three signals to respectively control the on and off of the metal-oxide semiconductor field effect transistor switch K1, the 1kV AC contactor switch K2 and the 10kV AC contactor switch K3. The metal-oxide semiconductor field effect transistor switch K1 realizes the on and off of the switch by controlling the voltage between the control gate and the source. The 1kV AC contactor switch K2 and the 10kV AC contactor switch K3 utilize the cooperation of electromagnetic force and spring elastic force to realize the on and off of the contacts.

[0060] The current and voltage generated during no-load loss test are very small. The metal-oxide semiconductor field effect transistor switch K1 is designed with MOSFET to allow small current to pass through, greatly reducing the switch volume. The 1kV AC contactor switch K2 and the 10kV AC contactor switch K3 are designed with AC contactors, which can withstand high voltage and allow large current to pass through, meeting the requirements of the load loss detection experiment (see Figures 1-3 ).

[0061] When actually assembling this device, the upper end of the metal-oxide semiconductor field-effect transistor switch K1 is connected to the first group of the low-voltage side of the transformer 4 through the a sleeve 5, and the lower end is connected to the three-phase fixed-frequency power supply 1 through the electrical compartment 8. When the metal-oxide semiconductor field-effect transistor switch K1 is closed, the first group of the low-voltage side of the transformer 4 is powered by the three-phase fixed-frequency power supply 1; the upper end of the 1kV AC contactor switch K2 is connected to the second group of the low-voltage side of the transformer 4 through the b sleeve 6, and the lower end is short-circuited through the copper bar inside the electrical compartment 8. When the 1kV AC contactor switch K2 is closed, the low-voltage side of the transformer 4 is short-circuited; the upper end of the 10kV AC contactor switch K3 is connected to the high-voltage side of the transformer 4 through the c sleeve 7, and the lower end is connected to the three-phase fixed-frequency power supply 1 through the electrical compartment 8. When the 10kV AC contactor switch K3 is closed, the high-voltage end of the transformer 4 is powered by the three-phase fixed-frequency power supply 1; the 10kV high-voltage power supply switch K4 provides a working power supply circuit for the 10kV AC contactor switch K3 (see Figure 3 、 Figure 4 ).

[0062] For the convenience of description, hereinafter, the metal-oxide semiconductor field-effect transistor switch K1, the 1kV AC contactor switch K2, and the 10kV AC contactor switch K3 will be simply referred to as: MOSFET switch K1, 1kV switch K2, 10kV switch K3;

[0063] During no-load loss testing: (The test method for the rated no-load loss is to apply a three-phase sine wave with the rated frequency and rated voltage from the low-voltage winding side of the transformer 4, and the high-voltage winding is open); the controller 20 controls the MOSFET switch K1 to close, and the 1kV switch K2 and the 10kV switch K3 to open, so as to apply a three-phase voltage on the low-voltage side of the transformer 4 and keep the high-voltage side open, forming a wiring for detecting the no-load loss of the transformer 4.

[0064] During load loss testing: (The test method for the rated load loss is to apply a voltage on the high-voltage winding side of the transformer 4 and short-circuit the low-voltage side); the controller 20 controls the MOSFET switch K1 to open, and the 1kV switch K2 and the 10kV switch K3 to close, so as to apply a three-phase voltage on the high-voltage side of the transformer 4 and short-circuit the low-voltage side of the transformer 4, that is, forming a wiring for detecting the load loss of the transformer 4 (see Figures 2-4 ).

[0065] The detection system module 3 is used to conduct no-load loss tests and load loss tests on the transformer 4; it controls the integrated wiring module 2 to automatically switch the no-load and load test wiring, simplifies the experimental operation, and realizes the programmed process control of one-key operation, automatic testing, and report generation; the detection system module 3 consists of an electrical parameter measurement module 30, a central processor 31, a power supply voltage and current control module 32, and a temperature sensor 33; the electrical parameter measurement module 30 consists of three-phase voltage and current sensors 300, a signal conditioning unit 301, and an A / D converter 302, and the central processor 31 includes a microprocessor 310, an LCD display screen 311, a data optimization module 312, and an overcurrent threshold database 313 (see Figure 1 ).

[0066] The three-phase voltage and current sensors 300 are connected to the central processor 31 via the signal conditioning unit 301 and the A / D converter 302 to complete the acquisition, correction, conversion, and transmission of analog electrical signals; the power supply voltage and current control module 32 and the temperature sensor 33 are respectively connected to the microprocessor 310 and are used to collect the temperature parameters of the transformer 4 and control the output of the three-phase constant-frequency power supply 1; the microprocessor 310 communicates with the LCD display screen 311 to realize the control of the entire device system, data analysis and calculation, and human-machine interaction (see Figure 1 ).

[0067] The three-phase voltage and current sensors 300 are used to collect the electrical parameters during no-load loss tests and load loss tests. The three-phase voltage and current sensors 300 are connected to the transformer 4 to be measured through insulating bushings to measure the electrical parameters for energy efficiency detection, and their voltage and current measurement accuracy levels are both 0.1 level, meeting the requirements of national and industry standards.

[0068] The signal conditioning unit 301 is used for the calibration of electrical parameters. The signal conditioning unit 301 combines the measurement values of the three-phase voltage and current sensors 300 with the non-linear zero-crossing optimization mathematical algorithm of the data optimization module 312 to automatically correct the test data, greatly improving the accuracy of the detection values.

[0069] The A / D converter 302 is used for the conversion between analog electrical signals and digital electrical signals. The A / D converter 302 converts the analog electrical signals calibrated by the signal conditioning unit 301 into digital signals and inputs them into the central processor 31 to complete the data transmission.

[0070] The LCD display screen 311 is used for human-machine interaction and energy efficiency report display. It receives key information through the control circuit of the LCD display screen 311, issues corresponding detection instructions and control signals to the microprocessor 310, controls the integrated wiring module 2 to complete automatic wiring, obtains corresponding detection data through the electrical parameter measurement unit 30, obtains calibration data after calibrating the detection data, and obtains calibration data after calculation by the microprocessor 310. Finally, it determines the energy efficiency level of the transformer 4, generates an energy efficiency level test report of the transformer 4, and displays it through the LCD display screen 311.

[0071] The power supply voltage and current control module 32 is used to control the output of the three-phase fixed-frequency power supply 1. The power supply voltage and current control module 32 receives the control signal of the central processor 31, completes the automatic adjustment of the output voltage and current of the three-phase fixed-frequency power supply 1, and improves the detection efficiency.

[0072] The temperature sensor 33 is used to measure the temperature parameters of the transformer 4. The temperature sensor 33 with the model DS18B20 is installed at multiple locations of the transformer 4 to achieve distributed temperature detection, obtain the average value of the real-time sampling values of the temperatures at multiple locations, and use them as the temperatures during the DC resistance measurement and load loss detection of the transformer 4 respectively, so as to improve the accuracy of the measurement data.

[0073] The microprocessor 310 is used for data processing and calculation of no-load and load loss tests and logical switching of the MOSFET switch K1, 1 kV switch K2, and 10 kV switch K3 of the integrated wiring module 2; The microprocessor 310 selects the chip with the model STM32F401CCU6. This chip combines a high-speed embedded memory and a wide range of enhanced I / O and peripheral devices, has high performance and high security, and is convenient for the subsequent upgrade and maintenance of the controller 20 and the electrical parameter module 30 (see Figure 1 ).

[0074] The overcurrent threshold database 313 is an access or Mysql or Excel workbook, which is used to compare with the parameters of the transformer 4 input by the three-phase voltage and current sensor 300; the overcurrent threshold database 313 is set with an no-load test current limit value during the no-load test, which can effectively prevent the tested transformer 4 from being burned; during the load test, a load test reference voltage value is set to improve the current boosting efficiency and shorten the test time; the overcurrent threshold database 313 has the following data columns: the first column records the transformer material, the second column records the rated capacity of the transformer, the third column records the rated voltage of the high-voltage side, the fourth column records the rated voltage of the low-voltage side, the fifth column records the connection group label, and the connection group label is the connection method of the high-voltage and low-voltage windings of the transformer 4; the sixth column records the no-load loss, and the no-load loss is the nominal value of the no-load loss of the corresponding type of transformer; the seventh column records the load loss, the eighth column records the short-circuit impedance, the ninth column records the no-load current, the tenth column records the no-load test current limit value, the eleventh column records the load test reference voltage value, and each row of the overcurrent threshold database 313 represents a type of transformer 4; the types of the transformer 4 include:

[0075] 30 kVA oil-immersed three-phase double-winding non-excitation regulating distribution transformer;

[0076] 50 kVA oil-immersed three-phase double-winding non-excitation regulating power transformer;

[0077] 100 kVA oil-immersed three-phase double-winding non-excitation regulating power transformer;

[0078] 160 kVA oil-immersed three-phase double-winding non-excitation regulating power transformer;

[0079] 200 kVA oil-immersed three-phase double-winding non-excitation regulating power transformer;

[0080] 315 kVA oil-immersed three-phase double-winding non-excitation regulating power transformer;

[0081] 400 kVA oil-immersed single-phase double-winding non-excitation regulating power transformer.

[0082] The no-load test current limit value is used to protect the circuit and prevent the tested transformer 4 and the energy efficiency detection device from being burned due to excessive current; the no-load test current limit value is calculated through the parameters of the transformer 4: first, the rated current of the low-voltage side of the transformer is calculated by using the rated voltage data of the low-voltage side of the measured transformer 4, and then the rated no-load current value of the transformer is calculated through the definition of the no-load current percentage (the ratio of the no-load current to the rated current on the low-voltage side when the high-voltage side of the transformer is open and the rated voltage is applied to the low-voltage side). Finally, considering the influence of the current peak and leaving a part of current margin, comprehensively, 1.5 times of the rated no-load current value of the transformer 4 is set as the no-load test current limit value.

[0083] The reference voltage value for the load experiment is used to rapidly increase the current, shorten the test time, and improve the detection efficiency. According to the requirements of the load experiment, the current on the high-voltage side of the transformer 4 should be the rated current. In the traditional boosting process, to ensure that the current on the high-voltage side can reach the rated current, the voltage can only change in small gradients. During the voltage change process, it is necessary to continuously judge the relationship between the real-time current value and the rated current and continuously adjust the voltage, resulting in a large amount of time consumed in the overall boosting process. By setting the reference voltage value for the load experiment, the current on the high-voltage side can quickly reach the rated current, greatly shortening the experiment time. When conducting the load test, the impedance voltage is calculated based on the short-circuit impedance percentage on the nameplate of the transformer 4 and the rated voltage on the high-voltage side. 0.85 times the impedance voltage of the transformer 4 is set as the reference voltage value for the load experiment, so that the voltage on the high-voltage side of the transformer 4 quickly rises to the reference voltage, ensuring that the current flowing through the high-voltage side at this time is close to the rated current. After fine-tuning, the current on the high-voltage side can reach the rated current, greatly reducing the voltage adjustment range and shortening the entire test time.

[0084] The following is the detection parameter table of the overcurrent threshold database 313

[0085]

[0086]

[0087] The relevant data of each type of transformer 4 in the above detection parameter table of the overcurrent threshold database 313 comply with the provisions of GB / T25446—2010 and GB / T6451—2015.

[0088] The three-phase voltage and current sensor 300 and the central processor 31 form an experimental protection module. The experimental protection module compares the obtained information of the transformer 4 with the detection parameters in the overcurrent threshold database 313 from top to bottom. The comparison and judgment process is as follows:

[0089] The first step: Compare the material type of the transformer 4. If the obtained material type is the same as the material type in the current row of the overcurrent threshold database 313, proceed to the next step; otherwise, return to the first step.

[0090] The second step: Compare the rated capacity of the transformer 4. If the obtained rated capacity is equal to the rated capacity in the overcurrent threshold database 313, proceed to the next step; otherwise, return to the first step.

[0091] The third step: Compare the rated voltage on the high-voltage side of the transformer 4. If the obtained rated voltage is equal to the rated voltage in the overcurrent threshold database 313, proceed to the next step; otherwise, return to the first step.

[0092] Step 4: Compare the rated voltage on the low-voltage side of transformer 4. If the obtained rated voltage is equal to the rated voltage in the overcurrent threshold database 313, proceed to the next step; otherwise, return to Step 1.

[0093] Step 5: Compare the connection method of the connection group label of transformer 4. If the obtained connection method of transformer 4 is the same as the connection method in the current row of the overcurrent threshold database 313, proceed to the next step; otherwise, return to Step 1.

[0094] Step 6: Compare the no-load loss of transformer 4: If the obtained no-load loss is less than the no-load loss in the overcurrent threshold database 313, proceed to the next step; otherwise, return to Step 1.

[0095] Step 7: Compare the load loss under the connection method of the connection group label in the overcurrent threshold database 313: If the obtained load loss of transformer 4 under the Dyn11 / Yzn11 connection method is less than the load loss under the Dyn11 / Yzn11 connection method in the current row of the overcurrent threshold database 313, proceed to the next step; otherwise, return to Step 1. If the obtained load loss under the Yyn0 connection method is less than the load loss under the Yyn0 connection method in the current row of the overcurrent threshold database 313, proceed to the next step; otherwise, return to Step 1.

[0096] Step 8: Compare the no-load current: If the obtained no-load current is less than the no-load current in the overcurrent threshold database 313, proceed to the next step; otherwise, return to Step 1.

[0097] Step 9: Compare the short-circuit impedance: If the obtained short-circuit impedance is less than the short-circuit impedance in the overcurrent threshold database 313, proceed to the next step; otherwise, return to Step 1.

[0098] Step 10: Read the data in the last two columns: Take out the no-load test current limit value and the load test reference voltage value in the current row of the overcurrent threshold database 313, and transfer the record in the current row of the overcurrent threshold database 313 to the microprocessor 310.

[0099] Step 11: During the no-load test, the microprocessor 310 sets the no-load test current limit value and monitors the current value of the transformer 4 under test in real time through the three-phase voltage and current sensor 300. Once the current is greater than the no-load test current limit value, the microprocessor 310 cuts off the three-phase fixed-frequency power supply 1 through the power supply voltage control module 32 to protect the transformer 4 under test, the energy efficiency detection device, and the safety of the test personnel. During the load test, the microprocessor 310 sets the load test reference voltage value and monitors the voltage and current values of the transformer 4 under test in real time through the three-phase voltage and current sensor 300, causing the voltage to rise rapidly to the set voltage. After reaching the set voltage, the microprocessor 310 controls the power supply voltage and current control module 32 to change the voltage in small steps until the test current reaches the rated current of the transformer 4, greatly shortening the test time.

[0100] A detection method for a transformer energy efficiency detection device with non-linear zero-crossing optimization, characterized in that: the transformer energy efficiency detection device with non-linear zero-crossing optimization is composed of a three-phase fixed-frequency power supply 1, an integrated wiring module 2, and a detection system module 3. The three-phase fixed-frequency power supply 1 is connected to the transformer 4 through the integrated wiring module 2. The three-phase fixed-frequency power supply 1 and the integrated wiring module 2 are respectively connected to the detection system module 3 to realize the automatic switching of the wiring for the no-load loss test and the load loss test of the transformer 4 and the acquisition of test data. The integrated wiring module 2 includes a controller 20, a metal-oxide semiconductor field effect transistor switch K1, a 1 kV vacuum AC contactor switch K2, a 10 kV vacuum AC contactor switch K3, and a 10 kV high-voltage power supply switch K4. The detection system module 3 is composed of an electrical parameter measurement module 30, a central processor 31, a power supply voltage and current control module 32, and a temperature sensor 33. The electrical parameter measurement module 30 includes a three-phase voltage and current sensor 300, a signal conditioning circuit 301, and an A / D converter 302. The central processor 31 includes a microprocessor 310, an LCD display screen 311, a data optimization module 312, and an overcurrent threshold database 313. The electrical parameter measurement module 30 is connected to the central processor 31 to complete the acquisition, correction, conversion, and transmission of analog electrical signals. The power supply voltage and current control module 32 is connected to the microprocessor 310 to control the output of the three-phase fixed-frequency power supply 1. The temperature sensor 33 is connected to the microprocessor 310 to collect the temperature parameters of the transformer 4. The implementation of its detection method includes the following steps:

[0101] Step 1: When batch-detecting different types of transformers 4, first detect their DC resistance and record the temperature of the current detection environment.

[0102] Step 2: Set the working parameters of the no-load loss test and the load loss test through the setting interface of the detection system module 3, input the corresponding DC resistance value, and adjust the voltage and current output by the three-phase fixed-frequency power supply 1 through the power supply voltage and current control module 32 to meet the no-load and load loss test requirements of the transformer 4. For the no-load test, it is detected at the rated voltage; for the load test, it is detected in the full-current mode. The detection data of the load test in the full-current mode does not need to be converted and can be directly calculated using the energy efficiency detection formula of the transformer 4 to ensure the detection accuracy.

[0103] Step 3: Construct a non-linear zero-crossing optimization model through the microprocessor 310 of the central processor 31, the data optimization module 312, and the over-current threshold database 313 to realize the automatic correction of the detection data of the three-phase voltage and current sensors 300, ensuring good anti-interference performance and high-precision detection effect. The construction method of the non-linear zero-crossing optimization model is as follows:

[0104] 3.1) Obtain the maximum value Umax and the minimum value Umin of the acquired signal, Vpp = Umax - Umin, and calculate Vpp / 2 as the rough estimated value Un of the amplitude.

[0105] 3.2) Use the zero-crossing detection method to determine the phase φ0 and the rough estimated value T0 of the period of the sine wave signal.

[0106] 3.3) Establish an objective function, obtain the correction parameter x, and optimize the measurement data.

[0107] The specific operations are as follows:

[0108] 3.3.1) Establish the objective function

[0109] Ideally, the detected sine waveform satisfies u = U n sin(t / T + φ), and the following objective function is established:

[0110]

[0111]

[0112] where i is the sampling point number, t i and u i are the sampling time and the sampling value respectively; the function g is defined as the sum of the squares of the differences between the actual measured values and the corresponding values calculated according to the set sine function mathematical model. When the function g has the minimum value, the sine function is closest to the ideal value, that is, the test data after non-linear optimization is more accurate.

[0113] 3.3.2) Solve the above objective function using the Newton iteration method;

[0114] Let The linearization equation of f(x) is expressed as:

[0115]

[0116] where x0 is the set initial value;

[0117] When the function reaches an extreme value, that is

[0118]

[0119]

[0120] 3.3.3) Obtain the correction parameter x. At this time, the △x obtained by using formula (5) and the initial value x0 can be used to solve the correction parameter x through the formula x = x0 + △x. Substitute x into the function g to find the value of g(x); use the previously solved x as the initial value and substitute it into formula (5) to solve △x, and repeat the above process until the value of g(x) is greater than the previous x value, then stop the whole process. The previously obtained x value is the data after non-linear zero-crossing optimization. At this time, the objective function is closest to the ideal value, that is, the most accurate;

[0121] Step Four: Start the detection with one key. The central processing unit 31 automatically and remotely controls the logical switching of the metal-oxide semiconductor field effect transistor switch K1, 1 kV vacuum AC contactor switch K2, and 10 kV vacuum AC contactor switch K3 of the three-phase fixed-frequency power supply 1 and the integrated wiring module 2 to achieve the automatic detection of the no-load of the transformer 4; the central processing unit 31 controls the integrated wiring module 2 to automatically complete the no-load loss test wiring of the transformer 4, obtains the voltage and current test data through the three-phase voltage and current sensor 300, and automatically corrects the test data through the signal conditioning unit 301 in combination with the non-linear zero-crossing optimization method to ensure the accuracy of the detection data; the corrected test data is signal-converted through the A / D converter 302 and transmitted to the central processing unit 31, and the rated no-load loss is directly calculated by the central processing unit 31; during the load test of the transformer 4, the controller 20 controls the integrated wiring module 2 to automatically complete the switching of the load loss test wiring of the transformer 4, obtains and corrects the voltage and current data and temperature parameters through the electrical parameter measurement module 30, and then transmits them to the central processing unit 31, and calculates the rated load loss and short-circuit impedance by using the energy efficiency data calculation formula;

[0122] Step Five: The central processing unit 31 is used to summarize, display, and generate a detection data report for the detection data.

[0123] When calculating the energy efficiency of the transformer 4, it is necessary to measure the voltage, current and their phase difference during the no-load and load tests in real time. The voltage and current signals are converted into voltage signals for measurement through voltage transformers and current transformers. During the measurement process, due to reasons such as voltage and current waveform distortion and A / D quantization error, there will inevitably be certain errors in the sampled data. The real-time voltage amplitude and period obtained by the traditional zero-crossing detection method will have large deviations. The non-linear zero-crossing data optimization method improves the traditional zero-crossing method, without the need to pre-design a zero-crossing detection circuit, effectively saving hardware costs. Through this method, the detection data of the three-phase voltage and current sensor 300 is optimized, successfully avoiding interference and improving the detection accuracy.

[0124] The non-linear zero-crossing data optimization method constructs a non-linear zero-crossing optimization model through the microprocessor 310 of the central processor 31, the data optimization module 312 and the over-current threshold database 313 to realize the automatic correction of the detection data of the three-phase voltage and current sensor 300, ensuring good anti-interference performance and high-precision detection effect. The following is the construction method of the non-linear zero-crossing optimization model:

[0125] 3.1) Obtain the maximum value Umax and the minimum value Umin of the collected signal, Vpp = Umax - Umin, and calculate Vpp / 2 as the rough estimate value Un of the amplitude.

[0126] 3.2) Use the zero-crossing detection method to determine the phase φ0 and the rough estimate value T0 of the period of the sine wave signal.

[0127] 3.3) Establish an objective function, obtain the correction parameter x, and optimize the measurement data.

[0128] The specific operation is as follows:

[0129] 3.3.1) Establish an objective function

[0130] Ideally, the detected sine wave form satisfies u = U n sin(t / T + φ), and the following objective function is established:

[0131]

[0132]

[0133] where i is the sampling point number, t i and u i are the sampling time and the sampling value respectively; the function g is defined as the sum of the squares of the differences between the actual measured values and the corresponding values calculated according to the set sine function mathematical model. When the function g has a minimum value, the sine function is closest to the ideal value, that is, the test data after non-linear optimization is more accurate.

[0134] 3.3.2) Solve the above objective function by using the Newton iteration method;

[0135] Let The linearized equation of f(x) is expressed as:

[0136]

[0137] where x0 is the set initial value;

[0138] When the function reaches an extreme value, that is

[0139]

[0140]

[0141] 3.3.3) Obtain the correction parameter x; at this time, the △x obtained by using formula (5) and the initial value x0 can be used to solve the correction parameter x through the formula x = x0 + △x, substitute x into the function g to find the value of g(x); substitute the previously solved x as the initial value into formula (5) to solve △x, and repeat the above process until the value of g(x) is greater than the previous x value, then stop the whole process. The previously obtained x value is the optimized data of the non-linear zero-crossing point, and at this time the objective function is closest to the ideal value, that is, the most accurate.

[0142] The non-linear zero-crossing data optimization method has good anti-interference performance. For example: when the sampling frequency is 20 kHz, a random error of -0.5 to 0.5 V is applied to the sine signal 5sin(314.15926t + 0.3), which is equivalent to introducing random interference. Use the traditional zero-crossing detection method to measure this signal, (see Figure 5 ). Figure 5 is the comparison result graph of the sampling signals detected by the non-linear zero-crossing optimization algorithm of the present invention and the zero-crossing method; Figure 5 The black solid line in is the ideal waveform V1 of the sine signal. Since a random error of ±0.5 V is introduced to the sine signal, the voltage waveform becomes an irregular sine wave signal, and this irregular sine wave signal fluctuates around the ideal waveform of the sine signal. The gray dotted line is the signal waveform V2 measured by the traditional zero-crossing algorithm. Initially, the signal waveform hardly fluctuates. As time goes on, the signal waveform V2 measured by the traditional zero-crossing algorithm gradually advances ahead of the ideal value, and the error gradually increases, indicating weak anti-interference ability; Figure 5 The black dotted line in is the signal waveform V3 measured by the non-linear zero-crossing optimization algorithm. When the introduced random error continuously increases, its measured value always fluctuates slightly around the ideal waveform V1 of the sine signal, approaching the ideal value, indicating that the non-linear zero-crossing optimization algorithm has high measurement accuracy and strong anti-interference ability.

[0143] (See Figure 6 ), Figure 6 is a comparison result graph of the non - linear zero - crossing optimization algorithm and the zero - crossing method for detecting the voltage amplitude; the voltage amplitude error range of the traditional zero - crossing protection method is +0.05 to +0.48 V; the voltage amplitude error range of the non - linear zero - crossing optimization method is -0.02 to +0.01 V; Figure 6 The black solid line in

[0144] (See Figure 7 ) Figure 7 is a comparison result graph of the non - linear zero - crossing optimization algorithm and the zero - crossing method for detecting the voltage frequency; the voltage frequency error range of the traditional zero - crossing protection method is -0.1 to +0.1 Hz; the voltage frequency error range of the non - linear zero - crossing optimization method is -0.03 to +0.01 Hz, and the frequency error is reduced by 10 times compared with the traditional zero - crossing protection method; Figure 7 The black solid line in Figure 7 is the ideal value f1 of the signal frequency, with a value of 50 Hz. Figure 7 The gray dashed line in

[0145] is the measured value f3 of the signal frequency by the traditional zero - crossing detection method. As the injected random error increases continuously, the fluctuation amplitude of the measured value f3 of the signal frequency by the traditional zero - crossing detection method near the ideal value f1 of the voltage signal frequency gradually increases, indicating its low measurement accuracy and weak anti - interference ability; Figure 6 and Figure 7 The black dashed line in

[0146] Through the above comparison results of the non - linear zero - crossing optimization algorithm and the traditional zero - crossing detection method for signal voltage / frequency Figure 6 and Figure 7 it is clearly known that: the non - linear zero - crossing optimization algorithm has a more prominent optimization effect on the detected data, enhances the overall anti - interference ability of the device system, greatly reduces errors, and effectively improves the accuracy of the detected data.

[0146] The transformer energy efficiency detection device and detection method using the nonlinear zero-crossing optimization of the present invention have the following advantages over the prior art: the overcurrent protection device of the present invention effectively prevents overcurrent from occurring during the test by monitoring the voltage and current values of the transformer 4 under test in real time and comparing them with the overcurrent threshold database 313, thereby providing safety protection for the transformer 4 under test, the energy efficiency detection device and the tester; a nonlinear zero-crossing optimization method is proposed by improving the zero-crossing data processing method, which has stronger anti-interference ability and reduces the error of the detection data by nearly 20 times compared with the zero-crossing method, making the optimized detection data closer to the ideal true value. The device of the present invention has automatic voltage step-up and voltage step-down, temperature detection and other functions. The device has the functions of measuring and detecting the no-load power of transformer, and the test results are centralized, which fully meets the technical requirements of energy efficiency grade detection; the nonlinear zero-crossing optimized transformer energy efficiency detection device and detection method are used to realize batch detection of energy efficiency grade detection test items of various types of transformers 4, and the no-load test wiring switching is realized through the integrated wiring module 2, which replaces the traditional manual wiring, simplifies the experimental operation, avoids manual wiring errors, improves the system safety and test data accuracy, greatly shortens the detection time, and improves the detection efficiency through the automated test process; it is simple and convenient to operate, has strong safety, and high detection accuracy, which fully meets the needs of power transformer 4 energy efficiency grade detection, and has now become a powerful assistant for power workers.

Claims

1. A transformer energy efficiency detection device with optimized non-linear zero-crossing points, characterized in that: The transformer energy efficiency detection device with optimized non-linear zero-crossing consists of a three-phase fixed-frequency power supply (1), an integrated wiring module (2), and a detection system module (3). The three-phase fixed-frequency power supply (1) is connected to the transformer (4) through the integrated wiring module (2). The three-phase fixed-frequency power supply (1) and the integrated wiring module (2) are respectively connected to the detection system module (3) to achieve automatic switching of the wiring for no-load loss test and load loss test of the transformer (4) and acquisition of test data. The integrated wiring module (2) includes a controller (20), a metal-oxide semiconductor field effect transistor switch (K1), a 1kV vacuum AC contactor switch (K2), a 10kV vacuum AC contactor switch (K3), and a 10kV high-voltage power supply switch (K4). The detection system module (3) consists of an electrical parameter measurement module (30), a central processing unit (31), a power supply voltage and current control module (32), and a temperature sensor (33). The electrical parameter measurement module (30) includes three-phase voltage and current sensors (300), a signal conditioning circuit (301), and an A / D converter (302). The central processing unit (31) includes a microprocessor (310), an LCD display screen (311), a data optimization module (312), and an over-current threshold database (313). The electrical parameter measurement module (30) is connected to the central processing unit (31) to complete the acquisition, correction, conversion, and transmission of analog electrical signals. The power supply voltage and current control module (32) is connected to the microprocessor (310) to control the output of the three-phase fixed-frequency power supply (1). The temperature sensor (33) is connected to the microprocessor (310) to collect the transformer temperature parameters. The controller (20) of the integrated wiring module (2) outputs three signals to respectively control the on and off of the metal-oxide semiconductor field effect transistor switch (K1), the 1kV vacuum AC contactor switch (K2), and the 10kV vacuum AC contactor switch (K3), meeting the wiring requirements for no-load loss test and load loss test, and eliminating the need to manually remove and connect the lines during no-load loss test and load loss test. The data optimization module (312) realizes non-linear zero-crossing optimization of the measurement values of the three-phase voltage and current sensors (300) through the microprocessor (310) in combination with the over-current threshold database (313), automatically corrects the test data, reduces the measured voltage amplitude error by 48 times, and reduces the frequency error by 10 times. The over-current threshold database (313) is set with a no-load test current limit value and a load test reference voltage value.

2. The transformer energy efficiency detection device with optimized non-linear zero-crossing point according to claim 1, characterized in that: The three-phase voltage and current sensors (300) of the electrical parameter measurement module (30) collect the electrical parameters during no-load loss test and load loss test. The voltage and current measurement accuracy levels are 0.1 level, meeting the requirements of national and industry standards. The signal conditioning circuit (301) combines the measurement values of the three-phase voltage and current sensors (300) with the non-linear zero-crossing optimization algorithm to automatically correct the test data.

3. The transformer energy efficiency detection device with optimized non-linear zero-crossing point according to claim 1, characterized in that: The described three-phase voltage and current sensor (300) and the central processing unit (31) constitute an experimental overcurrent protection module. The magnitude of the current detected by the three-phase voltage and current sensor (300) is transmitted to the central processing unit (31), and it is judged whether the current signal exceeds the limit value by comparing with the overcurrent threshold database (313) of the central processing unit (31). If it exceeds the limit value, the central processing unit (31) controls to stop the experiment; otherwise, the experiment continues.

4. The transformer energy efficiency detection device with optimized non-linear zero-crossing point according to claim 1, characterized in that: The described power supply voltage and current control module (32) receives the control signal of the central processing unit (31) and completes the automatic adjustment of the output voltage and current of the three-phase fixed-frequency power supply (1).

5. A transformer energy efficiency detection device with optimized non-linear zero-crossing points according to claim 1, characterized in that: A plurality of the described temperature sensors (33) are installed to achieve distributed real-time temperature detection, and the average temperature is selected as the temperature for the DC resistance detection and load loss test of the transformer (4).

6. The transformer energy efficiency detection device with optimized non-linear zero-crossing point according to claim 1, characterized in that: The described controller (20) is respectively connected to the metal-oxide semiconductor field effect transistor switch (K1), the 1 kV vacuum AC contactor switch (K2), and the 10 kV vacuum AC contactor switch (K3) to control the on-off states of the three switches; the upper end of the metal-oxide semiconductor field effect transistor switch (K1) is connected to the first group of the low-voltage side of the transformer (4) through a bushing (5), and the lower end is connected to the three-phase fixed-frequency power supply (1) through an electrical cubicle (8). When the metal-oxide semiconductor field effect transistor switch (K1) is closed, the first group of the low-voltage side of the transformer (4) is powered by the three-phase fixed-frequency power supply (1); the upper end of the 1 kV vacuum AC contactor switch (K2) is connected to the second group of the low-voltage side of the transformer (4) through a bushing (6), and the lower end is short-circuited through a copper bar inside the electrical cubicle (8). When the 1 kV vacuum AC contactor switch (K2) is closed, the low-voltage side of the transformer (4) is short-circuited; the upper end of the 10 kV vacuum AC contactor switch (K3) is connected to the third group of the high-voltage side of the transformer (4) through a bushing (7), and the lower end is connected to the three-phase fixed-frequency power supply (1) through an electrical cubicle (8). When the 10 kV vacuum AC contactor switch (K3) is closed, the high-voltage end of the transformer (4) is powered by the three-phase fixed-frequency power supply (1); when the 10 kV high-voltage power supply switch (K4) is closed, the three-phase fixed-frequency power supply (1) power supply circuit of the 10 kV vacuum AC contactor switch (K3) is connected.

7. A detection method for a transformer energy efficiency detection device with optimized non - linear zero - crossing points, characterized in that: The described transformer energy efficiency detection device with optimized non-linear zero-crossing consists of a three-phase fixed-frequency power supply (1), an integrated wiring module (2), and a detection system module (3). The three-phase fixed-frequency power supply (1) is connected to the transformer (4) through the integrated wiring module (2). The three-phase fixed-frequency power supply (1) and the integrated wiring module (2) are respectively connected to the detection system module (3) to achieve automatic switching of the wiring for no-load loss test and load loss test of the transformer and acquisition of test data. The integrated wiring module (2) includes a controller (20), a metal-oxide semiconductor field-effect transistor switch (K1), a 1 kV vacuum AC contactor switch (K2), a 10 kV vacuum AC contactor switch (K3), and a 10 kV high-voltage power supply switch (K4). The detection system module (3) consists of an electrical parameter measurement module (30), a central processing unit (31), a power supply voltage and current control module (32), and a temperature sensor (33). The electrical parameter measurement module (30) includes three-phase voltage and current sensors (300), a signal conditioning circuit (301), and an A / D converter (302). The central processing unit (31) includes a microprocessor (310), an LCD display screen (311), a data optimization module (312), and an overcurrent threshold database (313). The electrical parameter measurement module (30) is connected to the central processing unit (31) to complete the acquisition, correction, conversion, and transmission of analog electrical signals. The power supply voltage and current control module (32) is connected to the microprocessor (310) to control the output of the three-phase fixed-frequency power supply (1). The temperature sensor (33) is connected to the microprocessor (310) to acquire the temperature parameters of the transformer (4). Its detection method is realized through the following steps: Step 1. When batch-detecting different types of transformers (4), first detect the DC resistance and record the temperature of the current detection environment. Step 2. Set the working parameters of the no-load loss test and the load loss test through the setting interface of the detection system module (3), input the corresponding DC resistance value, and adjust the voltage and current output by the three-phase fixed-frequency power supply (1) through the power supply voltage and current control module (32) to meet the requirements of the no-load and load loss tests of the transformer (4). For the no-load test, detect with the rated voltage. For the load test, detect in the full-current mode. The detection data in the full-current mode load test does not need to be converted and is directly calculated using the transformer (4) energy efficiency detection formula to ensure the detection accuracy. Step 3. Through the microprocessor (310), data optimization module (312), and overcurrent threshold database (313) of the central processing unit (31), construct a non-linear zero-crossing optimization model to achieve automatic correction of the detection data of the three-phase voltage and current sensors (300) and ensure good anti-interference performance and high-precision detection effect. The construction method of the non-linear zero-crossing optimization model is as follows: 3.1) Obtain the maximum value Umax and the minimum value Umin of the acquired signal, Vpp = Umax - Umin, and calculate Vpp / 2 as the rough estimated value Un of the amplitude. 3.2) Determine the phase φ0 of the sine wave signal and the rough estimated value T0 of the period using the zero-crossing detection method; 3.3) Establish an objective function, obtain the correction parameter x, and optimize the measurement data; The specific operations are as follows: 3.3.1) Establish the objective function The sine wave detected ideally satisfies \(u = U\sin(\frac{t}{T}+\varphi)\), and the following objective function is established: n \(\sin(\frac{t}{T}+\varphi)\), an objective function is established as follows: Among them, i is the number of sampling points, t i and u i are the sampling time and the sampling value respectively; the function g is defined as the sum of squares of the differences between the actual measured values and the corresponding values calculated according to the set sine function mathematical model. When the function g has a minimum value, the sine function is closest to the ideal value, that is, the test data is more accurate after non-linear optimization; 3.3.2) Solve the above objective function using the Newton iteration method; Let The linearized equation of f(x) is expressed as: where x0 is the set initial value; When the function reaches an extreme value, that is 3.3.3) Obtain the correction parameter x. At this time, the △x obtained by using formula (5) and the initial value x0 can be used to solve the correction parameter x through the formula x = x0 + △x, and substitute x into the function g to find the value of g(x); take the x obtained in the previous solution as the initial value and substitute it into formula (5) to solve △x, and repeat the above process until the value of g(x) is greater than the previous x value to stop the whole process. Then the x value obtained in the previous time is the data optimized by the non-linear zero-crossing, and at this time the objective function is closest to the ideal value, that is, the most accurate; Step Four: One-key start the detection. Automatically and remotely control the logical switching of the metal-oxide semiconductor field effect transistor switch (K1), 1kV vacuum AC contactor switch (K2), and 10kV vacuum AC contactor switch (K3) of the power supply and the integrated wiring module (2) through the central processing unit (31) to achieve the automatic detection of the no-load and load of the transformer (4); the central processing unit (31) controls the integrated wiring module (2) to automatically complete the wiring for the no-load loss test of the transformer (4), obtain the voltage and current test data through the three-phase voltage and current sensor (300), and automatically correct the test data through the signal conditioning circuit (301) in combination with the non-linear zero-crossing optimization method to ensure the accuracy of the detection data; convert the corrected test data into a signal through the A / D converter (302) and transmit it to the central processing unit (31), and directly calculate the rated no-load loss through the central processing unit (31); during the load test of the transformer (4), control the integrated wiring module (2) to automatically complete the switching of the wiring for the load loss test of the transformer (4) through the controller (20), obtain and correct the voltage and current data and temperature parameters through the electrical parameter measurement module (30), and then transmit them to the central processing unit (31), and calculate the rated load loss and short-circuit impedance using the energy efficiency data calculation formula; Step Five: Through the central processing unit (31), achieve the summary, display, and generation of the detection data report.

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