Hand-held mutual inductor intelligent test system

Abstract

The invention provides a handheld intelligent testing system for a mutual inductor. The system comprises a power signal generation module, a signal conditioning and collecting module, a data processing and calculating module, a communication data management module and a user interaction module. The power supply signal generation module is used for providing a power supply required by the system for testing the mutual inductor and generating a high-precision and low-noise test signal; the signal conditioning acquisition module is used for acquiring a test signal output by the mutual inductor and conditioning the test signal to a standard input range of the system analog-to-digital converter; the data processing calculation module is used for calculating and analyzing the collected test signals to obtain error parameters of the mutual inductor; the communication data management module is used for completing data transmission and data management between the edge end and the management end; the user interaction module is used for displaying system data for testers through a touch display interface of the system; according to the invention, miniaturization, high precision and intellectualization of mutual inductor testing are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of power testing systems, and in particular to a handheld intelligent testing system for transformers. Background Art

[0002] Instrument transformers (ITs), as crucial measurement and protection components in power systems, have a performance directly impacting the operational safety and stability of the power grid. To ensure their measurement accuracy and operational reliability, regular characteristic testing and calibration are essential. Currently, most IT testing methods rely on volt-ampere characteristic testing under power-frequency high-voltage excitation or on ratio and angular error calibration by splicing standard TIs. These traditional testing methods typically require large, bulky, and heavy high-voltage power supply equipment, resulting in complex operation, low test efficiency, poor field adaptability, and high voltage hazards.

[0003] In addition, existing portable test devices are mainly based on single-point data measurement, lacking comprehensive extraction and high-precision digital processing of the overall characteristic parameters of the transformer, and cannot effectively adapt to the new smart grid's demand for improved online rapid detection, miniaturization, portability and intelligent evaluation capabilities of transformers. Therefore, how to achieve miniaturization, intelligence and efficiency of transformer testing equipment while ensuring measurement accuracy and safety has become a technical problem that urgently needs to be solved in this field.

[0004] After consulting the relevant disclosed technical solutions, the technology with publication number CN205643677U proposes a handheld current transformer volt-ampere characteristic tester, including a 12V lithium battery pack B1, a DC air switch K1, an inverter module M1, an auto-voltage regulating transformer T1, an AC voltmeter V1, an AC ammeter A1 and an AC air switch K2; it also includes a compensation circuit, an overcurrent alarm circuit and an oscillation circuit, the compensation circuit includes a compensation capacitor C1, the compensation circuit is connected in parallel in the output circuit of the auto-voltage regulator T1; the overcurrent alarm circuit includes a sampling current limiting resistor R1, The rectifier diode D1, buzzer H1 and filter capacitor C3, the overcurrent alarm circuit is connected in series in the output circuit of the auto-voltage regulating transformer T1; the oscillation circuit includes a current-limiting resistor R2 and a protection capacitor C2, and the oscillation circuit is connected in parallel with the secondary winding of the current transformer under test; this solution does not require a test power supply, and the level of the current transformer secondary winding can be quickly determined from the current and voltmeter readings. It is simple to operate and highly efficient; however, this solution only judges the transformer volt-ampere characteristics based on traditional electrical quantity readings. The test accuracy is greatly affected by equipment fluctuations, making it difficult to meet high-precision testing requirements. Summary of the Invention

[0005] The purpose of the present invention is to address the current deficiencies and propose a handheld intelligent testing system for transformers.

[0006] The present invention adopts the following technical solutions:

[0007] A handheld intelligent transformer testing system includes a power signal generation module, a signal conditioning and acquisition module, a data processing and calculation module, a communication data management module, and a user interaction module; the power signal generation module is used to provide the power required by the system for testing the transformer, and to generate a high-precision, low-noise test signal; the signal conditioning and acquisition module is used to collect the test signal output by the transformer, and condition the test signal to within the standard input range of the system analog-to-digital converter; the data processing and calculation module is used to calculate and analyze the collected test signal to obtain the error parameters of the transformer; the communication data management module is used to complete data transmission and data management between the edge end and the management end; and the user interaction module is used to display system data to testers through the system's touch display interface.

[0008] The power signal generation module includes a DC power supply unit, a variable frequency AC signal unit, a signal control unit and a protection isolation unit; the DC power supply unit is used to provide a stable DC power supply for each functional module of the system; the variable frequency AC signal unit is used to output an adjustable AC test signal; the signal control unit is used to control the output mode of the AC test signal according to the test requirements; the protection isolation unit is used to realize power isolation protection between the AC test signal and the test object.

[0009] Furthermore, the signal conditioning and acquisition module includes a signal amplification unit, a signal filtering unit, a synchronous sampling unit and an input protection unit; the signal amplification unit is used to adjust the amplitude of the test signal output by the transformer so that the amplitude of the test signal adapts to the standard input range of the system analog-to-digital converter; the signal filtering unit is used to filter the test signal output by the transformer; the synchronous sampling unit is used to realize multi-channel synchronous acquisition of the test signal output by the transformer; the input protection unit is used to prevent external abnormal signals from damaging the analog-to-digital converter.

[0010] Furthermore, the data processing and calculation module performs data analysis and processing based on the nonlinear equivalent circuit model of the transformer to derive and calculate the error parameters of the transformer; the data processing and calculation module includes an error calculation unit, an excitation parameter extraction unit, a turns ratio analysis unit and a characteristic curve generation unit; the error calculation unit is used to calculate the error parameters of the transformer based on the nonlinear equivalent circuit model; the excitation parameter extraction unit is used to extract the standard excitation admittance parameters; the turns ratio analysis unit is used to obtain the actual turns ratio of the transformer; the characteristic curve generation unit is used to generate a VA characteristic curve and an error characteristic curve.

[0011] Furthermore, the error calculation unit obtains the error parameter of the mutual inductor by the following formula:

[0012]

[0013] Where ε is the complex error of the transformer, that is, the error parameter, which is used to characterize the amplitude error and phase error of the transformer under specific load conditions; R CT is the secondary winding resistance of the transformer, which is obtained by applying a DC current and measuring the voltage drop according to Ohm's law; j is an imaginary unit used to represent the phase characteristics of the AC signal in the complex domain; L s is the leakage inductance of the secondary winding of the transformer, reflecting the inductive reactance component caused by the leakage magnetic flux in the secondary winding; Z b is the secondary load impedance of the transformer, which is a known measurable parameter; is the power factor angle of the secondary load, which indicates the phase difference between the secondary voltage and the secondary current. It is obtained by synchronously sampling the secondary voltage and current signals and calculating the phase difference. Y is the standard excitation admittance parameter, which indicates the composite admittance of the transformer core under rated working conditions. SR is the rated current ratio of the transformer, which is a known parameter. N is the actual turns ratio of the transformer.

[0014] Furthermore, the excitation parameter extraction unit obtains the standard excitation admittance parameter of the transformer in the following manner:

[0015] S11: Applying an AC voltage signal with controllable amplitude and gradually decreasing frequency to the secondary side of the transformer through the signal control unit. The starting frequency is set to the standard power frequency, and the frequency is gradually reduced with a preset step length until the minimum test frequency is reached.

[0016] S12: At each test frequency point, the voltage signal and excitation current signal applied on the secondary side of the transformer are collected in real time;

[0017] S13: For each set of collected voltage signals and excitation current signals, process them according to the frequency conversion formula to convert the excitation voltage under the test conditions into the equivalent excitation voltage under the standard power frequency. The conversion formula is:

[0018]

[0019] Among them, U is the equivalent excitation voltage at standard power frequency, U x Indicates that in the variable frequency test, the secondary side of the transformer is at the test frequency f x The voltage signal applied under the test frequency is x; the index number of the test frequency point is f b is the frequency value corresponding to the standard power frequency;

[0020] S14: based on the converted equivalent excitation voltage and the corresponding excitation current, draw the VA characteristic curve of the transformer;

[0021] S15: Derive the excitation admittance Y of the transformer under standard power frequency conditions based on the VA characteristic curve data.

[0022] Furthermore, the turns ratio analysis unit obtains the actual turns ratio of the transformer in the following manner:

[0023] S21: Applying an adjustable power frequency AC current to the transformer through-core voltage winding via the power signal generation module, so that the transformer core generates a stable AC magnetic flux;

[0024] S22: When the core flux is stable, measure the induced voltage across the transformer secondary winding and the auxiliary measurement winding simultaneously. Since both the secondary winding and the auxiliary winding are in an open circuit state and share the same core flux, the induced voltage between them is proportional to the number of winding turns.

[0025] S23: According to the principle that the induced electromotive force is proportional to the number of turns, the turns ratio of the transformer secondary winding to the auxiliary winding is taken as the actual turns ratio of the transformer.

[0026] The beneficial effects achieved by the present invention are:

[0027] The present invention uses a transformer testing method based on a nonlinear equivalent circuit model, combined with variable frequency excitation, frequency conversion, and standard parameter extraction technology, to achieve high-precision measurement and intelligent trend analysis of transformer error parameters, significantly improving the miniaturization, portability, and test safety of the test system. This solution can also autonomously identify the performance change trend of the transformer and provide early warning of potential degradation problems, comprehensively improving the accuracy, real-time performance, and intelligent operation and maintenance level of the transformer detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention can be further understood from the following description in conjunction with the accompanying drawings. The components in the figures are not necessarily drawn to scale, but rather the emphasis is placed on illustrating the principles of the embodiments. In different views, the same reference numerals designate corresponding parts.

[0029] Figure 1 It is a schematic diagram of the overall module of the present invention.

[0030] Figure 2 Schematic diagram of the nonlinear equivalent circuit model of the present invention.

[0031] Figure 3 This is a schematic diagram of the working process of the excitation parameter extraction unit of the present invention.

[0032] Figure 4 Schematic diagram of the working process of the turns ratio analysis unit of the present invention.

[0033] Figure 5 This is a schematic diagram of the circuit wiring structure of the turns ratio analysis unit of the present invention.

[0034] Figure 6 Schematic diagram of the workflow of the trend analysis unit of the present invention.

[0035] Figure 7 is the ω under different λ values of the present invention i With Δt i Schematic diagram of the function changes.

[0036] Meaning of the letters in the picture: R P is the primary winding resistance, L P is the leakage inductance of the primary winding, I P is the primary side current, N P , N S is an ideal transformer winding, I ST is the excitation branch input current, I CT is the secondary side current, L S is the secondary winding side leakage inductance, R CT is the secondary winding resistance, L main is the inductance of the excitation circuit, R eddy is the eddy current resistance, R H is the hysteresis resistance, U C (V C ) is the voltage across the excitation inductor, U CT (V B ) is the voltage across the load, Z b is the secondary load impedance, I E is the eddy current component, I L is the eddy current component, I ex is the excitation current component, P1, P2, S1, and S2 are the connection terminals; AS is the current source in the power signal generation module, W1 is the CT through-core voltage winding, W2 is the CT secondary winding, W3 is the CT through-core auxiliary measurement winding, V is the voltage measurement unit for measuring the secondary winding, and mV is the voltage measurement unit for measuring the auxiliary through-core winding. DETAILED DESCRIPTION

[0037] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with its embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention; for those skilled in the art, after reviewing the following detailed description, other systems, methods and / or features of the present embodiment will become apparent; it is intended that all such additional systems, methods, features and advantages are included in this specification; included within the scope of the present invention and protected by the appended claims; additional features of the disclosed embodiments are described in the following detailed description, and these features will be apparent from the following detailed description.

[0038] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. This is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or component referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0039] Example 1:

[0040] like Figure 1 As shown, this embodiment provides a handheld transformer intelligent testing system, which includes a power signal generation module, a signal conditioning and acquisition module, a data processing and calculation module, a communication data management module and a user interaction module; the power signal generation module is used to provide the power required by the system to test the transformer, and generate a high-precision and low-noise test signal; the signal conditioning and acquisition module is used to collect the test signal output by the transformer and condition the test signal to the standard input range of the system analog-to-digital converter; the data processing and calculation module is used to calculate and analyze the collected test signal to obtain the error parameter of the transformer; the communication data management module is used to complete data transmission and data management between the edge end and the management end; the user interaction module is used to display system data to the tester through the system's touch display interface;

[0041] Specifically, the test signal output by the transformer includes a voltage signal and a current signal induced by the secondary winding under a magnetic flux state established in the iron core after an excitation current is applied to the primary side of the transformer;

[0042] The power signal generation module includes a DC power supply unit, a variable frequency AC signal unit, a signal control unit and a protection isolation unit; the DC power supply unit is used to provide a stable DC power supply for each functional module of the system; the variable frequency AC signal unit is used to output an adjustable AC test signal; the signal control unit is used to control the output mode of the AC test signal according to the test requirements; the protection isolation unit is used to achieve power isolation protection between the AC test signal and the test object;

[0043] The signal conditioning and acquisition module includes a signal amplification unit, a signal filtering unit, a synchronous sampling unit, and an input protection unit; the signal amplification unit is used to adjust the amplitude of the test signal output by the mutual inductor so that the test signal amplitude adapts to the standard input range of the system analog-to-digital converter; the signal filtering unit is used to filter the test signal output by the mutual inductor; the synchronous sampling unit is used to realize multi-channel synchronous acquisition of the test signal output by the mutual inductor; the input protection unit is used to prevent external abnormal signals from damaging the analog-to-digital converter;

[0044] Further, such as Figure 2 As shown, the data processing and calculation module performs data analysis and processing based on the nonlinear equivalent circuit model of the transformer to derive and calculate the error parameters of the transformer; the data processing and calculation module includes an error calculation unit, an excitation parameter extraction unit, a turns ratio analysis unit and a characteristic curve generation unit; the error calculation unit is used to calculate the error parameters of the transformer based on the nonlinear equivalent circuit model; the excitation parameter extraction unit is used to extract the standard excitation admittance parameters; the turns ratio analysis unit is used to obtain the actual turns ratio of the transformer; the characteristic curve generation unit is used to generate a VA characteristic curve and an error characteristic curve;

[0045] Furthermore, the error calculation unit obtains the error parameter of the mutual inductor by the following formula:

[0046]

[0047] Where ε is the complex error of the transformer, that is, the error parameter, which is used to characterize the amplitude error and phase error of the transformer under specific load conditions; R CT is the secondary winding resistance of the transformer, which is obtained by applying a DC current and measuring the voltage drop according to Ohm's law; j is an imaginary unit used to represent the phase characteristics of the AC signal in the complex domain; L s is the leakage inductance of the secondary winding of the transformer, which reflects the inductive reactance caused by the leakage flux in the secondary winding and can be ignored in general; Z b is the secondary load impedance of the transformer, which is a known measurable parameter; is the power factor angle of the secondary load, which represents the phase difference between the secondary voltage and the secondary current. It is obtained by synchronously sampling the secondary voltage and current signals and calculating the phase difference. Y is the standard excitation admittance parameter, which represents the composite admittance of the transformer core under rated working conditions. SR is the rated current ratio of the transformer, which is a known parameter. N is the actual turns ratio of the transformer.

[0048] Further, such as Figure 3 As shown, the excitation parameter extraction unit obtains the standard excitation admittance parameter of the transformer in the following manner:

[0049] S11: Apply an AC voltage signal with controllable amplitude and gradually decreasing frequency to the secondary side of the transformer through the signal control unit. The starting frequency is set to the standard power frequency, such as 50 Hz, and the frequency is gradually reduced in a preset step size until the minimum test frequency is reached.

[0050] S12: At each test frequency point, the voltage signal and excitation current signal applied on the secondary side of the transformer are collected in real time;

[0051] S13: For each set of collected voltage signals and excitation current signals, process them according to the frequency conversion formula to convert the excitation voltage under the test conditions into the equivalent excitation voltage under the standard power frequency. The conversion formula is:

[0052]

[0053] Among them, U is the equivalent excitation voltage at standard power frequency, U x Indicates that in the variable frequency test, the secondary side of the transformer is at the test frequency f x The voltage signal applied under the test frequency is x; the index number of the test frequency point is f. b is the frequency value corresponding to the standard power frequency;

[0054] S14: based on the converted equivalent excitation voltage and the corresponding excitation current, draw the VA characteristic curve of the transformer;

[0055] S15: Derived from the VA characteristic curve data, the excitation admittance Y of the transformer under standard power frequency conditions is expressed as:

[0056] Y = G - jB;

[0057] Among them, G is the real part of the excitation admittance, which represents the equivalent resistive loss of the transformer core; B is the imaginary part of the excitation admittance, which represents the equivalent inductive reactance characteristic of the transformer core;

[0058] Because the magnetic flux density of the transformer core is proportional to the applied voltage and inversely proportional to the frequency, the traditional method requires applying a very high voltage to make the core reach the rated excitation state under standard power frequency, which has problems such as large equipment and dangerous high voltage. By gradually reducing the frequency, the same magnetic flux state as that under power frequency high voltage can be achieved at a very low voltage. This solution obtains the excitation characteristic data of the transformer by applying an AC signal with controllable amplitude and gradually decreasing frequency on the secondary side, and uniformly converts the excitation voltage of each test point to the standard power frequency conditions through the frequency conversion formula to derive the standard excitation admittance parameters of the transformer. Compared with the traditional power frequency high-voltage test method, this method achieves the same magnetic flux state through variable frequency low-voltage excitation, effectively avoiding the danger of high voltage, significantly reducing the voltage level and volume and weight of the test equipment, realizing the miniaturization and portability of the test system, and at the same time improving the test safety and automation level.

[0059] Further, such as Figure 4 、 Figure 5 As shown, the turns ratio analysis unit obtains the actual turns ratio of the transformer in the following manner:

[0060] S21: Applying an adjustable power frequency AC current to the transformer through-core voltage winding via the power signal generation module, so that the transformer core generates a stable AC magnetic flux;

[0061] S22: When the core flux is stable, measure the induced voltage across the transformer secondary winding and the auxiliary measurement winding simultaneously. Since both the secondary winding and the auxiliary winding are in an open circuit state and share the same core flux, the induced voltage between them is proportional to the number of winding turns.

[0062] S23: According to the principle that the induced electromotive force is proportional to the number of turns, the turns ratio of the transformer secondary winding to the auxiliary winding is taken as the actual turns ratio of the transformer:

[0063]

[0064] Where N is the actual turns ratio of the transformer, U2 is the induced voltage of the secondary winding, and U3 is the induced voltage of the auxiliary winding. U2 and U3 are obtained by voltage measurement units connected to the output terminals of the secondary winding and the auxiliary winding, respectively. n3 is the actual number of turns of the auxiliary winding.

[0065] By applying a constant AC current to the through-the-wire CT and simultaneously measuring the induced voltages of the secondary and auxiliary measurement windings, the error caused by the excitation current of the voltage-applied winding can be effectively eliminated. Because both the secondary and auxiliary windings are open-circuited during the test, the induced electromotive force is directly proportional to the number of turns, making the measurement of the transformer's actual turns ratio more accurate and stable, improving the measurement accuracy and reliability of through-the-wire CT ratio tests. Furthermore, compared with direct measurement methods that pass large currents through the primary side, this ratio test method does not require high currents, has the advantages of small test equipment capacity, and is safe and reliable.

[0066] Furthermore, the characteristic curve generating unit completes the curve generation in the following manner:

[0067] The converted equivalent excitation voltage and the corresponding excitation current are processed in groups to draw the VA characteristic curve of the transformer;

[0068] The complex error derived from the error calculation unit is decomposed into amplitude error and phase error. Under different loads or different excitation states, the amplitude error-load curve and phase error-load curve of the transformer are generated as error characteristic curves, which are used to comprehensively evaluate the law of change of the measurement error of the transformer with working conditions.

[0069] Example 2:

[0070] This embodiment should be understood to include at least all the features of any of the aforementioned embodiments and be further improved thereon;

[0071] This embodiment provides a handheld intelligent transformer testing system, which includes a power signal generation module, a signal conditioning and acquisition module, a data processing and calculation module, a communication data management module, and a user interaction module; the power signal generation module is used to provide the power required by the system to test the transformer and generate a high-precision, low-noise test signal; the signal conditioning and acquisition module is used to collect the test signal output by the transformer and condition the test signal to within the standard input range of the system analog-to-digital converter; the data processing and calculation module is used to calculate and analyze the collected test signal to obtain the error parameter of the transformer; the communication data management module is used to complete data transmission and data management between the edge end and the management end; and the user interaction module is used to display system data to the tester through the system's touch display interface;

[0072] Furthermore, the edge end is a local terminal of a handheld transformer intelligent test system, and the management end is a centralized device management platform;

[0073] Furthermore, the communication data management module includes a data interface unit, a data storage unit, and a trend analysis unit; the data interface unit is used to open a 4G private network access interface to complete data communication between the edge end and the management end; the data storage unit is used to locally cache the collected transformer output test signals and system analysis and processing data at the edge end to ensure that data is not lost in the event of communication anomalies and is automatically retransmitted after communication is restored; the trend analysis unit is used to perform intelligent evaluation of transformer performance based on the transformer's historical test results at the management end;

[0074] Specifically, if Figure 6 、 Figure 7 The specific workflow of the trend analysis unit is as follows:

[0075] For a certain transformer:

[0076] S31: Obtain historical test results of the transformer, where each historical test record in the historical test results includes a test time corresponding to the historical test record and an error characteristic curve in the historical test record;

[0077] S32: extracting a ratio difference value and an angle difference value under standard load conditions from the error characteristic curve in each historical test record; the ratio difference value is obtained by selecting the amplitude error of a corresponding standard load point from the amplitude error-load curve; the angle difference value is obtained by selecting the phase error of a corresponding standard load point from the phase error-load curve;

[0078] S33: Calculate the performance trend change index of the transformer:

[0079]

[0080] Among them, S is the transformer performance trend change index, which is used to quantify the degree of change in transformer performance; α1 is the weight coefficient of the ratio difference change in the transformer performance trend change index, which is used to unify the differences in magnitude and unit between the ratio difference change and the angular difference change, and is set by pre-experimentation; α2 is the weight coefficient of the angular difference change in the transformer performance trend change index, which is used to unify the differences in magnitude and unit between the ratio difference change and the angular difference change, and is set by pre-experimentation; i is the index number of the historical test record, and the closer the historical test record is to the current time, the larger the index number; N is the total number of historical test records; Δf i is the ratio difference change of the i-th historical test record, Δk i is the angular difference change in the i-th historical test record, ω i is the time weight coefficient of the i-th historical test record, satisfying:

[0081] Δf i =f i -f i-1 ;

[0082] Δk i =k i -k i-1 ;

[0083] ω i =exp(-λ·Δt i );

[0084] Among them, f i is the difference value of the i-th historical test record, f i-1 is the difference between the i-1th historical test record, k i is the angular difference of the i-th historical test record, k i-1 is the angular difference of the i-1th historical test record, t i is the time difference between the i-th historical test record and the n-th historical test record, λ is the time decay factor, which is used to control the influence of time decay on the time weight coefficient and is set by pre-experimentation;

[0085] S34: Compare the transformer performance trend change index with the set performance threshold. When the transformer performance trend change index is greater than the performance threshold, it is determined that the transformer has a performance degradation trend, and an early warning message is generated and pushed to the management end user;

[0086] This solution introduces a time-weighted processing mechanism for historical test data on the management side. Based on the changing trends of the ratio difference and angle difference extracted under standard load, it automatically quantifies the performance changes of the transformer and forms a performance trend change indicator. The system can intelligently judge the potential degradation trend of the transformer and generate early warning information based on the time evolution law, realizing an intelligent upgrade from static detection to dynamic trend assessment, greatly improving the accuracy, real-time performance and automation level of transformer status assessment, and effectively supporting the intelligent operation and maintenance and preventive maintenance of power grid equipment.

[0087] The contents disclosed above are only preferred feasible embodiments of the present invention and do not limit the scope of protection of the present invention. Therefore, all equivalent technical changes made using the contents of the present invention description and drawings are included in the scope of protection of the present invention. In addition, the elements therein can be updated as technology develops.

Claims

1. A handheld intelligent transformer testing system, characterized in that: The system includes a power signal generation module, a signal conditioning and acquisition module, a data processing and calculation module, a communication data management module, and a user interaction module; the power signal generation module is used to provide the power required by the system to test the transformer and generate a high-precision, low-noise test signal; the signal conditioning and acquisition module is used to collect the test signal output by the transformer and condition the test signal to the standard input range of the system analog-to-digital converter; the data processing and calculation module is used to calculate and analyze the collected test signal to obtain the error parameters of the transformer; the communication data management module is used to complete data transmission and data management between the edge end and the management end; the user interaction module is used to display system data to the tester through the system's touch display interface; The power signal generation module includes a DC power supply unit, a variable frequency AC signal unit, a signal control unit and a protection isolation unit; the DC power supply unit is used to provide a stable DC power supply for each functional module of the system; the variable frequency AC signal unit is used to output an adjustable AC test signal; the signal control unit is used to control the output mode of the AC test signal according to the test requirements; the protection isolation unit is used to realize power isolation protection between the AC test signal and the test object.

2. A handheld transformer intelligent testing system according to claim 1, characterized in that: The signal conditioning and acquisition module includes a signal amplification unit, a signal filtering unit, a synchronous sampling unit and an input protection unit; the signal amplification unit is used to adjust the amplitude of the test signal output by the transformer so that the test signal amplitude adapts to the standard input range of the system analog-to-digital converter; the signal filtering unit is used to filter the test signal output by the transformer; the synchronous sampling unit is used to realize multi-channel synchronous acquisition of the test signal output by the transformer; the input protection unit is used to prevent external abnormal signals from damaging the analog-to-digital converter.

3. The handheld intelligent transformer testing system according to claim 1, characterized in that: The data processing and calculation module includes an error calculation unit, an excitation parameter extraction unit, a turns ratio analysis unit and a characteristic curve generation unit; the error calculation unit is used to calculate the error parameters of the transformer based on a nonlinear equivalent circuit model; the excitation parameter extraction unit is used to extract the standard excitation admittance parameters; the turns ratio analysis unit is used to obtain the actual turns ratio of the transformer; and the characteristic curve generation unit is used to generate a VA characteristic curve and an error characteristic curve.

4. A handheld transformer intelligent testing system according to claim 3, characterized in that: The error calculation unit obtains the error parameter of the mutual inductor through the following formula: Where ε is the complex error of the transformer, that is, the error parameter, which is used to characterize the amplitude error and phase error of the transformer under specific load conditions; R CT is the secondary winding resistance of the transformer, which is obtained by applying a DC current and measuring the voltage drop according to Ohm's law; j is an imaginary unit used to represent the phase characteristics of the AC signal in the complex domain; L s is the leakage inductance of the secondary winding of the transformer, reflecting the inductive reactance component caused by the leakage magnetic flux in the secondary winding; Z b is the secondary load impedance of the transformer, which is a known measurable parameter; is the power factor angle of the secondary load, which indicates the phase difference between the secondary voltage and the secondary current. It is obtained by synchronously sampling the secondary voltage and current signals and calculating the phase difference. Y is the standard excitation admittance parameter, which indicates the composite admittance of the transformer core under rated working conditions. SR is the rated current ratio of the transformer, which is a known parameter. N is the actual turns ratio of the transformer.

5. The handheld intelligent transformer testing system according to claim 3, characterized in that: The excitation parameter extraction unit obtains the standard excitation admittance parameter of the transformer in the following manner: S11: Applying an AC voltage signal with controllable amplitude and gradually decreasing frequency to the secondary side of the transformer through the signal control unit. The starting frequency is set to the standard power frequency, and the frequency is gradually reduced with a preset step length until the minimum test frequency is reached. S12: At each test frequency point, the voltage signal and excitation current signal applied on the secondary side of the transformer are collected in real time; S13: For each set of collected voltage signals and excitation current signals, process them according to the frequency conversion formula to convert the excitation voltage under the test conditions into the equivalent excitation voltage under the standard power frequency. The conversion formula is: Among them, U is the equivalent excitation voltage at standard power frequency, U x Indicates that in the variable frequency test, the secondary side of the transformer is at the test frequency f x The voltage signal applied under the test frequency is x; the index number of the test frequency point is f b is the frequency value corresponding to the standard power frequency; S14: based on the converted equivalent excitation voltage and the corresponding excitation current, draw the VA characteristic curve of the transformer; S15: Derive the excitation admittance Y of the transformer under standard power frequency conditions based on the VA characteristic curve data.

6. The handheld intelligent transformer testing system according to claim 3, characterized in that: The turns ratio analysis unit obtains the actual turns ratio of the transformer in the following manner: S21: Applying an adjustable power frequency AC current to the transformer through-core voltage winding via the power signal generation module, so that the transformer core generates a stable AC magnetic flux; S22: When the core flux is stable, measure the induced voltage across the transformer secondary winding and the auxiliary measurement winding simultaneously. Since both the secondary winding and the auxiliary winding are in an open circuit state and share the same core flux, the induced voltage between them is proportional to the number of winding turns. S23: According to the principle that the induced electromotive force is proportional to the number of turns, the turns ratio of the transformer secondary winding to the auxiliary winding is taken as the actual turns ratio of the transformer.

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