Transformer bushing dielectric loss absolute method live-line test diagnosis method, system, equipment and medium

Abstract

The invention is suitable for the field of bushing insulation diagnosis, and discloses a transformer bushing dielectric loss absolute method live-line test diagnosis method, system, equipment and medium, and the method comprises the steps: obtaining a dielectric loss value of a bushing in operation through a bushing live-line test; calculating a dielectric loss value increment between the dielectric loss value and the initial dielectric loss value based on the bushing dielectric loss value; obtaining a first judgment conclusion of the insulation state of the sleeve based on comparison between the dielectric loss value increment and a dielectric loss detection threshold value; transformer upper oil temperature is obtained, the change trend of the dielectric loss value along with the transformer upper oil temperature is analyzed, and a second judgment conclusion is obtained; based on the first judgment conclusion and the second judgment conclusion, the insulation condition of the sleeve is judged, and corresponding processing is executed. According to the invention, through temperature and live-line test dual diagnosis, operation is simple and easy to implement, equipment power failure is not needed, and application scene universality is high; the health state of the bushing is mastered, the diagnosis accuracy is improved, and safe and stable operation of the transformer is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of bushing insulation diagnosis, in particular to a transformer bushing dielectric loss absolute method live test diagnosis method, system, device and medium. BACKGROUND

[0002] At present, the common test project for detecting the state of the bushing is still to carry out 10kV dielectric loss and capacitance measurement under power-off, but it is not sensitive to the initial damp defect of the bushing and is difficult to truly reflect the operation condition of the device.

[0003] Only by means of live test or online monitoring can the insulation condition of the running bushing be timely mastered, so as to prevent the occurrence of bushing sudden failure. The dielectric loss and capacitance live online detection technology is widely used at present, and its detection methods mainly include "relative method" and "absolute method". The "relative method" does not need to extract the secondary voltage signal of the bus voltage mutual inductor, so the angle difference problem of the absolute method can be avoided, in addition, the operation conditions between devices are relatively close, and the influence of external factors is relatively close, so the influence of these factors can be offset to a certain extent, the stability of the data is improved, and the judgment is convenient, so it becomes the mainstream method, and the corresponding industry standard is formed. However, the biggest disadvantage of this method is that at least two capacitance type devices under the same bus voltage are needed to carry out the test, which is not universal and cannot be carried out on all running bushings. In addition, the relative method related to a large number of literatures does not give the threshold of the relative method judgment method, and the industry standard gives the judgment threshold that "the relative dielectric loss factor change should not exceed 0.003", and the determination method is obtained by using the results of defect probability and mathematical statistics, but the reason for the change of the characteristic parameters of the test piece is not explained from the mechanism, so the persuasiveness is insufficient, the representativeness is not enough, and therefore the state control value is differentiated according to the production management needs and a large amount of data accumulation, so the judgment method is not perfect and still needs further research. Therefore, it is necessary to carry out research on other diagnosis methods, so as to fully master the running state of all bushings.

[0004] The "absolute method" has higher universality and can be carried out in all connection mode substations, but is affected by environment, system operation condition, PT angle difference and phase-to-phase interference, etc., so the error of the dielectric loss test result is larger compared with the 10kV dielectric loss test result carried out under power-off, and it is difficult to directly judge the insulation condition of the device from the size of the measurement result, so most traditional concepts consider that the absolute method is not feasible and is abandoned, and the research and application of the absolute method are less. Therefore, a method with universality and accurate measurement is needed to judge the insulation state of the bushing. SUMMARY

[0005] In view of the above existing problems, the present application is proposed.

[0006] Therefore, the application provides a transformer bushing dielectric loss absolute method live test diagnosis method, system and device and a dielectric solution to the problems of the prior art, such as the limitation of test conditions and test instruments, which leads to great difficulty in development and low popularization, and the imperfectness of the relative method.

[0007] To solve the above technical problems, the application provides the following technical solutions. In a first aspect, the application provides a transformer bushing dielectric loss absolute method live test diagnosis method, comprising: obtaining a dielectric loss value of the bushing in operation through live test of the bushing; calculating a dielectric loss value increment of the dielectric loss value and an initial dielectric loss value based on the dielectric loss value of the bushing; obtaining a first judgment conclusion of the insulation state of the bushing based on comparison of the dielectric loss value increment and a dielectric loss detection threshold value; obtaining an upper oil temperature of the transformer, analyzing the change trend of the dielectric loss value with the upper oil temperature of the transformer, and obtaining a second judgment conclusion; judging the insulation condition of the bushing based on the first judgment conclusion and the second judgment conclusion and performing corresponding processing.

[0008] As a preferred scheme of the transformer bushing dielectric loss absolute method live test diagnosis method, the calculation of the dielectric loss value increment of the dielectric loss value and the initial dielectric loss value based on the dielectric loss value of the bushing comprises: the difference between the current dielectric loss value and the initial dielectric loss value is calculated as the dielectric loss value increment based on the dielectric loss value of the bushing obtained through live test of the bushing, wherein the initial dielectric loss value is the dielectric loss measurement value of the first live test after the equipment is put into production.

[0009] As a preferred scheme of the transformer bushing dielectric loss absolute method live test diagnosis method, the obtaining of the first judgment conclusion of the insulation state of the bushing based on comparison of the dielectric loss value increment and the dielectric loss detection threshold value comprises: the dielectric loss detection threshold value comprises a first threshold value and a second threshold value, wherein the second threshold value is greater than the first threshold value; if the dielectric loss value increment is not greater than the first threshold value, the first judgment conclusion is a normal state; if the dielectric loss value increment is between the two threshold values, the first judgment conclusion is a pre-warning state; if the dielectric loss value increment is not less than the second threshold value, the first judgment conclusion is an abnormal state.

[0010] As a preferred scheme of the transformer bushing dielectric loss absolute method live test diagnosis method, the obtaining of the second judgment conclusion by obtaining the upper oil temperature of the transformer and analyzing the change trend of the dielectric loss value with the upper oil temperature of the transformer comprises: When the bushing insulation condition is in a warning state or an abnormal state, a second judgment is made within the first preset time period and the second preset time period, respectively: Multiple sets of dielectric loss values ​​and transformer upper oil temperature data were obtained by conducting multiple online tests under different oil temperature conditions. Based on the analysis of the changing trends of multiple sets of dielectric loss values ​​and transformer upper oil temperature data, a second judgment conclusion was obtained.

[0011] As a preferred embodiment of the transformer bushing dielectric loss absolute method for live-line testing and diagnosis described in this invention, wherein: when in an early warning state, the bushing insulation condition is determined based on a second judgment conclusion, and corresponding processing is performed, including: When in a warning state, the second judgment conclusion is that the dielectric loss value increases with the rise of oil temperature, then the bushing has an insulation defect, and it should be handled in conjunction with the power outage maintenance cycle; When in a warning state, the second judgment is that the oil temperature rises while the dielectric loss value remains basically constant, then the bushing insulation is normal.

[0012] As a preferred embodiment of the transformer bushing dielectric loss absolute method for live-line testing and diagnosis described in this invention, when an abnormal state is encountered, the bushing insulation condition is determined based on the second judgment conclusion, and corresponding processing is performed, including: When in an abnormal state, the second judgment conclusion is that the dielectric loss value increases with the increase of oil temperature, then the bushing has an insulation defect, and power should be cut off for handling. When in an abnormal state, the second judgment is that the oil temperature rises while the dielectric loss value remains basically constant, then the bushing has an insulation abnormality. During operation, continuous monitoring and interference elimination are required. As a preferred embodiment of the transformer bushing dielectric loss absolute method live-line testing and diagnostic method described in this invention, the method for obtaining the bushing dielectric loss value through live-line testing includes: The current signal of the bushing end screen and the bus voltage signal are obtained by conducting live bushing tests. The bushing dielectric loss value is obtained by performing analog-to-digital conversion on the bushing end screen current signal and the bus voltage signal.

[0013] Secondly, this invention provides a transformer bushing dielectric loss absolute method live-line testing and diagnostic system, comprising: The acquisition module is used to obtain the dielectric loss value of the bushing during operation through live bushing testing; The calculation module is used to calculate the increment of dielectric loss value compared to the initial dielectric loss value, based on the dielectric loss value of the casing. The first judgment module is used to obtain the first judgment conclusion on the insulation status of the bushing based on the comparison between the dielectric loss value increment and the dielectric loss detection threshold. The second judging module is used for obtaining the upper-layer oil temperature of the transformer, analyzing the change trend of the dielectric loss value with the upper-layer oil temperature of the transformer, and obtaining a second judging conclusion. The executing module is used for judging the insulation condition of the bushing and performing corresponding processing based on the first judging conclusion and the second judging conclusion.

[0014] In a third aspect, the present application provides an electronic device, comprising: a memory and a processor; The memory is used for storing computer executable instructions, and the processor is used for executing the computer executable instructions, so as to realize the steps of the transformer bushing dielectric loss absolute method on-line test diagnosis method.

[0015] In a fourth aspect, the present application provides a computer readable storage medium, which stores computer executable instructions, and the computer executable instructions are executed by the processor to realize the steps of the transformer bushing dielectric loss absolute method on-line test diagnosis method.

[0016] Compared with the prior art, the present application has the following beneficial effects: the absolute method on-line test is used to measure at the operating voltage, so that the current dielectric loss value of the bushing can be truly reflected; the double-evidence diagnosis logic is constructed with the dielectric loss value-bushing temperature as the core, so that the diagnosis closed loop is formed; the operation is simple and easy to implement, and the equipment does not need to be powered off, and does not need to rely on the horizontal comparison data of the same type of bushing, so that the industry pain point that the application scene of the "relative method" is limited is solved, and the universality is strong; the technical prejudice of the absolute method in the prior art is overcome: the simple "absolute method" measurement is greatly affected by the field interference factors, and is difficult to be used for accurate diagnosis; the health status of the bushing is accurately mastered, and the safe and stable operation of the power grid main equipment such as the transformer is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating any creative labor.

[0018] Figure 1 The overall flowchart of the transformer bushing dielectric loss absolute method on-line test diagnosis method described in an embodiment of the present application.

[0019] Figure 2 The dielectric loss value test principle diagram of the transformer bushing dielectric loss absolute method on-line test diagnosis method described in an embodiment of the present application.

[0020] Figure 3The curve graph of the dielectric loss of the bushing at different oil temperatures and voltage changes of the bushing of the transformer sleeve dielectric loss absolute method on-line test diagnosis method of one embodiment of the application.

[0021] Figure 4 The curve graph of the dielectric loss of the bushing at different oil temperatures and voltage changes of the bushing of the transformer sleeve dielectric loss absolute method on-line test diagnosis method of one embodiment of the application.

[0022] Figure 5 The curve graph of the dielectric loss of the bushing at different oil temperatures and voltage changes of the bushing of the transformer sleeve dielectric loss absolute method on-line test diagnosis method of one embodiment of the application.

[0023] Figure 6 The curve graph of the dielectric loss of the bushing at different oil temperatures and voltage changes of the bushing of the transformer sleeve dielectric loss absolute method on-line test diagnosis method of one embodiment of the application.

[0024] Figure 7 The curve graph of the dielectric loss of the bushing at different oil temperatures and voltage changes of the bushing of the transformer sleeve dielectric loss absolute method on-line test diagnosis method of one embodiment of the application.

[0025] Figure 8 The curve graph of the dielectric loss of the bushing at different oil temperatures and voltage changes of the bushing of the transformer sleeve dielectric loss absolute method on-line test diagnosis method of one embodiment of the application.

[0026] Figure 9 The curve graph of the dielectric loss of the bushing at different oil temperatures and voltage changes of the bushing of the transformer sleeve dielectric loss absolute method on-line test diagnosis method of one embodiment of the application.

[0027] Figure 10 The curve graph of the dielectric loss of the bushing at different oil temperatures and voltage changes of the bushing of the transformer sleeve dielectric loss absolute method on-line test diagnosis method of one embodiment of the application. DETAILED DESCRIPTION

[0028] To make the above objectives, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the protection scope of the present application.

[0029] Embodiment 1, refer to Figure 1 , one embodiment of the present application provides a transformer bushing dielectric loss absolute method on-line test diagnosis method, comprising: S100: obtaining the dielectric loss value of the bushing in operation through on-line test of the bushing. S200: Based on the casing dielectric loss value, calculate the dielectric loss increment between the initial dielectric loss value and the dielectric loss value; S300: Based on the comparison between the dielectric loss increment and the dielectric loss detection threshold, the first judgment conclusion of the bushing insulation status is obtained; S400: Obtain the upper oil temperature of the transformer, analyze the trend of dielectric loss value with the upper oil temperature of the transformer, and obtain the second judgment conclusion; S500: Based on the first and second judgment conclusions, determine the bushing insulation status and perform corresponding processing.

[0030] It should be noted that transformer bushings have a multi-layer composite insulation structure. During operation, parameters such as the internal electric field distribution, operating temperature, mechanical stress, and ambient humidity of the bushing vary significantly. This causes dynamic changes in the dielectric loss factor and capacitance of the main insulation and the grounding part of the end screen. Influenced by the coupling effect of temperature and electric fields, the insulation performance of the bushing also changes. Furthermore, the operating bushing is under continuous high electric field and temperature cycling, making accurate measurement of the absolute value of dielectric loss and insulation performance difficult, and the early warning of latent defects often has a lag. Simultaneously, due to long-term electromagnetic vibration, thermal expansion and contraction, and seal aging, partial discharge or insulation moisture may occur inside the bushing, thereby compromising the strength of the main insulation. Strong electromagnetic interference and difficulties in signal extraction during operation pose significant challenges to the "absolute method" dielectric loss measurement and can also lead to bushing breakdown due to the cumulative effect of insulation degradation. Therefore, conducting online live detection of dielectric loss and capacitance using the "absolute method" is of significant engineering importance.

[0031] Therefore, to address the aforementioned issues of universality and accuracy in judgment, the following steps (S100-S500) are used: absolute dielectric loss measurement is performed to obtain the dielectric loss increment, achieving the first level of judgment; capacitance-based live detection technology is employed to obtain the changing trends of the transformer upper oil temperature and bushing dielectric loss, achieving the second level of judgment; and by combining the first and second levels of judgment, an accurate judgment of the bushing insulation status is obtained, and corresponding processing is performed accordingly, thus achieving the judgment and processing of the bushing insulation status.

[0032] Example 2, refer to Figure 1 As an embodiment of the present invention, based on the above embodiment, a live-line test and diagnosis method for absolute dielectric loss of transformer bushings is provided.

[0033] In this embodiment of the application, step S100, which involves obtaining the dielectric loss value of the bushing during operation through a live bushing test, includes: Specifically, the absolute method for measuring dielectric loss will be carried out only after confirming that the operating mode of the transformer used in this test and the voltage transformer used to obtain the reference voltage are consistent with the historical test conditions.

[0034] It should be noted that different operating modes can affect test results due to PT angle difference and phase-to-phase interference, leading to certain errors in the test values. Comparing these values ​​with historical values ​​would then have low reliability. However, if the operating mode remains consistent, these influencing factors can be considered fixed errors, resulting in higher reliability when comparing test values ​​with historical values ​​each time. Meanwhile, the operating modes of transformers within substations remain largely unchanged; most transformers operate on a fixed busbar in actual power grid operation, providing the ideal conditions for applying the absolute method. When using the absolute method for live bushing testing, the test voltage is the same as the operating voltage. This is higher than the 10kV dielectric loss and capacitance measurements commonly performed in outage tests, making it easier to detect defects in bushing insulation.

[0035] Furthermore, the absolute method measures the device under test through a signal sampling unit connected in series with the grounding wire of the device under test's end screen. current signal The voltage signal is then collected using a bus voltage transformer that runs on the same busbar as the device under test. The frequency f is obtained, and the phase difference between voltage and current is obtained using phase detection techniques, such as lock-in amplifiers or digital signal processing techniques, to calculate the active power. and reactive power This allows for the calculation of the equivalent capacitance of the device under test. and dielectric loss factor The calculation principle is as follows:

[0036]

[0037] For example, such as Figure 2 The diagram shows the test principle of simultaneously acquiring the bushing end screen current signal and the secondary side voltage signal of the bus voltage transformer through a sensor, converting them from analog to digital signals, and then using relevant mathematical algorithms to perform time-domain or frequency-domain operations on the signals to calculate the fundamental phase difference of the voltage and current, thereby obtaining the dielectric loss angle and capacitance of the bushing.

[0038] It should be noted that for capacitive devices, the dielectric loss angle is very small, the current obtained from the end screen is in the milliampere range, and its resistive component is only in the microampere range, which can be ignored. Therefore, the capacitance measured by the absolute method is relatively accurate.

[0039] In this embodiment of the application, step S200, based on the casing dielectric loss value, calculates the dielectric loss increment between the dielectric loss value and the initial dielectric loss value, including: Specifically, the increment of dielectric loss value obtained from live bushing testing Defined as the difference between the dielectric loss value and its initial dielectric loss value:

[0040] wherein, is the dielectric loss value obtained by the present live test; is the dielectric loss value obtained by the first live test after the bushing is put into operation.

[0041] It should be noted that the bus PT angle difference and the phase-to-phase interference are the main interference factors of the absolute method test, but the error value of the fixed bus PT selected under the stable power grid operation mode is basically unchanged; the influence of the environmental temperature, voltage frequency fluctuation, system harmonics and the through-type current transformer is small. Although the live test of the dielectric loss by the absolute method has many interference factors, the test data error is stable and only fluctuates in a small range, which is completely insufficient to cover the large dielectric loss increment of the defective bushing under the dual action of high voltage and high oil temperature; and the dielectric loss increment is the subtraction of the two test values, which can offset the influence of the PT angle difference, phase-to-phase interference and other stable interference factors to a large extent, and is more close to the real dielectric loss increment of the bushing.

[0042] In the embodiment of the present application, the first judgment conclusion of the bushing insulation state is obtained by comparing the dielectric loss value increment with the dielectric loss detection threshold in step S300, including: Specifically, the dielectric loss detection threshold is set according to the test procedure, including the first threshold 0.15% and the second threshold 0.3%.

[0043] Further, the first judgment conclusion of the bushing insulation state is obtained by comparing the dielectric loss value increment with the dielectric loss detection threshold: If the first judgment conclusion is normal state; If the first judgment conclusion is early warning state; If the first judgment conclusion is abnormal state; In an optional embodiment, the dielectric loss detection threshold in step S300 can also be determined based on the statistical analysis results of a large number of historical normal bushing and known defective bushing sample data, so that the dielectric loss detection threshold is no longer a fixed value, which embodies the intelligentization of threshold setting.

[0044] In another optional embodiment, the dielectric loss detection threshold in step S300 can also be dynamically adjusted according to the model, voltage grade and operation time of the bushing to realize individualized diagnosis and improve the accuracy of bushing detection.

[0045] In the embodiment of the present application, the second judgment conclusion is obtained by analyzing the change trend of the dielectric loss value with the upper layer oil temperature of the transformer in step S400, including: Specifically, a time period is set according to the equipment risk assessment, such as a first preset time period of 6 months and a second preset time period of 3 months.

[0046] When the bushing insulation state is in the early warning state, the bushing dielectric loss value and the corresponding upper oil temperature of the transformer are tracked and tested within 6 months, the bushing dielectric loss value data in the range of 20-70°C is selected, 5 groups of dielectric loss value and temperature data are selected as evenly as possible at every 10°C interval, a dielectric loss value-temperature change graph is drawn, and the correlation between the dielectric loss value and the temperature is analyzed.

[0047] When the bushing insulation state is in the abnormal state, the bushing dielectric loss value and the corresponding upper oil temperature of the transformer are tracked and tested within 3 months, the bushing dielectric loss value data in the range of 20-70°C is selected, 5 groups of dielectric loss value and temperature data are selected as evenly as possible at every 10°C interval, a dielectric loss value-temperature change graph is drawn, and the correlation between the dielectric loss value and the temperature is analyzed.

[0048] It should be noted that the heat generated by the transformer operating loss increases the oil temperature, and with the change of the transformer load and the ambient temperature, the upper oil temperature generally fluctuates in the range of 20-80°C, and the lower part of the bushing is immersed in the oil at the top of the transformer, and the temperature of the bushing body can be approximately considered as being basically consistent with the upper oil temperature of the transformer, and changes with the change of the upper oil temperature of the transformer. Generally, the normal oil-paper bushing dielectric loss value decreases or does not change obviously with the increase of the temperature in the range of 20-70°C. However, the dielectric loss value of the bushing with insulation defects increases obviously with the increase of the temperature. The dielectric loss value of the defective bushing increases with the increase of the temperature at different measurement voltages, and almost has an exponential growth relationship. That is, when the live test is carried out on the running transformer, the live dielectric loss value of the bushing with insulation defects should increase obviously under the double action of high voltage and high oil temperature, not only far greater than the test error fluctuation range, but also the increment is obvious enough to sensitively reflect the early insulation deterioration of the bushing. The live dielectric loss value of the normal bushing changes little.

[0049] In an alternative embodiment, the drawing of the dielectric loss value-temperature change graph in step S400 to analyze the correlation between the dielectric loss value and the temperature can also be extracted by a quantitative mathematical model and a characteristic parameter. For example, after obtaining the dielectric loss value-temperature data points, linear fitting is performed on the data points, a linear model is adopted, the slope is calculated, and the slope of the normal bushing should be close to 0 or negative; and the slope of the defective bushing presents a significant positive value.

[0050] In another alternative embodiment, the correlation between the dielectric loss value and the temperature can also be extracted by quantifying a mathematical model and a characteristic parameter in the step S400 of drawing the dielectric loss value-temperature change graph. For example, after obtaining the dielectric loss value-temperature data points, the data points are subjected to nonlinear fitting, an exponential model is adopted or a temperature sensitivity coefficient is defined, the curvature is calculated or the average change amount of the dielectric loss value caused by the unit temperature change in the specified temperature range is calculated.

[0051] For example, two 110kV bushings with early insulation defects from different manufacturers are selected as samples (a bushing and b bushing), and high-temperature dielectric loss tests are respectively performed at room temperature 20℃ and near operating oil temperature 70℃, as shown in Figure 3 、 Figure 4 The dielectric loss of the a and b bushings varies with the voltage at 20℃ and 70℃.

[0052] Table 1 High-voltage dielectric loss test data of the two defective bushings at 20℃ and 70℃

[0053] Referring to Table 1, the dielectric loss values of the two bushings with insulation defects are significantly increased under the action of high voltage or under the action of high oil temperature, and the increase is more obvious under the joint action of the two, which is increased by 0.69% and 0.67% respectively. The increased value is related to the insulation damage degree of the tested bushing, the insulation structure of the bushing and the oil temperature, but the increase is indeed obvious and easy to identify, which is far greater than the error fluctuation range of the live test.

[0054] In the embodiment of the present application, based on the first judgment conclusion and the second judgment conclusion in the step S500, the insulation condition of the bushing is judged and corresponding processing is performed, including: When in the pre-warning state, the second judgment conclusion is that the dielectric loss value increases with the increase of the oil temperature, and the bushing has insulation defects, which is handled in combination with the power-off maintenance period; When in the pre-warning state, the second judgment conclusion is that the dielectric loss value is basically constant with the increase of the oil temperature, and the insulation condition of the bushing is normal.

[0055] When in the abnormal state, the second judgment conclusion is that the dielectric loss value increases with the increase of the oil temperature, and the bushing has insulation defects, which is handled by power-off; When in the abnormal state, the second judgment conclusion is that the dielectric loss value is basically constant with the increase of the oil temperature, and the bushing has insulation abnormalities, which is continuously monitored and the reason is found out to exclude interference in operation; In the embodiment 3, referring to Figures 5-9 As an embodiment of the present application, based on the above-mentioned embodiments, an actual application case of the absolute method transformer bushing insulation state diagnosis method is provided to verify the implementability and effect thereof; 220 kV substation No. 3 main transformer was put into operation in 2014. After installing the live test device of bushing in 2019, the absolute method live test was carried out once a year. In September 2023, the test found that the dielectric loss value of the 110 kV side B phase bushing was 0.7%, which increased by 0.597% compared with the initial value of 0.113%. The capacitance was normal, and the bushing was judged to be abnormal. The continuous tracking test was carried out. In February 2024, the outage test and replacement of the bushing were carried out.

[0056] Table 2: Dielectric loss pre-test data of bushing in each outage

[0057] Referring to Table 2, the dielectric loss test value of the three-phase bushing in each year (including the outage test after the serious abnormality of the live test) is stable, and the test result is qualified. It should be noted that the 2024 is the outage test after the serious abnormality of the live test.

[0058] Table 3: Dielectric loss live test data of A, B and C bushings in each outage

[0059] Referring to Table 3, the dielectric loss value of the B phase bushing actually increased by 0.22% in 2021 compared with the initial test value in 2019. However, since the outage pre-test was also carried out in 2021, the outage pre-test result was good, so it was decided to continue to observe. In 2023, the dielectric loss value of the B phase bushing was 0.7%, which increased by 0.597% compared with the initial measurement value. It was decided to prepare bushing spare parts for replacement and at the same time shorten the live test period to continuously monitor the state of the bushing.

[0060] The change of the dielectric loss test value of the B phase bushing in the order of test time is shown in Figure 5 , which appears to be high and low, even a large decrease, which is easy to misjudge the live test value as unreliable. The change of the dielectric loss test value of the three-phase bushing and the upper oil temperature of the transformer is shown in Figure 6 . Although there is unavoidable interference and certain deviation of the test value, it can be clearly seen from the trend line that the live dielectric loss value of the A and C phase bushings remains basically unchanged or slightly decreases with the increase of the upper oil temperature, while the live dielectric loss value of the B phase bushing rapidly increases with the increase of the upper oil temperature, which meets the two criteria, and it can be judged that the B phase bushing has insulation defects.

[0061] Since the 10 kV dielectric loss test result after outage is good, in order to exclude the influence that the 10 kV conventional dielectric loss test method cannot truly reflect the operation state of the bushing, and further verify the effectiveness of the live test of the bushing, the replaced B phase bushing was subjected to various diagnostic tests and disassembly inspection in the laboratory.

[0062] Table 4: Test items, results and conclusions

[0063] Referring to Table 4, the experimental items, test results and conclusions are carried out.

[0064] According to the analysis of the test results, the data of the conventional 10kV dielectric loss test, oil test and partial discharge test are normal, the data of the dielectric spectrum test and high voltage dielectric loss test indicate that the bushing is in the initial stage of insulation deterioration and dampness, the degree of polymerization of the insulation paper decreases obviously, and it is judged that the bushing is caused by the aging of the insulation paper, which leads to the initial insulation dampness deterioration of the bushing. The accuracy of the absolute method of charged testing and the double evidence diagnosis method is verified. At the same time, the bushing is in the initial stage of insulation deterioration and dampness, and the absolute method of charged testing has a large data change, which shows that the absolute method of charged testing can sensitively and early detect the insulation defect of the bushing and truly reflect the running state of the bushing.

[0065] Example 4, refer to Figure 10 As an embodiment of the present application, based on the above-mentioned embodiment, an actual application case of the absolute method of transformer bushing insulation state diagnosis method is provided to verify its implementability and effect; 110kV some transformer station No. 2 main transformer was put into production in 2000, and the bushing charged testing device was installed in 2020, and the absolute method of charged testing was carried out once a year. In February 2023, it was found that the test dielectric loss value of the 110kV side Y phase bushing was 0.61%, which was increased by 0.446% compared with the initial measurement value of 0.164%, and the capacitance was normal. It is judged that the bushing is abnormal, and the continuous tracking test is carried out. The relative method test cannot be carried out for judgment when the two main transformers of the transformer station are in parallel operation.

[0066] Table 5 X, Z, Y bushing dielectric loss charged test data

[0067] Referring to Table 5, the X, Z, Y bushing dielectric loss charged test data.

[0068] During the observation and tracking test, the change of the temperature of the upper layer of the transformer and the test value of the dielectric loss of the three-phase bushing was observed, as shown in Figure 10 As shown by the trend line, the dielectric loss value of the three-phase bushing charged basically remains unchanged or slightly decreases with the change of temperature, which does not meet the second criterion, and it is judged that the bushing has no insulation defect, and the abnormal increase of the dielectric loss value of the Y phase bushing charged test may be caused by other interference.

[0069] To find out the reason for the increase of the dielectric loss of the Y-phase bushing under voltage, the relevant equipment was inspected, and infrared temperature measurement found that the Y-phase secondary connection box of the voltage transformer for taking voltage signal had an abnormal temperature compared with the other two phases, suspecting that there was a defect in the secondary connection box of the voltage transformer, which caused the secondary voltage angle deviation to affect the test value of the bushing under voltage. The 110kV No. 2 main transformer and voltage transformer were inspected under power-off, and the test of the three-phase bushing of the transformer and the voltage transformer was normal. The inspection found that the N-end discharge gap of the 110kV voltage transformer Y-phase secondary connection box was burned due to moisture caused by poor sealing, and the secondary winding lead had white mold attached, which caused the secondary voltage angle deviation of the voltage transformer and affected the test value of the bushing under voltage. After the defect in the secondary connection box of the voltage transformer was treated, the power supply was restored to normal. In December 2023, the bushing under voltage test was retested, and the retest data was normal, as shown in Table 5.

[0070] It should be noted that the actual test situation of the method is that the absolute method is used to test more than 110 bushings of 35kV-500kV capacitive bushings in 130 substations, and more than 6500 sets of field test data are analyzed for 7 years. The interference situation is consistent with the above theoretical analysis, and the bus PT angle difference and the phase-to-phase interference are the main interference factors of the absolute method test, but the error value of the selected fixed bus PT is basically stable and unchanged under stable power grid operation mode; the influence of other factors such as environmental temperature and humidity is small. 95% of the dielectric loss test values fluctuate within ±0.1%, and the remaining 5% of the abnormal data can also find the reasons for the abnormality through specific analysis of specific problems, such as changes in electromagnetic interference environment after substation technical improvement, changes in PT secondary load after protection device replacement, and changes in operation mode. Therefore, the failure of the bushing is found in advance at a rate of 100% by using the method, and no missed judgment or misjudgment occurs. The fault bushing found by using the method is found to have different degrees of insulation defects in subsequent disassembly and maintenance, and the bushing with normal insulation state found by using the method is also found to be normal in the pre-test work of power-off maintenance.

[0071] In summary, the present application overcomes the long-standing technical bias of the absolute method in the field. The absolute method bushing under voltage test naturally takes advantage of the characteristics of the running transformer under running voltage and oil temperature periodic changes, avoiding a large number of voltage and temperature test equipment, and can be equivalent to simultaneously carrying out bushing high voltage dielectric loss test and thermal stability test on site, which is simple, easy to operate, highly applicable and has good application effect. Under the dual action of high voltage and high oil temperature, the dielectric loss value of the normal bushing under voltage changes little, while the dielectric loss value of the bushing with insulation defects increases significantly, which is much larger than the test error fluctuation range, and the increment is obvious enough to sensitively reflect the early insulation deterioration of the bushing and truly reflect the running state of the bushing; the present application fills the gap of no clear judgment standard for the absolute method transformer bushing insulation state under voltage detection, promotes the popularization and application of the absolute method transformer bushing insulation state under voltage detection technology, and improves the operation and maintenance level of the transformer bushing.

[0072] Embodiment 5, the above is a schematic scheme of the transformer bushing dielectric loss absolute method on-line test diagnosis method. It should be noted that the technical scheme of the transformer bushing dielectric loss absolute method on-line test diagnosis system belongs to the same concept as the technical scheme of the transformer bushing dielectric loss absolute method on-line test diagnosis method described above. The technical scheme of the transformer bushing dielectric loss absolute method on-line test diagnosis system in this embodiment is not described in detail, and the description of the technical scheme of the transformer bushing dielectric loss absolute method on-line test diagnosis method described above can be referred to.

[0073] The embodiment also provides a transformer bushing dielectric loss absolute method on-line test diagnosis system, comprising: The acquisition module is configured to acquire the dielectric loss value of the bushing in operation through on-line test of the bushing. The calculation module is configured to calculate the dielectric loss value increment of the dielectric loss value and the initial dielectric loss value based on the dielectric loss value of the bushing. The first judgment module is configured to obtain the first judgment conclusion of the insulation state of the bushing based on comparison between the dielectric loss value increment and the dielectric loss detection threshold. The second judgment module is configured to acquire the upper oil temperature of the transformer, analyze the change trend of the dielectric loss value with the upper oil temperature of the transformer, and obtain the second judgment conclusion. The execution module is configured to judge the insulation condition of the bushing and perform corresponding processing based on the first judgment conclusion and the second judgment conclusion.

[0074] The embodiment also provides an electronic device suitable for transformer bushing dielectric loss absolute method on-line test diagnosis, comprising: a memory and a processor; the memory is configured to store computer executable instructions, and the processor is configured to execute the computer executable instructions to implement the transformer bushing dielectric loss absolute method on-line test diagnosis method proposed in the above embodiment.

[0075] The embodiment also provides a storage medium having a computer program stored thereon, which is executed by a processor to implement the transformer bushing dielectric loss absolute method on-line test diagnosis method proposed in the above embodiment.

[0076] The storage medium proposed in the embodiment and the transformer bushing dielectric loss absolute method on-line test diagnosis method proposed in the above embodiment belong to the same inventive concept. The technical details not described in detail in the embodiment can be referred to the above embodiment, and the embodiment has the same beneficial effects as the above embodiment.

[0077] Those skilled in the art can clearly understand the present application by the above description of the embodiments, and the present application can be realized by software and necessary general hardware, and of course, can also be realized by hardware. Based on such understanding, the technical solutions of the present application or the part that contributes to the prior art can be embodied in the form of a software product, which can be stored in a computer readable storage medium, such as a floppy disk, a read-only memory (ROM), a random access memory (RAM), a FLASH, a hard disk, or an optical disc, and includes a number of instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute the methods of various embodiments of the present application.

[0078] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application but not limit the present application, and although the present application is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the spirit and scope of the present application, and all should be covered in the scope of the claims of the present application.

Claims

1. A live-line testing and diagnostic method for transformer bushing dielectric loss using the absolute method, characterized in that, include: The dielectric loss value of the bushing during operation is obtained by conducting a live test on the bushing. Based on the casing dielectric loss value, calculate the dielectric loss increment compared to the initial dielectric loss value; Based on the comparison between the dielectric loss increment and the dielectric loss detection threshold, the first judgment conclusion of the bushing insulation status is obtained; The temperature of the upper oil layer of the transformer is obtained, and the trend of dielectric loss value with the temperature of the upper oil layer of the transformer is analyzed to obtain the second judgment conclusion. Based on the first and second judgment conclusions, the insulation status of the bushing is determined and corresponding processing is performed.

2. The transformer bushing dielectric loss absolute method for live-line testing and diagnosis as described in claim 1, characterized in that, Based on the casing dielectric loss value, calculate the dielectric loss increment compared to the initial dielectric loss value, including: The dielectric loss value of the bushing obtained by the live test is used to calculate the difference between the current dielectric loss value and the initial dielectric loss value as the dielectric loss increment. The initial dielectric loss value is the dielectric loss measurement value of the first live test after the equipment is put into operation.

3. The transformer bushing dielectric loss absolute method for live-line testing and diagnosis as described in claim 2, characterized in that, Based on the comparison between the dielectric loss increment and the dielectric loss detection threshold, the first judgment conclusion on the bushing insulation condition is obtained, including: The threshold for dielectric loss detection includes a first threshold and a second threshold, wherein the second threshold is greater than the first threshold. If the increase in dielectric loss value is not greater than the first threshold, the first judgment conclusion is that the state is normal. If the increase in dielectric loss value is between the two thresholds, the first judgment conclusion is a warning state; If the increment of dielectric loss is not less than the second threshold, the first judgment conclusion is an abnormal state.

4. The transformer bushing dielectric loss absolute method for live-line testing and diagnosis as described in claim 3, characterized in that, The transformer upper oil temperature is obtained, and the trend of dielectric loss value with the transformer upper oil temperature is analyzed to obtain the second judgment conclusion, including: When the bushing insulation condition is in a warning state or an abnormal state, a second judgment is made within the first preset time period and the second preset time period, respectively: Multiple sets of dielectric loss values ​​and transformer upper oil temperature data were obtained by conducting multiple online tests under different oil temperature conditions. Based on the analysis of the changing trends of multiple sets of dielectric loss values ​​and transformer upper oil temperature data, a second judgment conclusion was obtained.

5. The transformer bushing dielectric loss absolute method for live-line testing and diagnosis as described in claim 4, characterized in that, When in a warning state, based on the second judgment conclusion, the bushing insulation condition is assessed and corresponding actions are taken, including: When in a warning state, the second judgment conclusion is that the dielectric loss value increases with the rise of oil temperature, then the bushing has an insulation defect, and it should be handled in conjunction with the power outage maintenance cycle; When in a warning state, the second judgment is that the oil temperature rises while the dielectric loss value remains basically constant, then the bushing insulation is normal.

6. The transformer bushing dielectric loss absolute method for live-line testing and diagnosis as described in claim 5, characterized in that, When an abnormal state is detected, the bushing insulation condition is assessed based on the second judgment conclusion, and corresponding actions are taken, including: When in an abnormal state, the second judgment conclusion is that the dielectric loss value increases with the increase of oil temperature, then the bushing has an insulation defect, and power is cut off for handling. When in an abnormal state, the second judgment is that the oil temperature rises while the dielectric loss value remains basically constant, then the bushing has an insulation abnormality. During operation, continuous monitoring and interference elimination are required.

7. The transformer bushing dielectric loss absolute method for live-line testing and diagnosis as described in claim 6, characterized in that, The dielectric loss value of the bushing is obtained through live bushing testing, including: The current signal of the bushing end screen and the bus voltage signal are obtained by conducting live bushing tests. The bushing dielectric loss value is obtained by performing analog-to-digital conversion on the bushing end screen current signal and the bus voltage signal.

8. A transformer bushing dielectric loss absolute method live-line testing and diagnostic system, using the method described in any one of claims 1-7, characterized in that, include: The acquisition module is used to obtain the dielectric loss value of the bushing during operation through live bushing testing; The calculation module is used to calculate the increment of dielectric loss value compared to the initial dielectric loss value, based on the dielectric loss value of the casing. The first judgment module is used to obtain the first judgment conclusion on the insulation status of the bushing based on the comparison between the dielectric loss value increment and the dielectric loss detection threshold. The second judgment module is used to obtain the transformer upper oil temperature, analyze the changing trend of dielectric loss value with the transformer upper oil temperature, and obtain the second judgment conclusion. The execution module is used to determine the bushing insulation status based on the first and second judgment conclusions and to perform corresponding processing.

9. An electronic device, characterized in that, include: Memory and processor; The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, they implement the steps of the transformer bushing dielectric loss absolute method live-line test and diagnosis method according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, It includes storing computer-executable instructions that, when executed by a processor, implement the steps of the transformer bushing dielectric loss absolute method live-line test and diagnosis method according to any one of claims 1 to 7.

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