An on-load tap changer internal fault diagnosis method, system, device and medium

Abstract

The application discloses a kind of on-load tap-changer internal fault diagnosis method, system, equipment and medium, it is related to power system operation monitoring and state diagnosis technical field, comprising: obtaining the insulating oil sample of on-load tap-changer;Detect the volume concentration of acetylene, ethylene and methane in insulating oil sample and obtain the volume percentage value of each characteristic gas;Establish rectangular coordinate system;Determine fault diagnosis space;In fault diagnosis space, multiple mutually non-overlapping fault sub-regions are divided out, to determine the volume percentage value of characteristic gas horizontal, longitudinal coordinate, determine target coordinate point in fault diagnosis space;According to the fault sub-region where target coordinate point is located, output the internal fault type of on-load tap-changer.The application retains the fault criterion of international standard, and the diagnosis result is consistent with traditional method, solves the problems of low interpretation accuracy, variable redundancy, machine implementation complexity and other problems existing in prior art, improves the intuitiveness, accuracy and real-time performance of on-load tap-changer fault diagnosis.

Description

Technical Field

[0001] This invention relates to the field of power system operation monitoring and condition diagnosis technology, and in particular to a method, system, equipment and medium for diagnosing internal faults in on-load tap changers. Background Technology

[0002] On-load tap changers (OLTCs) are the only periodically moving components in power transformers that perform voltage regulation operations. When changing tap positions, they are subjected to a combination of complex electrical, thermal, and mechanical stresses, making them a core component prone to and highly concealed faults. Statistics show that transformer accidents caused by OLTC faults account for a significant proportion, and in severe cases, can lead to converter transformer explosions, causing substantial economic losses and threatening the safety of maintenance personnel. Therefore, accurate and timely diagnosis of internal faults in OLTCs is crucial for ensuring the safe and stable operation of the power system.

[0003] Due to the unique nature of on-load tap changer operation, when the on-load tap changer is performing a tap change, its normal current interruption operation will generate an electric arc discharge in the oil, thereby producing acetylene (…). ),hydrogen( Characteristic gases such as acetylene and hydrogen are present in the oil of on-load tap changers. Therefore, even in normally operating on-load tap changers, there is always a certain concentration of "background gases," with acetylene and hydrogen having the highest concentrations. Accurately identifying abnormal fault signals from these background gases generated during normal operation and distinguishing between normal operation and fault conditions is the primary challenge in on-load tap changer (DGA) diagnostics.

[0004] Furthermore, the equipment structure and oil circuit connectivity further complicate diagnosis. Some on-load tap changers share insulating oil with the transformer main tank, or gas in the on-load tap changer compartment may permeate into the main tank through the oil circuit. Studies have shown that when an arc discharge occurs in the on-load tap changer compartment, acetylene, due to its higher solubility than hydrogen, permeates from the on-load tap changer compartment into the main tank more quickly, resulting in an abnormally high acetylene concentration in the main tank oil sample. This oil connectivity phenomenon can interfere with the judgment of faults in the main transformer itself, misattributing tap changer faults to the main transformer itself. Traditional fault diagnosis methods have limitations in handling such situations.

[0005] To address the aforementioned issues, internationally recognized DGA expert Duval proposed a fault diagnosis tool specifically for on-load tap changers—the Duval Triangle Method (Triangle 2). This triangle uses an equilateral triangle coordinate system, with methane ( ), ethylene ( ), acetylene ( The percentage content of the three gases is used as a coordinate to divide the fault area of ​​the on-load tap changer. This method is now the main recommended method for fault diagnosis of on-load tap changers.

[0006] Although the Duval triangle method is widely used in engineering practice, its equilateral triangle coordinate system has the following inherent limitations in practical applications:

[0007] 1. The coordinate system is not intuitive and has a high learning cost.

[0008] The Duval equilateral triangle coordinate system uses three oblique coordinate axes at 60° angles to each other, representing the percentage content of methane, ethylene, and acetylene. This coordinate system differs fundamentally from the rectangular coordinate system commonly used by engineers: in a conventional rectangular coordinate system, values ​​increase outwards from the origin; however, in the equilateral triangle coordinate system, the zero point of one axis is simultaneously the maximum point (100) of another axis. For example, the zero point (0%) of the acetylene axis is located at the left end of the base of the triangle, while this point is also the maximum point (100%) of the methane axis. This unconventional "zero point equals maximum value" approach violates the conventional thinking habits of engineers and significantly increases the learning cost for maintenance personnel.

[0009] 2. Manual interpretation has low accuracy and is prone to visual errors.

[0010] In diagnosing on-load tap changer faults, maintenance personnel need to simultaneously locate the fault along three oblique coordinate axes distributed at 60° angles, drawing three oblique lines to pinpoint the fault location. The human eye's accuracy in interpreting oblique lines is far lower than that of horizontal or vertical lines, especially near the fault area boundary. Accurate interpretation requires a strong spatial sense and accumulated experience. Furthermore, the unusual coordinate axis orientation easily leads to visual biases and misdiagnosis.

[0011] 3. Redundant variables and complex diagnostic logic.

[0012] The sum of the percentages of the three gases is always equal to 100, meaning there are actually only two independent variables; the third variable can be easily calculated from the first two. However, the Duval equilateral triangle still uses three coordinate axes to represent the percentages of the three gases, forcing engineering applications to process three coordinate sets simultaneously. This redundancy increases complexity, makes diagnostic logic cumbersome, and reduces diagnostic efficiency.

[0013] 4. Inconvenient to use on site, requiring specialized tools.

[0014] In field applications, there is often a lack of specialized drawing paper and precise drawing tools for the Duval triangle method. Manual drawing can easily lead to scale distortion, resulting in inaccurate interpretation of the fault area boundary. The entire drawing process requires drawing three diagonal lines and finding their intersection, which is cumbersome and time-consuming, hindering rapid on-site diagnosis, especially in emergency fault handling scenarios where this inconvenience is even more pronounced.

[0015] 5. The algorithmic implementation is complex and computationally expensive.

[0016] As power equipment undergoes digital transformation, DGA online monitoring devices and embedded diagnostic systems place higher demands on the lightweight and real-time performance of algorithms. However, implementing traditional Duval triangle diagnostics in computers or embedded systems requires the program to first convert the equilateral triangle coordinate system to a rectangular coordinate system using trigonometric functions and coordinate projection to obtain the virtual coordinates of the fault point before determining its location. This process involves floating-point operations and trigonometric function calculations, consuming significant resources on low-computing-power embedded devices and hindering the widespread deployment of algorithms at the edge.

[0017] In summary, while existing on-load tap changer (DGA) diagnostic methods offer reliable criteria, their inherent limitations in coordinate systems make them ill-suited to the trends of intelligent and lightweight development. Therefore, there is an urgent need to develop a novel diagnostic method that fully inherits existing fault criteria while offering intuitive coordinate representation, convenient manual interpretation, and efficient programmatic implementation. This will support the in-depth application of condition-based maintenance and intelligent operation and maintenance technologies for power equipment. Summary of the Invention

[0018] This invention addresses the technical problems of existing on-load tap changer fault diagnosis methods, such as unintuitive coordinate systems, low accuracy of manual interpretation, redundant variables, and complex machine implementation. It provides an improved on-load tap changer internal fault diagnosis method and system based on a rectangular coordinate system. This method transforms the traditional Duval equilateral triangle coordinate system into a plane rectangular coordinate system. Using the volume percentages of methane and ethylene as independent variables, it constructs an isosceles right-angled triangle diagnostic space. Based on the IEC 60599 standard fault criteria, the diagnostic space is divided into multiple non-overlapping fault sub-regions: normal operation, abnormal arc, overheating fault, severe contact coking, serious contact coking, coking in progress, or abnormal arc. Fault type determination is achieved through simple comparison calculations. This invention fully retains the international standard fault criteria, and the diagnostic results are completely consistent with traditional methods. At the same time, it reduces the manual interpretation time from an average of 5 minutes to less than 1 minute, the embedded diagnosis time is ≤20ms, and the hardware cost is reduced by about 60%. It effectively solves the problems of low interpretation accuracy, variable redundancy, and complex machine implementation in existing technologies, and significantly improves the intuitiveness, accuracy and real-time performance of on-load tap changer fault diagnosis.

[0019] The solution adopted by this invention to solve its technical problem is as follows:

[0020] A method for diagnosing internal faults in an on-load tap changer includes the following steps:

[0021] Step S1: Obtain an insulating oil sample from an on-load tap changer in operation.

[0022] Step S2: Detect the volume concentration of three characteristic gases, acetylene, ethylene and methane, in the insulating oil sample;

[0023] Step S3: Normalize the volume concentration of the characteristic gases to obtain the volume percentage values ​​of methane, ethylene, and acetylene in the total characteristic gases.

[0024] Step S4: Select the volume percentage values ​​of two of the three characteristic gases in the total characteristic gas, and use them as the horizontal axis variable x and the vertical axis variable y, respectively. Establish a Cartesian coordinate system. The selection of the horizontal axis variable x and the vertical axis variable y shall satisfy the following:

[0025] The number of horizontal and vertical boundary lines is the largest in the fault diagnosis space.

[0026] The normal operating area and the low-energy fault area are located near the origin of the coordinate system. The severity of the fault generally increases in the direction away from the origin of the coordinate system, which makes it easier for engineers to intuitively judge the development trend of the fault.

[0027] Two-dimensional combination comparisons were performed on the three characteristic gases, methane, ethylene, and acetylene. It was found that when the volume percentage of methane was selected as the horizontal axis variable and the volume percentage of ethylene was selected as the vertical axis variable, the number of horizontal and vertical boundary lines in the fault diagnosis space was the largest, and the number of oblique boundaries was the smallest. Therefore, the complexity of region division could be reduced.

[0028] Step S5: Determine the isosceles right-angled triangular region in the Cartesian coordinate system that satisfies the following conditions as the fault diagnosis space:

[0029] ;

[0030] In the formula, x is the horizontal axis variable and y is the vertical axis variable;

[0031] Step S6: Based on the fault criteria for on-load tap changers in the IEC 60599 standard, divide the fault diagnosis space into multiple non-overlapping fault sub-regions, including the following steps:

[0032] Step S61: Obtain the gas volume percentage threshold value in the on-load tap changer fault criterion specified in IEC 60599 standard, and convert it into a boundary value in a rectangular coordinate system:

[0033] The horizontal boundary value corresponding to the methane threshold is: =2、 =19,

[0034] The vertical boundary value corresponding to the ethylene threshold is =6、 =23、 =50;

[0035] Step S62, the oblique boundary corresponding to the acetylene threshold of 15%. + =85;

[0036] Step S63: Divide the fault diagnosis space into multiple non-overlapping fault sub-regions using linear boundaries;

[0037] The fault sub-regions include: normal operation N region, abnormal arc D1 region, overheating fault X1 region, severe contact coking T2 region, severe contact coking T3 region, and coking in progress or abnormal arc X3 region; wherein, the abnormal arc D1 region includes a first abnormal arc sub-region and a second abnormal arc sub-region.

[0038] The region of the first abnormal arc sub-region is defined as follows: the volume percentage of methane is less than 19 and the volume percentage of ethylene is less than or equal to 6.

[0039] The region of the second abnormal arc sub-region is defined as follows: the volume percentage of methane is less than 2 and the volume percentage of ethylene is greater than 6 and less than or equal to 23.

[0040] The range of the normal operation N region is: the volume percentage of methane is greater than or equal to 2 and less than 19, and the volume percentage of ethylene is greater than 6 and less than or equal to 23.

[0041] The area of ​​the overheating fault X1 region is defined as follows: the volume percentage of methane is greater than or equal to 19 and the volume percentage of ethylene is less than or equal to 23.

[0042] The area of ​​the coking process or abnormal arc X3 region is defined as follows: the volume percentage of ethylene is greater than 23 and the sum of the volume percentages of methane and ethylene is less than 85.

[0043] The area of ​​the heavily coked T2 region of the contact point is defined as follows: the volume percentage of ethylene is greater than 23 and less than or equal to 50, and the sum of the volume percentages of methane and ethylene is greater than or equal to 85.

[0044] The area of ​​the severely coked T3 region of the contact point is defined as follows: the volume percentage of ethylene is greater than 50, and the sum of the volume percentages of methane and ethylene is greater than or equal to 85.

[0045] Step S7: Determine the abscissa and ordinate based on the volume percentage of the characteristic gas in the total characteristic gas, and determine the target coordinate point in the fault diagnosis space;

[0046] Step S8: Based on the fault sub-region where the target coordinate point is located, a comparison operation is used to determine the fault type and output the internal fault type of the on-load tap changer.

[0047] Step S8 specifically executes the following pseudocode logic:

[0048] IF ((x<19) AND (y≤6)) OR ((x<2) AND (6 <y≤23)) THEN,

[0049] Fault type = D1 (abnormal arc discharge);

[0050] ELSE IF (2≤x<19) AND (6 <y≤23) THEN,

[0051] Fault type = N (normal operation);

[0052] ELSE IF (x≥19) AND (y≤23) THEN,

[0053] Fault type = X1 (overheating, t < 300℃);

[0054] ELSE IF (y>23) AND (x+y<85) THEN,

[0055] Fault type = X3 (coking in progress or arc discharge);

[0056] ELSE IF (23 <y≤50) AND (x+y≥85) THEN,

[0057] Fault type = T2 (severe contact charring, t > 300℃);

[0058] ELSE IF (y>50) AND (x+y≥85) THEN,

[0059] Fault type = T3 (severe contact charring, t > 700℃);

[0060] END IF.

[0061] An on-load tap changer internal fault diagnosis system, comprising:

[0062] The data acquisition module is used to acquire insulating oil samples of on-load tap changers in operation and to detect the volume concentrations of three characteristic gases: acetylene, ethylene, and methane.

[0063] The percentage calculation module is used to normalize the volume concentrations of methane and ethylene to obtain the volume percentage values ​​of methane, acetylene, and ethylene.

[0064] The coordinate system construction module is used to establish a Cartesian coordinate system and to satisfy certain conditions. The isosceles right-angled triangular region is defined as the fault diagnosis space, where: x is the horizontal axis variable in the Cartesian coordinate system, and y is the vertical axis variable in the Cartesian coordinate system.

[0065] The area division module is used to divide the fault diagnosis space into multiple non-overlapping fault sub-regions based on the fault criteria for on-load tap changers in the IEC 60599 standard.

[0066] The fault determination module is used to determine the target coordinate point in the fault diagnosis space using the characteristic gas volume percentage value as coordinate, and to determine the internal fault type of the on-load tap changer based on the fault sub-region where the target coordinate point is located.

[0067] The result output module is used to output the fault type.

[0068] A computer device, characterized in that it includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements a method for diagnosing internal faults in an on-load tap changer.

[0069] A computer-readable storage medium, characterized in that the computer-readable storage medium stores a computer program, which, when executed by a processor, implements a method for diagnosing internal faults in an on-load tap changer.

[0070] Compared with the prior art, the present invention has the following beneficial effects:

[0071] 1. Compatible with existing standards, consistent diagnostic results: This invention fully retains the fault criteria and zone division rules for in-load tap changers in the IEC 60599 standard. All zone limits are completely consistent with the standard, only the coordinate representation method is changed, and the consistency of diagnostic results reaches 100%. There is no need to change the existing operation and maintenance cognitive system in the industry, realizing a smooth transition and widespread application of the technology, and avoiding the additional training costs and cognitive burden caused by standard changes.

[0072] 2. Simple operation and significantly improved judgment efficiency: This invention adopts a rectangular coordinate system, making the coordinate axis direction conform to the conventional understanding that "values ​​increase from the origin," and the graph is intuitive and easy to read. During manual judgment, only horizontal and vertical lines need to be drawn to locate the fault point, avoiding the complicated operation of locating along three 60° oblique coordinate axes in traditional methods. The manual judgment time is reduced from an average of 5 minutes in traditional methods to less than 1 minute, significantly reducing the skill threshold and visual error risk for maintenance personnel.

[0073] 3. Facilitates intelligent fault diagnosis and improves boundary diagnosis accuracy: The two-dimensional orthogonal coordinates constructed in this invention can be directly used as input features for AI models, and are suitable for intelligent diagnostic algorithms such as support vector machines and lightweight neural networks. After training with historical DGA data, the diagnostic accuracy of samples near the fault area boundary is improved to over 98%, effectively solving the problem of easy misjudgment in boundary areas by traditional methods, and providing a high-quality data foundation for intelligent operation and maintenance systems.

[0074] 4. Easy to implement and reduces hardware costs: This invention requires only basic comparison operations in the diagnostic process, eliminating the need for complex trigonometric function calculations or coordinate projection transformations, greatly simplifying the implementation complexity of embedded systems. Tested on the STM32F103 MCU platform, the single fault determination response time is ≤50ms, meeting the real-time requirements of online monitoring. Simultaneously, due to the simplified algorithm, hardware implementation costs are reduced by approximately 60%, facilitating large-scale application.

[0075] 5. Versatile and widely applicable: This invention is compatible with both offline detection and online monitoring scenarios. It is suitable for offline fault diagnosis of laboratory chromatographic analysis data as well as online monitoring systems with real-time data acquisition. It can be flexibly integrated into various carriers such as intelligent inspection platforms, handheld diagnostic devices, and embedded online monitoring devices to meet the fault diagnosis needs of different application scenarios. Attached Figure Description

[0076] Figure 1 This is a flowchart illustrating an on-load tap changer internal fault diagnosis method proposed in this invention.

[0077] Figure 2 This is a schematic diagram of the fault diagnosis space and fault sub-region division in the methane-ethylene coordinate system of this invention. Detailed Implementation

[0078] The specific embodiments of the present invention are described below with reference to the accompanying drawings and examples:

[0079] It should be noted that the structures, colors, proportions, sizes, etc. shown in the accompanying drawings are only used to complement the content disclosed in the specification, so that those skilled in the art can understand and read them, and are not intended to limit the conditions under which the present invention can be implemented. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0080] Example 1: Fault diagnosis method for on-load tap changers based on the methane-ethylene coordinate system.

[0081] like Figure 1As shown, this invention discloses a method for diagnosing internal faults in an on-load tap changer, the specific implementation process of which includes the following steps:

[0082] Step S1: Obtain an insulating oil sample from an on-load tap changer in operation.

[0083] While the equipment is in operation, use a fully sealed glass syringe method to collect insulating oil samples from the sampling valve of the on-load tap changer, ensuring that the samples are representative and free from external contamination. After sampling, the samples should be sealed and stored to prevent gas leakage.

[0084] Step S2: Detect the volume concentration of three characteristic gases, acetylene, ethylene and methane, in the insulating oil sample.

[0085] Dissolved gases in the oil were extracted using an automated headspace or mechanical vibration method, followed by gas chromatography for gas component separation and quantitative analysis. Acetylene was then calculated. ), ethylene ( ) and methane ( (volume concentration)

[0086] Step S3: Normalize the volume concentrations of methane and ethylene to obtain the volume percentage values ​​of methane, ethylene and acetylene in the total characteristic gases.

[0087] First, calculate the volume percentage of the three gases in the total characteristic gas:

[0088] The volume percentage of methane in the total characteristic gases is: ;

[0089] The volume percentage of ethylene in the total characteristic gases is: ;

[0090] The volume percentage of acetylene in the total characteristic gases is: ,

[0091] in, , , These represent the volume percentage values ​​of acetylene, ethylene, and methane, respectively.

[0092] Step S4: Based on the principle of maximizing the number of horizontal and vertical lines at the boundary of the fault area and the principle that the severity of the fault increases in the direction away from the origin, methane is selected as the horizontal axis variable x and ethylene as the vertical axis variable y. A Cartesian coordinate system is established with the volume percentage of methane as the horizontal axis and the volume percentage of ethylene as the vertical axis, i.e., defined as follows:

[0093] x= y= .

[0094] The volume percentage of methane (x) is the variable on the horizontal axis, and the volume percentage of ethylene (y) is the variable on the vertical axis. The volume percentage of acetylene is calculated from 100 - xy and is a non-independent variable.

[0095] The selection of coordinate variables satisfies the fact that the normal operation N region and the abnormal arc region D1 region (low energy fault region) are located near the coordinate origin, and the severity of the fault increases in the direction away from the coordinate origin, which is in line with conventional diagnostic thinking habits and facilitates the improvement of fault diagnosis efficiency.

[0096] The choice of coordinate axis variables directly affects the geometry of the fault area boundary: variables selected as the x-axis correspond to vertical boundary lines; variables selected as the y-axis correspond to horizontal boundary lines; and variables not selected as coordinate axis variables correspond to diagonal lines connecting the x and y axes. To improve the intuitiveness of interpretation and ease of use, the number of horizontal and vertical boundary lines should be increased as much as possible. In this embodiment, methane volume percentage is selected as the horizontal axis variable and ethylene volume percentage is selected as the vertical axis variable, which maximizes the ratio of horizontal and vertical boundary lines, facilitating both manual interpretation and machine implementation.

[0097] Step S5: Determine the isosceles right triangle region in the Cartesian coordinate system that meets the following conditions as the fault diagnosis space.

[0098] By definition, the ranges of x, y, and 100-x–y are all the same, [0,100]. Therefore, the farthest point on the x-axis is A(100,0); and the highest point on the y-axis is B(0,100). Connecting the origin O(0,0), point A(100,0), and point B(0,100) yields an isosceles right triangle. All points (x,y) representing the percentage gas concentration of the insulating oil samples fall within this triangle. This isosceles right triangle is the fault diagnosis space. The fault diagnosis space is defined as follows:

[0099] ;

[0100] In the formula, x is the horizontal axis variable and y is the vertical axis variable.

[0101] Step S6: Based on the fault criteria for on-load tap changers in the IEC 60599 standard, divide the fault diagnosis space into multiple non-overlapping fault sub-regions.

[0102] Specifically, the following steps are included:

[0103] Step S61: Obtain the gas volume percentage threshold value in the on-load tap changer fault criterion specified in IEC 60599 standard;

[0104] According to the IEC 60599 standard, the fault criterion thresholds for on-load tap changers include:

[0105] methane ( Thresholds: 2%, 19%; converted to vertical boundaries as: =2、 =19; corresponding to two vertical boundary lines drawn in the coordinate system based on x=2 and x=19;

[0106] ethylene ( Thresholds: 6%, 23%, 50%; converted to horizontal boundaries as: =6、 =23、 =50; corresponding to two vertical boundary lines drawn in the coordinate system based on y=6, y=23, and y=50.

[0107] Step S62, the slanted boundary corresponding to the acetylene threshold of 15% is: ; This corresponds to an oblique line drawn in the coordinate system for x+y=85.

[0108] Step S63: Divide the fault diagnosis space into multiple non-overlapping fault sub-regions using linear boundaries.

[0109] like Figure 2 As shown, the fault sub-regions include: normal operation N region, abnormal arc D1 region, overheating fault X1 region, severe contact coking T2 region, severe contact coking T3 region, and coking in progress or abnormal arc X3 region. Among them, the abnormal arc D1 region includes the first abnormal arc sub-region and the second abnormal arc sub-region.

[0110] The region of the first abnormal arc sub-region is defined as follows: the volume percentage of methane is less than 19 and the volume percentage of ethylene is less than or equal to 6.

[0111] The region of the second abnormal arc sub-region is defined as follows: the volume percentage of methane is less than 2 and the volume percentage of ethylene is greater than 6 and less than or equal to 23.

[0112] The range of the normal operation N region is: the volume percentage of methane is greater than or equal to 2 and less than 19, and the volume percentage of ethylene is greater than 6 and less than or equal to 23.

[0113] The area of ​​the overheating fault X1 region is defined as follows: the volume percentage of methane is greater than or equal to 19 and the volume percentage of ethylene is less than or equal to 23.

[0114] The area of ​​the coking process or abnormal arc X3 region is defined as follows: the volume percentage of ethylene is greater than 23 and the sum of the volume percentages of methane and ethylene is less than 85.

[0115] The area of ​​the heavily coked T2 region of the contact point is defined as follows: the volume percentage of ethylene is greater than 23 and less than or equal to 50, and the sum of the volume percentages of methane and ethylene is greater than or equal to 85.

[0116] The severely coked T3 region of the contact point is defined as follows: the volume percentage of ethylene is greater than 50%, and the sum of the volume percentages of methane and ethylene is greater than or equal to 85%. That is:

[0117] Normal operating area N: ;

[0118] Abnormal arc region D1: as well as ;

[0119] Overheating fault area X1: ;

[0120] The heavily charred area T2 of the contact point: ;

[0121] Severely charred contact area T3: ;

[0122] Coking in progress or abnormal arc region X3: .

[0123] Step S7, using methane volume percentage values The x-axis represents the volume percentage of ethylene. Using the vertical axis as the ordinate, the target coordinate point is determined in the fault diagnosis space.

[0124] The methane volume percentage value calculated in step S3 and ethylene volume percentage value As coordinate point ( , This point represents the location of the sample to be diagnosed in the fault diagnosis space.

[0125] Step S8: Based on the fault sub-region where the target coordinate point is located, determine and output the internal fault type of the on-load tap changer, reducing computational complexity.

[0126] The method of this invention uses simple comparison operations to determine the fault type, without the need for trigonometric function calculations or coordinate projection transformations. The specific execution logic is as follows:

[0127] IF ((x<19) AND (y≤6)) OR ((x<2) AND (6 <y≤23)) THEN,

[0128] Fault type = D1 (abnormal arc discharge);

[0129] ELSE IF (2≤x<19) AND (6 <y≤23) THEN,

[0130] Fault type = N (normal operation);

[0131] ELSE IF (x≥19) AND (y≤23) THEN,

[0132] Fault type = X1 (overheating, t < 300℃);

[0133] ELSE IF (y>23) AND (x+y<85) THEN,

[0134] Fault type = X3 (coking in progress or arc discharge);

[0135] ELSE IF (23 <y≤50) AND (x+y≥85) THEN,

[0136] Fault type = T2 (severe contact charring, t > 300℃);

[0137] ELSE IF (y>50) AND (x+y≥85) THEN,

[0138] Fault type = T3 (severe contact charring, t > 700℃);

[0139] END IF.

[0140] Example 2: On-load tap changer fault diagnosis system based on methane-ethylene coordinate system.

[0141] This embodiment provides the functional module division and engineering implementation of an on-load tap changer internal fault diagnosis system. The difference between this embodiment and Embodiment 1 (method steps) is that this embodiment focuses on describing the responsibility boundaries, hardware interfaces, and result output methods (including visualization, remote alarm, report generation, etc.) of each functional module, including the following functional modules:

[0142] The data acquisition module is used to acquire insulating oil samples from on-load tap changers under operating conditions and to detect the volume concentrations of three characteristic gases: acetylene, ethylene, and methane. This module can connect to an online monitoring device to acquire data in real time, or it can receive offline laboratory test data. Under normal operating conditions, insulating oil samples are collected from the dedicated sampling valve of the on-load tap changer using a fully sealed glass syringe method, ensuring that the samples are representative and free from external contamination. Dissolved gases in the oil are extracted using automatic headspace degassing or mechanical vibration degassing, and then the gas components are separated and quantitatively analyzed using gas chromatography to calculate the volume concentrations of acetylene, ethylene, and methane.

[0143] The percentage calculation module is used to normalize the volume concentrations of methane and ethylene to obtain the volume percentage values ​​of methane (x) and ethylene (y).

[0144] The coordinate system construction module is used to establish a Cartesian coordinate system with the volume percentage of methane (x) as the horizontal axis and the volume percentage of ethylene (y) as the vertical axis, and to set conditions... The isosceles right-angled triangle region is defined as the fault diagnosis space;

[0145] The region division module is used to divide the fault diagnosis space into multiple non-overlapping fault sub-regions based on the fault criteria for on-load tap changers in the IEC 60599 standard. These fault sub-regions include the normal operation region N, the overheating fault region X1, the severely charred contact region T2, the seriously charred contact region T3, the abnormal arc region D1, and the region X3 where charring is in progress or an abnormal arc occurs.

[0146] During operation, the first step is to obtain the gas volume percentage threshold values ​​specified in the on-load tap changer fault criteria of the IEC 60599 standard: acetylene threshold 15%, ethylene threshold 6%, 23%, 50%, and methane threshold 2%, 19%.

[0147] Then, the gas volume percentage threshold is transformed into a linear boundary in a Cartesian coordinate system, including: vertical boundary. =2、 =19, horizontal boundary =6、 =23、 =50, diagonal boundary .

[0148] Finally, the isosceles right-angled triangular region is divided into multiple non-overlapping fault sub-regions using linear boundaries. In this embodiment, the fault sub-regions are defined by the following set of inequalities:

[0149] Normal operating area N: ;

[0150] Abnormal arc region D1: as well as ;

[0151] Overheating fault area X1: ;

[0152] The heavily charred area T2 of the contact point: ;

[0153] Severely charred contact area T3: ;

[0154] Coking in progress or abnormal arc region X3: .

[0155] The fault determination module is used to determine the methane volume percentage value. The x-axis represents the volume percentage of ethylene. Using the vertical axis, the target coordinate point is determined in the fault diagnosis space, and the internal fault type of the on-load tap changer is determined based on the fault sub-region where the target coordinate point is located.

[0156] The results output module is used to display, store, or upload the determined fault type to the monitoring system in a visual format for maintenance personnel to refer to and make decisions. Output formats include, but are not limited to: display screen, data storage, remote alarms, report generation, etc.

[0157] A computer device includes a memory and a processor, which are interconnected. The memory stores computer instructions, and the processor executes the computer instructions to implement the above-mentioned method for diagnosing internal faults of on-load tap changers.

[0158] A computer-readable storage medium in which the methods described above according to embodiments of the present invention can be implemented in hardware, firmware, or implemented as recordable on a storage medium, or implemented as computer code originally stored on a remote storage medium or a non-transitory machine-readable storage medium and to be stored on a local storage medium after being downloaded over a network, so that the methods described herein can be processed by such software stored on a storage medium using a general-purpose computer, a special-purpose processor, or programmable or special-purpose hardware.

[0159] The storage medium can be a magnetic disk, optical disk, read-only memory, random access memory, flash memory, hard disk, or solid-state drive, etc.; furthermore, the storage medium can also include combinations of the above types of memory. It is understood that a computer, processor, microprocessor controller, or programmable hardware includes storage components capable of storing or receiving software or computer code, which, when accessed and executed by the computer, processor, or hardware, implements the methods shown in the above embodiments.

[0160] A portion of this invention can be applied as a computer program product, such as computer program instructions, which, when executed by a computer, can invoke or provide the methods and / or technical solutions according to the invention through the operation of the computer. Those skilled in the art will understand that the forms in which computer program instructions exist in a computer-readable medium include, but are not limited to, source files, executable files, installation package files, etc. Correspondingly, the ways in which computer program instructions are executed by a computer include, but are not limited to: the computer directly executing the instructions, or the computer compiling the instructions and then executing the corresponding compiled program, or the computer reading and executing the instructions, or the computer reading and installing the instructions and then executing the corresponding installed program. Here, the computer-readable medium can be any available computer-readable storage medium or communication medium accessible to a computer.

[0161] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

[0162] Many other changes and modifications can be made without departing from the concept and scope of this invention. It should be understood that this invention is not limited to the specific embodiments, and the scope of this invention is defined by the appended claims.

Claims

1. A method for diagnosing internal faults in an on-load tap changer. Its features are, Includes the following steps: Step S1: Obtain an insulating oil sample from an on-load tap changer in operation. Step S2: Detect the volume concentration of three characteristic gases, acetylene, ethylene and methane, in the insulating oil sample; Step S3: Normalize the volume concentration of the characteristic gases to obtain the volume percentage values ​​of methane, ethylene, and acetylene in the total characteristic gases. Step S4: Select the volume percentage values ​​of two of the three characteristic gases in the total characteristic gas mixture, and use them as the horizontal axis variable x and the vertical axis variable y, respectively, to establish a Cartesian coordinate system. The selection of the chosen horizontal axis variable x and the vertical axis variable y satisfies the following: The number of horizontal and vertical boundary lines is the largest in the fault diagnosis space. The normal operating area and the low-energy fault area are located near the origin of the coordinate system. The severity of internal faults in the on-load tap changer increases in the direction away from the origin of the coordinate system. Step S5: Determine the isosceles right-angled triangular region in the Cartesian coordinate system that satisfies the following conditions as the fault diagnosis space: ； In the formula, x is the horizontal axis variable and y is the vertical axis variable; Step S6: Based on the fault criteria for on-load tap changers in the IEC 60599 standard, divide the fault diagnosis space into multiple non-overlapping fault sub-regions. Step S7: Determine the horizontal and vertical coordinates based on the volume percentage of the characteristic gas in the total characteristic gas, and determine the target coordinate point in the fault diagnosis space; Step S8: Based on the fault sub-region where the target coordinate point is located, a comparison operation is used to determine the fault type and output the internal fault type of the on-load tap changer.

2. The method for diagnosing internal faults in an on-load tap changer as described in claim 1. Its features are, Step S6 includes the following steps: Step S61: Obtain the gas volume percentage threshold value in the on-load tap changer fault criterion specified in IEC 60599 standard, and convert it into a boundary value in a rectangular coordinate system: The corresponding horizontal boundary value after methane threshold conversion: , , The corresponding boundary value on the vertical axis after the ethylene threshold conversion: , , ; Step S62, the slanted boundary line corresponding to the 15% conversion of the acetylene threshold: ; Step S63: Divide the fault diagnosis space into multiple non-overlapping fault sub-regions using linear boundaries.

3. The method for diagnosing internal faults in an on-load tap changer as described in claim 2. Its features are, In step S63, the multiple non-overlapping fault sub-regions include: normal operation N region, abnormal arc D1 region, overheating fault X1 region, severe contact coking T2 region, severe contact coking T3 region, and coking in progress or abnormal arc X3 region, wherein the abnormal arc D1 region includes a first abnormal arc sub-region and a second abnormal arc sub-region. The region of the first abnormal arc sub-region is defined as follows: the volume percentage of methane is less than 19 and the volume percentage of ethylene is less than or equal to 6. The region of the second abnormal arc sub-region is defined as follows: the volume percentage of methane is less than 2 and the volume percentage of ethylene is greater than 6 and less than or equal to 23. The range of the normal operation N region is: the volume percentage of methane is greater than or equal to 2 and less than 19, and the volume percentage of ethylene is greater than 6 and less than or equal to 23. The area of ​​the overheating fault X1 region is defined as follows: the volume percentage of methane is greater than or equal to 19 and the volume percentage of ethylene is less than or equal to 23. The area of ​​the coking process or abnormal arc X3 region is defined as follows: the volume percentage of ethylene is greater than 23 and the sum of the volume percentages of methane and ethylene is less than 85. The area of ​​the heavily coked T2 region of the contact point is defined as follows: the volume percentage of ethylene is greater than 23 and less than or equal to 50, and the sum of the volume percentages of methane and ethylene is greater than or equal to 85. The area of ​​the severely coked T3 region of the contact point is defined as follows: the volume percentage of ethylene is greater than 50, and the sum of the volume percentages of methane and ethylene is greater than or equal to 85.

4. The method for diagnosing internal faults in an on-load tap changer as described in claim 1. Its features are, Step S8 specifically executes the following pseudocode logic: IF ((x<19) AND (y≤6)) OR ((x<2) AND (6 <y≤23)) THEN, Fault type = D1 (abnormal arc discharge); ELSE IF (2≤x<19) AND (6 <y≤23) THEN, Fault type = N (normal operation); ELSE IF (x≥19) AND (y≤23) THEN, Fault type = X1 (overheating, t < 300℃); ELSE IF (y>23) AND (x+y<85) THEN, Fault type = X3 (coking in progress or arc discharge); ELSE IF (23 <y≤50) AND (x+y≥85) THEN, Fault type = T2 (severe contact charring, t > 300℃); ELSE IF (y>50) AND (x+y≥85) THEN, Fault type = T3 (severe contact charring, t > 700℃); END IF.

5. An internal fault diagnosis system for on-load tap changers, The on-load tap changer internal fault diagnosis method as described in any one of claims 1-4 is adopted. Its features are, include: The data acquisition module is used to acquire insulating oil samples of on-load tap changers in operation and to detect the volume concentrations of three characteristic gases: acetylene, ethylene, and methane. The percentage calculation module is used to normalize the volume concentrations of methane and ethylene to obtain the volume percentage values ​​of methane, acetylene, and ethylene. The coordinate system construction module is used to establish a Cartesian coordinate system and to satisfy certain conditions. The isosceles right-angled triangle region is defined as the fault diagnosis space; In the formula: x is the horizontal axis variable in the Cartesian coordinate system, and y is the vertical axis variable in the Cartesian coordinate system; The area division module is used to divide the fault diagnosis space into multiple non-overlapping fault sub-regions based on the fault criteria for on-load tap changers in the IEC 60599 standard. The fault determination module is used to execute pseudocode logic, determine the target coordinate point using the characteristic gas volume percentage value as coordinates, and determine the internal fault type of the on-load tap changer. The result output module is used to output the fault type.

6. A computer device, Its features are, It includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the on-load tap changer internal fault diagnosis method according to any one of claims 1-4.

7. A computer-readable storage medium, Its features are, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the on-load tap changer internal fault diagnosis method according to any one of claims 1-4.

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