Transformer partial discharge source location method and system based on simulated time delay database

Abstract

The present invention proposes a transformer local discharge source positioning method and system based on a simulated time delay database, which relates to the technical field of power equipment status monitoring and fault positioning. It includes dividing a transformer three-dimensional simulation model into grids, simulating the installation heat map of ultra-high frequency sensors when the local discharge source is at the center of each grid, and determining the best installation position; calculating the theoretical arrival time difference between ultra-high frequency sensors when the local discharge source is at the center of each grid; establishing a mapping relationship between the local discharge source coordinates of the transformer three-dimensional simulation model and the theoretical arrival time difference between ultra-high frequency sensors, and constructing a simulated time delay database; installing a built-in ultra-high frequency sensor on the actual transformer, and calculating the actual arrival time difference between the ultra-high frequency sensors; searching for a set of theoretical arrival time differences closest to the actual arrival time difference result in the simulated time delay database, and determining the local discharge source positioning result of the actual transformer based on the mapping relationship. The present invention solves the problem of low accuracy of existing local discharge positioning.

Description

Technical Field

[0001] The invention belongs to the technical field of power equipment status monitoring and fault location, and in particular relates to a transformer partial discharge source location method and system based on a simulated time delay database. Background Art

[0002] As one of the most critical equipment in the power system, the insulation reliability of large oil-immersed power transformers is related to the safety and stability of the entire power system. During long-term operation, power transformers often suffer insulation damage due to partial discharge (PD). If not discovered and repaired in time, it will gradually develop into a serious sudden insulation breakdown failure, causing equipment damage, power grid shutdown and other major economic losses.

[0003] The ultra high frequency (UHF) method has the advantages of high sensitivity, strong anti-interference ability and non-contact measurement, and has been widely used in partial discharge detection in recent years. The time difference of arrival (TDOA) method is mainly used to locate the local discharge source with the help of UHF signals. Although this method has simple principles and mature technology, the traditional TDOA mathematical model will have shortcomings such as local optimal solutions and low calculation efficiency in iterative optimization. In addition, due to the complex internal structure of the transformer, the UHF signal does not propagate in a straight line, and there is a non-line-of-sight propagation phenomenon, which leads to large errors in the traditional TDOA mathematical model in actual transformer PD positioning.

[0004] In addition, the installation position of the UHF sensor also has a great impact on the detection and positioning of partial discharge signals. Although the built-in UHF sensor can effectively improve the detection sensitivity and reduce the impact of external electromagnetic interference, the core, winding and other structures inside the power transformer will still affect the ability of the UHF sensor to receive partial discharge signals. At present, the power industry has not yet determined the installation standards for built-in UHF sensors in large oil-immersed power transformers. Summary of the invention

[0005] In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides a transformer partial discharge source locating method and system based on a simulated time delay database, proposes an effective selection method for the installation position of a built-in ultra-high frequency sensor, can further improve the sensitivity of the built-in ultra-high frequency sensor in detecting partial discharge, and uses software simulation to establish a time delay database to solve the problem of low existing partial discharge locating accuracy.

[0006] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions:

[0007] A first aspect of the present invention provides a transformer partial discharge source location method based on a simulation time delay database.

[0008] The transformer partial discharge source location method based on the simulated time delay database includes the following steps:

[0009] Establish a three-dimensional simulation model of the transformer;

[0010] The three-dimensional simulation model of the transformer is divided into grids, and the heat values ​​of the partial discharge UHF signals received by different areas on each box wall of the three-dimensional simulation model of the transformer are simulated when the local discharge source is at the center of each grid, so as to obtain the UHF sensor installation heat map and determine the optimal installation position of the UHF sensor;

[0011] Based on the determined optimal installation position, the theoretical arrival time difference between UHF sensors is simulated and calculated when the local discharge source is at the center of each grid;

[0012] Establish the mapping relationship between the local discharge source coordinates of the transformer 3D simulation model and the theoretical arrival time difference between the UHF sensors, and build the transformer simulation delay database;

[0013] Install the built-in UHF sensor at the corresponding position on the actual transformer, detect the partial discharge UHF signal, and calculate the actual arrival time difference between the UHF sensors;

[0014] A set of theoretical arrival time differences closest to the actual arrival time difference results is searched in the transformer simulation time delay database, and the local discharge source coordinates of the transformer three-dimensional simulation model are determined based on the mapping relationship, thereby determining the local discharge source positioning result of the actual transformer.

[0015] A second aspect of the present invention provides a transformer partial discharge source locating system based on a simulation time delay database.

[0016] The transformer partial discharge source location system based on the simulation time delay database includes:

[0017] The simulation model building module is configured to: build a three-dimensional simulation model of the transformer;

[0018] The optimal installation position determination module is configured to: divide the transformer three-dimensional simulation model into grids, simulate the heat values ​​of the partial discharge ultra-high frequency signals received by different areas on each box wall of the transformer three-dimensional simulation model when the partial discharge source is at the center of each grid, obtain the ultra-high frequency sensor installation heat map, and determine the optimal installation position of the ultra-high frequency sensor;

[0019] The theoretical arrival time difference calculation module is configured to: based on the determined optimal installation position, simulate and calculate the theoretical arrival time difference between the UHF sensors when the local discharge source is at the center of each grid;

[0020] The simulation time delay database construction module is configured to: establish a mapping relationship between the local discharge source coordinates of the three-dimensional simulation model of the transformer and the theoretical arrival time difference between the UHF sensor, and construct a simulation time delay database of the transformer;

[0021] The actual arrival time difference calculation module is configured to: install a built-in UHF sensor at a corresponding position on the actual transformer, detect the partial discharge UHF signal, and calculate the actual arrival time difference between the UHF sensors;

[0022] The matching module is configured to search for a set of theoretical arrival time differences that are closest to the actual arrival time difference results in the transformer simulation delay database, determine the local discharge source coordinates of the transformer three-dimensional simulation model based on the mapping relationship, and then determine the local discharge source positioning result of the actual transformer.

[0023] One or more of the above technical solutions have the following beneficial effects:

[0024] The present invention provides a transformer partial discharge source positioning method and system based on a simulated time delay database. A three-dimensional transformer model is established by using simulation software to simulate the propagation characteristics of partial discharge ultra-high frequency signals inside the transformer, thereby determining the optimal installation position of the ultra-high frequency sensor and the TDOA database. With the help of the mapping relationship between the coordinates of each partial discharge source and the TDOA of the ultra-high frequency sensor, the spatial position of the PD is finally determined.

[0025] The present invention proposes a method for determining the optimal arrangement position of UHF sensors using a sensor installation heat map based on simulation software, which effectively enhances the sensitivity of built-in UHF sensors in detecting partial discharge and improves the detection capability of the positioning system.

[0026] In view of the problem that the traditional TDOA equations do not take into account the refraction, reflection, diffraction and other situations that may occur in the transformer, the present invention proposes to use simulation software to establish a three-dimensional model that takes into account the complex structure inside the transformer, and calculate the theoretical arrival time difference of the corresponding ultra-high frequency signal when partial discharge occurs at different positions, so as to establish a TDOA database. This method can fully consider the impact of non-line-of-sight propagation of ultra-high frequency signals, and effectively solve the shortcomings of the traditional TDOA mathematical model that local optimal solutions will appear in iterative optimization. By searching the TDOA database of the transformer and finding a group of TDOAs with the smallest mean square error result, the location of the local discharge source can be determined more quickly and accurately.

[0027] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0029] Figure 1 This is a framework flow chart of an embodiment of the present invention.

[0030] Figure 2 The figure is a flowchart of the overall steps of the first embodiment of the present invention.

[0031] Figure 3 It is a three-dimensional schematic diagram of the overall structure of the transformer simulation model.

[0032] Figure 4 This is a schematic diagram of the internal structure of the transformer simulation model.

[0033] Figure 5 This is a top view schematic diagram of the internal structure of the transformer simulation model.

[0034] Figure 6 This is a front view of the electric field intensity distribution inside the transformer when partial discharge occurs between phases A and B of the transformer and the simulation time is 1ns.

[0035] Figure 7 This is a top view of the electric field intensity distribution inside the transformer when partial discharge occurs between phases A and B of the transformer and the simulation time is 1ns.

[0036] Figure 8 This is a front view of the electric field intensity distribution inside the transformer when partial discharge occurs between phases A and B of the transformer and the simulation time is 4ns.

[0037] Fig. 9 This is a top view of the electric field intensity distribution inside the transformer when partial discharge occurs between phases A and B of the transformer and the simulation time is 4ns.

[0038] Fig.10 This is a front view of the electric field intensity distribution inside the transformer when partial discharge occurs between phases A and B of the transformer and the simulation time is 7ns.

[0039] Fig.11 This is a top view of the electric field intensity distribution inside the transformer when partial discharge occurs between phases A and B of the transformer and the simulation time is 7ns.

[0040] Fig.12 for Figure 6-Figure 11 Schematic diagram of the electric field strength levels in .

[0041] Fig.13 Thermal map for sensor installation on the transformer front tank wall.

[0042] Fig.14 This is a schematic diagram of the installation layout of the UHF sensor.

[0043] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0044] 1. Iron core, 2. Clamp, 3. Pressure plate, 4. Winding coil, 5. Lead wire, 6. Tap changer, 7. Insulation paper, 8. Transformer casing. DETAILED DESCRIPTION

[0045] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0046] It should be noted that the terms used herein are for describing specific embodiments only and are not intended to be limiting of exemplary embodiments according to the present invention.

[0047] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0048] Embodiment 1

[0049] The embodiment of the present invention provides a method for locating the local discharge source of a transformer based on a simulated time delay database. First, a three-dimensional model of the transformer is established using simulation software to simulate the propagation characteristics of the local discharge signal inside the transformer; then the installation heat map is calculated to determine the optimal installation position of the ultra-high frequency sensor; then a mapping relationship between the local discharge source coordinates and the TDOA of the ultra-high frequency sensor is established as the TDOA database of the transformer; finally, the local discharge source is located by searching for a group of TDOAs with the smallest mean square error result in the TDOA database. The ultra-high frequency sensor installation strategy proposed by the present invention can enhance the sensitivity of the built-in ultra-high frequency sensor in detecting partial discharge. The local discharge source can be located by locating the local discharge source through the TDOA database, which can fully consider the influence of the non-line-of-sight propagation of the ultra-high frequency signal and improve the local discharge positioning accuracy.

[0050] Next, the technical contents of the embodiments of the present invention will be described in detail.

[0051] like Figure 1 and Figure 2 As shown, a transformer partial discharge source location method based on a simulated time delay database, the specific transformer partial discharge location steps include:

[0052] Step 1: Establish a three-dimensional simulation model of the transformer with the same size and structure as the transformer to be tested in the finite element simulation software;

[0053] Step 2: Subdivide the transformer model space into a limited number of small grids, and use simulation software to simulate the propagation characteristics of the partial discharge UHF signal generated inside the transformer when the local discharge source is at the center of each small grid;

[0054] Step 3: Calculate the heat values ​​of different areas on each wall of the transformer receiving the partial discharge signal, and obtain the UHF sensor installation heat map;

[0055] Step 4: Determine the best installation location for the UHF sensor;

[0056] Step 5: Use simulation software to calculate the time required for the partial discharge signal to propagate from the discharge source to each UHF sensor when the partial discharge source is at the center of each small grid;

[0057] Step 6: Establish the mapping relationship between the local discharge source coordinates and the TDOA of the UHF sensor as the TDOA database of the transformer;

[0058] Step 7: Install the built-in UHF sensor on the actual transformer, detect the partial discharge signal, and use the corresponding time delay algorithm to calculate the actual TDOA between each sensor;

[0059] Step 8: Search the transformer TDOA database for a set of TDOAs that is closest to the actual TDOA result. The mapped local discharge source coordinates are the final positioning results.

[0060] In some embodiments, the three-dimensional simulation model of the transformer includes structures such as the oil tank core, ABC three-phase windings and insulation, iron yokes and side yokes, clamps, insulating pressure plates and pads, wiring and voltage regulating switches.

[0061] In some embodiments, the method of spatial grid division of the transformer model in step 2 is:

[0062] If the internal length of the transformer is X cm, inner width Y cm, inner height Z cm, press u × v × w cm 3 The cube subdivides the three-dimensional space of the transformer into a finite number of small grids ( X , Y , Z can be respectively u , v , w divisible by), then there are a total of ( X × Y × Z ) / ( u × v × w) small spatial grids. The center of each small spatial grid is u × v × w cm 3 The geometric center of the cube.

[0063] In some embodiments, the method for calculating the heat value of the partial discharge signal received in a certain area on the box wall in step 3 is:

[0064]

[0065] in, H Represents the heat value of a certain area on the box wall receiving the partial discharge signal; s is the grid number; Representative in the s The probability of partial discharge occurring at a small grid is usually set to 1; Representative s When partial discharge occurs at a small grid, a certain area on the box wall receives the maximum amplitude of the UHF signal. The higher the heat value of a certain area on the box wall, the better the sensitivity of the UHF sensor installed in the area to detect partial discharge signals.

[0066] Since the top and bottom of the transformer are usually not suitable for installing UHF sensors, and the transformer structure has a certain symmetry, when obtaining the sensor installation thermal map, it is only necessary to calculate the heat values ​​of each point on the front and side box walls of the transformer.

[0067] In some embodiments, the strategy for determining the optimal installation position of the UHF sensor in step 4 is:

[0068] ① The number of built-in UHF sensors installed on the transformer should be no less than 4, and at least one built-in UHF sensor should be installed on each wall of the transformer except the top and bottom;

[0069] ② When the number of UHF sensors is more than 4, multiple built-in UHF sensors should be installed on the wall of the transformer with the largest area;

[0070] ③ According to the sensor installation heat map of different box wall surfaces, the UHF sensor should first be installed at the position with the highest heat value on each surface, then at the position with the second highest heat value, and so on;

[0071] ④ The spatial arrangement of the UHF sensor on the transformer should be as symmetrical as possible about the center point of the transformer.

[0072] In some embodiments, the method for determining the time when each UHF sensor receives the partial discharge signal in step 5 is:

[0073] Simulation software is based ons The time when local discharge occurs at each small grid is taken as the zero time for transient calculation. Probes are placed at the position of each UHF sensor to obtain the curve of the amplitude of the UHF electromagnetic wave signal received by each UHF sensor changing with time. i The time it takes for a UHF sensor to receive a partial discharge signal It is the moment when the amplitude of the UHF electromagnetic wave signal exceeds the set threshold for the first time.

[0074] In some embodiments, as described in step 6, the specific process of establishing the TDOA database of the transformer is:

[0075] First, the simulation software can be used to obtain the internal structure of the transformer. s When a partial discharge occurs at a small grid, the UHF signal propagates from the discharge source to the i The time for each UHF sensor position is , the UHF signal propagates from the discharge source to the j The time for each UHF sensor position is , at this time i UHF sensor and j The time difference of arrival of signals between UHF sensors for:

[0076]

[0077] Take one corner of the transformer as the origin of space and establish a three-dimensional rectangular coordinate system. s The center point of each small grid is ( x s , y s , z s ), then we can get the following pair of mapping relationships:

[0078]

[0079] in, N Represents the total number of UHF sensors installed, N ≥4; s is the serial number of the small grid, which is subdivided into ( X ×Y×Z ) / ( u×v×w ) small spatial grids, so the transformer TDOA database has a total of ( X × Y × Z ) / ( u × v × w ) for mapping.

[0080] In some embodiments, in step 7, the corresponding time delay algorithm adopts an improved small window cross-correlation algorithm, and the implementation steps of the algorithm are:

[0081] Step 7.1: Analyze the partial discharge signal at different times. M First, calculate the comprehensive correlation of the signals collected by the same UHF sensor at each time. The formula is:

[0082]

[0083] in, p and q Represents the sampling number; Represents the same UHF sensor p The magnitude of the comprehensive mutual correlation of the sub-collected signals; M is the total number of sampling times; t is the signal sampling point number; L is the length of the sampling signal sequence; Represents the same UHF sensor p subsampled signal sequence; Represents the same UHF sensor q Subsampled signal sequence.

[0084] from Select the maximum value The corresponding acquisition signal sequence As the partial discharge reference signal received by the UHF sensor, calculate the same UHF sensor q Second-rate( q ≠ k ) The generalized cross-correlation result of the sampled signal and the reference signal, find the corresponding value when the generalized cross-correlation value is the largest τ The value is q The displacement of the sampling points between the sub-sampled signal and the reference signal τ q , τ Indicates the size of the displacement of the sampling points. Find all the sampling times corresponding to τ q Value size, where the reference signal Corresponding τ q The value is 0. The average waveform is obtained according to the following formula :

[0085]

[0086] in, Indicates i Average signal waveform of UHF sensors; τ q Representative q The size of the sampling point displacement between the sub-sampled signal and the reference signal; t is the signal sampling point number, t ∈[1, L ]; M is the total number of sampling times; Represents the same UHF sensor q Subsampled signal sequence.

[0087] Step 7.2, i Average signal waveform of a UHF sensor The peak position m As the center, a length of 2 n The interval is used as the window function. Calculate the n Under the value, the window function and the j Average signal waveform of a UHF sensor ( i ≠ j )’s cross-correlation stability function :

[0088]

[0089] in, n Represents the half length of the window function; The half-length of the small window is n Time i A UHF sensor and j Cross-correlation stability of signals from UHF sensors; τ Indicates the size of the displacement of the sampling points, and its upper limit is β , the lower limit is - α ; t is the signal sampling point number; Representative i The average signal of the UHF sensor t The signal amplitude of each sampling point; Representative j The average signal of the UHF sensor is ( t + τ ) signal amplitude of the sampling points; Representative j The average signal of the UHF sensor is ( t + τ+1 ) signal amplitude of the sampling points; m Indicates signal The number of sampling points when the amplitude is maximum.

[0090] Step 7.3, calculate The first difference of , when a difference result When it is less than the set threshold, select The half-length of the optimal window function.

[0091] Step 7.4, calculate the half length of the window function as At that time, i Average signal waveform of a UHF sensor With j Average signal waveform of a UHF sensor ( i ≠ j ) small window cross-correlation result :

[0092]

[0093] in, Represents the half length of the optimal window function; The displacement size of the representative sampling points is τ At that time, i A UHF sensor and j Small window cross-correlation values ​​between UHF sensors.

[0094] when When taking the maximum value, the selected τ Multiply by the sampling time interval to get the i A UHF sensor and j The actual arrival time difference of the signal between the UHF sensors .

[0095] In some embodiments, in step 8, a group of TDOAs in the TDOA database that is closest to the actual TDOA result is searched, and the method adopted is to calculate the mean square error between the actual TDOA and each group of TDOAs in the TDOA database, and the formula is:

[0096]

[0097] in, i , j , l is the UHF sensor serial number; s is the sequence number of the small grid; N is the total number of UHF sensors; is the first i UHF sensor and j The actual arrival time difference between the UHF sensors, The first sWhen partial discharge occurs at a small grid, i UHF sensor and j The theoretical arrival time difference between UHF sensors; Represents the objective function f The variable at the minimum value s value.

[0098] The TDOA database ( X × Y × Z ) / ( u × v × w ) Substitute the arrival time differences of the two groups into the equation , when the objective function When the value is the smallest, the arrival time difference group entered at this time The corresponding grid center point coordinates This is the final partial discharge location result.

[0099] Next, the technical solution of this embodiment will be further explained in detail with reference to the accompanying drawings.

[0100] This embodiment takes the installation of 6 UHF sensors inside a real transformer with a size of 148×72×100 cm as an example to specifically illustrate the implementation of the method of this embodiment.

[0101] like Figure 1 The figure shows a framework flow chart of this embodiment, which includes a true transformer, a signal acquisition system, a TDOA database and a positioning system software.

[0102] As mentioned above, firstly, based on the real transformer, the optimal installation position of the UHF sensor is finally obtained by simulation method, and the mapping relationship between the local discharge source coordinates and the TDOA of the UHF sensor is established, and the TDOA database of the transformer is constructed;

[0103] Based on the optimal installation position of the UHF sensor, the UHF sensor is installed on the real transformer, and the signal acquisition system is used to collect the data received by the UHF sensor (the signal collected by the UHF sensor each time);

[0104] The data is transmitted to the positioning system software through the interactive interface. The actual arrival time difference between the UHF sensors is obtained after calculation. Finally, based on the TDOA database of the transformer, a group of TDOA local discharge sources with the smallest mean square error between the actual arrival time difference and the TDOA database is searched for to obtain the final positioning result and output it.

[0105] See also Figure 2The operation steps of the transformer partial discharge source location method based on the simulation time delay database in this embodiment are as follows:

[0106] Step 1: In the simulation software COMSOL, a three-dimensional simulation model of the transformer is established with the same size and structure as the transformer to be tested, including the oil tank core, ABC three-phase winding and insulation, iron yoke and side yoke, clamps, insulating pressure plates and pads, wiring and voltage regulating switches and other structures.

[0107] like Figure 3 The figure shows an overall schematic diagram of a transformer simulation model, wherein the outermost layer of the model is a transformer casing 8.

[0108] The front view and top view of the internal structure of the model are as follows Figure 4 and Figure 5 The internal structure of the simulated transformer includes the core 1, the clamp 2, the pressure plate 3, the winding coil 4 (including ABC three phases), the lead wire 5, the tap switch 6, the insulating paper 7 and other components.

[0109] The relative dielectric constant of the insulating oil is 2.24; the relative dielectric constant of the insulating paper is 4; the relative magnetic permeability of the iron core is 2000, and the electrical conductivity is 9.93×10 6 S / m; winding coil conductivity 5.78×10 7 S / m; fuel tank shell conductivity 5×10 6 S / m.

[0110] Step 2: The inner length of the transformer is 148 cm, the inner width is 72 cm, and the inner height is 100 cm. 3 The cube subdivides the three-dimensional space of the transformer model into a finite number of small spatial grids, a total of 133,200 small spatial grids. The center of each small spatial grid is 2×2×2cm 3 The geometric center of a cube.

[0111] An electric point dipole is set as a partial discharge source inside the model, and the simulation software COMSOL is used to simulate the propagation characteristics of the partial discharge ultra-high frequency signal generated inside the transformer when the partial discharge source is at the center of each small grid. Figure 6-Figure 11 This is the UHF signal propagation characteristic diagram when partial discharge occurs at a certain point between phases A and B of the transformer.

[0112] in, Figure 6 and Figure 7 They respectively represent the front view and top view of the electric field intensity distribution in the transformer when the simulation time is 1ns; Figure 8 and Fig. 9 They respectively represent the front view and top view of the electric field intensity distribution in the transformer when the simulation time is 4ns; Fig.10 and Fig.11They respectively represent the front view and top view of the electric field intensity distribution in the transformer when the simulation time is 7ns.

[0113] according to Fig.12 As shown, the more the color at a certain point in space at a certain moment is redder, the stronger the UHF signal is; the more the color is bluer, the weaker the UHF signal is.

[0114] Figure 6 and Figure 7 It is shown in the figure that the maximum value of the electric field strength in the transformer when the simulation time is 1ns is: 1.59913×10 6 V / m;

[0115] Figure 8 and Fig. 9 It is shown in the figure that the maximum value of the electric field strength in the transformer when the simulation time is 4ns is: 1.60967×10 6 V / m;

[0116] Fig.10 and Fig.11 It is shown in the figure that the maximum value of the electric field strength in the transformer is 1.57841×10 6 V / m.

[0117] Step 3: Calculate the heat value of different areas on each wall of the transformer receiving the partial discharge signal. Take the front wall of the transformer as an example, the area of ​​this surface is 148×100 cm 2 , according to 9.25×20 cm 2 The area is divided into 16×5 regions by small grids, and the heat value of the local discharge signal received in each region is calculated as follows:

[0118]

[0119] in, H Represents the heat value of a certain area on the box wall receiving the partial discharge signal; s is the grid number; Representative in the s The probability of partial discharge occurring at a small grid is usually set to 1; Representative s When local discharge occurs at a small grid, a certain area on the box wall receives the maximum amplitude of the UHF signal.

[0120] The higher the heat value of a certain area on the box wall, the better the sensitivity of detecting partial discharge signals when installing a UHF sensor in that area.

[0121] Finally, the heat value results of 16×5 different areas are obtained and combined into the sensor installation heat map on the front wall of the transformer, as shown in Fig.13 shown.

[0122] like Fig.13 As shown, the length and height of the transformer front wall are divided into equal parts, and length × height = 16 × 5 different areas are obtained, and the heat value results of each different area are specifically displayed with numerical values ​​in each area. The heat value is assigned different color depths according to the size, and is divided into multiple levels. The value on the far right is an exemplary depth value level. The lighter the color, the lower the heat value, and the darker the color, the higher the heat value; the length of each equal part of the transformer front wall is represented by the AP mark; the height of each equal part of the transformer front wall is represented by the ae mark. It can be seen that the highest heat value of the transformer front wall is in the Na area. Installing a UHF sensor in this area has the best sensitivity for detecting partial discharge.

[0123] Since the top and bottom of the transformer are usually not suitable for installing UHF sensors, and the transformer structure is symmetrical in front and back and left and right, when obtaining the sensor installation thermal map, it is only necessary to calculate the heat values ​​of each point on the front and side box walls of the transformer.

[0124] Step 4: The best installation location strategy for the UHF sensor is:

[0125] ① The number of built-in UHF sensors installed on the transformer should be no less than 4, and at least one built-in UHF sensor should be installed on each wall of the transformer except the top and bottom;

[0126] ② When the number of UHF sensors is more than 4, multiple built-in UHF sensors should be installed on the wall of the transformer with the largest area;

[0127] ③ According to the sensor installation heat map of different box wall surfaces, the UHF sensor should first be installed at the position with the highest heat value on each surface, then at the position with the second highest heat value, and so on;

[0128] ④ The spatial arrangement of the UHF sensor on the transformer should be as symmetrical as possible about the center point of the transformer.

[0129] Now take one corner of the transformer as the coordinate origin O Construct a spatial rectangular coordinate system with the inner width, inner length and inner height of the transformer as the coordinate system x, y, z According to the installation heat map, the installation positions of the 6 UHF sensors are finally determined as S 1(124.9,0,70)cm, S 2(23.1, 72, 30)cm, S 3(0, 40.5, 50)cm, S 4(148, 31.5, 50) cm, S5(124.9,0, 10)cm, S 6(23.1, 72, 90)cm; S 1. S 5 Installed at the two places with the highest heat value on the front wall of the transformer, S 2. S 6 are installed on the back wall of the transformer, respectively S 1. S 5 position about the center point of the transformer Q symmetry, S 3 Installed at the place with the highest heat value on the side wall of the transformer, S 4 is installed on the other side wall of the transformer, S 3 is located about the center point of the transformer Q Symmetrical, UHF sensor installation layout diagram as shown below Fig.14 shown.

[0130] Step 5: After determining the installation location of the UHF sensor, use the simulation software COMSOL to calculate the time required for the partial discharge signal to propagate from the discharge source to each UHF sensor when the partial discharge source is at the center of each small grid.

[0131] For example, when the simulation software COMSOL is used to simulate the partial discharge source at the center of the 53685th small grid (69, 11, 41) cm, the time when the partial discharge occurs at the 53685th small grid is taken as the zero time for transient calculation, the time unit is ns, the output step size is range(0,0.1,10) ns, and probes are placed at the positions of each UHF sensor. The curve of the amplitude of the UHF electromagnetic wave signal received by each UHF sensor changing with time is obtained. The time when each UHF sensor receives the partial discharge signal is regarded as the time when the amplitude of the electromagnetic wave signal exceeds the set threshold for the first time. It can be calculated that the time when the six UHF sensors receive the partial discharge signal is 3.4ns, 4.5ns, 5.7ns, 6.5ns, 3.8ns, and 5.1ns, respectively.

[0132] Step 6: Establish the mapping relationship between the local discharge source coordinates and the TDOA of the UHF sensor as the TDOA database of the transformer.

[0133] Calculate the TDOA between UHF sensors according to the following formula:

[0134]

[0135] The UHF signal propagates from the discharge source to the i The time for each UHF sensor position is ; The UHF signal propagates from the discharge source to the jThe time for each UHF sensor position is ;No. i UHF sensor and j The signal arrival time difference between the UHF sensors is .

[0136] For example, UHF sensors S 2 with UHF sensor S 1 arrival time difference By grouping the TDOAs between all UHF sensors, we can get the following pair of mapping relationships.

[0137]

[0138] When the local discharge source is located at the center of each small grid, the TDOA between the corresponding UHF sensors is calculated, and all mapping relationships are stored in the TDOA database of the transformer.

[0139] Step 7: Install 6 built-in UHF sensors on the actual transformer and build in an air gap defect as the local discharge source. The coordinates of the local discharge source are set to P (128, 65, 50) cm. The partial discharge signal generated by the air gap defect is detected by a UHF sensor, and the actual TDOA between the UHF sensors is calculated using the improved small window cross-correlation algorithm;

[0140] The specific implementation steps of the improved small window cross-correlation algorithm are as follows:

[0141] Step 7.1, collect the partial discharge signal 10 times at different times, and the length of each collected signal is 5000. First, calculate the comprehensive correlation size of each collected signal of the same UHF sensor, and the formula is:

[0142]

[0143] in, p and q Represents the sampling number; Represents the same UHF sensor p The magnitude of the comprehensive mutual correlation of the sub-collected signals; t is the signal sampling point number; Represents the same UHF sensor p subsampled signal sequence; Represents the same UHF sensor q Subsampled signal sequence.

[0144] from Select the maximum value The corresponding acquisition signal sequence As the partial discharge reference signal received by the UHF sensor, calculate the same UHF sensor q Second-rate( q ≠ k ) The generalized cross-correlation result of the sampled signal and the reference signal, find the corresponding value when the generalized cross-correlation value is the largest τ The value is q The displacement of the sampling points between the sub-sampled signal and the reference signal τ q . Find all the sampling times corresponding to τ q Value size, where the reference signal Corresponding τ q The value is 0. The average waveform is obtained according to the following formula :

[0145]

[0146] in, Indicates i Average signal waveform of UHF sensors; τ q Representative q The size of the sampling point displacement between the sub-sampled signal and the reference signal; t is the signal sampling point number, t ∈[1, 5000]; Represents the same UHF sensor q Subsampled signal sequence.

[0147] Step 7.2, i Average signal waveform of a UHF sensor The peak position m As the center, a length of 2 n The interval is used as the window function, n ∈[1,500]. Calculated in different n Under the value, the window function and the j Average signal waveform of a UHF sensor ( i ≠ j )’s cross-correlation stability function :

[0148]

[0149] in, n Represents the half length of the window function; The half-length of the small window is n Time i A UHF sensor and jSignal cross-correlation stability of UHF sensors; τ Indicates the size of the sampling point displacement, with an upper limit of 250 and a lower limit of -250; t is the signal sampling point number; Representative i The average signal of the UHF sensor t The signal amplitude of each sampling point; Representative j The average signal of the UHF sensor is ( t + τ ) signal amplitude of the sampling points; m Indicates signal b i The number of sampling points when the amplitude is maximum;

[0150] Step 7.3, calculate The first difference of , when a difference result When it is less than the set threshold, select The half-length of the optimal window function;

[0151] Step 7.4, calculate the half length of the window function as At that time, i Average signal waveform of a UHF sensor With j Average signal waveform of a UHF sensor ( i ≠ j ) small window cross-correlation result :

[0152]

[0153] in, n 0 represents the half length of the optimal window function; The displacement size of the representative sampling points is τ At that time, i A UHF sensor and j The small window cross-correlation value between the UHF sensors. When taking the maximum value, the selected τ Multiply by the sampling time interval to get the i A UHF sensor and j The actual arrival time difference of the signal between the UHF sensors ;

[0154] According to the above steps, calculate the arrival time difference between all UHF sensors, where , , …, .

[0155] Step 8: Search the TDOA database of the transformer and find the set of TDOA with the smallest mean square error result. The mapped local discharge source coordinates (123, 67, 50) cm are the final positioning results.

[0156] The formula for determining the partial discharge location result using the mean square error in step 8 is:

[0157]

[0158] in, i , j is the UHF sensor serial number; s is the sequence number of the small grid; is the first i UHF sensor and j The actual arrival time difference between the UHF sensors, The first s When partial discharge occurs at a small grid, i UHF sensor and j The theoretical arrival time difference between UHF sensors; Represents the objective function f The variable at the minimum value s value.

[0159] Substitute the 133,200 arrival time differences in the TDOA database into the equation , when the objective function value is the minimum, the arrival time difference group input at this time is The corresponding grid center point coordinates (123, 67, 50) cm are the final partial discharge location results.

[0160] The final positioning result is (123, 67, 50) cm. The field verification result is close to the actual defect position, and the positioning error is small, which is comparable to the laboratory measurement result.

[0161] Embodiment 2

[0162] This embodiment discloses a transformer partial discharge source locating system based on a simulation time delay database.

[0163] The transformer partial discharge source location system based on the simulation time delay database includes:

[0164] The simulation model building module is configured to: build a three-dimensional simulation model of the transformer;

[0165] The optimal installation position determination module is configured to: divide the transformer three-dimensional simulation model into grids, simulate the heat values ​​of the partial discharge ultra-high frequency signals received by different areas on each box wall of the transformer three-dimensional simulation model when the partial discharge source is at the center of each grid, obtain the ultra-high frequency sensor installation heat map, and determine the optimal installation position of the ultra-high frequency sensor;

[0166] The theoretical arrival time difference calculation module is configured to: based on the determined optimal installation position, simulate and calculate the theoretical arrival time difference between the UHF sensors when the local discharge source is at the center of each grid;

[0167] The simulation time delay database construction module is configured to: establish a mapping relationship between the local discharge source coordinates of the three-dimensional simulation model of the transformer and the theoretical arrival time difference between the UHF sensor, and construct a simulation time delay database of the transformer;

[0168] The actual arrival time difference calculation module is configured to: install a built-in UHF sensor at a corresponding position on the actual transformer, detect the partial discharge UHF signal, and calculate the actual arrival time difference between the UHF sensors;

[0169] The matching module is configured to search for a set of theoretical arrival time differences that are closest to the actual arrival time difference results in the transformer simulation delay database, determine the local discharge source coordinates of the transformer three-dimensional simulation model based on the mapping relationship, and then determine the local discharge source positioning result of the actual transformer.

[0170] The above-mentioned simulation model building module, optimal installation position determination module, theoretical arrival time difference calculation module, simulation delay database construction module, actual arrival time difference calculation module and matching module are specifically used to achieve:

[0171] In some embodiments, the three-dimensional simulation model of the transformer includes structures such as the oil tank core, ABC three-phase windings and insulation, iron yokes and side yokes, clamps, insulating pressure plates and pads, wiring and voltage regulating switches.

[0172] In some embodiments, the method of spatial grid division of the transformer model is:

[0173] If the internal length of the transformer is X cm, inner width Y cm, inner height Z cm, press u × v × w cm 3 The cube subdivides the three-dimensional space of the transformer into a finite number of small grids ( X , Y , Z can be respectively u , v , wdivisible by), then there are a total of ( X × Y × Z ) / ( u × v × w ) small spatial grids. The center of each small spatial grid is u × v × w cm 3 The geometric center of the cube.

[0174] In some embodiments, the heat value of the partial discharge signal received by a certain area on the box wall is calculated as follows:

[0175]

[0176] in, H Represents the heat value of a certain area on the box wall receiving the partial discharge signal; s is the grid number; Representative in the s The probability of partial discharge occurring at a small grid is usually set to 1; Representative s When partial discharge occurs at a small grid, a certain area on the box wall receives the maximum amplitude of the UHF signal. The higher the heat value of a certain area on the box wall, the better the sensitivity of the UHF sensor installed in the area to detect partial discharge signals.

[0177] Since the top and bottom of the transformer are usually not suitable for installing UHF sensors, and the transformer structure has a certain symmetry, when obtaining the sensor installation thermal map, it is only necessary to calculate the heat values ​​of each point on the front and side box walls of the transformer.

[0178] In some embodiments, the strategy for determining the best installation location of the UHF sensor is:

[0179] ① The number of built-in UHF sensors installed on the transformer should be no less than 4, and at least one built-in UHF sensor should be installed on each wall of the transformer except the top and bottom;

[0180] ② When the number of UHF sensors is more than 4, multiple built-in UHF sensors should be installed on the wall of the transformer with the largest area;

[0181] ③ According to the sensor installation heat map of different box wall surfaces, the UHF sensor should first be installed at the position with the highest heat value on each surface, then at the position with the second highest heat value, and so on;

[0182] ④ The spatial arrangement of the UHF sensor on the transformer should be as symmetrical as possible about the center point of the transformer;

[0183] In some embodiments, the time when each UHF sensor receives the partial discharge signal is determined by:

[0184] Simulation software is based on s The time when local discharge occurs at each small grid is taken as the zero time for transient calculation. Probes are placed at the position of each UHF sensor to obtain the curve of the amplitude of the UHF electromagnetic wave signal received by each UHF sensor changing with time. i The time it takes for a UHF sensor to receive a partial discharge signal It is the moment when the amplitude of the UHF electromagnetic wave signal exceeds the set threshold for the first time.

[0185] In some embodiments, the specific process of establishing the transformer simulation delay database is as follows:

[0186] First, the simulation software can be used to obtain the internal structure of the transformer. s When a partial discharge occurs at a small grid, the UHF signal propagates from the discharge source to the i The time for each UHF sensor position , at this time i UHF sensor and j The time difference of arrival of signals between UHF sensors for:

[0187]

[0188] Take one corner of the transformer as the origin of space and establish a three-dimensional rectangular coordinate system. s The center point of each small grid is ( x s , y s , z s ), then we can get the following pair of mapping relationships:

[0189]

[0190] in, N Represents the total number of UHF sensors installed, N ≥4; s is the serial number of the small grid, which is subdivided into ( X ×Y×Z ) / ( u×v×w ) small spatial grids, so the transformer TDOA database has a total of ( X × Y × Z ) / ( u × v × w) for mapping.

[0191] In some embodiments, an improved small window cross-correlation algorithm is used to calculate the actual arrival time difference between UHF sensors. The algorithm implementation steps are:

[0192] Step 7.1: Analyze the partial discharge signal at different times. M First, calculate the comprehensive correlation of the signals collected by the same UHF sensor at each time. The formula is:

[0193]

[0194] in, p and q Represents the sampling number; Represents the same UHF sensor p The magnitude of the comprehensive mutual correlation of the sub-collected signals; M is the total number of sampling times; t is the signal sampling point number; L is the length of the sampling signal sequence; Represents the same UHF sensor p subsampled signal sequence; Represents the same UHF sensor q Subsampled signal sequence.

[0195] from Select the maximum value The corresponding acquisition signal sequence As the partial discharge reference signal received by the UHF sensor, calculate the same UHF sensor q Second-rate( q ≠ k ) The generalized cross-correlation result of the sampled signal and the reference signal, find the corresponding value when the generalized cross-correlation value is the largest τ The value is q The displacement of the sampling points between the sub-sampled signal and the reference signal τ q . Find all the sampling times corresponding to τ q Value size, where the reference signal Corresponding τ q The value is 0. The average waveform is obtained according to the following formula :

[0196]

[0197] in, Indicates i Average signal waveform of UHF sensors; τ q Representative q The size of the sampling point displacement between the sub-sampled signal and the reference signal; t is the signal sampling point number, t ∈[1, L ]; M is the total number of sampling times; Represents the same UHF sensor q Subsampled signal sequence.

[0198] Step 7.2, i Average signal waveform of a UHF sensor The peak position m As the center, a length of 2 n The interval is used as the window function. Calculate the n Under the value, the window function and the j Average signal waveform of a UHF sensor ( i ≠ j )’s cross-correlation stability function :

[0199]

[0200] in, n Represents the half length of the window function; The half-length of the small window is n Time i A UHF sensor and j Cross-correlation stability of signals from UHF sensors; τ Indicates the size of the displacement of the sampling points, and its upper limit is β , the lower limit is - α ; t is the signal sampling point number; Representative i The average signal of the UHF sensor t The signal amplitude of each sampling point; Representative j The average signal of the UHF sensor is ( t + τ ) signal amplitude of the sampling points; m Indicates signal The number of sampling points when the amplitude is maximum.

[0201] Step 7.3, calculate The first difference of , when a difference result When it is less than the set threshold, select The half-length of the optimal window function.

[0202] Step 7.4, calculate the half length of the window function as At that time, i Average signal waveform of a UHF sensor With j Average signal waveform of a UHF sensor ( i ≠ j ) small window cross-correlation result :

[0203]

[0204] in, Represents the half length of the optimal window function; The displacement size of the representative sampling points is τ At that time, i A UHF sensor and j Small window cross-correlation values ​​between UHF sensors.

[0205] when When taking the maximum value, the selected τ Multiply by the sampling time interval to get the i A UHF sensor and j The actual arrival time difference of the signal between the UHF sensors .

[0206] In some embodiments, a group of TDOAs in the TDOA database that is closest to the actual TDOA result is searched by calculating the mean square error between the actual TDOA and each group of TDOAs in the TDOA database, and the formula is:

[0207]

[0208] in, i , j , l is the UHF sensor serial number; s is the sequence number of the small grid; N is the total number of UHF sensors; is the first i UHF sensor and j The actual arrival time difference between the UHF sensors, The first s When partial discharge occurs at a small grid, i UHF sensor and j The theoretical arrival time difference between UHF sensors; Represents the objective function fThe variable at the minimum value s value.

[0209] The TDOA database ( X × Y × Z ) / ( u × v × w ) Substitute the arrival time differences of the two groups into the equation , when the objective function When the value is the smallest, the arrival time difference group entered at this time The corresponding grid center point coordinates This is the final partial discharge location result.

[0210] Those skilled in the art should understand that the modules or steps of the present invention described above can be implemented by a general-purpose computer device, or alternatively, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. The present invention is not limited to any specific combination of hardware and software.

[0211] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A transformer partial discharge source location method based on a simulated time delay database, characterized in that: The following steps are involved: Establish a three-dimensional simulation model of the transformer; The three-dimensional simulation model of the transformer is divided into grids, and the heat values ​​of the partial discharge UHF signals received by different areas on each box wall of the three-dimensional simulation model of the transformer are simulated when the local discharge source is at the center of each grid, so as to obtain the UHF sensor installation heat map and determine the optimal installation position of the UHF sensor; Based on the determined optimal installation position, the theoretical arrival time difference between UHF sensors is simulated and calculated when the local discharge source is at the center of each grid; Establish the mapping relationship between the local discharge source coordinates of the transformer 3D simulation model and the theoretical arrival time difference between the UHF sensors, and build the transformer simulation delay database; Install the built-in UHF sensor at the corresponding position on the actual transformer, detect the UHF signal of partial discharge, and calculate the actual arrival time difference between the UHF sensors. Specifically, the improved small window cross-correlation algorithm is used to calculate the actual arrival time difference between the UHF sensors. The process is: calculate the comprehensive mutual correlation size of the signals collected by the same UHF sensor at each time, determine the partial discharge reference signal based on the maximum value of the comprehensive mutual correlation size, and then determine the first q The displacement of the sampling points between the sub-sampled signal and the reference signal τ q ,use τ q Calculate the i UHF Sensor q The average signal waveform of the sampling times is calculated as follows: ； Where t is the number of signal sampling points, t∈[1,L], and L is the length of the sampling signal sequence; M is the total number of sampling times; Represents the same UHF sensor q subsampled signal sequence; First i Average signal waveform of a UHF sensor The peak position is the center and the length is 2 n The interval is used as the window function and calculated in different n Under the value, the window function and the j Average signal waveform of a UHF sensor b j The cross-correlation stability function ,in i ≠ j； based on The first-order difference of determines the optimal half-length of the window function ; The half length of the window function is calculated as n 0 o'clock, i Average signal waveform of a UHF sensor With j Average signal waveform of a UHF sensor The small window cross-correlation result of ; when When taking the maximum value, the selected τ Multiply by the sampling time interval to get the i A UHF sensor and j The actual arrival time difference of the signals between the UHF sensors; where τ represents the displacement of the sampling points; A set of theoretical arrival time differences closest to the actual arrival time difference results is searched in the transformer simulation time delay database, and the local discharge source coordinates of the transformer three-dimensional simulation model are determined based on the mapping relationship, thereby determining the local discharge source positioning result of the actual transformer.

2. The transformer partial discharge source location method based on the simulation time delay database according to claim 1 is characterized in that: Establish a three-dimensional simulation model of the transformer, including: A three-dimensional simulation model of a transformer with the same size and structure as the transformer to be tested is established in the finite element simulation software. The structure of the three-dimensional simulation model of the transformer includes an oil tank core, ABC three-phase windings and insulation, an iron yoke and a side yoke, clamps, insulating pressure plates and pads, wiring and a voltage regulating switch.

3. The transformer partial discharge source location method based on the simulation time delay database according to claim 1 is characterized in that: The transformer 3D simulation model is divided into grids, including: Subdividing the three-dimensional space of the three-dimensional transformer simulation model into a finite number of space grids; The simulation software is used to simulate the propagation characteristics of the partial discharge UHF signal inside the transformer when the local discharge source is at the center of each grid.

4. The transformer partial discharge source location method based on the simulation time delay database according to claim 1 is characterized in that: The heat value of the partial discharge UHF signal received by different areas on each box wall of the three-dimensional simulation model of the transformer is calculated as follows: in, H Represents the heat value of a certain area on the box wall receiving the partial discharge signal; s is the grid number; Representative in the s The probability of partial discharge occurring at each small grid; Representative s When local discharge occurs at a small grid, a certain area on the box wall receives the maximum amplitude of the UHF signal; X , Y , Z They are the inner length and inner width of the transformer respectively. 、 inner height; u , v , w are the length, width, and height of the grid respectively.

5. The transformer partial discharge source location method based on the simulation time delay database according to claim 1, characterized in that: Determine the optimal installation position of the UHF sensor based on the installation strategy, wherein the installation strategy specifically includes: The number of UHF sensors installed on the transformer shall not be less than 4. Except for the top and bottom of the transformer box wall, at least one UHF sensor shall be installed on the other box walls; When the number of UHF sensors is more than 4, multiple UHF sensors should be installed on the wall of the transformer with the largest area. According to the sensor installation heat map of different box wall surfaces, the UHF sensor is first considered to be installed at the location with the highest heat value on each surface, followed by the location with the second highest heat value, and so on; The spatial arrangement of the UHF sensor on the transformer should be as symmetrical as possible about the center point of the transformer.

6. The transformer partial discharge source location method based on the simulation time delay database according to claim 4 is characterized in that: Based on the determined optimal installation position, the theoretical arrival time difference between UHF sensors when the local discharge source is at the center of each grid is simulated and calculated, including: According to the best installation position, probes are placed on the three-dimensional simulation model of the transformer to determine the time when each UHF sensor receives the partial discharge signal; The time when each UHF sensor receives the partial discharge signal is subtracted from each other to obtain the theoretical arrival time difference between the UHF sensors.

7. The transformer partial discharge source location method based on the simulation time delay database according to claim 6, characterized in that: Determine the time when each UHF sensor receives the partial discharge signal, including: Simulation software is based on s The moment when partial discharge occurs at each grid is taken as the zero moment for transient calculation. Based on the placed probes, the curve of the amplitude of the UHF electromagnetic wave signal received by each UHF sensor changing with time is obtained. i The time it takes for a UHF sensor to receive a partial discharge signal It is the moment when the amplitude of the UHF electromagnetic wave signal exceeds the set threshold for the first time.

8. The transformer partial discharge source location method based on the simulation time delay database according to claim 1, characterized in that: The mapping relationship between the local discharge source coordinates of the transformer 3D simulation model and the theoretical arrival time difference between the UHF sensors is established, and the transformer simulation delay database is constructed, including: Take one corner of the transformer as the origin of space and establish a three-dimensional rectangular coordinate system; The local discharge source coordinates of the transformer three-dimensional simulation model are set to the center point of each grid; A one-to-one mapping relationship is established between the coordinates of each local discharge source of the three-dimensional simulation model of the transformer and the theoretical arrival time difference between the corresponding ultra-high frequency sensors, so as to construct a simulation delay database of the transformer.

9. The transformer partial discharge source location method based on the simulation time delay database according to claim 1, characterized in that: Searching for a set of theoretical arrival time differences that are closest to the actual arrival time difference results in the transformer simulation time delay database, the specific method is: calculating the mean square error between the actual arrival time difference and each set of theoretical arrival time differences in the simulation delay database; The theoretical arrival time difference with the smallest mean square error is taken as the set of theoretical arrival time differences that are closest to the actual arrival time difference results.

10. A transformer partial discharge source location system based on a simulated time delay database, characterized in that: include: The simulation model building module is configured to: build a three-dimensional simulation model of the transformer; The optimal installation position determination module is configured to: divide the transformer three-dimensional simulation model into grids, simulate the heat values ​​of the partial discharge ultra-high frequency signals received by different areas on each box wall of the transformer three-dimensional simulation model when the partial discharge source is at the center of each grid, obtain the ultra-high frequency sensor installation heat map, and determine the optimal installation position of the ultra-high frequency sensor; The theoretical arrival time difference calculation module is configured to: based on the determined optimal installation position, simulate and calculate the theoretical arrival time difference between the UHF sensors when the local discharge source is at the center of each grid; The simulation time delay database construction module is configured to: establish a mapping relationship between the local discharge source coordinates of the three-dimensional simulation model of the transformer and the theoretical arrival time difference between the UHF sensor, and construct a simulation time delay database of the transformer; The actual arrival time difference calculation module is configured as follows: a built-in UHF sensor is installed at a corresponding position on the actual transformer, and the partial discharge UHF signal is detected, and the actual arrival time difference between the UHF sensors is calculated. Specifically, the improved small window cross-correlation algorithm is used to calculate the actual arrival time difference between the UHF sensors. The process is: calculate the comprehensive mutual correlation size of each acquisition signal of the same UHF sensor, determine the partial discharge reference signal based on the maximum value of the comprehensive mutual correlation size, and then determine the first q The displacement of the sampling points between the sub-sampled signal and the reference signal τ q ,use τ q Calculate the i UHF Sensor q The average signal waveform of the subsample , the specific calculation formula is: ； Where t is the number of signal sampling points, t∈[1,L], and L is the length of the sampling signal sequence; M is the total number of sampling times; Represents the same UHF sensor q subsampled signal sequence; First i Average signal waveform of a UHF sensor The peak position is the center and the length is 2 n The interval is used as the window function and calculated in different n Under the value, the window function and the j Average signal waveform of a UHF sensor b j The cross-correlation stability function ,in i ≠ j； based on The first-order difference of determines the optimal half-length of the window function ; The half length of the window function is calculated as n 0 o'clock, i Average signal waveform of a UHF sensor With j Average signal waveform of a UHF sensor The small window cross-correlation result of ; when When taking the maximum value, the selected τ Multiply by the sampling time interval to get the i A UHF sensor and j The actual arrival time difference of the signals between the UHF sensors; where τ represents the displacement of the sampling points; The matching module is configured to search for a set of theoretical arrival time differences that are closest to the actual arrival time difference results in the transformer simulation delay database, determine the local discharge source coordinates of the transformer three-dimensional simulation model based on the mapping relationship, and then determine the local discharge source positioning result of the actual transformer.

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