A method for locating partial discharge using a multi-group ultra-high frequency sensor in a transformer.

Abstract

This invention provides a method for locating partial discharge in a transformer using multi-group ultra-high frequency (UHF) sensors, comprising: acquiring n partial discharge signals; calculating the time difference between each pair of UHF sensors receiving the UHF partial discharge signals; selecting one of the four UHF sensors as a reference sensor, establishing a set of partial discharge source location equations based on the time difference between the propagation of the UHF signal generated by the partial discharge source to the reference sensor and the other three sensors, and obtaining the partial discharge source location results for the grouped UHF sensors; obtaining a location error weighting factor for the location result obtained under the k-th group; establishing an optimized coordinate search function for the partial discharge source based on the location result of each group and the location error weighting factor of each group, and obtaining the three-dimensional coordinates of the partial discharge source inside the transformer in space. This invention reduces the dependence of the location result on the time delay accuracy and effectively improves the location accuracy of the partial discharge source.

Description

Technical Field

[0001] This invention belongs to the field of transformer internal partial discharge location technology, and more specifically, relates to a method for partial discharge location using a multi-group ultra-high frequency sensor in a transformer. Background Technology

[0002] Partial discharge (PD) is a discharge phenomenon that occurs in a localized area when an insulation defect occurs inside electrical equipment. The presence of partial discharge seriously impairs the insulation performance of electrical equipment and can even cause the overall insulation performance of the equipment to be lost, leading to malfunctions.

[0003] Ultra-high frequency (UHF) detection technology is a rapidly developing method for diagnosing power distribution (PD) faults in electrical equipment in recent years. Due to its advantages such as strong anti-interference ability, wide detection bandwidth, and high sensitivity, it has been widely used in the location of PDs in high-voltage electrical equipment such as transformers.

[0004] The ultra-high frequency (UHF) sensor detects frequencies ranging from 300MHz to 1.5GHz. Traditional UHF localization methods utilize four UHF sensors and obtain the time difference between the UHF signal reaching each sensor and the other three. This allows for the establishment of a three-dimensional spatial coordinate localization equation set for the partial discharge source, which is then solved to obtain the source coordinates. However, this method fails to account for the significant errors caused by the time delay of the UHF signal due to the complex structure within the transformer. Furthermore, the extreme sensitivity of the localization equation set to this time delay leads to extremely large errors in the obtained partial discharge source coordinates, potentially resulting in localization failure. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for locating partial discharge of transformers using multi-group ultra-high frequency sensors, thereby solving the problem that existing locating methods suffer from significant errors due to the failure to consider the complex internal structure of transformers, which leads to large delays in ultra-high frequency signals.

[0006] This invention provides a method for locating partial discharge using a multi-group ultra-high frequency sensor in a transformer, comprising the following steps:

[0007] S1 acquires partial discharge signals simultaneously collected by n ultra-high frequency sensors targeting a transformer with internal insulation defects; where n ranges from 4... <n≤8;

[0008] S2 calculates the time difference between the reception of the UHF partial discharge signal by each pair of UHF sensors for the UHF signal collected by each UHF sensor.

[0009] S3 selects one of the four UHF sensors as a reference sensor, establishes a set of localization equations for the localization of the UHF signal generated by the local discharge power source to the reference sensor and the other three sensors based on the time difference between the UHF signal and the reference sensor, and obtains the localization result of the UHF power source of the grouped UHF sensors by solving the set of localization equations.

[0010] S4 calculates the positioning error weighting factor for the k-th group based on the positioning results of that group; where the value of k ranges from...

[0011] S5 establishes an optimization function for the local discharge source coordinates based on each set of positioning results and the positioning error weighting factor of each set of positioning results, and obtains the three-dimensional coordinates of the local discharge source inside the transformer in space by finding the optimal solution.

[0012] Furthermore, in step S2, the method for calculating the time difference of the UHF signal propagating from the insulation defect in the transformer to any two UHF sensors is as follows:

[0013] (1) The time t corresponding to the maximum value of the UHF signal collected by the i-th UHF sensor. i This is the moment when the ultra-high frequency signal generated during partial discharge propagates to the i-th ultra-high frequency sensor;

[0014] (2) The time delay of the signals received by the i-th and j-th UHF sensors from the partial discharge power supply inside the transformer is expressed as Δt. ij =t i -t j Where 1≤i≤n, 1≤j≤n, i≠j, t i t j These represent the times when the ultra-high frequency signal generated during partial discharge propagates to the i-th and j-th ultra-high frequency sensors, respectively.

[0015] Furthermore, the location equations for the partial discharge power source inside the transformer in step S3 are expressed as follows:

[0016]

[0017] Where (x,y,z) are the three-dimensional coordinates of the partial discharge source inside the transformer to be solved in space; t 1s Let x be the time it takes for the UHF signal to propagate from the partial discharge source to the reference sensor; i ,y i ,z i ) represents the known coordinates of the i-th UHF sensor; v represents the known propagation speed of UHF electromagnetic waves in transformer oil; Δt 12 , Δt 13 , Δt 14These are the time delays of the signals received by the first and second, third, and fourth UHF sensors from the partial discharge power supply inside the transformer, respectively.

[0018] Furthermore, in step S3, the solution of the localization equations of the partial discharge power source inside the transformer is transformed into an optimization problem as follows and then solved by the particle swarm optimization algorithm. Where (x,y,z) are the three-dimensional coordinates of the partial discharge source inside the transformer to be solved in space; t 1s Let x be the time it takes for the UHF signal to propagate from the partial discharge source to the reference sensor; i ,y i ,z i ) represents the known coordinates of the i-th UHF sensor; v represents the known propagation speed of UHF electromagnetic waves in transformer oil; Δt 1i Let be the time delay of the signal received by the first and i-th UHF sensors from the partial discharge power supply inside the transformer.

[0019] Furthermore, in step S5, the local discharge source optimization coordinate search function is expressed as:

[0020]

[0021] Where n represents the number of ultra-high frequency sensors; α ii This represents the weighting factor for the location results of group ii. (x k ,y k ,z k (x) represents the positioning result of the UHF sensor in the k-th group; s ,y s ,z s () represents the optimal coordinates of the local discharge source to be determined.

[0022] Furthermore, in step S4, taking the k-th positioning result obtained from the a, b, c, and d-th sensor groups as the center and an error sphere with radius r, a sufficient number of n random points are selected on the error sphere, and the difference between the time difference at each random point and the measured time difference is calculated. The result for the i-th point is denoted as... The positioning error weighting factor for the i-th point can be expressed as: The weighting factor for the k-th location result can be expressed as: in This represents the time difference error between the a-th and b-th sensor groups at the ii-th point on the error sphere. These represent the weighting factors of the time difference error of the sensors in groups a and b, groups a and c, and groups a and d at the i-th point on the error sphere, respectively. It represents the weight factor of the \(ii\)-th point on the error sphere corresponding to the positioning results obtained by the \(a\), \(b\), \(c\), and \(d\) groups of sensors; It represents the weight factor of the \(k\)-th group of positioning results; the value range of \(k\) is 0 < \(ii\) < \(nn\).

[0023] Furthermore, the radius \(r\) of the error sphere is 10 cm; the random point \(nn\) is 10000.

[0024] Furthermore, the bandwidth of the ultra-high frequency sensor is 300 MHz to 1.5 GHz; 4 < \(n\) ≤ 8; the ultra-high frequency signal acquisition device selects the Tektronix DPO7254C model oscilloscope, and the signal sampling rate is 20 GHz.

[0025] Through the above technical solutions conceived by the present invention, compared with the prior art, in the present invention, since the multiple groups of positioning results obtained by the multi-group sensor positioning are not evenly distributed around the actual positioning result, the time-delay sensitivity degree is measured according to the magnitude of the time-difference error of each group of positioning results on the positioning result error sphere, and the error weight factor is defined based on this, reducing the dependence of the positioning result on the time-delay accuracy and effectively improving the local discharge source positioning accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is the implementation flowchart of the local discharge positioning method for a transformer multi-group ultra-high frequency sensor provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] In order to make the purpose, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] The present invention provides a local discharge source positioning method for a transformer multi-group ultra-high frequency sensor. By grouping every four ultra-high frequency sensors and calculating the positioning error weight factors of the positioning results obtained under each grouping, and by establishing an optimization positioning result search function based on the positioning error weight factors, the optimal local discharge source positioning result is determined.

[0029] As Figure 1 shown, the local discharge positioning method for a transformer multi-group ultra-high frequency sensor provided by the present invention includes the following steps:

[0030] S1 Obtain the partial discharge signals collected by n (4 < n ≤ 8) ultra-high frequency sensors for a transformer with internal insulation defects at the same moment; among them, in step S1, the bandwidth of the ultra-high frequency sensor is 300 MHz to 1.5 GHz; 4 < n ≤ 8; the ultra-high frequency signal acquisition device selects an oscilloscope of model Tektronix DPO7254C, and the signal sampling rate is 20 GHz.

[0031] S2 For the ultra-high frequency signals collected by each ultra-high frequency sensor, calculate the time difference between the ultra-high frequency partial discharge signals received by every two ultra-high frequency sensors.

[0032] Among them, in step S2, the calculation method of the time difference for the ultra-high frequency signal to propagate from the insulation defect in the transformer to any two ultra-high frequency sensors is as follows:

[0033] (1) Take the moment t corresponding to the maximum value of the ultra-high frequency signal collected by the i-th (1 ≤ i ≤ n) ultra-high frequency sensor i as the moment when the ultra-high frequency signal generated during partial discharge propagates to the i-th ultra-high frequency sensor.

[0034] (2) The time delay of the signals from the internal partial discharge source in the transformer received by the i-th and j-th (1 ≤ j ≤ n, i ≠ j) ultra-high frequency sensors is expressed as Δt ij = t i - t j ; where t i , t j respectively represent the moments when the ultra-high frequency signal generated during partial discharge propagates to the i-th and j-th ultra-high frequency sensors.

[0035] S3 For every four ultra-high frequency sensors, select any one ultra-high frequency sensor as the reference sensor, and establish a partial discharge source location equation set based on the time differences of the ultra-high frequency signals generated by the partial discharge source propagating to the reference sensor and the other three sensors, and solve the partial discharge source location result of this group of ultra-high frequency sensors.

[0036] Among them, in step S3, the location equation set of the internal partial discharge source in the transformer is expressed as:

[0037]

[0038] Among them, (x, y, z) is the three-dimensional coordinate in space of the internal partial discharge source in the transformer to be solved; t 1s is the time to be solved for the ultra-high frequency signal to propagate from the partial discharge source to the reference sensor; (x i , y i , z i ) is the coordinate of the known i-th ultra-high frequency sensor; v is the known propagation speed of the ultra-high frequency electromagnetic wave in the transformer oil;; Δt 12, Δt 13 , Δt 14 are respectively the time delays of the signals received by the known first UHF sensor and the second, third, and fourth UHF sensors from the partial discharge source in the transformer.

[0039] In step S3, the solution of the localization equation system for the partial discharge source in the transformer is obtained by converting the solution problem of the equation system into an optimization problem as follows and performing optimization and solution through the particle swarm algorithm;

[0040]

[0041] where, (x, y, z) are the three-dimensional coordinates in space of the partial discharge source in the transformer to be solved; t 1s is the time for the UHF signal to be solved to propagate from the partial discharge source to the reference sensor; (x i , y i , z i ) are the coordinates of the known i-th UHF sensor; v is the known propagation speed of the UHF electromagnetic wave in the transformer oil; Δt 1i is the time delay of the signals received by the known first UHF sensor and the i-th UHF sensor from the partial discharge source in the transformer...

[0042] S4 For the k-th group obtained localization results, calculate the localization error weight factor of this group of localization results;

[0043] Specifically, in step S4, define an error spherical surface with the k-th group of localization results obtained by the a, b, c, d groups of sensors as the center of the sphere and r as the radius. Take a sufficient number of nn random points on the error spherical surface, and calculate the difference between the time difference at the random point and the measured time difference for each point. The result of the i-th point (0 < i < nn) is denoted as The localization error weight factor of the i-th point can be expressed as Then the weight factor of the k-th group of localization results can be expressed as where represents the time difference error of the a, b groups of sensors at the i-th point (0 < i < nn) on the error spherical surface; respectively represent the weight factors of the time difference errors of the a, b groups, a, c groups, and a, d groups of sensors at the i-th point (0 < i < nn) on the error spherical surface; represents the weight factor of the i-th point (0 < i < nn) on the error spherical surface corresponding to the localization results obtained by the a, b, c, d groups of sensors; represents the weight factor of the k-th group of localization results; the value range of k is r = 10 cm; nn = 10000..

[0044] S5 based on Based on the group positioning results and the positioning error weighting factor of each group positioning results, an optimization function for the local discharge source coordinates is established. By finding the optimal solution, the three-dimensional coordinates of the local discharge source inside the transformer in space are obtained.

[0045] Specifically, in step S5, the local discharge source optimization coordinate search function can be expressed as:

[0046]

[0047] Where n represents the number of ultra-high frequency sensors; α ii Indicates the group ii Weighting factors for localization results; (x k ,y k ,z k (x) represents the known positioning results of the k-th group of UHF sensors; s ,y s ,z s () represents the optimal coordinates of the local discharge source to be determined.

[0048] As an embodiment of the present invention, the local discharge source optimization coordinate search function can be optimized by particle swarm optimization algorithm.

[0049] In this embodiment of the invention, since the multiple positioning results obtained by the multi-group sensor positioning are not uniformly distributed around the actual positioning result, the time delay sensitivity of each positioning result is measured according to the magnitude of the time difference error on the positioning result error sphere, and an error weighting factor is defined accordingly. This reduces the dependence of the positioning result on the time delay accuracy and effectively improves the positioning accuracy of the partial discharge power source.

[0050] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for locating partial discharge using a multi-group ultra-high frequency sensor in a transformer, characterized in that, It includes the following steps: S1 Obtain the partial discharge signals collected by n ultra-high frequency sensors for a transformer with internal insulation defects at the same moment; where the value range of n is 4 < n ≤ 8; S2 For the ultra-high frequency signals collected by each ultra-high frequency sensor, calculate the time difference between the ultra-high frequency partial discharge signals received by every two ultra-high frequency sensors; S3 Arbitrarily select one of every four ultra-high frequency sensors as the reference sensor, establish a partial discharge source localization equation set based on the time differences of the ultra-high frequency signals generated by the partial discharge source propagating to the reference sensor and the other three sensors, and obtain the partial discharge source localization results of the grouped ultra-high frequency sensors by solving the partial discharge source localization equation set; S4 calculates the positioning error weighting factor for the k-th group based on the positioning results of that group; where the value of k ranges from... S5 Based on each group of localization results and the localization error weight factors of each group of localization results, establish an optimized coordinate search function for the partial discharge source, and obtain the three-dimensional coordinates of the internal partial discharge source of the transformer in space by finding the optimal solution.

2. The partial discharge localization method as described in claim 1, characterized in that, In step S2, the calculation method of the time difference between the ultra-high frequency signals propagating from the insulation defect in the transformer to any two ultra-high frequency sensors is as follows: (1) the time t corresponding to the maximum value of the ultra-high frequency signal collected by the ith ultra-high frequency sensor i the time when the ultra-high frequency signal generated during partial discharge propagates to the ith ultra-high frequency sensor (2) The time delay of the signals received by the i-th and j-th UHF sensors from the partial discharge power supply inside the transformer is expressed as Δt. ij =t i -t j Where 1≤i≤n, 1≤j≤n, i≠j, t i t j These represent the times when the ultra-high frequency signal generated during partial discharge propagates to the i-th and j-th ultra-high frequency sensors, respectively.

3. The partial discharge localization method as described in claim 1, characterized in that, In step S3, the localization equation set of the internal partial discharge source in the transformer is expressed as: Where (x,y,z) are the three-dimensional coordinates of the partial discharge source inside the transformer to be solved in space; t 1s Let x be the time it takes for the UHF signal to propagate from the partial discharge source to the reference sensor; i ,y i ,z i ) represents the known coordinates of the i-th UHF sensor; v represents the known propagation speed of UHF electromagnetic waves in transformer oil; Δt 12 , Δt 13 , Δt 14 These are the time delays of the signals received by the first and second, third, and fourth UHF sensors from the partial discharge power supply inside the transformer, respectively.

4. The partial discharge localization method as described in claim 1, characterized in that, In step S3, the solution of the localization equation set of the internal partial discharge source in the transformer is obtained by converting the solution problem of the equation set into an optimization problem as shown below and performing optimization search through the particle swarm algorithm; Where (x,y,z) are the three-dimensional coordinates of the partial discharge source inside the transformer to be solved in space; t 1s Let x be the time it takes for the UHF signal to propagate from the partial discharge source to the reference sensor; i ,y i ,z i ) represents the known coordinates of the i-th UHF sensor; v represents the known propagation speed of UHF electromagnetic waves in transformer oil; Δt 1i Let be the time delay of the signal received by the first and i-th UHF sensors from the partial discharge power supply inside the transformer.

5. The partial discharge localization method according to any one of claims 1-4, characterized in that, In step S5, the optimized coordinate search function for the partial discharge source is expressed as: Where n represents the number of ultra-high frequency sensors; α ii This represents the weighting factor for the location results of group ii. (x k ,y k ,z k (x) represents the positioning result of the UHF sensor in the k-th group; s ,y s ,z s () represents the optimal coordinates of the local discharge source to be determined.

6. The partial discharge localization method according to any one of claims 1 to 5, characterized in that, In step S4, taking the k-th positioning result obtained from the a, b, c, and d-th sensor groups as the center and an error sphere with radius r, a sufficient number of n random points are selected on the error sphere. For each point, the difference between the time difference at the random point and the measured time difference is calculated. The result for the i-th point is denoted as... The positioning error weighting factor for the i-th point can be expressed as: The weighting factor for the k-th location result can be expressed as: in This represents the time difference error between the a-th and b-th sensor groups at the ii-th point on the error sphere. These represent the weighting factors of the time difference error of the sensors in groups a and b, groups a and c, and groups a and d at the i-th point on the error sphere, respectively. This represents the weighting factor at the ii-th point on the error sphere corresponding to the positioning results obtained from the a, b, c, and d groups of sensors; This represents the weighting factor for the k-th location result; the value of k ranges from 1 to 2. 0 <ii<nn。 7. The partial discharge localization method as described in claim 6, characterized in that, The error spherical radius r is 10 cm; the random point nn is 10000.

8. The partial discharge localization method according to any one of claims 1-7, characterized in that, The bandwidth of the ultra-high frequency sensor is 300 MHz to 1.5 GHz; 4 < n ≤ 8; the ultra-high frequency signal acquisition device selects the Tektronix DPO7254C model oscilloscope, and the signal sampling rate is 20 GHz.

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