Partial discharge positioning error compensation device and method suitable for open substation

Abstract

The present invention relates to a local discharge positioning error compensation device and method suitable for open substations, the device includes two ultra-high frequency antennas, a three-dimensional electronic compass, a signal conditioning module, a signal acquisition module and an analysis terminal; the method includes: establishing a local discharge positioning mathematical model according to the size and sampling rate of the two ultra-high frequency antennas; establishing multiple groups of error distribution models based on sampling errors; performing local discharge detection to obtain the deflection angle of the antenna array; establishing an error equation group; solving the equation group according to the error weights corresponding to different angles to obtain the accurate local discharge source azimuth. The present invention uses a dual antenna array to quantitatively analyze the local discharge azimuth positioning error, obtains the positioning azimuth error caused by the quantized time delay error, and uses the quantized error to compensate for the azimuth error, effectively improving the accuracy of local discharge positioning without increasing the complexity of the hardware system.

Description

Technical Field

[0001] The invention belongs to the technical field of high-voltage electrical equipment, and relates to insulation state detection of high-voltage electrical equipment, in particular to a local discharge positioning error compensation device and method suitable for an open-type substation. Background Art

[0002] In the insulation state detection technology of high-voltage electrical equipment, the UHF method is a common method for locating partial discharge in open substations. Its specific implementation method is: four omnidirectional antennas are used to build an antenna array, and the time difference between the UHF signals detected by the four omnidirectional antennas is used to establish the following three equations, and the equations are solved to obtain the coordinates of the partial discharge source:

[0003]

[0004] Where (x1, y1, z1), (x2, y2, z2), (x3, y3, z3), (x4, y4, z4), (xp, yp, zp) are the coordinates of the four antennas and the PD source respectively, Δt 2-1 , Δt 3-1 , Δt 4-1 They are the time delays of #2, #3, #4 antennas and #1 antenna receiving UHF signals, and c is the propagation speed of electromagnetic waves in the air.

[0005] Theoretically, the coordinates (xp, yp, zp) of the local discharge source can be obtained by solving equation group (1). However, in practical applications, due to the discrete value of the time difference, the size deviation of the antenna array and the fact that equation (1) is a nonlinear equation group, its solution method is generally more complicated. The accuracy of the calculation result of equation group (1) depends on Δt 2-1 , Δt 3-1 , Δt 4-1 The accuracy of the three time differences, when there are errors in the three time differences, there is no solution to the equation group (1), that is, it is impossible to obtain accurate results. The error comes from two aspects. First, the signal-to-noise ratio of the partial discharge UHF signal is low, resulting in errors in the time difference calculation; second, the obtained partial discharge UHF signal is a discrete signal, the time difference is a discrete value, and the minimum resolution is the sampling rate of the signal. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a local discharge positioning error compensation device and method suitable for an open substation, which can effectively improve the accuracy of local discharge source azimuth measurement.

[0007] The present invention solves the existing technical problems by adopting the following technical solutions:

[0008] A local discharge positioning error compensation device suitable for an open substation comprises two ultra-high frequency antennas, a three-dimensional electronic compass, a signal conditioning module, a signal acquisition module and an analysis terminal; the two ultra-high frequency antennas are arranged at intervals to respectively collect ultra-high frequency signals of local discharge; the three-dimensional electronic compass is installed between the two ultra-high frequency antennas to measure the azimuth of the antenna array; the signal conditioning module is connected to the two ultra-high frequency antennas to realize the amplification function of the ultra-high frequency signal of local discharge; the signal acquisition module is connected to the signal conditioning module to sample the ultra-high frequency signal; the analysis terminal is connected to the signal acquisition module and the three-dimensional electronic compass to realize the time delay calculation and error compensation calculation functions of the two-way signal.

[0009] Moreover, the two UHF antennas are installed at two ends of the antenna connecting rod, and the three-dimensional electronic compass is installed in the middle position of the antenna connecting rod.

[0010] Moreover, the horizontal 0° direction of the three-dimensional electronic compass is perpendicular to the directions of the two UHF antennas.

[0011] Moreover, the sampling rate of the signal acquisition module is not less than 10GS / s.

[0012] A method for compensating a partial discharge positioning error of an open substation, comprising the following steps:

[0013] Step 1: Establish a mathematical model for PD location based on the size and sampling rate of the two UHF antennas to calculate the apparent azimuth angle θ of the PD source. app ;

[0014] Step 2: Perform error analysis on the partial discharge location mathematical model based on the sensitivity analysis method, and establish multiple groups of error distribution models based on sampling errors;

[0015] Step 3: Perform partial discharge detection, obtain two UHF signals, calculate the time delay and phase angle, and obtain the deflection angle of the antenna array;

[0016] Step 4: Repeat step 3 to establish the error equation group;

[0017] Step 5: Solve the equations according to the error weights corresponding to different angles to obtain the accurate azimuth of the local discharge source.

[0018] Moreover, the specific implementation method of step 1 is: take the center point of the two UHF antennas as the coordinate origin, and record the distance of each antenna from the origin as r, then the apparent azimuth angle θ of the local discharge source in the two-dimensional plane app Calculated by the following formula:

[0019]

[0020] Where Δt is the time delay of the two UHF signals, and c is the sampling rate of the signal acquisition module.

[0021] Moreover, the specific implementation method of step 2 is:

[0022] Assume that the linear, time-invariant system transfer function is T(s) = R(s) / E(s), where R(s) is the system output function, E(s) is the system input function, and x is a parameter of a certain link in the system; when x changes slightly, the change in the system output is expressed as follows:

[0023]

[0024]

[0025] Where dx is the change in x, and dR(s) is the change in output; is the normalized sensitivity of the system to parameter x;

[0026] The apparent azimuth angle θ app As the system output, with the time delay Δt as the system parameter, the error distribution model that changes with the time delay error dΔt is established:

[0027]

[0028] Where Δt is the time delay of the two UHF signals, c is the sampling rate of the signal acquisition module, r is the distance between each antenna and the center point, and dθ app |Δt is the theoretical error value of the apparent azimuth angle obtained when the delay is Δt and an error of dΔt occurs.

[0029] Moreover, the specific implementation method of step 3 includes the following steps:

[0030] (1) Detection signal: obtain two UHF signals s1(n) and s2(n) through two UHF antennas, and obtain the deflection angle α of the antenna array corresponding to the group of signals. The deflection angle is the angle with the true north direction obtained by the three-dimensional electronic compass;

[0031] (2) Delay calculation: calculate the delay Δt of the two UHF signals s1(n) and s2(n);

[0032] ⑶ Calculate the azimuth angle: Calculate the azimuth angle θ of the local discharge source based on the time delay Δt app .

[0033] Moreover, the error equations established in step 4 include the following parameters: the azimuth angle θ of the local discharge source app (i), time delay Δt(i) and the deflection angle α(i) of the antenna array.

[0034] Moreover, the specific implementation method of step 5 includes the following steps:

[0035] ⑴Construct error analysis model: According to the azimuth angle θ of the local discharge source obtained in step 4 app (i), time delay Δt(i) and deflection angle α(i) of the antenna array to establish the following error analysis model:

[0036] γ'=90+α(i)-θ app (i) = γ + g(dΔt)

[0037] Where, γ is the true azimuth of the local discharge source, γ' is the calculated error azimuth, and g(dΔt) is the azimuth error introduced by the time delay error dΔt;

[0038] (2) Construct the error azimuth matrix γ': According to step (1), I*(2K+2) error azimuths γ' are calculated, where I is the number of detections. An error azimuth matrix with I columns and 2K+2 rows is established, and the row vectors of the matrix are arranged in the order of increasing absolute value of the delay error |dΔt|;

[0039] ⑶ Minimum error optimization: Calculate the root mean square error value between each element in column I and each element in the remaining columns in turn, and obtain a total of (2K+2)×(I-1) root mean square error values. Record the row number of the error azimuth matrix corresponding to each root mean square error value, count the row number of the error azimuth matrix element corresponding to the minimum root mean square error, extract the corresponding error azimuth, calculate the average value, and obtain the azimuth after error compensation.

[0040] The advantages and positive effects of the present invention are:

[0041] The present invention is reasonably designed. It adopts a dual antenna array to quantitatively analyze the local discharge azimuth positioning error, obtains the positioning azimuth error caused by the quantized time delay error, and uses the quantized error to compensate for the azimuth error, thereby effectively improving the accuracy of local discharge positioning without increasing the complexity of the hardware system. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a structural diagram of a partial discharge positioning error compensation device using a dual antenna array according to the present invention;

[0043] Figure 2 is a flow chart of the error compensation method of the present invention;

[0044] Figure 3a A time domain waveform diagram of a first group of signals detected on-site according to an embodiment of the present invention;

[0045] Figure 3b A time domain waveform diagram of a second group of signals detected on-site according to an embodiment of the present invention;

[0046] Figure 3c A time domain waveform diagram of the third group of signals detected on-site according to an embodiment of the present invention;

[0047] Figure 4 This is the azimuth error distribution of different delay errors under the conditions of f=10GS / s and r=1m. DETAILED DESCRIPTION

[0048] The embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0049] A partial discharge positioning error compensation device suitable for open substations, such as Figure 1 As shown, it includes two UHF antennas, a three-dimensional electronic compass, a signal conditioning module, a signal acquisition module and an analysis terminal. The two UHF antennas are installed at both ends of the antenna connecting rod to respectively collect the local discharge UHF signals. The three-dimensional electronic compass is installed in the middle position of the antenna connecting rod to realize the measurement of the azimuth of the antenna array. When installing, the horizontal 0° direction of the three-dimensional electronic compass is set to be perpendicular to the direction of the antenna array. The signal conditioning module is connected to the two UHF antennas to realize the amplification function of the local discharge UHF signal, and the bandwidth covers 500MHz-1.5GHz, and the gain is greater than 20dB. The signal acquisition module is connected to the signal conditioning module for sampling the UHF signal, and its sampling rate is not less than 10GS / s. The analysis terminal is connected to the signal acquisition module and the three-dimensional electronic compass to realize the delay calculation of the two-way signal and the subsequent error compensation method function.

[0050] Based on the above-mentioned local discharge positioning error compensation device adapted to open substations, the present invention also proposes an error compensation method adapted to local discharge positioning of open substations, such as Figure 2 As shown, the following steps are included:

[0051] Step 1 (S1): A partial discharge location mathematical model is established according to the sizes of two UHF antennas and the sampling rate of a signal sampling module.

[0052] In this step, the center points of the two antennas are taken as the coordinate origin, and the distance between each antenna and the origin is recorded as r. Then, the apparent azimuth angle of the local discharge source in the two-dimensional plane can be calculated by formula (2).

[0053]

[0054] Step 2 (S2): Based on the sensitivity analysis method, error analysis is performed on the partial discharge location mathematical model, and multiple groups of error distribution models based on sampling errors are established.

[0055] In this step, the sensitivity analysis method is used to perform quantitative calculation of the adopted error. Sensitivity analysis is a method to study the sensitivity of a system state or output change to changes in system parameters or surrounding conditions. Assume that the transfer function of a linear, time-invariant system is T(s) = R(s) / E(s), where R(s) is the system output function, E(s) is the system input function, and x is a parameter of a certain link in the system. When x changes slightly, the change in the system output can be expressed as shown in formula (3), where dx is the change in x and dR(s) is the change in output. is the normalized sensitivity of the system to parameter x, and the calculation method is shown in formula (4).

[0056]

[0057]

[0058] The apparent azimuth angle θ app As the system output, with the delay Δt as the system parameter, the error distribution model that changes with the delay error dΔt is established according to formula (3), as shown in formula (5). app |Δt is the theoretical error value of the apparent azimuth angle when the delay is Δt and an error of dΔt occurs. A series of error distribution models are established according to the sampling rate of the signal acquisition module. When the signal sampling rate is fGS / s, the delay resolution is 1 / fs, and the theoretical minimum delay error is 1 / 2fs. Let dΔt = ±1 / 2fs, ±1 / fs, ±2 / fs, ±3 / fs, ....., ±k / fs, ....., ±K / fs as the delay error, establish a series of error distribution models, and select 1+K groups of delay errors from small to large according to the actual situation to establish the corresponding 2+2K azimuth error distribution models.

[0059]

[0060] Step 3 (S3): Perform partial discharge detection, obtain two UHF signals, calculate the time delay and phase angle, and obtain the deflection angle of the antenna array.

[0061] This step is used to obtain raw data and calculate the deflection angle of the antenna array. The specific method is as follows:

[0062] Step 301 (S301): Detection signal: Use Figure 1 The local discharge positioning error compensation device for an open substation shown in the figure is tested on site in the substation to obtain two UHF signals s1(n) and s2(n) received by two antennas, and at the same time obtains the deflection angle α of the antenna array corresponding to the group of signals, which is the angle with the true north direction obtained by a three-dimensional electronic compass.

[0063] Step 302 (S302): Delay calculation: Calculate the delay of signals s1(n) and s2(n) using the minimum energy accumulation algorithm (since there are many types of delay calculation methods, other methods can also be used for calculation). Calculate the minimum cumulative energy curves of signals s1(n) and s2(n) respectively according to equations (6) and (7), where N is the number of sampling points of the signal, obtain the sampling point numbers χ1 and χ2 corresponding to the minimum value of the minimum energy accumulation curve, and the delay Δt is the difference between χ1 and χ2.

[0064]

[0065]

[0066] Step 303 (S303): Calculate the azimuth angle: Calculate the azimuth angle θ of the local discharge source using the time delay Δt obtained in S302 and equation (3) app .

[0067] Step 4 (S4): Repeat S3 to establish the error equation group.

[0068] In this step, S3 is repeatedly executed to obtain multiple groups of time delays Δt(i), θ app (i) and the corresponding antenna array deflection angle α(i), where i is the number of repetitions, i>2.

[0069] Step 5 (S5): Solve the equation group according to the error weights corresponding to different angles to obtain the accurate azimuth of the local discharge source.

[0070] This step realizes the error compensation function of the partial discharge source azimuth, and its specific implementation method is:

[0071] Step 501 (S501): Construct an error analysis model: Use the θ obtained in step 4 app (i), Δt(i) and α(i) are equal according to equation (8), where γ is the true azimuth of the local discharge source, γ' is the calculated error azimuth, and g(dΔt) is the azimuth error introduced by the time delay error dΔt. The calculation method is to substitute the Δt obtained in step 3 into one of the error models in equation (5) to obtain the result.

[0072] γ'=90+α(i)-θ app (i) = γ + g(dΔt) (8)

[0073] Step 502 (S502): Construct an error azimuth matrix γ': After calculation in step 501, I*(2K+2) error azimuths γ' are obtained, where I is the number of detections. An error azimuth matrix with I columns and (2K+2) rows is established, and the row vectors of the matrix are arranged in the order of increasing absolute values ​​of the delay errors |dΔt|.

[0074] Step 503 (S503): Minimum error search: Calculate the root mean square error value between each element of this column and each element of the remaining columns in turn, and obtain a total of (2K+2)(I-1) root mean square error values, record the row number of the error azimuth matrix corresponding to each root mean square error value, count the row number of the error azimuth matrix element corresponding to the minimum root mean square error, extract the corresponding error azimuth, and calculate the average value, which is the azimuth after error compensation.

[0075] A specific example is given below to verify the effect of the present invention:

[0076] If the sampling rate of the signal acquisition module is set to 10GS / s, the delay resolution between array signals is 100ns, and the theoretical minimum delay deviation is 50ps. The distance between antenna A and antenna B is 2m, then r = 1m. The propagation speed of electromagnetic waves in the air is about 3*10 8 m / s. Three groups of signals are detected at a certain site, such as Figure 3a , Figure 3b and Figure 3c After calculation, the delays of the three groups of signals are 1.4ns, 0.8ns and 3.5ns respectively, and the corresponding azimuth angles and measured deflection angles are shown in Table 1.

[0077] Table 1 Calculation results of delay, calculated azimuth, deflection angle and error azimuth

[0078] According to formula (5), the error distribution model is established, as shown in formula (9). According to the error of delay calculation, eight theoretical delay errors of dΔt = ±50ps, ±100ps, ±200ps, and ±300ps are taken to establish the error distribution model, as shown in Figure 4 As shown. The three groups of time delays are substituted into the eight models to calculate the azimuth error, as shown in Table 2. Subtract the γ' in Table 1 from the data in Table 2 to obtain the error azimuth matrix γ', as shown in formula (10). According to S503, the error is optimized and calculated, and the minimum root mean square error is 0.131. The row numbers of the corresponding three columns are 7, 5, and 1, respectively, and the values ​​of the corresponding error azimuth matrix are 32.0705°, 31.886°, and 31.9925 degrees, respectively. The azimuth after error compensation is 31.983 degrees.

[0079]

[0080]

[0081] Table 2 Error values ​​of azimuth under different delay errors

[0082]

[0083] It can be seen from the above experiments that the accuracy of the partial discharge source azimuth angle measurement can be greatly improved after the partial discharge positioning error compensation of the present invention is adopted.

[0084] It should be emphasized that the embodiments described in the present invention are illustrative rather than restrictive. Therefore, the present invention includes but is not limited to the embodiments described in the specific implementation manner. Any other implementation manners derived by those skilled in the art based on the technical solution of the present invention also fall within the scope of protection of the present invention.

Claims

1. An error compensation method for a local discharge positioning error compensation device for an open substation, the local discharge positioning error compensation device for an open substation comprising two ultra-high frequency antennas, a three-dimensional electronic compass, a signal conditioning module, a signal acquisition module and an analysis terminal; the two ultra-high frequency antennas are arranged at intervals to respectively collect ultra-high frequency signals of local discharge; the three-dimensional electronic compass is installed between the two ultra-high frequency antennas to measure the azimuth of the antenna array; the signal conditioning module is connected to the two ultra-high frequency antennas to realize the amplification function of the ultra-high frequency signal of local discharge; the signal acquisition module is connected to the signal conditioning module for sampling the ultra-high frequency signal; the analysis terminal is connected to the signal acquisition module and the three-dimensional electronic compass to realize the time delay calculation and error compensation calculation function of the two-way signal, characterized in that: The compensation method comprises the following steps: Step 1: Establish a mathematical model for PD location based on the size and sampling rate of the two UHF antennas to calculate the apparent azimuth angle θ of the PD source. app ; Step 2: Perform error analysis on the partial discharge location mathematical model based on the sensitivity analysis method, and establish multiple groups of error distribution models based on sampling errors; Step 3: Perform partial discharge detection, obtain two UHF signals, calculate the time delay and phase angle, and obtain the deflection angle of the antenna array; Step 4: Repeat step 3 to establish the error equation group; Step 5: Solve the equations according to the error weights corresponding to different angles to obtain the accurate azimuth of the local discharge source; The specific implementation method of step 2 is: Assume that the linear, time-invariant system transfer function is T(s) = R(s) / E(s), where R(s) is the system output function, E(s) is the system input function, and x is a parameter of a certain link in the system; when x changes slightly, the change in the system output is expressed as follows: Where dx is the change in x, and dR(s) is the change in output; is the normalized sensitivity of the system to parameter x; The apparent azimuth angle θ app As the system output, with the time delay Δt as the system parameter, the error distribution model that changes with the time delay error dΔt is established: In the formula, Δt is the time delay of the two UHF signals, c is the sampling rate of the signal acquisition module, r is the distance between each antenna and the center point, and dθ app |Δt is the theoretical error value of the apparent azimuth angle obtained when the delay is Δt and an error of dΔt occurs.

2. The error compensation method of the partial discharge positioning error compensation device adapted to the open type substation according to claim 1 is characterized in that: The specific implementation method of step 1 is: take the center point of the two UHF antennas as the coordinate origin, and record the distance of each antenna from the origin as r, then the apparent azimuth angle θ of the local discharge source in the two-dimensional plane is app Calculated by the following formula: Where Δt is the time delay of the two UHF signals, and c is the sampling rate of the signal acquisition module.

3. The error compensation method of the partial discharge positioning error compensation device adapted to the open type substation according to claim 1 is characterized in that: The specific implementation method of step 3 includes the following steps: (1) Detection signal: obtain two UHF signals s1(n) and s2(n) through two UHF antennas, and obtain the deflection angle α of the antenna array corresponding to the group of signals. The deflection angle is the angle with the true north direction obtained by the three-dimensional electronic compass; (2) Delay calculation: calculate the delay Δt of the two UHF signals s1(n) and s2(n); ⑶ Calculate the azimuth angle: Calculate the azimuth angle θ of the local discharge source based on the time delay Δt app .

4. The error compensation method of the partial discharge positioning error compensation device adapted to the open type substation according to claim 1 is characterized in that: The error equations established in step 4 include the following parameters: the azimuth angle θ of the local discharge source app (i), time delay Δt(i) and the deflection angle α(i) of the antenna array.

5. The error compensation method for the partial discharge positioning error compensation device of an open type substation according to claim 1 is characterized in that: The specific implementation method of step 5 includes the following steps: ⑴Construct error analysis model: According to the azimuth angle θ of the local discharge source obtained in step 4 app (i), time delay Δt(i) and deflection angle α(i) of the antenna array to establish the following error analysis model: γ'=90+α(i)-θ app (i)=γ+g(dΔt) Where, γ is the true azimuth of the local discharge source, γ' is the calculated error azimuth, and g(dΔt) is the azimuth error introduced by the time delay error dΔt; (2) Construct the error azimuth matrix γ': According to step (1), I*(2K+2) error azimuths γ' are calculated, where I is the number of detections. An error azimuth matrix with I columns and 2K+2 rows is established, and the row vectors of the matrix are arranged in the order of increasing absolute value of the delay error |dΔt|; ⑶ Minimum error optimization: Calculate the root mean square error value between each element in column I and each element in the remaining columns in turn, and obtain a total of (2K+2)×(I-1) root mean square error values. Record the row number of the error azimuth matrix corresponding to each root mean square error value, count the row number of the error azimuth matrix element corresponding to the minimum root mean square error, extract the corresponding error azimuth, calculate the average value, and obtain the azimuth after error compensation.

6. The error compensation method for the partial discharge positioning error compensation device of an open type substation according to claim 1 is characterized in that: The two UHF antennas are installed at two ends of the antenna connecting rod, and the three-dimensional electronic compass is installed in the middle of the antenna connecting rod.

7. The error compensation method for the partial discharge positioning error compensation device of an open type substation according to claim 1 is characterized in that: The horizontal 0° direction of the three-dimensional electronic compass is perpendicular to the directions of the two UHF antennas.

8. The error compensation method for the partial discharge positioning error compensation device of an open type substation according to claim 1 is characterized in that: The sampling rate of the signal acquisition module is not less than 10GS / s.

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