A hybrid line distance measurement method based on segmented Berelon model

Abstract

The present invention relates to the field of power transmission line protection technology, and in particular to a hybrid line distance measurement method based on a segmented Berelon model, including: obtaining three-phase voltage and current values ​​at a protection installation; calculating line mode high frequency components of multiple frequency bands of current traveling waves by using phase mode decomposition and wavelet decomposition; calculating the product results of line mode high frequency components under multiple frequency bands, and determining the peak sampling point number according to the peak position of the product result; preliminarily determining the fault section according to the length and wave velocity of overhead lines and cables in the hybrid line; based on the Berelon model of the non-fault section in the hybrid line, calculating the current at the intermediate hybrid point position, determining the sampling point number corresponding to the peak position of the high frequency product result of the current at the hybrid point position; determining the fault position according to the sampling point number corresponding to the peak position of the high frequency product result of the current at the hybrid point position and the protection installation near the fault point. The present invention effectively improves the accuracy and reliability of hybrid line fault distance measurement.

Description

Technical Field

[0001] The present invention relates to the technical field of power transmission line protection, and more particularly to a hybrid line distance measurement method based on a segmented Berelon model. Background Art

[0002] With the rapid development of offshore wind power and island economy, hybrid transmission lines of overhead lines and submarine cables have been widely used. More and more cross-river and cross-sea power transmission is carried out by laying power cables. In actual engineering applications, most of them use hybrid transmission lines of overhead lines and cables. When a cable fails, line inspection is very complicated and inspection and maintenance are difficult. If the fault distance measurement is inaccurate, it will seriously affect the power transmission work.

[0003] For hybrid line fault distance measurement, there are currently two main methods: impedance method and traveling wave method. Both methods have achieved good distance measurement results when applied to a single type of line. However, when applied to hybrid lines, the impedance method fault location method is no longer applicable due to the inconsistency of line parameters of overhead lines and cables. For hybrid line traveling wave distance measurement methods, the first wave head obtained at the distance measurement device is currently used to calculate the fault point location by wave impedance conversion and other methods. However, due to the large number of discontinuous points in the wave impedance of hybrid lines, the first wave head at the distance measurement device is severely distorted, resulting in low distance measurement accuracy. Therefore, an effective and high-precision traveling wave distance measurement method is urgently needed to achieve hybrid line fault distance measurement. Summary of the invention

[0004] In view of this, the present invention provides a hybrid line distance measurement method based on the segmented Berylon model, which effectively improves the accuracy and reliability of hybrid line fault distance measurement.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A hybrid line distance measurement method based on a segmented Berelon model comprises the following steps:

[0007] S1: Obtain the three-phase voltage and current values ​​at the protection installation location;

[0008] S2: Use phase mode decomposition and wavelet decomposition to calculate the line mode high frequency components of multiple frequency bands of the current traveling wave;

[0009] S3: Calculate the product results of the high-frequency components of the line modes in multiple frequency bands, and determine the peak sampling point number according to the peak position of the product result;

[0010] S4: Preliminarily determine the fault section based on the length and wave velocity of the overhead lines and cables in the hybrid line;

[0011] S5: Based on the Berelon model of the non-fault section in the hybrid line, the current at the intermediate hybrid point is estimated, and the sampling point number corresponding to the peak position of the high-frequency product result of the current at the hybrid point is determined;

[0012] S6: Determine the fault location based on the sampling point number corresponding to the peak position of the high-frequency product result of the mixed point location and the current near the fault point protection installation.

[0013] Furthermore, in S2, the calculation formulas for the line mode high frequency components of multiple frequency bands of the current traveling wave for the M-side protection and the N-side protection are the same, where the calculation formula for the M-side protection is:

[0014] Sagami decomposition: i M1 (n)=[i Ma (n)-i Mb (n)] / 3

[0015] Wavelet decomposition:

[0016] Where n is the current sampling point number; i Ma 、i Mb and i M1 are the A-phase current, B-phase current and line mode current of the M-side protection respectively; i MH1 、i MH2 and i MH3 They are the high-frequency components of the line mode current in the first frequency band, the second frequency band and the third frequency band, and their frequency bands are [f samp / 4,f samp / 2]、[f samp / 8,f samp / 4] and [f samp / 16,f samp / 8], where f samp is the sampling frequency; i ML1 and i ML2 They are the low-frequency components of the line mode current in the first and second frequency bands, and their frequency bands are [0,f samp / 4] and [0,f samp / 8]; P H and P L are the high-pass filter coefficient and low-pass filter coefficient of wavelet decomposition respectively; N H and N L are the length of the high-pass filter coefficient and the length of the low-pass filter coefficient respectively; k is the current filter coefficient point number.

[0017] Furthermore, the high-pass filter coefficient P of wavelet decomposition HSet to [-0.23040.7148-0.6309-0.02800.18700.0308-0.0329-0.0106], the low-pass filter coefficient P of wavelet decomposition L Set to [-0.01060.03290.0308-0.1870-0.02800.63090.71480.2304], filter coefficient length N H and N L Both are 8.

[0018] Furthermore, in S3, the product of the line mode high frequency components of multiple frequency bands is used as the line mode comprehensive component of the current traveling wave. The calculation formula of the line mode comprehensive component is:

[0019]

[0020] In the formula, i MH and i MHj are the line mode comprehensive component of the current traveling wave and the line mode high frequency component of the jth frequency band respectively; П is the standard symbol for the product of polynomials; N lv is the number of frequency bands for calculating the line mode synthesis component.

[0021] Furthermore, the number of frequency bands N of the line mode integrated component is calculated lv is 3.

[0022] Furthermore, in S4, the criterion for determining the fault section is:

[0023]

[0024] Where N Mmax and N Mmax are the sampling point numbers corresponding to the peak values ​​of the product of the high-frequency components of the line mode for the M-side protection and the N-side protection respectively; f samp is the sampling frequency; L c and L o are the lengths of cables and overhead lines in the hybrid line respectively; v c and v o are the wave velocities of cables and overhead lines in the hybrid line, and their values ​​are and L cab and C cab are the positive sequence inductance and positive sequence capacitance of the cable per unit length in the hybrid line; L ove and C ove The positive sequence inductance and positive sequence capacitance of the overhead line per unit length in the mixed line are respectively;

[0025] If the criterion is met, it is determined that the fault occurs in the cable section of the hybrid line; otherwise, it is determined that the fault occurs in the overhead line section of the hybrid line.

[0026] Furthermore, in S5, the expression of the Berelon model based on the non-fault section in the hybrid line is:

[0027]

[0028] Where n is the current sampling point number; i k is the estimated current at the mixing point; i M and u M are the current and voltage of the M side protection, i N and u N are the current and voltage of N-side protection respectively; τ k is the wave transmission delay of the non-fault section, which is the line length of the non-fault section / wave velocity, where the wave velocity is L and C represent the inductance and capacitance of the line in the non-fault section respectively; f samp is the sampling frequency; Z c is the wave impedance, and its value is

[0029] Furthermore, in S6, if the fault point is close to the M-side protection, the calculation formula for the fault position is:

[0030]

[0031] Where, L MF L is the distance between the fault point and the M side protection. MK N is the distance between the M side protection and the mixing point; Mmax N is the peak sampling point number of the wave head for protection on the M side, Kmax is the wave head peak sampling point number at the mixing point; v is the wave velocity; f samp is the sampling frequency;

[0032] If the fault point is close to the N-side protection, the calculation formula for the fault position is:

[0033]

[0034] Where, L NF L is the distance between the fault point and the N-side protection. NK N is the distance between the N-side protection and the mixing point; Nmax N is the peak sampling point number of the wave head for protection on the N side. Kmax It is the sampling point number of the wave head peak at the mixing point.

[0035] It can be seen from the above technical solutions that, compared with the prior art, the present invention has the following beneficial effects:

[0036] The present invention utilizes the segmented Berelon model of the line and realizes the decoupling of the overhead line and the cable by calculating the current at the intermediate mixing point, simplifies the complex hybrid line distance measurement into a single line distance measurement, and effectively improves the accuracy and reliability of hybrid line fault distance measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0038] Figure 1 A schematic diagram of the structure of the hybrid circuit provided by the present invention;

[0039] Figure 2 A flow chart of a hybrid line distance measurement method based on a segmented Berelon model provided by the present invention. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] like Figure 1 As shown, it is a schematic diagram of a hybrid line, where S1 and S2 represent M-side protection and N-side protection respectively, MK is the overhead line, HK is the cable, and F1 represents the fault point location.

[0042] like Figure 2 As shown, the embodiment of the present invention discloses a hybrid line distance measurement method based on a segmented Berelon model, comprising the following steps:

[0043] S1: Obtain the three-phase voltage and current values ​​at the protection installation location;

[0044] S2: Use phase mode decomposition and wavelet decomposition to calculate the line mode high frequency components of multiple frequency bands of the current traveling wave;

[0045] S3: Calculate the product results of the high-frequency components of the line modes in multiple frequency bands, and determine the peak sampling point number according to the peak position of the product result;

[0046] S4: Preliminarily determine the fault section based on the length and wave velocity of the overhead lines and cables in the hybrid line;

[0047] S5: Based on the Berelon model of the non-fault section in the hybrid line, the current at the intermediate hybrid point is estimated, and the sampling point number corresponding to the peak position of the high-frequency product result of the current at the hybrid point is determined;

[0048] S6: Determine the fault location based on the sampling point number corresponding to the peak position of the high-frequency product result of the mixed point location and the current near the fault point protection installation.

[0049] The above steps are further explained below.

[0050] S1. Obtain the three-phase voltage and current values ​​at the protection installation location.

[0051] S2. Use phase mode decomposition and wavelet decomposition to calculate the line mode high frequency components of multiple frequency bands of the current traveling wave. The calculation formulas for the line mode high frequency components of multiple frequency bands of the current traveling wave for M-side protection and N-side protection are the same. Taking the phase mode decomposition and wavelet decomposition process of the M-side protection as an example, the calculation formula for the line mode high frequency components of multiple frequency bands of the current traveling wave is:

[0052] Sagami decomposition: i M1 (n)=[i Ma (n)-i Mb (n)] / 3

[0053] Wavelet decomposition:

[0054] Where n is the current sampling point number; i Ma 、i Mb and i M1 are the A-phase current, B-phase current and line mode current of the M-side protection respectively; i MH1 、i MH2 and i MH3 They are the high-frequency components of the line mode current in the first frequency band, the second frequency band and the third frequency band, and their frequency bands are [f samp / 4,f samp / 2]、[f samp / 8,f samp / 4] and [f samp / 16,f samp / 8], where f samp is the sampling frequency; i ML1 and i ML2 They are the low-frequency components of the line mode current in the first and second frequency bands, and their frequency bands are [0,f samp / 4] and [0,f samp / 8]; P H and P L are the high-pass filter coefficient and low-pass filter coefficient of wavelet decomposition respectively; N H and N Lare the length of the high-pass filter coefficient and the length of the low-pass filter coefficient respectively; k is the current filter coefficient point number.

[0055] Among them, the high-pass filter coefficient P of wavelet decomposition H Set to [-0.23040.7148-0.6309-0.02800.18700.0308-0.0329-0.0106], the low-pass filter coefficient P of wavelet decomposition L Set to [-0.01060.03290.0308-0.1870-0.02800.63090.71480.2304], filter coefficient length N H and N L Both are 8.

[0056] S3: Calculate the product results of the high-frequency components of the line modes in multiple frequency bands, and determine the peak sampling point number according to the peak position of the product result, so as to comprehensively utilize the multi-band information and reduce noise interference.

[0057] The product of the line mode high frequency components of multiple frequency bands is taken as the line mode comprehensive component of the current traveling wave. The calculation formula of the line mode comprehensive component is:

[0058]

[0059] In the formula, i MH and i MHj are the line mode comprehensive component of the current traveling wave and the line mode high frequency component of the jth frequency band respectively; П is the standard symbol for the product of polynomials; N lv is the number of frequency bands for calculating the line mode integrated component. In this embodiment, the number of frequency bands N for calculating the line mode integrated component is lv is 3.

[0060] S4 preliminarily determines the fault section based on the length and wave velocity of the overhead lines and cables in the hybrid line. The criteria for determining the fault section are:

[0061]

[0062] Where N Mmax and N Mmax are the sampling point numbers corresponding to the peak values ​​of the product of the high-frequency components of the line mode for the M-side protection and the N-side protection respectively; f samp is the sampling frequency; L c and L o are the lengths of cables and overhead lines in the hybrid line respectively; v c and v o are the wave velocities of cables and overhead lines in the hybrid line, and their values ​​are and L cab and C cabare the positive sequence inductance and positive sequence capacitance of the cable per unit length in the hybrid line; L ove and C ove The positive sequence inductance and positive sequence capacitance of the overhead line per unit length in the mixed line are respectively;

[0063] If the criterion is met, it is determined that the fault occurs in the cable section of the hybrid line; otherwise, it is determined that the fault occurs in the overhead line section of the hybrid line.

[0064] S5 constructs the Berelon model of the non-fault section in the hybrid line. The calculation formula for calculating the current at the intermediate hybrid point using the Berelon model is:

[0065]

[0066] Where n is the current sampling point number; i k is the estimated current at the mixing point; i M and u M are the current and voltage of the M side protection, i N and u N are the current and voltage of N-side protection respectively; τ k is the wave transmission delay of the non-fault section, which is the line length of the non-fault section / wave velocity, where the wave velocity is L and C represent the inductance and capacitance of the line in the non-fault section respectively; f samp is the sampling frequency; Z c is the wave impedance, and its value is

[0067] Afterwards, similar to S3, the product result of the line mode high frequency components in multiple frequency bands at the mixing point position is calculated, and the peak sampling point number is determined according to the peak position of the product result.

[0068] S6 determines the fault location based on the sampling point number corresponding to the peak position of the high-frequency product result of the current at the hybrid point location and the protection installation near the fault point. If the fault point location is close to the M side protection, the calculation formula for the fault location is:

[0069]

[0070] Where, L MF L is the distance between the fault point and the M side protection. MK N is the distance between the M side protection and the mixing point; Mmax N is the peak sampling point number of the wave head for protection on the M side, Kmax is the wave head peak sampling point number at the mixing point; v is the wave velocity, and its value is Where L and C represent the positive sequence inductance and positive sequence capacitance of the line per unit length respectively; f samp is the sampling frequency;

[0071] If the fault point is close to the N-side protection, the calculation formula for the fault position is:

[0072]

[0073] Where, L NF L is the distance between the fault point and the N-side protection. NK N is the distance between the N-side protection and the mixing point; Nmax N is the peak sampling point number of the wave head for protection on the N side. Kmax It is the sampling point number of the wave head peak at the mixing point.

[0074] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0075] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A hybrid line distance measurement method based on a segmented Berelon model, characterized in that: The following steps are involved: S1: Obtain the three-phase voltage and current values ​​at the protection installation location; S2: Use phase mode decomposition and wavelet decomposition to calculate the line mode high frequency components of multiple frequency bands of the current traveling wave; S3: Calculate the product results of the high-frequency components of the line modes in multiple frequency bands, and determine the peak sampling point number according to the peak position of the product result; S4: Preliminarily determine the fault section based on the length and wave velocity of the overhead lines and cables in the hybrid line; S5: Based on the Berelon model of the non-fault section in the hybrid line, the current at the intermediate hybrid point is estimated, and the sampling point number corresponding to the peak position of the high-frequency product result of the current at the hybrid point is determined; the expression of the Berelon model based on the non-fault section in the hybrid line is: Where n is the current sampling point number; i k is the estimated current at the mixing point; i M and u M are the current and voltage of the M side protection, i N and u N are the current and voltage of N-side protection respectively; τ k is the wave transmission delay of the non-fault section, which is the line length of the non-fault section / wave velocity, where the wave velocity is L and C represent the inductance and capacitance of the line in the non-fault section respectively; f samp is the sampling frequency; Z c is the wave impedance, and its value is S6: Determine the fault location based on the sampling point number corresponding to the peak position of the high-frequency product result of the mixed point location and the current near the fault point protection installation.

2. The hybrid line distance measurement method based on the segmented Berelon model according to claim 1, characterized in that: In S2, the calculation formulas for the line mode high frequency components of multiple frequency bands of the current traveling wave are the same for the M-side protection and the N-side protection, where the calculation formula for the M-side protection is: Sagami decomposition: i M1 (n) = [i Ma (n)-i Mb (n)] / 3 Wavelet decomposition: Where n is the current sampling point number; i Ma 、i Mb and i M1 are the A-phase current, B-phase current and line mode current of the M-side protection respectively; i MH1 、i MH2 and i MH3 They are the high-frequency components of the line mode current in the first frequency band, the second frequency band and the third frequency band, and their frequency bands are [f samp / 4,f samp / 2]、[f samp / 8,f samp / 4] and [f samp / 16,f samp / 8], where f samp is the sampling frequency; i ML1 and i ML2 They are the low-frequency components of the line mode current in the first and second frequency bands, and their frequency bands are [0,f samp / 4] and [0,f samp / 8]; P H and P L are the high-pass filter coefficient and low-pass filter coefficient of wavelet decomposition respectively; N H and N L are the length of the high-pass filter coefficient and the length of the low-pass filter coefficient respectively; k is the current filter coefficient point number.

3. The hybrid line distance measurement method based on the segmented Berelon model according to claim 2, characterized in that: High-pass filter coefficient P of wavelet decomposition H Set to [-0.23040.7148-0.6309-0.02800.18700.0308-0.0329-0.0106], the low-pass filter coefficient P of wavelet decomposition L Set to [-0.01060.03290.0308-0.1870-0.02800.63090.71480.2304], filter coefficient length N H and N L Both are 8.

4. The hybrid line distance measurement method based on the segmented Berelon model according to claim 1, characterized in that: In S3, the product of the line mode high frequency components of multiple frequency bands is used as the line mode comprehensive component of the current traveling wave. The calculation formula of the line mode comprehensive component is: In the formula, i MH and i MHj are the line mode comprehensive component of the current traveling wave and the line mode high frequency component of the jth frequency band respectively; П is the standard symbol for the product of polynomials; N lv is the number of frequency bands for calculating the line mode synthesis component.

5. The hybrid line distance measurement method based on the segmented Berelon model according to claim 4, characterized in that: Calculate the number of frequency bands N for the line mode composite component lv is 3.

6. The hybrid line distance measurement method based on the segmented Berelon model according to claim 1, characterized in that: In S4, the criterion for determining the fault section is: Where N Mmax and N Mmax are the sampling point numbers corresponding to the peak values ​​of the product of the high-frequency components of the line mode for the M-side protection and the N-side protection respectively; f samp is the sampling frequency; L c and L o are the lengths of cables and overhead lines in the hybrid line respectively; v c and v o are the wave velocities of cables and overhead lines in the hybrid line, and their values ​​are and L cab and C cab are the positive sequence inductance and positive sequence capacitance of the cable per unit length in the hybrid line; L ove and C ove The positive sequence inductance and positive sequence capacitance of the overhead line per unit length in the mixed line are respectively; If the criterion is met, it is determined that the fault occurs in the cable section of the hybrid line; otherwise, it is determined that the fault occurs in the overhead line section of the hybrid line.

7. The hybrid line distance measurement method based on the segmented Berelon model according to claim 1, characterized in that: In S6, if the fault point is close to the M-side protection, the calculation formula for the fault position is: Where, L MF L is the distance between the fault point and the M side protection. MK N is the distance between the M side protection and the mixing point; Mmax N is the peak sampling point number of the wave head for protection on the M side, Kmax is the wave head peak sampling point number at the mixing point; v is the wave velocity; f samp is the sampling frequency; If the fault point is close to the N-side protection, the calculation formula for the fault position is: Where, L NF L is the distance between the fault point and the N-side protection. NK N is the distance between the N-side protection and the mixing point; Nmax N is the peak sampling point number of the wave head for protection on the N side. Kmax It is the sampling point number of the wave head peak at the mixing point.

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