A fusion ranging method based on multi-band identification

Abstract

The present invention relates to the field of power transmission line protection technology, and specifically to a fusion ranging method based on multi-band identification, including: obtaining three-phase voltage and current values ​​at the protection installation; determining the power frequency fault point location using the power frequency impedance method; calculating the line mode high and low frequency components of the current traveling wave and the line mode low frequency components of the voltage traveling wave; finding the peak values ​​of the current line mode high frequency components of the protection on both sides, and detecting whether there are other peak values ​​greater than the threshold to the forward patrol point; comparing the peak values ​​corresponding to the initial traveling wave sampling point numbers of the protection on both sides, and detecting the initial traveling wave on the side with a smaller peak value within the setting time window corresponding to the power frequency fault point location; verifying the validity of the initial traveling wave according to the polarity criterion and the peak-to-peak ratio criterion; determining the fault location according to the initial traveling wave sampling point number of the bilateral protection. The present invention combines a variety of abnormal wave detection methods to effectively improve the reliability of traveling wave ranging.

Description

Technical Field

[0001] The present invention relates to the technical field of power transmission line protection, and more particularly to a fusion ranging method based on multi-frequency band identification. Background Art

[0002] With the continuous commissioning of ultra-high voltage long-distance transmission lines in my country, improving the accuracy and precision of fault distance measurement is of great significance to reducing the pressure of on-site maintenance and shortening power outage time. The traditional impedance distance measurement method is easily affected by factors such as system operation mode, short-circuit transition resistance and transformer transmission error, and it is difficult to meet today's precise positioning requirements. The modern traveling wave distance measurement method is affected by factors such as the uncertainty of the traveling wave source, the variability of busbar wiring methods, and lightning strikes and secondary transmission circuit interference. Its reliability and accuracy still need to be improved.

[0003] In response to the above problems, domestic and foreign scholars have carried out a lot of research work, mainly including: a distance measurement scheme that uses the fusion of single-end traveling wave and double-end traveling wave distance measurement information (Wang Kuixin, etc.), but this method does not consider the complex traveling wave interference caused by lightning strikes and secondary transmission loops, which has an adverse effect on the identification of the initial wave head and reflected wave head of the fault; a traveling wave distance measurement method based on the frequency-varying characteristics of transmission line parameters (Zhu Baihan, etc.), which uses the time domain characteristics of the traveling wave or the difference between high and low frequency components for fault distance measurement, but considering the complex nonlinear relationship between the traveling wave steepness, the traveling wave attenuation characteristics and the fault distance, the accuracy of the distance measurement result is not high; a distance measurement method that uses the anti-interference of traveling wave energy (Han Zhikun, etc.), which uses the square sum of the traveling wave sampling points in a fixed time window to calculate the energy ratio to prevent the interference of noise information. However, it does not consider the problem of extracting the effective wave head caused by the complex traveling wave refraction and reflection process at multiple wave impedance discontinuities such as the fault point, busbar and its back system in the actual system.

[0004] In summary, for the traveling wave ranging method of AC transmission lines, existing research is still imperfect in dealing with the ranging reliability issues caused by frequent traveling wave refraction and reflection processes in the system, waveform distortion caused by secondary transmission loops, noise, lightning strikes and flashover interference. Summary of the invention

[0005] In view of this, the present invention provides a fusion ranging method based on multi-band identification, which combines a variety of abnormal wave detection methods to effectively improve the reliability of traveling wave ranging.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A fusion ranging method based on multi-band identification includes the following steps:

[0008] S1: Obtain the three-phase voltage and current values ​​at the protection installation location;

[0009] S2: Use the power frequency impedance method to determine the power frequency fault point location;

[0010] S3: Calculate the line mode high and low frequency components of the current traveling wave and the line mode low frequency components of the voltage traveling wave by using phase mode decomposition and wavelet decomposition;

[0011] S4: Determine the peak sampling point number according to the peak position of the high-frequency component of the current traveling wave, push forward a time window from the peak sampling point number, and find out whether there are other peaks greater than the setting threshold in the window. If so, set the other peak as the initial traveling wave sampling point number. If not, set the peak sampling point as the initial traveling wave sampling point number.

[0012] S5: Compare the peak values ​​corresponding to the initial traveling wave sampling point numbers of the protections on both sides. The side with the smaller peak value is within the setting time window corresponding to the power frequency fault point position calculated by S2, and the validity check of the initial traveling wave is performed. If the initial traveling wave sampling point number falls within the setting time window, it is valid, otherwise it is invalid.

[0013] S6: verifying the validity of the initial traveling wave according to the polarity relationship between the low-frequency component of the voltage traveling wave and the high-frequency component of the current traveling wave calculated in S3;

[0014] S7: According to the relationship between the ratio of the high-frequency and low-frequency components of the traveling waves of the protection currents on both sides and the fault location, the validity of the initial traveling waves is verified again;

[0015] S8: Determine the fault location based on the initial traveling wave sampling point number of the double-side protection.

[0016] Furthermore, in S2, the calculation formula for determining the power frequency fault point location using the power frequency impedance method is:

[0017]

[0018] Where: L MF and L MN are the distance between the fault point and the M-side protection and the total length of the line respectively; Re and In are the standard symbols for the real part of a complex number and the natural logarithm respectively; cosh and sinh are the standard symbols for the hyperbolic cosine and hyperbolic sine respectively; γ and Z c They are the propagation coefficient and wave impedance of the transmission line, and their values ​​are

[0019] Don't and Where L and C represent the positive sequence inductance and positive sequence capacitance of the line per unit length respectively; and The positive-sequence voltage and positive-sequence current phasor values ​​measured for the M-side and N-side protections respectively.

[0020] Further, in S3, the calculation formulas for calculating the line mode components of the current traveling wave and the voltage traveling wave for the M-side protection and the N-side protection are the same, wherein the calculation formulas for the line mode high and low frequency components of the current traveling wave and the line mode low frequency components of the voltage traveling wave for the M-side protection are:

[0021] Sagami decomposition:

[0022] Wavelet decomposition:

[0023] Where n is the current sampling point number; i Ma 、i Mb 、i M1 、i MH and i ML They are the A-phase current, B-phase current, line mode current, high-frequency component current and low-frequency component current of the M-side protection; u Ma 、u Mb 、u M1 and u ML are the A-phase voltage, B-phase voltage, line mode voltage and low-frequency component voltage after wavelet decomposition of the M-side protection; 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 lengths of the high-pass filter coefficient and the low-pass filter coefficient respectively; k is the point number of the current filter coefficient.

[0024] Furthermore, the filter coefficient P H Set to [-0.23040.7148-0.6309-0.02800.18700.0308-0.0329-0.0106], filter coefficient P L Set to [-0.01060.03290.0308-0.1870

[0025] -0.02800.63090.71480.2304], filter coefficient length N H and N L Both are set to 8.

[0026] Furthermore, in S4, the window length of the time window pushed forward from the peak sampling point number is 10us, and the threshold value is set to 0.7 times the maximum peak value.

[0027] Furthermore, in S5, if the peak value corresponding to the initial traveling wave sampling point of the M-side protection is larger, the relationship between the power frequency fault point position and the traveling wave detection sampling point number of the N-side protection is:

[0028] N NL =N Mmax +(L MN-2L MF )f samp / v

[0029] Where N NL N is the sampling point number of the traveling wave detection of the N-side protection; Mmax L is the initial traveling wave sampling point number of the M side protection; MF and L MN are the distance between the fault point and the M-side protection and the total length of the line respectively; f samp is the sampling frequency; 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;

[0030] If the peak value corresponding to the initial traveling wave sampling point of the N-side protection is larger, the relationship between the power frequency fault point position and the traveling wave detection sampling point number of the M-side protection is:

[0031] N ML =N Nmax -(L MN -2L MF )f samp / v

[0032] Where N ML N is the sampling point number of the traveling wave detection for the M side protection; Nmax It is the initial traveling wave sampling point of N-side protection.

[0033] Furthermore, in S5, the power frequency fault point corresponds to the wave head sampling point number N NL or N ML The detection time window range is 50us. If the initial traveling wave sampling point number N Mmax Falling in [N ML -5*10 -5 / f s ,N ML +5*10 -5 / f s ] range, or N Nmax Falling in [N NL -5*10 -5 / f s ,N NL +5*10 -5 / f s ] range, the initial traveling wave extraction is judged to be valid, otherwise it is invalid.

[0034] Furthermore, in S6, the polarity criterion for verifying the validity of the initial traveling wave is:

[0035]

[0036] In the formula, i MH and u MLare the high-frequency component current and low-frequency component voltage of the M side protection respectively; i NH and u NL are the high-frequency component current and low-frequency component voltage of the N-side protection respectively; Mmax and N Nmax They are the initial traveling wave sampling point numbers of the M-side protection and the N-side protection respectively;

[0037] If the polarity criterion is met, the initial traveling wave is judged to be valid, otherwise, it is judged to be invalid.

[0038] Furthermore, in S7, the peak value ratio criterion for verifying the validity of the initial traveling wave is:

[0039]

[0040] In the formula, i MH and i ML are the high-frequency component current and low-frequency component current of the M side protection respectively; i NH and i NL are the high-frequency component current and low-frequency component current of N-side protection respectively; N Mmax and N Nmax They are the initial traveling wave sampling point numbers of the M-side protection and the N-side protection respectively;

[0041] If the power frequency fault point is close to the M side protection, when the peak value ratio criterion is met, the initial traveling waves on both sides are judged to be valid; when the peak value ratio criterion is not met, the initial traveling waves on both sides are judged to be invalid;

[0042] If the power frequency fault point is close to the N-side protection, when the peak value ratio criterion is met, the initial traveling waves on both sides are judged to be invalid; when the peak value ratio criterion is not met, the initial traveling waves on both sides are judged to be valid.

[0043] Furthermore, in S8, the formula for determining the fault location using the initial traveling wave sampling point number is:

[0044]

[0045] Where, L F and L MN N are the traveling wave ranging distance between the fault point and the M-side protection and the total length of the line respectively; Mmax and N Nmax are the initial traveling wave sampling point numbers for M-side protection and N-side protection respectively; 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.

[0046] It can be seen from the above technical solutions that, compared with the prior art, the present invention has the following beneficial effects:

[0047] The present invention obtains the voltage and current values ​​at the installation locations of the protections on both sides, and uses the power frequency impedance method to determine the position of the power frequency fault point; uses phase mode decomposition and wavelet decomposition to calculate the line mode high and low frequency components of the current traveling wave and the line mode low frequency components of the voltage traveling wave; finds the peak values ​​of the current line mode high frequency components of the protections on both sides, and forward point detection to detect whether there are other wave peaks greater than the threshold; compares the peak values ​​of the protections on both sides, and performs initial traveling wave detection near the power frequency fault point on the side with the smaller peak value; verifies the validity of the initial traveling wave according to the polarity relationship between the voltage traveling wave and the current traveling wave; verifies the validity of the initial traveling wave again according to the current wave peak ratio and fault distance of the different frequency bands of the protections on both sides, and finally completes the double-end traveling wave ranging. The present invention comprehensively utilizes the impedance method and the traveling wave method, and the results of each frequency band are complementary and mutually corrected. Combined with a variety of abnormal wave detection methods, the reliability of the traveling wave ranging is effectively improved, and the problem of insufficient reliability of the traveling wave ranging caused by the frequent traveling wave refraction and reflection process in the system, the waveform distortion caused by the secondary transmission loop, noise, lightning strikes and flashover interference can be dealt with. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] 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.

[0049] Figure 1 The present invention provides a flow chart of a fusion ranging method based on multi-band identification. DETAILED DESCRIPTION

[0050] 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.

[0051] like Figure 1 As shown, the embodiment of the present invention discloses a fusion ranging method based on multi-band identification, which is characterized by comprising the following steps:

[0052] S1: Obtain the three-phase voltage and current values ​​at the protection installation location;

[0053] S2: Use the power frequency impedance method to determine the power frequency fault point location;

[0054] S3: Calculate the line mode high and low frequency components of the current traveling wave and the line mode low frequency components of the voltage traveling wave by using phase mode decomposition and wavelet decomposition;

[0055] S4: Determine the peak sampling point number according to the peak position of the high-frequency component of the current traveling wave, push forward a time window from the peak sampling point number, and find out whether there are other peaks greater than the setting threshold in the window. If so, set the other peak as the initial traveling wave sampling point number. If not, set the peak sampling point as the initial traveling wave sampling point number.

[0056] S5: Compare the peak values ​​corresponding to the initial traveling wave sampling point numbers of the protections on both sides. The side with the smaller peak value is within the setting time window corresponding to the power frequency fault point position calculated by S2, and the validity check of the initial traveling wave is performed. If the initial traveling wave sampling point number falls within the setting time window, it is valid, otherwise it is invalid.

[0057] S6: verifying the validity of the initial traveling wave according to the polarity relationship between the low-frequency component of the voltage traveling wave and the high-frequency component of the current traveling wave calculated in S3;

[0058] S7: According to the relationship between the ratio of the high-frequency and low-frequency components of the traveling waves of the protection currents on both sides and the fault location, the validity of the initial traveling waves is verified again;

[0059] S8: Determine the fault location based on the initial traveling wave sampling point number of the double-side protection.

[0060] The above steps are further described below.

[0061] S1. Obtain the three-phase voltage and current values ​​at the protection installation location.

[0062] In S2, the power frequency impedance method is used to determine the power frequency fault point location, and the calculation formula is:

[0063]

[0064] Where: L MF and L MN are the distance between the fault point and the M-side protection and the total length of the line respectively; Re and In are the standard symbols for the real part of a complex number and the natural logarithm respectively; cosh and sinh are the standard symbols for the hyperbolic cosine and hyperbolic sine respectively; γ and Z c are the propagation coefficient and wave impedance of the transmission line, and their values ​​are and Where L and C represent the positive sequence inductance and positive sequence capacitance of the line per unit length respectively; and The positive-sequence voltage and positive-sequence current phasor values ​​measured for the M-side and N-side protections respectively.

[0065] S3 uses phase mode decomposition and wavelet decomposition to calculate the line mode high and low frequency components of the current traveling wave and the line mode low frequency components of the voltage traveling wave; the calculation formulas for calculating the line mode components of the current traveling wave and the voltage traveling wave for the M-side protection and the N-side protection are the same, among which, the calculation formulas for the line mode high and low frequency components of the current traveling wave and the line mode low frequency components of the voltage traveling wave for the M-side protection are:

[0066] Sagami decomposition:

[0067] Wavelet decomposition:

[0068] Where n is the current sampling point number; i Ma 、i Mb 、i M1 、i MH and i ML They are the A-phase current, B-phase current, line mode current, high-frequency component current and low-frequency component current of the M-side protection; u Ma 、u Mb 、u M1 and u ML are the A-phase voltage, B-phase voltage, line mode voltage and low-frequency component voltage after wavelet decomposition of the M-side protection; 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 lengths of the high-pass filter coefficient and the low-pass filter coefficient respectively; k is the point number of the current filter coefficient.

[0069] Among them, the filter coefficient P H Set to [-0.23040.7148-0.6309-0.02800.18700.0308-0.0329-0.0106], filter coefficient P L Set to [-0.01060.03290.0308-0.1870-0.02800.63090.71480.2304], filter coefficient length N H and N L Both are set to 8.

[0070] S4. Determine the peak sampling point number according to the peak position of the high-frequency component of the current traveling wave, push forward a time window from the peak sampling point number, and look for other wave peaks greater than the setting threshold in the window. If so, set the other wave peak as the initial traveling wave sampling point number. If not, set the peak sampling point as the initial traveling wave sampling point number. The window length of the time window pushed forward from the peak sampling point number is 10us, and the setting threshold value is 0.7 times the maximum peak value.

[0071] S5. Compare the peak values ​​corresponding to the initial traveling wave sampling point numbers of the protections on both sides. The side with the smaller peak value is within the setting time window corresponding to the power frequency fault point position calculated by S2, and the initial traveling wave validity check is performed. If the initial traveling wave sampling point number falls within the setting time window, it is valid, otherwise it is invalid; specifically:

[0072] If the peak value corresponding to the initial traveling wave sampling point of the M-side protection is larger, the relationship between the power frequency fault point position and the traveling wave detection sampling point number of the N-side protection is:

[0073] N NL =N Mmax +(L MN -2L MF )f samp / v

[0074] Where N NL N is the sampling point number of the traveling wave detection of the N-side protection; Mmax L is the initial traveling wave sampling point number of the M side protection; MF and L MN are the distance between the fault point and the M-side protection and the total length of the line respectively; f samp is the sampling frequency; 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;

[0075] If the peak value corresponding to the initial traveling wave sampling point of the N-side protection is larger, the relationship between the power frequency fault point position and the traveling wave detection sampling point number of the M-side protection is:

[0076] N ML =N Nmax -(L MN -2L MF )f samp / v

[0077] Where N ML N is the sampling point number of the traveling wave detection for the M side protection; Nmax It is the initial traveling wave sampling point of N-side protection.

[0078] Among them, the power frequency fault point corresponds to the wave head sampling point number N NL or N ML The detection time window range is 50us. If the initial traveling wave sampling point number N Mmax Falling in [N ML -5*10 -5 / f s ,N ML +5*10 -5 / f s ] range, or N Nmax Falling in [N NL -5*10 -5 / f s ,N NL +5*10 -5 / f s ] range, the initial traveling wave extraction is judged to be valid, otherwise it is invalid.

[0079] S6. According to the polarity relationship between the low-frequency component of the voltage traveling wave and the high-frequency component of the current traveling wave calculated in S3, the validity of the initial traveling wave is verified. The polarity criterion for verifying the validity of the initial traveling wave is:

[0080]

[0081] In the formula, i MH and u ML are the high-frequency component current and low-frequency component voltage of the M side protection respectively; i NH and u NL are the high-frequency component current and low-frequency component voltage of the N-side protection respectively; Mmax and N Nmax They are the initial traveling wave sampling point numbers of the M-side protection and the N-side protection respectively;

[0082] If the polarity criterion is met, the initial traveling wave is judged to be valid, otherwise, it is judged to be invalid.

[0083] S7. According to the relationship between the ratio of the high-frequency and low-frequency components of the protection current traveling waves on both sides and the fault location, the validity of the initial traveling wave is verified again. The peak value ratio criterion for verifying the validity of the initial traveling wave is:

[0084]

[0085] In the formula, i MH and i ML are the high-frequency component current and low-frequency component current of the M side protection respectively; i NH and i NL are the high-frequency component current and low-frequency component current of N-side protection respectively; N Mmax and N Nmax They are the initial traveling wave sampling point numbers of the M-side protection and the N-side protection respectively;

[0086] If the power frequency fault point is close to the M side protection, when the peak value ratio criterion is met, the initial traveling waves on both sides are judged to be valid; when the peak value ratio criterion is not met, the initial traveling waves on both sides are judged to be invalid;

[0087] If the power frequency fault point is close to the N-side protection, when the peak value ratio criterion is met, the initial traveling waves on both sides are judged to be invalid; when the peak value ratio criterion is not met, the initial traveling waves on both sides are judged to be valid.

[0088] S8. Determine the fault location according to the initial traveling wave sampling point number of the double-side protection. The calculation formula is:

[0089]

[0090] Where, L F and L MN N are the traveling wave ranging distance between the fault point and the M-side protection and the total length of the line respectively; Mmax and N Nmax are the initial traveling wave sampling point numbers for M-side protection and N-side protection respectively; 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.

[0091] 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.

[0092] 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 fusion ranging method based on multi-band identification, characterized in that: The following steps are involved: S1: Obtain the three-phase voltage and current values ​​at the protection installation location; S2: Use the power frequency impedance method to determine the power frequency fault point location; S3: Calculate the line mode high and low frequency components of the current traveling wave and the line mode low frequency components of the voltage traveling wave by using phase mode decomposition and wavelet decomposition; S4: Determine the peak sampling point number according to the peak position of the high-frequency component of the current traveling wave, push forward a time window from the peak sampling point number, and find out whether there are other peaks greater than the setting threshold in the window. If so, set the other peak as the initial traveling wave sampling point number. If not, set the peak sampling point as the initial traveling wave sampling point number. S5: Compare the peak values ​​corresponding to the initial traveling wave sampling point numbers of the protections on both sides. The side with the smaller peak value is within the setting time window corresponding to the power frequency fault point position calculated by S2, and the validity check of the initial traveling wave is performed. If the initial traveling wave sampling point number falls within the setting time window, it is valid, otherwise it is invalid. S6: verifying the validity of the initial traveling wave according to the polarity relationship between the low-frequency component of the voltage traveling wave and the high-frequency component of the current traveling wave calculated in S3; S7: According to the relationship between the ratio of the high-frequency and low-frequency components of the traveling waves of the protection currents on both sides and the fault location, the validity of the initial traveling waves is verified again; S8: Determine the fault location based on the initial traveling wave sampling point number of the double-side protection.

2. The fusion ranging method based on multi-band identification according to claim 1 is characterized in that: In S2, the calculation formula for determining the power frequency fault point location using the power frequency impedance method is: Where: L MF and L MN are the distance between the fault point and the M-side protection and the total length of the line respectively; Re and In are the standard symbols for the real part of a complex number and the natural logarithm respectively; cosh and sinh are the standard symbols for the hyperbolic cosine and hyperbolic sine respectively; γ and Z c are the propagation coefficient and wave impedance of the transmission line, and their values ​​are and Where L and C represent the positive sequence inductance and positive sequence capacitance of the line per unit length respectively; and The positive-sequence voltage and positive-sequence current phasor values ​​measured for the M-side and N-side protections respectively.

3. The fusion ranging method based on multi-band identification according to claim 1 is characterized in that: In S3, the calculation formulas for calculating the line mode components of the current traveling wave and the voltage traveling wave for the M-side protection and the N-side protection are the same, wherein the calculation formulas for the line mode high- and low-frequency components of the current traveling wave and the line mode low-frequency components of the voltage traveling wave for the M-side protection are: Sagami decomposition: Wavelet decomposition: Where n is the current sampling point number; i Ma 、i Mb 、i M1 、i MH and i ML They are the A-phase current, B-phase current, line mode current, high-frequency component current and low-frequency component current of the M-side protection; u Ma 、u Mb 、u M1 and u ML are the A-phase voltage, B-phase voltage, line mode voltage and low-frequency component voltage after wavelet decomposition of the M-side protection; 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 lengths of the high-pass filter coefficient and the low-pass filter coefficient respectively; k is the point number of the current filter coefficient.

4. The fusion ranging method based on multi-band identification according to claim 3 is characterized in that: Filter coefficient P H Set to [-0.23040.7148-0.6309-0.02800.18700.0308-0.0329 -0.0106], filter coefficient P L Set to [-0.01060.03290.0308-0.1870-0.02800.63090.71480.2304], filter coefficient length N H and N L Both are set to 8.

5. The fusion ranging method based on multi-band identification according to claim 1 is characterized in that: In S4, the window length of the time window pushed forward from the peak sampling point number is 10us, and the threshold value is set to 0.7 times the maximum peak value.

6. The fusion ranging method based on multi-band identification according to claim 1, characterized in that: In S5, if the peak value corresponding to the initial traveling wave sampling point of the M-side protection is larger, the relationship between the power frequency fault point position and the traveling wave detection sampling point number of the N-side protection is: N NL =N Mmax +(L MN -2L MF )f samp / v Where N NL N is the sampling point number of the traveling wave detection of the N side protection; Mmax L is the initial traveling wave sampling point number of the M side protection; MF and L MN are the distance between the fault point and the M-side protection and the total length of the line respectively; f samp is the sampling frequency; 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; If the peak value corresponding to the initial traveling wave sampling point of the N-side protection is larger, the relationship between the power frequency fault point position and the traveling wave detection sampling point number of the M-side protection is: N ML =N Nmax -(L MN -2L MF )f samp / v Where N ML N is the sampling point number of the traveling wave detection of the M side protection; Nmax It is the initial traveling wave sampling point of N-side protection.

7. The fusion ranging method based on multi-band identification according to claim 6 is characterized in that: In S5, the power frequency fault point corresponds to the wave head sampling point number N NL or N ML The detection time window range is 50us. If the initial traveling wave sampling point number N Mmax Falling in [N ML -5*10 -5 / f s ,N ML +5*10 -5 / f s ] range, or N Nmax Falling in [N NL -5*10 -5 / f s ,N NL +5*10 -5 / f s ] range, the initial traveling wave extraction is judged to be valid, otherwise it is invalid.

8. The fusion ranging method based on multi-band identification according to claim 1, characterized in that: In S6, the polarity criterion for verifying the validity of the initial traveling wave is: In the formula, i MH and u ML are the high-frequency component current and low-frequency component voltage of the M side protection respectively; i NH and u NL are the high-frequency component current and low-frequency component voltage of the N-side protection respectively; Mmax and N Nmax They are the initial traveling wave sampling point numbers of the M-side protection and the N-side protection respectively; If the polarity criterion is met, the initial traveling wave is judged to be valid, otherwise, it is judged to be invalid.

9. The fusion ranging method based on multi-band identification according to claim 1, characterized in that: In S7, the peak value ratio criterion for verifying the validity of the initial traveling wave is: In the formula, i MH and i ML are the high-frequency component current and low-frequency component current of the M side protection respectively; i NH and i NL are the high-frequency component current and low-frequency component current of N-side protection respectively; N Mmax and N Nmax They are the initial traveling wave sampling point numbers of the M-side protection and the N-side protection respectively; If the power frequency fault point is close to the M side protection, when the peak value ratio criterion is met, the initial traveling waves on both sides are judged to be valid; when the peak value ratio criterion is not met, the initial traveling waves on both sides are judged to be invalid; If the power frequency fault point is close to the N-side protection, when the peak value ratio criterion is met, the initial traveling waves on both sides are judged to be invalid; when the peak value ratio criterion is not met, the initial traveling waves on both sides are judged to be valid.

10. The fusion ranging method based on multi-band identification according to claim 1, characterized in that: In S8, the formula for determining the fault location using the initial traveling wave sampling point number is: Where, L F and L MN N are the traveling wave ranging distance between the fault point and the M-side protection and the total length of the line respectively; Mmax and N Nmax are the initial traveling wave sampling point numbers for M-side protection and N-side protection respectively; 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.

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