Cable loss extreme point identification method, system and device under broadband disturbance and medium

Abstract

The invention provides a cable loss extreme point identification method, system and device under broadband disturbance and a medium, and the method comprises the steps: carrying out the time-frequency transformation analysis of a power detection parameter of a to-be-identified cable, and obtaining frequency domain feature data containing a plurality of frequency components; calculating cable parameters when each frequency component acts according to the cable structure of the cable to be identified; according to the frequency domain characteristic data and the cable parameters, cable current distribution in the broadband harmonic environment is calculated by using a transmission line fluctuation model; searching the maximum value of the cable current in the cable current distribution in the broadband harmonic environment; and based on the maximum value of the cable current, identifying the position of a cable loss extreme value by using a transmission line electromagnetic-thermal coupling model. According to the invention, accurate identification of the position of the loss extreme point of the cable in the broadband harmonic environment can be realized, the surface temperature of the cable does not need to be monitored by a sensor, and the investment cost is greatly reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power cable state monitoring, and in particular to a cable loss extreme point identification method, system, device and medium under wideband disturbance. BACKGROUND

[0002] Power cable is a key component of power transmission and distribution system, and its operating state directly affects the reliability and safety of power grid. Under the background of high proportion of new energy grid connection and surge of nonlinear load, cable lines are often affected by wideband harmonic disturbance, which leads to abnormal increase of conductor loss and dielectric loss, and causes local overheating, insulation aging and even breakdown. Therefore, identifying the cable loss extreme point is crucial to prevent faults.

[0003] Considering the positive inverse relationship between temperature and cable loss, current traditional identification methods mostly monitor the surface temperature of the cable through infrared or distributed optical fiber sensors. However, this local temperature measurement method requires a large amount of cost to ensure accurate identification of the loss extreme point. In addition, current transmission line models mostly ignore the frequency-dependent characteristics of cable parameters, which are not suitable for the identification requirements of cable loss extreme point identification, especially in complex harmonic conditions such as high proportion of new energy grid connection, it is difficult to identify the accurate position of the loss extreme point. SUMMARY

[0004] In order to overcome the defects of low accuracy and high cost in the loss extreme point identification of the above-mentioned traditional technology, the present application provides a cable loss extreme point identification method under wideband disturbance, comprising:

[0005] Performing time-frequency transformation analysis on the power detection parameters of the cable to be identified to obtain frequency domain feature data containing multiple frequency components;

[0006] According to the cable structure of the cable to be identified, the cable parameters under the action of each frequency component are calculated;

[0007] According to the frequency domain feature data and the cable parameters, the cable current distribution under the wideband harmonic environment is calculated by using the transmission line wave model;

[0008] The maximum cable current under the wideband harmonic environment is found, and based on the maximum cable current, the position of the cable loss extreme point is identified by using the transmission line electromagnetic-thermal coupling model.

[0009] Optionally, the calculation of the cable current distribution under the wideband harmonic environment by using the transmission line wave model according to the frequency domain feature data and the cable parameters comprises:

[0010] According to the harmonic amplitude of each frequency component in the frequency feature data, the propagation coefficient and the wave impedance in the cable parameters, the cable current distribution under the wideband harmonic environment is calculated by using the transmission line wave model.

[0011] Optionally, the transmission line ripple model satisfies the following formula:

[0012] in, This refers to the cable current distribution under broadband harmonic environments, U1(ω i ) is the amplitude of the i-th harmonic at the first end, Γ1(ω i Γ2(ω) is the reflection coefficient at the head end corresponding to the i-th harmonic; i Z is the reflection coefficient at the end corresponding to the i-th harmonic; G (ω i Z is the equivalent impedance of the component connected to the first terminal corresponding to the i-th harmonic; R (ω i ) is the equivalent impedance of the component connected to the end corresponding to the i-th harmonic; γ(ω) i Z is the propagation coefficient corresponding to the i-th harmonic; c (ω i ω is the wave impedance corresponding to the i-th harmonic. i is the frequency of the i-th harmonic, x is the distance between the selected location and the beginning of the cable, i takes values ​​of 1, ..., n, and n is the total number of harmonics.

[0013] Optionally, the transmission line electromagnetic-thermal coupling model incorporates conductor loss and armor layer loss.

[0014] The electromagnetic-thermal coupling model of the transmission line satisfies the following formula:

[0015] Where W is the cable loss, W 1,i W is the conductor loss corresponding to the i-th harmonic. 2,i This represents the armor layer loss corresponding to the i-th harmonic, where i takes values ​​from 1 to n, and n is the total harmonic order. λ(ω) i ) is the armor layer loss factor corresponding to the i-th harmonic, I i R is the current corresponding to the i-th harmonic. ac (ω i ω is the AC resistance corresponding to the i-th harmonic. i It is the frequency of the i-th harmonic.

[0016] Optionally, the cable parameters include propagation coefficient and wave impedance;

[0017] The calculation of cable parameters for each frequency component based on the cable structure of the cable to be identified includes:

[0018] Based on the cable structure of the cable to be identified, calculate the resistance, inductance, capacitance, and conductance per unit length between the conductors in the cable to be identified;

[0019] Calculate the impedance per unit length based on the resistance and inductance per unit length between the conductors in the cable to be identified;

[0020] Calculate the admittance per unit length based on the capacitance and conductance per unit length between the conductors in the cable to be identified;

[0021] The propagation coefficient of the cable to be identified is calculated based on the product of the impedance and admittance per unit length.

[0022] The wave impedance of the cable to be identified is calculated based on the ratio of impedance to admittance per unit length.

[0023] Optionally, the propagation coefficient of the cable to be identified satisfies the following formula:

[0024] Where γ is the propagation coefficient, Z0 is the impedance per unit length, Y0 is the admittance per unit length, R0 is the resistance per unit length between conductors, l0 is the inductance per unit length between conductors, C0 is the capacitance per unit length between conductors, G0 is the conductance per unit length between conductors, ω is the magnitude of the angular frequency, and j is the imaginary unit.

[0025] The wave impedance of the cable to be identified satisfies the following formula:

[0026] Among them, Z c Z0 is the wave impedance, Y0 is the impedance per unit length, R0 is the resistance per unit length between conductors, L0 is the inductance per unit length between conductors, C0 is the capacitance per unit length between conductors, G0 is the conductance per unit length between conductors, ω is the magnitude of the angular frequency, and j is the imaginary unit.

[0027] Optionally, calculating the resistance, inductance, capacitance, and conductance per unit length between conductors in the cable to be identified, based on the cable structure of the cable to be identified, includes:

[0028] Calculate the resistance per unit length between conductors based on the angular frequency, conductor permeability, conductor conductivity, conductor radius, and inner diameter of the metal shielding layer in the cable structure.

[0029] Calculate the inductance per unit length between conductors based on the outer diameter of the metal shielding layer in the cable structure, the magnitude of the angular frequency, the magnitude of the conductor permeability, the conductor conductivity, and the radius of the conductor core.

[0030] Based on the complex permittivity of the medium in the cable structure and the inner and outer radii of the medium, calculate the capacitance and conductance per unit length between the conductors.

[0031] Optionally, the resistance per unit length between the conductors satisfies the following formula:

[0032] Where R0 is the resistance per unit length between conductors, ω is the angular frequency; μ is the magnetic permeability of the conductor; σ is the electrical conductivity of the conductor; r cu It is the radius of the conductor core; r sh It is the inner diameter of the metal shielding layer;

[0033] The inductance per unit length between the conductors satisfies the following formula:

[0034] Where L0 is the inductance per unit length between conductors, ω is the angular frequency; μ is the permeability of the conductor; σ is the conductivity of the conductor; r cu It is the radius of the conductor core; r' sh is the outer diameter of the metal shielding layer, and ln() is the natural logarithm function;

[0035] The capacitance per unit length between the conductors satisfies the following formula:

[0036] Where C0 is the capacitance per unit length between conductors, ε k (ω) is the complex permittivity of the k-th dielectric layer; r k and r k+1 ω and j are the inner and outer radii of the k-th medium layer, respectively, where k takes values ​​from 1 to N, N is the total number of medium layers, ω is the magnitude of the angular frequency, j is the imaginary unit, and Im() is the function for finding the imaginary part.

[0037] The conductivity per unit length between the conductors satisfies the following formula:

[0038] Where G0 is the conductance per unit length between conductors, ε k (ω) is the complex permittivity of the k-th dielectric layer; r k and r k+1 ω and j are the inner and outer radii of the k-th medium layer, respectively, where k takes values ​​from 1 to N, N is the total number of medium layers, ω is the angular frequency, j is the imaginary unit, and Re() is the function to find the real part.

[0039] On the other hand, the present invention also provides a cable loss extreme point identification system under broadband disturbance, comprising:

[0040] The time-frequency transformation analysis module is used to perform time-frequency transformation analysis on the power detection parameters of the cable to be identified, and obtain frequency domain feature data containing multiple frequency components;

[0041] The cable parameter calculation module is used to calculate the cable parameters when each frequency component is applied, based on the cable structure of the cable to be identified.

[0042] The current distribution calculation module is used to calculate the cable current distribution under broadband harmonic environment based on the frequency domain characteristic data and the cable parameters, using the transmission line ripple model.

[0043] The loss extreme value identification module is used to find the maximum value of cable current in the cable current distribution under the broadband harmonic environment; based on the maximum value of cable current, the location of the cable loss extreme value is identified using the transmission line electromagnetic-thermal coupling model.

[0044] Optionally, the current distribution calculation module is specifically used for:

[0045] Based on the harmonic amplitude of each frequency component in the frequency characteristic data, the propagation coefficient and wave impedance in the cable parameters, the cable current distribution under broadband harmonic environment is calculated using the transmission line ripple model.

[0046] Optionally, the transmission line ripple model satisfies the following formula:

[0047] in, This refers to the cable current distribution under broadband harmonic environments, U1(ω i ) is the amplitude of the i-th harmonic at the first end, Γ1(ω i Γ2(ω) is the reflection coefficient at the head end corresponding to the i-th harmonic; i Z is the reflection coefficient at the end corresponding to the i-th harmonic; G (ω i Z is the equivalent impedance of the component connected to the first terminal corresponding to the i-th harmonic; R (ω i ) is the equivalent impedance of the component connected to the end corresponding to the i-th harmonic; γ(ω) i Z is the propagation coefficient corresponding to the i-th harmonic; c (ω i ω is the wave impedance corresponding to the i-th harmonic. i is the frequency of the i-th harmonic, x is the distance between the selected location and the beginning of the cable, i takes values ​​of 1, ..., n, and n is the total number of harmonics.

[0048] Optionally, the transmission line electromagnetic-thermal coupling model incorporates conductor loss and armor layer loss.

[0049] The electromagnetic-thermal coupling model of the transmission line satisfies the following formula:

[0050] Where W is the cable loss, W 1,i W is the conductor loss corresponding to the i-th harmonic. 2,iThis represents the armor layer loss corresponding to the i-th harmonic, where i takes values ​​from 1 to n, and n is the total harmonic order. λ(ω) i ) is the armor layer loss factor corresponding to the i-th harmonic, I i R is the current corresponding to the i-th harmonic. ac (ω i ω is the AC resistance corresponding to the i-th harmonic. i It is the frequency of the i-th harmonic.

[0051] Optionally, the cable parameters include propagation coefficient and wave impedance;

[0052] The cable parameter calculation module includes:

[0053] The distributed parameter calculation unit is used to calculate the resistance, inductance, capacitance and conductance per unit length between conductors in the cable to be identified based on the cable structure of the cable to be identified.

[0054] The impedance calculation unit is used to calculate the impedance per unit length based on the resistance and inductance per unit length between conductors in the cable to be identified.

[0055] The admittance calculation unit is used to calculate the admittance per unit length based on the capacitance and conductance per unit length between conductors in the cable to be identified.

[0056] The propagation coefficient calculation unit is used to calculate the propagation coefficient of the cable to be identified based on the product of the impedance and admittance per unit length.

[0057] The wave impedance calculation unit is used to calculate the wave impedance of the cable to be identified based on the ratio of impedance to admittance per unit length.

[0058] Optionally, the propagation coefficient of the cable to be identified satisfies the following formula:

[0059] Where γ is the propagation coefficient, Z0 is the impedance per unit length, Y0 is the admittance per unit length, R0 is the resistance per unit length between conductors, L0 is the inductance per unit length between conductors, C0 is the capacitance per unit length between conductors, G0 is the conductance per unit length between conductors, ω is the magnitude of the angular frequency, and j is the imaginary unit.

[0060] The wave impedance of the cable to be identified satisfies the following formula:

[0061] Among them, Z cZ0 is the wave impedance, Y0 is the impedance per unit length, R0 is the resistance per unit length between conductors, l0 is the inductance per unit length between conductors, C0 is the capacitance per unit length between conductors, G0 is the conductance per unit length between conductors, ω is the magnitude of the angular frequency, and j is the imaginary unit.

[0062] Optionally, the distribution parameter calculation unit is specifically used for:

[0063] Calculate the resistance per unit length between conductors based on the angular frequency, conductor permeability, conductor conductivity, conductor radius, and inner diameter of the metal shielding layer in the cable structure.

[0064] Calculate the inductance per unit length between conductors based on the outer diameter of the metal shielding layer in the cable structure, the magnitude of the angular frequency, the magnitude of the conductor permeability, the conductor conductivity, and the radius of the conductor core.

[0065] Based on the complex permittivity of the medium in the cable structure and the inner and outer radii of the medium, calculate the capacitance and conductance per unit length between the conductors.

[0066] Optionally, the resistance per unit length between the conductors satisfies the following formula:

[0067] Where R0 is the resistance per unit length between conductors, ω is the angular frequency; μ is the magnetic permeability of the conductor; σ is the electrical conductivity of the conductor; r cu It is the radius of the conductor core; r sh It is the inner diameter of the metal shielding layer;

[0068] The inductance per unit length between the conductors satisfies the following formula:

[0069] Where L0 is the inductance per unit length between conductors, ω is the angular frequency; μ is the permeability of the conductor; σ is the conductivity of the conductor; r cu It is the radius of the conductor core; r' sh is the outer diameter of the metal shielding layer, and ln() is the natural logarithm function;

[0070] The capacitance per unit length between the conductors satisfies the following formula:

[0071] Where C0 is the capacitance per unit length between conductors, ε k (ω) is the complex permittivity of the k-th dielectric layer; r k and r k+1 ω and j are the inner and outer radii of the k-th medium layer, respectively, where k takes values ​​from 1 to N, N is the total number of medium layers, ω is the magnitude of the angular frequency, j is the imaginary unit, and Im() is the function for finding the imaginary part.

[0072] The conductivity per unit length between the conductors satisfies the following formula:

[0073] Where G0 is the conductance per unit length between conductors, ε k (ω) is the complex permittivity of the k-th dielectric layer; r k and r k+1 ω and j are the inner and outer radii of the k-th medium layer, respectively, where k takes values ​​from 1 to N, N is the total number of medium layers, ω is the angular frequency, j is the imaginary unit, and Re() is the function to find the real part.

[0074] On the other hand, the present invention also provides a computer device, characterized in that it includes: one or more processors;

[0075] The processor is used to store one or more programs;

[0076] When the one or more programs are executed by the one or more processors, the cable loss extreme point identification method under broadband disturbance described in any one of the above-described methods is implemented.

[0077] On the other hand, the present invention also provides a computer-readable storage medium, characterized in that it stores a computer program thereon, which, when executed, implements the cable loss extreme point identification method under broadband disturbance as described in any one of the above.

[0078] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0079] This invention provides a method, system, device, and medium for identifying cable loss extreme points under broadband disturbances. The method involves performing time-frequency transformation analysis on the electrical detection parameters of the cable to be identified, obtaining frequency domain characteristic data containing multiple frequency components; calculating the cable parameters under the influence of each frequency component based on the cable structure; calculating the cable current distribution under broadband harmonic environments using a transmission line ripple model based on the frequency domain characteristic data and cable parameters; identifying the maximum cable current value within the broadband harmonic environment; and identifying the location of the cable loss extreme point using a transmission line electromagnetic-thermal coupling model based on the maximum cable current value. This invention accurately reflects the spatial distribution of cable current under broadband harmonic environments by combining the cable's electrical detection parameters with the transmission line ripple model. Furthermore, the transmission line electromagnetic-thermal coupling model enables accurate identification of cable loss extreme points under broadband harmonic environments. Moreover, this invention eliminates the need for sensors to monitor cable surface temperature, significantly reducing investment costs. Attached Figure Description

[0080] Figure 1 This is a flowchart illustrating the cable loss extreme point identification method under broadband disturbance of the present invention.

[0081] Figure 2 This is a schematic diagram of the transmission line equivalent circuit model of the present invention;

[0082] Figure 3 This is a schematic diagram of the cable current extreme point calculation process according to the present invention;

[0083] Figure 4 This is a schematic diagram of the cable loss extreme point identification system under broadband disturbance of the present invention;

[0084] Figure 5 This is a schematic diagram of the electronic device of the present invention. Detailed Implementation

[0085] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0086] Example 1:

[0087] This invention provides a method for identifying extreme points of cable loss under broadband disturbances, as follows: Figure 1 As shown, it includes:

[0088] Step 101: Perform time-frequency transformation analysis on the power detection parameters of the cable to be identified to obtain frequency domain feature data containing multiple frequency components.

[0089] Step 102: Calculate the cable parameters when each frequency component is applied, based on the cable structure of the cable to be identified.

[0090] Step 103: Based on the frequency domain characteristic data and cable parameters, use the transmission line ripple model to calculate the cable current distribution under broadband harmonic environment.

[0091] Step 104: Locate the maximum cable current value in the cable current distribution under broadband harmonic environment; based on the maximum cable current value, use the transmission line electromagnetic-thermal coupling model to identify the location of the extreme value of cable loss.

[0092] In this embodiment of the invention, the power detection parameters of the cable are combined with the transmission line fluctuation model to accurately reflect the spatial distribution of cable current under broadband harmonic environment. Furthermore, the transmission line electromagnetic-thermal coupling model can accurately identify the location of cable loss extreme points under broadband harmonic environment. Moreover, this invention does not require the use of sensors to monitor the cable surface temperature, which greatly reduces the investment cost.

[0093] In step 101 above, the cable to be identified refers to the cable at which the extreme loss point is to be identified; for ease of description, it will be simply referred to as the cable below. The cable's electrical detection parameters can be the cable's end electrical detection parameters, including voltage and / or current measurement data, more specifically, end voltage and / or end current, such as cable voltage and / or current measurement data at the cable's head end, or voltage and / or current measurement data at both ends. In this embodiment of the invention, by measuring the cable's electrical detection parameters (such as end voltage), there is no need to use sensors to locally measure the cable surface temperature, thus avoiding inaccuracies caused by local measurements and the cost issues associated with excessive sensors. Subsequently, combined with the transmission line electromagnetic-thermal coupling model, the identification of cable loss extreme points under broadband harmonic environments can be achieved.

[0094] Wideband harmonics are high-frequency interference phenomena in power systems. Under wideband harmonic environments, current or voltage waveform distortion may occur, increasing power loss and reducing the efficiency of the power system. In other words, wideband harmonic disturbance conditions exist under wideband harmonic environments.

[0095] In one implementation, step 101 above can perform FFT (Fast Fourier Transform) analysis on the cable's electrical detection parameters (such as the terminal current and / or terminal voltage) to obtain frequency domain feature data containing multiple frequency components. Optionally, after performing time-frequency transformation analysis, the data after time-frequency transformation analysis can also be normalized to obtain frequency domain feature data containing multiple frequency components.

[0096] Cable parameters include transmission coefficient and wave impedance. In addition, distributed parameters can also be included. For example, in step 102 above, based on the cable structure, the distributed parameters, transmission coefficient and wave impedance of the cable can be calculated when each frequency component is applied.

[0097] like Figure 2 As shown, the distributed parameters include resistance R0, inductance l0, capacitance C0, and conductance G0. Considering that the distributed parameter model of the transmission line is a limiting case of lumped parameter elements, and since the resistance, inductance, capacitance, and conductance are distributed along the transmission line, in this embodiment of the invention, they are represented by the parameters of the transmission line per unit length.

[0098] In one possible implementation, in step 102 above, the resistance, inductance, capacitance, and conductance per unit length of the conductors in the cable to be identified can be calculated based on the cable structure of the cable to be identified; the impedance per unit length can be calculated based on the resistance and inductance per unit length of the conductors in the cable to be identified; the admittance per unit length can be calculated based on the capacitance and conductance per unit length of the conductors in the cable to be identified; the propagation coefficient of the cable to be identified can be calculated based on the product of the impedance and admittance per unit length; and the wave impedance of the cable to be identified can be calculated based on the ratio of the impedance to the admittance per unit length.

[0099] When calculating the resistance per unit length between conductors based on the cable structure, the resistance R0 between conductors can be calculated using the angular frequency, conductor permeability, conductor conductivity, conductor radius, and inner diameter of the metal shielding layer within the cable structure. For example, in this embodiment of the invention, R0 can satisfy the following formula:

[0100] Where ω is the magnitude of the angular frequency; μ is the magnitude of the conductor's permeability; σ is the conductor's conductivity; r cu It is the radius of the conductor core; r sh It is the inner diameter of the metal shielding layer.

[0101] When calculating the inductance per unit length between conductors based on the cable structure, the inductance L0 between conductors can be calculated using the angular frequency, conductor permeability, conductor conductivity, conductor radius, and outer diameter of the metal shielding layer within the cable structure. For example, in this embodiment of the invention, l0 can satisfy the following formula:

[0102] Where ω is the magnitude of the angular frequency; μ is the magnitude of the conductor's permeability; σ is the conductor's conductivity; r cu It is the radius of the conductor core; r' sh is the outer diameter of the metal shielding layer, and ln() is the natural logarithm function.

[0103] When calculating the capacitance per unit length between conductors based on the cable structure, the capacitance C0 between conductors can be calculated based on the complex permittivity and inner / outer radii of the dielectric in the cable structure. For example, in an embodiment of the invention, C0 can satisfy the following formula:

[0104] Where, ε k (ω) is the complex permittivity of the k-th dielectric layer; r k and r k+1ω and j are the inner and outer radii of the k-th medium layer, respectively, where k takes values ​​from 1 to N, N is the total number of medium layers, ω is the magnitude of the angular frequency, j is the imaginary unit, and Im() is the function for finding the imaginary part.

[0105] When calculating the conductance per unit length between conductors based on the cable structure, the conductance G0 between conductors can be calculated based on the complex permittivity and inner / outer radii of the dielectric in the cable structure. For example, in an embodiment of the invention, G0 can satisfy the following formula:

[0106] Where, ε k (ω) is the complex permittivity of the k-th dielectric layer; r k and r k+1 ω and j are the inner and outer radii of the k-th medium layer, respectively, where k takes values ​​from 1 to N, N is the total number of medium layers, ω is the angular frequency, j is the imaginary unit, and Re() is the function to find the real part.

[0107] The complex permittivity ε of the above-mentioned medium k (ω) can be the complex permittivity of the semiconducting material, which is related to the material's relaxation time, DC conductivity, and high-frequency components of the permittivity, and can satisfy the following formula:

[0108] Where τ1 and τ2 are the material relaxation times, σ dc ε is the DC conductivity of the material. ∞ ω is the high-frequency component of the dielectric constant, j is the imaginary unit, A1, A2, α1, and α2 are fitting constants, which can be obtained by fitting experimental data to obtain the specific expression of the equation, and ε0 is the vacuum dielectric constant.

[0109] It is understood that the angular frequency ω involved in the formula of the present invention can be regarded as any frequency. That is, any harmonic frequency can be substituted into the above formula to calculate the distributed parameters, transmission coefficient and wave impedance of the cable when each frequency component is applied. Subsequent similar cases will not be explained one by one.

[0110] If the above-mentioned distribution parameters are equal everywhere along the cable, it is called a uniform transmission line. In this embodiment of the invention, the discussion and description mainly focus on the uniform transmission line model.

[0111] The impedance per unit length calculated above based on the resistance and inductance per unit length between conductors in the cable to be identified can be the impedance Z0 per unit length of a uniform transmission line. For example, Z0 can satisfy the following formula: Z0=R0+jωL0, where R0 is the resistance per unit length between conductors, L0 is the inductance per unit length between conductors, ω is the magnitude of the angular frequency, and j is the imaginary unit.

[0112] The admittance per unit length calculated above based on the capacitance and conductance per unit length between conductors in the cable to be identified can be the admittance Y0 per unit length of a uniform transmission line. For example, Y0 can satisfy the following formula: Y0=G0+jωC0, where C0 is the capacitance per unit length between conductors, G0 is the conductance per unit length between conductors, ω is the angular frequency, and j is the imaginary unit.

[0113] When calculating the propagation coefficient γ of the cable to be identified based on the product of impedance and admittance per unit length, the following formula can be satisfied: Where γ is the propagation coefficient, Z0 is the impedance per unit length, Y0 is the admittance per unit length, R0 is the resistance per unit length between conductors, L0 is the inductance per unit length between conductors, C0 is the capacitance per unit length between conductors, G0 is the conductance per unit length between conductors, ω is the magnitude of the angular frequency, and j is the imaginary unit.

[0114] The above calculation uses the ratio of impedance to admittance per unit length to determine the wave impedance Z of the cable to be identified. c When the wave impedance of the cable to be identified satisfies the following formula: Among them, Z c Z0 is the wave impedance, Y0 is the impedance per unit length, R0 is the resistance per unit length between conductors, L0 is the inductance per unit length between conductors, C0 is the capacitance per unit length between conductors, G0 is the conductance per unit length between conductors, ω is the magnitude of the angular frequency, and j is the imaginary unit.

[0115] In one implementation, in step 103 above, the cable current distribution under broadband harmonic environments can be calculated using a transmission line wave model based on the harmonic amplitudes of each frequency component in the frequency characteristic data, the propagation coefficient, and the wave impedance in the cable parameters. For example, based on the harmonic amplitudes of each frequency component in the frequency characteristic data, the propagation coefficient, and the wave impedance in the cable parameters, the traveling wave and anti-traveling wave of each frequency component are calculated respectively; the differences between the traveling wave and anti-traveling wave of each frequency component are summed to obtain the cable current distribution under broadband harmonic environments.

[0116] For example, the transmission line ripple model satisfies the following formula:

[0117]

[0118] in, This refers to the cable current distribution under broadband harmonic environments, U1(ω i ) is the amplitude of the i-th harmonic at the first end, Γ1(ω iΓ2(ω) is the reflection coefficient at the head end corresponding to the i-th harmonic; i Z is the reflection coefficient of the terminal corresponding to the i-th harmonic; G (ω i Z represents the equivalent impedance of the component connected to the first terminal corresponding to the i-th harmonic; R (ω i ) represents the equivalent impedance of the component connected to the terminal corresponding to the i-th harmonic; γ(ω) i Z is the propagation coefficient corresponding to the i-th harmonic; c (ω i ω is the wave impedance corresponding to the i-th harmonic. i is the frequency of the i-th harmonic, x is the distance between the selected location and the beginning of the cable, i takes values ​​of 1, ..., n, and n is the total number of harmonics.

[0119] The above transmission line ripple model can be derived through the following process:

[0120] Assume that one end of the cable is the cable start end and the other end is the cable end end, and the distance between the start end and the end end is l, that is, assume that the cable length is l.

[0121] First, we analyze the cable current under the influence of a single-frequency harmonic. (Referring to the above...) Figure 2 Analyzing the steady-state circuit shown, we can see that:

[0122]

[0123] In the formula, It is the voltage vector on the cable; It is the current vector on the cable; x is the distance between the selected location and the cable start, A1 and A2 are integration constants, and Z is the current vector on the cable. c γ is the wave impedance, and γ is the propagation coefficient.

[0124] If the terminal voltage and current are both known, and satisfy the following conditions: achievable In the formula, the reflection coefficient at the head end Reflection coefficient at the end Z G It is the equivalent impedance of the component connected to the beginning of the cable; Z R It is the equivalent impedance of the component connected to the end of the cable. It is the voltage vector at the beginning and end of the cable, where U1 is the voltage amplitude at the beginning of the cable. is the current vector at the beginning and end of the cable, and l is the cable length.

[0125] The frequency can be obtained as ω i The current distribution at different locations along the cable length under the influence of harmonics:

[0126]

[0127] in, At frequency ω i The current distribution at position x is determined by the harmonic effect of the cable, where l is the cable length and is a known condition; Z G It is the equivalent impedance of the component connected to the beginning of the cable; Z R It is the equivalent impedance of the component connected to the end of the cable; Z G Z R The results can all be obtained using the impedance scanning method, Z c γ is the wave impedance, and γ is the propagation coefficient.

[0128] At each frequency By superimposing these components, the aforementioned transmission line ripple model can be obtained.

[0129] In one implementation, when searching for the maximum cable current in the cable current distribution under a broadband harmonic environment in step 104 above, the cable current distribution data can be converted into a two-dimensional data graph. In the two-dimensional graph, the horizontal axis is the distance (i.e., x above), and the vertical axis is the current amplitude. Then, the maximum cable current can be quickly found in the two-dimensional data graph, and the location of the maximum cable current can be located.

[0130] In step 104, the transmission line electromagnetic-thermal coupling model illustrates the relationship between current and loss. Therefore, based on the location of the maximum cable current, combined with the transmission line electromagnetic-thermal coupling model, the location of the extreme cable loss can be quickly and accurately identified. For example, the location of the maximum cable current is the location of the extreme cable loss.

[0131] This transmission line electromagnetic-thermal coupling model incorporates conductor loss and armor layer loss. Generally, cable losses include conductor loss, insulation dielectric loss, and armor layer loss. In this embodiment of the invention, it is generally assumed that only cable insulation with voltage levels of 110kV and above needs to consider insulation dielectric loss, and this loss is ignored here.

[0132] The conductor loss W1 is the Joule heat loss per unit length of the conductor when alternating current flows through a power cable. The conductor loss is related to the current, and in the example, it satisfies the following formula: W1 = I 2 R ac In the formula, I is the current flowing through the conductor core; R ac R represents the AC resistance per unit length of cable, expressed in Ω / m (ohms per meter). In this embodiment of the invention, the skin effect and proximity effect of the conductor are considered under harmonic environments. ac Satisfy R ac =R dc (1+y s +yp In the formula, y s y is the skin effect coefficient. p R is the proximity effect coefficient. dc This is the DC resistance per unit length of cable at the operating temperature.

[0133] The armor layer loss W2 consists of two parts: hysteresis loss and eddy current loss. Both of these losses are related to the conductor loss. For example, they satisfy the following formula: W2 = λ1W1 + λ2W1 = (λ1 + λ2)W1 = λW1, where λ is the armor layer loss factor, which is the sum of the hysteresis loss factor λ1 and the eddy current loss factor λ2, i.e., λ = λ1 + λ2. In a possible scenario, for a three-core cable with steel tape armor, when the steel tape thickness is 0.3mm to 1.0mm, λ1 satisfies the following formula: λ² satisfies the following formula: In the formula, S is the distance between the centers of each conductor; δ is the equivalent thickness of the armor; d A denoted as the average diameter of the armor; f is the excitation operating frequency; μ is the relative permeability; and R is the AC resistance of the conductor at the maximum allowable operating temperature.

[0134] For example, the electromagnetic-thermal coupling model of a transmission line satisfies the following formula: W = W1 + W2 = (1 + λ)W1 = (1 + λ)I 2 R ac Where W is the cable loss. In this formula, the location of the point where the cable loss is at its maximum is also the location of the location of the maximum effective value of the current in the cable.

[0135] Based on the above formula, when the frequency range is f1, f2, ..., f n When subjected to broadband harmonics, the cable loss W, i.e., the electromagnetic-thermal coupling model of the transmission line, satisfies the following formula:

[0136] Where W is the cable loss, W 1,i W is the conductor loss corresponding to the i-th harmonic. 2,i This represents the armor layer loss corresponding to the i-th harmonic, where i takes values ​​from 1 to n, and n is the total harmonic order, i.e., the total number of frequency components. λ(ω) i ) is the armor layer loss factor corresponding to the i-th harmonic, I i R is the current corresponding to the i-th harmonic. ac (ω i Let be the AC resistance corresponding to the i-th harmonic. From this formula, it can be determined that when the power supply frequency and cable structural parameters are known, the extreme point distribution of cable loss under broadband harmonic environments is still related to the extreme point distribution of cable current.

[0137] The following is combined Figure 3The specific embodiments shown illustrate the present invention.

[0138] The cable terminal voltage data is collected, then subjected to FFT analysis and normalization to obtain frequency domain characteristic data containing multiple frequency components. Starting from the first frequency component (i=1), the corresponding harmonic frequency band set is used, combined with the cable structural parameters, to calculate the cable's distributed parameters. Then, based on the cable's distributed parameters, the propagation coefficient and wave impedance are calculated; and the power source terminal impedance Z is obtained using the impedance scanning method. G and cable load end impedance Z R Using the propagation coefficient and wave impedance, and the source impedance Z... G and cable load end impedance Z R The frequency is calculated as ω. i The current distribution under the action of harmonics Then, the current distribution at different locations along the cable length is calculated in the spatial domain. The cable currents acting on each frequency component are superimposed (it can be understood that when i=1, the superposition result is the current distribution). (Itself), until i reaches n, at which point it is assumed that the cable current under the action of all frequency components has been superimposed, and thus the result is obtained. Search The location of the maximum cable current is the location of the maximum loss, thus allowing us to pinpoint the extreme point of harmonic loss.

[0139] Example 2:

[0140] Based on the same inventive concept, this invention also provides a cable loss extreme point identification system under broadband disturbance, as shown in the schematic diagram below. Figure 4 As shown, it includes:

[0141] The time-frequency transformation analysis module is used to perform time-frequency transformation analysis on the power detection parameters of the cable to be identified, and obtain frequency domain feature data containing multiple frequency components;

[0142] The cable parameter calculation module is used to calculate the cable parameters when each frequency component is applied, based on the cable structure of the cable to be identified.

[0143] The current distribution calculation module is used to calculate the cable current distribution under broadband harmonic environments based on frequency domain characteristic data and cable parameters, using the transmission line ripple model.

[0144] The loss extremum identification module is used to find the maximum value of cable current in the cable current distribution under broadband harmonic environment; based on the maximum value of cable current, the electromagnetic-thermal coupling model of transmission line is used to identify the location of the cable loss extremum.

[0145] In one specific implementation, the current distribution calculation module is specifically used for:

[0146] Based on the harmonic amplitude of each frequency component in the frequency characteristic data, the propagation coefficient and wave impedance in the cable parameters, the cable current distribution under broadband harmonic environment is calculated using the transmission line ripple model.

[0147] In one specific implementation, the transmission line ripple model satisfies the following formula:

[0148] in, This refers to the cable current distribution under broadband harmonic environments, U1(ω i ) is the amplitude of the i-th harmonic at the first end, Γ1(ω i Γ2(ω) is the reflection coefficient at the head end corresponding to the i-th harmonic; i Z is the reflection coefficient at the end corresponding to the i-th harmonic; G (ω i Z is the equivalent impedance of the component connected to the first terminal corresponding to the i-th harmonic; R (ω i ) is the equivalent impedance of the component connected to the end corresponding to the i-th harmonic; γ(ω) i Z is the propagation coefficient corresponding to the i-th harmonic; c (ω i ω is the wave impedance corresponding to the i-th harmonic. i is the frequency of the i-th harmonic, and x is the distance between the selected location and the beginning of the cable.

[0149] In one specific implementation, the transmission line electromagnetic-thermal coupling model introduces conductor loss and armor layer loss.

[0150] The electromagnetic-thermal coupling model of a transmission line satisfies the following formula:

[0151] Where W is the cable loss, W 1,i W is the conductor loss corresponding to the i-th harmonic. 2,i This represents the armor layer loss corresponding to the i-th harmonic, where i takes values ​​from 1 to n, and n is the total harmonic order. λ(ω) i ) is the armor layer loss factor corresponding to the i-th harmonic, I i R is the current corresponding to the i-th harmonic. ac (ω i ω is the AC resistance corresponding to the i-th harmonic. i It is the frequency of the i-th harmonic.

[0152] In one specific implementation, the cable parameters include propagation coefficient and wave impedance;

[0153] The cable parameter calculation module includes:

[0154] The distributed parameter calculation unit is used to calculate the resistance, inductance, capacitance, and conductance per unit length between conductors in the cable to be identified, based on the cable structure of the cable to be identified.

[0155] The impedance calculation unit is used to calculate the impedance per unit length based on the resistance and inductance per unit length between conductors in the cable to be identified.

[0156] Admittance calculation unit is used to calculate the admittance per unit length based on the capacitance and conductance per unit length between conductors in the cable to be identified;

[0157] The propagation coefficient calculation unit is used to calculate the propagation coefficient of the cable to be identified based on the product of impedance and admittance per unit length.

[0158] The wave impedance calculation unit is used to calculate the wave impedance of the cable to be identified based on the ratio of impedance to admittance per unit length.

[0159] In one specific implementation, the propagation coefficient of the cable to be identified satisfies the following formula:

[0160] Where γ is the propagation coefficient, Z0 is the impedance per unit length, Y0 is the admittance per unit length, R0 is the resistance per unit length between conductors, L0 is the inductance per unit length between conductors, C0 is the capacitance per unit length between conductors, G0 is the conductance per unit length between conductors, ω is the magnitude of the angular frequency, and j is the imaginary unit.

[0161] The wave impedance of the cable to be identified satisfies the following formula:

[0162] Among them, Z c Z0 is the wave impedance, Y0 is the impedance per unit length, R0 is the resistance per unit length between conductors, L0 is the inductance per unit length between conductors, C0 is the capacitance per unit length between conductors, G0 is the conductance per unit length between conductors, ω is the magnitude of the angular frequency, and j is the imaginary unit.

[0163] In one specific implementation, the distributed parameter calculation unit is specifically used for:

[0164] Calculate the resistance per unit length between conductors based on the angular frequency, conductor permeability, conductor conductivity, conductor radius, and inner diameter of the metal shielding layer in the cable structure.

[0165] Calculate the inductance per unit length between conductors based on the outer diameter of the metal shielding layer, the magnitude of the angular frequency, the magnitude of the conductor's magnetic permeability, the conductor's conductivity, and the radius of the conductor core in the cable structure.

[0166] Calculate the capacitance and conductance per unit length between conductors based on the complex permittivity of the dielectric material in the cable structure and the inner and outer radii of the dielectric material.

[0167] In one specific implementation, the resistance per unit length between conductors satisfies the following formula:

[0168] Where R0 is the resistance per unit length between conductors, ω is the angular frequency; μ is the magnetic permeability of the conductor; σ is the electrical conductivity of the conductor; r cu It is the radius of the conductor core; r sh It is the inner diameter of the metal shielding layer;

[0169] The inductance per unit length between conductors satisfies the following formula:

[0170] Where L0 is the inductance per unit length between conductors, ω is the angular frequency; μ is the permeability of the conductor; σ is the conductivity of the conductor; r cu It is the radius of the conductor core; r' sh It is the outer diameter of the metal shielding layer;

[0171] The capacitance per unit length between conductors satisfies the following formula:

[0172] Where C0 is the capacitance per unit length between conductors, ε k (ω) is the complex permittivity of the k-th dielectric layer; r k and r k+1 ω and j are the inner and outer radii of the k-th medium layer, respectively, where k takes values ​​from 1 to N, N is the total number of medium layers, ω is the magnitude of the angular frequency, j is the imaginary unit, and Im() is the function for finding the imaginary part.

[0173] The conductivity per unit length between conductors satisfies the following formula:

[0174] Where G0 is the conductance per unit length between conductors, ε k (ω) is the complex permittivity of the k-th dielectric layer; r k and r k+1 ω and j are the inner and outer radii of the k-th medium layer, respectively, where k takes values ​​from 1 to N, N is the total number of medium layers, ω is the angular frequency, j is the imaginary unit, and Re() is the function to find the real part.

[0175] Example 3:

[0176] like Figure 5As shown, the present invention also provides an electronic device, which may be a computer device, a microcontroller device, a smart mobile device, etc. The electronic device in this embodiment may include a processor, a memory, a transceiver component, etc. The memory, processor, and transceiver component are connected via a bus; the memory can be used to store executable programs, and an exemplary executable program may include instructions; the processor is used to execute the instructions stored in the memory. The memory can also be used to store data, which can be accessed and / or modified when instructions are executed.

[0177] The processor may be a Central Processing Unit (CPU), or it may be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, and it is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions in the storage medium to implement the corresponding method flow or corresponding function, so as to realize the steps of the cable loss extreme point identification method under broadband disturbance in the above embodiment.

[0178] Example 4:

[0179] Based on the same inventive concept, this invention also provides a readable storage medium, specifically an electronic device readable storage medium (Memory). This readable storage medium is a memory device within an electronic device used to store programs and data. It is understood that the storage medium here can include both built-in storage media within the electronic device and extended storage media supported by the electronic device. The storage medium provides storage space, which stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more executable programs (including program code). It should be noted that the storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device. Loading and executing one or more instructions stored in the storage medium by the processor can implement the steps of the cable loss extreme point identification method under broadband disturbance described in the above embodiments.

[0180] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0181] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0182] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0183] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0184] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation methods of the application, but these changes, modifications or equivalent substitutions are all within the scope of protection of the claims pending approval.

Claims

1. A method for identifying extreme points of cable loss under broadband disturbance, characterized in that, include: Time-frequency transformation analysis is performed on the power detection parameters of the cable to be identified to obtain frequency domain feature data containing multiple frequency components; Based on the cable structure of the cable to be identified, calculate the cable parameters when each frequency component is applied. Based on the frequency domain characteristic data and the cable parameters, the cable current distribution under broadband harmonic environment is calculated using the transmission line ripple model. Find the maximum cable current value in the cable current distribution under the broadband harmonic environment; based on the maximum cable current value, use the transmission line electromagnetic-thermal coupling model to identify the location of the extreme value of cable loss.

2. The method as described in claim 1, characterized in that, The step of calculating the cable current distribution under broadband harmonic environments based on the frequency domain characteristic data and the cable parameters using a transmission line ripple model includes: Based on the harmonic amplitude of each frequency component in the frequency characteristic data, the propagation coefficient and wave impedance in the cable parameters, the cable current distribution under broadband harmonic environment is calculated using the transmission line ripple model.

3. The method as described in claim 2, characterized in that, The transmission line ripple model satisfies the following formula: in, This refers to the cable current distribution under broadband harmonic environments, U1(ω i ) is the amplitude of the i-th harmonic at the first end, Γ1(ω i Γ2(ω) is the reflection coefficient at the head end corresponding to the i-th harmonic; i Z is the reflection coefficient at the end corresponding to the i-th harmonic; G (ω i Z is the equivalent impedance of the component connected to the first terminal corresponding to the i-th harmonic; R (ω i ) is the equivalent impedance of the component connected to the end corresponding to the i-th harmonic; γ(ω) i Z is the propagation coefficient corresponding to the i-th harmonic; c (ω i ω is the wave impedance corresponding to the i-th harmonic. i is the frequency of the i-th harmonic, x is the distance between the selected location and the beginning of the cable, i takes values ​​of 1, ..., n, and n is the total number of harmonics.

4. The method as described in claim 1, characterized in that, The electromagnetic-thermal coupling model of the transmission line introduces conductor loss and armor layer loss. The electromagnetic-thermal coupling model of the transmission line satisfies the following formula: Where W is the cable loss, W 1,i W is the conductor loss corresponding to the i-th harmonic. 2,i This represents the armor layer loss corresponding to the i-th harmonic, where i takes values ​​from 1 to n, and n is the total harmonic order. λ(ω) i ) is the armor layer loss factor corresponding to the i-th harmonic, I i R is the current corresponding to the i-th harmonic. ac (ω i ω is the AC resistance corresponding to the i-th harmonic. i It is the frequency of the i-th harmonic.

5. The method according to any one of claims 1-4, characterized in that, The cable parameters include propagation coefficient and wave impedance; The calculation of cable parameters for each frequency component based on the cable structure of the cable to be identified includes: Based on the cable structure of the cable to be identified, calculate the resistance, inductance, capacitance, and conductance per unit length between the conductors in the cable to be identified; Calculate the impedance per unit length based on the resistance and inductance per unit length between the conductors in the cable to be identified; Calculate the admittance per unit length based on the capacitance and conductance per unit length between the conductors in the cable to be identified; The propagation coefficient of the cable to be identified is calculated based on the product of the impedance and admittance per unit length. The wave impedance of the cable to be identified is calculated based on the ratio of impedance to admittance per unit length.

6. The method as described in claim 5, characterized in that, The propagation coefficient of the cable to be identified satisfies the following formula: Where γ is the propagation coefficient, Z0 is the impedance per unit length, Y0 is the admittance per unit length, R0 is the resistance per unit length between conductors, l0 is the inductance per unit length between conductors, C0 is the capacitance per unit length between conductors, G0 is the conductance per unit length between conductors, ω is the magnitude of the angular frequency, and j is the imaginary unit. The wave impedance of the cable to be identified satisfies the following formula: Among them, Z c Z0 is the wave impedance, Y0 is the impedance per unit length, R0 is the resistance per unit length between conductors, l0 is the inductance per unit length between conductors, C0 is the capacitance per unit length between conductors, G0 is the conductance per unit length between conductors, ω is the magnitude of the angular frequency, and j is the imaginary unit.

7. The method as described in claim 5, characterized in that, The step of calculating the resistance, inductance, capacitance, and conductance per unit length between conductors in the cable to be identified, based on the cable structure of the cable to be identified, includes: Calculate the resistance per unit length between conductors based on the angular frequency, conductor permeability, conductor conductivity, conductor radius, and inner diameter of the metal shielding layer in the cable structure. Calculate the inductance per unit length between conductors based on the outer diameter of the metal shielding layer in the cable structure, the magnitude of the angular frequency, the magnitude of the conductor permeability, the conductor conductivity, and the radius of the conductor core. Based on the complex permittivity of the medium in the cable structure and the inner and outer radii of the medium, calculate the capacitance and conductance per unit length between the conductors.

8. The method as described in claim 7, characterized in that, The resistance per unit length between the conductors satisfies the following formula: Where R0 is the resistance per unit length between conductors, ω is the angular frequency; μ is the magnetic permeability of the conductor; σ is the electrical conductivity of the conductor; r cu It is the radius of the conductor core; r sh It is the inner diameter of the metal shielding layer; The inductance per unit length between the conductors satisfies the following formula: Where L0 is the inductance per unit length between conductors, ω is the angular frequency; μ is the permeability of the conductor; σ is the conductivity of the conductor; r cu It is the radius of the conductor core; r' sh is the outer diameter of the metal shielding layer, and ln() is the natural logarithm function; The capacitance per unit length between the conductors satisfies the following formula: Where C0 is the capacitance per unit length between conductors, ε k (ω) is the complex permittivity of the k-th dielectric layer; r k and r k+1 ω and j are the inner and outer radii of the k-th medium layer, respectively, where k takes values ​​from 1 to N, N is the total number of medium layers, ω is the magnitude of the angular frequency, j is the imaginary unit, and Im() is the function for finding the imaginary part. The conductivity per unit length between the conductors satisfies the following formula: Where G0 is the conductance per unit length between conductors, ε k (ω) is the complex permittivity of the k-th dielectric layer; r k and r k+1 ω and j are the inner and outer radii of the k-th medium layer, respectively, where k takes values ​​from 1 to N, N is the total number of medium layers, ω is the angular frequency, j is the imaginary unit, and Re() is the function to find the real part.

9. A system for identifying extreme points of cable loss under broadband disturbance, characterized in that, include: The time-frequency transformation analysis module is used to perform time-frequency transformation analysis on the power detection parameters of the cable to be identified, and obtain frequency domain feature data containing multiple frequency components; The cable parameter calculation module is used to calculate the cable parameters when each frequency component is applied, based on the cable structure of the cable to be identified. The current distribution calculation module is used to calculate the cable current distribution under broadband harmonic environment based on the frequency domain characteristic data and the cable parameters, using the transmission line ripple model. The loss extreme value identification module is used to find the maximum value of cable current in the cable current distribution under the broadband harmonic environment; based on the maximum value of cable current, the location of the cable loss extreme value is identified using the transmission line electromagnetic-thermal coupling model.

10. The system as described in claim 9, characterized in that, The current distribution calculation module is specifically used for: Based on the harmonic amplitude of each frequency component in the frequency characteristic data, the propagation coefficient and wave impedance in the cable parameters, the cable current distribution under broadband harmonic environment is calculated using the transmission line ripple model.

11. The system as claimed in claim 10, characterized in that, The transmission line ripple model satisfies the following formula: in, This refers to the cable current distribution under broadband harmonic environments, U1(ω i ) is the amplitude of the i-th harmonic at the first end, Γ1(ω i Γ2(ω) is the reflection coefficient at the head end corresponding to the i-th harmonic; i Z is the reflection coefficient at the end corresponding to the i-th harmonic; G (ω i Z is the equivalent impedance of the component connected to the first terminal corresponding to the i-th harmonic; R (ω i ) is the equivalent impedance of the component connected to the end corresponding to the i-th harmonic; γ(ω) i Z is the propagation coefficient corresponding to the i-th harmonic; c (ω i ω is the wave impedance corresponding to the i-th harmonic. i is the frequency of the i-th harmonic, x is the distance between the selected location and the beginning of the cable, i takes values ​​of 1, ..., n, and n is the total number of harmonics.

12. The system as described in claim 9, characterized in that, The electromagnetic-thermal coupling model of the transmission line introduces conductor loss and armor layer loss. The electromagnetic-thermal coupling model of the transmission line satisfies the following formula: Where W is the cable loss, W 1,i W is the conductor loss corresponding to the i-th harmonic. 2,i This represents the armor layer loss corresponding to the i-th harmonic, where i takes values ​​from 1 to n, and n is the total harmonic order. λ(ω) i ) is the armor layer loss factor corresponding to the i-th harmonic, I i R is the current corresponding to the i-th harmonic. ac (ω i ω is the AC resistance corresponding to the i-th harmonic. i It is the frequency of the i-th harmonic.

13. The system according to any one of claims 9-12, characterized in that, The cable parameters include propagation coefficient and wave impedance; The cable parameter calculation module includes: The distributed parameter calculation unit is used to calculate the resistance, inductance, capacitance and conductance per unit length between conductors in the cable to be identified based on the cable structure of the cable to be identified. The impedance calculation unit is used to calculate the impedance per unit length based on the resistance and inductance per unit length between conductors in the cable to be identified. The admittance calculation unit is used to calculate the admittance per unit length based on the capacitance and conductance per unit length between conductors in the cable to be identified. The propagation coefficient calculation unit is used to calculate the propagation coefficient of the cable to be identified based on the product of the impedance and admittance per unit length. The wave impedance calculation unit is used to calculate the wave impedance of the cable to be identified based on the ratio of impedance to admittance per unit length.

14. The system as described in claim 13, characterized in that, The propagation coefficient of the cable to be identified satisfies the following formula: Where γ is the propagation coefficient, Z0 is the impedance per unit length, Y0 is the admittance per unit length, R0 is the resistance per unit length between conductors, l0 is the inductance per unit length between conductors, C0 is the capacitance per unit length between conductors, G0 is the conductance per unit length between conductors, ω is the magnitude of the angular frequency, and j is the imaginary unit. The wave impedance of the cable to be identified satisfies the following formula: Among them, Z c Z0 is the wave impedance, Y0 is the impedance per unit length, R0 is the resistance per unit length between conductors, l0 is the inductance per unit length between conductors, C0 is the capacitance per unit length between conductors, G0 is the conductance per unit length between conductors, ω is the magnitude of the angular frequency, and j is the imaginary unit.

15. The system as described in claim 13, characterized in that, The distributed parameter calculation unit is specifically used for: Calculate the resistance per unit length between conductors based on the angular frequency, conductor permeability, conductor conductivity, conductor radius, and inner diameter of the metal shielding layer in the cable structure. Calculate the inductance per unit length between conductors based on the outer diameter of the metal shielding layer in the cable structure, the magnitude of the angular frequency, the magnitude of the conductor permeability, the conductor conductivity, and the radius of the conductor core. Based on the complex permittivity of the medium in the cable structure and the inner and outer radii of the medium, calculate the capacitance and conductance per unit length between the conductors.

16. The system as described in claim 15, characterized in that, The resistance per unit length between the conductors satisfies the following formula: Where R0 is the resistance per unit length between conductors, ω is the angular frequency; μ is the magnetic permeability of the conductor; σ is the electrical conductivity of the conductor; r cu It is the radius of the conductor core; r sh It is the inner diameter of the metal shielding layer; The inductance per unit length between the conductors satisfies the following formula: Where L0 is the inductance per unit length between conductors, ω is the angular frequency; μ is the permeability of the conductor; σ is the conductivity of the conductor; r cu It is the radius of the conductor core; r' sh is the outer diameter of the metal shielding layer, and ln() is the natural logarithm function; The capacitance per unit length between the conductors satisfies the following formula: Where C0 is the capacitance per unit length between conductors, ε k (ω) is the complex permittivity of the k-th dielectric layer; r k and r k+1 ω and j are the inner and outer radii of the k-th medium layer, respectively, where k takes values ​​from 1 to N, N is the total number of medium layers, ω is the magnitude of the angular frequency, j is the imaginary unit, and Im() is the function for finding the imaginary part. The conductivity per unit length between the conductors satisfies the following formula: Where G0 is the conductance per unit length between conductors, ε k (ω) is the complex permittivity of the k-th dielectric layer; r k and r k+1 ω and j are the inner and outer radii of the k-th medium layer, respectively, where k takes values ​​from 1 to N, N is the total number of medium layers, ω is the angular frequency, j is the imaginary unit, and Re() is the function to find the real part.

17. An electronic device, characterized in that, include: At least one processor and memory; The memory and processor are connected via a bus; The memory is used to store one or more programs; When the one or more programs are executed by the at least one processor, the method for identifying extreme points of cable loss under broadband disturbance as described in any one of claims 1 to 8 is implemented.

18. A readable storage medium, characterized in that, It contains an execution program, which, when executed, implements the cable loss extreme point identification method under broadband disturbance as described in any one of claims 1 to 8.

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