Frequency response modeling method of high voltage cable joint considering broadband characteristics of semi-conductive shielding layer

Abstract

The present invention provides a frequency response modeling method for a high-voltage cable joint considering the broadband characteristics of a semi-conductive shielding layer. The method measures the complex dielectric constants of the inner and outer semi-conductive shielding layers of the cable joint within a preset frequency range, and fits the relationship between the complex dielectric constant and the frequency, thereby obtaining a complex dielectric constant equation for the inner and outer semi-conductive shielding layers of the cable joint; according to the internal structural differences of the cable joint, the cable joint is subjected to segmented equivalent processing, and a distributed parameter equivalent circuit considering the crimping of the cable joint conductor is established according to the segmented results; the frequency domain response characteristic parameters of the cable joint are calculated through the complex dielectric constant equation, including characteristic impedance, wave velocity and propagation coefficient, transfer matrix and transmission coefficient, so that the propagation characteristics of different center frequency signals in the cable joint and the frequency dependence characteristics of the cable joint can be analyzed according to the frequency domain response characteristic parameters.

Description

Technical Field

[0001] The present invention relates to the field of high voltage and insulation technology, and in particular to a frequency response modeling method for a high voltage cable joint taking into account the broadband characteristics of a semi-conductive shielding layer. Background Art

[0002] With the rapid development of China's megacities, the number of power cables in urban power grids has increased rapidly due to their excellent electrical performance. The good and stable normal operation of dense power cables in cities is directly related to the safety and reliability of urban power grids.

[0003] Under normal operation of cables, they are often invaded by transient overvoltages. Fourier spectrum analysis of different types of overvoltages found that the main frequency band of the operating wave is distributed in the range of several kHz, the transient component of the lightning wave is concentrated below 1MHz, and the main frequency band of the very fast transient overvoltage VFTO is distributed in the range of several MHz to tens of MHz. In the case of cable faults, it is necessary to use a swept frequency signal to locate the fault point, and the incident signal termination frequency is as high as 100MHz. It can be seen that under different working conditions, the cable will be invaded by waves of several kHz to hundreds of MHz, which adds complexity to the operation evaluation of the cable.

[0004] Cable joints are the weak point of cable systems, so the study of their broadband response characteristics in different frequency ranges is of great significance. Studies have shown that the inner and outer semi-conductive shielding layers of cable joints have strong frequency dependence characteristics, which significantly affect the wave propagation process. However, the existing technology does not consider the frequency-varying characteristics of the inner and outer semi-conductive shielding layers, and thus cannot accurately describe the frequency-varying characteristics of the cable joint frequency response characteristics. Summary of the invention

[0005] The present invention provides a high-voltage cable joint frequency response modeling method considering the broadband characteristics of a semi-conductive shielding layer, which can consider the frequency variation characteristics of the inner and outer semi-conductive shielding layers of the cable joint and analyze the frequency response characteristics of the cable joint.

[0006] The present invention provides a method for modeling a high-voltage cable joint frequency response taking into account the broadband characteristics of a semi-conductive shielding layer, comprising:

[0007] Obtaining a first complex dielectric constant and a second complex dielectric constant of a pretreated inner semiconductive shielding layer sample and an outer semiconductive shielding layer sample of a cable joint measured within a preset frequency range;

[0008] Fitting the relationship between the first complex dielectric constant and the second complex dielectric constant and the frequency respectively, to obtain a first complex dielectric constant equation corresponding to the inner semi-conductive shielding layer sample and a second complex dielectric constant equation corresponding to the outer semi-conductive shielding layer sample;

[0009] According to the internal structural differences of the cable joint, the cable joint is subjected to segmented equivalent processing, and a distributed parameter equivalent circuit considering the crimping of the cable joint conductor is established according to the segmented results; wherein the distributed parameter equivalent circuit includes a plurality of unit circuits;

[0010] Considering the structure and material properties of each unit after segmentation, combining the first complex dielectric constant equation and the second complex dielectric constant equation, calculating the impedance and admittance of each unit circuit as it changes with frequency;

[0011] According to the impedance and admittance of each unit circuit that varies with frequency, the characteristic impedance, wave velocity and propagation coefficient of the cable joint along the axial length at different frequencies are calculated, and according to the characteristic impedance and the propagation coefficient, the transfer matrix and transmission coefficient of the cable joint are calculated.

[0012] As an improvement of the above scheme, according to the difference in the internal structure of the cable joint, the cable joint is subjected to segmented equivalent processing, and a distributed parameter equivalent circuit considering the crimping of the cable joint conductor is established according to the segmented result, specifically including:

[0013] According to the difference in the internal structure of the cable connector and the axially symmetrical characteristics of the cable connector, the left half axis of the cable connector is divided into a plurality of units connected in series; wherein, if the unit is a non-crimping section of the cable connector, the unit is a first unit; and if the unit is a crimping section of the cable connector, the unit is a second unit;

[0014] Each first unit circuit corresponding to each first unit and a second unit circuit corresponding to the second unit are established to establish a distributed parameter equivalent circuit considering the crimping of the cable joint conductor.

[0015] As an improvement of the above scheme, the structure and material properties of each unit after segmentation are considered, and the impedance and admittance of each unit circuit varying with frequency are calculated by combining the first complex dielectric constant equation and the second complex dielectric constant equation, which specifically includes:

[0016] For each of the unit circuits, calculating the distributed resistance and distributed inductance of the unit circuit that vary with frequency, and calculating the impedance of the unit circuit that varies with frequency based on the distributed resistance and the distributed inductance;

[0017] The frequency-varying admittance of each material structure layer in the unit circuit is calculated, and the frequency-varying admittances of all material structure layers are calculated in parallel to obtain the frequency-varying admittance of the unit circuit; wherein the material structure layers contained in the unit circuit include a main insulating layer and a semiconductive resistive water layer, and also include at least one of an inner semiconductive shielding layer and an outer semiconductive shielding layer, and the frequency-varying admittance of the inner semiconductive shielding layer is calculated according to the first complex dielectric constant equation, and the frequency-varying admittance of the outer semiconductive shielding layer is calculated according to the second complex dielectric constant equation.

[0018] As an improvement to the above solution, the distributed resistance of the unit circuit that varies with frequency is calculated by the following steps:

[0019] When the unit circuit is a first unit circuit, the distributed resistance of the first unit circuit that varies with frequency is calculated according to the following formula:

[0020]

[0021] When the unit circuit is a second unit circuit, the distributed resistance of the second unit circuit that varies with frequency is calculated according to the following formula:

[0022]

[0023] a′=a″+△d

[0024]

[0025] Wherein, R(ω) is the distributed resistance of the first unit, ω is the angular frequency, a1 is the outer radius of the inner conductor, a2 is the inner radius of the outer conductor, ρ1 is the resistivity of the inner conductor, ρ2 is the resistivity of the outer conductor, μ0 is the magnetic permeability of vacuum, R'(ω) is the distributed resistance of the second unit, K is the contact coefficient, a' is the conductor radius of the cable body, a" is the radius of the conductor of the crimping section of the cable connector, ρ' is the resistivity of the normal conductor, ρ" is the resistivity of the conductor of the crimping section of the cable connector, △d is the thickness of the crimping section of the cable connector, l is the length of the first unit circuit, and l' is the length of the second unit circuit.

[0026] As an improvement of the above solution, the distributed inductance of the unit circuit is obtained by the following steps:

[0027] When the unit circuit is a first unit circuit, the distributed inductance of the first unit circuit is calculated according to the following formula:

[0028]

[0029] When the unit circuit is a second unit circuit, the distributed inductance of the second unit circuit is calculated according to the following formula:

[0030]

[0031] Wherein, L(ω) is the distributed inductance of the first unit circuit, ω is the angular frequency, a1 is the radius of the cable body conductor, a2 is the inner radius of the outer conductor, μ0 is the vacuum permeability, ρ1 is the resistivity of the inner conductor, ρ2 is the resistivity of the outer conductor, L'(ω) is the distributed inductance of the second unit, ρ″ is the resistivity of the conductor of the crimping section of the cable connector, a″ is the radius of the conductor of the crimping section of the cable connector, Y is the axial length of the crimping section of the cable connector, l is the length of the first unit circuit, and l' is the length of the second unit circuit.

[0032] As an improvement of the above solution, the frequency-varying admittance of the inner semi-conductive shielding layer is calculated according to the first complex dielectric constant equation, and the frequency-varying admittance of the outer semi-conductive shielding layer is calculated according to the second complex dielectric constant equation, specifically:

[0033] The admittance of the inner semi-conductive shield is calculated according to the following formula:

[0034]

[0035] The admittance of the outer semi-conductive shield is calculated according to the following formula:

[0036] Where Y1(ω) is the admittance of the inner semi-conductive shielding layer, ω is the angular frequency, ε0 ​​is the vacuum dielectric constant, is the first complex dielectric constant equation, r o1 is the outer radius of the inner semi-conductive shield, r i1 is the inner radius of the inner semi-conductive shielding layer, Y2(ω) is the admittance of the outer semi-conductive shielding layer, is the second complex dielectric constant equation, r o2 is the outer radius of the outer semi-conductive shield, r i2 is the inner radius of the outer semi-conductive shield.

[0037] As an improvement to the above solution, the transfer matrix of the cable joint is calculated by the following steps:

[0038] The cable connector is equivalent to a plurality of coaxial series-connected units, and according to the propagation coefficient, axial length and characteristic impedance corresponding to each unit, the transfer matrix characteristic parameters of each unit are calculated;

[0039] The product of the transfer matrix characteristic parameters of all the units is calculated to obtain the transfer matrix of the cable joint.

[0040] As an improvement of the above solution, the transfer matrix characteristic parameters of the unit are calculated by the following formula:

[0041]

[0042] in, represents the characteristic parameters of the transfer matrix of the i-th unit, γ i is the propagation coefficient corresponding to the i-th unit circuit in the equivalent circuit, l i is the axial length of the i-th unit, Z oi is the characteristic impedance corresponding to the i-th unit circuit in the equivalent circuit.

[0043] As an improvement of the above solution, the transmission coefficient of the cable connector is calculated by the following formula:

[0044]

[0045] Among them, T j is the transmission coefficient of the cable joint, Z o is the characteristic impedance of the cable connector, and A, B, C, and D are all elements in the transfer matrix of the cable connector.

[0046] Compared with the prior art, the embodiment of the present invention provides a high-voltage cable joint frequency response modeling method that considers the broadband characteristics of the semi-conductive shielding layer. The complex dielectric constant of the inner and outer semi-conductive shielding layers of the cable joint is measured within a preset frequency range, and the relationship between the complex dielectric constant and the frequency is fitted to obtain the complex dielectric constant equation of the inner and outer semi-conductive shielding layers of the cable joint; according to the internal structure difference of the cable joint, the cable joint is subjected to segmented equivalent processing, and a distributed parameter equivalent circuit considering the crimping of the cable joint conductor is established according to the segmented result; the frequency domain response characteristic parameters of the cable joint are calculated by the complex dielectric constant equation, including characteristic impedance, wave velocity and propagation coefficient, transfer matrix and transmission coefficient, which can consider the frequency variation characteristics of the inner and outer semi-conductive shielding layers of the cable joint, and accurately analyze the frequency response characteristics of the cable joint, so that the propagation characteristics of different center frequency signals in the cable joint and the frequency dependence characteristics of the cable joint can be analyzed according to the frequency domain response characteristic parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a flow chart of a method for modeling a high-voltage cable connector frequency response taking into account the broadband characteristics of a semi-conductive shielding layer provided by an embodiment of the present invention;

[0048] Figure 2 It is a schematic diagram of the impedance measurement principle provided by the present invention;

[0049] Figure 3 It is a structural schematic diagram of the cable connector provided by the present invention;

[0050] Figure 4 It is a schematic diagram of the structure of the segmented left half-shaft joint of the cable joint provided by the present invention;

[0051] Figure 5 It is an equivalent distributed parameter model of each unit of the cable connector provided by the present invention;

[0052] Figure 6 It is a curve diagram of the parameters of the inner and outer semi-conductive shielding layers of the cable connector provided by the present invention as a function of frequency;

[0053] Figure 7 It is a curve diagram of the change of the characteristic impedance of the cable joint along the axial direction at a frequency of 1 MHz provided by the present invention;

[0054] Figure 8 It is a curve diagram of the change of the characteristic impedance of the cable connector along the axial direction at different frequencies provided by the present invention;

[0055] Fig. 9 It is a curve diagram of the change of the amplitude of the transmission coefficient of the cable joint provided by the present invention within the range of 1 MHz-100 MHz. DETAILED DESCRIPTION

[0056] 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.

[0057] See also Figure 1 , Figure 1 It is a flow chart of a method for frequency response modeling of a high-voltage cable connector taking into account the broadband characteristics of a semi-conductive shielding layer provided in an embodiment of the present invention.

[0058] The method for modeling the frequency response of a high-voltage cable connector taking into account the broadband characteristics of a semi-conductive shielding layer provided in an embodiment of the present invention comprises steps S11 to S15:

[0059] Step S11, obtaining the first complex dielectric constant and the second complex dielectric constant of the pre-treated inner semi-conductive shielding layer sample and the outer semi-conductive shielding layer sample of the cable connector measured within a preset frequency range.

[0060] In the specific implementation, the inner semi-conductive shielding layer and the outer semi-conductive shielding layer of the cable connector are sampled respectively to obtain the inner semi-conductive shielding layer sample and the outer semi-conductive shielding layer sample. Exemplarily, the specifications of the inner semi-conductive shielding layer sample and the outer semi-conductive shielding layer sample can be circular sheets with a diameter of 30 mm and a thickness of 1 mm. Of course, the samples can also be processed into other specifications as long as they meet the dielectric constant measurement requirements.

[0061] Specifically, after obtaining the inner semi-conductive shielding layer sample and the outer semi-conductive shielding layer sample, the inner semi-conductive shielding layer sample and the outer semi-conductive shielding layer sample are further pre-treated, and the pre-treatment process can be: placing the inner semi-conductive shielding layer sample and the outer semi-conductive shielding layer sample in a drying dish for 24 hours, and then taking them out to spray gold on both sides of the inner semi-conductive shielding layer sample and the outer semi-conductive shielding layer sample. The purpose of pre-treating the inner semi-conductive shielding layer sample and the outer semi-conductive shielding layer sample is to remove moisture from the sample surface as much as possible. Without this step, the presence of moisture may cause the measured dielectric constant value to be too low; the purpose of spraying gold on both sides of the sample is to eliminate the influence of the sample surface roughness on the electric field distribution, make the test electric field as uniform as possible, and improve the measurement accuracy.

[0062] Exemplarily, the first complex dielectric constant and the second complex dielectric constant obtained by measuring the inner semiconductive shielding layer sample and the outer semiconductive shielding layer sample of the pretreated cable joint within a preset frequency range can be measured by an impedance measurement method, and the preset range can be 1kHz to 100MHz.

[0063] See also Figure 2 , Figure 2 A schematic diagram of the impedance measurement principle is shown. Figure 2 The amplitude and phase of the voltage signal U1 flowing through the inner semi-conductive shielding layer sample or the outer semi-conductive shielding layer sample can be collected by the vector voltage analyzer 1; the current signal I flowing through the inner semi-conductive shielding layer sample or the outer semi-conductive shielding layer sample can be collected by the vector voltage analyzer 1. S Supplied by the inverting input of the operational amplifier and through the adjustable resistor R X It is converted into a voltage signal U2 and collected by a vector voltage analyzer 2; R0 is a protective resistor; the sine signal generator and the vector voltage analyzer are both connected to a computer for synchronous calculation of frequency and phase.

[0064] Among them, the current signal I flowing through the inner semi-conductive shielding layer sample or the outer semi-conductive shielding layer sample S The relationship with the voltage signal U2 is:

[0065] Under different frequency voltages, according to the voltage signal U1 and current signal I flowing through the inner semi-conductive shielding layer sample or the outer semi-conductive shielding layer sample S The complex impedance of the inner semi-conductive shield sample or the outer semi-conductive shield sample can be calculated:

[0066]

[0067] In the formula, and The measured voltage signal U1 flowing through the test sample and the calculated current signal I flowing through the test sample are S plural form of .

[0068] Therefore, the complex dielectric constant of the inner semi-conductive shielding layer sample or the outer semi-conductive shielding layer sample can be expressed as:

[0069]

[0070] Wherein, ε' is the real part of the complex dielectric constant, which is proportional to the reactive current in the medium and has the same meaning as the dielectric constant of the medium. ε" is the imaginary part of the complex dielectric constant, which is usually used to represent the energy loss caused by relaxation polarization in the medium and becomes a loss factor. C0 is the no-load capacitance of the inner semi-conductive shielding layer sample or the outer semi-conductive shielding layer sample, which can be calculated based on the parameters of the inner semi-conductive shielding layer sample or the outer semi-conductive shielding layer sample. ω is the angular frequency of the AC voltage.

[0071] Step S12, respectively fitting the variation relationship between the first complex dielectric constant and the second complex dielectric constant and the frequency, to obtain a first complex dielectric constant equation corresponding to the inner semi-conductive shielding layer sample and a second complex dielectric constant equation corresponding to the outer semi-conductive shielding layer sample.

[0072] In some embodiments, the first complex dielectric constant equation corresponding to the inner semi-conductive shielding layer sample and the second complex dielectric constant equation corresponding to the outer semi-conductive shielding layer sample can be obtained by fitting the following formula:

[0073]

[0074] Where τ1 and τ2 are relaxation times, σ dc is the DC conductivity, ε ∞ is the high-frequency component of the dielectric constant, A1, A2, α1, α2 are fitting constants, and ε0 is the vacuum dielectric constant, which is 8.854187817×10 -12 F / m.

[0075] It can be understood that the first complex dielectric constant equation in the embodiment of the present invention is used to describe the relationship between the complex dielectric constant of the inner semi-conductive shielding layer sample and the frequency, and the second complex dielectric constant equation is used to describe the relationship between the complex dielectric constant of the outer semi-conductive shielding layer sample and the frequency.

[0076] Step S13, performing segmented equivalent processing on the cable connector according to differences in its internal structure, and establishing a distributed parameter equivalent circuit considering crimping of the cable connector conductor according to the segmented results; wherein the distributed parameter equivalent circuit includes a plurality of unit circuits.

[0077] See also Figure 3 , Figure 3 The schematic diagram of the structure of the cable connector is shown. It can be seen that the cable connector contains multiple layers of materials, such as an outer semi-conductive shielding layer, an XPLE main insulation layer and an inner semi-conductive shielding layer. In specific implementation, the cable connector is divided into multiple units according to the changes in the internal structure of the cable connector along the axial direction. The basis for segmentation is that the structure and material of each unit are as uniform as possible. For example, when it is found that the structure of a certain point is significantly different from the structure before this point, the point is used as the dividing point to divide the cable connector. As an example, Figure 4 The schematic diagram of the structure of the cable joint after the half-axle joint is segmented is shown. Figure 4 In FIG. 1 , it can be seen that the left half axis of the cable connector is divided into segments a to f, and a unit circuit corresponding to each unit is established, thereby obtaining the following: Figure 5 The equivalent distributed parameter model of each unit of the cable joint.

[0078] Step S14, considering the structure and material characteristics of each unit after segmentation, combining the first complex dielectric constant equation and the second complex dielectric constant equation, calculate the impedance and admittance of each unit circuit that varies with frequency.

[0079] Step S15, calculating the characteristic impedance, wave velocity and propagation coefficient of the cable connector along the axial length at different frequencies according to the impedance and admittance of each unit circuit that vary with frequency, and calculating the transfer matrix and transmission coefficient of the cable connector according to the characteristic impedance and the propagation coefficient.

[0080] In an optional implementation, the step S13 of "performing segmented equivalent processing on the cable connector according to the internal structural differences of the cable connector, and establishing a distributed parameter equivalent circuit considering the crimping of the cable connector conductor according to the segmentation results" specifically includes:

[0081] According to the difference in the internal structure of the cable connector and the axially symmetrical characteristics of the cable connector, the left half axis of the cable connector is divided into a plurality of units connected in series; wherein, if the unit is a non-crimping section of the cable connector, the unit is a first unit; and if the unit is a crimping section of the cable connector, the unit is a second unit;

[0082] Each first unit circuit corresponding to each first unit and a second unit circuit corresponding to the second unit are established to establish a distributed parameter equivalent circuit considering the crimping of the cable joint conductor.

[0083] In the embodiment of the present invention, considering that the cable joint has contact resistance at the conductor connection due to crimping, the contact resistance may cause changes in the radius and conductivity of the cable core. Therefore, it is necessary to distinguish the crimped section from other non-crimped sections, define the unit of the crimped section as the first unit, and define the unit of the non-crimped section as the second unit.

[0084] Specifically, the cable joint has the characteristic of being axially symmetrical. To reduce the amount of calculation, the left half shaft or the right half shaft portion can be taken and the left half shaft or the right half shaft portion can be equivalently segmented to obtain multiple units, wherein the crimping section includes the leftmost section and the rightmost section located at the cable joint. As an example, Figure 4 The f section in is the crimping section, then a~g are the first units, and f is the second unit.

[0085] In an optional implementation, the step S14 "considering the structure and material properties of each unit after segmentation, combining the first complex dielectric constant equation and the second complex dielectric constant equation, calculating the impedance and admittance of each unit circuit that varies with frequency" specifically includes S141-S142:

[0086] Step S141, for each of the unit circuits, calculating the distributed resistance and distributed inductance of the unit circuit that vary with frequency, and calculating the impedance of the unit circuit that varies with frequency based on the distributed resistance and the distributed inductance;

[0087] S142, calculating the frequency-varying admittance of each material structure layer in the unit circuit, and calculating the frequency-varying admittances of all material structure layers in parallel to obtain the frequency-varying admittance of the unit circuit; wherein the material structure layers contained in the unit circuit include a main insulating layer and a semi-conductive resistive water layer, and also include at least one of an inner semi-conductive shielding layer and an outer semi-conductive shielding layer, and the frequency-varying admittance of the inner semi-conductive shielding layer is calculated based on the first complex dielectric constant equation, and the frequency-varying admittance of the outer semi-conductive shielding layer is calculated based on the second complex dielectric constant equation.

[0088] In one implementation, in step S141, the distributed resistance of the unit circuit that varies with frequency is calculated by the following steps:

[0089] When the unit circuit is a first unit circuit, the distributed resistance of the first unit circuit that varies with frequency is calculated according to the following formula:

[0090]

[0091] When the unit circuit is a second unit circuit, the distributed resistance of the second unit circuit that varies with frequency is calculated according to the following formula:

[0092]

[0093] a′=a″+△d

[0094]

[0095] Wherein, R(ω) is the distributed resistance of the first unit, ω is the angular frequency, a1 is the outer radius of the inner conductor, a2 is the inner radius of the outer conductor, ρ1 is the resistivity of the inner conductor, ρ2 is the resistivity of the outer conductor, μ0 is the magnetic permeability of vacuum, R'(ω) is the distributed resistance of the second unit, K is the contact coefficient, a' is the conductor radius of the cable body, a" is the radius of the conductor of the crimping section of the cable connector, ρ' is the resistivity of the normal conductor, ρ" is the resistivity of the conductor of the crimping section of the cable connector, △d is the thickness of the crimping section of the cable connector, l is the length of the first unit circuit, and l' is the length of the second unit circuit.

[0096] It is worth noting that the embodiment of the present invention takes into account that due to crimping, the cable joint will have contact resistance at the conductor connection point, and the contact resistance will cause the radius and conductivity of the cable core to change. Therefore, in order to accurately calculate the size of the contact resistance of the crimping section of the cable joint, for the second unit, such as Figure 4 For the g segment in , the contact coefficient K is considered to be added to measure the change of the resistance value of this segment, so that the resistance value of the second unit can be accurately calculated, and then the impedance value of the second unit can be accurately calculated.

[0097] In one implementation, in step S141, the distributed inductance of the unit circuit is obtained by the following steps:

[0098] When the unit circuit is a first unit circuit, the distributed inductance of the first unit circuit is calculated according to the following formula:

[0099]

[0100] When the unit circuit is a second unit circuit, the distributed inductance of the second unit circuit is calculated according to the following formula:

[0101]

[0102] Wherein, L(ω) is the distributed inductance of the first unit circuit, ω is the angular frequency, a1 is the radius of the cable body conductor, a2 is the inner radius of the outer conductor, μ0 is the vacuum permeability, ρ1 is the resistivity of the inner conductor, ρ2 is the resistivity of the outer conductor, L'(ω) is the distributed inductance of the second unit, ρ″ is the resistivity of the conductor of the crimping section of the cable connector, a″ is the radius of the conductor of the crimping section of the cable connector, Y is the axial length of the crimping section of the cable connector, l is the length of the first unit circuit, and l' is the length of the second unit circuit.

[0103] In an embodiment of the present invention, the distributed inductance of each unit circuit is composed of the self-inductance of the inner conductor, the self-inductance of the outer conductor, and the mutual inductance between the inner conductor and the outer conductor. For the non-crimped section of the cable connector, that is, the first unit, it can be equivalent to an infinitely long straight conductor for calculation, and the self-inductance of the inner conductor, the self-inductance of the outer conductor, and the mutual inductance between the inner conductor and the outer conductor can be accumulated during the calculation. As for the circuit connector crimping section, that is, the second unit, since the length of the cable connector crimping section is relatively short and is not much different from the outer diameter of the copper shielding layer of the cable connector, it cannot be assumed to be an infinitely long straight conductor for calculation. Therefore, considering the cable crimping section as a non-infinitely long conductor, its inductance calculation is corrected. Since the inductance value of the cable crimping section, that is, the corresponding area, is not only affected by the magnetic flux generated by the cable crimping section, but also by the magnetic flux generated by the semi-infinite conductors on both sides, the conductivity change at the joint caused by the cable crimping defect can be ignored in the calculation process. The entire cable line is calculated as a uniform infinite straight conductor, and then the difference between the magnetic flux of the crimping section and the normal cable core of the same length is subtracted to obtain the total magnetic flux of the area, and then the inductance value is solved.

[0104] From the above, the distributed inductance of each unit after the cable joint is segmented can be obtained, and then the inductance value of the circuit joint as a whole can be calculated. Since the inductance value of each unit is equivalent to a parallel structure, the calculation is based on the formula (Here L1 and L2 refer to the distributed inductance of each unit circuit), and the overall inductance value of the cable connector can be obtained.

[0105] Furthermore, the impedance of the unit circuit that varies with frequency is calculated by the following formula:

[0106] Z=R+jωL

[0107] Wherein, L is the distributed resistance of each unit circuit, and L is the distributed inductance of each unit circuit. When the unit circuit is the first unit circuit, L is the distributed inductance L(ω) of the first unit circuit, and when the unit circuit is the second unit circuit, L is the distributed inductance L'(ω) of the second unit circuit.

[0108] In one embodiment, the step S142 "calculates the frequency-varying admittance of each material structure layer in the unit circuit, and calculates the frequency-varying admittances of all material structure layers in parallel to obtain the frequency-varying admittance of the unit circuit; wherein the material structure layers contained in the unit circuit include a main insulating layer and a semiconductive resistive water layer, and also include at least one of an inner semiconductive shielding layer and an outer semiconductive shielding layer", that is, the frequency-varying admittance of the unit circuit is calculated according to the following formula:

[0109]

[0110] Among them, Y i is the admittance of the material structure layer.

[0111] Exemplarily, let Y1 be the admittance of the inner semiconductive shielding layer, Y2 be the admittance of the outer semiconductive shielding layer, Y3 be the admittance of the main insulating layer, and Y4 be the admittance of the semiconductive resistive water layer. Then in some embodiments:

[0112] When the unit circuit includes a main insulating layer, a semiconductive resistive water layer and an inner semiconductive shielding layer, the frequency-dependent admittance of the unit circuit is:

[0113] When the unit circuit includes a main insulating layer, a semiconductive resistive water layer and an outer semiconductive shielding layer, the frequency-varying admittance of the unit circuit is:

[0114] When the unit circuit includes a main insulating layer, a semiconductive water layer, an inner semiconductive shielding layer and an outer semiconductive shielding layer, the frequency-dependent admittance of the unit circuit is:

[0115] In one embodiment, the frequency-varying admittance of the inner semi-conductive shielding layer is calculated according to the first complex dielectric constant equation, and the frequency-varying admittance of the outer semi-conductive shielding layer is calculated according to the second complex dielectric constant equation, specifically:

[0116] The admittance of the inner semi-conductive shield is calculated according to the following formula:

[0117]

[0118] The admittance of the outer semi-conductive shield is calculated according to the following formula:

[0119]

[0120] Where Y1(ω) is the admittance of the inner semi-conductive shielding layer, ω is the angular frequency, ε0 ​​is the vacuum dielectric constant, is the first complex dielectric constant equation, r o1 is the outer radius of the inner semi-conductive shield, r i1 is the inner radius of the inner semi-conductive shielding layer, Y2(ω) is the admittance of the outer semi-conductive shielding layer, is the second complex dielectric constant equation, r o2 is the outer radius of the outer semi-conductive shield, r i2 is the inner radius of the outer semi-conductive shield.

[0121] In some embodiments, the admittance of the main insulating layer and the admittance of the semi-conductive water layer are both based on Calculate, where n = 3, 4; and The value of can be directly obtained through existing technology.

[0122] In one embodiment, the characteristic impedance Z0, wave velocity υ and propagation coefficient γ in step S15 "calculating the characteristic impedance, wave velocity and propagation coefficient of the cable joint along the axial length at different frequencies according to the impedance and admittance of each unit circuit that vary with frequency, and calculating the transfer matrix and transmission coefficient of the cable joint according to the characteristic impedance and the propagation coefficient" are calculated as shown in the following formula:

[0123]

[0124] Among them, Z is the impedance of the unit circuit, Y is the admittance of the unit circuit, and C is the capacitance in parallel with the conductance in the unit circuit.

[0125] In one embodiment, the transfer matrix of the cable joint is calculated by the following steps:

[0126] The cable connector is equivalent to a plurality of coaxial series-connected units, and according to the propagation coefficient, axial length and characteristic impedance corresponding to each unit, the transfer matrix characteristic parameters of each unit are calculated;

[0127] The product of the transfer matrix characteristic parameters of all the units is calculated to obtain the transfer matrix of the cable joint.

[0128] In one embodiment, the transfer matrix characteristic parameters of the unit are calculated by the following formula:

[0129]

[0130] in, represents the characteristic parameters of the transfer matrix of the i-th unit, γ i is the propagation coefficient corresponding to the i-th unit circuit in the equivalent circuit, l i is the axial length of the i-th unit, Z oi is the characteristic impedance corresponding to the i-th unit circuit in the equivalent circuit.

[0131] Specifically, since both ends of the cable connector are connected to the cable body in the actual circuit, when considering the wave refraction reflection, the reference impedance at both ends of the connector equivalent two-port network can be set to the characteristic impedance of the cable body. Furthermore, in one embodiment, the transmission coefficient of the cable connector is calculated by the following formula:

[0132]

[0133] Among them, T j is the transmission coefficient of the cable joint, Z o is the characteristic impedance of the cable connector, and A, B, C, and D are all elements in the transfer matrix of the cable connector.

[0134] In one experiment, a prefabricated high-voltage cable joint with a cable model of YJLW03-Z-64 / 110kV-1×630mm2 was subjected to the high-voltage cable joint frequency response modeling method considering the broadband characteristics of the semi-conductive shielding layer provided by the embodiment of the present invention, and the following results were obtained: Figure 6 The diagram shows how the parameters of the inner and outer semi-conductive shielding layers of the cable connector vary with frequency.

[0135] Based on the measured data of the inner and outer semi-conductive shielding layers, the broadband dielectric constant equations of the inner and outer semi-conductive shielding layers of the cable joint are obtained through mathematical fitting, which is then substituted into the distributed parameter model of the cable joint to calculate its frequency response characteristic parameters. Figure 7 The variation of the axial characteristic impedance of the cable connector of the straight-through connector at a frequency of 1MHz is given.

[0136] The changes of the axial characteristic impedance of the connector at different frequencies are as follows Figure 8 As shown in the figure, it can be found that although the characteristic impedance of the cable connector has an obvious changing trend with the axial distance, the frequency-varying parameters of the cable connector maintain good consistency in the high-frequency range and have low frequency dependence characteristics.

[0137] According to the transfer matrix and transmission coefficient, we can calculate Fig. 9 The transmission coefficient amplitude of the cable joint shown in the figure is in the range of 1MHz-100MHz. As the signal frequency increases, the transmission coefficient amplitude of the middle joint decays in an oscillating manner as a whole. When the signal frequency is 100MHz, the transmission coefficient amplitude is about 0.85.

[0138] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A frequency response modeling method for a high-voltage cable connector considering the broadband characteristics of a semi-conductive shielding layer, characterized in that: include: Obtaining a first complex dielectric constant and a second complex dielectric constant of a pretreated inner semiconductive shielding layer sample and an outer semiconductive shielding layer sample of a cable joint measured within a preset frequency range; Fitting the relationship between the first complex dielectric constant and the second complex dielectric constant and the frequency respectively, to obtain a first complex dielectric constant equation corresponding to the inner semi-conductive shielding layer sample and a second complex dielectric constant equation corresponding to the outer semi-conductive shielding layer sample; According to the internal structural differences of the cable joint, the cable joint is subjected to segmented equivalent processing, and a distributed parameter equivalent circuit considering the crimping of the cable joint conductor is established according to the segmented results; wherein the distributed parameter equivalent circuit includes a plurality of unit circuits; Considering the structure and material properties of each unit after segmentation, combining the first complex dielectric constant equation and the second complex dielectric constant equation, calculating the impedance and admittance of each unit circuit as it changes with frequency; According to the impedance and admittance of each unit circuit that vary with frequency, calculate the characteristic impedance, wave velocity and propagation coefficient of the cable joint along the axial length at different frequencies, and according to the characteristic impedance and the propagation coefficient, calculate the transfer matrix and transmission coefficient of the cable joint; According to the difference in the internal structure of the cable joint, the cable joint is subjected to segmented equivalent processing, and a distributed parameter equivalent circuit considering the crimping of the cable joint conductor is established according to the segmented result, which specifically includes: According to the difference in the internal structure of the cable connector and the axially symmetrical characteristics of the cable connector, the left semi-axial part of the cable connector is divided into a plurality of units connected in series; wherein, if the unit is a non-crimping section of the cable connector, the unit is a first unit; and if the unit is a crimping section of the cable connector, the unit is a second unit; Establishing each first unit circuit corresponding to each first unit and a second unit circuit corresponding to the second unit to establish a distributed parameter equivalent circuit considering the crimping of the cable connector conductor; The considering the structure and material properties of each unit after segmentation, combining the first complex dielectric constant equation and the second complex dielectric constant equation, and calculating the impedance and admittance of each unit circuit as it changes with frequency, specifically includes: For each of the unit circuits, calculating the distributed resistance and distributed inductance of the unit circuit that vary with frequency, and calculating the impedance of the unit circuit that varies with frequency based on the distributed resistance and the distributed inductance; Calculating the frequency-varying admittance of each material structure layer in the unit circuit, and calculating the frequency-varying admittances of all material structure layers in parallel to obtain the frequency-varying admittance of the unit circuit; wherein the material structure layers contained in the unit circuit include a main insulating layer and a semiconductive resistive water layer, and also include at least one of an inner semiconductive shielding layer and an outer semiconductive shielding layer, and the frequency-varying admittance of the inner semiconductive shielding layer is calculated according to the first complex dielectric constant equation, and the frequency-varying admittance of the outer semiconductive shielding layer is calculated according to the second complex dielectric constant equation; The transfer matrix of the cable joint is calculated by the following steps: The cable connector is equivalent to a plurality of coaxial units connected in series, and the transfer matrix characteristic parameters of each unit are calculated according to the propagation coefficient, axial length and characteristic impedance corresponding to each unit; Calculating the product of the transfer matrix characteristic parameters of all the units to obtain the transfer matrix of the cable connector; The transmission coefficient of the cable joint is calculated by the following formula: Among them, T j is the transmission coefficient of the cable joint, Z o is the characteristic impedance of the cable connector, and A, B, C, and D are all elements in the transfer matrix of the cable connector.

2. The high-voltage cable joint frequency response modeling method considering the broadband characteristics of the semi-conductive shielding layer as claimed in claim 1 is characterized in that: The distributed resistance of the unit circuit that varies with frequency is calculated by the following steps: When the unit circuit is a first unit circuit, the distributed resistance of the first unit circuit that varies with frequency is calculated according to the following formula: When the unit circuit is a second unit circuit, the distributed resistance of the second unit circuit that varies with frequency is calculated according to the following formula: a′=a″+△d Wherein, R(ω) is the distributed resistance of the first unit, ω is the angular frequency, a1 is the outer radius of the inner conductor, a2 is the inner radius of the outer conductor, ρ1 is the resistivity of the inner conductor, ρ2 is the resistivity of the outer conductor, μ0 is the magnetic permeability of vacuum, R'(ω) is the distributed resistance of the second unit, K is the contact coefficient, a' is the conductor radius of the cable body, a" is the radius of the conductor of the crimping section of the cable connector, ρ' is the resistivity of the normal conductor, ρ" is the resistivity of the conductor of the crimping section of the cable connector, △d is the thickness of the crimping section of the cable connector, l is the length of the first unit circuit, and l' is the length of the second unit circuit.

3. The high-voltage cable joint frequency response modeling method considering the broadband characteristics of the semi-conductive shielding layer as claimed in claim 1 is characterized in that: The distributed inductance of the unit circuit is obtained by the following steps: When the unit circuit is a first unit circuit, the distributed inductance of the first unit circuit is calculated according to the following formula: When the unit circuit is a second unit circuit, the distributed inductance of the second unit circuit is calculated according to the following formula: Wherein, L(ω) is the distributed inductance of the first unit circuit, ω is the angular frequency, a1 is the radius of the cable body conductor, a2 is the inner radius of the outer conductor, μ0 is the vacuum permeability, ρ1 is the resistivity of the inner conductor, ρ2 is the resistivity of the outer conductor, L'(ω) is the distributed inductance of the second unit, ρ″ is the resistivity of the conductor of the crimping section of the cable connector, a″ is the radius of the conductor of the crimping section of the cable connector, Y is the axial length of the crimping section of the cable connector, l is the length of the first unit circuit, and l' is the length of the second unit circuit.

4. The high-voltage cable joint frequency response modeling method considering the broadband characteristics of the semi-conductive shielding layer as claimed in claim 1 is characterized in that: The frequency-varying admittance of the inner semi-conductive shielding layer is calculated according to the first complex dielectric constant equation, and the frequency-varying admittance of the outer semi-conductive shielding layer is calculated according to the second complex dielectric constant equation, specifically: The admittance of the inner semi-conductive shield is calculated according to the following formula: The admittance of the outer semi-conductive shield is calculated according to the following formula: Where Y1(ω) is the admittance of the inner semi-conductive shielding layer, ω is the angular frequency, ε0 ​​is the vacuum dielectric constant, is the first complex dielectric constant equation, r o1 is the outer radius of the inner semi-conductive shield, r i1 is the inner radius of the inner semi-conductive shielding layer, Y2(ω) is the admittance of the outer semi-conductive shielding layer, is the second complex dielectric constant equation, r o2 is the outer radius of the outer semi-conductive shield, r i2 is the inner radius of the outer semi-conductive shielding layer, and j is the imaginary unit.

5. The high-voltage cable joint frequency response modeling method considering the broadband characteristics of the semi-conductive shielding layer as claimed in claim 1 is characterized in that: The transfer matrix characteristic parameters of the unit are calculated by the following formula: in, represents the characteristic parameters of the transfer matrix of the i-th unit, γ i is the propagation coefficient corresponding to the i-th unit circuit in the equivalent circuit, l i is the axial length of the i-th unit, Z oi is the characteristic impedance corresponding to the i-th unit circuit in the equivalent circuit.

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