Cable insulation status identification method, device and equipment based on harmonic amplification factor

Abstract

The present application discloses a cable insulation state identification method, device and equipment based on harmonic amplification factor, which relates to the field of cable insulation state identification. The key points of the technical solution are: constructing a correlation equation between the harmonic amplification factor of the cable and the equivalent impedance parameter of the Π-type equivalent circuit after the cable is equivalent; obtaining the harmonic amplitude at both ends of the cable at the current moment, and calculating the harmonic amplification factor of the cable at the current moment based on the harmonic amplitude; constructing an objective function with the minimum sum of squares of the residuals between the harmonic amplification factor represented by the correlation equation and the harmonic amplification factor at the current moment, using the Gauss-Newton iteration method to solve the objective function, and obtaining the index value of the cable insulation state; identifying the insulation state of the cable based on the index value of the cable insulation state. The present application calculates the harmonic voltage and harmonic current amplification factors based only on the harmonic data obtained by the existing power grid harmonic monitoring device, and estimates the index value of the current insulation state, thereby achieving accurate quantification of small changes in the cable insulation state.

Description

Technical Field

[0001] The present application relates to the field of cable insulation status identification, and more specifically, to a cable insulation status identification method, device and equipment based on harmonic amplification factor. Background Art

[0002] Cross-linked polyethylene cables have been widely used in power systems. As the service life increases, the insulation material will gradually age, resulting in a decrease in insulation performance, which will endanger the safety of the power system. Therefore, it is necessary to evaluate the insulation condition of the cable.

[0003] At present, the methods for estimating the insulation state of cables based on the power disturbance flowing through the cables can be divided into two categories. The first is based on power transient disturbances. This type of method evaluates the insulation state of cables by analyzing the response characteristics of transient disturbances caused by power grid faults, high-voltage filter switching, etc. when passing through the cables; the second is the insulation state monitoring method based on steady-state wide-frequency domain harmonic data. The transient disturbances of the power grid required by the first type of method usually occur randomly, resulting in a lack of available data, and this type of method needs to extract the high-frequency characteristic quantity of the disturbance, so the sampling rate of the measuring device is high, which limits the application of this type of method; the second type of method needs to obtain the phasor data of the ratio of the harmonic voltage and harmonic current at both ends of the cable respectively and sum them, so the phasor data (such as amplitude and phase) of the harmonic data at both ends of the cable are required to be accurately synchronized to suppress the synchronous phase error of the harmonic voltage and harmonic current, otherwise the estimation result will be unavailable. Most of the current harmonic measurement devices use network synchronization, so the synchronization error between devices is often large, which greatly affects the use of the second type of method. Summary of the invention

[0004] The purpose of the present application is to provide a method, device and equipment for identifying the insulation status of a cable based on harmonic amplification factors. The present application improves the accuracy of identifying the insulation status of the cable, thereby reducing the incidence of cable insulation failures and effectively improving the operational stability of the power grid.

[0005] In a first aspect of the present application, a method for identifying the insulation state of a cable based on harmonic amplification factor is provided, the method comprising:

[0006] Constructing a correlation equation between the harmonic amplification factor of the cable and the equivalent impedance parameter of the Π-type equivalent circuit after the cable is equivalent; wherein the equivalent impedance parameter is determined based on the complex dielectric constant of the insulating material of the cable;

[0007] Obtain the harmonic amplitudes at both ends of the cable at the current moment, and calculate the harmonic amplification factor of the cable at the current moment based on the harmonic amplitudes;

[0008] An objective function is constructed to minimize the residual sum of squares between the harmonic amplification factor represented by the correlation equation and the harmonic amplification factor at the current moment, and the Gauss-Newton iteration method is used to solve the objective function to obtain the index value of the cable insulation state;

[0009] Identify the insulation status of the cable based on the index value of the cable insulation status.

[0010] In an implementation of the first aspect of the present application, the equivalent impedance parameter is determined based on the complex dielectric constant of the insulating material of the cable, specifically:

[0011] Obtain the complex dielectric constant of the cable's insulation material and the cable's dimensional parameters;

[0012] Calculate the cable's unit length admittance based on the complex dielectric constant and size parameters;

[0013] The equivalent impedance parameters of the cable's Π-type equivalent circuit are calculated based on the cable's unit length admittance and the cable length; the equivalent impedance parameters include the series impedance and the ground impedance of the cable's Π-type equivalent circuit.

[0014] In an implementation of the first aspect of the present application, the expression for constructing the correlation equation between the harmonic amplification factor of the cable and the equivalent impedance parameter of the Π-type equivalent circuit after the cable is equivalent is:

[0015] Among them, Z m , Z p are the series impedance and ground impedance of the cable Π-type equivalent circuit, F u is the harmonic voltage amplification factor, F i is the harmonic current amplification factor, It is the ratio of harmonic voltage to harmonic current at the end of the cable.

[0016] In an implementation of the first aspect of the present application, the harmonic amplitudes at both ends of the cable at the current moment are obtained, and the harmonic amplification factor of the cable at the current moment is calculated according to the harmonic amplitudes, specifically:

[0017] Obtain the harmonic voltage amplitude and harmonic current amplitude at both ends of the cable measured at the current moment;

[0018] The harmonic voltage amplification factor is obtained by dividing the harmonic voltage amplitude at one end of the cable by the harmonic voltage amplitude at the other end;

[0019] The harmonic current amplification factor is obtained by dividing the harmonic current amplitude at one end of the cable by the harmonic current amplitude at the other end;

[0020] The harmonic voltage amplification factor is added to the harmonic current amplification factor to obtain the harmonic amplification factor of the cable at the current moment.

[0021] In an implementation of the first aspect of the present application, the objective function is expressed as: Among them, argmin means optimization Minimize the residual sum of squares, is * The estimated value of K is the harmonic amplification factor, K T With K M are the theoretical value and measured value of K, K T is obtained from the correlation equation, h i is the i-th harmonic frequency, and R is the total number of harmonic frequencies.

[0022] In a second aspect of the present application, a device for identifying cable insulation status based on harmonic amplification factor is provided, the device comprising:

[0023] A correlation equation construction module is used to construct a correlation equation between the harmonic amplification factor of the cable and the equivalent impedance parameter of the Π-type equivalent circuit after the cable is equivalent; wherein the equivalent impedance parameter is determined based on the complex dielectric constant of the insulating material of the cable;

[0024] The harmonic amplification factor calculation module is used to obtain the harmonic amplitudes at both ends of the cable at the current moment, and calculate the harmonic amplification factor of the cable at the current moment according to the harmonic amplitudes;

[0025] The insulation index solving module is used to construct an objective function that minimizes the residual sum of squares between the harmonic amplification factor represented by the correlation equation and the harmonic amplification factor at the current moment, and uses the Gauss-Newton iteration method to solve the objective function to obtain the index value of the cable insulation state;

[0026] The insulation state identification module is used to identify the insulation state of the cable according to the index value of the cable insulation state.

[0027] In an implementation of the second aspect of the present application, the correlation equation construction module includes:

[0028] A cable parameter acquisition module is used to obtain the complex dielectric constant of the cable's insulation material and the cable's size parameters;

[0029] Unit length admittance calculation module, used to calculate the unit length admittance of the cable based on the complex dielectric constant and size parameters;

[0030] The equivalent impedance parameter calculation module is used to calculate the equivalent impedance parameters of the cable Π-type equivalent circuit based on the cable's unit length admittance and cable length; wherein the equivalent impedance parameters include the series impedance and ground impedance of the cable Π-type equivalent circuit.

[0031] In an implementation of the first aspect of the present application, the expression for constructing the correlation equation between the harmonic amplification factor of the cable and the equivalent impedance parameter of the Π-type equivalent circuit after the cable is equivalent is:

[0032] Among them, Z m , Z p are the series impedance and ground impedance of the cable Π-type equivalent circuit, F u is the harmonic voltage amplification factor, F i is the harmonic current amplification factor, It is the ratio of harmonic voltage to harmonic current at the end of the cable.

[0033] In an implementation of the second aspect of the present application, the harmonic amplification factor calculation module includes:

[0034] A harmonic parameter acquisition module, used to obtain the harmonic voltage amplitude and harmonic current amplitude at both ends of the cable measured at the current moment;

[0035] A harmonic voltage amplification factor calculation module is used to obtain the harmonic voltage amplification factor by dividing the harmonic voltage amplitude at one end of the cable by the harmonic voltage amplitude at the other end;

[0036] A harmonic current amplification factor calculation module is used to obtain the harmonic current amplification factor by dividing the harmonic current amplitude at one end of the cable by the harmonic current amplitude at the other end;

[0037] The harmonic voltage amplification factor is added to the harmonic current amplification factor to obtain the harmonic amplification factor of the cable at the current moment.

[0038] The third aspect of the present application provides a computer device, which includes a processor, a memory, and a computer program stored in the memory and executable by the processor, wherein when the computer program is executed by the processor, the steps of a cable insulation status identification method based on harmonic amplification factor as provided in the first aspect of the present application are implemented.

[0039] Compared with the prior art, this application has the following beneficial effects:

[0040] In a cable insulation state identification method based on harmonic amplification factor provided by the present application, the present application establishes a correlation equation between the cable insulation index and the harmonic voltage and harmonic current amplification factors at both ends of the cable, and constructs an objective function of minimizing the residual sum of squares between the harmonic amplification factor represented by the correlation equation and the harmonic amplification factor at the current moment, and solves the index value of the insulation state through Gauss-Newton iteration, thereby realizing non-invasive identification of the cable insulation state. It can be seen that the present application only calculates the harmonic voltage amplification factor and the harmonic current amplification factor (i.e., the amplitude ratio of the harmonic voltage and harmonic current at both ends of the cable) based on the harmonic amplitude data obtained by the existing power grid harmonic monitoring device, thereby estimating the index value of the cable insulation state, and can realize accurate quantification of small changes in the cable insulation state, and the entire data acquisition and identification process has no effect on the cable operation. In summary, the present application improves the accuracy of the cable insulation state identification, thereby reducing the incidence of cable insulation failures, and can effectively improve the operational stability of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The drawings described herein are used to provide a further understanding of the embodiments of the present application, constitute a part of the present application, and do not constitute a limitation on the embodiments of the present application. In the drawings:

[0042] Figure 1 A schematic flow chart of a cable insulation status identification method based on harmonic amplification factor provided in an embodiment of the present application;

[0043] Figure 2 An equivalent circuit diagram of cable harmonics transmitted through a cable provided in an embodiment of the present application;

[0044] Figure 3 An impedance scanning curve diagram of an offshore wind farm provided in an embodiment of the present application;

[0045] Figure 4 A comparison chart of cable insulation status index estimation results and reference values ​​at different cable lengths provided in an embodiment of the present application;

[0046] Figure 5 A comparison chart of cable insulation status index estimation results and reference values ​​under different power grid short-circuit capacities provided in an embodiment of the present application;

[0047] Figure 6 A principle block diagram of a cable insulation status identification device based on harmonic amplification factor provided in an embodiment of the present application. DETAILED DESCRIPTION

[0048] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with examples and drawings. The illustrative implementation scheme of the present application and its description are only used to explain the present application and are not intended to limit the present application.

[0049] It should be noted that the terms "include" or "may include" used in various embodiments of the present application indicate the presence of the function, operation or element applied for, and do not limit the addition of one or more functions, operations or elements. In addition, as used in various embodiments of the present application, the terms "include", "have" and their cognates are only intended to indicate specific features, numbers, steps, operations, elements, components or a combination of the foregoing items, and should not be understood as first excluding the presence of one or more other features, numbers, steps, operations, elements, components or a combination of the foregoing items or the possibility of adding one or more features, numbers, steps, operations, elements, components or a combination of the foregoing items.

[0050] Please refer to Figure 1 , Figure 1 A schematic diagram of a flow chart of a cable insulation status identification method based on harmonic amplification factor provided in an embodiment of the present application, such as Figure 1 As shown, the method includes:

[0051] S101, constructing a correlation equation between the harmonic amplification factor of the cable and the equivalent impedance parameter of the Π-type equivalent circuit after the cable is equivalent; wherein the equivalent impedance parameter is determined based on the complex dielectric constant of the insulating material of the cable.

[0052] In this embodiment, the expression of the correlation equation is: Among them, Z m , Z p are the series impedance and ground impedance of the cable Π-type equivalent circuit, F u is the harmonic voltage amplification factor, F i is the harmonic current amplification factor, It is the ratio of harmonic voltage to harmonic current at the end of the cable.

[0053] It should be noted that if Figure 2 As shown in the figure, the ratio of harmonic voltage to harmonic current at the end of the cable is

[0054] like Figure 2 As shown, the Π-type equivalent circuit after the cable is equivalent is common knowledge to those skilled in the art, so no unnecessary elaboration is made.

[0055] Secondly, for the association equation between the harmonic amplification factor of the cable and the equivalent impedance parameters of the Π-type equivalent circuit after the cable is equivalent, provided in this embodiment. In the power grid, power harmonics, as a typical steady-state disturbance, have been widely distributed in the transmission and distribution network with the large-scale commissioning of power electronic equipment in the power grid. When power harmonics are transmitted along the cable, certain frequency harmonics are significantly amplified due to the inductive and capacitive coupling between the cable and the power grid. At this time, the harmonic amplification factor at both ends of the cable is very sensitive to the insulation parameters of the cable. Therefore, the insulation parameters of the cable can be estimated based on the harmonic amplification factor at both ends of the cable. Since the harmonic data at both ends of the cable can be obtained based on the existing harmonic monitoring device, the idea of ​​estimating the insulation parameters based on the harmonic amplification factor is easy to be practical in engineering, which will greatly reduce the incidence of cable insulation failures and is of great significance to the safe and stable operation of the power grid.

[0056] The equivalent impedance parameter is determined based on the complex dielectric constant of the cable's insulation material, specifically:

[0057] Get the complex dielectric constant of the cable's insulation material and the cable's dimensional parameters.

[0058] In this embodiment, the complex dielectric constant of the cable insulation material is a commonly used cable insulation status indicator, as shown in Table 1 below. However, since the imaginary part of the complex dielectric constant is much smaller than the real part, the imaginary part estimation error is relatively large. Therefore, in this embodiment, only the real part of the complex dielectric constant is used to effectively indicate the cable insulation status. Therefore, the real part of the complex dielectric constant is used as the insulation status indicator.

[0059] Table 1 Corresponding to different cable insulation conditions

[0060] Insulation status intact Slight aging Moderate aging Severe aging <![CDATA[ε * ]]> 2.46-j0.000532 2.57-j0.00514 2.63-j0.0213 2.69-j0.0539

[0061] By comparing the data changes in Table 1, i.e. the real part and the imaginary part, it can be seen that for different insulation aging degrees, the real part changes more obviously. Therefore, the index value determined in the subsequent step S104 also uses the real part as a reference standard for insulation state identification.

[0062] It is common knowledge in the art that the central conductor of the cable is wrapped by an insulating material, and the outer layer of the insulating layer is a metal shielding layer. The size parameters of the cable are divided into the radius value of the central conductor and the radius value of the metal shielding layer, as shown in Table 2 below.

[0063] Table 2 Cable size parameter values

[0064] Cable layer <![CDATA[Central conductor (r c )]]> <![CDATA[Metal shield (r m )]]> Radius value (mm) 23.8 56.2

[0065] The admittance per unit length of the cable is calculated based on the complex dielectric constant and size parameters.

[0066] In this embodiment, the cable equivalent admittance per unit length is characterized based on the cable insulation status index.

[0067] Where Y0 is the admittance per unit length of the cable, ε0 is the dielectric constant of vacuum, ε′ and ε″ are the complex dielectric constants ε * The real and imaginary values, r c is the radius of the central conductor, r m is the radius of the metal shielding layer.

[0068] The equivalent impedance parameters of the cable's Π-type equivalent circuit are calculated based on the cable's unit length admittance and the cable length; the equivalent impedance parameters include the series impedance and the ground impedance of the cable's Π-type equivalent circuit.

[0069] In this embodiment, based on the admittance per unit length of the cable described in the above embodiment, the equivalent impedance parameter of the cable Π-type equivalent circuit is characterized based on the admittance per unit length of the cable, that is, In the formula, Z m With Z p are the series impedance and ground impedance of the cable Π-type equivalent circuit, Z c is the line wave impedance, γ is the line propagation constant, and l is the cable length.

[0070] And in formula (2), we have Where Z0 is the cable impedance per unit length, which is a constant and does not change with the aging of the cable insulation.

[0071] S102, obtaining the harmonic amplitudes at both ends of the cable at the current moment, and calculating the harmonic amplification factor of the cable at the current moment according to the harmonic amplitudes.

[0072] In this embodiment, the current moment refers to the cable that currently needs to be identified. The acquisition of the harmonic amplitude at both ends of the cable at the current moment can be measured by an existing power grid harmonic monitoring device, which is a conventional technical means in the art.

[0073] In some embodiments, the measured harmonic amplitudes include harmonic voltage amplitudes and harmonic current amplitudes at both ends of the cable at the current moment;

[0074] Secondly, the harmonic voltage amplification factor is obtained by dividing the harmonic voltage amplitude at one end of the cable by the harmonic voltage amplitude at the other end;

[0075] The harmonic current amplification factor is obtained by dividing the harmonic current amplitude at one end of the cable by the harmonic current amplitude at the other end.

[0076] The calculation formula for harmonic voltage / current amplification factor is:

[0077] The harmonic voltage amplification factor is added to the harmonic current amplification factor to obtain the harmonic amplification factor of the cable at the current moment.

[0078] The calculation formula for the harmonic amplification factor of the cable at the current moment is: K = |F u |+|F i | (6).

[0079] S103, constructing an objective function for minimizing the sum of squares of the residuals between the harmonic amplification factor represented by the correlation equation and the harmonic amplification factor at the current moment, solving the objective function using the Gauss-Newton iteration method, and obtaining an index value of the cable insulation state.

[0080] In some embodiments, the objective function is expressed as: Among them, argmin means optimization Minimize the residual sum of squares, is * The estimated value of K is the harmonic amplification factor, K T With K M are the theoretical value and measured value of K, K T is obtained from the correlation equation, h i is the i-th harmonic frequency, and R is the total number of harmonic frequencies.

[0081] Since the correlation equation is a nonlinear equation, it can be regarded as a least squares problem. Therefore, in this embodiment, K T With K M The Gauss-Newton iteration method is used to iteratively solve the index value of the cable insulation state, that is, the complex dielectric constant of the cable under actual conditions.

[0082] S104, identifying the insulation status of the cable according to the index value of the insulation status of the cable.

[0083] In this embodiment, the insulation state of the cable can be determined by finding the real part value of the complex dielectric constant of the cable in the insulation state under the standard reference and then comparing it with the real part value of the complex dielectric constant of the cable in the actual situation.

[0084] Based on the embodiments described above, it can be seen that the present embodiment provides a method for identifying the insulation state of a cable based on harmonic amplification factors. The present embodiment establishes a correlation equation between the cable insulation index and the harmonic voltage and harmonic current amplification factors at both ends of the cable, and constructs an objective function of minimizing the sum of squared residuals between the harmonic amplification factor represented by the correlation equation and the harmonic amplification factor at the current moment, and solves the index value of the insulation state through Gauss-Newton iteration, thereby realizing the non-invasive identification of the insulation state of the cable. It can be seen that the present application only calculates the harmonic voltage amplification factor and the harmonic current amplification factor (i.e., the amplitude ratio of the harmonic voltage and harmonic current at both ends of the cable) based on the harmonic amplitude data obtained by the existing power grid harmonic monitoring device, thereby estimating the index value of the insulation state of the cable, and can realize the accurate quantification of the slight changes in the insulation state of the cable, and the entire data acquisition and identification process has no effect on the operation of the cable. In summary, the present application improves the accuracy of the insulation state identification of the cable, thereby reducing the incidence of cable insulation failures, and can effectively improve the operational stability of the power grid.

[0085] To explain the identification method provided in this embodiment in detail, based on Figure 2 The circuit shown is simulated to verify the applicability and effectiveness of the proposed method in scenarios with different cable lengths and short-circuit capacity of the power grid at the cable end.

[0086] The simulation scene settings are as follows:

[0087] Simulation scenario 1: short-circuit capacity S c =50000MVA, the cable length l is set to 10~50km, with a step length of 10km.

[0088] Simulation scenario 2: l = 40 km, S c Set to 10000~50000MVA, with a step size of 10000MVA.

[0089] The simulation steps are as follows:

[0090] 1) Press Figure 3 The actual wind farm impedance scanning curve settings shown Figure 2 middle value, and calculate according to formula (8)

[0091]

[0092] 2) Set to 1p.u,

[0093] 3) Based on the ε corresponding to different cable insulation conditions shown in Table 1 *The values ​​and the cable size parameters in Table 2 are used to calculate the capacitance per unit length under different insulation conditions based on formula (1), and according to the l value, Z is calculated based on formula (2) and formula (3) m and Z p .

[0094] 4) According to Figure 2 The circuit in the figure calculates the harmonic voltage and current values ​​at both ends of the cable under different insulation conditions. According to the accuracy requirements of Class I measuring devices in the IEC 61000-4-7 standard, a random error of ±5% is added to simulate the measurement error.

[0095] 5) Evaluate ε based on the proposed method * , and compare the difference between its actual estimated value ε' and the reference value to verify the effectiveness of the proposed method. The estimation results under scenario 1 and scenario 2 are shown as follows: Figure 4 , Figure 5 As shown. Figure 4 In the figure, when l takes different values, the corresponding estimation results under each insulation state are close to the reference value (true value). Therefore, it can be seen that the proposed method is applicable to cables of different lengths. Figure 5 In, when S c When different values ​​are taken, the corresponding estimation results under each insulation state are close to the true value. Therefore, it can be seen that the proposed method is applicable to cables connected to different power grid short-circuit capacities. In summary, the insulation state identification method provided in this embodiment is effective in different scenarios, which improves the accuracy of cable insulation state identification, thereby reducing the occurrence rate of cable insulation failures and effectively ensuring the operational stability of the power grid.

[0096] Please refer to Figure 6 , Figure 6 A schematic diagram of a cable insulation status identification device based on harmonic amplification factor provided in an embodiment of the present application is shown in FIG. Figure 6 As shown, the device comprises:

[0097] The correlation equation construction module 610 is used to construct a correlation equation between the harmonic amplification factor of the cable and the equivalent impedance parameter of the Π-type equivalent circuit after the cable is equivalent; wherein the equivalent impedance parameter is determined based on the complex dielectric constant of the insulation material of the cable;

[0098] The harmonic amplification factor calculation module 620 is used to obtain the harmonic amplitudes at both ends of the cable at the current moment, and calculate the harmonic amplification factor of the cable at the current moment according to the harmonic amplitudes;

[0099] The insulation index solving module 630 is used to construct an objective function for minimizing the residual sum of squares between the harmonic amplification factor represented by the correlation equation and the harmonic amplification factor at the current moment, and solve the objective function using the Gauss-Newton iteration method to obtain the index value of the cable insulation state;

[0100] The insulation state identification module 640 is used to identify the insulation state of the cable according to the index value of the insulation state of the cable.

[0101] In a cable insulation state identification device based on harmonic amplification factor provided in this embodiment, the present application establishes a correlation equation between the cable insulation index and the harmonic voltage and harmonic current amplification factors at both ends of the cable, and constructs an objective function of minimizing the residual sum of squares between the harmonic amplification factor represented by the correlation equation and the harmonic amplification factor at the current moment, and solves the index value of the insulation state through Gauss-Newton iteration, thereby realizing non-invasive identification of the cable insulation state. It can be seen that the present application only calculates the harmonic voltage amplification factor and the harmonic current amplification factor (i.e., the amplitude ratio of the harmonic voltage and harmonic current at both ends of the cable) based on the harmonic amplitude data obtained by the existing power grid harmonic monitoring device, thereby estimating the index value of the cable insulation state, and can realize accurate quantification of small changes in the cable insulation state, and the entire data acquisition and identification process has no effect on the cable operation. In summary, the present application improves the accuracy of the cable insulation state identification, thereby reducing the incidence of cable insulation failures, and can effectively improve the operational stability of the power grid.

[0102] In some embodiments, the correlation equation building module 610 includes:

[0103] A cable parameter acquisition module is used to obtain the complex dielectric constant of the cable's insulation material and the cable's size parameters;

[0104] Unit length admittance calculation module, used to calculate the unit length admittance of the cable based on the complex dielectric constant and size parameters;

[0105] The equivalent impedance parameter calculation module is used to calculate the equivalent impedance parameters of the cable Π-type equivalent circuit based on the cable's unit length admittance and cable length; wherein the equivalent impedance parameters include the series impedance and ground impedance of the cable Π-type equivalent circuit.

[0106] In some embodiments, the expression for constructing the correlation equation between the harmonic amplification factor of the cable and the equivalent impedance parameter of the Π-type equivalent circuit after the cable is equivalent is:

[0107] Among them, Z m , Z p are the series impedance and ground impedance of the cable Π-type equivalent circuit, F u is the harmonic voltage amplification factor, F i is the harmonic current amplification factor, It is the ratio of harmonic voltage to harmonic current at the end of the cable.

[0108] In some embodiments, the harmonic amplification factor calculation module 620 includes:

[0109] A harmonic parameter acquisition module, used to obtain the harmonic voltage amplitude and harmonic current amplitude at both ends of the cable measured at the current moment;

[0110] A harmonic voltage amplification factor calculation module is used to obtain the harmonic voltage amplification factor by dividing the harmonic voltage amplitude at one end of the cable by the harmonic voltage amplitude at the other end;

[0111] A harmonic current amplification factor calculation module is used to obtain the harmonic current amplification factor by dividing the harmonic current amplitude at one end of the cable by the harmonic current amplitude at the other end;

[0112] The harmonic voltage amplification factor is added to the harmonic current amplification factor to obtain the harmonic amplification factor of the cable at the current moment.

[0113] The embodiment of the present application also provides a computer device, which includes a processor, a memory, a communication interface 330 and at least one communication bus for connecting the processor, the memory and the communication interface. The memory includes but is not limited to a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (PROM) or a portable CD-ROM, and the memory is used for related instructions and data.

[0114] The communication interface is used to receive and send data. The processor may be one or more. When the processor is a CPU, the CPU may be a single-core CPU or a multi-core CPU. The processor in the computer device is used to read one or more programs stored in the memory and perform the following operations: construct an association equation between the harmonic amplification factor of the cable and the equivalent impedance parameter of the Π-type equivalent circuit after the cable is equivalent; wherein the equivalent impedance parameter is determined based on the complex dielectric constant of the insulating material of the cable; obtain the harmonic amplitude at both ends of the cable at the current moment, and calculate the harmonic amplification factor of the cable at the current moment based on the harmonic amplitude; construct an objective function with the minimum residual sum of squares between the harmonic amplification factor represented by the association equation and the harmonic amplification factor at the current moment, and use the Gauss-Newton iteration method to solve the objective function to obtain the index value of the cable insulation state; identify the insulation state of the cable based on the index value of the cable insulation state.

[0115] It should be noted that the specific implementation of each operation can be Figure 1 The corresponding description of the method embodiment shown, the computer device can be used to execute a cable insulation status identification method based on harmonic amplification factor of the above method embodiment of the present application, which will not be described in detail here.

[0116] In the embodiment of the present application, a computer-readable storage medium is also provided, and the computer-readable storage medium is a memory device in a computer device for storing programs and data. It is understandable that the computer-readable storage medium here can include both the built-in storage medium in the computer device and the extended storage medium supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory (non-volatile memory), such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the above-mentioned embodiment of a method for identifying the insulation state of a cable based on harmonic amplification. It should be understood by those skilled in the art that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0117] The specific implementation methods described above further illustrate the purpose, technical solutions and beneficial effects of the present application in detail. It should be understood that the above description is only the specific implementation method of the present application and is not intended to limit the scope of protection of the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A cable insulation status identification method based on harmonic amplification factor, characterized in that: Methods include: Constructing the correlation equation between the harmonic amplification factor of the cable and the equivalent impedance parameter of the Π-type equivalent circuit after the cable is equivalent; The equivalent impedance parameter is determined based on the complex dielectric constant of the cable's insulation material; the expression of the associated equation is: Among them, Z m , Z p are the series impedance and ground impedance of the cable Π-type equivalent circuit, F u is the harmonic voltage amplification factor, F i is the harmonic current amplification factor, is the ratio of harmonic voltage to harmonic current at the end of the cable; Obtain the harmonic amplitudes at both ends of the cable at the current moment, and calculate the harmonic amplification factor of the cable at the current moment based on the harmonic amplitudes; An objective function is constructed to minimize the residual sum of squares between the harmonic amplification factor represented by the correlation equation and the harmonic amplification factor at the current moment, and the Gauss-Newton iteration method is used to solve the objective function to obtain the index value of the cable insulation state; wherein the expression of the objective function is: Among them, argmin means optimization Minimize the residual sum of squares, is * The estimated value of K is the harmonic amplification factor, K T With K M are the theoretical value and measured value of K, K T is obtained from the correlation equation, h i is the i-th harmonic frequency, R is the total number of harmonic frequencies; Identify the insulation status of the cable based on the index value of the cable insulation status.

2. The method according to claim 1, characterized in that The equivalent impedance parameters are determined based on the complex dielectric constant of the cable's insulation material, specifically: Obtain the complex dielectric constant of the cable's insulation material and the cable's dimensional parameters; Calculate the cable's unit length admittance based on the complex dielectric constant and size parameters; The equivalent impedance parameters of the cable's Π-type equivalent circuit are calculated based on the cable's unit length admittance and the cable length; the equivalent impedance parameters include the series impedance and the ground impedance of the cable's Π-type equivalent circuit.

3. The method according to claim 1, characterized in that Get the harmonic amplitude at both ends of the cable at the current moment, and calculate the harmonic amplification factor of the cable at the current moment based on the harmonic amplitude, specifically: Obtain the harmonic voltage amplitude and harmonic current amplitude at both ends of the cable measured at the current moment; The harmonic voltage amplification factor is obtained by dividing the harmonic voltage amplitude at one end of the cable by the harmonic voltage amplitude at the other end; The harmonic current amplification factor is obtained by dividing the harmonic current amplitude at one end of the cable by the harmonic current amplitude at the other end; The harmonic voltage amplification factor is added to the harmonic current amplification factor to obtain the harmonic amplification factor of the cable at the current moment.

4. A cable insulation status identification device based on harmonic amplification factor, characterized in that: The device includes: The correlation equation construction module is used to construct the correlation equation between the harmonic amplification factor of the cable and the equivalent impedance parameter of the Π-type equivalent circuit after the cable is equivalent; wherein the equivalent impedance parameter is determined based on the complex dielectric constant of the insulating material of the cable; wherein the expression of the correlation equation is: Among them, Z m , Z p are the series impedance and ground impedance of the cable Π-type equivalent circuit, F u is the harmonic voltage amplification factor, F i is the harmonic current amplification factor, is the ratio of harmonic voltage to harmonic current at the end of the cable; The harmonic amplification factor calculation module is used to obtain the harmonic amplitudes at both ends of the cable at the current moment, and calculate the harmonic amplification factor of the cable at the current moment according to the harmonic amplitudes; The insulation index solving module is used to construct an objective function for minimizing the residual sum of squares between the harmonic amplification factor represented by the correlation equation and the harmonic amplification factor at the current moment, and solve the objective function using the Gauss-Newton iteration method to obtain the index value of the cable insulation state; wherein the expression of the objective function is: Among them, argmin means optimization Minimize the residual sum of squares, is * The estimated value of K is the harmonic amplification factor, K T With K M are the theoretical value and measured value of K, K T is obtained from the correlation equation, h i is the i-th harmonic frequency, R is the total number of harmonic frequencies; The insulation state identification module is used to identify the insulation state of the cable according to the index value of the insulation state of the cable.

5. The device according to claim 4, characterized in that Correlation equation building blocks, including: A cable parameter acquisition module is used to obtain the complex dielectric constant of the cable's insulation material and the cable's size parameters; Unit length admittance calculation module, used to calculate the unit length admittance of the cable based on the complex dielectric constant and size parameters; The equivalent impedance parameter calculation module is used to calculate the equivalent impedance parameters of the cable Π-type equivalent circuit based on the unit length admittance of the cable and the cable length; wherein the equivalent impedance parameters include the series impedance and the ground impedance of the cable Π-type equivalent circuit.

6. The device according to claim 4, characterized in that Harmonic amplification factor calculation module, including: A harmonic parameter acquisition module, used to obtain the harmonic voltage amplitude and harmonic current amplitude at both ends of the cable measured at the current moment; A harmonic voltage amplification factor calculation module is used to obtain the harmonic voltage amplification factor by dividing the harmonic voltage amplitude at one end of the cable by the harmonic voltage amplitude at the other end; A harmonic current amplification factor calculation module is used to obtain the harmonic current amplification factor by dividing the harmonic current amplitude at one end of the cable by the harmonic current amplitude at the other end; The harmonic voltage amplification factor is added to the harmonic current amplification factor to obtain the harmonic amplification factor of the cable at the current moment.

7. A computer device, characterized in that: The computer device includes a processor, a memory, and a computer program stored in the memory and executable by the processor, wherein when the computer program is executed by the processor, the steps of a cable insulation status identification method based on harmonic amplification factor as described in any one of claims 1 to 3 are implemented.

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