CN111999564A - Calculation method and calculation device of internal dielectric constant value of cable accessories - Google Patents

Abstract

The present application provides an internal dielectric constant value calculation method and a calculation device of a cable accessory, which are applied to the internal dielectric constant value calculation device of the cable accessory, wherein the internal dielectric constant value calculation device of the cable accessory includes an electrode array, At least two electrode pairs included in the electrode array are arranged around the side of the cable accessory, and the method includes: collecting the capacitance value between each electrode pair in the at least two electrode pairs; acquiring the internal dielectric constant distribution corresponding to the cable accessory and Coupling relationship for boundary capacitance information; based on the coupling relationship and the capacitance value between each of the at least two electrode pairs, calculates the value of the internal permittivity of the cable accessory. In this way, a flexible electrode array arrangement is adopted to meet the testing and installation requirements of cable accessories of different voltage levels and structures. Calculate the internal permittivity value of cable accessories through a non-invasive, real-time nondestructive testing method. The realization process is simple, convenient and quick.

Description

Calculation method and calculation device of internal dielectric constant value of cable accessories

technical field

The present application relates to the field of electric power technology, and in particular, to a calculation method and calculation device of an internal permittivity value of a cable accessory.

Background technique

In the cable transmission system, cable accessories are an important factor affecting the normal operation of the cable system. When installing a cable terminal, the outer shielding layer of a section of cable must be stripped off, resulting in uneven distribution of the electric field where the terminal is located, resulting in a tangential electric field that is unfavorable to insulation. In the prior art, the stress cone can be used to control the electric field strength of the terminal, which can homogenize the electric field to a certain extent and improve the electric field strength at the cut-off point of the shielding layer of the cable. The electric field distribution inside the stress cone can be optimized by adjusting the thickness, end curvature and axial length of the stress cone, but the optimization effect is limited.

With the improvement of the performance of the insulating material, the dielectric constant of the material can also be changed, so that the composite material has the function of homogenizing the AC electric field distribution, so as to achieve the purpose of improving the terminal electric field distribution. However, it is currently not possible to measure the internal permittivity value of cable accessories.

SUMMARY OF THE INVENTION

The present application provides a method and a computing device for calculating the internal dielectric constant value of a cable accessory, so as to solve the problem that the internal dielectric constant value of the cable accessory cannot be measured in the prior art.

In a first aspect, the present invention provides a method for calculating an internal permittivity value of a cable accessory, which is applied to a device for calculating an internal permittivity value of a cable accessory, wherein the device for calculating an internal permittivity value for the cable accessory includes an electrode array, At least two electrode pairs included in the electrode array are arranged around the side of the cable accessory, and the method includes:

collecting a capacitance value between each of the at least two electrode pairs;

obtaining the coupling relationship between the internal dielectric constant distribution corresponding to the cable accessory and the boundary capacitance information;

Based on the coupling relationship and a capacitance value between each of the at least two electrode pairs, an internal permittivity value of the cable accessory is calculated.

Further, the internal permittivity value calculation device of the cable accessory further includes a high-voltage power supply, and the high-voltage power supply is connected to each electrode pair of the at least two electrode pairs. Before the step of pairing the capacitance value between each electrode pair, the method further includes:

the high-voltage power supply outputs alternating current to each of the at least two electrode pairs;

The collecting the capacitance value between each electrode pair in the at least two electrode pairs includes:

A capacitance value between each of the at least two electrode pairs is collected with the alternating current passing between each of the at least two electrode pairs.

Further, at least two electrode pairs included in the electrode array are arranged around the inner wall side or the outer wall side of the cable accessory.

In a second aspect, the present invention also provides a device for calculating an internal permittivity value of a cable accessory, the device for calculating an internal permittivity value of the cable accessory includes an electrode array, and the electrode array includes at least two electrode pairs Around the side of the cable accessory, the internal dielectric constant value calculation device of the cable accessory includes:

a collection module, configured to collect a capacitance value between each of the at least two electrode pairs;

an acquisition module, used for acquiring the coupling relationship between the internal dielectric constant distribution corresponding to the cable accessory and the boundary capacitance information;

A calculation module, configured to calculate an internal permittivity value of the cable accessory according to the coupling relationship and a capacitance value between each of the at least two electrode pairs.

Further, the internal permittivity value calculation device of the cable accessory further includes a high-voltage power supply, and the high-voltage power supply is connected to each of the at least two electrode pairs;

the high-voltage power supply outputs alternating current to each of the at least two electrode pairs;

The acquisition module is specifically configured to acquire the capacitance value between each of the at least two electrode pairs when the alternating current is passed between each of the at least two electrode pairs .

Further, at least two electrode pairs included in the electrode array are arranged around the inner wall side or the outer wall side of the cable accessory.

It can be known from the above technical solutions that an embodiment of the present invention provides a method for calculating an internal permittivity value of a cable accessory and a calculating device, wherein the device for calculating an internal permittivity value of the cable accessory includes an electrode array, and the electrode array includes The at least two electrode pairs are arranged around the side of the cable accessory, and the method includes: collecting the capacitance value between each electrode pair in the at least two electrode pairs; obtaining the corresponding internal dielectric of the cable accessory The coupling relationship between the constant distribution and the boundary capacitance information; the internal dielectric constant value of the cable accessory is calculated according to the coupling relationship and the capacitance value between each of the at least two electrode pairs. In this way, a flexible electrode array arrangement is adopted to meet the testing and installation requirements of cable accessories of different voltage levels and structures. Calculate the internal permittivity value of cable accessories through a non-invasive, real-time nondestructive testing method. The realization process is simple, convenient and quick.

Description of drawings

In order to illustrate the technical solutions of the present application more clearly, the accompanying drawings required in the embodiments will be briefly introduced below. Obviously, for those of ordinary skill in the art, without creative work, the Additional drawings can be obtained from these drawings.

1 is a flowchart of a method for calculating an internal permittivity value of a cable accessory provided by the present invention;

2 is a schematic diagram of an electrode array provided by the present invention;

FIG. 3 is a structural diagram of a device for calculating an internal permittivity value of a cable accessory provided by the present invention.

Detailed ways

Embodiments will be described in detail below, examples of which are illustrated in the accompanying drawings. Where the following description refers to the drawings, the same numerals in different drawings refer to the same or similar elements unless otherwise indicated. The implementations described in the following examples are not intended to represent all implementations consistent with this application. are merely exemplary of systems and methods consistent with some aspects of the present application as recited in the claims.

Referring to FIG. 1 , FIG. 1 is a flow chart of a method for calculating an internal permittivity value of a cable accessory provided by the present invention, which is applied to an internal permittivity value calculating device for a cable accessory. The internal dielectric constant value calculation device of the cable accessory includes an electrode array, and at least two electrode pairs included in the electrode array are arranged around the side of the cable accessory. As shown in Figure 1, it includes the following steps:

Step 101: Collect a capacitance value between each of the at least two electrode pairs.

In step 101, a capacitance value between each of the at least two electrode pairs may be collected.

For the dielectric constant gradient cable accessories of different voltage levels, different electrode arrays can be designed, as well as the electrode arrangement inside and outside the cable accessories. A 24-electrode capacitance tomography (ECT) sensor with 8 sets of electrode rotation excitation measurement mode can be used. The independent measurement number of capacitance is similar to that of the traditional 12-electrode ECT sensor, which can better ensure the real-time imaging speed. At the same time, the measured capacitance value is large and the dynamic range is small, which reduces the difficulty of signal detection circuit design, improves the measurement accuracy, improves the balance of the sensitive field in the measurement area, and improves the imaging quality of the object in the center of the field.

In the power system, according to the voltage of the transmission line, it is divided into different voltage levels, such as 35kV, 110kV, 220kV, 330kV, 500kV, etc. The shape and size of the cable accessories in different voltage levels are different, and specific analysis is required when measuring .

The topology of the electrode array is the arrangement of the electrode array, including the number, size, and spatial position information of the electrodes. As shown in FIG. 2 , it is a schematic diagram of the electrode array. The electrode array is composed of a plurality of electrodes, and the electrodes are installed around the inner wall of the cable accessory at equal intervals, and are arranged in a ring-shaped parallel and neatly arranged on the inner wall of the cable accessory, or are arranged in parallel and crosswise.

Optionally, the internal permittivity value calculation device of the cable accessory further includes a high-voltage power supply, and the high-voltage power supply is connected to each electrode pair of the at least two electrode pairs. Before the step of the capacitance value between each of the electrode pairs, the method further includes:

the high-voltage power supply outputs alternating current to each of the at least two electrode pairs;

The collecting the capacitance value between each electrode pair in the at least two electrode pairs includes:

A capacitance value between each of the at least two electrode pairs is collected with the alternating current passing between each of the at least two electrode pairs.

It should be noted that the device for calculating the internal permittivity value of the cable accessory may further include a high-voltage power supply, and the high-voltage power supply is connected to each of the at least two electrode pairs. The high voltage power supply may output alternating current to each of the at least two electrode pairs. At this time, in the case of passing an alternating current between each of the at least two electrode pairs, the capacitance value between each of the at least two electrode pairs may be collected.

再根据高斯通量定理即可求出该电极板上的感应电荷量Q，即Knowing the dielectric constant distribution ε(x, y), calculate its potential distribution

Then according to the Gaussian flux theorem, the induced charge Q on the electrode plate can be obtained, that is,

In the formula, V is the potential difference between the two electrode plates, and D is the area of the electrode plates.

的离散值，进一步用离散形式的向量ε取代连续向量ε(x,y)，则依据上式，即可求出i-j电极对间的电容值。According to the above analysis, it can be found that

The discrete value of , and further replace the continuous vector ε(x, y) with the discrete vector ε, then according to the above formula, the capacitance value between the ij electrode pair can be obtained.

Step 102: Obtain the coupling relationship between the internal dielectric constant distribution corresponding to the cable accessory and the boundary capacitance information.

In step 102, the coupling relationship between the internal dielectric constant distribution corresponding to the cable accessory and the boundary capacitance information can be obtained. The electrostatic field simulation can be performed by simulating the Comsol software, the corresponding geometric and material properties can be established, and the coupling relationship (sensitive field matrix) can be determined by calculating the relationship between the internal material properties and the boundary capacitance information.

The sensitivity matrix algorithm is a dynamic imaging algorithm, so it is necessary to collect two sets of data in different states. The steps to obtain the dielectric constant distribution using the sensitivity matrix algorithm are as follows:

(1) Determine the geometric size and shape of the uniform field and divide it.

First, use finite element simulation software to model, establish the same model as the actual measurement structure, and perform mesh division. At this time, since the internal dielectric constant of the cable accessory is unknown, it is set as a homogeneous material, and then follow-up The material parameters are continuously adjusted and corrected through the algorithm until the measured value of the boundary capacitance is closer to the simulated value.

(2) A plurality of measurements of the potential distribution on the boundary electrodes are performed as data obtained by the measurements.

What is measured is the capacitance value between different electrode pairs at the boundary. This value is the reference value, and the simulation process is to continuously adjust the internal dielectric constant distribution, so that the boundary capacitance obtained by the simulation is close to this value.

(3) Set the initial dielectric constant distribution.

Since the internal dielectric constant of the structure to be tested is unknown, it is necessary to set the initial value during the simulation process, where the initial dielectric constant is uniform, that is, the dielectric constant of the homogeneous cable accessories, according to the initial dielectric constant Distribution, simulation to obtain the initial boundary capacitance, and then use the difference between this capacitance and the actual measured capacitance, and then feed back to the adjustment of the dielectric constant value, and iterate continuously to obtain the real dielectric constant value.

(4) Calculate the coefficient matrix S (coupling relation).

While calculating the boundary capacitance, the sensitivity matrix between different electrodes is calculated according to the potential distribution information obtained by the finite element calculation. The specific calculation formula is as follows:

和

分别当电极i为激励电极和j为激励电极时在(x,y)处的电位分布。V为两电极之间的电位差。where Sij(k) is the sensitivity distribution between electrodes i and j, _ε0 is the vacuum permittivity,

and

Potential distribution at (x, y) when electrode i is the excitation electrode and j is the excitation electrode, respectively. V is the potential difference between the two electrodes.

(5) A new dielectric constant distribution in the field is obtained.

According to the sensitivity matrix obtained from the simulation, combined with the difference between the measured boundary capacitance and the simulated boundary capacitance, the dielectric constant difference calculated by the regularization algorithm is used to obtain the new dielectric constant. constant.

The method of establishing the sensitive field by means of numerical simulation has high efficiency, and can directly extract the sensitivity distribution in the field, which avoids the problems of low efficiency and poor accuracy in the actual measurement process.

Step 103: Calculate the internal permittivity value of the cable accessory according to the coupling relationship and the capacitance value between each of the at least two electrode pairs.

In step 103, an internal permittivity value of the cable accessory may be calculated according to the coupling relationship and the capacitance value between each of the at least two electrode pairs.

Through the high-performance regularized nonlinear inversion algorithm, the dielectric constant distribution information of the inner space of the cable accessory is reconstructed according to the output capacitance distribution information.

ΔC=SΔε

In the above formula, S is the sensitive field matrix (the new dielectric constant distribution is obtained through the sensitive matrix), ΔC is the boundary capacitance information, and Δε is the internal dielectric constant value. In fact, the internal permittivity value is obtained by solving the above formula. However, this inversion process is non-linear and cannot be directly inverted, so a regularization algorithm needs to be used to ensure that the calculation results are closer to the true value.

The regularized Gauss-Newton algorithm can be used to calculate the ECT inverse problem. The steps are as follows:

(1) The initial value of the regularized Gauss-Newton algorithm is set to the dielectric constant distribution value of the uniform field, and the capacitance distribution on the boundary electrode is calculated;

(2) Calculate the Jacobian matrix, and the iteration step size h _TRGN and the new dielectric constant distribution can be obtained by the following formula:

Among them, F(ε) is the potential on the boundary electrode obtained from the existing dielectric constant distribution, C is the measured value of the boundary capacitance, and ε is the dielectric constant distribution of the measured field. The mutual relationship between the subdivision elements can be represented by a modulation matrix R. The construction rule of the matrix R is: assuming that R is an N×N matrix, the number of elements divided by the finite element model is N. α is the relaxation iteration coefficient.

(3) Solve the ECT positive problem, so as to obtain the capacitance on the boundary electrode under the dielectric constant distribution;

(4) Calculate the following formula, and judge whether the result meets the conditions for ending the algorithm. If so, the iteration ends, otherwise return (2).

where f(ε) is the measured value C of the boundary capacitance as a function of the dielectric constant ε.

According to the above steps, the dielectric constant value can be calculated.

Using the nonlinearity of the regularized inversion algorithm can approximate the nonlinearity of the sensitive field of the electromagnetic inverse problem, so that it can have a high inversion accuracy.

Optionally, at least two electrode pairs included in the electrode array are arranged around the inner wall side or the outer wall side of the cable accessory.

It should be noted that, at least two electrode pairs included in the electrode array can be arranged around the inner wall side or the outer wall side of the cable accessory. The cable attachment is a hollow structure, divided into inner and outer sides, with two faces, the inner wall side refers to the inner face, and the outer wall side refers to the outer face.

It can be seen from the above technical solutions that the method for calculating the internal dielectric constant value of a cable accessory provided by the embodiment of the present invention is applied to the internal dielectric constant value calculating device of the cable accessory, and the internal dielectric constant value calculating device of the cable accessory is applied. An electrode array is included, and at least two electrode pairs included in the electrode array are arranged around the side of the cable accessory, and the method includes: collecting a capacitance value between each electrode pair in the at least two electrode pairs; Obtain the coupling relationship between the internal dielectric constant distribution corresponding to the cable accessory and the boundary capacitance information; according to the coupling relationship and the capacitance value between each electrode pair in the at least two electrode pairs, calculate the Internal dielectric constant value. In this way, a flexible electrode array arrangement is adopted to meet the testing and installation requirements of cable accessories of different voltage levels and structures. Calculate the internal permittivity value of cable accessories through a non-invasive, real-time nondestructive testing method. The realization process is simple, convenient and quick.

Referring to FIG. 3 , FIG. 3 is a structural diagram of a device for calculating the internal permittivity value of a cable accessory provided by the present invention. The internal permittivity value calculation device 300 of the cable accessory includes an electrode array, and at least two electrode pairs included in the electrode array are arranged around the side of the cable accessory. As shown in FIG. 3 , the internal dielectric constant value calculation device 300 of the cable accessory includes a collection module 301, an acquisition module 302 and a calculation module 303, wherein:

a collection module 301, configured to collect a capacitance value between each of the at least two electrode pairs;

an acquisition module 302, configured to acquire the coupling relationship between the internal permittivity distribution corresponding to the cable accessory and the boundary capacitance information;

The calculation module 303 is configured to calculate the internal permittivity value of the cable accessory according to the coupling relationship and the capacitance value between each of the at least two electrode pairs.

Optionally, the internal dielectric constant value calculation device of the cable accessory further includes a high-voltage power supply, and the high-voltage power supply is connected to each of the at least two electrode pairs;

the high-voltage power supply outputs alternating current to each of the at least two electrode pairs;

The collection module 301 is specifically configured to collect the capacitance between each of the at least two electrode pairs when the alternating current is passed between each of the at least two electrode pairs value.

Optionally, at least two electrode pairs included in the electrode array are arranged around the inner wall side or the outer wall side of the cable accessory.

The device 300 for calculating the internal permittivity value of the cable accessory can implement various processes implemented by the device for calculating the internal permittivity value of the cable accessory in the method embodiment of FIG. In addition, the internal dielectric constant value calculation device 300 of the cable accessory can adopt a flexible electrode array arrangement to meet the testing and installation requirements of cable accessories with different voltage levels and structures. Calculate the internal permittivity value of cable accessories through a non-invasive, real-time nondestructive testing method. The realization process is simple, convenient and quick.

Similar parts between the embodiments provided in the present application may be referred to each other. The specific embodiments provided above are just a few examples under the general concept of the present application, and do not constitute a limitation on the protection scope of the present application. For those skilled in the art, any other implementations expanded according to the solution of the present application without creative work fall within the protection scope of the present application.

Claims (6)

1. A method for calculating an internal dielectric constant value of a cable accessory is applied to an internal dielectric constant calculating device of the cable accessory, and is characterized in that the internal dielectric constant calculating device of the cable accessory comprises an electrode array, at least two electrode pairs contained in the electrode array are arranged on the side face of the cable accessory in a surrounding mode, and the method comprises the following steps:

collecting capacitance values between each electrode pair of the at least two electrode pairs;

acquiring the coupling relation between the internal dielectric constant distribution corresponding to the cable accessory and the boundary capacitance information;

and calculating the internal dielectric constant value of the cable accessory according to the coupling relation and the capacitance value between each electrode pair in the at least two electrode pairs.

2. The method of claim 1, wherein the internal permittivity calculation means of the cable accessory further comprises a high voltage power supply connected to each electrode pair of the at least two electrode pairs, the method further comprising, prior to the step of acquiring a capacitance value between each electrode pair of the at least two electrode pairs:

the high-voltage power supply outputs alternating current to each electrode pair of the at least two electrode pairs;

the acquiring capacitance values between each electrode pair of the at least two electrode pairs comprises:

acquiring a capacitance value between each electrode pair of the at least two electrode pairs under the condition that the alternating current passes between each electrode pair of the at least two electrode pairs.

3. The method of claim 1 or 2, wherein the electrode array comprises at least two electrode pairs disposed around the inner wall side or the outer wall side of the cable accessory.

4. An internal dielectric constant calculation device of an electrical cable accessory, the internal dielectric constant calculation device of the electrical cable accessory comprising an electrode array, at least two electrode pairs included in the electrode array being disposed around a side surface of the electrical cable accessory, the internal dielectric constant calculation device of the electrical cable accessory comprising:

the acquisition module is used for acquiring capacitance values between each electrode pair in the at least two electrode pairs;

the acquisition module is used for acquiring the coupling relation between the internal dielectric constant distribution corresponding to the cable accessory and the boundary capacitance information;

and the calculation module is used for calculating the internal dielectric constant value of the cable accessory according to the coupling relation and the capacitance value between each electrode pair in the at least two electrode pairs.

5. The electrical cable accessory internal permittivity calculation device of claim 4, further comprising a high voltage power supply connected to each electrode pair of the at least two electrode pairs;

the high-voltage power supply outputs alternating current to each electrode pair of the at least two electrode pairs;

the acquisition module is specifically configured to acquire a capacitance value between each electrode pair of the at least two electrode pairs when the alternating current is passed between each electrode pair of the at least two electrode pairs.

6. The apparatus according to claim 4 or 5, wherein the electrode array comprises at least two electrode pairs disposed around the inner wall side or the outer wall side of the cable accessory.

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