阅读说明：本技术 一种换流变压器固体绝缘含水量的测试方法 (Method for testing water content of solid insulation of converter transformer ) 是由 崔律 周行星 陈俊杰 李红雷 陈炯 于 2020-11-17 设计创作，主要内容包括：本发明涉及一种换流变压器固体绝缘含水量的测试方法,包括以下步骤：获取待测换流变压器的结构参数、绝缘油电导率、不同含水量固体绝缘的复介电常数；计算待测换流变压器的FDS模型曲线；基于FDS法测量待测换流变压器固体绝缘的频域介电谱曲线；选择与频域介电谱曲线误差最小的FDS模型曲线,该模型曲线的固体绝缘含水量即为测试结果。与现有技术相比,本发明使用FDS法测量换流变压器的固体绝缘含水量,先计算待测换流变压器的FDS模型曲线,再测量得到待测换流变压器的频域介电谱曲线,找到与频域介电谱曲线最接近的FDS模型曲线,从而确定待测换流变压器的固体绝缘含水量,满足换流变压器的现场诊断需求,不破坏换流变压器绝缘结构,精度较高。(The invention relates to a method for testing the water content of solid insulation of a converter transformer, which comprises the following steps: acquiring structural parameters of a converter transformer to be tested, the conductivity of insulating oil and the complex dielectric constants of solid insulation with different water contents; calculating an FDS model curve of the converter transformer to be tested; measuring a frequency domain dielectric spectrum curve of the solid insulation of the converter transformer to be measured based on an FDS method; and selecting an FDS model curve with the minimum error with the frequency domain dielectric spectrum curve, wherein the solid insulation water content of the model curve is the test result. Compared with the prior art, the method has the advantages that the solid insulation water content of the converter transformer is measured by using an FDS method, the FDS model curve of the converter transformer to be measured is calculated firstly, then the frequency domain dielectric spectrum curve of the converter transformer to be measured is obtained through measurement, and the FDS model curve closest to the frequency domain dielectric spectrum curve is found, so that the solid insulation water content of the converter transformer to be measured is determined, the field diagnosis requirement of the converter transformer is met, the insulation structure of the converter transformer is not damaged, and the precision is high.)

1. A method for testing the water content of solid insulation of a converter transformer is characterized by comprising the following steps:

s1: acquiring structural parameters of a converter transformer to be tested and the electrical conductivity sigma of insulating oil, and acquiring complex dielectric constants of solid insulation with different water contents at a test temperature;

s2: calculating to obtain a plurality of FDS model curves of the converter transformer to be tested according to the structural parameters, the conductivity sigma of the insulating oil and the complex dielectric constants of the solid insulation with different water contents, wherein each FDS model curve corresponds to different water contents of the solid insulation;

s3: measuring and obtaining a frequency domain dielectric spectrum curve of the solid insulation of the converter transformer to be measured based on a frequency domain dielectric spectrum method;

s4: and selecting the FDS model curve with the minimum error with the frequency domain dielectric spectrum curve from the plurality of FDS model curves obtained in the step S2, wherein the solid insulation water content corresponding to the FDS model curve is the solid insulation water content of the converter transformer to be tested, and recording the solid insulation water content as a test result.

2. The method for testing the water content of the solid insulation of the converter transformer according to claim 1, wherein the complex dielectric constant of the solid insulation comprises the complex dielectric constant of a paperboard and the complex dielectric constant of a strut.

3. The method for testing the water content of the solid insulation of the converter transformer according to claim 2, wherein in the step S1, the temperature correction is performed on the angular frequency of the complex dielectric constant of the solid insulation at the test temperature T based on an Arrhenius model, and the specific formula is as follows:

wherein, ω is_TDenotes the angular frequency, ω, at the test temperature T₂₀Representing the angular frequency at 20 ℃, W representing the activation energy of the cardboard or strut dielectric material, k representing the Boltzmann constant, Δ T being the temperature difference in units of thermodynamic units Kelvin, T₂₀Represents 20 ℃.

4. The method for testing the water content of the solid insulation of the converter transformer according to claim 2, wherein in the step S2, the calculation formula of the FDS model curve is specifically as follows:

wherein epsilon^*(ω，T)_{Integral body}The complex dielectric constant of the whole insulation system of the converter transformer is shown, X and Y are structural parameters of the converter transformer, X is the ratio of the sum of the thicknesses of all paper boards in the insulation system of the converter transformer to the sum of the thicknesses of all supporting strips, Y is the ratio of the sum of the widths of all supporting strips in the insulation system of the converter transformer to the sum of the widths of all paper boards,respectively showing the complex dielectric constants of the stay, the paperboard and the insulating oil, epsilon' shows the real part of the complex dielectric constant of the insulating oil, sigma shows the conductivity of the insulating oil, epsilon₀Denotes the vacuum dielectric constant and ω denotes the angular frequency.

5. The method for testing the water content of the solid insulation of the converter transformer according to claim 4, wherein in the step S2, the value of ε' is 2.2.

6. The method for testing the water content of the solid insulation of the converter transformer according to claim 1, wherein the step S3 comprises the following steps:

s31: the method comprises the steps that a network side sleeve lead and a valve side sleeve lead of a converter transformer to be tested are unfastened, and a tap switch of the converter transformer to be tested is adjusted to a rated gear;

s32: the method comprises the following steps of short-circuiting two ends of a valve side winding of a converter transformer to be tested, connecting the two ends to a high-voltage output end of a frequency domain dielectric spectrum tester through a shielding signal wire, short-circuiting two ends of a network side winding of the converter transformer to be tested, and connecting the two ends to a high-voltage response end of the frequency domain dielectric spectrum tester through the shielding signal wire;

s33: setting a measuring frequency band of a frequency domain dielectric spectrum tester, and setting a test voltage;

s34: the measurement data is measured and recorded.

7. The method for testing the water content of the solid insulation of the converter transformer according to claim 6, wherein in the step S33, the measurement frequency band is 0.01 Hz-1000 Hz.

8. The method for testing the water content of the solid insulation of the converter transformer according to claim 7, wherein in the step S33, the test voltage is 140V.

9. The method for testing the water content of the solid insulation of the converter transformer according to claim 1, wherein the step S4 specifically comprises: and (4) optimally approximating the frequency domain dielectric spectrum curve and the plurality of FDS model curves obtained in the step (S2) by adopting a least square method to obtain the FDS model curve with the minimum error with the frequency domain dielectric spectrum curve, wherein the solid insulation water content corresponding to the FDS model curve is the solid insulation water content of the converter transformer to be detected.

10. The method for testing the water content of the solid insulation of the converter transformer according to claim 1, further comprising the step S5: and repeating the step S3 until the repetition times are equal to the preset measurement times to obtain a plurality of groups of test results, removing abnormal data in the test results, calculating an average value, and taking the average value as a final measurement result.

Technical Field

The invention relates to the field of power transmission detection, in particular to a method for testing the water content of solid insulation of a converter transformer.

Background

The converter transformer is core equipment of a direct-current transmission project, and whether the insulation state of the converter transformer is good or not directly relates to safe and stable operation of a power grid. The water content of solid insulation (mainly composed of cellulose insulation paper, insulation paper boards and supporting strips) of the converter transformer can reflect the insulation state and the aging degree of the converter transformer, and the method has important significance for predicting the residual life of the converter transformer and diagnosing faults.

At present, the method for measuring the water content of the solid insulation of the converter transformer is mainly a chemical measurement method for extracting a paper sample, and although the chemical measurement method is high in precision, the insulation of the converter transformer needs to be damaged, so that the method is not suitable for field diagnosis of the converter transformer.

In the field of insulation measurement, frequency domain dielectric spectroscopy (FDS) is an electrical measurement method based on dielectric characteristics, the FDS is low in noise interference degree, low in test voltage and rich in carried information, and is more suitable for field diagnosis of an insulation state. However, the FDS method has some disadvantages in the measurement of the insulation state. The measured object of the FDS method is an oil-immersed insulation system, and due to the fact that the design and production processes of different manufacturers are different, factors such as the type of a solid insulation material, the thickness of the material, the weight of the material, the quality of insulating oil, the volume of the insulating oil, impurities and the like can be reflected in a measurement result. If the material properties selected in the simulation test in the laboratory are far from the actual products, or the factors such as the material type, the winding structure, the oilpaper proportion and the like of the tested equipment are unknown during the field test, the best approximation between the model curve and the tested waveform is often difficult to obtain, and the state of the whole insulation system is difficult to accurately judge.

In addition, in the prior art, the FDS method is mainly used for measuring the insulation state of the alternating-current transformer, and no case of measuring the water content of the solid insulation of the converter transformer by using the FDS method is seen yet. And because the main insulation at the valve side of the converter transformer needs to face various working conditions such as direct current voltage, harmonic waves, commutation pulses, polarity inversion and the like, the insulation structure of the converter transformer is different from that of the alternating current transformer, the FDS curve model of the converter transformer is different from that of the alternating current transformer, and the direct measurement of the converter transformer by using the FDS model of the alternating current transformer causes large errors.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a method for testing the water content of the solid insulation of the converter transformer, which comprises the steps of measuring the water content of the solid insulation of the converter transformer by using an FDS (fully drawn sheet), firstly calculating an FDS (frequency domain signal) model curve corresponding to the structure of the converter transformer to be tested, then measuring the solid insulation of the converter transformer by using an FDS method to obtain a frequency domain dielectric spectrum curve, and finding the FDS model curve closest to the frequency domain dielectric spectrum curve, thereby determining the water content of the solid insulation of the converter transformer to be tested, meeting the field diagnosis requirement of the converter transformer without damaging the insulation structure of the converter transformer and having higher precision.

The purpose of the invention can be realized by the following technical scheme:

a method for testing the water content of solid insulation of a converter transformer comprises the following steps:

s1: acquiring structural parameters of a converter transformer to be tested and the electrical conductivity sigma of insulating oil, and acquiring complex dielectric constants of solid insulation with different water contents at a test temperature;

s2: calculating to obtain a plurality of FDS model curves of the converter transformer to be tested according to the structural parameters, the conductivity sigma of the insulating oil and the complex dielectric constants of the solid insulation with different water contents, wherein each FDS model curve corresponds to different water contents of the solid insulation;

s3: measuring and obtaining a frequency domain dielectric spectrum curve of the solid insulation of the converter transformer to be measured based on a frequency domain dielectric spectrum method;

s4: and selecting the FDS model curve with the minimum error with the frequency domain dielectric spectrum curve from the plurality of FDS model curves obtained in the step S2, wherein the solid insulation water content corresponding to the FDS model curve is the solid insulation water content of the converter transformer to be tested, and recording the solid insulation water content as a test result.

Further, the complex dielectric constant of the solid insulation comprises the complex dielectric constant of the paperboard and the complex dielectric constant of the stay.

Furthermore, in step S1, the temperature correction is performed on the angular frequency of the complex dielectric constant of the solid insulation at the test temperature T based on the Arrhenius model, and the specific formula is as follows:

wherein, ω is_TDenotes the angular frequency, ω, at the test temperature T₂₀Representing the angular frequency at 20 ℃, W representing the activation energy of the cardboard or strut dielectric material, k representing the Boltzmann constant, Δ T being the temperature difference in units of thermodynamic units Kelvin, T₂₀Represents 20 ℃.

Further, in step S2, the calculation formula of the FDS model curve is specifically as follows:

wherein epsilon^*(ω，T)_{Integral body}The complex dielectric constant of the whole insulation system of the converter transformer is shown, X and Y are structural parameters of the converter transformer, X represents the ratio of the sum of all the thicknesses of paperboards to the sum of all the thicknesses of supporting strips in the insulation system of the converter transformer, and Y represents the ratio of the sum of all the thicknesses of supporting strips in the insulation system of the converter transformerThe ratio of the sum of the widths of all the stays to the sum of the widths of all the sheets in the insulation system of the transformer,respectively showing the complex dielectric constants of the stay, the paperboard and the insulating oil, epsilon' shows the real part of the complex dielectric constant of the insulating oil, sigma shows the conductivity of the insulating oil, epsilon₀Denotes the vacuum dielectric constant and ω denotes the angular frequency.

Furthermore, in step S2, the value of ∈' is 2.2.

Further, the step S3 includes the following steps:

s31: the method comprises the steps that a network side sleeve lead and a valve side sleeve lead of a converter transformer to be tested are unfastened, and a tap switch of the converter transformer to be tested is adjusted to a rated gear;

s32: the method comprises the following steps of short-circuiting two ends of a valve side winding of a converter transformer to be tested, connecting the two ends to a high-voltage output end of a frequency domain dielectric spectrum tester through a shielding signal wire, short-circuiting two ends of a network side winding of the converter transformer to be tested, and connecting the two ends to a high-voltage response end of the frequency domain dielectric spectrum tester through the shielding signal wire;

s33: setting a measuring frequency band of a frequency domain dielectric spectrum tester, and setting a test voltage;

s34: the measurement data is measured and recorded.

Furthermore, in step S33, the measurement frequency band is 0.01Hz to 1000 Hz.

Further, in step S33, the test voltage is 140V.

Further, the step S4 is specifically: and (4) optimally approximating the frequency domain dielectric spectrum curve and the plurality of FDS model curves obtained in the step (S2) by adopting a least square method to obtain the FDS model curve with the minimum error with the frequency domain dielectric spectrum curve, wherein the solid insulation water content corresponding to the FDS model curve is the solid insulation water content of the converter transformer to be detected.

Further, the method also includes step S5: and repeating the step S3 until the repetition times are equal to the preset measurement times to obtain a plurality of groups of test results, removing abnormal data in the test results, calculating an average value, and taking the average value as a final measurement result.

Compared with the prior art, the invention has the following beneficial effects:

(1) the method comprises the steps of measuring the water content of the solid insulation of the converter transformer by using FDS, firstly calculating an FDS model curve corresponding to the structure of the converter transformer to be measured, then measuring the solid insulation of the converter transformer by using an FDS method to obtain a frequency domain dielectric spectrum curve, and finding the FDS model curve closest to the frequency domain dielectric spectrum curve, so that the water content of the solid insulation of the converter transformer to be measured is determined, the field diagnosis requirement of the converter transformer is met, the insulation structure of the converter transformer is not damaged, and the precision is high.

(2) The testing frequency range is wide, and the information content contained in the testing result is more abundant than the power frequency dielectric loss measuring items; the test voltage is low, the test wiring is simple, the test time is short, no complex operation is needed, the field implementation is convenient, and the time cost and the labor cost are saved.

(3) When an FDS model curve is calculated, firstly, the angular frequency of the complex dielectric constant of the solid insulation at the test temperature T is subjected to temperature correction based on an Arrhenius model, so that the test precision is improved, and the temperature correction is more accurate.

Drawings

FIG. 1 is a flow chart of the present invention;

FIG. 2 is an equivalent circuit diagram of the measurement model in the example.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

Example 1:

in order to meet the field test requirement of the converter transformer and not to damage the insulation structure of the converter transformer, the solid insulation water content of the converter transformer is measured by using an FDS method, and a measurement model equivalent circuit diagram is shown in FIG. 2.

A method for testing the water content of solid insulation of a converter transformer is shown in figure 1 and comprises the following steps:

s1: and acquiring the structural parameters of the converter transformer to be tested and the electrical conductivity sigma of the insulating oil, and acquiring the complex dielectric constants of the solid insulation with different water contents at the test temperature.

Specifically, the main insulation on the valve side of the converter transformer needs to face various working conditions such as direct-current voltage, harmonic waves, commutation pulses, polarity inversion and the like, the insulation structure of the converter transformer is different from that of the alternating-current transformer, the difference exists between an FDS curve model of the converter transformer and the alternating-current transformer, and a large error is caused when the converter transformer is directly measured by using the alternating-current transformer FDS model. Therefore, the FDS model curve corresponding to the insulation structure of the converter transformer to be measured is calculated first, and then the best approximation is obtained between the FDS model curve and actual measurement data.

When calculating the FDS model curve, it is necessary to obtain the structural parameters of the converter transformer to be tested and the electrical conductivity σ of the insulating oil, and obtain the complex dielectric constants of the solid insulation with different water contents at the test temperature.

In this embodiment, the structural parameter X and the structural parameter Y can be directly obtained according to the specification parameter and the instruction manual of the converter transformer to be tested. X represents the ratio of the sum of the thicknesses of all paperboards and the sum of the thicknesses of all supporting strips in an insulation system of the converter transformer, the value range of X is 15-55%, and in the embodiment, the structural parameter X is 30%; y represents the ratio of the sum of the widths of all the supporting bars in the insulation system of the converter transformer to the sum of the widths of all the paper boards, and the value range of the structural parameter Y is 15% -25%, in the embodiment, the structural parameter Y is 20%.

The complex dielectric constant of the solid insulation includes the complex dielectric constant of the paperboard and the complex dielectric constant of the struts. According to the specification of the solid insulation of the converter transformer, complex dielectric constants of paperboards and supporting strips with different water contents at 20 ℃ can be obtained. However, since the test temperature T may not be equal to 20 ℃ when measured in the field, a temperature correction is required.

The method is characterized in that the temperature correction is carried out on the angular frequency of the complex dielectric constant of the solid insulation at the test temperature T based on an Arrhenius model, and the specific formula is as follows:

wherein, ω is_TDenotes the angular frequency, ω, at the test temperature T₂₀The angular frequency at 20 ℃, W represents the activation energy of the paperboard or bracing dielectric material, W is usually 0.9 eV-1.4 eV, k represents the Boltzmann constant, and the value is 1.38065 x 10^{- 23}J/K, Δ T is the temperature difference in units of thermodynamic Kelvin K, T₂₀Represents 20 ℃.

S2: and calculating to obtain a plurality of FDS model curves of the converter transformer to be tested according to the structural parameters, the conductivity sigma of the insulating oil and the complex dielectric constants of the solid insulation with different water contents, wherein each FDS model curve corresponds to different water contents of the solid insulation.

Calculating the complex dielectric constant of the insulating oil according to the conductivity sigma of the insulating oil:

ε' represents the real part of the complex permittivity of the insulating oil, usually taken as 2.2, σ represents the conductivity of the insulating oil, ε₀Denotes the vacuum dielectric constant and ω denotes the angular frequency.

And then calculating an FDS model curve according to the structural parameter X, the structural parameter Y, the complex dielectric constant of the insulating oil and the corrected complex dielectric constant of the solid insulation, wherein the calculation formula specifically comprises the following steps:

wherein epsilon^*(ω，T)_{Integral body}The complex dielectric constant of the whole insulation system of the converter transformer is shown, X and Y are structural parameters of the converter transformer, and X represents the sum of the thicknesses of all paperboards in the insulation system of the converter transformer and the sum of the thicknessesThe ratio of the sum of the thicknesses of the stay strips, Y represents the ratio of the sum of the widths of all the stay strips to the sum of the widths of all the paper plates in the insulation system of the converter transformer,the complex dielectric constants of the bar, the cardboard and the insulating oil are shown.

And calculating to obtain a plurality of FDS model curves, wherein each FDS model curve corresponds to different solid insulation water contents.

S3: the method for measuring and obtaining the frequency domain dielectric spectrum curve of the solid insulation of the converter transformer to be measured based on the frequency domain dielectric spectrum method comprises the following steps:

s31: unfastening a network side sleeve lead and a valve side sleeve lead of the converter transformer to be tested, adjusting a tap switch of the converter transformer to be tested to a rated gear, and grounding adjacent conductors (such as metal structures and the like) of the converter transformer to be tested;

s32: the method comprises the steps that two ends of a valve side winding of a converter transformer to be tested are in short circuit, the valve side winding is connected to a high-voltage output end of a frequency domain dielectric spectrum tester through a shielding signal wire, two ends of a network side winding of the converter transformer to be tested are in short circuit, the network side winding is connected to a high-voltage response end of the frequency domain dielectric spectrum tester through the shielding signal wire, and in order to prevent interference and test safety, the wiring and adjacent conductors (such as metal structures and the like) of the converter transformer to be tested are kept at a distance of more;

s33: setting a measuring frequency band of the frequency domain dielectric spectrum tester, setting a test voltage, wherein the measuring frequency band is 0.01Hz to 1000Hz, and applying 140V of the test voltage.

S34: and measuring and recording measurement data, wherein the measurement data can be displayed in various modes such as graphs, tables, data and the like.

S4: and selecting the FDS model curve with the minimum error with the frequency domain dielectric spectrum curve from the plurality of FDS model curves obtained in the step S2, wherein the solid insulation water content corresponding to the FDS model curve is the solid insulation water content of the converter transformer to be tested, and recording the solid insulation water content as a test result.

The method specifically comprises the following steps: and (4) optimally approximating the frequency domain dielectric spectrum curve and the plurality of FDS model curves obtained in the step (S2) by adopting a least square method to obtain the FDS model curve with the minimum error with the frequency domain dielectric spectrum curve, wherein the solid insulation water content corresponding to the FDS model curve is the solid insulation water content of the converter transformer to be detected.

In this embodiment, the solid insulation moisture content corresponding to the FDS model curve with the minimum error of the frequency domain dielectric spectrum curve is 0.6%.

In order to eliminate the influence of accidental factors on the measurement result, the measurement can be carried out for multiple times.

Step S5: and repeating the step S3 until the repetition times are equal to the preset measurement times to obtain a plurality of groups of test results, removing abnormal data in the test results, calculating an average value, and taking the average value as a final measurement result.

The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.