CN112798663A - Method and system for evaluating moisture content of oil-immersed paperboard in oil-immersed power equipment - Google Patents
Method and system for evaluating moisture content of oil-immersed paperboard in oil-immersed power equipment Download PDFInfo
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Abstract
The invention discloses a method and a system for evaluating the moisture content of an oil-immersed paperboard in oil-immersed power equipment. The method can effectively represent the influence of moisture on the relaxation polarization process inside the oil-immersed paperboard system, so as to evaluate the moisture content of the oil-immersed paperboard system, and can provide a new idea for evaluating the moisture content of the oil-immersed power equipment.
Description
Technical Field
The invention relates to the field of insulation state assessment of oil-immersed power equipment, in particular to a method and a system for assessing the moisture content of an oil-immersed paperboard in the oil-immersed power equipment.
Background
With the gradual development of extra-high voltage transmission projects, safe and reliable operation of oil-immersed power equipment is particularly important. In actual operation, the oil-immersed power equipment is susceptible to deterioration caused by moisture, electrical stress, thermal stress, mechanical stress and the like, wherein the moisture is the most recognized main factor influencing the performance of the oil-immersed paperboard system. IEEE Std C57.91-1995 also shows that moisture can accelerate insulation failure of oil-immersed power equipment such as transformers and bushings. Therefore, diagnosing and evaluating the moisture content has important engineering value for maintaining the safe and stable operation of the power equipment.
The insulation moisture of the oil-immersed power equipment mainly comes from residual moisture inside the insulation during the production and manufacturing of the power equipment, external environment moisture in the maintenance or actual operation process of the power equipment and moisture generated by insulation degradation. The traditional water detection method comprises a Karl Fischer method, an oilpaper water balance curve method and the like, but the traditional method is easily influenced by factors such as environment, inconvenience in field use and the like. In recent years, Polarization and depolarization current methods (PDC) and Frequency domain dielectric spectroscopy (FDS) have been increasingly applied to the diagnosis and evaluation of insulation performance and moisture content of oil-immersed power equipment, based on dielectric response and as a non-destructive inspection technique. Researchers at home and abroad use the time-frequency domain dielectric measurement technology to carry out a great deal of research on the evaluation of the affected state of the oil-immersed power equipment, and obtain more valuable research results. The research results show that the damp can obviously increase the dielectric loss and the capacitance, and the water content of the sleeve is evaluated by taking the ratio of the capacitance value at the characteristic frequency point to the capacitance value at the power frequency point as the characteristic quantity. The influence of moisture on the frequency domain dielectric property of silicone oil paper and mineral oil-impregnated paper boards is researched by Dun waves and the like, and research results show that the dielectric loss of the oil-impregnated paper boards is gradually increased along with the increase of the moisture content. And carrying out frequency domain dielectric tests on oil-immersed cellulose paperboards containing different moisture contents by Liujifeng and the like, wherein research results show that the moisture has obvious influence on the frequency domain dielectric characteristics of the oil-immersed cellulose paperboards, and characteristic quantities are extracted from frequency domain dielectric curves to quantify the influence of the moisture. Lundgaard and the like perform frequency domain dielectric spectrum tests on oil-immersed paperboards with three different moisture contents, and research results show that the relative dielectric constant of a low-frequency region is greatly influenced by moisture, and the relative dielectric constant of a high-frequency region is basically not influenced by moisture.
At present, most studies extract characteristic quantities directly from frequency domain dielectric spectral curves to quantitatively evaluate the influence of moisture. However, the traditional frequency domain dielectric spectrum FDS is easily influenced by a direct current conduction process, so that the low-frequency dielectric constant is too large, and the internal relaxation polarization process capable of accurately reflecting the state of the oil-immersed paperboard and being affected with damp is further inhibited.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method for evaluating the moisture content of an oil-immersed paperboard in oil-immersed power equipment (an oil-immersed transformer, an oil-immersed bushing and the like). The method for extracting the characteristic quantity from the dielectric modulus spectrum DMS to evaluate the moisture content of the oil-immersed paperboard can provide a new idea for evaluating the moisture content of the oil-immersed power equipment.
In order to achieve the above object, the present invention provides a method for estimating moisture content of an oil-immersed paperboard in an oil-immersed power equipment, comprising the following steps:
1) preparing oil-immersed paper boards with different moisture degrees (the moisture content is 0.5% -5%):
placing a plurality of oil-immersed paper boards in air to absorb moisture naturally (the moisture absorption degree is determined by controlling the natural moisture absorption time), so as to obtain oil-immersed paper boards with different moisture absorption degrees; testing the moisture content of the oil-immersed paper boards with different moisture degrees by using a titrator to obtain the moisture content of the oil-immersed paper boards with different moisture degrees (each oil-immersed paper board is tested for three times and the average value is taken as the moisture content of the moisture-immersed paper board);
2) and (3) carrying out frequency domain dielectric test on oil-immersed paperboards with different moisture degrees:
obtaining frequency domain dielectric spectrums of the oil-immersed paper boards with different moisture degrees; wherein the dielectric spectrum consists of a real part of the dielectric constant and an imaginary part of the dielectric constant;
3) acquiring dielectric modulus spectrums of oil-immersed paper boards with different moisture degrees:
converting the frequency domain dielectric spectrum of each oil-immersed paperboard into a dielectric modulus spectrum (the dielectric modulus spectrum consists of a dielectric modulus real part and a dielectric modulus imaginary part), combining the dielectric modulus spectrums of the oil-immersed paperboards with different wetting degrees to form discrete data points of the dielectric modulus real part and the dielectric modulus imaginary part under different test frequency points (the dielectric modulus spectrum real part and the dielectric modulus imaginary part are more sensitive to the moisture state of the oil-immersed paperboard, and the dielectric modulus imaginary part has an obvious loss peak, which indicates that the dielectric modulus spectrum can effectively represent the internal relaxation polarization process of the wetted oil-immersed paperboard);
4) extracting characteristic quantity capable of effectively representing water content of oil-immersed paperboard:
a. adopting Origin software to convert discrete data points of the real part of the dielectric modulus and the imaginary part of the dielectric modulus into mathematical functions with continuous characteristics, namely a continuous function M' (f) of the real part of the dielectric modulus and a continuous function M "(f) of the imaginary part of the dielectric modulus at different test frequency points;
b. forming a linear mathematical function G '(f) and a linear mathematical function G "(f) according to the continuous function M' (f) of the real part of the dielectric modulus and the continuous function M" (f) of the imaginary part of the dielectric modulus;
c. performing integral calculation on planes surrounded by M '(f) and M' (f) of the oil-immersed paperboard with different moisture degrees and the corresponding G '(f) and G' (f), and finally obtaining characteristic quantities RDMI and IDMI for representing the moisture degrees of the oil-immersed paperboard;
5) assessing oil impregnated paperboard moisture content
And performing nonlinear function fitting on the relation between the RDMI and the IDMI and the moisture content of the corresponding oil-immersed paperboard, and estimating the moisture content of the oil-immersed paperboard according to the fitting result (estimating the moisture content of the oil-immersed paperboard in the oil-immersed power equipment by using the fitting formula of the method).
Further, in the step 1), the manufacturing process of the oil-immersed paper boards with different moisture degrees is as follows:
weighing by using an electronic balance to obtain the initial mass of the insulating paperboard with the initial moisture content, placing the insulating paperboard in the air to absorb moisture naturally, weighing again after the expected moisture absorption time, and stopping moisture absorption after the target mass of the formula (1) is reached;
in the formula (4), m0And mTRespectively representing initial and target qualities, w, of the oil-impregnated paper sheet0And wTRespectively representing the initial and target moisture content of the oil impregnated paperboard.
Still further, in the step 2), the method for obtaining the frequency domain dielectric spectrums of the oil-impregnated paper boards with different moisture degrees comprises the following steps:
a. manufacturing a three-electrode system (the three-electrode system is manufactured according to the national standard GB/T1410-2006 and combined with the actual size of the oil-immersed paper board and is used for testing the frequency domain dielectric property of the oil-immersed paper board), placing the three-electrode testing system in a thermostat, placing the oil-immersed paper board in the three-electrode testing system in the thermostat,
b. and connecting the IDAX300 frequency domain dielectric response tester with a three-electrode test system in the thermostat, and performing frequency domain dielectric test on the oil-immersed paper boards with different degrees of moisture to obtain frequency domain dielectric spectrums (the frequency domain dielectric spectrums are composed of a dielectric constant real part and a dielectric constant imaginary part) of the oil-immersed paper boards with different degrees of moisture.
Further, the temperature in the constant temperature box is 20-85 ℃;
the working conditions of the frequency domain dielectric response tester are as follows:
the test temperature is 45 ℃, the peak value of the test voltage is 200V, and the test frequency is 2.2 multiplied by 10-3-104Hz。
Still further, in the step 3), the frequency domain dielectric spectrum is converted into a dielectric modulus spectrum based on the formula (2);
in the formula, M' (ω) is the real part of the dielectric modulus,
m "(ω) is the imaginary part of the dielectric modulus,
ε' (ω) is the real part of the dielectric constant,
ε "(ω) is the imaginary part of the dielectric constant.
Still further, in the step 4), the formulas of characteristic quantities RDMI and IDMI for characterizing the moisture degree of the oil-impregnated paperboard are obtained as follows:
in equations (3) to (4), RDMI is an integral value of the real part of the dielectric modulus,
IDMI is an imaginary integral value of the dielectric modulus,
f1and f2Respectively representing the left and right cut-off frequency points of a dielectric modulus curve;
m' (f) is a mathematical function formed by continuously processing the real part data of the dielectric modulus at different discrete frequency points;
g' (f) is a linear mathematical function formed by connecting left and right cut-off frequency points of a dielectric modulus real part curve;
m "(f) is a mathematical function formed by continuously processing the dielectric modulus imaginary part data under different discrete frequency points;
g "(f) is a linear mathematical function formed by connecting the left and right cut-off frequency points of the curve of the imaginary part of the dielectric modulus.
The invention also provides a system for evaluating the moisture content of the oil-immersed paper board in the oil-immersed power equipment, which comprises a moisture content acquisition module, a frequency domain dielectric spectrum acquisition module, a dielectric modulus integral value acquisition module and an oil-immersed paper board moisture content evaluation module; wherein,
the moisture content acquisition module is used for placing the oil-immersed paper boards in the air for natural moisture absorption to obtain the oil-immersed paper boards with different moisture degrees, and performing moisture content test on the oil-immersed paper boards with different moisture degrees to obtain the moisture contents of the oil-immersed paper boards with different moisture degrees;
the frequency domain dielectric spectrum acquisition module acquires frequency domain dielectric spectrums of the oil-immersed paper boards with different moisture degrees;
the dielectric modulus spectrum acquisition module is used for converting the frequency domain dielectric spectrum of each oil-immersed paperboard into a dielectric modulus spectrum, and combining the dielectric modulus spectrums of the oil-immersed paperboards with different moisture degrees to form discrete data points of a real part of the dielectric modulus and discrete data points of an imaginary part of the dielectric modulus at different test frequency points;
the integral value acquisition module of the dielectric modulus is used for converting discrete data points of the real part of the dielectric modulus and the imaginary part of the dielectric modulus into mathematical functions with continuous characteristics, namely a continuous function M' (f) of the real part of the dielectric modulus and a continuous function M "(f) of the imaginary part of the dielectric modulus;
forming a linear mathematical function G '(f) and a linear mathematical function G "(f) according to the continuous function M' (f) of the real part of the dielectric modulus and the continuous function M" (f) of the imaginary part of the dielectric modulus; performing integral calculation on planes surrounded by M '(f) and M' (f) of the oil-immersed paper boards with different moisture degrees and the corresponding G '(f) and G' (f) respectively to obtain a dielectric modulus real part integral value RDMI and a dielectric modulus imaginary part integral value IDMI of characteristic quantities representing the moisture degrees of the oil-immersed paper boards;
and the oil-immersed paperboard moisture content evaluation module is used for performing nonlinear function fitting on the relation between the RDMI and the IDMI and the moisture content of the corresponding oil-immersed paperboard and evaluating the moisture content of the oil-immersed paperboard according to the fitting result.
Further, the process for manufacturing the oil-immersed paper boards with different moisture degrees by the moisture content acquisition module comprises the following steps:
weighing by using an electronic balance to obtain the initial mass of the insulating paperboard with the initial moisture content, placing the insulating paperboard in the air to absorb moisture naturally, weighing again after the expected moisture absorption time, and stopping moisture absorption after the target mass of the formula (1) is reached;
in the formula (1), m0And mTRespectively representing initial and target qualities, w, of the oil-impregnated paper sheet0And wTRespectively representing the initial and target moisture content of the oil impregnated paperboard.
Still further, the method for acquiring the frequency domain dielectric spectrum of the oil-immersed paperboard with different moisture degrees by the frequency domain dielectric spectrum acquisition module comprises the following steps:
the three-electrode testing system is placed in a thermostat, the oil-immersed paper board is placed inside the three-electrode testing system in the thermostat, the frequency domain dielectric response tester is connected with the three-electrode testing system in the thermostat in a wiring mode, the oil-immersed paper boards with different moisture degrees are subjected to frequency domain dielectric testing, and the frequency domain dielectric spectrums of the oil-immersed paper boards with different moisture degrees are obtained.
Still further, the dielectric modulus spectrum obtaining module converts the frequency domain dielectric spectrum into a dielectric modulus spectrum by using a formula (2);
in the formula, M' (ω) is the real part of the dielectric modulus,
m "(ω) is the imaginary part of the dielectric modulus,
ε' (ω) is the real part of the dielectric constant,
ε "(ω) is the imaginary part of the dielectric constant.
Still further, the integral value of the dielectric modulus acquiring module obtains characteristic quantities RDMI and IDMI for representing the moisture degree of the oil-immersed paperboard by using formulas (3) to (4):
in equations (3) to (4), RDMI is an integral value of the real part of the dielectric modulus,
IDMI is an imaginary integral value of the dielectric modulus,
f1and f2Respectively are the left and right cut-off frequency points of the dielectric modulus curve;
m' (f) is a mathematical function formed by continuously processing the real part data of the dielectric modulus at different discrete frequency points;
g' (f) is a linear mathematical function formed by connecting left and right cut-off frequency points of a dielectric modulus real part curve;
m "(f) is a mathematical function formed by continuously processing the dielectric modulus imaginary part data under different discrete frequency points;
g "(f) is a linear mathematical function formed by connecting the left and right cut-off frequency points of the curve of the imaginary part of the dielectric modulus.
The invention has the beneficial effects that:
the main factor of the insulation performance failure of the oil-immersed power equipment is the moisture. The invention converts the frequency domain dielectric spectrum of the relaxation polarization process which is seriously influenced by the direct current conduction process into the dielectric modulus spectrum which can highlight the relaxation polarization process, and provides an evaluation method which can effectively represent the water content of the oil-immersed paperboard according to the characteristics of the dielectric modulus spectrum. The method can effectively represent the influence of moisture on the relaxation polarization process inside the oil-immersed paperboard system, so as to evaluate the moisture content of the oil-immersed paperboard system, and can provide a new idea for evaluating the moisture content of the oil-immersed power equipment.
Drawings
FIG. 1 is a schematic diagram of the system of the present invention;
FIG. 2 is a flow chart of an implementation of the present invention;
FIG. 3 is a diagram of a frequency domain dielectric three-electrode test system for an oil-immersed paperboard in the invention;
FIG. 4 is a frequency domain dielectric spectrogram of oil-impregnated paper sheets with different degrees of moisture exposure in the present invention;
FIG. 5 is a graph of the dielectric modulus of oil-impregnated paper sheets of different degrees of moisture exposure in accordance with the present invention;
FIG. 6 is a schematic diagram illustrating the calculation of characteristic quantities for estimating the moisture content of the oil-impregnated paper board in the present invention;
FIG. 7 is a graph showing the relationship between RDMI and moisture of different wetted oil-impregnated paper boards in the present invention;
FIG. 8 is a graph showing the relationship between IDMI and water content of different wetted oil-impregnated paper boards in the present invention;
FIG. 9 is a frequency domain dielectric spectrum of an oil-impregnated paper sheet of the present invention having a moisture content of 1.84%;
fig. 10 is a dielectric modulus spectrum of oil-impregnated paper board with a moisture content of 1.84% in the present invention.
Detailed Description
The invention is described in further detail below with reference to the following figures and specific examples:
example 1
The system for evaluating the moisture content of the oil-immersed paper board in the oil-immersed power equipment shown in fig. 1 comprises a moisture content acquisition module, a frequency domain dielectric spectrum acquisition module, a dielectric modulus integral value acquisition module and an oil-immersed paper board moisture content evaluation module; wherein,
the moisture content acquisition module is used for placing the oil-immersed paper boards in the air for natural moisture absorption to obtain the oil-immersed paper boards with different moisture degrees, and performing moisture content test on the oil-immersed paper boards with different moisture degrees to obtain the moisture contents of the oil-immersed paper boards with different moisture degrees;
the frequency domain dielectric spectrum acquisition module acquires frequency domain dielectric spectrums of the oil-immersed paper boards with different moisture degrees;
the dielectric modulus spectrum acquisition module is used for converting the frequency domain dielectric spectrum of each oil-immersed paperboard into a dielectric modulus spectrum, and combining the dielectric modulus spectra of the oil-immersed paperboards with different moisture degrees to form discrete data points of a real part of the dielectric modulus and discrete data points of an imaginary part of the dielectric modulus at different test frequency points;
the integral value acquisition module of the dielectric modulus is used for converting discrete data points of the real part of the dielectric modulus and the imaginary part of the dielectric modulus into mathematical functions with continuous characteristics, namely a continuous function M' (f) of the real part of the dielectric modulus and a continuous function M "(f) of the imaginary part of the dielectric modulus;
the continuous function M '(f) of the real part of the dielectric modulus and the continuous function M "(f) of the imaginary part of the dielectric modulus form a linear mathematical function G' (f) and a linear mathematical function G" (f); performing integral calculation on planes surrounded by M '(f) and M' (f) of the oil-immersed paper boards with different moisture degrees and the corresponding G '(f) and G' (f) respectively to obtain a dielectric modulus real part integral value RDMI and a dielectric modulus imaginary part integral value IDMI of characteristic quantities representing the moisture degrees of the oil-immersed paper boards;
and the oil-immersed paperboard moisture content evaluation module is used for performing nonlinear function fitting on the relation between the RDMI and the IDMI and the moisture content of the corresponding oil-immersed paperboard and evaluating the moisture content of the oil-immersed paperboard according to the fitting result.
Example 2
The method for evaluating the moisture content of the oil-immersed paperboard in the oil-immersed power equipment based on the device shown in FIG. 2 comprises the following steps:
1) preparing oil-immersed paper boards with different moisture degrees (the moisture content is 0.5% -5%):
a. putting the 4 dry oil-immersed paper boards in the air according to different days for natural moisture absorption (the moisture absorption degree is determined by controlling the natural moisture absorption time), and obtaining oil-immersed paper boards with different moisture degrees; the manufacturing process of the oil-immersed paperboard with different moisture degrees comprises the following steps:
selecting a dry oil-immersed paperboard, weighing by adopting an electronic balance to obtain the initial mass of the insulating paperboard with the initial moisture content, placing the insulating paperboard in the air to absorb moisture naturally, weighing the oil-immersed paperboard placed in the air with different moisture absorption time, weighing again after the expected moisture absorption time, and stopping moisture absorption after the target mass of the formula (1) is reached;
in the formula (4), m0And mTRespectively representing initial and target qualities, w, of the oil-impregnated paper sheet0And wTRespectively representing the initial and target moisture contents of the oil-impregnated paper board;
b. when the moisture content of the oil-impregnated paper board meets the expected requirement, a water content test is carried out on a damp sample by adopting a Mettler-Torlado DO308 and DL32 Karlifen coulometric titrator, each oil-impregnated paper board is tested for three times, the average value is taken as the sample moisture content, and finally the water content of the oil-impregnated paper board is respectively 0.98%, 2.53%, 3.62% and 4.51%;
2) and (3) carrying out frequency domain dielectric test on oil-immersed paperboards with different moisture degrees:
manufacturing a three-electrode system (manufacturing the three-electrode system according to the national standard GB/T1410-2006 and by combining the actual size of the oil-immersed paperboardA three-electrode system is used for testing the frequency domain dielectric property of the oil-immersed paperboard), as shown in fig. 3, the three-electrode testing system is placed in a thermostat with the temperature of 20-85 ℃, the oil-immersed paperboard is placed in the three-electrode testing system in the thermostat, then an IDAX300 frequency domain dielectric response tester is adopted to be connected with the three-electrode testing system in the thermostat in a wiring mode, and different damp samples are subjected to frequency domain dielectric testing (the testing temperature is controlled to be 45 ℃, the voltage peak value of the frequency domain dielectric property testing is 200V, and the testing frequency range is 2.2 x 10)-3-104Hz); the real and imaginary parts of the relative dielectric constants of the different wetted oil-impregnated paperboard samples obtained are shown in fig. 4.
3) Acquiring dielectric modulus spectrums of oil-immersed paper boards with different moisture degrees:
the frequency domain dielectric spectrum of each oil-impregnated paperboard is converted into a dielectric modulus spectrum (the dielectric modulus spectrum is composed of a real part of dielectric modulus and an imaginary part of dielectric modulus) according to a dielectric modulus spectrum conversion formula (2), as shown in fig. 5. As can be seen from FIG. 5, the real part and the imaginary part of the dielectric modulus spectrum are sensitive to the moisture-affected reaction of the oil-immersed paperboard, and the imaginary part of the dielectric modulus spectrum has an obvious loss peak;
in the formula, M' (ω) is the real part of the dielectric modulus,
m "(ω) is the imaginary part of the dielectric modulus,
ε' (ω) is the real part of the dielectric constant,
ε "(ω) is the imaginary part of the dielectric constant;
4) extracting characteristic quantity capable of effectively representing water content of oil-immersed paperboard:
a. firstly, adopting Origin software to convert discrete data points of the real part and the imaginary part of the dielectric modulus at different test frequency points into mathematical functions with continuous characteristics, namely a continuous function M' (f) of the real part of the dielectric modulus and a continuous function M "(f) of the imaginary part of the dielectric modulus;
b. furthermore, the left and right boundary points of the functions M '(f) and M "(f) are connected to form corresponding linear functions, namely G' (f) and G" (f);
c. performing integral calculation on planes enclosed by the M '(f) and the M' (f) of the oil-immersed paperboard with different moisture degrees and the corresponding G '(f) and G' (f) by adopting a formula (3) and a formula (4), and finally obtaining characteristic quantities RDMI and IDMI (shown in table 1) representing the moisture degrees of the oil-immersed paperboard;
in equations (3) to (4), RDMI is an integral value of the real part of the dielectric modulus,
IDMI is an imaginary integral value of the dielectric modulus,
f1and f2Respectively representing the left and right cut-off frequency points of a dielectric modulus curve;
m' (f) represents a mathematical function formed by continuously processing the real part data of the dielectric modulus at different discrete frequency points;
g' (f) represents a linear mathematical function formed by connecting left and right cut-off frequency points of a real part curve of the dielectric modulus;
m "(f) represents a mathematical function formed by continuous processing of dielectric modulus imaginary part data under different discrete frequency points;
g "(f) represents a linear mathematical function formed by connecting left and right cut-off frequency points of the curve of the imaginary part of the dielectric modulus;
TABLE 1
5) Determining evaluation formula for evaluating moisture content of oil-impregnated paperboard by different characteristic quantities
And performing nonlinear function fitting on the relationship between the real part integral value RDMI of the dielectric modulus, the imaginary part integral value IDMI of the dielectric modulus and the moisture content as shown in figures 6-8, and determining an evaluation formula for evaluating the moisture content of the oil-impregnated paperboard by different characteristic quantities as shown in formula (5) and formula (6). From the formula (5) and the formula (6), the real part integral value RDMI and the imaginary part integral value IDMI of the dielectric modulus have a good exponential function relationship (the goodness of fit is more than 0.99) with the moisture content as follows:
RDMI＝-1706.3×e(-mc％/2.43)+1667.44 (5)
IDMI＝333.16/(1+e((mc％-2.51)/0.45))+17.40 (6)
example 3
The method is used for evaluating the moisture of the oil-immersed paperboard in the existing oil-immersed power equipment:
and (3) testing the moisture content of the verified oil-immersed paperboard by using a Karl Fischer titrator to obtain the moisture content of 1.84%. Then, an frequency domain dielectric response tester of IDAX300 is used to perform a frequency domain dielectric test on the oil-impregnated paperboard, and the real part and the imaginary part of the dielectric constant are obtained as shown in fig. 9. Then, the dielectric constants of the real part and the imaginary part obtained by the test are converted into the dielectric modulus real part and the dielectric modulus imaginary part by using the formula (1), as shown in fig. 10. Secondly, the dielectric modulus real part and the dielectric modulus imaginary part of the oil-impregnated paperboard sample are subjected to quantitative integral calculation by using the formula (2) and the formula (3), and the RDMI and IDMI characteristic quantity values are obtained through calculation and are 851 and 186 respectively. Meanwhile, the calculated RDMI and IDMI values are respectively substituted into a fitting formula (5) and a fitting formula (6), so that the pre-evaluation moisture content values are respectively 1.79% and 1.89%. Finally, the relative error calculated for the estimated moisture content using equation (7) was 2.7% compared to the measured moisture content of 1.84%.
RE in the formula (7) is the relative error of the moisture content evaluation result, mc%Evaluation ofFor the estimated moisture content, mc%Measured in factMeasured moisture content.
From the above, it can be seen that: the method has small error in estimating the moisture content of the oil-impregnated paper board, and can be used for effectively estimating the moisture content of the oil-impregnated paper board.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.
Claims (10)
1. A method for evaluating the moisture content of an oil-immersed paperboard in an oil-immersed power device is characterized by comprising the following steps of: the method comprises the following steps:
1) placing a plurality of oil-immersed paper boards in air for natural moisture absorption to obtain oil-immersed paper boards with different moisture degrees; testing the moisture content of the oil-immersed paper boards with different moisture degrees to obtain the moisture content of the oil-immersed paper boards with different moisture degrees;
2) obtaining frequency domain dielectric spectrums of the oil-immersed paper boards with different moisture degrees; wherein the dielectric spectrum consists of a real part of the dielectric constant and an imaginary part of the dielectric constant;
3) converting the frequency domain dielectric spectrum of each oil-immersed paperboard into a dielectric modulus spectrum, and combining the dielectric modulus spectrums of the oil-immersed paperboards with different moisture degrees to form discrete data points of a real part of the dielectric modulus and data points of an imaginary part of the dielectric modulus at different test frequency points;
4) converting the discrete data points of the real part of the dielectric modulus and the imaginary part of the dielectric modulus into mathematical functions with continuous characteristics, namely a continuous function M' (f) of the real part of the dielectric modulus and a continuous function M "(f) of the imaginary part of the dielectric modulus;
forming a linear mathematical function G '(f) and a linear mathematical function G "(f) according to the continuous function M' (f) of the real part of the dielectric modulus and the continuous function M" (f) of the imaginary part of the dielectric modulus;
performing integral calculation on planes surrounded by M '(f) and M' (f) of the oil-immersed paper boards with different moisture degrees and the corresponding G '(f) and G' (f) respectively to obtain a dielectric modulus real part integral value RDMI and a dielectric modulus imaginary part integral value IDMI of characteristic quantities representing the moisture degrees of the oil-immersed paper boards;
5) and performing nonlinear function fitting on the relation between the RDMI and the IDMI and the moisture content of the corresponding oil-immersed paperboard, and evaluating the moisture content of the oil-immersed paperboard according to the fitting result.
2. The method for evaluating the moisture content of the oil-immersed paper board in the oil-immersed power equipment according to claim 1, wherein in the step 1), the oil-immersed paper boards with different moisture degrees are manufactured by the following processes:
weighing by using an electronic balance to obtain the initial mass of the insulating paperboard with the initial moisture content, placing the insulating paperboard in the air to absorb moisture naturally, weighing again after the expected moisture absorption time, and stopping moisture absorption after the target mass of the formula (1) is reached;
in the formula (1), m0And mTRespectively representing initial and target qualities, w, of the oil-impregnated paper sheet0And wTRespectively representing the initial and target moisture content of the oil impregnated paperboard.
3. The method for estimating the moisture content of an oil-impregnated paperboard in an oil-filled power device according to claim 1, wherein: in the step 2), the method for obtaining the frequency domain dielectric spectrums of the oil-immersed paper boards with different moisture degrees comprises the following steps:
the three-electrode testing system is placed in a thermostat, the oil-immersed paper board is placed inside the three-electrode testing system in the thermostat, the frequency domain dielectric response tester is connected with the three-electrode testing system in the thermostat in a wiring mode, the oil-immersed paper boards with different moisture degrees are subjected to frequency domain dielectric testing, and the frequency domain dielectric spectrums of the oil-immersed paper boards with different moisture degrees are obtained.
4. The method for estimating the moisture content of an oil-impregnated paperboard in an oil-filled power device according to claim 1, wherein: the step 3) of converting the frequency domain dielectric spectrum into a dielectric modulus spectrum based on the formula (2);
in the formula, M' (ω) is the real part of the dielectric modulus,
m "(ω) is the imaginary part of the dielectric modulus,
ε' (ω) is the real part of the dielectric constant,
ε "(ω) is the imaginary part of the dielectric constant.
5. The method for estimating the moisture content of an oil-impregnated paperboard in an oil-filled power device according to claim 1, wherein: in the step 4), the formulas of characteristic quantities RDMI and IDMI for representing the moisture degree of the oil-immersed paperboard are obtained as follows:
in equations (3) to (4), RDMI is an integral value of the real part of the dielectric modulus,
IDMI is an imaginary integral value of the dielectric modulus,
f1and f2Respectively are the left and right cut-off frequency points of the dielectric modulus curve;
m' (f) is a mathematical function formed by continuously processing the real part data of the dielectric modulus at different discrete frequency points;
g' (f) is a linear mathematical function formed by connecting left and right cut-off frequency points of a dielectric modulus real part curve;
m "(f) is a mathematical function formed by continuously processing the dielectric modulus imaginary part data under different discrete frequency points;
g "(f) is a linear mathematical function formed by connecting the left and right cut-off frequency points of the curve of the imaginary part of the dielectric modulus.
6. A system for evaluating the moisture content of an oil-immersed paperboard in oil-immersed power equipment is characterized by comprising a moisture content acquisition module, a frequency domain dielectric spectrum acquisition module, a dielectric modulus integral value acquisition module and an oil-immersed paperboard moisture content evaluation module; wherein,
the moisture content acquisition module is used for placing the oil-immersed paper boards in the air for natural moisture absorption to obtain the oil-immersed paper boards with different moisture degrees, and performing moisture content test on the oil-immersed paper boards with different moisture degrees to obtain the moisture contents of the oil-immersed paper boards with different moisture degrees;
the frequency domain dielectric spectrum acquisition module acquires frequency domain dielectric spectrums of the oil-immersed paper boards with different moisture degrees;
the dielectric modulus spectrum acquisition module is used for converting the frequency domain dielectric spectrum of each oil-immersed paperboard into a dielectric modulus spectrum, and combining the dielectric modulus spectrums of the oil-immersed paperboards with different moisture degrees to form discrete data points of a real part of the dielectric modulus and discrete data points of an imaginary part of the dielectric modulus at different test frequency points;
the integral value acquisition module of the dielectric modulus is used for converting discrete data points of the real part of the dielectric modulus and the imaginary part of the dielectric modulus into mathematical functions with continuous characteristics, namely a continuous function M' (f) of the real part of the dielectric modulus and a continuous function M "(f) of the imaginary part of the dielectric modulus;
forming a linear mathematical function G '(f) and a linear mathematical function G "(f) according to the continuous function M' (f) of the real part of the dielectric modulus and the continuous function M" (f) of the imaginary part of the dielectric modulus;
performing integral calculation on planes surrounded by M '(f) and M' (f) of the oil-immersed paper boards with different moisture degrees and the corresponding G '(f) and G' (f) respectively to obtain a dielectric modulus real part integral value RDMI and a dielectric modulus imaginary part integral value IDMI of characteristic quantities representing the moisture degrees of the oil-immersed paper boards;
and the oil-immersed paperboard moisture content evaluation module is used for performing nonlinear function fitting on the relation between the RDMI and the IDMI and the moisture content of the corresponding oil-immersed paperboard and evaluating the moisture content of the oil-immersed paperboard according to the fitting result.
7. The system for evaluating the moisture content of the oil-immersed paper board in the oil-immersed power equipment according to claim 6, wherein the process for manufacturing the oil-immersed paper boards with different moisture degrees by the moisture content acquisition module is as follows:
weighing by using an electronic balance to obtain the initial mass of the insulating paperboard with the initial moisture content, placing the insulating paperboard in the air to absorb moisture naturally, weighing again after the expected moisture absorption time, and stopping moisture absorption after the target mass of the formula (1) is reached;
in the formula (1), m0And mTRespectively representing initial and target qualities, w, of the oil-impregnated paper sheet0And wTRespectively representing the initial and target moisture content of the oil impregnated paperboard.
8. The system for estimating the moisture content of the oil-impregnated paper board in the oil-filled power device according to claim 6, wherein the frequency-domain dielectric spectrum obtaining module obtains the frequency-domain dielectric spectra of the oil-impregnated paper boards with different degrees of moisture as follows:
the three-electrode testing system is placed in a thermostat, the oil-immersed paper board is placed inside the three-electrode testing system in the thermostat, the frequency domain dielectric response tester is connected with the three-electrode testing system in the thermostat in a wiring mode, the oil-immersed paper boards with different moisture degrees are subjected to frequency domain dielectric testing, and the frequency domain dielectric spectrums of the oil-immersed paper boards with different moisture degrees are obtained.
9. The system for estimating moisture content of an oil-immersed paperboard in an oil-filled power device according to claim 6, wherein the dielectric modulus spectrum obtaining module converts the frequency domain dielectric spectrum into a dielectric modulus spectrum by using formula (2);
in the formula, M' (ω) is the real part of the dielectric modulus,
m "(ω) is the imaginary part of the dielectric modulus,
ε' (ω) is the real part of the dielectric constant,
ε "(ω) is the imaginary part of the dielectric constant.
10. The system for evaluating the moisture content of the oil-immersed paperboard in the oil-immersed power equipment according to claim 6, wherein the integral value acquisition module of the dielectric modulus obtains characteristic quantities RDMI and IDMI which represent the moisture degree of the oil-immersed paperboard by using formulas (3) to (4):
in equations (3) to (4), RDMI is an integral value of the real part of the dielectric modulus,
IDMI is an imaginary integral value of the dielectric modulus,
f1and f2Respectively are the left and right cut-off frequency points of the dielectric modulus curve;
m' (f) is a mathematical function formed by continuously processing the real part data of the dielectric modulus at different discrete frequency points;
g' (f) is a linear mathematical function formed by connecting left and right cut-off frequency points of a dielectric modulus real part curve;
m "(f) is a mathematical function formed by continuously processing the dielectric modulus imaginary part data under different discrete frequency points;
g "(f) is a linear mathematical function formed by connecting the left and right cut-off frequency points of the curve of the imaginary part of the dielectric modulus.
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Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106021756A (en) * | 2016-05-27 | 2016-10-12 | 三峡大学 | Method for assessing insulation state of oil paper based on characteristic quantity of frequency domain dielectric spectroscopy |
| CN107894444A (en) * | 2017-11-10 | 2018-04-10 | 哈尔滨理工大学 | A kind of Oil-Paper Insulation moisture content fitting algorithm |
| CN108680613A (en) * | 2018-04-23 | 2018-10-19 | 三峡大学 | A method of assessing moisture in insulating paper using complex dielectric permittivity initial slope |
| US20190041450A1 (en) * | 2015-12-01 | 2019-02-07 | Yandong LV | An intelligent assessment method of main insulation condition of transformer oil paper insulation |
| CN110009236A (en) * | 2019-04-10 | 2019-07-12 | 哈尔滨理工大学 | A kind of oil-immersed power transformer built-in electrical insulation degree of aging quantitative evaluating method |
| CN111220885A (en) * | 2020-01-21 | 2020-06-02 | 广西大学 | Method for estimating activation energy of transformer oil paper insulation based on frequency domain dielectric modulus |
| CN111812467A (en) * | 2020-07-16 | 2020-10-23 | 重庆大学 | Method for evaluating aging state of oil-impregnated transformer oil paper insulation system |
-
2021
- 2021-01-06 CN CN202110011953.8A patent/CN112798663B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20190041450A1 (en) * | 2015-12-01 | 2019-02-07 | Yandong LV | An intelligent assessment method of main insulation condition of transformer oil paper insulation |
| CN106021756A (en) * | 2016-05-27 | 2016-10-12 | 三峡大学 | Method for assessing insulation state of oil paper based on characteristic quantity of frequency domain dielectric spectroscopy |
| CN107894444A (en) * | 2017-11-10 | 2018-04-10 | 哈尔滨理工大学 | A kind of Oil-Paper Insulation moisture content fitting algorithm |
| CN108680613A (en) * | 2018-04-23 | 2018-10-19 | 三峡大学 | A method of assessing moisture in insulating paper using complex dielectric permittivity initial slope |
| CN110009236A (en) * | 2019-04-10 | 2019-07-12 | 哈尔滨理工大学 | A kind of oil-immersed power transformer built-in electrical insulation degree of aging quantitative evaluating method |
| CN111220885A (en) * | 2020-01-21 | 2020-06-02 | 广西大学 | Method for estimating activation energy of transformer oil paper insulation based on frequency domain dielectric modulus |
| CN111812467A (en) * | 2020-07-16 | 2020-10-23 | 重庆大学 | Method for evaluating aging state of oil-impregnated transformer oil paper insulation system |
Non-Patent Citations (3)
| Title |
|---|
| 刘骥;张明泽;赵春明;程炜超;贾海峰;朱博;: "基于频域介电响应分频段优化计算的变压器油纸绝缘老化参数定量计算方法", 电工技术学报, no. 09 * |
| 董明;刘媛;任明;吴雪舟;汪可;刘锐;李金忠;: "油纸绝缘频域介电谱特征参数提取及绝缘状态相关性研究", 中国电机工程学报, no. 23 * |
| 黎成林;曹保江;孙健翔;雷帆;吴广宁;高波;: "基于FDS的变压器油浸纸老化程度与水分含量评估方法", 电力自动化设备, no. 01 * |
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