CN107957436A - Method for evaluating uneven moisture degree of oil-impregnated paper insulation assembly - Google Patents

Abstract

The present invention provides a method for evaluating the degree of uneven dampness of an oil-impregnated paper insulation assembly, comprising: step S1, forming a plurality of oil-impregnated paper samples with uneven dampness through a plurality of uniformly dampened oil-impregnated paper insulation samples, and evaluating each The oil-impregnated paper sample is subjected to a frequency-domain dielectric spectrum test to obtain a plurality of first dielectric spectrum curves, and the corresponding relationship between each first dielectric spectrum curve and the degree of moisture of each oil-impregnated paper sample is established; step S2 , performing a frequency-domain dielectric spectrum test on the actual oil-impregnated paper insulation assembly to obtain a second dielectric spectrum curve, when the similarity between the second dielectric spectrum curve and one of the first dielectric spectrum curves meets a predetermined requirement , the degree of dampness corresponding to the corresponding first dielectric spectrum curve is taken as the degree of dampness of the actual oil-immersed insulation component. The invention has the advantages that: the characteristic peak of the frequency domain dielectric spectrum is used to evaluate the non-uniform dampness degree of the oil-paper insulation, and compared with the existing method, the evaluation accuracy of the dampness of the oil-paper insulation is improved, and more detailed dampness conditions can be obtained.

Description

A Method for Evaluating the Degree of Uneven Wetting of Oil-impregnated Paper Insulation Assemblies

technical field

The invention relates to the technical field of power transmission detection, in particular to a method for evaluating the degree of uneven dampness of an oil-immersed paper insulation assembly.

Background technique

Oil-impregnated paper insulation is one of the most commonly used insulating materials for power equipment. It is mainly used in the insulation system of oil-immersed transformers, oil-impregnated paper bushings and oil-immersed capacitors. In the power grid system of 110kV and above, the proportion of oil-impregnated paper insulation reaches more than 93%. Among them, the capacitive high-voltage bushing is one of the typical oil-impregnated paper insulation devices, and it is an indispensable external connection component of the power transformer. It not only has the function of leading the winding leads out of the transformer, but also bears the role of supporting and fixing the leads. The data show that the bushing accidents of 110kV and above transformers account for a certain proportion of the total number of accidents, and as the voltage level increases, the proportion of accidents caused by bushings increases. The failure or damage of the transformer bushing will not only cause a power outage of the transformer, but also may cause the explosion of the bushing, damage the transformer or even cause a fire to further expand the scope of the accident. For the oil-impregnated paper insulating bushing, the moisture content has a significant acceleration effect on the aging of the insulating paper. The higher the moisture content, the faster the aging rate, and the decreasing rate of the degree of polymerization of the insulating paper is also significantly accelerated. Therefore, the safe and stable operation of the bushing directly affects the stability of the entire power grid, and the diagnosis and evaluation of its insulation state and damp model are of great significance.

At present, there are dry weighing method, Karl-Fisher method, oil-immersed paper moisture balance curve method, etc. to detect the moisture content in insulating paper. The first two measurements must take samples to damage the insulation of the equipment, and the weighing method has been replaced by the Karl-Fischer method because of its low measurement accuracy. The oil-soaked paper moisture balance curve method first measures the moisture content in the oil, and then estimates the water content in the paper according to the oil-soaked paper moisture balance curve. This method is easy to operate and will not damage the insulation of the equipment, but the measurement accuracy is low.

In the existing method of evaluating the moisture content of oil-impregnated paper insulation by using FDS (Frequency Domain Dielectric Spectroscopy), the moisture content is usually regarded as the equivalent moisture content, and the moisture distribution is assumed to be uniform.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for evaluating the degree of uneven dampness of oil-impregnated paper insulation components, which utilizes the characteristic peaks of the dielectric spectrum in the frequency domain to evaluate the degree of uneven dampness of oil-paper insulation. The accuracy of moisture assessment of oil-paper insulation is improved, and more detailed moisture conditions can be obtained.

In order to solve the above technical problems, the present invention provides a method for evaluating the degree of uneven damping of oil-impregnated paper insulation components, including:

Step S1, combining multiple uniformly damp oil-impregnated paper insulation samples in different ways to form multiple unevenly damp oil-impregnated paper samples, and performing a frequency-domain dielectric spectrum test on each unevenly damp oil-impregnated paper sample, Obtaining a plurality of first dielectric spectrum curves, and establishing a corresponding relationship between each of the first dielectric spectrum curves and the degree of dampness of each non-uniform oil-impregnated paper sample;

Step S2, performing a frequency-domain dielectric spectrum test on the actual oil-impregnated paper insulation assembly to obtain a second dielectric spectrum curve, when the similarity between the second dielectric spectrum curve and one of the first dielectric spectrum curves reaches When a predetermined requirement is required, the degree of dampness corresponding to the corresponding first dielectric spectrum curve is used as the degree of dampness of the actual oil-immersed insulation component.

Before the step S1, it also includes: step S0, making a plurality of uniformly damp oil-impregnated paper insulation samples with different moisture levels, and performing a frequency-domain dielectric spectrum test on each uniformly damp oil-impregnated paper insulation sample to obtain multiple A third dielectric spectrum curve.

After the step S1, it also includes: obtaining the impedance equivalent value of the dielectric spectrum curve of each uniformly dampened oil-soaked paper insulation sample in each superposition combination; calculate the dielectric loss curve of each superimposed combination; and verify the accuracy of the first dielectric spectrum curve obtained in step S1 through the calculated dielectric curve.

Among them, different uniformly damp oil-impregnated paper insulation samples have different damp levels.

Wherein, the oil-immersed paper insulation assembly is used in equipment such as oil-immersed transformers, oil-paper bushings, and oil-immersed capacitors.

Wherein, the frequency-domain dielectric spectrum test in step S1 and step S2 is carried out at 40 degrees and the input voltage is 200V.

Wherein, the thickness of the non-uniformly damped oil-soaked paper sample combined with a plurality of uniformly dampened oil-soaked paper insulation samples is the same as the thickness of a single uniformly damped oil-soaked paper sample.

The beneficial effects of the embodiments of the present invention are:

The embodiment of the present invention evaluates the degree of uneven dampness of oil-impregnated paper insulation samples, on the one hand, improves the accuracy of oil-paper insulation dampness assessment, and can obtain more detailed dampness conditions; on the one hand, compared with the dry weighing method, The present invention can significantly improve the accuracy of the test, and can obtain specific moisture distribution conditions; on the other hand, compared with the Karl-Fisher method, the present invention can realize non-destructive testing, without damage to samples or oil-paper insulated power equipment, and the testing process Convenient and fast.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is a schematic flow chart of an embodiment of a method for evaluating the degree of uneven damping of an oil-impregnated paper insulation assembly.

Fig. 2 is a schematic flowchart of another embodiment of a method for evaluating the degree of uneven damping of an oil-impregnated paper insulation assembly.

Fig. 3 is a schematic diagram of another embodiment of tanδ-f curves under different water contents in the present invention.

Fig. 4 is a schematic diagram of another embodiment of C'-f curves under different water contents in the present invention.

Fig. 5 is a schematic diagram of another embodiment of C"-f curves under different water contents in the present invention.

Figure 6 is a schematic diagram of another embodiment of the tanδ-f characteristic curve with an equivalent water content of 2% in the present invention.

Figure 7 is a schematic diagram of another embodiment of the tanδ-f characteristic curve with an equivalent water content of 3% in the present invention.

Figure 8 is a schematic diagram of another embodiment of the tanδ-f characteristic curve with an equivalent water content of 4% in the present invention.

Fig. 9 is a schematic diagram of another embodiment of the double-layer oil-paper insulation equivalent circuit diagram in the present invention.

Detailed ways

Embodiments of the present invention will be illustrated below with reference to the accompanying drawings.

Fig. 1 is a schematic flow chart of an embodiment of a method for evaluating the degree of uneven damping of an oil-impregnated paper insulation assembly according to the present invention. The applicable object of the invention is the insulation system of equipment such as oil-immersed transformer, oil-paper bushing and oil-immersed capacitor.

Step S1, combining the plurality of uniformly damp oil-soaked paper insulation samples in different ways to form a plurality of non-uniformly damp oil-soaked paper samples, and performing frequency-domain dielectric spectroscopy on each non-uniformly damp oil-soaked paper sample Test to obtain a plurality of first dielectric spectrum curves, and establish a corresponding relationship between each of the first dielectric spectrum curves and the moisture content of each non-uniform oil-impregnated paper sample.

Step S2, performing a frequency-domain dielectric spectrum test on the actual oil-impregnated paper insulation assembly to obtain a second dielectric spectrum curve, when the similarity between the second dielectric spectrum curve and one of the first dielectric spectrum curves reaches When a predetermined requirement is required, the degree of dampness corresponding to the corresponding first dielectric spectrum curve is used as the degree of dampness of the actual oil-immersed insulation component.

Fig. 2 is a schematic flow chart of another embodiment of a method for evaluating the degree of uneven damping of an oil-impregnated paper insulation assembly according to the present invention, the method may include:

Step S0, making a plurality of uniformly damp oil-impregnated paper insulation samples with different moisture levels, and performing a frequency-domain dielectric spectrum test on each uniformly damp oil-impregnated paper insulation sample to obtain a plurality of uniformly damp oil-impregnated paper insulation samples The dielectric spectrum curve.

Step S1, combining the plurality of uniformly damp oil-soaked paper insulation samples in different ways to form a plurality of non-uniformly damp oil-soaked paper samples, and performing frequency-domain dielectric spectroscopy on each non-uniformly damp oil-soaked paper sample Test to obtain a plurality of first dielectric spectrum curves, and establish a corresponding relationship between each of the first dielectric spectrum curves and the degree of dampness of each non-uniform oil-impregnated paper sample;

Step S11, obtaining the impedance equivalent value of the dielectric spectrum curve of each uniformly damp oil-impregnated paper insulation sample in each superposition combination, and calculating according to the obtained impedance equivalent value of each uniformly damp oil-impregnated paper insulation sample Each superimposed and combined dielectric loss curve is used to verify the accuracy of the first dielectric spectrum curve obtained in step S1 through the calculated dielectric curve.

Step S2, performing a frequency-domain dielectric spectrum test on the actual oil-impregnated paper insulation assembly to obtain a second dielectric spectrum curve, when the similarity between the second dielectric spectrum curve and one of the first dielectric spectrum curves reaches When a predetermined requirement is required, the degree of dampness corresponding to the corresponding first dielectric spectrum curve is used as the degree of dampness of the actual oil-immersed insulation component.

The method for evaluating the degree of moisture of the oil-impregnated paper insulation assembly of the present invention will be described in detail below in conjunction with a specific example.

In step S0, uniformly damp oil-paper unit laminated samples with initial moisture content of: dry, 1%, 2%, 3%, 4%, 5%, and 6% can be prepared. Among them, the water content of 6% is obtained by artificial humidification, and the equipment in operation is usually not affected by so much damp. The purpose is to observe whether the water change law when the water content is high is consistent with that when the water content is low. Evaluation curves provide more data points to improve fit accuracy. Obtain unit laminated oil-impregnated paper samples with different water contents (<0.5%, 1%, 2%, 3%, 4%, 5% and 6%), and conduct frequency-domain dielectric spectrum testing, with a frequency range of 1mHz~ 5kHz, the test temperature is 40°C, and the peak test voltage is 200V. The obtained dielectric spectrum curves are shown in Fig. 3 , Fig. 4 and Fig. 5 .

In step S1, use the above uniform damp samples to combine into non-uniform damp oil-paper insulation samples, and perform frequency-domain dielectric spectrum testing to obtain dielectric spectrum curves corresponding to different unevenness. As an example, the cable paper unit stacks can be reassembled into unit stacks with an equivalent moisture content of 2%, 3%, and 4% and the thickness of the unit stacks before assembly can be maintained. The specific combinations are shown in Table 1. The uneven degree of dampness n is defined as the degree of deviation between the local water content and the equivalent water content. The larger the value of n, the more uneven the dampness, as shown in the following formula

(1)

Table 1 Equivalent moisture content of unit laminated oil-impregnated paper samples

The frequency-domain dielectric spectrum test (test voltage 200V) was carried out on the above three types of non-uniform damp test samples at 40°C, and the test results are shown in Figure 6, Figure 7 and Figure 8 respectively.

In step S11, the frequency-domain dielectric spectrum of the uniform water content in step S0 is used to replace the frequency-domain dielectric spectrum of the uniform part of the non-uniform damp test sample in step S1. Since the thickness is doubled, the capacitance needs to be doubled during calculation. According to the calculation of the equivalent polarization and loss parameters of the composite medium, a double-layer series model is used to compare the test results. The impedance Z obtained from the dielectric response test of the frequency-domain dielectric spectrum of uniform water content can be expressed by the parallel equivalent circuit of R and C, as follows

(2)

According to the equivalent circuit model in Figure 9, substituting the RC equivalent circuit parameters with different water contents of the single layer into the formula (3) can obtain the interface polarization loss tanδ-f curve caused by inhomogeneity in the combination of double-layer oil-paper insulation.

(3)

(4)

(5)

Comparing the calculated tanδ-f curve with the frequency-domain dielectric spectrum curve measured by the non-uniform damp oil paper sample, when the curve coincidence degree is the highest, it can be obtained by checking the corresponding table of water content and damp degree similar to Table 1. The non-uniform moisture content of the oil-paper insulation sample.

Finally, in step S2, the degree of dampness of the actual oil-impregnated paper insulation assembly can be judged according to the similarity between the dielectric spectrum curve obtained from the actual oil-impregnated paper insulation assembly and the dielectric spectrum curve of the non-uniform damp sample.

To sum up, the embodiment of the present invention uses a method for evaluating the uneven moisture content of oil-impregnated paper insulation components. On the one hand, the accuracy of moisture assessment of oil-paper insulation is improved, and more detailed moisture conditions can be obtained; On the one hand, compared with the dry weighing method, the present invention can significantly improve the accuracy of the test, and can obtain specific moisture distribution conditions; Oil-paper insulated power equipment is non-destructive and the test process is convenient and fast.

The above disclosures are only preferred embodiments of the present invention, and certainly cannot limit the scope of rights of the present invention. Therefore, equivalent changes made according to the claims of the present invention still fall within the scope of the present invention.

Claims (7)

1. A kind of 1. method for the uneven damp degree for assessing oil-impregnated paper insulation component, it is characterised in that including：

   Step S1, multiple oil-impregnated paper insulation samples uniformly to make moist are combined by different way, form multiple uneven oil that make moist Impregnated paper sample, and dielectric spectroscopy test is carried out to each non-uniform oil-paper sample that makes moist, obtain multiple first dielectric spectras Curve, and it is corresponding with the damp degree for the non-uniform oil-paper sample that each makes moist to establish each first dielectric spectral curve Relation；

   Step S2, carries out dielectric spectroscopy test to actual oil-impregnated paper insulation component, obtains the second dielectric spectral curve, when described the When the similarity of one of two dielectric spectral curves and the first dielectric spectral curve reaches pre-provisioning request, by corresponding first dielectric spectra Damp degree of the corresponding damp degree of curve as the actual oil immersion insulation assembly.
2. 2. according to the method described in claim 1, it is characterized in that, further included before the step S1：

   Step S0, make the different multiple oil-impregnated paper insulation samples uniformly to make moist of damp degree, and uniformly makes moist to each Oil-impregnated paper insulation sample carries out dielectric spectroscopy test, obtains multiple 3rd dielectric spectral curves.
3. 3. according to the method described in claim 2, it is characterized in that, further included after the step S1：

   The equivalent impedance of the dielectric spectral curve for the oil-impregnated paper insulation sample that each obtained in each stack combinations is uniformly made moist Value；

   Each stack combinations is calculated according to acquisition each equivalent impedance value of oil-impregnated paper insulation sample for uniformly making moist Dielectric loss curve；

   And the accuracy of the first dielectric spectral curve obtained in the dielectric curve verification step S1 for passing through the calculating.
4. 4. according to the method described in claim 1, it is characterized in that, the different oil-impregnated paper insulation samples uniformly to make moist makes moist Degree is different.
5. 5. according to the method described in claim 1, it is characterized in that, the oil-impregnated paper insulation component be used for oil-immersed transformer, In the equipment such as oilpaper casing and oil immersed type capacitor.
6. 6. according to the method any one of claim 1-5, it is characterised in that into line frequency in the step S1 and step S2 Domain dielectric spectra test is that input voltage carries out in the case of being 200V at 40 degree.
7. 7. according to the method any one of claim 1-5, it is characterised in that：

   The thickness of the uneven oil-paper sample that makes moist after multiple oil-impregnated paper insulation sample combinations uniformly made moist with it is single uniformly The thickness of the oil-paper sample to make moist is identical.