CN107957436B - Method for evaluating uneven moisture degree of oil-impregnated paper insulation assembly - Google Patents
Method for evaluating uneven moisture degree of oil-impregnated paper insulation assembly Download PDFInfo
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Abstract
本发明提供一种评估油浸纸绝缘组件的不均匀受潮程度的方法，包括：步骤S1，通过多个均匀受潮的油浸纸绝缘样品形成多个受潮不均匀油浸纸样品，并对每个油浸纸样品进行频域介电谱测试，得到多个第一介电谱曲线，并建立所述每个第一介电谱曲线与每个油浸纸样品的受潮程度的对应关系；步骤S2，对实际油浸纸绝缘组件进行频域介电谱测试，得到第二介电谱曲线，当所述第二介电谱曲线与所述第一介电谱曲线之一的相似度达到预定要求时，将对应的第一介电谱曲线对应的受潮程度作为所述实际油浸绝缘组件的受潮程度。本发明优点在于：利用频域介电谱特征峰来评估油纸绝缘不均匀受潮程度，相比现有方法，提高了油纸绝缘受潮评估准确度，且可以得出更详细的受潮状况。
The present invention provides a method for evaluating the degree of uneven dampness of an oil-impregnated paper insulating assembly, comprising: step S1, forming a plurality of non-uniformly dampened oil-impregnated paper samples by using a plurality of uniformly dampened oil-impregnated paper insulation samples; The oil-impregnated paper sample is tested by frequency domain dielectric spectrum to obtain a plurality of first dielectric spectrum curves, and the corresponding relationship between each first dielectric spectrum curve and the degree of dampness of each oil-impregnated paper sample is established; Step S2 , perform a frequency domain dielectric spectrum test on the actual oil-impregnated paper insulation assembly, and obtain a second dielectric spectrum curve. When the similarity between the second dielectric spectrum curve and one of the first dielectric spectrum curves reaches a predetermined requirement , the dampness degree corresponding to the corresponding first dielectric spectrum curve is taken as the dampness degree of the actual oil-immersed insulating component. The present invention has the advantages of using the characteristic peaks of the frequency domain dielectric spectrum to evaluate the degree of uneven dampness of the oil-paper insulation, which improves the dampness evaluation accuracy of the oil-paper insulation compared with the existing method, and can obtain more detailed damp conditions.
Description
Technical Field
The invention relates to the technical field of power transmission detection, in particular to a method for evaluating the uneven moisture degree of an oil-impregnated paper insulating assembly.
Background
Oil-impregnated paper insulation is one of the most common insulation materials for power equipment, and is mainly used in insulation systems of equipment such as oil-impregnated transformers, oil-impregnated paper bushings and oil-impregnated capacitors. In a 110kV or above power grid system, the proportion of oil-impregnated paper insulation reaches more than 93%. Among them, the capacitive high-voltage bushing is one of typical oil-impregnated paper insulation devices, and is an indispensable external connection component of a power transformer. The transformer has the function of leading the winding lead out of the transformer and also plays a role in supporting and fixing the lead. Data show that the accident of the transformer bushing of 110kV and above accounts for a certain proportion of the total number of accidents, and the proportion of the accidents caused by the bushing is increased along with the increase of the voltage level. The failure or damage of the transformer bushing not only causes the transformer to be powered off, but also can cause the bushing to explode to cause the transformer to be damaged and even cause a fire to further expand the accident range. For the oil-impregnated paper insulating sleeve, the moisture content has an obvious acceleration effect on the aging of the insulating paper, the aging rate is higher as the moisture content is higher, and the polymerization degree reduction rate of the insulating paper is also obviously accelerated. Therefore, the safe and stable operation of the sleeve directly influences the stability of the whole power grid, and has great significance for the diagnosis and evaluation of the insulation state and the damp model of the whole power grid.
At present, the method for detecting the moisture content in the insulating paper comprises a drying weighing method, a Karl Fischer method, an oil-impregnated paper moisture equilibrium curve method and the like. The former two measurements must be taken to sample and destroy the insulation of equipment, and the weighing method is replaced by a Karl Fischer method due to low measurement precision. The oil-impregnated paper moisture balance curve method firstly measures the moisture content in oil, and then estimates the moisture content in paper according to the oil-impregnated paper moisture balance curve.
In existing methods for estimating water content in oil-impregnated paper insulation using FDS (frequency domain dielectric spectroscopy), the water content is generally considered to be equivalent water content and the water distribution is assumed to be uniform.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a method for evaluating the uneven moisture degree of an oil-impregnated paper insulation assembly, wherein the uneven moisture degree of the oil-impregnated paper insulation assembly is evaluated by utilizing a frequency domain dielectric spectrum characteristic peak.
In order to solve the technical problem, the invention provides a method for evaluating the uneven moisture degree of an oil-impregnated paper insulation assembly, which comprises the following steps:
step S1, combining a plurality of uniformly damped oil-impregnated paper insulation samples in different modes to form a plurality of non-uniformly damped oil-impregnated paper samples, performing frequency domain dielectric spectrum test on each non-uniformly damped oil-impregnated paper sample to obtain a plurality of first dielectric spectrum curves, and establishing a corresponding relation between each first dielectric spectrum curve and the damping degree of each non-uniformly damped oil-impregnated paper sample;
and step S2, performing frequency domain dielectric spectrum testing on the actual oil-impregnated paper insulating assembly to obtain a second dielectric spectrum curve, and when the similarity between the second dielectric spectrum curve and one of the first dielectric spectrum curves reaches a preset requirement, taking the moisture degree corresponding to the corresponding first dielectric spectrum curve as the moisture degree of the actual oil-impregnated paper insulating assembly.
Before the step S1, the method further includes: step S0, a plurality of uniformly damped oil-impregnated paper insulation samples with different damping degrees are manufactured, and frequency domain dielectric spectrum testing is carried out on each uniformly damped oil-impregnated paper insulation sample to obtain a plurality of third dielectric spectrum curves.
The method further comprises the following steps after the step S1: obtaining an impedance equivalent value of a dielectric spectrum curve of each uniformly damped oil-impregnated paper insulation sample in each superposition combination; calculating a dielectric loss curve of each superposed combination according to the obtained impedance equivalent value of each uniformly damped oil-impregnated paper insulation sample; and verifying the accuracy of the first dielectric spectrum curve obtained in step S1 by the calculated dielectric curve.
Wherein, the different oil impregnated paper insulation samples which are evenly affected with damp have different degrees of damp.
The oil-impregnated paper insulation assembly is used for equipment such as an oil-impregnated transformer, an oil-impregnated paper bushing and an oil-impregnated capacitor.
Wherein, the frequency domain dielectric spectrum test in the steps S1 and S2 is performed under the condition of 40 degrees and the input voltage is 200V.
And the thickness of the oil-impregnated paper sample subjected to non-uniform wetting after the plurality of oil-impregnated paper insulation samples subjected to uniform wetting are combined is the same as that of the single oil-impregnated paper sample subjected to uniform wetting.
The embodiment of the invention has the beneficial effects that:
according to the embodiment of the invention, by evaluating the uneven moisture degree of the oil-impregnated paper insulation sample, on one hand, the evaluation accuracy of the oil-impregnated paper insulation moisture is improved, and more detailed moisture condition can be obtained; on one hand, compared with a drying and weighing method, the method can obviously improve the testing precision and can obtain the specific moisture distribution condition; on the other hand, compared with the Karl-Fischer method, the invention can realize nondestructive testing, has no damage to the sample or the oil paper insulation power equipment, and is convenient and quick in the testing process.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic flow chart of an embodiment of a method for evaluating uneven moisture of an oil impregnated paper insulation assembly.
Fig. 2 is a schematic flow chart of another embodiment of a method for evaluating the uneven moisture level of an oil impregnated paper insulation assembly.
FIG. 3 is a schematic view of another embodiment of tan delta-f curves at different water contents in the present invention.
FIG. 4 is a schematic view of another embodiment of the C' -f curve at different water contents in the present invention.
FIG. 5 is a schematic view of another embodiment of the C "-f curve of the present invention at different water contents.
FIG. 6 is a schematic view of another example of tan delta-f characteristic curve of equivalent water content of 2% in the present invention.
FIG. 7 is a schematic view of another example of tan delta-f characteristic curve of equivalent water content of 3% in the present invention.
FIG. 8 is a schematic view of another example of tan delta-f characteristic curve of equivalent water content of 4% in the present invention.
Fig. 9 is a schematic diagram of another embodiment of the equivalent circuit diagram of the double-layer oiled paper insulation in the invention.
Detailed Description
Embodiments of the present invention will be described below with reference to the accompanying drawings.
Fig. 1 is a schematic flow chart of an embodiment of a method for evaluating the uneven moisture level of an oil impregnated paper insulation assembly according to the present invention. The invention is applicable to insulation systems of equipment such as oil-immersed transformers, oil-paper bushings, oil-immersed capacitors and the like.
Step S1, combining the uniformly moistened oil-impregnated paper insulation samples in different modes to form a plurality of uniformly moistened oil-impregnated paper samples, performing frequency domain dielectric spectrum testing on each uniformly moistened oil-impregnated paper sample to obtain a plurality of first dielectric spectrum curves, and establishing a corresponding relation between each first dielectric spectrum curve and the moistening degree of each uniformly moistened oil-impregnated paper sample.
And step S2, performing frequency domain dielectric spectrum testing on the actual oil-impregnated paper insulating assembly to obtain a second dielectric spectrum curve, and when the similarity between the second dielectric spectrum curve and one of the first dielectric spectrum curves reaches a preset requirement, taking the moisture degree corresponding to the corresponding first dielectric spectrum curve as the moisture degree of the actual oil-impregnated paper insulating assembly.
Fig. 2 is a schematic flow chart of another embodiment of the method for evaluating the uneven moisture level of the oil-impregnated paper insulation assembly, which may include:
step S0, a plurality of uniformly damped oil-impregnated paper insulation samples with different damping degrees are manufactured, and frequency domain dielectric spectrum testing is carried out on each uniformly damped oil-impregnated paper insulation sample to obtain dielectric spectrum curves of the plurality of uniformly damped oil-impregnated paper insulation samples.
Step S1, combining the uniformly moistened oil-impregnated paper insulation samples in different modes to form a plurality of uniformly moistened oil-impregnated paper samples, performing frequency domain dielectric spectrum testing on each uniformly moistened oil-impregnated paper sample to obtain a plurality of first dielectric spectrum curves, and establishing a corresponding relation between each first dielectric spectrum curve and the moistening degree of each uniformly moistened oil-impregnated paper sample;
step S11, obtaining an impedance equivalent value of the dielectric spectrum curve of each uniformly damped oil-impregnated paper insulation sample in each superposition combination, calculating a dielectric loss curve of each superposition combination according to the obtained impedance equivalent value of each uniformly damped oil-impregnated paper insulation sample, and verifying the accuracy of the first dielectric spectrum curve obtained in the step S1 through the calculated dielectric curve.
And step S2, performing frequency domain dielectric spectrum testing on the actual oil-impregnated paper insulating assembly to obtain a second dielectric spectrum curve, and when the similarity between the second dielectric spectrum curve and one of the first dielectric spectrum curves reaches a preset requirement, taking the moisture degree corresponding to the corresponding first dielectric spectrum curve as the moisture degree of the actual oil-impregnated paper insulating assembly.
The method for evaluating the moisture degree of the oil-impregnated paper insulation assembly according to the present invention will be described in detail with reference to a specific example.
In step S0, an initial moisture content may be prepared of: dry (dry), 1%, 2%, 3%, 4%, 5%, 6% uniformly moistened oilpaper cell laminate samples. Wherein the water content is that 6% obtains for manual humidification, and equipment in service can not wet so seriously usually, and the purpose is whether have better uniformity with the water content when the water content is great for observing the moisture change law, provides more data points in order to improve the fitting accuracy for the evaluation curve. Obtaining unit laminated oil-impregnated paper samples with different water contents (< 0.5%, 1%, 2%, 3%, 4%, 5% and 6%), and performing frequency domain dielectric spectrum test, wherein the frequency band range is 1 mHz-5 kHz, the test temperature is 40 ℃, and the test voltage peak value is 200V. The obtained dielectric spectrum curves are shown in fig. 3, 4 and 5.
In step S1, the uniformly damped samples are combined into a non-uniformly damped oiled paper insulation sample, and a frequency domain dielectric spectrum test is performed to obtain dielectric spectrum curves corresponding to different non-uniformities. By way of example, the cable paper unit stacks may be recombined into unit stacks having equivalent moisture contents of 2%, 3%, 4% and maintained with the thickness of the unit stacks prior to combination, as shown in table 1. The uneven moisture degree n is defined as the deviation degree of the local water content and the equivalent water content, and the larger the value of n, the more uneven the moisture is, as the following formula
TABLE 1 equivalent water content of unit laminated oil-impregnated paper test sample
The frequency domain dielectric spectrum test (test voltage 200V) was performed on the three types of non-uniformly wetted test articles at 40 ℃, and the test results are shown in fig. 6, fig. 7 and fig. 8, respectively.
In step S11, the frequency domain dielectric spectrum of the uniform moisture content of the non-uniform moisture test article of step S1 is replaced with the frequency domain dielectric spectrum of the uniform moisture content of step S0. Due to the fact that the thickness is doubled, capacitance needs to be doubled during calculation, and the test results are compared by using a double-layer series model according to equivalent polarization and loss parameters of the composite medium. The impedance Z resulting from dielectric response testing of the frequency domain dielectric spectrum of uniform water content can be represented by the R, C parallel equivalent circuit as follows
According to the equivalent circuit model of fig. 9, the interface polarization loss tan δ -f curve caused by non-uniformity when the double-layer oiled paper insulation combination is obtained by substituting the RC equivalent circuit parameters with different water contents in a single layer into the formula (3).
Comparing the tan delta-f curve obtained by calculation with a frequency domain dielectric spectrum curve measured by the oil paper sample subjected to uneven moisture, and obtaining the uneven moisture degree of the oil paper insulation sample by checking a water content and moisture degree corresponding table similar to the table 1 when the curve coincidence degree is highest.
Finally, in step S2, the actual moisture degree of the oil-impregnated paper insulation assembly can be determined according to the similarity between the dielectric spectrum curve obtained by the actual oil-impregnated paper insulation assembly and the dielectric spectrum curve of the uneven moisture sample.
In summary, the embodiment of the invention, by using the method for evaluating the uneven moisture degree of the oil-impregnated paper insulation assembly, on one hand, the evaluation accuracy of the oil-impregnated paper insulation moisture degree is improved, and more detailed moisture conditions can be obtained; on one hand, compared with a drying and weighing method, the method can obviously improve the testing precision and can obtain the specific moisture distribution condition; on the other hand, compared with the Karl-Fischer method, the invention can realize nondestructive testing, has no damage to the sample or the oil paper insulation power equipment, and is convenient and quick in the testing process.
The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention, and it is therefore to be understood that the invention is not limited by the scope of the appended claims.
Claims (3)
1. A method of assessing uneven moisture exposure of an oil impregnated paper insulation assembly comprising:
step S0, a plurality of uniformly damped oil-impregnated paper insulation samples with different damping degrees are manufactured, and frequency domain dielectric spectrum testing is carried out on each uniformly damped oil-impregnated paper insulation sample to obtain a plurality of third dielectric spectrum curves; wherein, the different oil-impregnated paper insulation samples which are uniformly wetted have different degrees of wetting; the oil-immersed paper insulation assembly is used in an oil-immersed transformer, an oil-immersed sleeve and an oil-immersed capacitor;
step S1, combining a plurality of uniformly damped oil-impregnated paper insulation samples in different modes to form a plurality of non-uniformly damped oil-impregnated paper samples, performing frequency domain dielectric spectrum test on each non-uniformly damped oil-impregnated paper sample to obtain a plurality of first dielectric spectrum curves, and establishing a corresponding relation between each first dielectric spectrum curve and the damping degree of each non-uniformly damped oil-impregnated paper sample;
obtaining an impedance equivalent value of a dielectric spectrum curve of each uniformly damped oil-impregnated paper insulation sample in each superposition combination, calculating a dielectric loss curve of each superposition combination according to the obtained impedance equivalent value of each uniformly damped oil-impregnated paper insulation sample, and verifying the accuracy of the first dielectric spectrum curve obtained in the step S1 through the calculated dielectric loss curve;
and step S2, performing frequency domain dielectric spectrum testing on the actual oil-impregnated paper insulating assembly to obtain a second dielectric spectrum curve, and when the similarity between the second dielectric spectrum curve and one of the first dielectric spectrum curves reaches a preset requirement, taking the moisture degree corresponding to the corresponding first dielectric spectrum curve as the moisture degree of the actual oil-impregnated paper insulating assembly.
2. The method as claimed in claim 1, wherein the frequency domain dielectric spectrum test in steps S1 and S2 is performed at 40 degrees with an input voltage of 200V.
3. The method according to claim 1, wherein the combined thickness of the uniformly dampened non-uniform oil impregnated paper samples after the plurality of uniformly dampened oil impregnated paper insulation samples is the same as the thickness of a single uniformly dampened oil impregnated paper sample.
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| CN108982603B (en) * | 2018-08-24 | 2019-09-06 | 西南交通大学 | A test method for damp state of oil-immersed casing |
| CN112505112A (en) * | 2020-12-08 | 2021-03-16 | 海南电网有限责任公司电力科学研究院 | FDS-based transformer local damping feature extraction method |
| CN112834872A (en) * | 2020-12-22 | 2021-05-25 | 深圳供电局有限公司 | Evaluation method, device and computer equipment for local dampness evaluation of transformer bushing end screen |
| CN113447537B (en) * | 2021-06-25 | 2023-05-05 | 海南电网有限责任公司电力科学研究院 | Method and device for measuring dielectric spectrum of oilpaper insulating frequency domain, storage medium and terminal |
| CN113484369A (en) * | 2021-06-25 | 2021-10-08 | 海南电网有限责任公司电力科学研究院 | Oil paper insulation dielectric spectrum characteristic analysis method |
| CN115219793B (en) * | 2021-06-29 | 2025-07-11 | 国网山东省电力公司济宁供电公司 | A method and system for evaluating moisture status of oil-paper insulated power equipment |
| CN113588733B (en) * | 2021-07-09 | 2023-05-02 | 深圳供电局有限公司 | Method and equipment for evaluating insulating moisture content of oilpaper |
| CN117169788B (en) * | 2023-11-03 | 2024-01-30 | 江苏嘉盟电力设备有限公司 | Method for analyzing moisture state of middle joint of crosslinked polyethylene insulated power cable |
| CN117407631B (en) * | 2023-12-15 | 2024-02-27 | 南京中鑫智电科技有限公司 | Method and system for evaluating high-voltage sleeve damp state |
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