CN117969608A - Nondestructive testing method for 10kV dry-type distribution transformer low-voltage side winding material based on eddy current - Google Patents
Nondestructive testing method for 10kV dry-type distribution transformer low-voltage side winding material based on eddy current Download PDFInfo
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Abstract
The invention relates to the technical field of detection of materials of dry-type distribution transformer windings, in particular to a nondestructive detection method of a 10kV dry-type distribution transformer low-voltage side winding material based on eddy current. The detection method comprises the following steps: obtaining a plurality of simulated low-voltage side windings according to the difference of the materials of the conductors, the difference of the thicknesses of the conductors, the difference of the surface areas of the conductors, the difference of the thicknesses of the insulating layers and the difference of the number of turns of the windings; respectively detecting the conductivity of each simulated low-voltage side winding to obtain a plurality of simulated conductivities; detecting the conductivity of a low-voltage side winding of the dry-type distribution transformer to be detected to obtain the actually measured conductivity; and comparing the actually measured electric conductivity with each analog electric conductivity, wherein the conductor material in the analog low-voltage side winding corresponding to the group with the smallest absolute difference is the material used by the conductor in the dry-type distribution transformer low-voltage side winding to be measured. The method can realize detection and judgment of the conductor material in the dry-type transformer on the premise of not damaging the transformer, and has the advantages of safety, environmental protection, high accuracy and the like.
Description
Technical Field
The invention relates to the technical field of detection of materials of dry-type distribution transformer windings, in particular to a nondestructive detection method of a 10kV dry-type distribution transformer low-voltage side winding material based on eddy current; more particularly, relates to a nondestructive testing method for a 10kV dry-type distribution transformer low-voltage side winding material based on eddy current and application thereof.
Background
The distribution transformer is one of power transformers and is also one of key equipment of a power distribution network, and plays a role in converting voltage measured by a feeder line of the power distribution network into voltage which can be directly used by a user side, and whether the distribution transformer can normally operate is related to whether a distribution system can reliably, safely, economically and high-quality operate. Meanwhile, as one of the main categories of distribution transformer, the dry distribution transformer has the advantages of large usage amount, wide popularization range, low technical threshold, more production enterprises, good product quality and uneven quality, and causes more faults, and under the condition that the distribution transformer breaks down, the distribution transformer can damage equipment, possibly cause large-scale power failure, even can bring potential safety risks, and it is important to ensure the normal operation of the distribution transformer, so that the detection technology research needs to be enhanced to ensure the safety of the distribution transformer.
Copper is the most common choice of dry distribution transformer winding materials, but with the increasing price of copper, manufacturers have proliferated to let many transformer manufacturers enter the negative interest rate era, so that some 'sub-filled' transformers start to enter the market, and in the current dry transformer production, some bad merchants replace copper materials with aluminum materials to be used as conductor materials. In order to reduce the cost, some manufacturers discard the copper foil used as a conductor and replace the copper foil with an aluminum foil with lower price, which causes serious potential safety hazards and slows down the development of the dry-type transformer manufacturing industry.
If the copper material is replaced with an aluminum material: on one hand, as the conductivity of copper and aluminum are in a certain gap, and copper conductivity is higher than aluminum in general, the dry distribution transformer adopting the copper winding has less electric quantity loss in transmission than the dry distribution transformer adopting the aluminum winding, and the purpose of saving energy is better achieved; on the other hand, because the copper winding and the aluminum winding have different resistances, and the aluminum resistivity is higher than that of copper at normal temperature, in long-term power operation, the dry distribution transformer adopting the aluminum winding can generate more heat than the copper winding, and a series of problems such as defects and the like are caused by heating.
Therefore, in order to timely determine the type of winding materials in a dry-type distribution transformer, it is necessary to provide a method for detecting and determining the conductor materials in the dry-type transformer to be tested under the condition that the transformer is not damaged.
In view of this, the present invention has been made.
Disclosure of Invention
The invention aims to provide a nondestructive detection method for a 10kV dry-type distribution transformer low-voltage side winding material based on eddy current, which can realize detection and judgment of conductor materials in a dry-type transformer on the premise of not damaging the transformer and has the advantages of safety, environmental protection, high accuracy and the like.
The second aim of the invention is to provide an application of a nondestructive testing method for a10 kV dry-type distribution transformer low-voltage side winding material based on eddy current in judging the dry-type distribution transformer low-voltage side winding conductor material.
In order to achieve the above object of the present invention, the following technical solutions are specifically adopted:
the invention firstly provides a nondestructive testing method for a 10kV dry-type distribution transformer low-voltage side winding material based on eddy current, which comprises the following steps:
(a) Obtaining a plurality of simulated low-voltage side windings according to different materials of conductors, different thicknesses of the conductors, different surface areas of the conductors, different thicknesses of the insulating layers and different numbers of turns of the windings;
(b) Respectively detecting the conductivity of each analog low-voltage side winding to obtain a plurality of analog conductivities;
(c) Detecting the conductivity of the low-voltage side winding of the dry-type distribution transformer to be detected to obtain the actually measured conductivity;
(d) And comparing the actually measured electric conductivity with each analog electric conductivity, wherein the conductor material in the analog low-voltage side winding corresponding to the group with the smallest absolute difference is the material used by the conductor in the dry-type distribution transformer low-voltage side winding to be measured.
The invention further provides application of the nondestructive testing method for the 10kV dry-type distribution transformer low-voltage side winding material based on eddy current in judging the dry-type distribution transformer low-voltage side winding conductor material.
Compared with the prior art, the invention has the beneficial effects that:
According to the nondestructive testing method provided by the invention, the eddy-current-based conductivity detector is utilized to respectively prepare a plurality of simulated low-voltage side windings according to the differences of the material of the conductor, the thickness of the conductor, the surface area of the conductor, the thickness of the insulating layer and the number of turns of the windings, so that a basis is provided for comparison and judgment of the conductivity of the low-voltage side windings of the dry-type distribution transformer to be tested, and the material of the conductor can be judged on the premise of not damaging the transformer and conducting conductivity detection on the low-voltage side windings of the dry-type transformer through the external insulating layer, so that the nondestructive testing method has the advantages of safety, environmental protection, high accuracy and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a partial cross-sectional view of an analog low-side winding provided by the present invention;
fig. 2 is a schematic structural diagram of the eddy current conductivity meter provided by the invention.
Detailed Description
The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and detailed description, but it will be understood by those skilled in the art that the examples described below are some, but not all, examples of the present invention, and are intended to be illustrative of the present invention only and should not be construed as limiting the scope of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
In the present invention, unless specifically stated otherwise, the terms "first", "second", "third", "fourth", etc. are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or quantity or as implicitly indicating the importance or quantity of the indicated technical feature. Moreover, the terms "first," "second," "third," "fourth," and the like are used for non-exhaustive list description purposes only, and are not to be construed as limiting the number of closed forms.
The terms "comprising" and "including" as used herein mean open ended or closed ended, unless otherwise noted. For example, the terms "comprising" and "comprises" may mean that other components not listed may be included or included, or that only listed components may be included or included.
In the present invention, "one or more" or "at least one" means any one, any two or more of the listed items unless specifically stated otherwise. Wherein "several" means any two or more.
In a first aspect, the invention provides a nondestructive testing method for a 10kV dry-type distribution transformer low-voltage side winding material based on eddy current, in particular to a method for detecting or judging the material of a conductor in a low-voltage side winding, which specifically comprises the following steps:
(a) And preparing a plurality of simulated low-voltage side windings according to the difference of conductor materials in the low-voltage side windings, the difference of conductor thicknesses, the difference of conductor surface areas, the difference of insulating layer thicknesses in the low-voltage side windings and the difference of winding turns of the low-voltage side windings.
It will be appreciated that there are many factors that affect the conductivity measurements, some factors having a greater effect and some factors having a lesser effect.
According to the invention, the plurality of simulated low-voltage side windings are respectively obtained by adopting a variable control method for factors with larger influence on different conductor materials, different conductor thicknesses, different conductor surface areas, different insulating layer thicknesses and different winding turns, the method is strict, and the final detection and judgment accuracy is high.
In some embodiments, in step (a), the analog low-voltage side winding includes a winding unit and an insulating layer coated on an outer surface of the winding unit.
Referring to fig. 1, a partial cross-sectional view of an analog low-side winding provided by the present invention is shown.
In some embodiments, the winding unit includes at least one layer of conductors and at least one layer of DMD insulation paper alternately stacked.
In some specific embodiments, the winding unit is cylindrical or cylindrical in shape.
In some embodiments, the insulating layer is formed from at least one layer of DMD insulating paper.
The winding turns refer to the number of superimposed layers in the winding unit, namely the number of layers of DMD insulating paper in the winding unit.
(B) And respectively detecting the conductivity of each simulated low-voltage side winding to obtain a plurality of simulated conductivity data which are used as comparison data of the conductivity of the low-voltage side winding of the dry-type distribution transformer to be tested.
In some embodiments, in step (b), the conductivity of each simulated low side winding is measured at least five times, and then averaged, preferably at least ten times.
(C) And detecting the conductivity of the low-voltage side winding of the dry-type distribution transformer to be detected to obtain the actually measured conductivity.
In some embodiments, in step (c), the conductivity of the low-side winding of the dry-type power distribution transformer to be tested is measured at least five times, and then averaged, preferably measured at least ten times.
The step (b) and the step (c) are not sequential, and the step (b) may be performed first, the step (c) may be performed first, and the step (b) and the step (c) may be performed simultaneously.
(D) And (c) comparing the actually measured electric conductivity obtained in the step (c) with the analog electric conductivity obtained in each step (b) respectively to obtain a plurality of groups of absolute differences, namely absolute values of differences between the actually measured electric conductivity and the analog electric conductivity, wherein the conductor material in the analog low-voltage side winding corresponding to the group with the smallest absolute difference is the material used by the conductor in the dry-type distribution transformer low-voltage side winding to be tested.
The material of the conductor in the certain simulated low-voltage side winding corresponding to the certain simulated conductivity with the smallest difference of the measured conductivities is the material used for the conductor in the low-voltage side winding of the dry-type distribution transformer to be measured.
For example, the measured conductivity is 10% iacs, the simulated conductivity obtained by detecting the first simulated low-voltage side winding is 7% iacs, the simulated conductivity obtained by detecting the second simulated low-voltage side winding is 8% iacs, the simulated conductivity obtained by detecting the third simulated low-voltage side winding is 9.9% iacs, the first absolute difference= |10% iacs-7% iacs|=3% iacs, the second absolute difference= |10% iacs-8% iacs|=2% iacs, the third absolute difference= |10% iacs-9.9% iacs|=0.1% iacs, and the group with the smallest absolute difference is the third group, so that the conductor material in the third simulated low-voltage side winding is the material used for the conductor in the low-voltage side winding to be measured.
It can be understood that the nondestructive testing method provided by the invention can be used for judging the conductor materials in the dry-type transformer and can also be used for judging the conductor materials in other types of transformers. Meanwhile, the nondestructive testing method provided by the invention can be used for judging the material of the conductor in the low-voltage side winding of the 10kV dry-type distribution transformer, and can also be used for judging the material of the conductor in the low-voltage side winding of other transformers. In contrast, the nondestructive detection method is used for judging the conductor material in the low-voltage side winding of the 10kV dry-type distribution transformer, and is not required to be disassembled, so that the accuracy is higher.
Because the winding unit of the low-voltage side winding of the dry-type transformer is wrapped by the outer DMD resin insulating layer, the conductivity of the winding unit cannot be directly detected, but the conductivity of the whole low-voltage side winding needs to be detected through the DMD resin insulating layer, so that factors possibly influencing the conductivity detection result need to be found out, experiments are designed to verify influence factors and irrelevant factors, and the conductivity and the numerical range of the low-voltage side winding of the dry-type transformer, which are measured through the insulating layer under each structural condition, are determined, and are the detection obstacle for the conductivity and the judgment basis for distinguishing the dry-type transformers with different materials. The inventor finds that the material of the conductor, the thickness of the conductor, the surface area of the conductor, the thickness of the insulating layer and the number of winding turns have great influence on the conductivity detection result through a large number of experiments.
Therefore, the nondestructive testing method provided by the invention can be used for detecting the conductivity of the low-voltage side winding of the dry-type transformer through the external insulating layer on the premise of not damaging the transformer by using the conductivity detector based on eddy current, and then comparing the detection value with the conductivity reference value of the simulated low-voltage side winding of the corresponding different structures and different material conditions determined through experiments so as to judge the material of the conductor in the winding, and has the advantages of safety, environmental protection, easiness in operation, high accuracy and the like.
In some specific embodiments, in step (a), the method for preparing the simulated low-voltage side winding comprises the steps of: and respectively taking copper foil or aluminum foil as a conductor, stacking the conductor and DMD insulating paper, and winding n layers to obtain the winding unit with the number of turns (or layers) of n. It will be appreciated that the number of turns is the same as the number of layers of DMD insulation paper in the resulting winding unit after winding.
And then winding m layers of DMD insulating paper on the outer surface of the winding unit to obtain the simulated low-voltage side winding.
In some embodiments, the winding of the m layers of DMD insulation paper is followed by a baking step. Wherein the parameters of baking have little effect on conductivity, so conventional baking parameters can be used.
As an example, the baking temperature is 100 to 150 ℃ and the baking time is 1 to 3 hours, but is not limited thereto.
In some embodiments, each layer of the conductor has a thickness of 0.5 to 1mm; including but not limited to a point value of any one of 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, or a range value therebetween.
In some embodiments, several simulated low-side windings are made using conductors having thicknesses of 0.5mm, 0.8mm, and 1.0mm, respectively.
In some embodiments, the surface area of each layer of the conductor is 900 to 12100mm 2; including but not limited to a point value of any one of 900mm2、1600mm2、2500mm2、3600mm2、4900mm2、6400mm2、8700mm2、10000mm2、12100mm2 or a range value between any two.
By way of example, the length x width of each layer of the conductor comprises, for example, 30mm x 30mm, 50mm x 50mm, 70mm x 70mm, 90mm x 90mm or 110mm x 110mm.
In some embodiments, the thickness of each layer of the DMD insulation paper is from 0.1 to 0.3mm, including but not limited to a dot value of any one of 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, or a range of values therebetween.
In some embodiments, the simulated low side winding is made of class F DMD insulating paper having a thickness of 0.2 mm.
In some specific embodiments, n=1 to 10; including but not limited to a point value of any one of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or a range value between any two.
In some specific embodiments, the m=1 to 10, including but not limited to a point value of any one of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or a range value between any two.
In some embodiments, the method for preparing the simulated low-voltage side winding comprises: according to the material of the conductor, the thickness of the conductor and the thickness variation of the external insulation layer, copper foils with the same surface areas and three thicknesses of 0.5mm, 0.8mm and 1.0mm and aluminum foils with the three thicknesses are respectively used as conductors, winding units with the number of turns of n=10 are manufactured, and 1 to 10 layers of DMD insulation paper are respectively wound on the outer surfaces of the winding units, so that a plurality of simulated low-voltage side windings are obtained.
It has been found that the conductivity first shows a slow decrease with increasing number of layers of DMD insulating paper wound on the outer surface of the winding unit, and then shows a gradual increase in the rate of decrease, the number of layers increasing to 8 hours where the rate reaches a maximum. For example, when the number of layers increases from 1 to 2 or from 2 to 3, the rate of conductivity decrease is about 0.3% and 2.4%, respectively; when the number of layers increases from 3 to 4 or from 4 to 5, the conductivity decreases at about 6.1% and 9.9%, respectively; the rate of conductivity decrease was about 13.1% and 14.3% when the number of layers increased from 5 to 6 or from 6 to 7, respectively.
The research shows that the influence condition of the conductor material (copper foil or aluminum foil) on the conductivity is as follows: the conductivity of the simulated low-voltage side winding made of the aluminum foil is obviously lower than that of the simulated low-voltage side winding made of the copper foil. The difference between the conductivity measurements becomes smaller as the number of layers of DMD insulation paper wound around the outer layer increases. When the number of layers of the DMD insulating paper wound on the outer layer is 5, the electric conductivities measured by the simulated low-voltage side winding made of the copper foil and the simulated low-voltage side winding made of the aluminum foil are respectively about 80% IACS and 50% IACS, and a gap of about 30% IACS still exists between the two, so that the difference can be used for judging that the material of the windings is copper or aluminum.
In some embodiments, the method for preparing the simulated low-voltage side winding comprises: according to the change of winding turns, copper foil with the same surface area and 0.5mm thick and aluminum foil with the same surface area are respectively used as conductors, 5 layers of DMD insulating paper are wound on the outer surface of a winding unit, and the winding turns in the winding unit are sequentially increased from 1 to 10 to form a plurality of simulated low-voltage side windings.
In some embodiments, the method for preparing the simulated low-voltage side winding comprises: according to the change of the surface area of the conductor, copper foils with different surface areas and aluminum foils with different surface areas and 0.5mm thickness are used as conductors, the number of turns in the winding unit is 5, and a plurality of simulated low-voltage side windings of 5 layers of DMD insulating paper are wound on the outer surface of the winding unit.
In some embodiments, in step (b) and/or step (c), the means for detecting comprises an eddy current conductivity meter. The eddy current conductivity meter is a conductivity detector based on an eddy current principle, and the detector has the advantage of convenience in detection, and the probe can be used for gap detection.
In some specific embodiments, the conductivity detector based on the eddy current principle uses a probe model ES20, and the measuring range of the detector is 1-112% IACS.
Fig. 2 is a schematic structural diagram of an eddy current conductivity meter according to the present invention, but the structure should not be construed as limiting the scope of the category of the eddy current conductivity meter according to the present invention.
In some specific embodiments, the method for detecting the conductivity by using the conductivity detector based on the eddy current principle is as follows: calibrating the conductivity detector by using a standard block; the probe of the conductivity detector is vertically pressed on the surface of the detected object, and the pressing force is required to be kept stable during each detection; at the start of detection, each data was taken from the average of several detection results, and the standard deviation of the several detection results was controlled to be 0.35% iacs or less.
In some specific embodiments, in the step (b) and/or the step (c), during the detection, the probe of the device for detecting is placed perpendicular to the side surface of the winding on the analog low voltage side, so as to improve the accuracy of the detection result/judgment result.
In some embodiments, in step (b) and/or step (c), the number of times the detection is greater than or equal to 5, including but not limited to any one of 5,6, 8, 10, 12, 13, 15, 20, or any range between any two, and then taking an average.
In some specific embodiments, in the step (c), the detection is performed on an area of the top end of the winding on the low-voltage side of the to-be-detected dry-type distribution transformer, where the distance is beyond 2mm, so as to improve the accuracy of the detection result/judgment result and prevent the top end from contacting unevenly and having a gap to interfere with the detection result.
In some specific embodiments, in order to further improve the accuracy of the detection result and the determination result, the condition for detecting the conductivity of each of the analog low-voltage side windings should be the same as or similar to the field environment for actually detecting the conductivity of the low-voltage side winding of the to-be-detected dry-type power distribution transformer.
In some specific embodiments, the details of the structure of the low-voltage side winding of the dry-type transformer can be determined by in-situ investigation of the dry-type transformer manufacturer, for example, the number of layers of DMD insulating paper wound on the outer surface of the winding unit in the low-voltage side winding of the dry-type transformer is 5, then m=5 can be directly used, and other variables can be controlled to prepare a plurality of analog low-voltage side windings.
In a second aspect, the invention provides an application of the nondestructive testing method for the material of the low-voltage side winding of the 10kV dry-type distribution transformer based on eddy current in judging the material of the conductor of the low-voltage side winding of the dry-type distribution transformer.
The nondestructive testing method for the conductor material in the low-voltage side winding is convenient to operate, and can rapidly distinguish the conductor material, so that the quality of the transformer is ensured.
Embodiments of the present invention will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
Examples
In this embodiment, taking a low-voltage side winding of a certain 10kV dry-type transformer as an example, the nondestructive testing method of the conductor material includes the following steps:
(1) According to the material of the conductor, the thickness of the conductor and the thickness of the external insulation layer:
Winding units with n=10 turns were fabricated using a copper foil with a surface area of 4900mm 2 (length×width=70 mm×70 mm), a thickness of 0.5mm, and an aluminum foil with a surface area of 4900mm 2 (length×width=70 mm×70 mm), and a thickness of 0.5mm as conductors, and 1 to 10 layers of DMD insulation paper (the single-layer thickness of the DMD insulation paper used in this example was 0.2 mm) were wound around the outer surfaces of the winding units, respectively, to obtain 20 analog low-voltage side windings.
And winding units with n=10 turns were fabricated using a copper foil with a surface area of 4900mm 2 (length×width=70 mm×70 mm), a thickness of 0.8mm, and an aluminum foil with a surface area of 4900mm 2 (length×width=70 mm×70 mm), and a thickness of 0.8mm as conductors, respectively, and 1 to 10 layers of DMD insulating paper were wound on the outer surfaces of the winding units, respectively, to obtain 20 analog low-voltage side windings.
Then, winding units with n=10 turns were fabricated by using 4900mm 2 (length×width=70 mm×70 mm) in surface area, 1.0mm thick copper foil, 4900mm 2 (length×width=70 mm×70 mm) in surface area and 1.0mm thick aluminum foil as conductors, and 1 to 10 layers of DMD insulating paper were wound around the outer surfaces of the winding units, respectively, to obtain 20 simulated low-voltage side windings.
(2) According to the change of winding turns, a copper foil with a surface area of 4900mm 2 (length×width=70 mm×70 mm), a thickness of 0.5mm and an aluminum foil with a surface area of 4900mm 2 (length×width=70 mm×70 mm) and a thickness of 0.5mm are used as conductors respectively to manufacture 5 layers of DMD insulating paper on the outer surface of a winding unit, the number of turns in the winding unit is sequentially increased from 1 to 10 on the simulated low-voltage side winding, and the number of the simulated low-voltage side windings is 20.
(3) According to the change of the surface area of the conductor, cutting a copper foil with the thickness of 0.5mm and an aluminum foil with the thickness of 0.5mm into five conductors with different surface areas of 30mm multiplied by 30mm, 50mm multiplied by 50mm, 70mm multiplied by 70mm, 90mm multiplied by 90mm and 110mm multiplied by 110mm respectively, then manufacturing a winding unit with the number of turns of 5, winding 5 layers of simulated low-voltage side windings of DMD insulating paper on the outer surface of the winding unit, and the number of the simulated low-voltage side windings is 10.
(4) Calibrating the eddy current conductivity meter, and then respectively detecting the conductivity of each simulated low-voltage side winding manufactured in the step (1), the step (2) and the step (3), so as to obtain 87 simulated conductivity data (90 groups are totally used, 3 groups of unfavorable data are removed), wherein when each simulated low-voltage side winding is detected, the probe of the eddy current conductivity meter and the surface of a detection object are in a vertical relation (shown in fig. 2), the pressing force detected each time is kept stable, and the detection time is 2s; each valid data is taken from the average of ten test data and it is ensured that the standard deviation of the ten test data is less than 0.35% iacs; according to the analysis and arrangement of all the obtained effective data, extraneous factors (such as damage of DMD insulating paper, burrs of conductors and other unfavorable data, 3 groups of the unfavorable data) are removed, 87 reference data (namely 87 simulated conductivities) which can be used as the winding materials for distinguishing the conductivity detection of the winding on the low-voltage side of the field dry-type distribution transformer are obtained, and the conductivity part data of the simulated low-voltage side winding are shown in table 1.
Table 1 partial simulation conductivity data
(5) And detecting the electric conductivity of the low-voltage side windings of the 5 to-be-detected dry-type distribution transformer on site, wherein the area, which is 2mm away from the top end, of the side surface of the low-voltage side windings of the to-be-detected dry-type distribution transformer is taken as a detection surface of an eddy current conductivity meter to detect the electric conductivity, and the measured electric conductivity is obtained, and the data are shown in Table 2.
Table 2 actual conductivity data
(6) And (3) comparing the actually measured electric conductivity obtained in the step (5) with the analog electric conductivity obtained in each step (4), wherein the conductor material in the analog low-voltage side winding corresponding to the group with the smallest absolute difference is the material used for the conductor in the low-voltage side winding of the dry-type distribution transformer to be detected.
For example, the conductivity value of the low-voltage side winding of the No. 1 dry-type distribution transformer to be tested in table 2 is 71.14% iacs, which is closest to the conductivity value of the 6# copper analog low-voltage side winding in table 1 (i.e. the absolute difference is the smallest), so that the copper material of the conductor in the 6# copper analog low-voltage side winding is the copper material used for the conductor in the No. 1 dry-type distribution transformer low-voltage side winding.
For another example, the conductivity value of the low-voltage side winding of the dry-type distribution transformer to be tested 2 in table 2 is 41.17% iacs, which is closest to (i.e. the absolute difference between) the conductivity value of the 10# aluminum analog low-voltage side winding in table 1 is 40.08% iacs, so that the aluminum material of the conductor in the 10# aluminum analog low-voltage side winding is the material used by the conductor in the dry-type distribution transformer to be tested 2, i.e. aluminum.
Therefore, the nondestructive detection method provided by the invention can realize detection and judgment of the conductor material in the dry-type transformer on the premise of not damaging the transformer, and has high accuracy.
In addition, the nondestructive testing method provided by the invention not only can judge the conductor material, but also provides guidance for judging the thickness of a single turn of the conductor, the number of external insulation turns and the thickness of an external insulation layer, for example, the thickness of the single turn of the conductor, the number of external insulation turns and the thickness of the external insulation layer of the low-voltage side winding of the No. 2 dry-type transformer to be tested can be judged according to the 10# aluminum simulation while the thickness of the single turn of the conductor, the number of external insulation turns and the thickness of the external insulation layer of the low-voltage side winding of the No. 2 dry-type transformer to be tested are judged.
While the invention has been illustrated and described with reference to specific embodiments, it is to be understood that the above embodiments are merely illustrative of the technical aspects of the invention and not restrictive thereof; those of ordinary skill in the art will appreciate that: modifications may be made to the technical solutions described in the foregoing embodiments, or equivalents may be substituted for some or all of the technical features thereof, without departing from the spirit and scope of the present invention; such modifications and substitutions do not depart from the spirit of the corresponding technical solutions; it is therefore intended to cover in the appended claims all such alternatives and modifications as fall within the scope of the invention.
Claims (10)
1. The nondestructive testing method for the 10kV dry-type distribution transformer low-voltage side winding material based on eddy current is characterized by comprising the following steps of:
(a) Obtaining a plurality of simulated low-voltage side windings according to different materials of conductors, different thicknesses of the conductors, different surface areas of the conductors, different thicknesses of the insulating layers and different numbers of turns of the windings;
(b) Respectively detecting the conductivity of each analog low-voltage side winding to obtain a plurality of analog conductivities;
(c) Detecting the conductivity of the low-voltage side winding of the dry-type distribution transformer to be detected to obtain the actually measured conductivity;
(d) And comparing the actually measured electric conductivity with each analog electric conductivity, wherein the conductor material in the analog low-voltage side winding corresponding to the group with the smallest absolute difference is the material used by the conductor in the dry-type distribution transformer low-voltage side winding to be measured.
2. The nondestructive testing method for the material of the low-voltage side winding of the 10kV dry-type distribution transformer based on the eddy current according to claim 1, wherein in the step (a), the preparation method of the simulated low-voltage side winding comprises the following steps: respectively taking copper foil or aluminum foil as a conductor, stacking the conductor and DMD insulating paper, and winding n layers to obtain a winding unit with n turns; and winding m layers of DMD insulating paper on the outer surface of the winding unit to obtain the simulated low-voltage side winding.
3. The nondestructive testing method for the low-voltage side winding material of the eddy current-based 10kV dry-type distribution transformer substation according to claim 2, wherein the thickness of each layer of the conductor is 0.5-1 mm;
and/or each layer of the conductor has a surface area of 900-12100 mm 2.
4. The nondestructive testing method for the low-voltage side winding material of the 10kV dry-type distribution transformer substation based on the eddy current according to claim 2, wherein the thickness of each layer of DMD insulating paper is 0.1-0.3 mm.
5. The nondestructive testing method for the low-voltage side winding material of the 10kV dry-type distribution transformer based on the eddy current according to claim 2, wherein n=1-10;
And/or, m=1 to 10.
6. The nondestructive testing method for 10kV dry-type distribution transformer low-voltage side winding materials based on eddy current according to claim 1, wherein in the step (b) and/or the step (c), the device for testing comprises an eddy current conductivity meter.
7. The nondestructive testing method for the material of the low-voltage side winding of the 10kV dry-type distribution transformer based on the eddy current according to claim 1, wherein in the step (b) and/or the step (c), a probe of a device used for testing is placed perpendicular to the side face of the simulated low-voltage side winding in the testing process.
8. The nondestructive testing method for the low-voltage side winding material of the 10kV dry-type distribution transformer based on the eddy current according to claim 1, wherein in the step (b) and/or the step (c), the detection times are more than or equal to 5 times, and then an average value is obtained.
9. The nondestructive testing method for the material of the low-voltage side winding of the 10kV dry-type distribution transformer based on the eddy current according to claim 1, wherein in the step (c), the detection is performed on a region, which is outside the distance of 2mm, of the top end of the low-voltage side winding of the dry-type distribution transformer to be tested.
10. The use of the eddy current-based nondestructive testing method for the material of the low-voltage side winding of the 10kV dry-type distribution transformer according to any one of claims 1 to 9 for judging the material of the conductor of the low-voltage side winding of the dry-type distribution transformer.
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