阅读说明：本技术 一种油浸式电力变压器腐蚀程度的评估方法 (Method for evaluating corrosion degree of oil-immersed power transformer ) 是由 何智杰 傅炜婷 黄鹏 曾建敏 黄昭云 洪文斌 颜城 郑哲艺 林燕桢 林瑞聪 洪君 于 2021-09-15 设计创作，主要内容包括：本发明涉及一种油浸式电力变压器腐蚀程度的评估方法,包括测定绝缘纸中铜元素含量和铝元素含量；计算绝缘纸的腐蚀程度c1；测定绝缘油中铜元素含量、铝元素含量、水分含量和酸值；计算绝缘油的腐蚀程度c2；电力变压器腐蚀程度的综合评估步骤。该评估方法基于绝缘纸和绝缘油相关指标参数去对电力变压器腐蚀情况进行评估,更为全面以及具有较高的精准度。(The invention relates to an assessment method of corrosion degree of an oil-immersed power transformer, which comprises the steps of measuring the content of copper element and the content of aluminum element in insulating paper; calculating the corrosion degree c1 of the insulating paper; measuring the content of copper element, the content of aluminum element, the content of water and the acid value in the insulating oil; calculating the corrosion degree c2 of the insulating oil; and comprehensively evaluating the corrosion degree of the power transformer. The evaluation method is used for evaluating the corrosion condition of the power transformer based on the relevant index parameters of the insulating paper and the insulating oil, and is more comprehensive and has higher accuracy.)

1. An assessment method for corrosion degree of an oil-immersed power transformer is characterized by comprising the following steps:

s1: and (3) determining the content of copper and aluminum in the insulating paper:

sampling insulation paper of a power transformer to be evaluated, and testing the content PCu and the content PAl of aluminum element in the insulation paper, wherein PCu and PAl are percentages;

s2: calculating the corrosion degree c1 of the insulating paper:

and (3) calculating the corrosion degree c1 of the insulating paper, wherein the calculation formula is as follows:

s3: determining the content of copper element, the content of aluminum element, the content of water and the acid value in the insulating oil:

sampling insulating oil of a power transformer to be evaluated, and testing to obtain the copper element content OCu and the aluminum element content OAl in the insulating oil, wherein both OCu and OAl are percentages;

testing to obtain the water content Ow in the insulating oil, wherein the unit is ppm;

testing to obtain the acid value Oa in the insulating oil, wherein the unit is mgKOH/g;

s4: calculating the corrosion degree c2 of the insulating oil:

firstly, the corrosion degree a1 is calculated according to the copper element content OCu and the aluminum element content OAl in the insulating oil, and the calculation formula is as follows:

a₁＝0.6×OCu×64+0.4×OAl×27

and then calculating the corrosion degree a2 according to the moisture content Ow in the insulating oil, wherein the calculation formula is as follows:

then, the degree of corrosion a3 was calculated from the acid value Oa in the insulating oil, and the calculation formula was as follows:

a₃＝λ×|lgOa|²

wherein, λ is temperature coefficient, and λ is 0.95 when the external environment temperature is below 15 ℃ on average; when the temperature of the external environment is averagely 15-25 ℃, the lambda value is 1; when the temperature of the external environment is averagely above 25 ℃, the lambda value is 1.05;

finally, the corrosion degree c2 of the insulating oil is obtained, and the calculation formula is as follows:

s5: comprehensive evaluation of corrosion degree of the power transformer:

calculating the corrosion degree c of the power transformer according to the corrosion degree c1 of the insulating paper and the corrosion degree c2 of the insulating oil, wherein the calculation formula is as follows:

when c is less than or equal to 7, the corrosion degree of the power transformer is low, namely the corrosion condition of the power transformer is not serious; when c is more than 7 and less than or equal to 9, the corrosion degree of the power transformer is moderate, namely the corrosion condition of the power transformer is general; when c is larger than 9, the corrosion degree of the power transformer is higher, namely the corrosion condition of the power transformer is more serious.

2. The method for evaluating the corrosion degree of an oil-filled power transformer according to claim 1, wherein the method comprises the following steps: step S1, specifically, a scanning electron microscope energy spectrometer is used for testing the copper element content PCu in the insulating paper, and a scanning electron microscope energy spectrometer is used for testing the aluminum element content PAl in the insulating paper.

3. The method for evaluating the corrosion degree of an oil-filled power transformer according to claim 1, wherein the method comprises the following steps: step S3, specifically, the content of copper element OCu in the insulating oil is obtained through an inductively coupled ion emission spectrometry test, and the content of aluminum element OAl in the insulating oil is obtained through the inductively coupled ion emission spectrometry test.

4. The method for evaluating the corrosion degree of an oil-filled power transformer according to claim 1, wherein the method comprises the following steps: the insulation paper sampled in step S1 is insulation paper for the transformer body winding.

5. The method for evaluating the corrosion degree of an oil-filled power transformer according to claim 1, wherein the method comprises the following steps: the insulating oil sampled in step S3 is the insulating oil of the transformer tank.

Technical Field

The invention relates to the technical field of performance evaluation of power transformers, in particular to an evaluation method for corrosion degree of an oil-immersed power transformer.

Background

Electric power has been an important production power and has long been an indispensable energy source in people's life. With the continuous increase of the scale and complexity of the Chinese power grid, it becomes increasingly difficult to ensure the safe and reliable operation of the power grid and avoid large-scale power failure. Therefore, safe operation of the power grid is particularly important to ensure the safety of electricity utilization for people and to meet the electricity utilization requirements of society. The power transformer is used as a core device for safe and stable operation of a power grid, and in long-term operation, the electrical performance of the power transformer is reduced due to a product generated by reaction of corrosive sulfide and metal in transformer insulating oil, insulation safety is damaged, and stable operation of the power grid is influenced.

The existing insulation aging evaluation of transformers obtains the degree of corrosion of oil-filled power transformers mainly by evaluating the degree of polymerization of insulation paper and measuring the content of aging byproducts of insulation paper, such as carbon-oxygen gas, furfural, and low-molecular alcohols. In the prior art, the evaluation is not accurate enough, and a large error exists, so that an evaluation method for the corrosion degree of the power transformer is needed to effectively and comprehensively evaluate the power transformer, discover the electrical performance defect of the power transformer in time, and provide guarantee for the safe operation of the power transformer.

In the existing research, for example, a quantitative characterization method for sulfur corrosion degree of transformer oil based on copper weight loss indicates that corrosive sulfur in transformer oil reacts with a copper winding to generate cuprous sulfide attached to the surface of insulating paper, so that the electrical performance of the insulating paper is reduced to cause a fault, in pages 75-81, a fancy, li qingmin, haoxi, zhanhao hao, doliche and an insulating material are disclosed. The weight loss quality of copper has good correlation with the concentration of corrosive sulfur in transformer oil, the higher the concentration of the corrosive sulfur in the oil is, the larger the weight loss quality of the copper sheet is, and the method can accurately detect the sulfur corrosion degree of the transformer oil in actual operation. The copper sheet mainly generates oxidation reaction and sulfur corrosion reaction, and based on the mass conservation law, the mass loss of the copper sheet caused by the sulfur corrosion reaction can be obtained, so that the quantitative characterization of the sulfur corrosion degree of the transformer oil is realized.

In addition, for example, "the phenomenon of corrosion of aluminum foil in a bushing by oil and sulfur and a test on the influence of the phenomenon on the insulation performance of oil paper are studied", item-based, Yuan, how-free, Zhangling, Liaorui, a high-voltage electricity technology, volume 45, phase 2, pages 484 to 491, and in 2019, day 2, month 28, it is indicated that the insulation structure of the oil-immersed bushing is different from the insulation of the oil paper of a transformer, and the outer part of the copper core is alternately wrapped by the metal aluminum foil and the insulation paper to form a cylindrical capacitor screen. The aluminum foil has stronger metal activity than copper, and the existence of the aluminum foil probably has great influence on the change of the insulating property of the sleeve under various aging factors. In addition, the casing has small volume, less oil mass, closed structure, high and concentrated electric field intensity, and compared with the insulating structure of the transformer, the special oil paper insulating structure of the casing is more easily affected by oil sulfur corrosion, thereby bringing more serious harm. The aluminum foil in the structure of the oil-paper-aluminum foil has corrosion phenomena under the condition of certain acid value and sulfur content of insulating oil, the corrosion is intensified by the existence of DBDS, and the corrosion degree of the aluminum foil can be judged by testing the content of aluminum element in the oil.

Disclosure of Invention

In order to solve the above problems, an object of the present invention is to provide an evaluation method for corrosion degree of an oil-immersed power transformer, the evaluation method is based on index parameters related to insulation paper and insulation oil to evaluate corrosion condition of the power transformer, and the evaluation method is more comprehensive and has higher accuracy.

In order to achieve the purpose, the invention adopts the following technical scheme:

an assessment method for corrosion degree of an oil-immersed power transformer comprises the following steps:

s1: and (3) determining the content of copper and aluminum in the insulating paper:

sampling insulation paper of a power transformer to be evaluated, and testing the content PCu and the content PAl of aluminum element in the insulation paper, wherein PCu and PAl are percentages;

s2: calculating the corrosion degree c1 of the insulating paper:

and (3) calculating the corrosion degree c1 of the insulating paper, wherein the calculation formula is as follows:

s3: determining the content of copper element, the content of aluminum element, the content of water and the acid value in the insulating oil:

sampling insulating oil of a power transformer to be evaluated, and testing to obtain the copper element content OCu and the aluminum element content OAl in the insulating oil, wherein both OCu and OAl are percentages;

testing to obtain the water content Ow in the insulating oil, wherein the unit is ppm;

testing to obtain the acid value Oa in the insulating oil, wherein the unit is mgKOH/g;

s4: calculating the corrosion degree c2 of the insulating oil:

firstly, the corrosion degree a1 is calculated according to the copper element content OCu and the aluminum element content OAl in the insulating oil, and the calculation formula is as follows:

a₁＝0.6×OCu×64+0.4×OAl×27

and then calculating the corrosion degree a2 according to the moisture content Ow in the insulating oil, wherein the calculation formula is as follows:

then, the degree of corrosion a3 was calculated from the acid value Oa in the insulating oil, and the calculation formula was as follows:

a₃＝λ×|lgOa|²

wherein, λ is temperature coefficient, and λ is 0.95 when the external environment temperature is below 15 ℃ on average; when the temperature of the external environment is averagely 15-25 ℃, the lambda value is 1; when the temperature of the external environment is averagely above 25 ℃, the lambda value is 1.05;

finally, the corrosion degree c2 of the insulating oil is obtained, and the calculation formula is as follows:

s5: comprehensive evaluation of corrosion degree of the power transformer:

calculating the corrosion degree c of the power transformer according to the corrosion degree c1 of the insulating paper and the corrosion degree c2 of the insulating oil, wherein the calculation formula is as follows:

when c is less than or equal to 7, the corrosion degree of the power transformer is low, namely the corrosion condition of the power transformer is not serious; when c is more than 7 and less than or equal to 9, the corrosion degree of the power transformer is moderate, namely the corrosion condition of the power transformer is general; when c is larger than 9, the corrosion degree of the power transformer is higher, namely the corrosion condition of the power transformer is more serious.

In step S1, a scanning electron microscope spectrometer is specifically used to test the copper element content PCu in the insulating paper, and a scanning electron microscope spectrometer is used to test the aluminum element content PAl in the insulating paper.

In the step S3, specifically, an inductively coupled ion emission spectrometry is adopted to test to obtain the copper element content OCu in the insulating oil; and testing by adopting an inductively coupled ion emission spectrometry to obtain the content OAl of the aluminum element in the insulating oil.

The insulation paper sampled in step S1 is insulation paper for the transformer body winding.

The insulating oil sampled in step S3 is the insulating oil of the transformer tank.

The invention has the following beneficial effects:

the method for evaluating the corrosion degree of the oil-immersed power transformer can visually and comprehensively evaluate the corrosion degree of the oil-immersed power transformer.

Drawings

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

Detailed Description

The invention is described in further detail below with reference to the following figures and specific examples:

referring to fig. 1, a method for evaluating corrosion degree of an oil-immersed power transformer includes the following steps:

s1: and (3) determining the content of copper and aluminum in the insulating paper:

sampling insulation paper of a power transformer to be evaluated, wherein the insulation paper to be sampled is insulation paper of a transformer body winding, testing the copper element content PCu in the insulation paper by adopting a scanning electron microscope energy spectrometer, and testing the aluminum element content PAl in the insulation paper by adopting the scanning electron microscope energy spectrometer, wherein PCu and PAl are percentages;

s2: calculating the corrosion degree c1 of the insulating paper:

and (3) calculating the corrosion degree c1 of the insulating paper, wherein the calculation formula is as follows:

where 64 is the relative atomic mass of copper and 27 is the relative atomic mass of aluminum;

wherein PCu is the content PCu of copper element in the sampling insulation paper; PAl is the aluminum content in the sampled insulation paper.

S3: determining the content of copper element, the content of aluminum element, the content of water and the acid value in the insulating oil:

s3-1: sampling insulating oil of a power transformer to be evaluated, wherein the sampled insulating oil is the insulating oil of a transformer oil tank, and testing by adopting an inductively coupled ion emission spectrometry to obtain the copper element content OCu in the insulating oil, wherein OCu is percentage;

s3-2: testing by adopting an inductively coupled ion emission spectrometry to obtain the content OAl of the aluminum element in the insulating oil, wherein the OAl is percentage;

s3-3: testing the moisture content Ow in the insulating oil by using a Karl Fischer moisture tester, a Mettler electronic balance, a vibration table, a test tube, a vacuum drying oven and the like, wherein the unit of the moisture content Ow is ppm;

the specific steps of using a Karl Fischer moisture tester, a Mettler electronic balance, a vibration table, a test tube, a vacuum drying oven and the like to test and obtain the moisture content Ow in the insulating oil are as follows:

(1) test apparatus

The equipment used for the test of the moisture content in the oil comprises a Karl Fischer moisture tester, a high-precision weighing Mettler electronic balance, a vibration table for stirring the moisture in the oil, a test tube and a vacuum drying oven for drying the test tube.

(2) Moisture content testing procedure

Firstly, connecting an instrument power line according to an instrument specification and debugging the instrument. Before using each test tube and syringe, it was dried in a vacuum oven at 115. + -. 5 ℃ for 16 to 24 hours. Cooled in a desiccator and stored in the desiccator until needed.

And connecting the electrode lead to the designated position of the coulometric analyzer. The electromagnetic stirrer was turned on to start the electrolysis of the residual moisture present. If the electrolyte is over-iodine, injecting a proper amount of water-containing methanol or pure water, wherein the color of the electrolyte gradually becomes light, and finally the electrolyte is yellow for electrolysis.

Thirdly, when the electrolyte reaches the end point, selecting proper delay time, preferably 50s, pressing down a start button, measuring 0.1 mul of distilled water or desalted water (or standard sample with known water content) by using a 0.5 mul injector, and injecting the distilled water or desalted water into the electrolytic cell through a sample inlet at the upper part of the electrolytic cell for correction. The relative error between the milli-base number and the theoretical value should not exceed + -5%, and the current compensator should be adjusted if the relative error exceeds the range. When the required value is reached by continuously feeding 0.1 mul of water for three times, the instrument can be considered to be adjusted.

And fourthly, after the instrument is adjusted to be balanced, the dry injector is used for taking test oil. The syringe is filled with an insulating oil liquid to keep the needle tip below the liquid surface. After the oil is taken out, the syringe is vertically placed, the needle head is upward, and all air bubbles in the syringe are discharged. The liquid in the syringe is discharged and the syringe is refilled. About 2ml of sample was then discharged using the syringe to flush the needle and the syringe was initially weight-weighed using an electronic balance.

Controlling the apparatus to start electrolysis according to the manufacturer's instructions, and quickly injecting a proper amount of sample into the titration container. The needle tip is not allowed to contact the reagent surface. The syringe weight was then weighed again and the mass of the injected sample recorded as M (grams). A vibrating table was used to ensure that the oil was well mixed with the solvent. And the rotating speed of the stirrer cannot be changed after the instrument is self-balanced or in the titration process.

Sixthly, after the titration is finished, the weight m (microgram) of the water content measured by titration is read out from a display. And repeating the measurement, repeating the operation for at least two times in the same test, and taking an average value.

In the formula: m is the water titration amount in micrograms (μ g);

m is the mass of the insulating liquid in grams (g);

ppm is parts per million, which means that the mass of solute is one million of the mass of the whole solution, and 1ppm is 1 mug/g.

S3-4: testing the acid value Oa in the insulating oil by using a conical flask, a spheroid reflux condenser tube, a micro-burette, a water bath device and the like, wherein the unit of the acid value Oa is mgKOH/g;

the specific steps for testing the acid value Oa of the insulating oil by using a conical flask, a spheroid reflux condenser tube, a micro-burette, a water bath device and the like are as follows:

(1) test apparatus and reagent

The acid value is an indication of the amount of acidic substances contained in the oil, and the number of milligrams of potassium hydroxide required to neutralize the acidic substances in 1g of the oil is referred to as the acid value (mgKOH/g).

The test instrument: conical flask, ball star reflux condenser tube, micro-burette and water bath

Test reagents: potassium hydroxide, 95% ethanol, basic blue 6B, cresol red and dilute hydrochloric acid

(2) Test flow

Firstly, weighing 8-10 g of a sample by using a clean and dry conical flask, and weighing the sample to 0.2 g.

② adding 50 ml of 95 percent ethanol into another clean anhydrous conical flask, installing a reflux condenser tube, boiling the ethanol for 5 minutes under continuous shaking, and removing the carbon dioxide dissolved in the 95 percent ethanol.

0.5 ml of basic blue 6B was added to the boiling ethanol and neutralized with 0.05N ethanolic potassium hydroxide while hot until the solution changed from blue to light red (or yellow to mauve). For the sample which is not neutralized and has a light red color, if the sample is to be used for measuring the acid value, 0.05N diluted hydrochloric acid is used for a plurality of drops to neutralize the ethanol to be just slightly acidic, and then the solution is neutralized by the steps until the solution is changed from blue to light red (or from yellow to purple).

Thirdly, the neutralized 95 percent ethanol is injected into a conical flask filled with weighed sample, and a reflux condenser tube is arranged. The solution was boiled for 5 minutes with constant shaking.

To the boiled mixture, 0.5 ml of basic blue 6B was added, and the mixture was neutralized with 0.05N ethanol potassium hydroxide while hot until the solution changed from blue to light red (or from yellow to purplish red).

For samples that did not appear reddish at the end of titration, titration was allowed to reach the end point when the border of the mixture started to change significantly from color.

The time elapsed from the cessation of heating of the erlenmeyer flask to the end of the titration should not exceed 3 minutes in each titration.

(3) Calculating the neutralization acid value in the insulating oil

The acid number X of the sample was calculated as follows:

T＝56.1N

in the formula:

v-titration is the volume of potassium hydroxide ethanol solution consumed, in milliliters;

g is the weight of the sample, G;

t-titer of potassium hydroxide ethanol solution, mg KOH/ml;

56.1 gram equivalents to potassium hydroxide;

n-equivalent concentration of Potassium hydroxide ethanol solution, N.

S4: calculating the corrosion degree c2 of the insulating oil:

firstly, the corrosion degree a1 is calculated according to the copper element content OCu and the aluminum element content OAl in the insulating oil, and the calculation formula is as follows:

a₁＝0.6×OCu×64+0.4×OAl×27

where 64 is the relative atomic mass of copper and 27 is the relative atomic mass of aluminum;

wherein OCu is the content of copper element in the sampled insulating oil; OAl is the content of aluminum element in the sampled insulating oil.

And then calculating the corrosion degree a2 according to the moisture content Ow in the insulating oil, wherein the calculation formula is as follows:

then, the degree of corrosion a3 was calculated from the acid value Oa in the insulating oil, and the calculation formula was as follows:

a₃＝λ×|lgOa|²

wherein, λ is temperature coefficient, and λ is 0.95 when the external environment temperature is below 15 ℃ on average; when the temperature of the external environment is averagely 15-25 ℃, the lambda value is 1; when the temperature of the external environment is averagely above 25 ℃, the lambda value is 1.05;

finally, the corrosion degree c2 of the insulating oil is obtained, and the calculation formula is as follows:

s5: comprehensive evaluation of corrosion degree of the power transformer:

calculating the corrosion degree c of the power transformer according to the corrosion degree c1 of the insulating paper and the corrosion degree c2 of the insulating oil, wherein the calculation formula is as follows:

when c is less than or equal to 7, the corrosion degree of the power transformer is low, namely the corrosion condition of the power transformer is not serious; when c is more than 7 and less than or equal to 9, the corrosion degree of the power transformer is moderate, namely the corrosion condition of the power transformer is general; when c is larger than 9, the corrosion degree of the power transformer is higher, namely the corrosion condition of the power transformer is more serious.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent structural changes made by using the contents of the present specification and the drawings, or applied directly or indirectly to other related technical fields, are included in the scope of the present invention.