CN-122016780-A - Method for judging acid value titration end point of electric power oil based on color titration method

Abstract

The invention relates to the technical field of oil chemical analysis, and particularly discloses a method for judging an acid value titration end point of electric power oil based on a color titration method. According to the invention, the spectrum color sensor is used for collecting the data of the change of the solution color depth value along with time in the titration process, the color titration curve is fitted by using a high-order polynomial, the curvature of the fitted curve is calculated point by point, and the curvature peak point with the curvature value of 0.2-2 appearing for the first time is used as the titration end point. The invention overcomes the defects of strong subjectivity, easy pollution of the electrode, easy occurrence of no potential jump and the like of the traditional indicator titration method, simultaneously avoids the adverse effect of the colors of different oil samples on the RGB value of the titration end point when the existing color titration method judges the end point by the RGB value of the color, has objective and accurate titration end point judgment and excellent repeatability, and is suitable for the acid value measurement of the electric oil. The method is simple and convenient to operate, economical, environment-friendly, efficient and accurate, and has higher popularization and application values.

Inventors

• SHI RONGXUE
• LIU KECHENG
• YU JINXING
• LIU SIQI
• ZHANG SHENGHAN
• YAN NING
• FAN RUIMIN

Assignees

• 国网河北能源技术服务有限公司
• 国家电网有限公司

Dates

Publication Date

20260512

Application Date

20251219

Claims (10)

1. 1. The method for judging the acid value titration end point of the electric power oil based on the color titration method is characterized by comprising the following steps of: Weighing an oil sample in a reaction container provided with a spectrum color sensor, adding an alcohol solvent, an indicator and a titrant, performing acid value titration, recording time-varying data of a color depth value, and drawing a color titration curve; And fitting the color titration curve by using a high-order polynomial, calculating the curvature of the fitted curve point by point, and taking the curvature peak point with the first occurrence curvature value within the range of 0.2-2 as the titration end point.
2. 2. The method for determining an acid value titration endpoint of an electrical oil based on a color titration method according to claim 1, wherein the oil sample comprises transformer oil or turbine oil.
3. 3. The method for determining an acid value titration endpoint of an electrical oil based on a color titration method according to claim 1, wherein the alcohol solvent comprises ethanol or isopropanol, and the indicator comprises bromothymol blue solution.
4. 4. The method for determining an acid value titration endpoint of an electric oil based on a color titration method according to claim 1 or 3, wherein the mass volume ratio of the oil sample, the alcohol solvent and the indicator is (8-10) g (50-60) mL (0.15-0.25) mL.
5. 5. The method for determining an acid value titration endpoint of electric power oil based on a color titration method according to claim 1, wherein the titrant comprises a potassium hydroxide ethanol standard solution, and the concentration of potassium hydroxide in the titrant is 0.03 mol/L-0.05 mol/L.
6. 6. The method for determining an acid value titration end point of electric power oil based on a color titration method according to claim 1, wherein the temperature of the acid value titration is 75 ℃ to 85 ℃.
7. 7. The method for determining an acid value titration endpoint of an electrical oil based on a color titration method according to claim 1, wherein the higher order polynomial comprises a sixth order polynomial having a general formula shown in formula 1: y=b+a 1 ×x+a 2 ×x 2 +a 3 ×x 3 +a 4 ×x 4 +a 5 ×x 5 +a 6 ×x 6 1 (1) In formula 1, x represents time in s, y represents a color depth value, and is dimensionless, b represents an intercept on a y axis, and a 1 、a 2 、a 3 、a 4 、a 5 and a 6 represent fitting coefficients, respectively.
8. 8. The method for determining an acid value titration end point of power oil based on a color titration method according to claim 1, wherein fitting is started from the time when the color titration curve reaches 3 data points, and curvature of a fitted curve is calculated.
9. 9. The method for determining an acid value titration end point of an electrical oil according to claim 1, wherein the step of obtaining the titration end point further comprises calculating an acid value from a volume of the titrant corresponding to the titration end point.
10. 10. The method for determining an acid value titration endpoint of an electrical oil based on a color titration method according to claim 9, wherein the calculation formula of the acid value is shown in formula 2: Acid value = [ (V 1 -V 0 ) ×c×56.1]/M 2, 2 In the formula 2, the components are mixed, V 1 is the volume of titrant consumed by the titration oil sample, in mL; v 0 is the volume of titrant consumed in the blank test in mL; c is the concentration of the titrant, and the unit is mol/L; 56.1 is the molar mass of potassium hydroxide in g/mol; m is the mass of the oil sample, and the unit is g.

Description

Method for judging acid value titration end point of electric power oil based on color titration method Technical Field The invention relates to the technical field of oil chemical analysis, in particular to a method for judging an acid value titration end point of electric power oil based on a color titration method. Background The acidic components in the operating transformer oil or turbine oil are mainly partial oxidation products generated after the oxidation of the oil, such as naphthenic acid, phenols, fatty acids and the like. If these acidic substances are not removed in time, equipment and parts contacting with oil products can be corroded, the service life of the equipment and parts is shortened, and serious accidents can be caused. The acid value is used for judging the content of acid products in the oil product and the automatic oxidation trend of the oil product. Therefore, the acid value of the electric oil must be measured both in the acceptance of new oil and in the regular supervision of operating oil. In the existing acid value measurement technology of the electric power oil, an indicator titration method and an automatic potentiometric titration method are widely applied, but the two methods have certain defects. The indicator titration method is limited in application range, is only suitable for measuring the acid value of light-colored oil products, cannot be measured for some oil products with darker colors or slow titration endpoint change, and is mainly judged manually in the color change in the test process, so that subjectivity is high, different testers can possibly give different judgment results, and reproducibility is poor. The electrode used in the automatic potentiometric titration method is easy to be polluted, the maintenance process is complex, the influence factors (solvent flushing, electrode activation, isopropanol immersion and the like) are numerous, and the problem of no obvious titration jump easily occurs during measurement. Currently, color titration of acid values of oil products generally uses a determined RGB value as a titration endpoint. However, since the colors of the original oil samples are greatly different, it is actually difficult to determine the RGB values of the end point colors in advance. Therefore, it is needed to develop a new technology for measuring the acid value of the electric oil based on the color derivative sensing technology, so as to overcome the limitations that the RGB value of the solution color is not easy to determine, the color change of the end point is not obvious, and the automatic potentiometric titration method is easy to have no potential jump and the like when the titration end point needs to be set in advance by the indicator titration method. Disclosure of Invention In view of the above problems, the present invention provides a method for determining an acid value titration endpoint of electric power oil based on a color titration method, which does not need to determine RGB values of endpoint colors in advance, can significantly improve objectivity and accuracy of determining the titration endpoint, and can efficiently and accurately detect the acid value of the electric power oil. In order to solve the technical problems, the technical scheme provided by the invention is as follows: a method for judging an acid value titration end point of electric power oil based on a color titration method comprises the following steps: Weighing an oil sample in a reaction container provided with a spectrum color sensor, adding an alcohol solvent, an indicator and a titrant, performing acid value titration, recording time-varying data of a color depth value, and drawing a color titration curve; And fitting the color titration curve by using a high-order polynomial, calculating the curvature of the fitted curve point by point, and taking the curvature peak point with the first occurrence curvature value within the range of 0.2-2 as the titration end point. Compared with the prior art, the method for judging the acid value titration end point of the electric power oil based on the color titration method is characterized in that the spectrum color sensor is used for collecting data of the change of the solution color depth value along with time in the titration process, a color titration curve is fitted by using a high-order polynomial, the curvature of the fitted curve is calculated point by point, and the curvature peak point with the first occurrence curvature value within the range of 0.2-2 is used as the titration end point. The invention overcomes the defects of strong subjectivity, easy pollution of the electrode, easy occurrence of no potential jump and the like of the traditional indicator titration method, simultaneously avoids the adverse effect of the colors of different oil samples on the RGB value of the titration endpoint when the existing color titration method judges the endpoint by the RGB value, has the advantages