RU2735627C1 - Method of determining degree of polymerisation of transformer paper insulation - Google Patents

Abstract

FIELD: physics.SUBSTANCE: method of determining quality of paper insulation consists in determining degree of polymerisation (DP) using reflection coefficients of radiation of paper insulation. Position of the maximum in the spectrum of the reflection coefficient of radiation of paper insulation in the wavelength range of 400÷800 nm is determined for paper insulation with different values of DP and the DP are determined from the obtained DP relationship from the position of the maxima in the spectrum of the radiation reflection coefficient of paper insulation.EFFECT: technical result is providing nondestructive quality control of paper insulation of a transformer with a wide range of measured values and high accuracy of measuring DP.1 cl, 3 dwg

Description

The invention relates to a technique for diagnosing oil-filled electrical equipment, in particular, to quality control of oil-paper insulation of a transformer.

Known chemical method for determining the degree of polymerization (DP), which consists in determining the intrinsic viscosity of cellulose using a solution of cadmium ethylenediamine complex (cadoxen) on the basis of which the DP is calculated. However, using this method leads to damage to the paper insulation of the transformer. This method is laborious and requires preparation of a cadoxen solution, sampling of insulation, and determination of intrinsic viscosity [1].

There is also known a method for monitoring the quality of paper insulation of a transformer, which consists in establishing the correlation dependence of the chromaticity coordinates x and y on its SP. Determining the chromaticity coordinates x and y of cellulose insulation, determine SP [2].

The disadvantage of this method is the small dynamic range of the measured values of the chromaticity coordinates and the accuracy of determining the SP.

There is also known a method for monitoring the technical condition of high-voltage oil-filled electric power equipment, which consists in determining the DP using a calibration graph of the dependence of the DP on the reflection coefficient of radiation at a wavelength of 1742 cm ^-1 [3].

The disadvantage of this method is the use of the far infrared range, the practical implementation of which is difficult to implement on transformer equipment.

The closest to the claimed method in terms of the maximum number of similar features is the method for determining the DP using a calibration graph of the dependence of the DP on the reflection coefficients of the radiation of paper insulation at wavelengths in the visible range of the spectrum 650 ÷ 655 nm [4].

The disadvantage of this method is the narrow range of the measured values of the reflection coefficients and the accuracy of determining the DP, since the absolute values of the reflection coefficients are measured, which depend on the characteristics of the transformer oil.

The basis of the invention is the problem of creating a method for non-destructive quality control of paper insulation of a transformer with a wide range of measured values and increased measurement accuracy of SP.

The technical result is achieved by the fact that in the method of non-destructive quality control of paper insulation of a transformer, according to which the quality is assessed by analyzing a set of properties using non-destructive testing methods, and the quality indicator is calculated depending on the position of the maximum in the reflection spectrum of paper insulation in the wavelength range of 400 h 800 nm. The position of the maximum in the reflection spectrum does not depend on the transformer oil impregnating it, since it is a relative value.

The use of the non-destructive testing method makes it possible to measure the reflection coefficient in a wide range, which will improve the accuracy of the method.

Determination of the SP depending on the reflection coefficient of the paper insulation of the transformer at wavelengths of 400 ÷ 800 nm in the visible region of the spectrum makes it possible to automate the calculations. This is achieved through the use of special algorithms.

The essence of the invention is illustrated in Fig. 1.

Figure 1 shows a diagram of a device for implementing a method for monitoring the quality of paper insulation of a transformer, where, 1 - transformer housing, 2 - transformer winding, 3 - fiber-optic cables, 4 - radiation source, 5 - radiation receiver.

The way to control the quality of paper insulation of a transformer is as follows.

Fiber-optic cables 3 are fed to the upper part of the winding of the transformer 2, one of which is designed to illuminate a section of paper insulation using a radiation source 4, the other for transferring reflected radiation from the paper insulation to the receiver 5, which records the reflected radiation.

Determination of the reflection coefficient of radiation from paper insulation at certain wavelengths was used as a method of non-destructive testing. To control the quality of paper insulation, wavelengths of 400 ÷ 800 nm are used, at which the reflection coefficient R _{400 ÷ 800} is determined. The value of R _{400 ÷ 800} is defined as the ratio of the values of the radiation intensity from the radiation source 4 - I _{IZL400 ÷ 800} and the intensity of the reflected radiation from the paper insulation of the transformer I _{OTR400 ÷ 800} .

FIG. 2 shows the dependences of the reflection coefficients of transformer paper with different values of SP.

The position of the maxima in the reflectance spectrum depends only on the SP of the paper and is shown in Fig. 3, where SP is determined by the function SP = f ( R _{400 ÷ 800} ).

Substituting the value of R _{400 ÷ 800} into the established function SP = f ( R _{400 ÷ 800} ), we determine the SP of the cellulose insulation of the transformer.

The use of the proposed method does not require large material costs, and its implementation is easy to operate, since it uses the reflection wavelength in the visible region of the spectrum, which significantly reduces the cost of practical implementation of the method.

Bibliographic list

1. GOST 25438-82 Cellulose for chemical processing. Methods for determining intrinsic viscosity. USSR State Committee for Standards. Moscow.

2. RU 2392684, cl. H 01 F 41/12, 2010.

3. RU 2420822 cl. H 01 F 41/12, 2011.

4. RU 2535874 cl. H01F 41/00 2013.

Claims (1)

A method for determining the quality of paper insulation, which consists in determining the degree of polymerization (DP) using the reflection coefficients of the radiation of paper insulation, characterized in that the position of the maximum in the spectrum of the reflectance of the radiation of paper insulation in the wavelength range of 400-800 nm for paper insulation with different values is determined SP and determine SP according to the obtained dependence of SP on the position of the maxima in the spectrum of the reflection coefficient of radiation of paper insulation.

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