RU2262690C1 - Method and device for acoustical testing of porcellaneous bearing rod insulators - Google Patents

Abstract

FIELD: analyzing or investigating materials.

SUBSTANCE: method comprises exciting free vibrations at several points on the side and flanges of the porcellaneous body, determining the spectra of the vibrations, calculating productions of the spectra of the signal from different points, and determining damping the vibration at the points tested and ratios of their maximum amplitudes in the low-frequency, mid-frequency (at the basic frequency of vibration), and high-frequency spectrum ranges. The device additionally comprises velocity pickup with linear dependence of the input signal on the vibration frequency, unit for monitoring the signal quality that allows the extraction of the optimal signal from several ones received from the points to be tested, and unit for processing information and testing.

EFFECT: enhanced reliability of testing.

4 cl, 1 dwg

Description

The invention relates to the field of electrical engineering and can be used to monitor the status of high-voltage porcelain support-rod insulators.

The reliability of porcelain support-rod insulators to date remains insufficient. Their destruction leads to accidents. In this case, injuries and human casualties are possible. Therefore, monitoring the technical condition of such insulators both before commissioning and during operation is an extremely important task.

The reliability of the insulator is determined by the quality of its porcelain body and the bond strength of the porcelain body with the flanges.

Known and recommended for use is the acoustic emission control device PAK-3M [1], developed by the All-Russian Research Institute of Electric Power (Moscow). The principle of operation of the device is based on the registration of acoustic emission signals that occur when microcracks appear in the body of the insulator during its mechanical loading (see PAK-3M acoustic emission monitoring device. Technical description and operating instructions).

This method is very labor intensive. According to the safety requirements, first it is necessary to install scaffolds on the disconnector frames, insulators must be attached to wooden racks temporarily attached to the frame to prevent them from falling in the event of a break in the test, before starting the tests, the loading device must be assembled and fixed on the upper flanges of two adjacent insulators under test. Install sensors on both insulators to receive acoustic emission signals using rubber dampers and grease to make acoustic contact.

The occurrence of acoustic emission signals as the load on the insulator increases is due to the development of germ defects (spasmodic growth of microcracks) present in porcelain, which, of course, impairs the quality of the insulator and reduces its strength.

A known method of controlling the defectiveness of the product [2] (ed. Certificate No. 2111485 dated 07/27/94), according to which the vibrations of the product are excited at one point by impact, take their own vibrations at two different points, their amplitudes are determined, and the product is judged to be defective in relation to the amplitude of oscillations at these two points.

The disadvantage of this method is that the judgment on quality only in relation to the amplitudes of the two signals is not reliable and reliable enough and can lead to erroneous conclusions. Both amplitudes can be reduced due to the presence of defects or, conversely, increased due to the reception of not only the main signal, but also reflected from the defect, for example, cracks. At the same time, their attitude will indicate the suitability of the insulator.

Another disadvantage of the method, as well as the disadvantage of the control method using the device PAK-ZM, is that both of them do not control the bond strength of the porcelain body of the insulator with its flanges.

A known method for determining the defectiveness of products [3] (author's certificate No. 1167492 of 12.01.83), according to which shock in different zones of the controlled product sequentially excite elastic vibrations, determine vibrations with maximum amplitude and determine the presence of a defect in the product from the envelope of the amplitude of this vibration. .

This method is closest to the proposed and adopted as a prototype. A significant drawback is that the evaluation of the quality of the product only by the magnitude of the amplitude of the oscillations is not reliable enough, as described above in relation to the method [2].

To overcome these shortcomings, we propose a method for monitoring the condition of porcelain support-rod insulators, including dosed shock excitation in a vibration isolator at several points, their reception and determination of spectra, characterized in that the vibrations excite at points located both on the porcelain body and on the cast iron flanges of the insulator, the products of the spectra obtained by impacts at different points are calculated, and the degree of defectiveness of the insulator is judged by the number of peaks exceeding the specified control th level in the products of the spectra at the surveyed points.

To diagnose the condition of not only the porcelain body, but also the strength of its connection with the flanges, blows are applied to the upper flange, to porcelain under the upper flange, to the lower flange and to porcelain above the lower flange. At each examined point, several blows are applied, from which the optimal one is selected according to the characteristics.

In suitable insulators, the spectra obtained after impacts at different points differ little from each other and the number of peaks in the products of the spectra exceeding the control level is small. The presence of defects in the body of the insulator and poor connection of the body with the flanges leads to a shift in the spectra, the appearance of additional frequencies and, accordingly, a sharp increase in the number of peaks in the products of the spectra exceeding the control level.

The addition of these data to the determination of the attenuation of oscillations and the ratio of their maximum amplitudes in the low-frequency, mid-frequency (at the main natural frequency of the insulator oscillations) and high-frequency spectral regions allows to increase the reliability of the control and makes it possible to determine the location of defects.

A number of devices are known for controlling products by the method of free oscillations (Glagovsky P.A., Moskovenko I. Low-frequency acoustic methods in mechanical engineering. L .: Mechanical engineering, 1977).

To excite oscillations, mechanical or piezoelectric impactors are mainly used. The amplitude spread in this case can reach 10-15%. The blow itself may be unsuccessful. To eliminate these shortcomings, the proposed device has a block for selecting the optimal signal (in terms of the amplitude of the signal and its attenuation) from several received at the surveyed point. This signal is used in further analysis.

Piezoelectric receivers or microphones are used as a signal receiver in existing devices. The former have a sharply nonlinear amplitude-frequency characteristic and have their own resonant frequencies, which can distort the results if they are close to the natural frequencies of the insulator. The microphone as a receiver for testing insulators mounted on switchgears in the field is generally not applicable.

To eliminate these drawbacks, the proposed device is equipped with a speed sensor for receiving signals with a linear dependence of the output signal on the frequency, which does not have its own resonant frequencies in the entire operating range.

To process signals, calculate parameters and evaluate the quality of insulators, the proposed device is equipped with a unit for information processing and diagnostics.

The block diagram of the device is shown in the drawing. Here 1 is a drummer, 2 is an insulator being examined, 3 is a speed sensor, 4 is an amplifier, 5 is a filter, 6 is a signal quality control unit, 7 is a spectrum analyzer, 8 is a non-volatile long-term memory unit, 9 is an information processing and diagnostic unit.

The device operates as follows. When the striker 1 strikes the tested insulator 2, mechanical vibrations occur in it, which are sensed and converted into electrical signals by the speed sensor 3. The signal is amplified by the amplifier 4 and filtered by the filter 5. At each examined point of the insulator, several strokes are applied, from the signals from which block 6 signal quality control selects the optimal signal in terms of level and minimum attenuation for further processing. The signals selected from block 6 from the surveyed points are sent to the spectrum analyzer 7 based on the fast Fourier transform algorithm.

The spectra of the signals enter the blocks of long-term memory 8 and processing diagnostic information 9. In the latter, the products of the spectra obtained at different points of the isolator are calculated, and the number of peaks in the mutual spectra is determined at a given reference level. The attenuation of oscillations at the surveyed points and the ratio of their maximum amplitudes in the low-frequency, mid-frequency (at the main natural frequency of the insulator oscillations) and high-frequency spectral regions are determined. On the basis of all these calculated and experimental data, the diagnostic unit issues a conclusion on the quality of the insulator.

Thus, the application of the proposed method of acoustic control of high-voltage porcelain support-rod insulators and a device for its implementation increases the reliability and reliability of diagnosis and allows you to determine not only the quality of the porcelain body of the insulator, but also the strength of its connection with the flanges.

Example

To implement the proposed method of acoustic control of insulators, a device was assembled in accordance with the diagram in the drawing. The tests were carried out on insulators such as ONS-110/300 of the Slavic plant of high-voltage insulators, removed from an open switchgear after operation. For testing, insulators were mounted vertically on a solid foundation (concrete floor). A speed sensor made with a point contact was installed by means of a clamp on the middle (9th) skirt of the insulator. Blows were made on the upper and lower flanges and on the body of the insulator between the upper flange and the upper skirt and between the lower flange and the lower skirt. The blows were inflicted by a mechanical hammer with a metered blow. At each examined point, three blows were inflicted, of which the device for further processing chose one optimal one.

A total of 8 isolators were examined. Survey data with numerical values of the controlled parameters are presented in the table.

Tab. No. of insulators 1 2 3 4 5 6 7 8 The number of peaks at the control level 7 3 eleven 8 16 4 6 24 7 3 8 7 47 nine 10 twenty nine 6 5 3 29th 12 6 45 Attenuation of the fundamental frequency of natural oscillations 3.6 5.7 11.0 4.1 32,7 2.9 2.7 17.3 3.2 5,4 5.9 2.0 24.0 2.2 2,4 19.7 5.5 4.9 7.6 2.6 44,2 2,8 3.4 28.1 6.0 5.2 5.5 2.9 35.0 3.6 2,8 42,4 Ratios of maximum oscillation amplitudes 1,0 1,2 1,0 0.8 1.3 1,1 0.9 1.4 1,1 1,2 1.3 1,0 1,6 1.4 1,2 8.6 1,0 1,2 1.3 1.3 2,8 1,2 1.3 1,6

According to the given data, insulators Nos. 1,2,3,4,6,7 were suitable for operation, and Nos. 5 and 8 were rejected. From the above data it follows that in insulator No. 5 there is a defect, and in insulator No. 8 there is a poor connection between porcelain and the lower flange. Indeed, upon inspection in the insulator No. 5, a crack was found under the lower skirt, and in the insulator No. 8 - partial peeling and chipping of the ligament of the lower flange with porcelain

Claims (4)

1. The method of acoustic control of porcelain support-rod insulators, including dosed shock excitation in the vibration isolator, receiving natural vibrations and determining the vibration spectrum, characterized in that the vibrations excite at several points located both on the porcelain body and on the insulator flanges, are calculated products of spectra obtained from impacts at different points, and the degree of defectiveness of an insulator is judged by the number of peaks exceeding a given reference level in the products of spectra in edovannyh points. 2. The method according to claim 1, characterized in that it further determines the damping of the oscillations at the surveyed points and the ratio of their maximum amplitudes in the low-frequency, mid-frequency (at the main natural frequency of the oscillator insulator) and high-frequency spectral regions. 3. The method according to claim 1, characterized in that the blows are applied to the upper flange, to the porcelain under the upper flange, to the porcelain above the lower flange and the lower flange, and the signal receiver is placed on one of the middle skirts of the insulator. 4. An acoustic control device for porcelain support-rod insulators, containing a drummer for exciting free mechanical vibrations, an amplifier, a filter, a spectrum analyzer, characterized in that a speed sensor with a linear dependence of the output signal on the oscillation frequency, which is made with the ability to convert mechanical vibrations into electrical signals transmitted sequentially through an amplifier and a filter into a quality control unit made with zmozhnostyu selecting and transmitting optimal level and minimum attenuation of the signal in the spectrum analyzer, associated with the block of non-volatile memory and an information processing unit and for calculating diagnostic product spectra obtained at different points of the insulator.