CN111912460A - Acousto-optic combined device for on-line monitoring of electric branches - Google Patents

Abstract

The acousto-optic combination device for on-line monitoring of electrical tree branches provided by the invention belongs to the technical field of insulation material detection. It includes a signal source, a high-voltage amplifying module, an observation module, an acoustic measurement module and a data acquisition and processing module; the signal source is connected with the high-voltage amplifying module, and the high-voltage amplifying module is connected with a needle electrode, which is embedded in the measured dielectric and is The bottom of the measured dielectric is coated with conductive paint and connected with a ground electrode, the observation module is set near the measured dielectric, the acoustic measurement module is attached to the surface of the measured dielectric, and both the observation module and the acoustic measurement module are connected to the data acquisition and processing module. The acousto-optic combination device for on-line monitoring of electrical tree branches of the present invention monitors and analyzes materials in combination with optical equipment and acoustic equipment, which makes up for the limitation that single acoustic detection can only measure dynamic characteristics and optical detection is limited by the degree of light transmittance of materials. Solid insulating materials have potential application prospects for detecting the growth process of electrical tree branches.

Description

Acoustic-optical combined device for on-line monitoring of electrical tree branches

technical field

The invention belongs to the technical field of insulation material detection, and in particular relates to an acousto-optic combined device for online monitoring of electrical trees.

Background technique

Solid dielectrics are insulating materials that play a very important role in electrical insulation systems. An important and remarkable phenomenon in the aging process of solid dielectrics is the emergence and development of electrical tree branches. The generation and growth of electric branches is a gradual process. Generally, due to defects, bubbles, etc., the nearby electric field is distorted and the field strength is concentrated, which further causes the decomposition and destruction of the nearby insulating materials, and develops in a radial and dendritic shape, which eventually leads to the breakdown of the solid dielectric and the insulation failure. The whole process involves complex electrodynamic and electrochemical processes. Studies have shown that the generation and development of electrical tree branches are affected by various factors, such as the frequency and amplitude of voltage, external mechanical stress, defects inside the material, temperature and so on. The current research mainly focuses on the recording and analysis of optical or electrical signals during the growth and development of electrical tree branches. For example, using a microscope to observe the geometric properties of the electrical tree and its evolution or to analyze the aging process by measuring the amount of partial discharge. The advantage of optical analysis is that the growth and development of electrical branches can be observed intuitively and conveniently. However, this kind of measurement has high requirements on the transparency of the sample, and the sight line is easily affected by the surface and internal bubbles and impurities of the material. In the process of the generation and development of electrical branches, along with the deformation and internal cracking of the material, the phenomenon of acoustic emission will occur. Through the detection of acoustic emission, the growth activity of electrical branches can be effectively observed. In addition, since the acoustic emission detection is not sensitive to the geometry of the material, it has high practicability. However, acoustic emission is a kind of dynamic detection, which can only reflect the growth position and activity of the electric branch, but cannot effectively reflect other characteristics such as the size of the electric branch.

SUMMARY OF THE INVENTION

In view of this, the purpose of the present invention is to provide an acousto-optic combination device for online monitoring of electrical tree branches.

After research, the present invention adopts following technical scheme:

An acousto-optic combination device for on-line monitoring of electric tree branches includes a signal source, a high-voltage amplifying module, an observation module, an acoustic measurement module and a data acquisition and processing module; the signal source is connected with the high-voltage amplifying module, and the high-voltage amplifying module is connected with a Needle electrode, the needle electrode is pre-buried in the dielectric under test, the bottom of the dielectric under test is coated with conductive paint and connected with a ground electrode, the observation module is set near the dielectric under test, and the acoustic measuring module is attached to the surface of the dielectric under test , the observation module and the acoustic measurement module are both connected with the data acquisition and processing module.

Preferably, the observation module includes an observation mechanism, a light source mechanism, and a rotating bracket for supporting the observation mechanism and the light source mechanism, respectively, and the rotating bracket can be adjusted around the measured dielectric in up and down, left and right, and front and rear directions.

Preferably, the observation mechanism is an optical microscope, and the optical microscope zooms, zooms in and zooms out to observe the growth of the electrical tree as a whole and locally, and transmits it to the data acquisition and processing module.

Preferably, the light source mechanism includes a side light source and a bottom light source, and the side light source and the bottom light source are respectively disposed on both sides of the dielectric under test.

Preferably, the high-voltage amplifier module is a high-voltage amplifier, and the high-voltage output end of the high-voltage amplifier is connected to the needle electrode through a wire. Among them, the high-voltage amplifier is placed on the experimental stand.

Preferably, the other output end of the high voltage amplifier reduces the output high voltage and then connects to an oscilloscope for observing the input and output waveforms.

Preferably, the acoustic detection module includes an acoustic emission detection sensor and a preamplifier, the acoustic emission detection sensor is attached to the surface of the dielectric under test, and the detected signal is amplified by the preamplifier and then transmitted to the data acquisition and processing module. Among them, the acoustic emission detection sensor and the preamplifier are supported by an adjustable rotating bracket.

Preferably, the needle electrode is arranged coaxially with the measured dielectric.

Preferably, the radius of curvature of the needle tip of the needle electrode in the measured dielectric is less than 5 microns.

Preferably, the data acquisition and processing module is a computer.

Preferably, the connection between the needle electrode and the wire is poured with glue, and the potting glue extends to the measured dielectric. Specifically, the needle electrode and the high-voltage wire are firmly connected and poured with epoxy glue, and the potting glue is extended to the measured dielectric, completely wrapping the needle electrode between the wire and the measured dielectric, leaving no gap to prevent partial discharge under high voltage. Flashover along the surface.

The detection method of the above-mentioned acousto-optic combined device for online monitoring of electrical tree branches specifically includes the following steps:

1) Make a solid insulating material with good transparency into the dielectric under test, embed the needle electrode in the dielectric under test along the length direction, and connect the other side of the dielectric under test in the direction of elongation to the ground electrode;

2) Set the frequency and amplitude of the output signal of the signal source, and transmit the signal to the high-voltage amplifier through the wire. After the signal is amplified by the high-voltage amplifier, it is transmitted to the needle electrode through the high-voltage wire;

3) The other output end of the high-voltage amplifier reduces the output high voltage and then connects to the oscilloscope to observe the input and output waveforms;

4) Adjust the side light source and the bottom light source in the observation module to a suitable position, and adjust the optical microscope in the observation module to a suitable multiple to fix, and transmit the overall and local growth of the electrical tree of the material with good transparency observed by the microscope to the computer;

5) Keep the environment quiet, adjust the acoustic emission detection sensor in the acoustic measurement module so that it is attached to the surface of the measured dielectric near the needle tip of the needle electrode, and the signal detected by the acoustic emission detection sensor is amplified by the preamplifier and transmitted to the computer;

6) Adjust the amplitude of the output voltage of the signal source, detect the growth of the electrical tree with the amplitude change through the microscope and the acoustic emission detection sensor, and transmit it to the computer;

7) After the electric tree grows to a certain value, turn off the power supply, process and analyze the optical data and acoustic data collected in the computer, and obtain the maximum length of the electric tree growth as:

l _eb =max[l _end ] (Formula I)

In formula I, l _eb represents the maximum length from the needle tip to the end point of the electrical branch, and l _end represents the measured length from the needle tip to the terminal point of the electrical branch, that is, each measured length from the needle tip to the terminal point of the electrical branch;

The average intensity of acoustic emission per 10 seconds is obtained as:

In formula II, D _10s-average represents the arithmetic mean of the decibel value of each sampling point in every 10 seconds, t ₀ represents the starting time of the decibel value of acoustic emission collection in any 10-second period, and D(t) represents the acquisition at time t. to the decibel value;

The increment Δl _eb of the electrical branch length in each 10-second interval is obtained by l _end , and the relationship between the increment Δl _eb of the electrical branch length in each 10-second interval and the average intensity of acoustic emission is fitted to obtain the average acoustic emission per 10-second interval. The relationship between strength and electrical branch length increment is:

D _10s-average =1755.4Δl _eb +6.3 (Formula III)

In formula III, D _10s-average represents the arithmetic mean of the decibel values of each sampling point in every 10 seconds, and Δle _eb represents the increment of the electrical tree length in every 10-second interval;

8) The model or formula obtained above is used for monitoring and analysis of materials with poor transparency or opaqueness.

The beneficial effects of the present invention are:

The acousto-optic combination device for on-line monitoring of electrical tree branches of the present invention observes and measures the growth process of electrical tree branches of materials with good transparency through optical equipment, and simultaneously processes and extracts the detected acoustic emission signals with acoustic equipment, and then uses computer The relationship between optical phenomena and acoustic emission characteristics at different growth stages of electrical branches is obtained by analysis, and then it is applied to the monitoring and analysis of similar materials with poor transparency or opaqueness, which makes up for the fact that a single acoustic detection can only measure dynamic characteristics and optical detection. Limited by the degree of light transmittance of the material, in addition, by using a solid medium to insulate the exposed electrical connections, the inconvenience caused by the use of insulating oil is avoided, and it has higher practicability. The growth process has potential applications.

Description of drawings

Fig. 1 is the structure schematic diagram of the acousto-optic combination device of the electric tree on-line monitoring of the present invention;

In the figure, 1-computer; 2-optical microscope; 3-side light source; 4-bottom light source; 5-acoustic emission detection sensor; 6-preamplifier; 7-measured dielectric; 8-insulation potting glue;

2 is a graph showing the relationship between the length characteristic and time of the electrical tree branch detected by the acousto-optic combination device for on-line monitoring of electrical tree branch according to the present invention;

Fig. 3 is the variation diagram of the average intensity of acoustic emission obtained by the detection of the acoustic-optical combination device of the electric tree online monitoring of the present invention;

Fig. 4 is the relationship between the increment Δle _eb of the electrical branch length and the average intensity of acoustic emission obtained by fitting the acousto-optic combination device for on-line monitoring of electrical branch according to the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1

As shown in Figure 1, the acousto-optic combination device for on-line monitoring of electrical tree branches includes a signal source, a high-voltage amplifying module, an observation module, an acoustic measurement module and a data acquisition and processing module 1; the signal source is connected to the high-voltage amplifying module, and the high-voltage amplifying module is connected There are needle electrodes, the needle electrodes are pre-buried in the measured dielectric 7, the bottom of the measured dielectric 7 is coated with conductive paint and connected with a ground electrode, the observation module is set near the measured dielectric 7, and the acoustic measurement module is attached to the measured dielectric 7. The surface, the observation module and the acoustic measurement module are all connected with the data acquisition and processing module 1 . Among them, the bottom of the dielectric under test is coated with conductive paint and connected to the ground electrode to avoid discharge on the surface of the dielectric under test.

The observation module includes an observation mechanism, a light source mechanism, and a rotating bracket for supporting the observation mechanism and the light source mechanism respectively. The rotating bracket can be adjusted around the measured dielectric in the up and down, left and right and front and rear directions.

The observation mechanism is an optical microscope 2 , and the optical microscope 2 zooms in and zooms out to observe the growth of the electrical tree as a whole and locally, and transmits it to the data acquisition and processing module 1 .

The light source mechanism includes a side light source 3 and a bottom light source 4 , and the side light source 3 and the bottom light source 4 are respectively arranged on both sides of the measured dielectric 7 .

The high-voltage amplifier module is a high-voltage amplifier, and the high-voltage output end of the high-voltage amplifier is connected with the needle electrode through a wire. The other output end of the high voltage amplifier reduces the output high voltage and then connects to the oscilloscope to observe the input and output waveforms.

The acoustic detection module includes an acoustic emission detection sensor 5 and a preamplifier 6 . The acoustic emission detection sensor 5 is attached to the surface of the measured dielectric 7 , and the detected signal is amplified by the preamplifier 6 and transmitted to the data acquisition and processing module 1 .

The needle electrode is arranged coaxially with the measured dielectric 7 . The radius of curvature of the needle tip of the needle electrode in the measured dielectric 7 is less than 5 microns.

The data acquisition and processing module 1 is a computer.

The connection between the needle electrode and the wire is poured with glue, and the potting glue extends to the measured dielectric.

The detection method of the above-mentioned acousto-optic combination device for on-line monitoring of electrical trees uses a dielectric material with good transparency as the measured dielectric, and specifically includes the following steps:

1) Add E-51 epoxy resin with good transparency, add curing agent and catalyst, and make a sample dielectric by stirring, degassing, heating and curing, etc., and embed the extension direction of the needle electrode into the measured dielectric, and the Connect the ground electrode on the other side of the measuring dielectric along the length direction;

2) Set the output frequency of the signal source to a sine wave with a frequency of 50Hz and an amplitude of 2V, and transmit the signal to a high-voltage amplifier with a gain of 5000 through a wire for amplification to obtain a power-frequency sine wave with an amplitude of 10KV, and then transmit it to the needle electrode through the high-voltage line;

3) The other output end of the 5000 times gain high voltage amplifier will reduce the output high voltage and connect it to the oscilloscope to observe the specific waveforms of the input and output signals;

4) Adjust the side light source and the bottom light source in the observation module to a suitable position and fix, and adjust the optical microscope in the observation module to a suitable multiple to fix, and observe the overall and local growth of the electrical branches of the dielectric material with good transparency obtained by the camera of the microscope. transmission of information to a computer;

5) At the same time, keep the environment quiet, adjust the acoustic emission detection sensor in the acoustic measurement module to make it stick to the measured dielectric surface near the needle tip of the needle electrode, and the signal detected by the acoustic emission detection sensor is amplified by the preamplifier and transmitted to the computer;

6) Adjust the amplitude of the output voltage of the signal source, so that the amplified amplitude of the high-voltage amplifier gradually rises to 20KV, and the growth of the electrical tree with the amplitude change is detected by the microscope and the acoustic emission detection sensor, and transmitted to the computer;

7) When the electric tree grows to about 1mm, turn off the power supply, process and analyze the data collected in the computer, and obtain relevant models or formulas;

The data of the first 10 min was taken for analysis, and the captured optical images were extracted every 10 s to obtain a series of images. Using the proportional relationship between the actual length and the pixel point, the length of the electrical tree branch in the extracted frame is measured as:

l _eb =max[l _end ] (Formula I)

In formula I, _{le eb} represents the maximum length from the needle tip to the end point of the electrical branch, and l _end represents the measured length from the needle tip to the terminal point of the electrical branch, that is, each measured length from the needle tip to the terminal point of the electrical branch.

The relationship between the length characteristic of the electrical branch and the time is shown in Figure 2.

From the analysis in Figure 2, it can be seen that from the start of timing to 140s, the electrical branch length increases from zero, and the corresponding electrical branch length increment Δl _eb also changes from 0 to a positive value, indicating that electrical branches are generated and begin to grow, which can be calculated The average growth rate is 0.00137mm/s.

The sampled acoustic signal is processed to obtain the average intensity of acoustic emission per 10 seconds as:

In formula II, D _10s-average represents the arithmetic mean of the decibel value of each sampling point in every 10 seconds, t ₀ represents the starting time of the decibel value of acoustic emission collection in any 10-second period, and D(t) represents the acquisition at time t. to the decibel value.

The variation graph of the acquired mean intensity of acoustic emission is shown in Fig. 3 .

From the analysis in Figure 3, it can be seen that the acoustic signal collected in the initial stage is weak, and the acoustic signal in the middle and rear stages fluctuates within a certain range after a rise, which basically corresponds to the generation and growth of electric tree branches in time.

The increment Δle _eb of the electrical branch length is fitted with the average intensity of acoustic emission, and the results are shown in Fig. 4.

According to the analysis and fitting in Figure 4, under the given experimental conditions, the relationship between the average intensity of acoustic emission per 10 seconds and the length increment of electrical branches is:

D _10s-average =1755.4Δl _eb +6.3 (Formula III)

In formula III, D _10s-average represents the arithmetic mean of the decibel values of each sampling point in every 10 seconds, and Δle _eb represents the increment of the electrical tree length.

It can be seen from the analysis in FIG. 4 that the acoustic signal intensity corresponding to the period when the electrical tree length increment is 0 is relatively weak, which can be considered as environmental noise or a noise signal in the amplifier circuit. However, in the period when the length of the electrical branch is larger, the collected acoustic emission signal is stronger, and under the premise of ignoring individual deviation points, it can be considered that the two have a linear relationship under the current experimental conditions.

To sum up, it can be seen that the acoustic signal intensity measured during the generation and development of electric tree branches is significantly improved compared with that when they are not generated. grow. In addition, the signal is weak when there is no electrical tree at first, which proves the feasibility of the acousto-optic combination device.

The acousto-optic combination device for online monitoring of electrical tree branches of the present invention uses the combination of acoustic equipment and optical equipment to measure electrical tree branches on-line, which makes up for the limitation that single acoustic detection can only measure dynamic characteristics and optical detection is limited by the degree of light transmittance of materials . Compared with a single measurement, the present invention observes the electrical tree growth process of the material with good transparency through optical equipment, and at the same time, processes and extracts the detected acoustic emission signal with acoustic equipment, and analyzes and obtains the optical phenomena of electrical tree branches in different growth stages. The correlation with acoustic emission properties is then applied to the monitoring analysis of similar but less transparent or opaque materials.

Of course, the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still understand the foregoing embodiments. The technical solutions described are modified, or some technical features thereof are equivalently replaced. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. The acousto-optic combined device for the on-line monitoring of the electric branches is characterized by comprising a signal source, a high-voltage amplification module, an observation module, an acoustic measurement module and a data acquisition and processing module; the signal source is connected with the high-voltage amplification module, the high-voltage amplification module is connected with a needle electrode, the needle electrode is embedded in a tested medium, the bottom of the tested medium is coated with conductive paint and is connected with a ground electrode, the observation module is arranged near the tested medium, the acoustic measurement module is attached to the surface of the tested medium, and the observation module and the acoustic measurement module are both connected with the data acquisition and processing module.

2. The acousto-optic combination device for on-line monitoring of electrical branches according to claim 1, wherein the observation module comprises an observation mechanism, a light source mechanism, and a rotating bracket for supporting the observation mechanism and the light source mechanism, respectively, the rotating bracket being adjustable in up-and-down, left-and-right, and front-and-back directions around the measured electrical medium.

3. The acousto-optic combination device for on-line monitoring of electric tree branches according to claim 2, wherein the observation mechanism is an optical microscope, and the optical microscope zooms.

4. The acousto-optic combination device for on-line monitoring of electric tree branches as claimed in claim 2, wherein the light source mechanism comprises a side surface light source and a bottom surface light source, and the side surface light source and the bottom surface light source are respectively arranged on two sides of the medium to be measured.

5. The acousto-optic combination device for on-line monitoring of electrical branches according to claim 1, wherein the high voltage amplification module is a high voltage amplifier, and a high voltage output end of the high voltage amplifier is connected with the needle electrode through a lead.

6. The acousto-optic combination device for on-line monitoring of electrical branches of claim 5, wherein the other output end of the high voltage amplifier reduces the output high voltage and then connects the reduced output high voltage to an oscilloscope for observing the input and output waveforms.

7. The acousto-optic combination device for on-line monitoring of the electric tree branches as claimed in claim 1, wherein the acoustic measurement module comprises an acoustic emission detection sensor and a preamplifier, the acoustic emission detection sensor is attached to the surface of the measured electric medium, and the acoustic emission detection sensor amplifies the detected signal through the preamplifier and transmits the amplified signal to the data acquisition and processing module.

8. The acousto-optic combination device for on-line monitoring of electrical branches according to claim 1, wherein the needle electrode is coaxially arranged with the measured dielectric.

9. The acousto-optic combination device for on-line monitoring of electrical tree branches according to claim 1, wherein the data acquisition and processing module is a computer.

10. The acousto-optic combination device for on-line monitoring of electrical branches of claim 1, wherein the joint of the needle electrode and the lead wire is poured with glue, and the pouring glue extends to the measured electrical medium.

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