CN100351624C - Dissolved gas analyzer of electric power transformer oil based on Raman technology - Google Patents

Abstract

The invention discloses a Raman technology-based analysis device for dissolved gas in power transformer oil, which belongs to the technical field of power equipment state detection. The invention includes: laser light source, sample pool and its optical system, multi-channel spectrometer, gas compression device and computer communication part. The sample cell and its optical system and gas compression device are connected through pipelines, the spectrometer and computer communication part are connected through communication lines for data exchange, the sample cell and its optical system and laser light source are fixed on a mounting plate, the sample cell and its optical system and Spectrometers are self-contained and transmit information through light. Compared with other devices, the sensitivity and precision of the present invention are greatly improved, and fully automatic control is realized; the working time is greatly reduced (reduced by more than 5-10 times), and has incomparable advantages compared with other devices.

Description

Dissolved gas analysis device in power transformer oil based on Raman technology

technical field

The invention relates to a detection device for dissolved gas in transformer oil, in particular to a Raman technology-based analysis device for dissolved gas in power transformer oil, which belongs to the technical field of electric equipment state detection.

Background technique

Large-scale power transformers are one of the most important and expensive equipment in power transmission and transformation systems. The quality of their insulation conditions is related to whether the power system can operate safely and reliably. A large number of studies and practices on dissolved gas analysis (DGA) in transformer oil at home and abroad show that H ₂ , CH ₄ , C ₂ H ₂ , C ₂ H ₄ , C ₂ H ₆ , CO and CO ₂ dissolved in transformer oil The ratio between the content of gas components, gas production rate and their content is reliable information reflecting the internal insulation state of the transformer, and can detect latent defects and faults of transformers more sensitively and accurately. It is generally believed that DGA is a powerful means for diagnosing transformer insulation faults . It has become a hot spot in this field to install the DGA monitoring device on the transformer in operation, collect oil samples in real time and monitor the dissolved gas in the transformer oil.

After searching the literature of the prior art, it was found that "Transformer Oil Chromatography On-line Monitoring System" published by Chen Xiaodong and others on "Mechanical Engineer" 2003 (4)-49-51, the key device of the system is to use molecular membrane for oil and gas monitoring. The separation device is used for chromatographic identification of the separated gas. Its disadvantages are: 1. Due to the congenital defects of chromatography, the detection sensitivity is low. Second, due to the long time and complicated operation of using molecular membranes to separate gases, each detection takes a long time. Three, the system is greatly affected by the external environment, and the work is unstable.

Contents of the invention

The purpose of the present invention is to address the deficiencies in the prior art, and propose a Raman technology-based analysis device for dissolved gas in power transformer oil, so that it can be used for on-line or on-site monitoring of various fault characteristic gases, with high sensitivity and high precision and good reliability.

The invention is realized through the following technical solutions, and the invention includes: a laser light source, a sample pool and its optical system, a multi-channel spectrometer, a gas compression device and a computer communication part. The connection relationship is as follows: the sample cell, the optical system and the gas compression device are connected through pipelines, the spectrometer and the computer communication part are connected through communication lines for data exchange, the sample cell, its optical system and the laser light source are fixed on a mounting plate, the sample cell and the Its optical system and spectrometer are independent, and the information is transmitted through light.

The laser light source is a fully solidified laser pumped by a semiconductor laser diode. The output wavelength is 532nm, the power stability is better than 5%, the structure is compact, and it is easy to use. The Raman (Raman) spectrum of all components of dissolved gases in transformer oil is located in the visible band, which greatly improves the acceptance sensitivity (compared to infrared spectrum). The advantage of the Raman spectrum method over the infrared spectrum and the hue spectrum analysis method is that the light source is selective and flexible. It is better that the characteristic spectral lines do not overlap, which is conducive to the simultaneous detection of multiple gas components at one time. The Glan prism and isolator are placed in front of the light exit hole of the laser, and are fixed on the same mounting plate as the laser, sample cell and optical system, to protect the laser reflected from the optical path of the sample cell from entering the laser, and to ensure that the laser is stable without damage Work, while the photosensitive diode is installed at the back end of the sample cell and the optical system, indicating that the laser is working normally and the power has reached the rated value (100mW).

The sample cell and its optical system include: spherical mirror, photodiode, Raman light collection lens, Notch filter, multi-channel spectrometer input slit, and stray light prevention lens barrel. There are three spherical mirrors, the first spherical mirror and the second spherical mirror are reflective spherical mirrors for visible wavelengths, which are respectively placed at the left and right ends of the horizontal position of the sample cell and its optical system, and the photosensitive diode is placed on the right side of the second spherical mirror; High reflection spherical mirror, the third spherical mirror is located at the lower end of the sample cell and its optical system in the direction of the vertical laser beam, the Raman light collection lens is placed in the sample cell and the middle of the optical system, and the filter (532nm<1‰) is placed in the sample cell and its optical system The upper part of the system prevents the return of 532nm light. The input slit of the multi-channel spectrometer is placed on the top of the sample cell and its optical system to prevent the stray light lens barrel from being located in the inner cavity of the sample cell and the optical system. The photosensitive diode indicates the laser output power and normal operation.

The concentric spherical mirror system is used to improve the laser focusing intensity and multi-pass excitation in the sample pool, which is more than 50 times higher than the single-pass excitation laser sample; at the same time, there is a spherical mirror in the vertical direction of the laser beam in the sample pool to collect the reverse laser beam. Mann scattered light. The image is imaged at the input slit of the multichannel spectrometer through the collection lens. The design makes full use of the collection angle of the multi-channel spectrometer to ensure that more than 70% of the Raman scattered light within the 4π solid angle enters the multi-channel spectrometer.

The multi-channel spectrometer is a miniaturized and stable multi-channel spectrometer with a focal length of 190nm, a grating of 1200L/mm, f/3.9, and a low-noise and high-sensitivity CCD with 1024×256 pixels installed at the output of the spectrometer. The disadvantage of low intensity in the spectrum is that stray light and Rayleigh scattered light must be isolated. The invention uses an anti-stray light lens barrel, a metal sealing system and an optical filter to isolate the Rayleigh scattered light below 0.1% (up to 5/10,000), so as to ensure that the Raman scattered light of trace gas can be detected.

Gas compression devices include: transformers, circulation pipelines, electronic valves, oil sample pools, sampling bags, vacuum tanks, vacuum pumps, and pipelines. Its connection relationship: the circulation pipeline is connected to the crude oil of the transformer for oil sample circulation, the oil sample pool and the sampling bag are connected through the pipeline, the electronic valve is located on the circulation pipeline and the pipeline, the vacuum pump is connected with the pipeline, and the whole system is pumped and sampled The bag is placed in a vacuum tank, but not in contact, and the upper and lower parts are connected to the pipeline respectively.

Vacuum headspace method and pressure control technology are used to collect oil samples of 500ml-1000ml, which basically reflect the operation status of dissolved gas in power transformers. In the process of internal faults in power transformers: from a small amount of N ₂ , O ₂ , H ₂ O to gradually increase CO, CO ₂ , H ₂ to CH ₄ and other alkane gases, the gas volume is about 10 milliliters, through the vacuum headspace method And pressure regulation, the gas in the oil is separated out, and then the gas in the sampling bag is compressed, and pressed into the sample cell to achieve a compression ratio of more than 50 times. Since the intensity of the Raman scattered light signal is directly proportional to the concentration of gas molecules, the higher the compression ratio, the more the detection sensitivity can be improved.

The computer and communication system realizes the acquisition and processing of CCD data by the computer, as well as various system controls. At the same time, the data can also be transmitted to each console through the computer. Since the technology in this part is very mature, it will not be repeated.

The whole working process of the present invention can be finished within half an hour. The vacuum pump pumps the oil from the circulation pipeline into the oil sample chamber through the adjustment of several electronic valves, and then vacuumizes the oil sample in the oil sample chamber through the vacuum pump and other electronic valves, and pumps the gas in the oil into the sample chamber. Then the gas is pressed into the optical sample cell through the adjustment of the electronic valve and the vacuum pump. This process takes about a few minutes; then start the laser, enter the sample cell and its optical system, and excite the oil sample gas back and forth to generate Raman scattering. For light, a CCD laser is used to collect Raman spectra. Because it is in the order of ppm, the integration time takes a few minutes. Finally, the spectral signals of the CCD are collected and the data is processed by a computer. At the same time, the computer can also control the entire process.

The Raman detection technology adopted in the present invention can achieve the accuracy, sensitivity and long-term reliability required by various DGA fault diagnosis methods for oil-immersed power transformers, and can be used for online, on-site and laboratory testing of various oil-immersed equipment in power systems and other state detection, develop DGA-based online state monitoring equipment, portable or vehicle-mounted state detection equipment, and laboratory testing equipment. Compared with other devices, the sensitivity and precision of this device are greatly improved, and fully automatic control is realized; the working time is greatly reduced (by more than 5-10 times), and it has incomparable advantages compared to other devices.

Description of drawings

Fig. 1 structural representation of the present invention

Fig. 2 structural representation of the sample cell of the present invention and its optical path system

Fig. 3 structural representation of the gas compression device of the present invention

Detailed ways

As shown in FIG. 1 , the present invention includes: a laser light source 1 , a sample pool and its optical system 2 , a multi-channel spectrometer 3 , a gas compression device 4 and a computer communication part 5 . The connection relationship is as follows: the sample cell, the optical system 2 and the gas compression device 4 are connected through pipelines, the spectrometer 3 and the computer communication part 5 are connected through a communication line for data exchange, and the sample cell, its optical system 2 and the laser light source 1 are fixed in an installation On board, the sample cell with its optical system 2 and the spectrometer 3 are independent and transmit information through light.

The laser light source 1 is composed of an all-solid-state frequency-doubled laser 6 pumped by a semiconductor diode laser, a Glan prism 7 and an isolator 8 . The three are fixed together on the mounting plate, the Glan prism 7 is placed between the isolator 8 and the laser 6 ; and the isolator 8 is arranged between the sample pool and the optical system 2 and the Glan prism 7 .

As shown in Figure 2, the sample cell and its optical system 2 include: a first spherical mirror 9, a second spherical mirror 10, a photodiode 11, a third spherical mirror 12, a Raman light collection lens 13, a Notch filter 14, and a multi-channel spectrometer Input slit 15, prevent stray light column 16. The first spherical mirror 9 and the second spherical mirror 10 are visible wavelength reflective spherical mirrors, which are respectively placed at the left and right ends of the sample pool and its optical system 2 horizontal positions, and the photodiode 11 is placed on the right side of the second spherical mirror 10; the third spherical mirror 12 is Visible band highly reflective spherical mirror, the third spherical mirror 12 is located at the lower end of the sample cell and its optical system 2 perpendicular to the laser beam direction, the Raman light collection lens 13 is placed in the sample cell and the middle section of the optical system 2, and the optical filter 14 (532nm<1‰ ) is placed on the upper part of the sample cell and its optical system 2 to prevent the 532nm light from returning. The input slit 15 of the multi-channel spectrometer is placed on the top of the system, and the lens barrel 16 for preventing stray light is located in the cavity of the sample cell and its optical system 2 .

The laser beam output by the laser 6 passes through a group of concentric first spherical mirrors 9 and second spherical mirrors 10, converging the first spherical mirrors 9 to focus the laser beam at the concentric place, increasing the excitation intensity; The second spherical mirror 10 has a high reflectivity (R>90%) on the spherical surface, and multi-pass excitation of the concentric gas sample increases by 2 orders of magnitude compared with single excitation. At the same time, because the laser beam has a waist (focal spot) and a certain focal depth (beam waist length) in the concentric part, this part of the gas sample is fully excited, and all the Raman scattered light is collected at the slit 15 (see Figure 1). , and can increase the acceptance sensitivity several times. In order to ensure that the Raman scattered light excited by the gas sample is fully collected, a visible wavelength reflective spherical mirror 12 is used to collect the backscattered light at the concentric and slit 15 planes perpendicular to the laser light path, and the Raman light collection lens 13 All the forward and backward Raman scattered light is collected into the slit 15 to ensure that more than 70% of the Raman scattered light all enter the slit 15 within a 4π solid angle. In addition to metal isolation, the Notch filter 14 is used to basically isolate stray light and Rayleigh scattered light to below 10 ^-5 ~10 ^-4 .

The multi-channel spectrometer 3 is a miniaturized multi-channel spectrometer with stable performance. It has a focal length of 190nm, a grating of 1200L/mm, and f/3.9. The astigmatism lens barrel 16, the metal sealing system and the optical filter 14 isolate the Rayleigh scattered light below 0.1%.

As shown in Figure 3, the gas compression device 4 includes: a transformer 17, three circulating pipelines 18, 19, 31, six electronic valves 20, 21, 22, 23, 24, 25, an oil sample pool 26, a sampling bag 27, A vacuum tank 28, a vacuum pump 29, and a pipeline 30 connected to the atmosphere. Its connection relationship: the first circulating pipeline 18 is connected to the crude oil of the transformer 17, the second circulating pipeline 19 is connected to the oil sample pool 26 and the sampling bag 27, the first electronic valve 20 and the second electronic valve 21 are located on the first circulating pipeline 18, and the second electronic valve 20 is located on the first circulating pipeline 18. The three electronic valves 22 are located on the second circulation pipeline 19, the fourth electronic valve 23 is located on the third circulation pipeline 31 connected to the sampling bag 27 and the sample pool optical system 2, and the fifth electronic valve 24 is located between the vacuum tank 28 and the pipeline 31. Between, the sixth electronic valve 25 is located on the connecting part of the pipeline 30 and the atmosphere, the vacuum pump 29 communicates with the third circulation pipeline 31, and is installed at the end of the third circulation pipeline 31, the sampling bag 27 is placed in the vacuum tank 28, and the upper and lower sides respectively The third circulation pipeline 31 is connected to the second circulation pipeline 19 .

Claims (5)

1, a kind of based on dissolved gas analyzer in the electric power transformer oil of Raman technology, comprise: multi-channel spectrometer based (3), computing machine communication part (5), it is characterized in that, also comprise: LASER Light Source (1), sample cell and optical system thereof (2) and gas compressing apparatus (4), sample cell and optical system (2) are connected by pipeline with gas compressing apparatus (4), spectrometer (3) is connected by connection with computing machine communication part (5) and carries out exchanges data, sample cell and optical system thereof (2) and LASER Light Source (1) are fixed on the installing plate, sample cell and optical system thereof (2) and spectrometer (3) are independently, diffuse information by light;

Described sample cell and optical system thereof (2) comprising: first spherical mirror (9) and second spherical mirror (10), photodiode (11), the 3rd spherical mirror (12), Raman light collecting lens (13), optical filter (14), multichannel spectrometer input slit (15), prevent parasitic light lens barrel (16), its annexation is: first spherical mirror (9) and second spherical mirror (10) place the two ends, the left and right sides of sample cell and optical system (2) horizontal level thereof respectively, photodiode (11) places the right side of second spherical mirror (10), the 3rd spherical mirror (12) is positioned at sample cell and optical system (2) vertical beam of light direction lower end thereof, Raman light collecting lens (13) places sample cell and optical system (2) stage casing, optical filter (14) places sample cell and optical system (2) epimere thereof, multichannel spectrometer input slit (15) places sample cell and optical system (2) top thereof, prevents that parasitic light lens barrel (16) is positioned in sample cell and optical system (2) inner chamber thereof.

2, according to claim 1 based on dissolved gas analyzer in the electric power transformer oil of Raman technology, it is characterized in that, LASER Light Source (1) is the full curing solid frequency double laser (6) by the semiconductor diode laser pumping, Glan prism (7) and isolator (8) are formed, the three is fixed on the installing plate together, Glan prism (7) is arranged in the middle of isolator (8) and the laser instrument (6), and isolator (8) is arranged between sample cell and optical system (2) and the Glan prism (7).

3, according to claim 1 based on dissolved gas analyzer in the electric power transformer oil of Raman technology, it is characterized in that, first spherical mirror (9) and second spherical mirror (10) are visible wavelength reflecting sphere mirror, and the 3rd spherical mirror (12) is the high reflecting sphere mirror of visible waveband.

4, according to claim 1ly it is characterized in that multi-channel spectrometer based (3) based on dissolved gas analyzer in the electric power transformer oil of Raman technology, its burnt long 190nm, grating 1200L/mm, f/3.9, spectrometer output place is provided with the CCD of 1024 * 256 picture dots.

5, according to claim 1 based on dissolved gas analyzer in the electric power transformer oil of Raman technology, it is characterized in that, gas compressing apparatus (4) comprising: transformer (17), first circulating line (18), second circulating line (19), the 3rd circulating line (31), six electronics valves (20,21,22,23,24,25), oil sample pond (26), sampling bag (27), vacuum tank (28), vacuum pump (29), pipeline (30), its annexation is: first circulating line (18) links to each other with transformer (17) crude oil, second circulating line (19) connects oil sample pond (26) and sampling bag (27), the first electronics valve (20), the second electronics valve (21) is positioned on first circulating line (18), the 3rd electronics valve (22) is positioned on second circulating line (19), quadrielectron valve (23) is positioned on sampling bag (27) and the 3rd circulating line (31) that sample cell and optical system (2) thereof link to each other, the 5th electronics valve (24) is positioned between vacuum tank (28) and the 3rd circulating line (31), the 6th electronics valve (25) is positioned on the section of tubing (30) that links to each other with atmosphere, vacuum pump (29) and the 3rd circulating line (31) communicate, and be located at the terminal point of the 3rd circulating line (31), sampling bag (27) places vacuum tank (28), up and down respectively with the 3rd circulating line (31), second circulating line (19) links to each other.

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