Calibration Device and Method for Dissolved Gas Monitoring System in Photoacoustic Spectroscopy Transformer Oil

Abstract

The present invention relates to a calibration device for a dissolved gas monitoring system in transformer oil by photoacoustic spectroscopy, which includes a thermostatic chamber provided with a controller. Inside the thermostatic chamber, there is a water bath tank with a certain volume. An intake pipe and an outlet pipe are provided above the water level of the water bath tank. Both the intake pipe and the outlet pipe are connected to the water bath tank and extend outside the thermostatic chamber. A dew point meter is provided on the outlet pipe outside the thermostatic chamber. A heating device and a temperature sensor are also provided inside the thermostatic chamber. Both the heating device and the temperature sensor are controlled and connected to the controller. This calibration device can effectively reduce the probability of interference of water vapor in the dissolved gas in transformer oil on each component gas, ensure the measurement results, and thus can timely monitor the concentration of the dissolved gas in the oil and understand the operating condition of the transformer, warn of potential faults, and avoid the occurrence of catastrophic accidents. A calibration method for a dissolved gas monitoring system in transformer oil by photoacoustic spectroscopy also has the advantages of warning of potential faults and avoiding the occurrence of catastrophic accidents.

Description

Technical Field

[0001] The present invention relates to the technical field of on-line monitoring of transformers, and in particular to a calibration device for a monitoring system for dissolved gases in transformer oil by photoacoustic spectroscopy. Background Art

[0002] Oil-immersed power transformers are one of the important equipment in the power supply and distribution systems of industrial and mining enterprises and civil buildings. It steps down the 10(6)kV or 35kV network voltage to the 230 / 400V bus voltage used by users. Such products are applicable to alternating current 50(60)Hz, with a maximum three-phase rated capacity of 2500kVA (the maximum single-phase rated capacity is 833kVA, and single-phase transformers are generally not recommended). It can be used indoors (outdoors). When the capacity is 315kVA and below, it can be installed on poles. The ambient temperature should not be higher than 40°C and not lower than -25°C. The highest daily average temperature is 30°C, and the highest annual average temperature is 20°C. The relative humidity should not exceed 90% (at an ambient temperature of 25°C), and the altitude should not exceed 1000m. If it does not meet the above usage conditions, appropriate rating adjustments should be made according to the relevant regulations of GB6450-86.

[0003] During long-term operation, oil-immersed power transformers may experience latent faults such as internal overheating and partial discharge. Overheating, discharge, etc. will cause the insulating oil to crack, thereby generating dissolved gases such as hydrogen, methane, ethane, acetylene, ethylene, carbon monoxide, and carbon dioxide; different fault types produce different gas components and concentrations.

[0004] The monitoring system for dissolved gases in transformer oil is an effective means to judge the latent faults of power transformers and is widely used. Currently, this system generally uses chromatographic column method and spectroscopic method to detect the concentration of dissolved gases in the oil. According to the measurement range regulations of multi-component on-line monitoring devices in the latest power industry standard DL / T1498.2-2016 "Technical Specifications for On-line Monitoring Devices of Substation Equipment - Part 2: On-line Monitoring Devices for Dissolved Gases in Transformer Oil", the lowest lower limit of the detection range is 0.5uL / L for acetylene. In the measurement range of 0.5 - 5uL / L, the measurement error of Class A is less than ±0.5uL / L or ±30% (take the larger value). Considering factors such as oil-gas separation error, photoacoustic spectroscopy measurement error, and cross-interference errors between water vapor and various components, the requirement for the measurement accuracy of the system is relatively high.

[0005] Since water vapor has absorption in almost the entire infrared spectral band, even if an ultra-narrowband infrared filter is used to separate the fingerprint absorption spectra of each component gas in the photoacoustic spectroscopy transformer oil dissolved gas detection system with a broadband infrared light source, due to the different molecular structures of the gases themselves, the infrared fingerprint absorption spectra of some gases are very narrow. Coupled with the processing technology limitations of the ultra-narrowband infrared filter, the infrared absorption spectra of each gas separated by the ultra-narrowband filter cannot completely match the infrared absorption fingerprint spectra of each gas. Therefore, the infrared fingerprint absorption spectrum of water vapor in the infrared band will overlap with the infrared fingerprint absorption spectra of some gases. When measuring these gases, water vapor will interfere with the measurement, resulting in a large measurement error, unable to timely monitor the concentration of dissolved gases in the oil and understand the operating conditions of the transformer, and thus unable to warn of potential faults, leading to catastrophic accidents. Therefore, on-line monitoring of transformer oil and gas has very important significance. Summary of the Invention

[0006] In order to overcome the above defects in the prior art, the first object of the present invention is to provide a calibration device for a photoacoustic spectroscopy transformer oil dissolved gas monitoring system. The calibration device has a clever structure, can effectively reduce the probability of interference of water vapor in the dissolved gas in the transformer oil on each component gas, ensure the measurement result, and then can timely monitor the concentration of dissolved gas in the oil and understand the operating conditions of the transformer, warn of potential faults, avoid the occurrence of catastrophic accidents, and ensure the safety of the transformer during use. The second object of the present invention is to provide a calibration method for a photoacoustic spectroscopy transformer oil dissolved gas monitoring system. In actual work, the water vapor concentration value at different temperatures is directly measured by a dew point meter, and the system response value can also be measured. Thus, the concentration value of the gas to be actually measured can be reflected, and the monitoring result is intuitive and clear, facilitating the operator to observe. It also has the advantages of being able to warn of potential faults and avoid the occurrence of catastrophic accidents.

[0007] The above calibration device for a photoacoustic spectroscopy transformer oil dissolved gas monitoring system and the above calibration method for a photoacoustic spectroscopy transformer oil dissolved gas monitoring system are technically interrelated and belong to the same inventive concept.

[0008] In order to achieve the above first object of the invention, the present invention adopts the following technical solutions: A calibration device for a photoacoustic spectroscopy transformer oil dissolved gas monitoring system includes a constant temperature box provided with a controller. Inside the constant temperature box, there is a water bath tank with a certain volume. An intake pipe and an outlet pipe are provided above the water level of the water bath tank. The intake pipe and the outlet pipe are both connected to the water bath tank and extend outside the constant temperature box. A dew point meter is provided on the outlet pipe outside the constant temperature box. A heating device and a temperature sensor are also provided inside the constant temperature box. The heating device and the temperature sensor are both controlled and connected to the controller.

[0009] As a preferred embodiment of the present invention, the water bath tank is provided with a water level sensor, and the water level sensor is connected to the controller for control.

[0010] As a preferred embodiment of the present invention, the water level sensor is arranged below the air inlet pipe.

[0011] As a preferred embodiment of the present invention, the heating device is arranged at the bottom of the water bath tank.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: In a calibration device for a dissolved gas monitoring system in transformer oil by photoacoustic spectroscopy of the present invention, by adding a standard gas water bath tooling in the monitoring system, the probability of interference of water vapor in the dissolved gas in the transformer oil on each component gas can be effectively reduced, the measurement result can be guaranteed, and then the concentration of the dissolved gas in the oil can be monitored in a timely manner, the operation status of the transformer can be understood, latent faults can be warned, the occurrence of catastrophic accidents can be avoided, and the safety of the transformer during use can be ensured.

[0013] In order to achieve the second object of the present invention, the following technical solutions are adopted: A calibration method for a dissolved gas monitoring system in transformer oil by photoacoustic spectroscopy. When calibrating the dissolved gas monitoring system in transformer oil by photoacoustic spectroscopy, the following steps are included:

[0014] S1. Pass the standard gases with low, medium, and high concentrations through the water bath tanks at three different temperatures of low, medium, and high in sequence to mix a mixed gas of the standard gas and water vapor;

[0015] S2. Then use a dew point meter connected to the outlet pipe to measure the concentration of water vapor;

[0016] S3. Preset the response value to the standard gas in the monitoring system as y n , and the different standard gas concentration values are represented as x n , then the response relationship formula generated by the standard gases with low, medium, and high concentrations under the interference of water vapor at low temperature can be obtained as y1 = k 低 x1 + b 低 ;

[0017] S4. Then pass the standard gases with low, medium, and high concentrations through the water bath tank at medium temperature in sequence to obtain the response relationship formula y2 = k 中 x2 + b 中 ;

[0018] S5. Finally, pass the standard gases with low, medium, and high concentrations through the water bath tank at high temperature in sequence to obtain the response relationship formula y3 = k 高 x3 + b 高;

[0019] S6. The water vapor concentration values at three different temperatures of low, medium, and high are directly measured by a dew point meter, and the system response value can also be measured. Thus, the gas concentration value to be actually measured can be reflected.

[0020] As a preferred embodiment of the present invention, it is assumed that the water vapor concentration value is represented as X n , then the low, medium, and high water vapor concentrations can be respectively represented as X 低 , X 中 , X 高 ; then use y1 = k 低 x1 + b 低 , y2 = k 中 x2 + b 中 , y3 = k 高 x3 + b 高 to establish the relationships between k n and b n and X n respectively, and re - establish the relationship between the water vapor concentration X n under different interference conditions of low, medium, and high temperatures and the different standard gas concentrations x n and the system response value y n as y n = k n x n + b n .

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: In the calibration method of the photoacoustic spectroscopy transformer oil dissolved gas monitoring system of the present invention, during the actual operation of the system, the water vapor concentration values at different temperatures can be directly measured by a dew point meter, and the monitoring results are intuitive and clear, which is convenient for operators to observe. It also has the advantages of being able to warn of potential faults and avoid the occurrence of catastrophic accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic structural diagram of a calibration device for a photoacoustic spectroscopy transformer oil dissolved gas monitoring system in an embodiment of the present invention.

[0023] Reference numerals: 1. Constant temperature box; 2. Inlet pipe; 3. Outlet pipe; 4. Controller; 5. Temperature sensor; 6. Water level sensor; 7. Water bath tank; 8. Dew point meter; 9. Heating device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] As Figure 1 shown, a calibration device for a dissolved gas monitoring system in transformer oil by photoacoustic spectroscopy includes a constant temperature box 1 provided with a controller 4. Inside the constant temperature box 1, there is a water bath tank 7 with a certain volume. A certain amount of water is filled in the water bath tank 7 to generate water vapor. In order to be able to monitor the concentration of dissolved gas in the oil online in real time, understand the operating condition of the transformer in a timely manner, and give early warning of potential faults, so as to avoid catastrophic accidents, an air inlet pipe 2 and an air outlet pipe 3 for facilitating the entry and exit of gas are provided above the water level of the water bath tank 7. In order to facilitate the connection of the air inlet pipe 2 and the air outlet pipe 3 to other components, the air inlet pipe 2 and the air outlet pipe 3 are both connected to the water bath tank 7 and extend outside the constant temperature box 1. And a dew point meter 8 is provided on the air outlet pipe 3 outside the constant temperature box 1. Through the dew point meter 8, the water vapor concentration value at different temperatures can be directly measured, and the system response value can also be measured, and thus the actual gas concentration value to be measured can be reflected.

[0026] In order to make the water in the water bath tank 7 present at different temperatures to monitor the influence of water vapor at different temperatures on the calibration gas, a heating device 9 and a temperature sensor 5 are further provided in the constant temperature box 1. The heating device 9, the temperature sensor 5 and the water level sensor 5 are all connected to the controller 4 for control. The temperature sensor 5 can detect the temperature of the water in the water bath tank 7 and transmit the temperature signal to the controller 4, and then the controller 4 controls the heating device 9 to decide whether to heat.

[0027] In order to facilitate real-time monitoring of the water level and prevent the water in the water bath tank 7 from flowing back into the air inlet pipe 2 and the air outlet pipe 3, affecting the monitoring results, a water level sensor 6 is provided in the water bath tank 7. Further, the water level sensor 6 is arranged below the air inlet pipe 2.

[0028] In order to facilitate heating the water in the water bath tank 7, the heating device 9 is arranged at the bottom of the water bath tank 7. The heating device 9 can be a heating wire with a simple structure, which is convenient to install and has high economic applicability.

[0029] A calibration method for a dissolved gas monitoring system in transformer oil by photoacoustic spectroscopy includes the following steps when calibrating the dissolved gas monitoring system in transformer oil by photoacoustic spectroscopy:

[0030] S1. Since the saturated water vapor content in water is different at different temperatures, in order to ensure the accuracy of the monitoring results, the standard gases with low, medium, and high concentrations are successively passed through the water bath tanks 7 at three different temperatures, namely low, medium, and high. That is, the standard gas with low concentration is successively passed through the water bath tanks 7 at three different temperatures, the standard gas with medium concentration is successively passed through the water bath tanks 7 at three different temperatures, and then the standard gas with high concentration is successively passed through the water bath tanks 7 at three different temperatures to mix the standard gas and the water vapor to form a mixed gas.

[0031] S2. Then, the dew point meter 8 connected to the outlet pipe 3 can accurately measure the concentration of the water vapor. The dew point meter 8 mainly has the following advantages: high stability, under severe interference conditions, the measured data can be stabilized within the range of ±0.5 °C, and it has excellent long-term stability and good repeatability; high precision, using imported high-performance dew point sensors and high-speed 12-bit Σ-Δ AD analog-to-digital converters, with a maximum resolution of 0.1 °C, fully meeting the actual measurement requirements, achieving accurate and reliable measurement results throughout the full range, wide measurement range, fast response speed, and stable and reliable measurement results; intelligent, the dew point meter 8 performs self-calibration when powered on, the sensor probe can automatically calibrate the zero point, automatically eliminate the systematic error introduced by zero drift, and ensure the accuracy of the measurement; long service life, the dew point meter 8 usually comes with an oil pollution filtering device, is not affected by dust particles and most chemical contaminations, can provide anti-oil pollution protection for the sensor, is extremely suitable for use in industrial environments, and the dryer can effectively protect the dew point sensor probe and extend the service life of the sensor.

[0032] S3. Preset the response value of the standard gas in the monitoring system as y n , and the different standard gas concentration values are represented as x n . According to the above method, the response relationship formula generated by the standard gases with low, medium, and high concentrations under the interference of water vapor at low temperature can be obtained as y1 = k 低 x1 + b 低 ;

[0033] S4. Then, the standard gases with low, medium, and high concentrations are successively passed through the water bath tank 7 at medium temperature, and the response relationship formula y2 = k 中 x2 + b 中 ; generated by the standard gases with low, medium, and high concentrations under the interference of water vapor at medium temperature can be obtained.

[0034] S5. Finally, the standard gases with low, medium, and high concentrations are successively passed through the water bath tank 7 at high temperature, and the response relationship formula y3 = k 高 x3 + b 高 ; generated by the standard gases with low, medium, and high concentrations under the interference of water vapor at high temperature can be obtained. S6. The water vapor concentration values at three different temperatures of low, medium, and high are directly measured by the dew point meter 8, and the system response value can also be measured. Thus, the actual gas concentration value to be measured can be reflected.

[0035] Assume that the water vapor concentration value is represented as X n , then the low, medium, and high water vapor concentrations can be respectively represented as X 低 , X 中 , X 高 ; then use y1 = k 低 x1 + b 低 , y2 = k 中 x2 + b 中 , y3 = k 高 x3 + b 高 to establish the relationships between k n and b n and X n respectively, and re - establish the relationships between the water vapor concentration X n under different interference conditions of different standard gas concentrations x n and the system response value y n as y n = k n x n + b n . In the actual operation of the system, the water vapor concentration values at different temperatures are directly measured by the dew - point meter 8, and the system response value can also be measured. Thus, the actual gas concentration value to be measured can be reflected.

[0036] In the photoacoustic spectroscopy transformer oil dissolved gas monitoring system calibration device and method of the present invention, by adding a standard gas water bath tooling in the monitoring system, the probability of the interference of water vapor in the dissolved gas in the transformer oil on each component gas can be effectively reduced, the measurement result can be guaranteed, and then the concentration of the dissolved gas in the oil can be monitored in time, the operation status of the transformer can be understood, latent faults can be warned, the occurrence of catastrophic accidents can be avoided, and the safety of the transformer during use can be ensured.

[0037] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention; therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

[0038] Although the accompanying drawing reference numerals in the figures: 1, incubator; 2, intake pipe; 3, outlet pipe; 4, controller; 5, temperature sensor; 6, water level sensor; 7, water bath tank; 8, dew point meter; 9, heating device and other terms are used more in this text, the possibility of using other terms is not excluded. The use of these terms is only for the purpose of more conveniently describing and explaining the essence of the present invention; interpreting them as any additional limitation is contrary to the spirit of the present invention.

Claims

1. A calibration method for a dissolved gas monitoring system in transformer oil using photoacoustic spectroscopy, the calibration method for the dissolved gas monitoring system in transformer oil using photoacoustic spectroscopy is implemented by a calibration device for the dissolved gas monitoring system in transformer oil using photoacoustic spectroscopy, characterized in that, The calibration device for the dissolved gas monitoring system in transformer oil by photoacoustic spectroscopy includes a thermostatic chamber (1) provided with a controller (4). Inside the thermostatic chamber (1), there is a water bath tank (7) with a certain volume. Above the water level of the water bath tank (7), there are an inlet pipe (2) and an outlet pipe (3). Both the inlet pipe (2) and the outlet pipe (3) are connected to the water bath tank (7) and extend outside the thermostatic chamber (1). And a dew point meter (8) is provided on the outlet pipe (3) outside the thermostatic chamber (1). Inside the thermostatic chamber (1), there is also a heating device (9) and a temperature sensor (5). Both the heating device (9) and the temperature sensor (5) are controlled and connected to the controller (4). The calibration method for the dissolved gas monitoring system in transformer oil by photoacoustic spectroscopy includes the following steps when calibrating the dissolved gas monitoring system in transformer oil by photoacoustic spectroscopy: S1. Pass the standard gases with low, medium, and high concentrations through the water bath tank (7) at three different temperatures of low, medium, and high in sequence to mix the mixed gas of the standard gas and water vapor; S2. Then use the dew point meter (8) connected to the outlet pipe (3) to measure the concentration of water vapor; S3. Preset the response value to the standard gas in the monitoring system as y n , and the different standard gas concentration values are represented as x n , then the response relationship formula generated by the standard gases with low, medium, and high concentrations under the water vapor interference at low temperature can be obtained as y1 = k 低 x1 + b 低 ; S4. Then pass the standard gases with low, medium, and high concentrations through the water bath tank (7) at medium temperature in sequence to obtain the response relationship formula y2 = k 中 x2 + b 中 generated by the standard gases with low, medium, and high concentrations under the water vapor interference at medium temperature; S5. Finally, pass the standard gases with low, medium, and high concentrations through the water bath tank (7) at high temperature in sequence to obtain the response relationship formula y3 = k 高 x3 + b 高 generated by the standard gases with low, medium, and high concentrations under the water vapor interference at high temperature; S6. The water vapor concentration values at three different temperatures of low, medium, and high are directly measured by the dew point meter (8), and the system response value can be measured. Thus, the actual gas concentration value to be measured can be reflected. Assume the water vapor concentration value is represented as X n , then the low, medium, and high water vapor concentrations can be respectively represented as X 低 , X 中 , X 高 ; Then use y1 = k 低 x1 + b 低 , y2 = k 中 x2 + b 中 , y3 = k 高 x3 + b 高 to establish k n and b n and X n Re-establish the water vapor concentrations X at three different temperatures of low, medium, and high based on the relationship n The different standard gas concentrations x under interference conditions n And the system response value y n The relationship y n = k n x n + b n .

2. The calibration method of the dissolved gas monitoring system in transformer oil by photoacoustic spectroscopy according to claim 1, wherein The water bath tank (7) is provided with a water level sensor (6), and the water level sensor (6) is connected to the controller (4) for control.

3. The calibration method for the dissolved gas monitoring system in transformer oil by photoacoustic spectroscopy according to claim 2, wherein The water level sensor (6) is arranged below the air inlet pipe (2).

4. The calibration method for the dissolved gas monitoring system in transformer oil by photoacoustic spectroscopy according to claim 1, wherein The heating device (9) is arranged at the bottom of the water bath tank (7).

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