Measurement of the SO3 concentration in flue gas is important to estimate the acid dew point and to control corrosion of downstream equipment. SO3 measurement is a difficult question since SO3 is a highly reactive gas...Measurement of the SO3 concentration in flue gas is important to estimate the acid dew point and to control corrosion of downstream equipment. SO3 measurement is a difficult question since SO3 is a highly reactive gas, and its concentration is generally two orders of magnitude lower than the SO2 concentration. The SO3 concentration can be measured online by the isopropanol absorption method; however, the reliability of the test results is relatively low. This work aims to find the error sources and to evaluate the extent of influence of each factor on the measurement results. The test results from a SO3 analyzer showed that the measuring errors are mainly caused by the gas–liquid flow ratio, SO2 oxidation, and the side reactions of SO3. The error in the gas sampling rate is generally less than 13%. The isopropanol solution flow rate decreases 3% to 30% due to the volatilization of isopropanol, and accordingly, this will increase the apparent SO3 concentration. The amount of SO2 oxidation is linearly related to the SO2 concentration. The side reactions of SO3 reduce the selectivity of SO42- to nearly 73%. As sampling temperature increases from180 to 300°C, the selectivity of SO42- decreases from 73% to 50%. The presence of H2 O in the sample gas helps to reduce the measurement error by inhibiting the volatilization of the isopropanol and weakening side reactions. A formula was established to modify the displayed value, and the measurement error was reduced from 25%–54% to less than 15%.展开更多
To address the lack of voltage ratio standards for accuracy testing of low-frequency voltage transformers,it is necessary to develop a 3 kV low-frequency induction voltage divider.Firstly,based on the analysis of the ...To address the lack of voltage ratio standards for accuracy testing of low-frequency voltage transformers,it is necessary to develop a 3 kV low-frequency induction voltage divider.Firstly,based on the analysis of the error sources of the induction voltage divider,a method was proposed to calculate the excitation impedance of the induction voltage divider using complex magnetic permeability.A measurement circuit based on the lock-in principle was set up to measure the complex magnetic permeability of grained-oriented silicon steel 30P100 and permalloy 1J85 at different frequencies.Secondly,a 3 kV low-frequency induction voltage divider with a two-stage excitation and a series-wound ra-tio winding in 10 sections was designed.The errors of the two stages of the instrument transformers were calculated at 20 and 50 Hz,respectively.Finally,the divider's errors were calibrated at 20 and 50 Hz using the reference potential method.The results showed that,compared to 50 Hz,the excitation impedance of the two stages decreased and the errors increased at 20 Hz,with the overall error of the induction voltage divider being better at 50 Hz than at 20 Hz.Experimental measurements indicated that at 20 Hz,the ratio error and phase error of the 3 kV two-stage excitation induction voltage divider were better than 110-5,whereas at 50 Hz,the errors were better than 110-6.This study provides support for the accuracy testing of voltage transformers used in low-frequency flexible AC transmission projects.展开更多
基金financial support from the National Natural Science Foundation of China(No.21477131)the Special Research Funding for Public Benefit Industries from the National Ministry of Environmental Protection(No.201509012)
文摘Measurement of the SO3 concentration in flue gas is important to estimate the acid dew point and to control corrosion of downstream equipment. SO3 measurement is a difficult question since SO3 is a highly reactive gas, and its concentration is generally two orders of magnitude lower than the SO2 concentration. The SO3 concentration can be measured online by the isopropanol absorption method; however, the reliability of the test results is relatively low. This work aims to find the error sources and to evaluate the extent of influence of each factor on the measurement results. The test results from a SO3 analyzer showed that the measuring errors are mainly caused by the gas–liquid flow ratio, SO2 oxidation, and the side reactions of SO3. The error in the gas sampling rate is generally less than 13%. The isopropanol solution flow rate decreases 3% to 30% due to the volatilization of isopropanol, and accordingly, this will increase the apparent SO3 concentration. The amount of SO2 oxidation is linearly related to the SO2 concentration. The side reactions of SO3 reduce the selectivity of SO42- to nearly 73%. As sampling temperature increases from180 to 300°C, the selectivity of SO42- decreases from 73% to 50%. The presence of H2 O in the sample gas helps to reduce the measurement error by inhibiting the volatilization of the isopropanol and weakening side reactions. A formula was established to modify the displayed value, and the measurement error was reduced from 25%–54% to less than 15%.
基金The Innovation Fund Project of China Electric Power Research Institute:Research on accuracy test method of voltage transformer for low-frequency transmission and development of test system,Grant/Award Number:GY83-22-005。
文摘To address the lack of voltage ratio standards for accuracy testing of low-frequency voltage transformers,it is necessary to develop a 3 kV low-frequency induction voltage divider.Firstly,based on the analysis of the error sources of the induction voltage divider,a method was proposed to calculate the excitation impedance of the induction voltage divider using complex magnetic permeability.A measurement circuit based on the lock-in principle was set up to measure the complex magnetic permeability of grained-oriented silicon steel 30P100 and permalloy 1J85 at different frequencies.Secondly,a 3 kV low-frequency induction voltage divider with a two-stage excitation and a series-wound ra-tio winding in 10 sections was designed.The errors of the two stages of the instrument transformers were calculated at 20 and 50 Hz,respectively.Finally,the divider's errors were calibrated at 20 and 50 Hz using the reference potential method.The results showed that,compared to 50 Hz,the excitation impedance of the two stages decreased and the errors increased at 20 Hz,with the overall error of the induction voltage divider being better at 50 Hz than at 20 Hz.Experimental measurements indicated that at 20 Hz,the ratio error and phase error of the 3 kV two-stage excitation induction voltage divider were better than 110-5,whereas at 50 Hz,the errors were better than 110-6.This study provides support for the accuracy testing of voltage transformers used in low-frequency flexible AC transmission projects.
