The No. 2 main transformer has been transformed into a transformer factory in Inner Mongolia. The 110kV bushing is a product of Nanjing Electric Porcelain Co., Ltd. The model is a BRL2W-110/600 oil-paper capacitive transformer bushing. It was manufactured in 1975-08 with a capacity of 280pF.
1999-10-17 After repairing the A-phase main transformer, lift the A-phase casing and discharge the insulating oil to remove the porcelain sleeve. Place the condenser core in the drying room for drying. The temperature of the drying chamber was controlled at 80. After drying for 20 hours, the temperature dropped to 60 to remove the condenser core for assembly. After vacuum injection, use ZC7-2500V megohmmeter and BM3A anti-jamming dielectric loss meter to test. The test data is: the final screen insulation resistance to ground is 5000M, tan value is 0.79%, and the capacitance is 282pF.
After 2 h of rest, the test data: tan is 0.72%, the insulation resistance of the end screen against the ground is 5000M, and the tan value is reduced from 0.79% to 0.
72%, a decrease of 0.07%. The analysis considers that this is because the casing after maintenance oil filling will always have more or less residual bubbles in the oil. These bubbles will have partial discharges under the test voltage, thus making the tan value larger than that measured after standing for a while.
After standing for 24 hours and then testing tan from the original 0.72% rose to 0.95%, the reason is that the casing itself is damp, after 24h warming the outer insulation of the sleeve core is dried, the inner insulation layer moisture is not discharged In the insulating layer, the moisture of the inner insulation layer is not mixed with the oil when the insulating oil is just added, so the test data is relatively small. After standing for 24 hours, the moisture of the insulation layer is emitted to mix with the oil, so the test data is larger than before. .
Through the above test data analysis, although the tan value does not exceed the standard, but compared with the measured data when not wet, it is still confirmed that the casing moisture has not been completely eliminated and should continue to disintegrate and dry. 1999-10-19 disintegration, re-drying, the temperature is controlled at 80 and 48h drying, and the temperature of the drying room is reduced to ambient temperature before taking out the condenser core for assembly. After the vacuum oiling test, the insulation resistance of the screen to the ground is 10000M, the tan value is 0.14%, the capacitance is 281pF, and the error of the tan value is 0.08%. This error is caused by a small amount of air bubbles in the casing after oil injection.
After the above analysis, the main reason for the excessive tan value of the bushing is due to the bad seal entering the humid air. Summarizing the above process, the following points need to be noted in the process of handling the wet process of the casing: First, it is necessary to have a good grasp of time when drying; Second, be sure to remove the temperature of the drying chamber and then remove the baking, otherwise bake When the temperature is reduced, it will re-inhale the moisture; the third is to test after standing still for a period of time after vacuum injection so as not to make the test data error (usually large), and also to inspect the sealing performance of the casing when vacuuming.
In a word, casing has more problems in the operation of the power system, and the consequences are more serious. Therefore, sufficient attention should be paid to handling such faults.
1999-10-17 After repairing the A-phase main transformer, lift the A-phase casing and discharge the insulating oil to remove the porcelain sleeve. Place the condenser core in the drying room for drying. The temperature of the drying chamber was controlled at 80. After drying for 20 hours, the temperature dropped to 60 to remove the condenser core for assembly. After vacuum injection, use ZC7-2500V megohmmeter and BM3A anti-jamming dielectric loss meter to test. The test data is: the final screen insulation resistance to ground is 5000M, tan value is 0.79%, and the capacitance is 282pF.
After 2 h of rest, the test data: tan is 0.72%, the insulation resistance of the end screen against the ground is 5000M, and the tan value is reduced from 0.79% to 0.
72%, a decrease of 0.07%. The analysis considers that this is because the casing after maintenance oil filling will always have more or less residual bubbles in the oil. These bubbles will have partial discharges under the test voltage, thus making the tan value larger than that measured after standing for a while.
After standing for 24 hours and then testing tan from the original 0.72% rose to 0.95%, the reason is that the casing itself is damp, after 24h warming the outer insulation of the sleeve core is dried, the inner insulation layer moisture is not discharged In the insulating layer, the moisture of the inner insulation layer is not mixed with the oil when the insulating oil is just added, so the test data is relatively small. After standing for 24 hours, the moisture of the insulation layer is emitted to mix with the oil, so the test data is larger than before. .
Through the above test data analysis, although the tan value does not exceed the standard, but compared with the measured data when not wet, it is still confirmed that the casing moisture has not been completely eliminated and should continue to disintegrate and dry. 1999-10-19 disintegration, re-drying, the temperature is controlled at 80 and 48h drying, and the temperature of the drying room is reduced to ambient temperature before taking out the condenser core for assembly. After the vacuum oiling test, the insulation resistance of the screen to the ground is 10000M, the tan value is 0.14%, the capacitance is 281pF, and the error of the tan value is 0.08%. This error is caused by a small amount of air bubbles in the casing after oil injection.
After the above analysis, the main reason for the excessive tan value of the bushing is due to the bad seal entering the humid air. Summarizing the above process, the following points need to be noted in the process of handling the wet process of the casing: First, it is necessary to have a good grasp of time when drying; Second, be sure to remove the temperature of the drying chamber and then remove the baking, otherwise bake When the temperature is reduced, it will re-inhale the moisture; the third is to test after standing still for a period of time after vacuum injection so as not to make the test data error (usually large), and also to inspect the sealing performance of the casing when vacuuming.
In a word, casing has more problems in the operation of the power system, and the consequences are more serious. Therefore, sufficient attention should be paid to handling such faults.
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