110KV Oil-Immersed Transformer High-Efficiency Oil Filtering Process

Abstract

The present invention provides an efficient oil filtering process for 110KV oil-immersed transformers, which is applicable to the efficient oil filtering of multiple oil-immersed transformers. The process includes operations of vacuum pumping, oil injection, oil circulation, standing still, conducting experiments, oil pumping, and removing test bushings in sequence. When there is a test bushing installed on the first transformer, oil circulation is carried out, and at the same time, the operations of vacuum pumping, oil injection, oil circulation, and standing still are started for the second transformer without a bushing installed. At this time, the first transformer continues with the subsequent operations of conducting experiments, oil pumping, and removing the test bushing. After the first transformer completes the whole set of operations, the removed test bushing is given to the second transformer that has completed the standing still operation. At the same time, the operations of vacuum pumping, oil injection, oil circulation, and standing still are started for the third transformer without a bushing installed, and so on, with continuous alternating operations. The present invention effectively saves time and improves the construction efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of oil-immersed transformers, and particularly to an efficient oil filtering process for 110KV oil-immersed transformers. Background Art

[0002] Distribution transformers are one of the important equipment in the power supply and distribution systems of industrial and mining enterprises and civil buildings. The conventional transformer oil filtering methods are, in sequence: installing bushings, evacuating, injecting oil, oil circulation, and wiring. Currently, for oil-immersed transformers, the existing oil filtering methods are, in sequence: evacuating, injecting oil, oil circulation, standing still, conducting experiments, pumping out oil, removing test bushings, connecting cable terminals, injecting oil, and oil circulation. Because there is only one set of riser and test bushing for the transformer, which are only installed for conducting tests on the transformer body, and these two devices are used for testing the transformer body and do not follow the subsequent operation of the transformer, with high costs, thus without the riser and test bushing, the subsequent several processes after standing still cannot be carried out, so the transformer oil filtering work cannot be carried out simultaneously. On average, it takes 24 hours of construction for one transformer, and it takes 8 days to complete one transformer, which is time-consuming and laborious. Summary of the Invention

[0003] To solve the above problems, the present invention discloses an efficient oil filtering process for 110KV oil-immersed transformers, which effectively saves time and improves construction efficiency.

[0004] The specific solution is as follows:

[0005] The efficient oil filtering process for 110KV oil-immersed transformers is applicable to efficient oil filtering of multiple oil-immersed transformers. It is characterized in that it includes the operations of evacuating, injecting oil, oil circulation, standing still, conducting experiments, pumping out oil, removing test bushings, installing cable heads, and injecting oil in sequence. When the first transformer is equipped with a test bushing, oil circulation is carried out, and at the same time, the operations of evacuating, injecting oil, oil circulation, and standing still of the second transformer without installing bushings are started. At this time, the first transformer continues the subsequent operations of conducting experiments, pumping out oil, and removing test bushings. After the first transformer completes the whole set of operations, the removed test bushing is given to the second transformer that has completed the standing still operation. At the same time, the operations of evacuating, injecting oil, oil circulation, and standing still of the third transformer without installing bushings are started, and so on, alternating operations continuously.

[0006] As a further improvement of the present invention, the specific steps of filtering oil for the oil-immersed transformer are as follows:

[0007] S1: Removing the blind plate of the oil-immersed transformer, releasing nitrogen, 0.5 days;

[0008] S2: Installing the riser and test bushing of the oil-immersed transformer, 0.5 days;

[0009] S3: Installing the pressure relief valve, temperature control, and gas relay of the oil-immersed transformer; 0.5 days

[0010] S4: Preparation for oil filling of the oil-immersed transformer begins. The transformer starts to be evacuated. When the vacuum degree of the transformer oil tank reaches 133 Pa during evacuation (the evacuation time is about 24 hours), continue to evacuate and maintain for more than 2 hours.

[0011] S5: After maintaining the vacuum for more than 2 hours, start vacuum oil filling. The oil filling volume per hour is less than 5000 L. If the oil filling speed is too fast, the oil will impact the oil tank, generating acetylene and also producing bubbles, which will cause static electricity and damage the internal insulation performance of the core. The transformer oil capacity of a 31.5 MVA transformer is 12.9 tons, with a total of 12.9 / 0.895 = 14.413407 m 3 ; The weight of the transformer oil of a 40 MVA transformer is 13.9 tons, 13.9 / 0.895 = 15.53073 m 3 . The nominal flow rate of the on-site vacuum oil filter is 50 L / min; The ideal oil filling time for a 31.5 MVA transformer is: 4.8 hours; The ideal oil filling time for a 40 MVA transformer is: 5.18 hours; During actual on-site oil filling, since the oil filling speed cannot be too high at the beginning and the efficiency of the oil filling machine cannot work at full load, the actual oil filling time is much longer than the ideal time.

[0012] S6: After filling with oil, maintain the vacuum degree for more than 4 hours, and then release the vacuum;

[0013] S7: After releasing the vacuum, conduct an oil sample test;

[0014] S8: Refill the oil. After the vacuum oil filling is completed, add oil to the conservator through the oil injection and drainage connecting pipe on the gas collecting box of the conservator. When adding oil, open the butterfly valves at both ends of the gas relay, and at the same time open the air release plug on the butterfly valve at the end of the oil injection and drainage connecting pipe. After the added oil overflows, close the plug and open the butterfly valve to exhaust the gas in the oil filling pipeline. After the oil is filled to slightly higher than the normal oil level, close the butterfly valve and remove the oil injection connecting pipe.

[0015] S9: After filling with oil, let it stand for 24 hours, and then open the air release plugs on the upper parts such as the bushings, coolers (radiators), connecting pipes, etc. and the exhaust nozzles on the diaphragm in the conservator to exhaust air. Close the plugs when the oil overflows. Adjust the oil level according to the final oil temperature and oil level curve (performed through the oil injection and drainage pipe on the gas collecting box of the conservator, that is, the one with the butterfly valve), and then take an oil sample test, which should meet the requirements of U≥40 kV, dielectric loss factor tgδ<0.5% at 90℃, and water content less than or equal to 20 mg / kg.

[0016] S10: Conduct tests on the transformer oil breakdown voltage, insulation resistance, absorption ratio, on-load voltage regulation, transformer turns ratio, transformer DC resistance, dielectric loss of the transformer together with the bushings, and high and low voltage insulation breakdown voltage;

[0017] S11: After all the above work is completed, drain the oil into the oil tank provided by the manufacturer. Wait until the oil is released below the interface of the outgoing line device, then remove the elevated seat and the test bushing. After removal, plug the blind plate. After the removal is completed, perform secondary oil injection, and then plug it.

[0018] As a further improvement of the present invention, in step S7, if the oil sample test result is U ≤ 30 kV, hot oil circulation should be carried out. After circulation, vacuum pumping is carried out, and finally the oil meets the test result of U ≥ 40 kV, the dielectric loss factor tgδ < 0.5% at 90 °C, and the water content is less than or equal to 20 mg / kg.

[0019] As a further improvement of the present invention, if the body of the transformer is severely damp during storage or internal inspection, drying treatment should be carried out. When drying without oil, the winding temperature shall not exceed 93 °C. When drying with oil, the upper layer oil temperature shall not exceed 85 °C.

[0020] As a further improvement of the present invention, when drying after hot oil circulation, the oil temperature at the outlet of the oil tank is 70 °C + 5 °C, the circulation time is not less than 20 h, and the full amount of oil is circulated 2 - 3 times; finally, the oil quality meets the requirements of U ≥ 40 kV, the dielectric loss factor tgδ < 0.5% at 90 °C, and the water content is less than or equal to 20 mg / kg.

[0021] As a further improvement of the present invention, the transformer oil tank and the conservator can withstand a static pressure of 30 kPa applied on the highest oil surface for 24 h continuously without leakage and damage.

[0022] As a further improvement of the present invention, during the sealing performance test of the transformer oil tank and the conservator, close the valve between the pressure relief valve and the oil tank. At the same time, the pressure relief valve with a locking device is in the locked state; after the sealing performance test is completed, open the valve between the pressure relief valve and the oil tank, and at the same time, remove the locking device of the pressure relief valve with a locking device.

[0023] As a further improvement of the present invention, during the vacuum pumping process, if the vacuum degree rises slowly or the leakage rate is greater than 34 Pa / h, it indicates that there is a leakage situation. Check the leakage points of the relevant pipelines and the installation parts of each component on the transformer and deal with them in time.

[0024] As a further improvement of the present invention, the reference method for checking the leakage point is as follows:

[0025] (1) Listen carefully to whether there is a squeaking air intake sound at the connection. The place with the sound is the leakage part.

[0026] (2) Light a mosquito coil and let its smoke move along the suspected installation parts. When checking the upper part, use a plate-like object to block the smoke so that it does not leave the inspection part. When it is found that the smoke is sucked inwards and tilted, this position is the leakage point (please pay attention to fire prevention when using this method).

[0027] The beneficial effects of the present invention are as follows: It is suitable for the oil filtering operation of multiple oil-immersed transformers. While the oil circulation is carried out on the previous transformer equipped with a test bushing, the vacuum pumping, oil injection, oil circulation, and standing operations of the subsequent transformer without a bushing are started simultaneously. This process for the subsequent transformer takes about 2 days. At the same time, the subsequent steps of doing experiments, pumping oil, and removing the bushing for the previous transformer also take about 2 days. In this way, it is just possible to start the subsequent experiments, pumping oil, and removing the test bushing steps for the subsequent transformer, effectively saving the time for the subsequent transformer to wait for the previous one to do experiments, pump oil, and remove the test bushing, and improving the construction efficiency. Description of the Drawings

[0028] Figure 1 It is the front view of the oil-immersed transformer in the present invention.

[0029] Figure 2 It is the right view of the oil-immersed transformer in the present invention.

[0030] List of Reference Numerals:

[0031] 1 - High-voltage A riser, 2 - High-voltage B riser, 3 - High-voltage C riser, 4 - Test bushing. Embodiment

[0032] The following further clarifies the present invention in conjunction with the drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0033] As shown in the figure, the 110KV oil-immersed transformer high-efficiency oil filtering process is applicable to the high-efficiency oil filtering of multiple oil-immersed transformers, including the operations of vacuum pumping, oil injection, oil circulation, standing, doing experiments, pumping oil, removing the test bushing, installing the cable head, and oil injection in sequence. While the oil circulation is carried out on the first transformer equipped with a test bushing, the vacuum pumping, oil injection, oil circulation, and standing operations of the second transformer without a bushing are started simultaneously. At this time, the first transformer continues the subsequent operations of doing experiments, pumping oil, and removing the test bushing. After the first transformer completes the whole set of operations, the removed test bushing is given to the second transformer that has completed the standing operation. At the same time, the vacuum pumping, oil injection, oil circulation, and standing operations of the third transformer without a bushing are started, and so on for continuous alternating operations.

[0034] In this embodiment, the specific steps of the oil filtering of the oil-immersed transformer are as follows:

[0035] S1: Remove the blind plate of the oil-immersed transformer, release nitrogen, 0.5 days;

[0036] S2: Install the riser and test bushing of the oil-immersed transformer, 0.5 days;

[0037] S3: Installation of the pressure relief valve, temperature controller, and gas relay of the oil-immersed transformer; 0.5 day

[0038] S4: Prepare for oil injection of the oil-immersed transformer. The transformer starts to be evacuated. When the vacuum degree of the transformer oil tank reaches 133 Pa (the evacuation time is about 24 hours), continue to evacuate for more than 2 hours.

[0039] S5: After maintaining the vacuum for more than 2 hours, start vacuum oil injection, and the oil injection volume per hour is less than 5000 L; if the oil injection speed is too fast, the oil will impact the oil tank to generate acetylene and also produce bubbles, resulting in static electricity and damaging the internal insulation performance of the core. The transformer oil capacity of a 31.5 MVA transformer is 12.9 tons, with a total of 12.9 / 0.895 = 14.413407 m 3 ; the weight of the transformer oil of a 40 MVA transformer is 13.9 tons, 13.9 / 0.895 = 15.53073 m 3 . The nominal flow rate of the on-site vacuum oil filter is 50 L / min; the ideal oil injection time for a 31.5 MVA transformer is: 4.8 hours; the ideal oil injection time for a 40 MVA transformer is: 5.18 hours; during actual on-site oil injection, since the oil injection speed cannot be too high at the beginning and the efficiency of the oil injection machine cannot work at full load, the actual oil injection time is much longer than the ideal time.

[0040] S6: After filling with oil, maintain the vacuum degree for more than 4 hours, and then release the vacuum;

[0041] S7: After releasing the vacuum, conduct an oil sample test;

[0042] S8: Refill the oil. After the vacuum oil injection is completed, add oil to the conservator through the oil injection and drainage connecting pipe on the conservator gas collection box. When adding oil, open the butterfly valves at both ends of the gas relay, and at the same time open the air release plug on the butterfly valve at the end of the oil injection and drainage connecting pipe. After the added oil overflows, close the plug and open the butterfly valve to remove the gas in the oil injection pipeline. After the oil is filled to slightly higher than the normal oil level, close the butterfly valve and remove the oil injection connecting pipe.

[0043] S9: After filling with oil, let it stand for 24 hours, and then open the air release plugs on the upper parts such as the bushings, coolers (radiators), and connecting pipes, and the exhaust nozzles on the diaphragm in the conservator to exhaust air. Close the plugs when the oil overflows. Adjust the oil level according to the final oil temperature and oil level curve (through the oil injection and drainage pipe on the conservator gas collection box, that is, the one with the butterfly valve), and then take an oil sample test, which should meet the requirements of U ≥ 40 kV, tgδ < 0.5% at 90 °C for the dielectric loss factor, and the water content is less than or equal to 20 mg / kg.

[0044] S10: Conduct tests on the transformer oil withstand voltage, insulation resistance, absorption ratio, on-load voltage regulation, transformer turns ratio, transformer DC resistance, dielectric loss of the transformer together with the bushings, and high and low voltage insulation withstand voltage;

[0045] S11: After all the above work is completed, drain the oil into the oil tank provided by the manufacturer. Wait until the oil is released below the interface of the outgoing line device, then remove the riser and the test bushing. After removal, plug the blind flange. After the removal is completed, perform secondary oil injection, and then plug it.

[0046] In this embodiment, in step S7, if the oil sample test result is U ≤ 30 kV, hot oil circulation should be carried out. After circulation, vacuum pumping should be carried out. Finally, make the oil meet the test results of U ≥ 40 kV, dielectric loss factor tgδ < 0.5% at 90 °C, and water content less than or equal to 20 mg / kg.

[0047] In this embodiment, if the core is severely damp during storage or internal inspection, drying treatment should be carried out. When drying without oil, the winding temperature shall not exceed 93 °C. When drying with oil, the upper layer oil temperature shall not exceed 85 °C.

[0048] In this embodiment, when drying after hot oil circulation, the oil temperature at the outlet of the oil tank is 70 °C + 5 °C, the circulation time is not less than 20 h, and the total oil volume is circulated 2 - 3 times; finally, make the oil quality meet the requirements of U ≥ 40 kV, dielectric loss factor tgδ < 0.5% at 90 °C, and water content less than or equal to 20 mg / kg.

[0049] In this embodiment, the transformer oil tank and conservator can withstand a static pressure of 30 kPa applied on the highest oil surface, and the test time is continuous for 24 h without leakage and damage.

[0050] In this embodiment, during the seal performance test of the transformer oil tank and conservator, close the valve between the pressure relief valve and the oil tank. At the same time, the pressure relief valve with a locking device is in the locked state; after the seal performance test is completed, open the valve between the pressure relief valve and the oil tank. At the same time, remove the locking device of the pressure relief valve with a locking device.

[0051] In this embodiment, during the vacuum pumping process, if the vacuum degree rises slowly or the leakage rate is greater than 34 Pa / h, it indicates that there is a leakage situation. Check the leakage points of the relevant pipelines and the installation parts of each component on the transformer and deal with them in time.

[0052] In this embodiment, the reference method for checking the leakage point is as follows:

[0053] (1) Listen carefully to whether there is a squeaking air intake sound at the connection. The location with the sound is the leakage part.

[0054] (2) Light a mosquito coil and let the smoke move along the suspected installation parts. When checking the upper part, use a plate to block the smoke so that it does not leave the inspection part. When it is found that the smoke is sucked in and tilted, this position is the leakage point (please pay attention to fire prevention when using this method).

[0055] The technical means disclosed in the solution of the present invention are not limited to those disclosed in the above embodiments, but also include technical solutions formed by any combination of the above technical features. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. The high-efficiency oil filtering process for 110KV oil-immersed transformers is applicable to the high-efficiency oil filtering of multiple oil-immersed transformers, and is characterized in that, It includes the operations of vacuum pumping, oil injection, oil circulation, standing still, conducting experiments, oil pumping, removing the test bushing, installing the cable head, and oil injection in sequence. When the first transformer is equipped with a test bushing, oil circulation is carried out, and at the same time, the operations of vacuum pumping, oil injection, oil circulation, and standing still of the second transformer without a bushing are started. At this time, the first transformer continues the subsequent operations of conducting experiments, oil pumping, and removing the test bushing. After the first transformer completes the whole set of operations, the removed test bushing is given to the second transformer that has completed the standing still operation. At the same time, the operations of vacuum pumping, oil injection, oil circulation, and standing still of the third transformer without a bushing are started, and so on, alternating the operations continuously; The specific steps for filtering the oil of the oil-immersed transformer are as follows: S1: Remove the blind plate of the oil-immersed transformer and release nitrogen; S2: Install the riser and test bushing of the oil-immersed transformer; S3: Install the pressure relief valve, temperature control, and gas relay of the oil-immersed transformer; S4: Start the oil injection preparation work of the oil-immersed transformer. The transformer starts to pump vacuum. When the vacuum degree of the transformer tank reaches 133 Pa, continue to pump vacuum for more than 2 hours; S5: After maintaining the vacuum for more than 2 hours, start vacuum oil injection. The oil injection volume per hour is less than 5000 L. If the oil injection speed is too fast, the oil will impact the tank to generate acetylene and also generate bubbles, resulting in static electricity and damaging the internal insulation performance of the core; S6: After filling with oil, maintain the vacuum degree for more than 4 hours, and then release the vacuum; S7: After releasing the vacuum, conduct an oil sample test; S8: Refill the oil. After the vacuum oil injection is completed, add oil to the conservator from the oil injection and drainage connection pipe on the gas collection box of the conservator. When adding oil, open the butterfly valves at both ends of the gas relay, and at the same time open the air release plug on the butterfly valve at the end of the oil injection and drainage connection pipe. After the added oil overflows, close the plug and open the butterfly valve, that is, discharge the gas in the oil injection pipeline. After the oil is injected to slightly higher than the normal oil level, close the butterfly valve and remove the oil injection connection pipe; S9: After filling with oil, let it stand for 24 hours, and then open the air release plugs on the upper parts of the bushings, coolers, and connecting pipes and the exhaust nozzles on the film in the conservator to exhaust gas. Close the plugs when the oil overflows; Adjust the oil level according to the final oil temperature and oil level curve, and take an oil sample test; S10: Conduct the tests of the oil withstand voltage, insulation resistance, absorption ratio, on-load voltage regulation, transformer turns ratio, transformer DC resistance, dielectric loss of the transformer together with the bushing, and high and low voltage insulation withstand voltage of the transformer; S11: After all the above work is completed, drain the oil into the oil tank provided by the manufacturer. Wait until the oil is released below the interface of the outgoing line device, remove the riser and test bushing, conduct blind plate sealing after removal, conduct secondary oil injection after the removal is completed, and then conduct sealing.

2. The high-efficiency oil filtering process for the 110KV oil-immersed transformer according to claim 1, characterized in that: In step S7, if the result of the oil sample test is U≤30 kV, hot oil circulation should be carried out. After circulation, vacuum pumping is carried out again, and finally the oil should meet the test results of U≥40 kV, dielectric loss factor tgδ<0.5% at 90℃, and water content less than or equal to 20 mg / kg.

3. The high-efficiency oil filtering process for the 110KV oil-immersed transformer according to claim 2, wherein: When the core is seriously damp during storage or internal inspection, drying treatment should be carried out. When drying without oil, the winding temperature shall not exceed 93℃. When drying with oil, the upper layer oil temperature shall not exceed 85℃.

4. The high-efficiency oil filtering process for the 110KV oil-immersed transformer according to claim 2, characterized in that: When drying using hot oil circulation, the oil temperature at the tank outlet is 70°C + 5°C, the circulation time is not less than 20 h, and the full oil volume is circulated 2 - 3 times; finally, the oil quality reaches the requirements of U ≥ 40 kV, tgδ < 0.5% at 90°C, and the water content is less than or equal to 20 mg / kg.

5. The high-efficiency oil filtering process of the 110KV oil-immersed transformer according to claim 1, characterized in that: The transformer tank and conservator can withstand a static pressure of 30 kPa applied on the highest oil surface for 24 h continuously without leakage or damage.

6. The high-efficiency oil filtration process for the 110KV oil-immersed transformer according to claim 1 is characterized in that: When conducting the sealing performance test of the transformer tank and conservator, close the valve between the pressure relief valve and the tank. At the same time, the pressure relief valve with a locking device is in the locked state; after the sealing performance test is completed, open the valve between the pressure relief valve and the tank, and at the same time, remove the locking device from the pressure relief valve with a locking device.

7. The high-efficiency oil filtering process for the 110KV oil-immersed transformer according to claim 1, characterized in that: During the vacuum pumping process, if the vacuum degree rises slowly or the leakage rate is greater than 34 Pa / h, it indicates a leakage situation. Check the leakage points of the relevant pipelines and the installation parts of each component on the transformer and deal with them in a timely manner.

8. The high-efficiency oil filtering process for the 110KV oil-immersed transformer according to claim 7, characterized in that: The reference method for checking the leakage points is as follows: (1) Listen carefully to whether there is a squeaking air intake sound at the connection. The location with the sound is the leakage part. (2) Light a mosquito coil and let the smoke move along the suspected installation parts. When checking the upper part, use a plate to block the smoke so that it does not leave the inspection part. When it is found that the smoke is sucked in and tilted, this position is the leakage point.

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