As a professional manufacturer in the power transmission and distribution equipment industry, JINSHANMEN TECHNOLOGY CO., LTD has rich experience in the maintenance and operation of transformers. The company mainly produces oil immersed power transformers, dry-type power transformers, oil immersed three-dimensional coiled power transformers, dry-type three-dimensional coiled power transformers, mining explosion-proof dry-type transformers, mining explosion-proof mobile substations, amorphous alloy power transformers, on load capacity regulating power transformers, locomotive dry-type transformers, as well as prefabricated substations, modular substations, wind energy box type substations, high and low voltage switchgear and other transmission and distribution equipment. Among them, the oil immersed power transformer is widely used in various power supply scenarios due to its excellent insulation and heat dissipation performance, and the 11kv power transformer, as a common type of oil immersed power transformer, is particularly important for oil filtering and filling operations to ensure long-term safe and stable operation.
I. The Importance of Transformer Oil Filtering and Filling
Transformer insulating oil plays two core roles: insulation and heat dissipation. To ensure the safe operation of transformers, especially oil immersed power transformers and 11kv power transformers, the insulating oil must have good insulation performance, including high breakdown voltage and low dielectric loss factor. The main factors affecting the breakdown voltage of insulating oil are moisture, impurities, gas and other pollutants.
During the operation of oil immersed power transformers, or during the long-term storage of new oil, it is inevitable that moisture invades. For 11kv power transformers operating in harsh environments, the insulation oil is more likely to absorb moisture and dust. In addition, the insulating oil of the oil immersed power transformer will produce carbon black under the action of electric arc during operation, and sludge and other impurities will be generated due to oil aging. These pollutants will significantly reduce the performance of insulating oil, damage the internal insulation structure of the transformer, and even lead to equipment failure and safety accidents. Therefore, regular oil filtering and standardized oil filling are essential maintenance links for oil immersed power transformers, including 11kv power transformers.
II. Core Equipment for Transformer Oil Filtering: Vacuum Oil Filter Device
To effectively remove moisture, gas and impurities in insulating oil and restore the performance of insulating oil, the vacuum oil filter device is the most commonly used and efficient purification equipment. It is widely used in the maintenance of oil immersed power transformers, especially 11kv power transformers. It not only can efficiently purify insulating oil, but also has functions such as hot oil circulation, vacuum oil filling and vacuum pumping for electrical equipment, which provides comprehensive protection for the safe operation of oil immersed power transformers.
1. Working Principle of Vacuum Oil Filter Device
Before oil filtering, under the action of pressure difference, the oil enters the primary filter from the oil inlet to filter out coarse impurities. The oil containing fine particles is heated by the heating pipe and then enters the vacuum separation tank. Under the action of the special degassing element of the vacuum cylinder, the insulating oil is fully film-formed, and the oil is divided and recombined at the same time. In the condenser, tiny water molecules coalesce into larger water droplets. When the vacuum degree reaches -0.09Mpa, the boiling point of water is only about 40℃, and the oil has been heated and stabilized at 60℃. At this time, the water in the oil boils and escapes to realize oil-water separation. The remaining water vapor and harmful gases in the oil are discharged by the vacuum pump together.
The oil after removing moisture is discharged by the oil discharge pump after filtering out fine impurities through the precision filter, completing a working cycle. After a short period of circulation, the moisture, gas and impurities in the oil can be completely removed, meeting the use standards of insulating oil for oil immersed power transformers and 11kv power transformers.
2. Vacuum Oil Filtering Operation Process
The standard operation of vacuum oil filtering is the key to ensuring the purification effect. It is especially important for the maintenance of oil immersed power transformers and 11kv power transformers. The specific process is divided into three stages: pre-startup inspection and preparation, vacuum oil filtering operation, and shutdown operation.
2.1 Pre-startup Inspection and Preparation
① Place the equipment stably, connect the oil inlet pipe of the vacuum oil filter device to the oil outlet of the oil tank to be filtered, and connect the oil outlet of the equipment to the oil inlet of the oil storage barrel. When pumping oil from an oil tank or barrel with a lot of sediment, do not insert the oil pipe directly to the bottom; if necessary, add a pre-filter to prevent excessive impurities from damaging the filter element.
② Connect the cooler to the cooling power supply, and carry out small-flow water circulation in accordance with the principle of bottom-in and top-out. If the equipment is used for a short time, the water content in the oil is not high, or it is used in winter, cooling water can be omitted.
③ Open the electric control box, select the corresponding three-phase cable according to the total power, connect the power supply, and reliably ground the vacuum oil filter device to ensure safe operation, which is especially critical for the oil filtering operation of 11kv power transformers.
④ Start the power supply; if the alarm sounds, it indicates that the phase sequence of the incoming power line is reversed (some equipment has no alarm, and the motor reverse rotation can be observed to judge the phase sequence reversal). It only needs to swap any two of the three-phase lines to solve the problem.
⑤ Place safety barriers in the working area, and equip with fire-fighting water sources and fire-fighting equipment to prevent safety accidents during the oil filtering process of oil immersed power transformers.
2.2 Vacuum Oil Filtering Operation
① For the oil filtering of the oil storage tank, the tank oil filtering method can be adopted: filter all the oil to be filtered into the oil storage tank through the high-vacuum oil filter. If the oil storage tank is used for self-circulation, the oil tank must be well sealed to prevent moisture and impurities in the air from entering, which will affect the insulation performance of the oil for oil immersed power transformers.
② First, close the oil inlet and outlet valves, as well as other drain valves, sampling valves, drain valves and air mixing valves connected to the outside world. Then start the vacuum pump on the control panel to evacuate the oil filter device. When the vacuum degree rises to the set value (observed through the vacuum gauge on the device), and the vacuum degree is between -0.06 and -0.08Mpa, slowly open the oil inlet valve to start oil feeding. Note: the valve should be opened gradually to avoid damaging the primary filter element due to sudden increase of impact force.
③ Observe the observation window on the vacuum pipe. When the oil enters the vacuum tank and the oil level reaches the middle position of the observation window, first open the oil outlet valve, then start the oil pump, and the oil outlet will start to discharge oil. Note: if the oil outlet valve is not opened before starting the oil pump, the pressure at the oil outlet will be too high, leading to equipment shutdown or even damage to the filter device, which will affect the normal maintenance of the 11kv power transformer.
④ Appropriately adjust the oil inlet and outlet valves. When the oil inlet and outlet reach basic balance, turn on the heating switch, start the heater, and adjust the temperature control value, generally 55-65℃ is appropriate. For two-stage heating equipment, whether to start the other group of heaters can be determined according to the amount of oil to be treated and the ambient temperature. The heating temperature of the second-stage heater is 3-5℃ higher than that of the first-stage heater (two-stage heating can also be turned on at the initial stage of circulation to facilitate rapid heating; after the overall oil temperature reaches above 50℃, one group can be turned off to save electricity).
⑤ After maintaining circulating filtration for a period of time, open the sampling valve to take an oil sample (before sampling, drain a small amount of oil to flush the sampling port and sampling oil pipe, and the sampling bottle also needs to be cleaned with oil) until the relevant tests of the insulating oil meet the standards of oil immersed power transformers and 11kv power transformers.
2.3 Shutdown Operation
① Before shutdown, turn off the heater 3-5 minutes in advance, and keep the oil circulating for a period of time to reduce the temperature to below 50℃, otherwise the heater will be easily damaged, which will affect the subsequent oil filtering operation of the oil immersed power transformer.
② First close the oil outlet valve of the oil tank, then close the oil inlet valve of the vacuum oil filter. After draining the residual oil in the equipment as much as possible, first close the oil discharge pump, then close the oil outlet valve.
③ After draining the oil in the oil pipe, close the vacuum pump, open the air inlet valve to release the vacuum.
④ Open the valve at the lower end of the condenser to drain the residual oil or water inside; if the equipment is not used for a long time, drain the cooling water (be sure to drain the cooling water in winter to avoid freezing and cracking). Close the valve after draining.
⑤ Open the drain valve to drain the residual oil in the tank, then turn off the power supply. After shutdown, clean the equipment to ensure that it can be used normally in the next oil filtering of the 11kv power transformer.
III. Key Points of Transformer Oil Filling (Applicable to Oil Immersed Power Transformers)
After the insulating oil is filtered and meets the standard, it is necessary to fill the oil into the oil immersed power transformer, especially the 11kv power transformer, in a standardized manner. The correct oil filling operation can avoid air and moisture entering the transformer, and ensure the insulation performance of the equipment.
① Before oil filling, check the tightness of the transformer oil tank to ensure that there is no oil leakage, which is the basic guarantee for the safe operation of the oil immersed power transformer.
② The filtered insulating oil should be left standing for a period of time to avoid air bubbles remaining in the oil; the oil filling temperature should be controlled at 40-60℃, which is conducive to the flow of the oil and the discharge of air in the transformer.
③ For oil immersed power transformers such as 11kv power transformers, vacuum oil filling is recommended. During the oil filling process, the vacuum pump should be kept running to ensure that the inside of the transformer is in a vacuum state, which can effectively remove the air in the transformer and prevent the insulation performance from being affected by air bubbles.
④ The oil filling speed should be controlled properly, generally 3-6t/h. If the vacuum degree drops, the oil filling speed should be reduced appropriately to avoid the vacuum degree being too low and air entering.
⑤ When the oil level reaches the standard position (observed through the oil level gauge of the transformer), stop oil filling, close the oil filling valve, and let the oil stand for 24-48 hours to discharge the residual air in the oil and the transformer, so as to ensure the stable operation of the oil immersed power transformer and the 11kv power transformer.
IV. Summary
Transformer oil filtering and filling are important links to ensure the safe and stable operation of oil immersed power transformers and 11kv power transformers. By using the vacuum oil filter device to purify the insulating oil in accordance with the standard operation process, the moisture, gas and impurities in the oil can be effectively removed, and the insulation performance of the oil can be restored. The standardized oil filling operation can avoid the damage of air and moisture to the transformer internal insulation, thus extending the service life of the oil immersed power transformer and ensuring the safe and stable operation of the power supply system.
As a professional manufacturer of power transmission and distribution equipment, JINSHANMEN TECHNOLOGY CO., LTD has rich experience in the production and maintenance of oil immersed power transformers and 11kv power transformers. We are committed to providing high-quality transformers and professional technical guidance to help customers solve various problems in the operation and maintenance of transformers.