A transformer oil on-line vacuum degassing device

Abstract

A kind of transformer oil on-line vacuum degassing device, including buffer tank, cylinder and vacuum pump, piston is arranged in cylinder, the lower end of cylinder is fixedly connected guide bushing, guide bushing is equipped with guide rod, the upper end of guide rod is fixedly connected with piston, spring for driving piston up is sleeved on guide rod, the upper end of cylinder is communicated with the bottom of buffer tank, vacuum pump and the upper end of transformer oil tank by first pipeline, second pipeline and third pipeline respectively, the lower end of transformer oil tank is communicated with the upper end of buffer tank by fourth pipeline, first electric valve is installed on first pipeline.The utility model is used to solve the problem that vacuum degassing method is easy to form gas dead angle and produce foam, leading to the problem that degassed gas is mixed into transformer oil and pipeline residual gas again with oil return.

Description

Technical Field

[0001] This utility model belongs to the technical field of transformer oil treatment and power equipment condition maintenance, and relates to an online vacuum degassing device for transformer oil. Background Technology

[0002] Transformers are critical power transmission and transformation equipment in power systems. Transformer oil, as the core insulating and cooling medium within the transformer, is subject to decomposition during long-term operation due to insulation aging, localized overheating, or internal discharge. This decomposition produces gases such as hydrogen and methane, which dissolve in the oil. Detecting these dissolved gases allows for assessment of the transformer's internal condition. Oil-gas separation (degassing) is a crucial prerequisite for accurate detection, and the performance of the degassing device directly determines the reliability of subsequent test results. Current transformer degassing technologies mainly include polymer membrane permeation degassing, dynamic headspace degassing, and vacuum degassing. However, each technology has significant shortcomings. 1. Polymer membrane permeation degassing method: This method relies on the selective permeation of polymer membranes to achieve oil-gas separation. However, the oil-gas equilibrium time is long and the degassing efficiency is low, making it difficult to quickly capture gas signals generated by sudden problems inside the transformer. Furthermore, polymer membranes are easily contaminated and aged by impurities in the oil, requiring frequent replacement, which increases maintenance costs and equipment downtime.

[0003] 2. Dynamic headspace degassing method: By introducing inert gas into the oil sample to replace dissolved gas, the degassing time is shortened. However, the introduction of inert gas increases the system cost and complexity. Moreover, the oil sample after replacement cannot be returned to the transformer tank, resulting in oil waste. At the same time, fluctuations in gas purity may also interfere with the detection accuracy.

[0004] 3. Vacuum degassing method: This method has high degassing efficiency and thorough oil-gas separation, making it a widely used technology. However, existing vacuum degassing devices still have the following problems: some devices use unreasonable cylinder layouts (such as horizontal cylinders), which can easily create gas dead zones due to tilted installation, or cause foaming during oil sample flow due to pipeline design problems, resulting in misjudgment of liquid level detection. This allows the degassing gas to re-mix with the transformer oil with the return oil, contaminating the oil sample. When the oil sample is returned to the transformer, if there is residual gas in the pipeline, it may cause the transformer protection system to malfunction, posing a risk of equipment shutdown.

[0005] Therefore, there is an urgent need to develop an online vacuum degassing device for transformer oil that has a reasonable structure, high efficiency and stability in degassing, can avoid gas residue and oil contamination, and is easy to operate and maintain, so as to solve the defects of existing technologies and ensure the safe operation of transformers. Utility Model Content

[0006] The purpose of this invention is to provide an online vacuum degassing device for transformer oil, which solves the problem that vacuum degassing methods easily create gas dead zones and generate foam, causing the degassed gas to be re-mixed into the transformer oil and residual gas in the pipeline along with the return oil.

[0007] To solve the above problems, the technical solution of this utility model is as follows: An online vacuum degassing device for transformer oil includes a buffer tank, a cylinder, and a vacuum pump. A piston is housed within the cylinder. A guide sleeve is fixedly connected to the lower end of the cylinder. A guide rod is housed within the guide sleeve, and its upper end is fixedly connected to the piston. A spring for driving the piston upwards is sleeved on the guide rod. The upper end of the cylinder is connected to the bottom of the buffer tank, the vacuum pump, and the upper end of the transformer oil tank via a first pipe, a second pipe, and a third pipe, respectively. The lower end of the transformer oil tank is connected to the upper end of the buffer tank via a fourth pipe. A first electric valve is installed on the first pipe. A second electric valve and a pressure sensor are installed on the second pipe. A vent pipe is connected to the second pipe between the second electric valve and the vacuum pump. A third electric valve is installed on the vent pipe. A fourth electric valve is installed on the third pipe. The cylinder has four electric valves. The lower end of the cylinder is connected to a vacuum pump via a suction pipe. The suction pipe is connected to an intake pipe via a pipeline, and a fifth electric valve is installed on the suction pipe. A sixth electric valve is installed on the intake pipe. An oil pump is installed on the fourth pipeline. A buffer pipe with a diameter larger than the second pipeline is connected to the second pipeline between the second electric valve and the vacuum pump. A level switch is installed on the buffer pipe. The lower end of the buffer pipe is connected to a buffer tank via a return pipe. A seventh electric valve is installed on the return pipe. The system also includes a controller. The level switch and pressure sensor are connected to the controller input. The first, second, third, fourth, fifth, sixth, and seventh electric valves and the vacuum pump are all connected to the controller output.

[0008] Furthermore, an oil filter is installed on the fourth pipe.

[0009] Furthermore, a contact block is fixedly connected to the guide rod, and a first limit switch and a second limit switch are provided on one side of the contact block. The first limit switch and the second limit switch are alternately triggered by the contact block, and the first limit switch and the second limit switch are connected to the input terminal of the controller.

[0010] Furthermore, an insulation layer is provided on the outside of the buffer tank, an electric heater is provided at the bottom of the buffer tank, and a temperature sensor is provided inside the buffer tank. The temperature sensor is connected to the input terminal of the controller, and the electric heater is connected to the output terminal of the controller.

[0011] Furthermore, a high-level sensor and a low-level sensor are respectively installed at the upper and lower ends of the buffer tank, and the high-level sensor and the low-level sensor are connected to the input terminal of the controller.

[0012] Furthermore, an eighth electric valve is installed on the second pipe between the vent pipe and the vacuum pump. A fifth pipe is connected to the third electric valve. A sampling tank is connected to the fifth pipe. A gas detection device is connected to the sampling tank. A ninth electric valve and a tenth electric valve are installed on the fifth pipes on both sides of the sampling tank, respectively. The gas detection device is connected to the controller input terminal, and the ninth and tenth electric valves are connected to the controller output terminal.

[0013] Furthermore, an air filter is installed at one end of the vent pipe.

[0014] Furthermore, a throttle valve is installed on the extraction pipe, and a check valve is connected to one side of the throttle valve.

[0015] The beneficial effects of this utility model are as follows: 1. The vertical cylinder layout, combined with the oil filling design when the piston moves upward, avoids the gas dead zone of traditional horizontal cylinders; the buffer tube is linked with the liquid level switch to ensure that there are no cavities in the pipeline, prevent the gas from being released and mixed into the transformer oil with the return oil, ensure the cleanliness of the oil sample and the insulation performance of the transformer, and at the same time avoid the protection system from malfunctioning due to residual gas in the pipeline.

[0016] 2. By linking the pressure sensor with the controller, the vacuum pressure and holding time are precisely controlled to ensure that dissolved gases in the oil are fully extracted; the insulation layer of the buffer tank, the electric heater and the temperature sensor work together to maintain a suitable temperature for the oil sample and reduce the impact of ambient temperature on the degassing effect; the oil filter removes impurities, avoids component wear and gas extraction obstruction, and ensures long-term stable degassing.

[0017] 3. The oil sample is collected, degassed and returned in a closed loop, with no oil waste; the controller links various sensors and electric valves to realize a fully automatic process of "oil extraction-degasting-return-reset", without manual intervention; the buffer tank level sensor controls the oil pump to start and stop as needed, reducing energy consumption. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the structure of this utility model. Figure 2 This is a schematic diagram of the circuit connection of this utility model.

[0019] In the diagram: 1. Sampling tank; 2. Gas detection device; 3. Vacuum pump; 4. Oil filter; 5. Oil pump; 6. Insulation layer; 7. Buffer tank; 8. Electric heater; 9. High level sensor; 10. Low level sensor; 11. Throttling valve; 12. Guide rod; 13. Second limit switch; 14. Contact block; 15. First limit switch; 16. Spring; 17. Cylinder; 18. Piston; 19. Level switch; 20. Buffer tube; 21. Air filter; 22. Pressure sensor; 23. Temperature sensor; 91. First electric valve; 92. Second electric valve; 93. Third electric valve; 94. Fourth electric valve; 95. Fifth electric valve; 96. Sixth electric valve; 97. Seventh electric valve; 98. Eighth electric valve; 99. Ninth electric valve; 90. Tenth electric valve. Detailed Implementation

[0020] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0021] like Figure 1 and 2As shown, an online vacuum degassing device for transformer oil includes a buffer tank 7, a cylinder 17, and a vacuum pump 3. The cylinder 17 is vertically arranged, and a piston 18 is installed inside the cylinder 17. A guide sleeve is fixedly connected to the lower end of the cylinder 17, and a guide rod 12 is installed inside the guide sleeve. The upper end of the guide rod 12 is fixedly connected to the piston 18. A spring 16 for driving the piston 18 upward is sleeved on the guide rod 12. The upper end of the cylinder 17 is connected to the bottom of the buffer tank 7, the vacuum pump 3, and the upper end of the transformer oil tank through a first pipe, a second pipe, and a third pipe, respectively. The lower end of the transformer oil tank is connected to the upper end of the buffer tank 7 through a fourth pipe. A first electric valve 91 is installed on the first pipe, a second electric valve 92 and a pressure sensor 22 are installed on the second pipe, a vent pipe is connected to the second pipe between the second electric valve 92 and the vacuum pump 3, a third electric valve 93 is installed on the vent pipe, and a fourth electric valve 22 is installed on the third pipe. The cylinder body 17 has an electric valve 94. The lower end of the cylinder body 17 is connected to the vacuum pump 3 through a suction pipe. The suction pipe is connected to the air inlet pipe and is equipped with a fifth electric valve 95. The air inlet pipe is equipped with a sixth electric valve 96. The oil pump 5 is installed on the fourth pipe. A buffer pipe 20 with a diameter larger than the second pipe is connected to the second pipe between the second electric valve 92 and the vacuum pump 3. A liquid level switch 19 is installed on the buffer pipe 20. The lower end of the buffer pipe 20 is connected to the buffer tank 7 through a return pipe. A seventh electric valve 97 is installed on the return pipe. The system also includes a controller (such as an S7-200SMART series controller). The liquid level switch 19 and the pressure sensor 22 are connected to the input terminal of the controller. The first electric valve 91, the second electric valve 92, the third electric valve 93, the fourth electric valve 94, the fifth electric valve 95, the sixth electric valve 96, the seventh electric valve 97 and the vacuum pump 3 are all connected to the output terminal of the controller.

[0022] The working process of this utility model is as follows: Initially, the piston 18 inside the cylinder 17 is positioned at the upper end of the cylinder 17 under the force of the spring 16; the first electric valve 91 is open (to prepare for the extraction of oil samples from the buffer tank 7), the fifth electric valve 95 is closed (to prevent the vacuum pump 3 from prematurely extracting gas from the rod chamber of the cylinder 17), and the remaining electric valves (second, third, fourth, sixth, and seventh) are closed; this state ensures that when the vacuum pump 3 is started in the subsequent S1 step, it can accurately extract air from the rod chamber of the cylinder 17 to form a negative pressure.

[0023] S1: Oil sample extraction: The controller starts the vacuum pump 3, which draws air from the rod chamber of cylinder 17 through the suction pipe to form a negative pressure, driving piston 18 to move downward against the elastic force of spring 16; at the same time, transformer oil in buffer tank 7 is drawn into cylinder 17 through the first pipeline (first electric valve 91 is opened). When piston 18 moves down to the preset position (determined by subsequent second limit switch 13), the controller closes the first electric valve 91 and the fifth electric valve 95 to complete the quantitative extraction of oil sample.

[0024] S2: Vacuum degassing: The controller synchronously opens the second electric valve 92, and the vacuum pump 3 switches to the mode of extracting gas from the cylinder 17 and the buffer tube 20; the pressure sensor 22 monitors the pipeline pressure in real time. When the vacuum pressure reaches 5 kPa, the vacuum pump 3 stops and maintains the pressure for 60 seconds. The negative pressure environment breaks the gas dissolution balance in the oil, allowing dissolved gases such as hydrogen and methane to be fully extracted.

[0025] S3: Gas discharge and oil filling: The controller opens the sixth electric valve 96, and atmospheric air enters the rod chamber of the cylinder 17. The piston 18 moves upward under the action of the spring 16, pushing the oil sample in the cylinder 17 to the buffer tube 20. When the oil sample triggers the liquid level switch 19 on the buffer tube 20, the controller closes the second electric valve 92. At this time, the cylinder 17 and the third pipe are filled with oil, which can eliminate dead corners and cavities in the pipes, thereby avoiding gas residue.

[0026] S4: Oil sample return: The controller opens the fourth electric valve 94, and the piston 18 continues to move upward (the spring 16 continues to exert force), pushing the oil sample in the cylinder 17 back to the transformer oil tank through the third pipeline, realizing zero-loss circulation of the oil sample.

[0027] S5: Reset and Circulation: After the oil sample is completely returned, the controller opens the third electric valve 93 (vent pipe) and the seventh electric valve 97 (return pipe). The residual oil in the buffer pipe 20 flows back to the buffer tank 7 through the return pipe; the device returns to the initial state and repeats steps S1-S5 to achieve continuous degassing.

[0028] As can be seen, this utility model avoids the gas dead zone caused by the tilted installation of traditional horizontal cylinders by using the vertical layout of cylinder body 17 and the oil filling design when piston 18 moves upward; the diameter of buffer pipe 20 is larger than that of the second pipe, which reduces turbulence and foam when the oil sample flows; the liquid level switch 19 accurately triggers the electric valve to close, ensuring that there are no cavities in the pipeline and completely eliminating the risk of the extracted gas mixing into the transformer oil with the return oil.

[0029] Furthermore, an oil filter 4 is installed on the fourth pipeline. When the oil pump 5 starts to pump transformer oil into the buffer tank 7, the oil must first pass through the filter media (such as a high-precision filter screen) to remove impurities (such as metal shavings, insulating particles, etc.) before entering the buffer tank 7. This prevents impurities from entering the cylinder 17, wearing down the piston 18 seals, clogging the electric valve core, extending the service life of the device, and reducing the failure rate. The removal of impurities reduces their obstruction to gas evolution (such as incomplete degassing due to gas adsorption on the impurity surface), ensuring consistent degassing efficiency for different batches of oil samples and improving the repeatability of subsequent gas detection data.

[0030] Furthermore, a contact block 14 is fixedly connected to the guide rod 12. A first limit switch 15 and a second limit switch 13 are provided on one side of the contact block 14. The first limit switch 15 and the second limit switch 13 are alternately triggered by the contact block 14. The first limit switch 15 and the second limit switch 13 are connected to the input terminal of the controller. The first limit switch 15 and the second limit switch 13 detect and control the stroke of the piston 18. When the first limit switch 15 is triggered, it indicates that the transformer oil in the cylinder 17 has been completely discharged. When the contact block 14 triggers the second limit switch 13, it indicates that the piston 18 has descended to the preset position. The first limit switch 15 limits the upward limit of the piston 18 to prevent the spring 16 from over-extending or the piston 18 from hitting the top of the cylinder 17, thus protecting the mechanical structure. At the same time, it accurately determines whether the oil sample has been completely discharged, avoiding residual oil from affecting the next round of degassing. The second limit switch 13 precisely controls the downward distance of the piston 18 to ensure that the volume of oil sample extracted each time is consistent, avoiding differences in degassing efficiency caused by fluctuations in the amount of oil sample.

[0031] Furthermore, an insulation layer 6 is provided outside the buffer tank 7, an electric heater 8 is provided at the bottom of the buffer tank 7, and a temperature sensor 23 is provided inside the buffer tank 7. The temperature sensor 23 is connected to the input terminal of the controller, and the electric heater 8 is connected to the output terminal of the controller. The temperature sensor 23 monitors the oil sample temperature inside the buffer tank 7 in real time, and the data is transmitted to the controller. When the temperature is lower than the optimal temperature for gas evolution (e.g., 45°C), the controller starts the electric heater 8 to raise the oil sample temperature to 50°C (the temperature range with the lowest gas solubility). After the temperature reaches the set value, the controller turns off the electric heater 8. By utilizing the physical property that "temperature increases → gas solubility decreases", the gas evolution rate is greatly improved. The insulation layer 6 maintains a stable temperature inside the tank, avoiding the problem of a sharp drop in degassing efficiency caused by low temperatures in winter in traditional devices.

[0032] Furthermore, a high-level sensor 9 and a low-level sensor 10 are respectively installed at the upper and lower ends of the buffer tank 7, and these sensors are connected to the controller input. The high-level sensor 9 and low-level sensor 10 are used for real-time detection of the transformer oil level in the buffer tank 7. When the level is low, the controller controls the oil pump 5 to start, drawing transformer oil into the buffer tank 7. When the level is high, the controller controls the oil pump 5 to stop, maintaining the transformer oil level in the buffer tank 7 between the high-level sensor 9 and the low-level sensor 10. This prevents the oil pump 5 from running dry (damaging the pump body) due to excessively low oil level in the buffer tank 7 or from overflowing due to excessively high oil level, ensuring uninterrupted degassing of the device 24 hours a day.

[0033] Furthermore, an eighth electric valve 98 is installed on the second pipe between the vent pipe and the vacuum pump 3. A fifth pipe is connected to the third electric valve 93, and a sampling tank 1 is connected to the fifth pipe. A gas detection device 2 (such as InsulDGA-7A from Maisheng Intelligent Technology) is connected to the sampling tank 1. A ninth electric valve 99 and a tenth electric valve 90 are installed on the fifth pipes on both sides of the sampling tank 1, respectively. The gas detection device 2 is connected to the controller input, and the ninth and tenth electric valves 99 and 90 are connected to the controller output. Under normal conditions, the eighth electric valve 98 is in the open state. When it is necessary to detect the gas in the transformer oil, the following steps are followed: A1: Under normal conditions, the eighth electric valve 98 is open. When testing is required, the controller closes the eighth electric valve 98, opens the third, ninth, and tenth electric valves, starts the vacuum pump 3, and stops after 10 seconds. The sampling tank 1 is then rinsed with outside air (filtered by air filter 21) to eliminate interference from residual gas.

[0034] A2: After completing the oil sample extraction (S1), the controller closes the eighth electric valve 98; when entering the vacuum degassing step (S2), the gas released in the cylinder 17 enters the sampling tank 1 through the second pipe and the fifth pipe (the ninth and tenth electric valves are open); when the pressure in the sampling tank 1 is detected to reach 50 kPa, the controller closes the tenth electric valve 90 and stops the vacuum pump 3, and maintains the pressure for 1 minute to allow more gas to enter the sampling tank 1.

[0035] A3: One minute later, the controller closes the ninth electric valve 99 and opens the eighth electric valve 98, and the device continues to execute the S2-S5 degassing process; at the same time, the gas detection device 2 analyzes the composition and concentration of the gas in the sampling tank 1, and the data is transmitted to the controller.

[0036] A4: After the test is completed, repeat step A1 to purge sampling tank 1. After restoring normal pressure, close all relevant electric valves. This will not affect the normal degassing circulation of the device.

[0037] Gas sampling can be completed without disassembling the device, improving detection efficiency and avoiding the detection lag problem caused by the traditional device's "degassing followed by separate sampling". The sampling tank 1 cleaning and atmospheric pressure reset process eliminates cross-contamination.

[0038] Furthermore, an air filter 21 is installed at one end of the vent pipe. This prevents dust from entering the sampling canister 1 and adsorbing gas components, ensuring accurate gas detection data and solving the detection deviation problem caused by air impurities in traditional devices.

[0039] Furthermore, a throttle valve 11 is installed on the air extraction pipe, and a one-way valve is connected to one side of the throttle valve 11. When the controller opens the sixth electric valve 96 (step S3), atmospheric air enters the rod chamber of the cylinder 17 through the air intake pipe and the throttle valve 11. By adjusting the opening of the throttle valve 11, the air intake speed is controlled, thereby controlling the upward speed of the piston 18 (usually set to 5-10 mm / s). This slow and stable upward speed of the piston 18 avoids foaming caused by turbulence when the oil sample enters the buffer pipe 20 too quickly, ensuring accurate triggering of the level switch 19. At the same time, it ensures that the oil sample is pushed to the transformer tank at a constant speed, avoiding pipeline pressure fluctuations caused by sudden increases in flow rate and preventing malfunctions of the transformer protection system.

[0040] The embodiments described in this specification are merely examples of implementations of the inventive concept. The scope of protection of this utility model should not be considered as limited to the specific forms described in the embodiments. The scope of protection of this utility model also extends to equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

Claims

1. An online vacuum degassing device for transformer oil, characterized in that: The system includes a buffer tank, a cylinder, and a vacuum pump. A piston is housed within the cylinder. A guide sleeve is fixedly connected to the lower end of the cylinder, and a guide rod is housed within the guide sleeve. The upper end of the guide rod is fixedly connected to the piston, and a spring is fitted over the guide rod to drive the piston upwards. The upper end of the cylinder is connected to the bottom of the buffer tank, the vacuum pump, and the upper end of the transformer oil tank via first, second, and third pipes, respectively. The lower end of the transformer oil tank is connected to the upper end of the buffer tank via a fourth pipe. A first electric valve is installed on the first pipe, a second electric valve and a pressure sensor are installed on the second pipe, a vent pipe connects to the second electric valve and the vacuum pump, a third electric valve is installed on the vent pipe, and a fourth electric valve is installed on the third pipe. The lower end of the cylinder... The system includes a vacuum pump connected to the exhaust pipe, an intake pipe connected to the exhaust pipe, a fifth electric valve installed on the exhaust pipe, a sixth electric valve installed on the intake pipe, an oil pump installed on the fourth pipe, a buffer pipe with a diameter larger than the second pipe connected to the second pipe between the second electric valve and the vacuum pump, a level switch installed on the buffer pipe, a return pipe connected to the lower end of the buffer pipe, a seventh electric valve installed on the return pipe, a controller, a level switch and a pressure sensor connected to the controller input, and the first, second, third, fourth, fifth, sixth, and seventh electric valves and the vacuum pump all connected to the controller output.

2. The online vacuum degassing device for transformer oil according to claim 1, characterized in that: An oil filter is installed on the fourth pipe.

3. The online vacuum degassing device for transformer oil according to claim 1, characterized in that: A contact block is fixedly connected to the guide rod. A first limit switch and a second limit switch are provided on one side of the contact block. The first limit switch and the second limit switch are alternately triggered by the contact block. The first limit switch and the second limit switch are connected to the input terminal of the controller.

4. The online vacuum degassing device for transformer oil according to claim 1, characterized in that: An insulation layer is installed on the outside of the buffer tank, an electric heater is installed at the bottom of the buffer tank, and a temperature sensor is installed inside the buffer tank. The temperature sensor is connected to the input terminal of the controller, and the electric heater is connected to the output terminal of the controller.

5. The online vacuum degassing device for transformer oil according to claim 1, characterized in that: A high-level sensor and a low-level sensor are respectively installed at the upper and lower ends of the buffer tank, and the high-level sensor and the low-level sensor are connected to the input terminal of the controller.

6. A transformer oil online vacuum degassing device according to any one of claims 1 to 5, characterized in that: An eighth electric valve is installed on the second pipe between the vent pipe and the vacuum pump. A fifth pipe is connected to the third electric valve. A sampling tank is connected to the fifth pipe. A gas detection device is connected to the sampling tank. A ninth electric valve and a tenth electric valve are installed on the fifth pipe on both sides of the sampling tank, respectively. The gas detection device is connected to the input terminal of the controller, and the ninth and tenth electric valves are connected to the output terminal of the controller.

7. A transformer oil online vacuum degassing device according to any one of claims 1 to 5, characterized in that: An air filter is installed at one end of the vent pipe.

8. A transformer oil online vacuum degassing device according to any one of claims 1 to 5, characterized in that: A throttle valve is installed on the extraction pipe, and a check valve is connected to one side of the throttle valve.

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