Wireless self-diagnostic intelligent gas density relay

Abstract

The application discloses a wireless self-diagnosis intelligent gas density relay, which comprises a base assembly, a contact assembly and a display assembly; the contact assembly and the display assembly are fixed on the base assembly respectively; a shell is arranged on the base assembly; a joint is fixed on the shell in a sealed manner; a gas passage is arranged in the joint; a gas path shutdown module is arranged on the upper portion of the gas passage of the joint; the other end of the gas path shutdown module is in sealed communication with a one-way valve, a pressure relief valve, the display assembly and an intelligent diagnosis module; the other end of the gas passage of the one-way valve and the pressure relief valve is in communication with the contact assembly; the other end of the joint is in communication with a gas chamber in an electrical equipment; the two ends of the shell are sealed and connected by a front cover and a rear cover respectively; a first sealed gas chamber and a second sealed gas chamber are arranged in the shell; the display assembly is arranged in the second sealed gas chamber; and the contact assembly is arranged in the first sealed gas chamber. The intelligent diagnosis module is arranged to enable the density monitoring device to realize the function of online checking of the density relay.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electric power, in particular to a wireless self-diagnosis intelligent gas density relay. BACKGROUND

[0002] With the rapid expansion of the capacity of the power system, the use of related electrical equipment in power generation, transformation, transmission, distribution and delivery has rapidly increased. In this case, how to ensure the safe and reliable operation of the power system becomes particularly important. The electrical equipment in the high-voltage field has a high value, and the impact range is wide and the consequences are serious after an accident. Therefore, it is particularly important to ensure the safety of power use in the high-voltage field. SF6 is a gas with good insulation and arc extinguishing performance, and is widely used in the high-voltage field. At present, most high-voltage equipment on the market uses SF6 as an insulating gas. The amount of SF6 directly affects the insulation and arc extinguishing performance of the equipment. If the SF6 gas density decreases to a certain extent, the insulation and arc extinguishing performance will be lost, which will cause a large amount of direct loss and immeasurable indirect loss. Therefore, gas-insulated electrical equipment in the high-voltage field is equipped with an SF6 density relay to monitor the SF6 gas content in the equipment. When the gas pressure in the equipment is too low, an alarm or lock signal is sent to notify the operation and maintenance personnel to handle the problem.

[0003] However, during the application of the density relay, there are often problems such as large deviation of the indicated value and the contact action value, low precision, fault omission and false reporting. After receiving the information, the operation and maintenance personnel need to go to the scene to find out the cause and eliminate the defect. According to the statistics of the State Grid and the South Grid Electric Power Research Institute in 2023, there are more than 50,000 substations in China, and more than 2 million density relays are in operation. Such a large number of in-operation density relays are distributed in various places in China, and the distribution of density relays is extremely dispersed. The time of the fault information of the meter is also uncertain, and the operation and maintenance is extremely difficult. According to the grid operation and maintenance standards and the JJG1073-2011 Pressure Type Sulfur Hexafluoride Gas Density Controller Calibration Regulation, the calibration of the density relay is not more than 1 year. The calibration of the density relay is low in efficiency and high in operating cost. Moreover, the digital transformation of substations has only been carried out for a few years, and the total amount of substations that have completed digital transformation is less than 10%. There are still many old substations that need to dig cable trenches and lay cables, which is very troublesome. Some substations are very old and do not have the conditions for wired construction and cable trench excavation. Therefore, how to provide a wireless gas density relay with high precision, high reliability, intelligent fault diagnosis and prediction for digital transformation has become a problem that needs to be solved by those skilled in the art. SUMMARY

[0004] To address current technological shortcomings, this invention proposes a wireless self-diagnostic intelligent gas density relay to solve the stability, accuracy, and dynamic response problems in PHIL simulation systems.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a wireless self-diagnostic intelligent gas density relay, comprising a mechanical part and an intelligent diagnostic module; the mechanical part includes a base assembly, a contact assembly, a display assembly, a connector, a housing, a front cover, a rear cover, a one-way valve, and a pressure relief valve; the intelligent diagnostic module includes a gas path shut-off module; the contact assembly and the display assembly are respectively fixed on the base assembly, the base assembly is provided with a housing, the connector is fixed to the housing and sealed, the connector is provided with a gas passage, the upper part of the gas passage of the connector is provided with a gas path shut-off module, the other end of the gas path shut-off module is sealed and connected to the one-way valve, the pressure relief valve, and the display assembly; the other end of the gas passage of the one-way valve and the pressure relief valve is connected to the contact assembly, the other end of the connector is connected to the gas chamber in the electrical equipment, the two ends of the housing are sealed and connected by a front cover and a rear cover respectively; the housing is provided with a first sealed gas chamber and a second sealed gas chamber, the display assembly is located in the second sealed gas chamber, and the contact assembly is located in the first sealed gas chamber.

[0006] Furthermore, the contact assembly includes a second base, a base air passage, a low-stiffness Baden tube, a first end seat, and a first crossbeam; the second base is fixed on the base assembly, and one end of the low-stiffness Baden tube is welded to the second base; a base air passage is provided on the second base; the inner cavity of the low-stiffness Baden tube is connected to the base air passage inside the second base, and the base air passage is connected to the other end of the gas passage of the one-way valve and the pressure relief valve; the other end of the low-stiffness Baden tube is provided with a first end seat, and the first end seat is provided with a first crossbeam.

[0007] Furthermore, the contact assembly also includes an adjusting rod, micro switches, and a printed circuit board; the adjusting rod is provided on the first crossbeam; several micro switches are respectively fixed on the printed circuit board, and the printed circuit board is fixed on the second base.

[0008] Furthermore, the micro switch is positioned below the adjusting rod, which directly triggers the micro switch. The contacts of the micro switch are connected from the printed circuit board to a terminal block mounted outside the housing via wires, and the housing of the terminal block is sealed.

[0009] The micro switch includes a first micro switch and a second micro switch; the adjusting rod includes a first adjusting rod and a second adjusting rod.

[0010] Furthermore, the display assembly includes a third base, a Baden tube welding interface, a movement, a dial, hands, a Baden tube, and a second end seat; the third base has a Baden tube welding interface inside; the third base is disposed inside the housing and fixed on the base assembly, and the Baden tube welding interface of the third base is connected to the air circuit at the other end of the air circuit shut-off module; one end of the Baden tube is welded to the Baden tube welding interface, and the other end of the Baden tube is sealed by the second end seat.

[0011] Furthermore, the display assembly also includes a temperature compensation element, a second crossbeam, and a connecting rod; one end of the temperature compensation element is fixed to the second end seat, and the other end of the temperature compensation element is connected to the second crossbeam; the second crossbeam is connected to one end of the connecting rod, and the other end of the connecting rod is connected to the movement; a dial is mounted on the movement, a pointer is mounted on the dial, the pointer can rotate with the movement's moving parts, a pointer lever is mounted on the pointer, and the movement is fixed on the third base.

[0012] Furthermore, the intelligent diagnostic module includes an intelligent control unit, a pressure regulating module, a pressure and temperature sampling module, a gas path shut-off module, a wireless information transceiver module, a power supply module, and an online verification contact sampling module. The gas passage of the gas path shut-off module is also sealed and connected to the pipelines of the pressure regulating module, the pressure and temperature sampling module, and the mechanical part of the density relay, respectively. The intelligent control unit is communicatively connected to the pressure regulating module, the pressure and temperature sampling module, the gas path shut-off module, the wireless information transceiver module, the power supply module, and the online verification contact sampling module. The other two ports of the online verification contact sampling module are connected to a micro switch and a secondary circuit interface, respectively. The secondary circuit interface is used to connect to the backend system.

[0013] The online verification contact sampling module is used to disconnect the mechanical parts from the back-end system signal connection during density relay verification. The intelligent control unit starts the pressure and temperature sampling module, the air circuit shutdown module, the wireless information transceiver module, the power supply module, and the online verification contact sampling module to verify the density relay contacts and transmit the verification results to the back-end system via wireless communication.

[0014] The gas circuit shut-off module is used to cut off the gas circuit connection between the density relay and the gas chamber in the electrical equipment;

[0015] The pressure regulating module is used to adjust the pressure of the gas inside the density relay, causing the microswitch of the density relay to close or open. At the corresponding moment when the microswitch closes or opens, the pressure and temperature of the gas inside the density relay are simultaneously collected by the pressure and temperature sampling module, and the action value and return value of the microswitch are obtained based on the collected pressure and temperature.

[0016] The wireless information transceiver module is used to input the action value and return value of the density relay micro switch obtained from the verification into the host computer for reference by maintenance personnel;

[0017] The power supply module is used to supply power to the intelligent control unit, pressure regulation module, pressure and temperature sampling module, gas path shut-off module, wireless information transceiver module, and online verification contact sampling module.

[0018] Furthermore, the base assembly includes a first base and an outer limiting device; the first base is disposed inside the housing, the outer limiting device is fixed on the first base, and the low-stiffness Baden tube of the contact assembly is disposed inside the outer limiting device.

[0019] Furthermore, the low-stiffness Baden tube of the contact component and the Baden tube of the display component have different stiffnesses; the Baden tube selected for the display component has a stiffness greater than 4 bar, while the low-stiffness Baden tube selected for the contact component has a stiffness less than 2 bar.

[0020] Furthermore, the first sealed gas chamber is pre-charged with SF6 gas at a pressure of P0; the low-stiffness Baden tube is installed inside the contact assembly, one end of the low-stiffness Baden tube is connected to the SF6 gas passage of the electrical equipment through the one-way valve, the pressure relief valve and the gas path shut-off module, and the low-stiffness Baden tube is pre-charged with SF6 gas at a pressure of P0-0.01MPa, the pressure relief valve is installed in the gas path of the low-stiffness Baden tube, and the pressure relief pressure of the pressure relief valve is set to P0-0.01MPa;

[0021] The low-stiffness Baden tube has an initial position and a limiting pressure point. The initial position is the position where the micro switch is triggered and turned on when the low-stiffness Baden tube is connected to the pneumatic circuit of the electrical equipment in the initial state. The limiting pressure point is the position where the low-stiffness Baden tube is stopped by the external limiting device when it moves outward. The travel distance from the initial position to the limiting pressure point is the effective travel distance of the low-stiffness Baden tube.

[0022] In the initial state, the low-stiffness Baden tube is in the initial position, and the pre-charge pressure P0 of the first sealed air chamber is 0.01 MPa greater than the internal pressure of the low-stiffness Baden tube. The low-stiffness Baden tube moves inward and bends.

[0023] When SF6 gas from electrical equipment is introduced into the low-stiffness Baden pipe through the one-way valve:

[0024] When the pressure inside the low-stiffness Baden tube is less than the pre-charge pressure P0 of the first sealed air chamber, the low-stiffness Baden tube remains in its initial position.

[0025] When the gas pressure entering the low-stiffness Baden tube is greater than or equal to the pre-charge pressure P0 of the first sealed air chamber, the low-stiffness Baden tube moves outward; until the internal pressure of the low-stiffness Baden tube increases to the pressure corresponding to the limit pressure point, the external limit device prevents the low-stiffness Baden tube from continuing to move outward.

[0026] When electrical equipment leaks SF6 gas:

[0027] When the pressure inside the low-rigidity Baden tube is greater than the pre-charge pressure P0+0.1MPa of the first sealed air chamber, the low-rigidity Baden tube remains in contact with the external limiting device.

[0028] When the pre-charge pressure P0 of the first sealed air chamber is less than the pressure inside the low-rigidity Baden tube and less than the pre-charge pressure P0 + 0.1 MPa of the first sealed air chamber, the low-rigidity Baden tube moves inward, causing the first crossbeam, the first adjusting rod, and the second adjusting rod to move inward synchronously.

[0029] When the pressure inside the low-stiffness Baden tube drops to the first micro switch warning threshold, the first adjusting rod triggers the first micro switch to issue a low air pressure alarm signal.

[0030] When the pressure inside the low-stiffness Baden tube drops to the second microswitch lockout threshold, the second adjusting rod triggers the second microswitch to send a lockout signal.

[0031] When the pressure inside the low-stiffness Baden tube is less than or equal to the pre-charge pressure P0-0.01MPa of the first sealed air chamber, the pressure relief valve closes, the pressure inside the low-stiffness Baden tube remains stable, the pressure difference between the inside and outside of the low-stiffness Baden tube remains constant, and the low-stiffness Baden tube stops moving inward.

[0032] Compared with existing technologies, the present invention has the following advantages:

[0033] (1) This invention improves the resolution of low-stiffness Baden tube measurement by reducing the stiffness of the low-stiffness Baden tube in the contact assembly, sets the low-stiffness Baden tube in a sealed air chamber, and pre-fills the sealed air chamber with compensation gas during the manufacturing process, so that the density relay can meet the manufacturing requirements of having the ability to set different alarm / lock contacts; and integrates the density relay with the traditional calibrator design, and adopts wireless information transceiver module communication, so that the density relay has all the functions of the traditional density relay, all the functions of the calibrator, and also has wireless transmission capability, so that the density relay has the characteristics of maintenance-free operation.

[0034] (2) By selecting low-stiffness Baden tubes, the present invention can greatly improve the measurement accuracy of the density relay action contacts, making the density relay measurement contacts more accurate, reducing false alarms / false alarms caused by insufficient accuracy of the contact measurement device, and improving the accuracy, quality and efficiency of operation and maintenance.

[0035] (3) This invention enables the density monitoring device to perform online verification of density relays by using a wireless information transceiver module. Furthermore, the density monitoring device uses wireless communication, eliminating the need for cable laying and foundation excavation during installation and construction, which greatly facilitates intelligent transformation, especially for the renovation of old substations. At the same time, the equipment can perform fault diagnosis and prediction, providing accurate basic data and accurate fault diagnosis, thus providing accurate information and decision support for operation and maintenance. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the intelligent gas density relay structure of the present invention.

[0037] Figure 2 This is a schematic diagram showing the structural distinction between the mechanical parts and the intelligent diagnostic module of the intelligent gas density relay of the present invention.

[0038] Figure 3 This is a schematic diagram of the movement and positional relationship of the low-stiffness Baden tube in the contact assembly of the present invention after being subjected to force.

[0039] Figure 4 This is a schematic diagram of the effective stroke structure of the initial position and limiting pressure point of the low-stiffness Baden tube of the present invention.

[0040] Figure 5 This is a schematic diagram of the display component 3 of the present invention.

[0041] Figure 6 This is a block diagram showing the connection between the intelligent diagnostic module and the gas passage of the present invention.

[0042] Reference numerals: 1. Base assembly; 11. First base; 12. External limiting device; 2. Contact assembly; 21. Second base; 211. Base air passage; 22. Low-rigidity Baden tube; 23. First end seat; 24. First crossbeam; 25. Adjusting rod; 26. Micro switch; 27. Printed circuit board; 3. Display assembly; 31. Third base; 311. Baden tube welding interface; 32. Movement; 33. Dial; 34. Hand; 35. Baden tube; 36. ... 37. Second crossbeam; 38. Connecting rod; 4. Connector; 41. One-way valve; 42. Pressure relief valve; 5. Housing; 6. Front cover; 7. Rear cover; 8. Intelligent diagnostic module; 801. Intelligent control unit; 802. Pressure regulating module; 803. Pressure and temperature sampling module; 804. Gas circuit shutdown module; 805. Wireless information transceiver module; 806. Power supply module; 807. Online verification contact sampling module; V1 is the first sealed air chamber; V2 is the second sealed air chamber. Detailed Implementation

[0043] like Figure 1As shown, the present invention provides a technical solution: a wireless self-diagnostic intelligent gas density relay, comprising a mechanical part and an intelligent diagnostic module 8; the mechanical part includes a base assembly 1, a contact assembly 2, a display assembly 3, a connector 4, a housing 5, a front cover 6, a rear cover 7, a one-way valve 41, and a pressure relief valve 42; the intelligent diagnostic module 8 includes a gas path shut-off module 804; the contact assembly 2 and the display assembly 3 are respectively fixed on the base assembly 1, the base assembly 1 is provided with a housing 5, the connector 4 is fixed to the housing 5 and sealed, the connector 4 is provided with a gas passage, and the connector 4... The upper part of the gas passage is provided with a gas path shut-off module 804. The other end of the gas path shut-off module 804 is sealed and connected to the one-way valve 41, the pressure relief valve 42, and the display component 3. The gas passages at the other ends of the one-way valve 41 and the pressure relief valve 42 are connected to the contact component 2. The other end of the connector 4 is connected to the gas chamber in the electrical equipment. The two ends of the housing 5 are sealed and connected by the front cover 6 and the rear cover 7, respectively. The housing 5 is provided with a first sealed gas chamber V1 and a second sealed gas chamber V2. The display component 3 is located in the second sealed gas chamber V2, and the contact component 2 is located in the first sealed gas chamber V1.

[0044] like Figures 1-4 As shown, the contact assembly 2 includes a second base 21, a base air passage 211, a low-stiffness Baden tube 22, a first end seat 23, a first crossbeam 24, an adjusting rod 25, a micro switch 26, and a printed circuit board 27. The second base 21 is fixed to the base assembly 1, and one end of the low-stiffness Baden tube 22 is welded to the second base 21. The second base 21 has a base air passage 211. The inner cavity of the low-stiffness Baden tube 22 communicates with the base air passage 211 inside the second base 21. The base air passage 211 is connected to the other end of the gas passage of the one-way valve 41 and the pressure relief valve 42. The other end of the low-rigidity Baden tube 22 is provided with a first end seat 23, a first crossbeam 24 is provided on the first end seat 23, and an adjusting rod 25 (or multiple rods) is provided on the first crossbeam 24; several microswitches 26 (or multiple microswitches) are respectively fixed on the printed circuit board 27, the printed circuit board 27 is fixed on the second base 21, and the microswitches 26 are correspondingly arranged below the adjusting rod 25. The adjusting rod 25 can directly or indirectly trigger the microswitches 26 to act; the contacts of the microswitches 26 are all connected from the printed circuit board 27 to the terminal block installed outside the housing 5 through wires, and the housing of the terminal block is sealed.

[0045] Among them, the micro switch 26 includes a first micro switch and a second micro switch; the adjusting rod 25 includes a first adjusting rod and a second adjusting rod.

[0046] like Figure 1 and Figure 5As shown, the display component 3 includes a third base 31, a Baden tube welding interface 311, a movement 32, a dial 33, a pointer 34, a Baden tube 35, a second end seat 36, a second crossbeam 37, and a connecting rod 38; the third base 31 has a Baden tube welding interface 311 inside; the third base 31 is disposed inside the housing 5 and fixed on the base component 1, and the Baden tube welding interface 311 of the third base 31 is connected to the air passage at the other end of the air passage shut-off module 804; one end of the Baden tube 35 is welded to the Baden tube welding interface 311, and the other end of the Baden tube 35 is sealed by the second end seat 36;

[0047] One end of the temperature compensation element is fixed on the second end seat 36, and the other end of the temperature compensation element is connected to the second crossbeam 37; the second crossbeam 37 is connected to one end of the connecting rod 38, and the other end of the connecting rod 38 is connected to the movement 32; a dial 33 is mounted on the movement 32, and a pointer 34 is mounted on the dial 33. The pointer 34 can rotate with the moving parts of the movement 32, and a pointer lever is mounted on the pointer 34. The movement 32 is fixed on the third base 31. Gas inside the electrical equipment enters the Baden tube 35 through connector 4 and the Baden tube welding interface 311. The second sealed air chamber V2 outside the Baden tube 35 is sealed with a pre-charged atmospheric pressure. When the gas pressure inside the Baden tube 35 is different from the pre-charged gas pressure of the second sealed air chamber V2, the Baden tube 35 undergoes elastic deformation in the opposite direction of the curvature center. The displacement of the closed end of the Baden tube 35 drives the temperature compensation element, the second crossbeam 37, and the connecting rod 38 to transmit in sequence, driving the mechanism 32 and the pointer 34 to rotate, displaying the actual gas pressure value.

[0048] like Figure 6 As shown, the intelligent diagnostic module 8 includes an intelligent control unit 801, a pressure regulating module 802, a pressure and temperature sampling module 803, a gas path shut-off module 804, a wireless information transceiver module 805, a power supply module 806, and an online verification contact sampling module 807. The gas passage of the gas path shut-off module 804 is also sealed and connected to the pipelines of the pressure regulating module 802, the pressure and temperature sampling module 803, and the mechanical part of the density relay. The intelligent control unit 801 is communicatively connected to the pressure regulating module 802, the pressure and temperature sampling module 803, the gas path shut-off module 804, the wireless information transceiver module 805, the power supply module 806, and the online verification contact sampling module 807. The other two ports of the online verification contact sampling module 807 are connected to the micro switch 26 and the secondary circuit interface, respectively. The secondary circuit interface is used to connect to the background system.

[0049] like Figure 1As shown, the base assembly 1 includes a first base 11 and an outer limiting device 12. The first base 11 is disposed inside the housing 5, and the outer limiting device 12 is fixed on the first base 11. The low-stiffness Baden tube 22 of the contact assembly 2 is disposed inside the outer limiting device 12. The low-stiffness Baden tube 22 moves within a pressure range of 0~0.1 MPa when the pressure difference between the low-stiffness Baden tube 22 and the first sealed air chamber V1 exceeds 0.1 MPa. When the pressure difference between the low-stiffness Baden tube 22 and the first sealed air chamber V1 exceeds 0.1 MPa, the outer side of the low-stiffness Baden tube 22 contacts the outer limiting device 12, preventing the low-stiffness Baden tube 22 from continuing to move outward with pressure changes. When the pressure difference between the low-stiffness Baden tube 22 and the first sealed air chamber V1 is too large, the outer limiting device 12 can protect the low-stiffness Baden tube 22 from excessive deformation and damage.

[0050] The first sealed gas chamber V1 is pre-charged with SF6 gas at a pressure of P0; the low-stiffness Baden tube 22 is installed in the contact assembly 2, and one end of the low-stiffness Baden tube 22 is connected to the SF6 gas passage of the electrical equipment through the one-way valve 41, the pressure relief valve 42 and the gas path shut-off module 804. The low-stiffness Baden tube 22 is pre-charged with SF6 gas at a pressure of P0-0.01MPa. The pressure relief valve 42 is installed in the gas path of the low-stiffness Baden tube 22, and the pressure relief pressure of the pressure relief valve 42 is set to P0-0.01MPa.

[0051] The low-stiffness Baden tube 22 has an initial position S1 and a limiting pressure point S2. The initial position S1 is the position where the micro switch 26 is triggered to turn on (or off) when the low-stiffness Baden tube 22 is connected to the pneumatic circuit of the electrical equipment in the initial state. The limiting pressure point S2 is the position where the low-stiffness Baden tube 22 is stopped by the external limiting device 12 when it moves outward. The stroke from the initial position S1 to the limiting pressure point S2 is the effective stroke of the low-stiffness Baden tube 22.

[0052] In the initial state, the low-stiffness Baden tube 22 is in the initial position S1, and the pre-charge pressure P0 of the first sealed air chamber V1 is 0.01 MPa greater than the internal pressure of the low-stiffness Baden tube 22. The low-stiffness Baden tube 22 moves inward and bends.

[0053] When the SF6 gas from the electrical equipment is introduced into the low-stiffness Baden pipe 22 through the one-way valve 41:

[0054] When the pressure inside the low-stiffness Baden tube 22 is less than the pre-charge pressure P0 of the first sealed air chamber V1, the low-stiffness Baden tube 22 remains in the initial position S1.

[0055] When the gas pressure entering the low-stiffness Baden tube 22 is greater than or equal to the pre-charge pressure P0 of the first sealed air chamber V1, the low-stiffness Baden tube 22 moves outward; until the internal pressure of the low-stiffness Baden tube 22 increases to the pressure corresponding to the limit pressure point S2, the external limit device 12 prevents the low-stiffness Baden tube 22 from continuing to move outward.

[0056] When electrical equipment leaks SF6 gas:

[0057] When the internal pressure of the low-rigidity Baden tube 22 is greater than the pre-charge pressure P0 + 0.1 MPa of the first sealed air chamber V1, the low-rigidity Baden tube 22 remains in contact with the external limiting device 12.

[0058] When the pre-charge pressure P0 of the first sealed air chamber V1 is less than the pressure inside the low-rigidity Baden tube 22 and less than the pre-charge pressure P0 + 0.1 MPa of the first sealed air chamber V1, the low-rigidity Baden tube 22 moves inward, causing the first crossbeam 24 and the first and second adjusting rods to move inward synchronously.

[0059] When the pressure inside the low-stiffness Baden tube 22 drops to the first micro switch warning threshold, the first adjusting rod triggers the first micro switch to issue a low air pressure alarm signal.

[0060] When the pressure inside the low-stiffness Baden tube 22 drops to the second micro-switch locking threshold, the second adjusting rod triggers the second micro-switch to send a locking signal.

[0061] Contact signals include alarm signals and interlock signals, which are generated by the state changes (closed / open) of alarm contacts and interlock contacts, respectively.

[0062] When the pressure inside the low-stiffness Baden tube 22 is less than or equal to the pre-charge pressure P0-0.01MPa of the first sealed air chamber V1, the pressure relief valve 42 closes, the pressure inside the low-stiffness Baden tube 22 remains stable, the pressure difference between the inside and outside of the low-stiffness Baden tube 22 remains constant, and the low-stiffness Baden tube 22 stops moving inward.

[0063] The pressure regulating module 802 is used to adjust the pressure of the gas inside the density relay, causing the micro switch 26 of the density relay to close or open. At the corresponding moment when the micro switch 26 closes or opens, the pressure and temperature of the gas inside the density relay are simultaneously collected by the pressure and temperature sampling module 803, and the action value and return value of the micro switch 26 are obtained based on the collected pressure and temperature.

[0064] The pressure and temperature sampling module 803 includes one or more temperature sensors and pressure sensors, used to synchronously collect the pressure and temperature of the gas inside the density relay, and to obtain the action value and return value of the micro switch 26 based on the collected pressure and temperature.

[0065] Pressure sensors can be absolute pressure sensors, relative pressure sensors, or a combination of both. The number of pressure sensors can be multiple. Pressure sensor forms can include diffused silicon pressure sensors, MEMS pressure sensors, chip-type pressure sensors, coil-induction pressure sensors (such as pressure sensors with Baden tubes and induction coils), and resistance pressure sensors (such as pressure sensors with Baden tubes and slide wire resistors). They can be analog or digital pressure sensors. Pressure acquisition utilizes various pressure-sensing elements such as pressure sensors and pressure transmitters, including diffused silicon, sapphire, piezoelectric, and strain gauge types (resistive strain gauges and ceramic strain gauges). Temperature sensors can be thermocouples, thermistors, or semiconductor types. Temperature sensors can be contact or non-contact. Depending on the sensor materials and electronic component characteristics, temperature sensors can be resistance temperature detectors (RTDs) and thermocouples. In short, temperature acquisition can utilize various temperature-sensing elements such as temperature sensors and temperature transmitters.

[0066] The pneumatic circuit shut-off module 804 is used to control the connection or disconnection between the pneumatic circuit of the electrical equipment body and the one-way valve 41, the pressure relief valve 42, the display component 3, and the intelligent diagnostic module 8. The pneumatic circuit shut-off module 804 can be controlled in various ways, including manual, electric, pneumatic, hydraulic, electromagnetic, and self-operated methods.

[0067] The online verification contact sampling module 807 includes two states, K1 and K2. K1 is the normal connection position between the density relay alarm contact and the interlocking contact and the secondary circuit interface, maintaining the connection between the density relay and the substation background signal; K2 is the disconnection between the density relay alarm contact and the interlocking contact and the secondary circuit interface, connecting to the first intelligent control unit 801.

[0068] Among them, the intelligent control unit 801 is used to start the pressure and temperature sampling module 803, the gas circuit shut-off module 804, the wireless information transceiver module 805, the power supply module 806, and the online verification contact sampling module 807 to verify the density relay contacts and transmit the verification results to the background system through wireless communication.

[0069] The processor of the intelligent control unit 801 can be a general-purpose computer, industrial control computer, CPU, microcontroller, ARM chip, AI chip, MCU, FPGA, PLC, industrial control motherboard, or embedded main control board.

[0070] Among them, the power supply module 806 is used to supply power to the intelligent control unit 801, the pressure regulating module 802, the pressure and temperature sampling module 803, the gas circuit shut-off module 804, the wireless information transceiver module 805, and the online verification contact sampling module 807.

[0071] Among them, the low-stiffness Baden tube 22 of the contact component 2 and the Baden tube of the display component 3 have different stiffnesses; the Baden tube 35 selected for the display component 3 has a stiffness greater than 4 bar, while the low-stiffness Baden tube 22 selected for the contact component 2 has a stiffness less than 2 bar.

[0072] When the contact assembly 2 and the display assembly 3 are subjected to the same gas pressure, the displacement of the end of the low-stiffness Baden tube 22 of the contact assembly 2 is greater than the displacement of the end of the Baden tube 35 of the display assembly 3. That is, the contact assembly 2 has a higher resolution and higher pressure measurement accuracy.

[0073] The working principle of the intelligent gas density relay is as follows:

[0074] The internal air passage of the density relay is connected to the air chamber of the electrical equipment body, and the air pressure inside the density relay is equal to the air pressure inside the air chamber of the electrical equipment body.

[0075] When the air pressure (P20) inside the electrical equipment changes, the pressure monitored by the density relay will change in real time with the pressure of the electrical equipment;

[0076] During the manufacturing process, the pressure relief valve 42 is set to P0-0.01 MPa, and the low-rigidity Baden pipe 22 is pre-filled with SF6 gas at a pressure of P0-0.01 MPa.

[0077] When the pressure inside the low-stiffness Baden tube 22 is greater than the pre-charge pressure of the first sealed air chamber V1, the low-stiffness Baden tube 22 tends to move outward (the reference direction is its own center of curvature).

[0078] When the end of the low-stiffness Baden tube 22 moves to the limiting pressure point S2 of the outer limiting device 12, the outer limiting device 12 of the base assembly 1 prevents the low-stiffness Baden tube 22 from moving outward, and the position of the low-stiffness Baden tube 22 remains unchanged and does not change with the pressure inside the low-stiffness Baden tube 22.

[0079] Afterwards, SF6 gas is pre-filled into the first sealed air chamber V1 where the contact component 2 is located. After the first sealed air chamber V1 is filled with gas, the low stiffness Baden tube 22 is disengaged from the outer limit device 12. The low stiffness Baden tube 22 moves to the initial position S1 and then stops. The stroke between the initial position S1 and the limit pressure point S2 of the outer limit device 12 is the effective stroke of the low stiffness Baden tube 22. During manufacturing, alarm and interlocking contacts can be set within the stroke range as needed.

[0080] When the density relay is not installed in the electrical equipment, and the gas inside the electrical equipment body is not introduced into the density relay, the density relay is in the factory state. The first sealed gas chamber V1 and the low stiffness Baden tube 22 have been pre-filled with SF6 gas of P0 and P0-0.01MPa respectively. The pre-filling pressure of the first sealed gas chamber V1 is greater than the internal pressure of the low stiffness Baden tube 22. The low stiffness Baden tube 22 is in the initial position S1.

[0081] When the density relay is installed in electrical equipment, the gas inside the electrical equipment body flows into the low-rigidity Baden tube 22 in the contact assembly 2 through the connector 4 and the one-way valve 41. When the internal pressure of the low-rigidity Baden tube 22 is greater than the pre-charge pressure of the first sealed air chamber V1, the low-rigidity Baden tube 22 begins to move outward. As the internal pressure of the low-rigidity Baden tube 22 increases, the distance the low-rigidity Baden tube 22 moves outward increases until the internal pressure of the low-rigidity Baden tube 22 increases to the limit pressure point S2. At this point, the path of the low-rigidity Baden tube 22 moving outward is blocked by the external limit device 12. After that, the low-rigidity Baden tube 22 does not move with the increase of internal pressure and remains stationary.

[0082] When gas leaks inside the electrical equipment, the pressure inside the low-rigidity Baden tube 22 is greater than the pressure of the pressure relief valve 42. The pressure relief valve 42 is in the open state, and the gas inside the low-rigidity Baden tube 22 flows into the first sealed gas chamber V1 through the pressure relief valve 42. The pressure inside the low-rigidity Baden tube 22 decreases as the gas pressure inside the electrical equipment decreases.

[0083] When the pressure inside the low-rigidity Baden tube 22 is greater than the pre-charge pressure of the first sealed air chamber V1, the outer wall of the low-rigidity Baden tube 22 remains in contact with the outer limiting device 12, and the low-rigidity Baden tube 22 does not move inward as the internal pressure decreases.

[0084] As the internal gas pressure decreases, the low-rigidity Baden tube 22 moves inward, and the first crossbeam 24 fixed on the first end seat 23 also moves inward. The adjusting rod 25 installed on the first crossbeam 24 moves inward together with the first crossbeam 24. As the air pressure decreases, the distance between the adjusting rod 25 and the contact of the micro switch 26 gets closer and closer.

[0085] When the air pressure of the electrical equipment drops to the alarm threshold preset by the first micro switch, the first adjusting rod triggers the signal switching of the first micro switch (from disconnected to connected or from connected to disconnected), sending an alarm signal of low air pressure to the backend to notify the maintenance personnel for maintenance.

[0086] When the air pressure drops further and reaches the lockout threshold preset by the second micro switch, the second adjusting rod triggers the signal switching of the second micro switch (from disconnected to connected or from connected to disconnected), sending a lockout signal to the background that the air pressure of the electrical equipment does not meet the safety requirements for operation. The electrical equipment then stops working.

[0087] When the electrical equipment continues to leak, after the gas leaks from the electrical equipment, when the internal pressure of the low-rigidity Baden tube 22 is less than the pre-charge pressure P0-0.1MPa of the first sealed air chamber V1, the pressure relief valve 42 closes the gas passage. The internal pressure of the low-rigidity Baden tube 22 does not decrease with the gas leakage in the first sealed air chamber V1, and the low-rigidity Baden tube 22 cannot continue to move inward.

[0088] For example, a density relay with parameters of 0.60 / 0.55 / 0.50 / 0.50 has a rated value of 0.6MPa, an alarm value of 0.55MPa, an initial state low-stiffness Baden tube 22 with a pre-charged gas pressure of 0.49MPa, and an external limit device 12 limiting the low-stiffness Baden tube 22 to a limit pressure point of 0.59MPa.

[0089] Before the density relay is installed, the air pressure in the first sealed air chamber V1 is 0.59 MPa, the pressure inside the low-stiffness Baden tube 22 is 0.49 MPa, the pre-charge pressure of the first sealed air chamber V1 is greater than the pressure inside the low-stiffness Baden tube 22, and the low-stiffness Baden tube 22 is in the initial position S1.

[0090] When the density relay is installed on electrical equipment, when the electrical equipment is filled with SF6 gas at 0.6 MPa, the pressure inside the low-rigidity Baden tube 22 is equal to the pressure inside the electrical equipment. The internal pressure of the low-rigidity Baden tube 22 is greater than the pressure P0 (0.59 MPa) limited by the external limit device 12. The movement of the low-rigidity Baden tube 22 is restricted, and it will not move outward as the internal pressure of the low-rigidity Baden tube 22 increases. The outer wall of the low-rigidity Baden tube 22 is kept tightly pressed against the external limit device 12, and the low-rigidity Baden tube 22 will not be damaged due to excessive internal pressure.

[0091] When the electrical equipment leaks gas, the pressure relief valve 42 is in the open state because the pressure is greater than the initial pre-charge pressure of 0.49 MPa in the low-rigidity Baden tube 22. As the electrical equipment leaks, the gas pressure in the low-rigidity Baden tube 22 gradually decreases. When the pressure is greater than 0.59 MPa, the outside of the low-rigidity Baden tube 22 remains in contact with the external limit device 12, and the position remains unchanged.

[0092] When the pressure of the electrical equipment decreases to 0.59 MPa, the low-stiffness Baden pipe 22 moves inward as the leakage inside the electrical equipment increases, and the SF6 pressure decreases to 0.55 MPa. The first regulating rod triggers the first alarm contact, and the density relay sends an alarm signal. When the SF6 gas leaks further and the SF6 pressure decreases to 0.50 MPa, the second regulating rod triggers the second interlock contact, sending an interlock signal to the back-end system to notify the maintenance personnel to perform maintenance.

[0093] If the gas leakage problem in the electrical equipment is not resolved and continues to leak, when the gas leakage in the electrical equipment reaches 0.49 MPa, the pressure relief valve 42 will close. At this time, the gas pressure in the low-rigidity Baden tube 22 will remain unchanged and will not decrease with the gas leakage in the electrical equipment. The tendency of the low-rigidity Baden tube 22 to move inward will stop. The pressure in the low-rigidity Baden tube 22 will be kept within a certain range from the gas pressure in the first sealed air chamber V1. This can protect the low-rigidity Baden tube 22 from being damaged due to excessive pressure difference during operation.

[0094] The working principle of online contact verification for intelligent gas density relays is as follows:

[0095] A periodic verification time can be set within the intelligent gas density relay, or a verification command can be sent to the intelligent gas density relay from the background system.

[0096] When the verification time is reached or a verification command is received, the density relay is adjusted to the verification state by the intelligent control unit 801. In the verification state, the online verification contact sampling module 807 cuts off the communication connection between the density relay alarm contact and the interlock signal and the background system. The switch of the online verification contact sampling module 807 is switched from K2 to K1, and the communication connection between the gas density relay contact signal and the background system is switched to the communication connection with the intelligent control unit 801.

[0097] The intelligent control unit 801 controls the gas path shut-off module 804 to cut off the gas passage between the density relay and the electrical equipment, so that the gas passage inside the density relay is independent of the first sealed gas chamber V1. The pressure regulating module 802 can effectively regulate the pressure inside the density relay.

[0098] Then, the intelligent control unit 801 controls the pressure regulating module 802 to adjust the gas pressure inside the density relay according to the needs of contact verification, so that the gas pressure inside the density relay slowly decreases, triggering the contact action of the density relay to generate alarm signal and lockout signal. The contact action of the alarm signal and lockout signal is transmitted to the intelligent control unit 801 through the online verification contact sampling module 807. The intelligent control unit 801 obtains the detected gas density value P20 based on the pressure value P and temperature value T when the contact action of the alarm signal and lockout signal occurs. Based on the detected gas density value P20, the contact action value of the density relay alarm signal and lockout signal is detected, thus completing the verification of the contact signal action value of the density relay.

[0099] The intelligent control unit 801 drives the pressure regulating module 802 to slowly increase the gas pressure of the density relay. The contacts of the density relay generate alarm and lockout signals and are reset. The reset of the alarm and lockout signals is transmitted to the intelligent control unit 801 through the online verification contact sampling module 807. The intelligent control unit 801 obtains the reset gas density value P20 based on the pressure value P and temperature value T when the contacts of the alarm and lockout signals are reset. Based on the reset gas density value P20, the contact return values ​​of the alarm and lockout signals of the density relay are detected, thus completing the verification of the contact signal return values ​​of the density relay.

[0100] After all contact signal verification work is completed, the intelligent control unit 801 controls the gas circuit shutdown module 804 to open, so that the gas circuit of the density relay and the electrical equipment are connected to each other, and the online verification contact sampling module 807 is adjusted to the working state, restoring the normal operation state.

[0101] The intelligent control unit 801 will complete the verification of the contact signal action value of the density relay and the verification of the contact signal return value of the density relay, and upload the data to the host computer through the wireless information transceiver module 805 for reference by the operation and maintenance personnel.

[0102] In this embodiment, the intelligent control unit 801 controls the opening and closing of the gas path shut-off module 804 of the gas density monitoring device. This ensures that during operation, the density relay is connected to the electrical equipment in the gas path, allowing the density relay to safely monitor the gas density of the electrical equipment and ensuring its safe and reliable operation. During verification, the gas density relay is not connected to the electrical equipment in the gas path, and online verification of the density relay does not affect the safe operation of the electrical equipment. This embodiment enables online verification of the density relay, improving efficiency and reducing maintenance costs. Furthermore, the entire verification process achieves zero SF6 gas emissions, complying with environmental regulations and facilitating widespread application.

[0103] When an upward trend in gas pressure is detected online, an abnormality notification can be issued in a timely manner.

[0104] The wireless self-diagnostic intelligent gas density relay of the present invention also includes a function to protect the electronic components from ambient temperature, preventing operation at excessively low or high temperatures and ensuring that the density relay operates within the allowable temperature range. The wireless self-diagnostic intelligent gas density relay of the present invention can also be equipped with a heater and / or a heat sink (e.g., a fan), activating the heater at low temperatures and the heat sink at high temperatures to ensure that related sensors and / or integrated circuits and other electronic components can operate reliably in low or high temperature environments.

[0105] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A wireless self-diagnostic intelligent gas density relay, characterized in that, It includes a mechanical component and an intelligent diagnostic module. The mechanical component includes a base assembly, a contact assembly, a display assembly, a connector, a housing, a front cover, a rear cover, a one-way valve, and a pressure relief valve. The intelligent diagnostic module includes a gas path shut-off module. The contact assembly and the display assembly are respectively fixed on the base assembly. The base assembly has a housing. The connector is fixed to the housing and sealed. The connector has a gas passage. The upper part of the gas passage of the connector has a gas path shut-off module. The other end of the gas path shut-off module is sealed and connected to the one-way valve, the pressure relief valve, and the display assembly. The other end of the gas passage of the one-way valve and the pressure relief valve is connected to the contact assembly. The other end of the connector is connected to the gas chamber in the electrical equipment. The two ends of the housing are sealed and connected by a front cover and a rear cover, respectively. The housing has a first sealed gas chamber and a second sealed gas chamber. The display assembly is located in the second sealed gas chamber, and the contact assembly is located in the first sealed gas chamber. The contact assembly includes a second base, a base air passage, a low-stiffness Baden tube, a first end seat, and a first crossbeam. The second base is fixed to the base assembly, and one end of the low-stiffness Baden tube is welded to the second base. A base air passage is provided on the second base. The inner cavity of the low-stiffness Baden tube is connected to the base air passage inside the second base. The base air passage is connected to the other end of the gas passage of the one-way valve and the pressure relief valve. The other end of the low-stiffness Baden tube is provided with a first end seat, and the first end seat is provided with a first crossbeam. The low-stiffness Baden tubes of the contact components and the Baden tubes of the display components have different stiffnesses; the Baden tubes used in the display components have a stiffness greater than 4 bar, while the low-stiffness Baden tubes used in the contact components have a stiffness less than 2 bar. The first sealed gas chamber is pre-charged with SF6 gas at a pressure of P0; the low-stiffness Baden tube is installed in the contact assembly, one end of the low-stiffness Baden tube is connected to the SF6 gas passage of the electrical equipment through the one-way valve, the pressure relief valve and the gas path shut-off module, and the low-stiffness Baden tube is pre-charged with SF6 gas at a pressure of P0-0.01MPa, the pressure relief valve is installed in the gas path of the low-stiffness Baden tube, and the pressure relief pressure of the pressure relief valve is set to P0-0.01MPa; The base assembly includes a first base and an outer limiting device; the first base is disposed inside the housing, the outer limiting device is fixed on the first base, and the low-rigidity Baden tube of the contact assembly is disposed inside the outer limiting device. The low-stiffness Baden tube has an initial position and a limiting pressure point. The initial position is the position where the micro switch is triggered and turned on when the low-stiffness Baden tube is connected to the pneumatic circuit of the electrical equipment in the initial state. The limiting pressure point is the position where the low-stiffness Baden tube is stopped by the external limiting device when it moves outward. The travel distance from the initial position to the limiting pressure point is the effective travel distance of the low-stiffness Baden tube.

2. The wireless self-diagnostic intelligent gas density relay according to claim 1, characterized in that: The contact assembly also includes an adjusting rod, micro switches, and a printed circuit board; the adjusting rod is provided on the first crossbeam; several micro switches are respectively fixed on the printed circuit board, and the printed circuit board is fixed on the second base.

3. The wireless self-diagnostic intelligent gas density relay according to claim 2, characterized in that: The micro switch is positioned below the adjusting rod, which directly triggers the micro switch. The contacts of the micro switch are connected from the printed circuit board to a terminal block mounted outside the housing via wires. The terminal block is sealed in the housing. The micro switch includes a first micro switch and a second micro switch; the adjusting rod includes a first adjusting rod and a second adjusting rod.

4. A wireless self-diagnostic intelligent gas density relay according to claim 3, characterized in that: The display assembly includes a third base, a Baden tube welding interface, a movement, a dial, hands, a Baden tube, and a second end seat; the third base has a Baden tube welding interface inside; the third base is located inside the housing and fixed to the base assembly, and the Baden tube welding interface of the third base is connected to the gas path at the other end of the gas path shut-off module; one end of the Baden tube is welded to the Baden tube welding interface, and the other end of the Baden tube is sealed by the second end seat.

5. A wireless self-diagnostic intelligent gas density relay according to claim 4, characterized in that: The display assembly also includes a temperature compensation element, a second crossbeam, and a connecting rod; one end of the temperature compensation element is fixed to the second end seat, and the other end of the temperature compensation element is connected to the second crossbeam; the second crossbeam is connected to one end of the connecting rod, and the other end of the connecting rod is connected to the movement; a dial is mounted on the movement, a pointer is mounted on the dial, the pointer rotates with the movement's moving parts, a pointer lever is mounted on the pointer, and the movement is fixed on the third base.

6. A wireless self-diagnostic intelligent gas density relay according to claim 5, characterized in that: The intelligent diagnostic module includes an intelligent control unit, a pressure regulating module, a pressure and temperature sampling module, a gas path shut-off module, a wireless information transceiver module, a power supply module, and an online verification contact sampling module. The gas passage of the gas path shut-off module is also sealed and connected to the pipelines of the pressure regulating module, the pressure and temperature sampling module, and the mechanical part of the density relay. The intelligent control unit is communicatively connected to the pressure regulating module, the pressure and temperature sampling module, the gas path shut-off module, the wireless information transceiver module, the power supply module, and the online verification contact sampling module. The other two ports of the online verification contact sampling module are connected to a micro switch and a secondary circuit interface, respectively. The secondary circuit interface is used to connect to the backend system. The online verification contact sampling module is used to disconnect the mechanical parts from the back-end system signal connection during density relay verification. The intelligent control unit starts the pressure and temperature sampling module, the air circuit shutdown module, the wireless information transceiver module, the power supply module, and the online verification contact sampling module to verify the density relay contacts and transmit the verification results to the back-end system via wireless communication. The gas circuit shut-off module is used to cut off the gas circuit connection between the density relay and the gas chamber in the electrical equipment; The pressure regulating module is used to adjust the pressure of the gas inside the density relay, causing the microswitch of the density relay to close or open. At the corresponding moment when the microswitch closes or opens, the pressure and temperature of the gas inside the density relay are simultaneously collected by the pressure and temperature sampling module, and the action value and return value of the microswitch are obtained based on the collected pressure and temperature. The wireless information transceiver module is used to input the action value and return value of the density relay micro switch obtained from the verification into the host computer for reference by maintenance personnel; The power supply module is used to supply power to the intelligent control unit, pressure regulation module, pressure and temperature sampling module, gas path shut-off module, wireless information transceiver module, and online verification contact sampling module.

7. A wireless self-diagnostic intelligent gas density relay according to claim 6, characterized in that: In the initial state, the low-stiffness Baden tube is in the initial position, and the pre-charge pressure P0 of the first sealed air chamber is 0.01 MPa greater than the internal pressure of the low-stiffness Baden tube. The low-stiffness Baden tube moves inward and bends. When SF6 gas from electrical equipment is introduced into the low-stiffness Baden pipe through the one-way valve: When the pressure inside the low-stiffness Baden tube is less than the pre-charge pressure P0 of the first sealed air chamber, the low-stiffness Baden tube remains in its initial position. When the gas pressure entering the low-stiffness Baden tube is greater than or equal to the pre-charge pressure P0 of the first sealed air chamber, the low-stiffness Baden tube moves outward; until the internal pressure of the low-stiffness Baden tube increases to the pressure corresponding to the limit pressure point, the external limit device prevents the low-stiffness Baden tube from continuing to move outward. When electrical equipment leaks SF6 gas: When the pressure inside the low-rigidity Baden tube is greater than the pre-charge pressure P0+0.1MPa of the first sealed air chamber, the low-rigidity Baden tube remains in contact with the external limiting device. When the pre-charge pressure P0 of the first sealed air chamber is less than the pressure inside the low-rigidity Baden tube and less than the pre-charge pressure P0 + 0.1 MPa of the first sealed air chamber, the low-rigidity Baden tube moves inward, causing the first crossbeam, the first adjusting rod, and the second adjusting rod to move inward synchronously. When the pressure inside the low-stiffness Baden tube drops to the first micro switch warning threshold, the first adjusting rod triggers the first micro switch to issue a low air pressure alarm signal. When the pressure inside the low-stiffness Baden tube drops to the second microswitch lockout threshold, the second adjusting rod triggers the second microswitch to send a lockout signal. When the pressure inside the low-stiffness Baden tube is less than or equal to the pre-charge pressure P0-0.01MPa of the first sealed air chamber, the pressure relief valve closes, the pressure inside the low-stiffness Baden tube remains stable, the pressure difference between the inside and outside of the low-stiffness Baden tube remains constant, and the low-stiffness Baden tube stops moving inward.

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