Method for preventing low-temperature liquefaction false alarm of SF6 gas density relay

Abstract

The invention relates to the technical field of electric power, and discloses a low-temperature liquefaction false alarm prevention method for an SF6 gas density relay, which is characterized in that a hump bulge of a liquefaction false alarm prevention limiting control rod is matched with an arc-shaped surface of an end seat, so that when the SF6 gas density is in a certain specific interval in a low-temperature environment, the end seat can be prevented from being damaged; and the alarm contact of the gas density relay cannot be triggered by mistake. According to the method, an original SF6 gas density relay is slightly modified, so that the problem of false alarm of the SF6 gas density relay caused by low-temperature liquefaction of SF6 gas is solved, safe operation of a power grid is effectively guaranteed, and meanwhile, the working intensity of operation and maintenance personnel is relieved.

Description

Technical Field

[0001] The invention relates to the technical field of electric power, and in particular to a method for preventing a SF6 gas density relay from false alarming due to low temperature liquefaction. Background Art

[0002] With the development of my country's economy and the improvement of people's living standards, the power industry has been booming and the capacity of the power system has expanded rapidly. In the process of power generation, transformation, transmission, distribution and delivery, the number of electrical equipment used has also increased dramatically. In this case, how to ensure the safe and reliable operation of the power system has become particularly important. Especially in the high-voltage field, due to the huge value of electrical equipment, once an accident occurs, it will have a wide range of impacts and serious consequences. Therefore, it is crucial to ensure the safety of electrical equipment in the high-voltage field.

[0003] SF6 is a gas with good insulation and arc extinguishing properties and is widely used in high voltage fields. Currently, most high voltage equipment on the market uses SF6 as insulation gas. The SF6 content directly affects the insulation and arc extinguishing performance of the equipment. If the SF6 gas density is reduced to a certain level, the insulation and arc extinguishing performance will be lost, resulting in huge direct losses and inestimable indirect losses.

[0004] Therefore, when operating important electrical equipment, SF6 density relays are equipped to monitor the SF6 gas content inside the electrical equipment. When the gas pressure of the equipment is too low, the density relay will send out an alarm or lockout signal to notify the operation and maintenance personnel to deal with the problem. However, my country has a vast territory, with a distance of more than 5,000 kilometers from north to south and from east to west, and a large difference in climate between east and west and north and south. For example, in winter, the temperature in northern my country can drop below minus 40°C. According to the characteristics of SF6, under such weather conditions, when the SF6 gas pressure is higher than a certain value, liquefaction will occur, resulting in a decrease in the SF6 gas pressure inside the electrical equipment. If the pressure of the electrical equipment continues to decrease, the SF6 density relay will trigger an alarm signal to notify the operation and maintenance personnel to perform maintenance. When the temperature warms up and the temperature rises, the liquid SF6 gas will be converted into a gaseous state. The temperature changes periodically every day. When the temperature of the electrical equipment is lower than a certain threshold, the density relay will send out an alarm signal until the temperature rises to a certain value, and the liquid SF6 is converted into a gaseous state. The density relay will release the alarm signal only when the gaseous SF6 gas exceeds the alarm setting value at 20°C. During this period, if the operation and maintenance personnel receive a false alarm signal, they need to go to the site to confirm whether it is safe and inflate the electrical equipment. This will cause the SF6 gas pressure of the electrical equipment to be too low when the temperature is low, and the operation and maintenance personnel need to inflate the electrical equipment. When the temperature is high, due to excessive gas being filled, there is too much gas in the gas chamber of the electrical equipment, and the pressure increases sharply, which will also cause unsafe factors.

[0005] Therefore, how to use an SF6 gas density relay that can prevent false alarms of liquefaction in its safety range in low-temperature areas has become a problem that technicians in this field need to solve urgently. At present, the liquefaction alarm problem is mainly solved by operation and maintenance personnel going to the site to replenish gas, but the problem is not solved from the product itself, which brings great trouble to the operation and maintenance work. Therefore, there is an inherent demand for providing a method for preventing false alarms of liquefaction of SF6 gas density relays at low temperatures. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preventing false alarms of SF6 gas density relays due to low-temperature liquefaction, thereby reducing false alarms caused by SF6 gas liquefaction during the use of the SF6 gas density relay, ensuring the safe operation of the power grid while reducing the workload of operation and maintenance personnel.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for preventing a SF6 gas density relay from false alarm due to low temperature liquefaction, the SF6 gas density relay comprising a housing and a core assembly arranged in the housing, the core assembly comprising a Baden tube, an end seat, a movement, a temperature compensation sheet, a pointer and a magnetic auxiliary electric contact, wherein one end of the end seat is fixed to the end of the Baden tube, and the other end of the end seat is connected to one end of the temperature compensation sheet; the method for preventing a false alarm due to low temperature liquefaction comprises:

[0009] The surface of the end seat close to one end of the Baden tube is set to be a convex arc surface;

[0010] A liquefaction-proof false alarm limit control rod is added to the watch movement assembly, one end of the liquefaction-proof false alarm limit control rod is fixedly arranged on the rotating shaft of the movement, and the other end extends to the bottom of the arc-shaped surface of the end seat, and a hump protrusion is provided on the liquefaction-proof false alarm limit control rod, and the hump protrusion is a structure formed by a smooth protrusion of the anti-liquefaction false alarm limit control rod toward the outer edge of the arc-shaped surface of the end seat, and a first arc-shaped surface and a second arc-shaped surface that are concave relative to the hump protrusion are formed on both sides of the top of the hump protrusion, and the first arc-shaped surface is closer to the arc-shaped surface of the end seat than the second arc-shaped surface;

[0011] When the air temperature does not reach the liquefaction temperature of SF6 gas, there is a gap between the arc surface of the end seat and the first arc surface of the anti-liquefaction false alarm limit control rod, and the SF6 gas density relay normally monitors the SF6 gas density value in the electrical equipment;

[0012] When the SF6 gas in the electrical equipment reaches the liquefaction temperature, the gas pressure in the electrical equipment decreases as the temperature decreases, and the pressure in the Baden tube decreases, causing the end seat to move toward the hump of the anti-liquefaction false alarm limit control rod, and the distance between the end seat arc surface and the first arc surface is reduced;

[0013] Before the magnetic assist type electric contact triggers the alarm, the first arc surface of the anti-liquefaction false alarm limit control rod contacts the arc surface of the end seat, the hump prevents the end seat from continuing to move inward, and the Baden tube remains relatively static;

[0014] When the SF6 gas density in the electrical equipment drops to the alarm threshold, the magnetic auxiliary electric contact does not trigger the alarm action because the end seat is blocked by the hump of the anti-liquefaction false alarm limit control rod;

[0015] As the temperature drops further, the SF6 gas in the electrical equipment continues to liquefy, and the apex of the end seat arc surface gradually moves toward the apex of the hump of the anti-liquefaction false alarm limit control rod. When the SF6 gas density drops to the preset release threshold of the anti-liquefaction false alarm control, the apex of the end seat arc surface contacts the apex of the hump of the anti-liquefaction false alarm limit control rod and is in a critical state.

[0016] If the SF6 gas inside the electrical equipment continues to liquefy, the Baden tube will further deform inward, causing the arc surface of the end seat to continue to move inward, break away from the hump of the anti-liquefaction false alarm limit control lever, and slide toward the second arc surface. At this time, the SF6 gas pressure value of the electrical equipment measured by the SF6 gas density relay is the actual SF6 gas pressure value.

[0017] In a preferred embodiment, the method also includes: when the vertex of the arc surface of the end seat is separated from the vertex of the hump protrusion and placed behind the second arc surface, when the pressure of the gaseous SF6 remaining after the electrical equipment is liquefied is lower than the locking threshold, the magnetic-assisted electric contact triggers an alarm action. At this time, the secondary circuit sends a locking signal to the background to control the electrical equipment to be locked and stop working.

[0018] In a preferred embodiment, the method further comprises:

[0019] Preset a false alarm interval for preventing liquefaction for the SF6 gas density relay, where the false alarm interval is when the density value of the SF6 gas in the gaseous state is higher than the blocking threshold and lower than the alarm threshold; and

[0020] The position of the free end of the anti-liquefaction false alarm limit control rod is determined. The position can ensure that before the gas density value of the SF6 gas in the Baden tube drops to the alarm threshold, the first arc surface of the hump protrusion contacts the arc surface of the end seat, and when the gas density value of the SF6 gas in the Baden tube drops to the anti-liquefaction false alarm interval, the hump protrusion can prevent the arc surface of the end seat from sliding from the first arc surface to the second arc surface, thereby making the contacts of the magnetic-assisted electric contacts non-conductive.

[0021] In a preferred embodiment, the method further includes: as the air temperature rises, the liquefied SF6 gas gradually returns to a gaseous state. During this process, the mechanism action process of the meter core assembly is opposite to that during liquefaction, ultimately restoring the SF6 gas density relay to a normal monitoring state.

[0022] In a more preferred embodiment, the method further comprises:

[0023] When the liquefied SF6 gas begins to return to its gaseous state, the gas pressure inside the electrical equipment gradually increases;

[0024] The pressure in the Baden tube increases, causing the second arc surface of the self-liquefaction false alarm limit control rod of the arc surface of the end seat to move toward the vertex of the hump;

[0025] When the SF6 gas density rises to the set control threshold for releasing the false alarm of anti-liquefaction, the vertex of the arc surface of the end seat contacts the vertex of the hump of the limit control rod of the false alarm of anti-liquefaction and is in a critical state;

[0026] As the temperature further increases, the end seat arc surface passes over the top of the hump and is placed inside the first arc surface with surface-to-surface contact;

[0027] When the SF6 gas inside the electrical equipment continues to return to the gaseous state, the Baden tube gradually returns to its original state, the arc surface of the end seat separates from the first arc surface of the anti-liquefaction false alarm limit control rod, and the SF6 gas density relay returns to the normal monitoring state.

[0028] In a preferred embodiment, the temperature compensation element is an Ω-type bimetallic temperature compensation sheet.

[0029] In a preferred embodiment, the gas density relay includes a density relay with an indication or a density relay without an indication, wherein the density relay with an indication includes a density relay with a pointer display, a density relay with a digital display, or a density relay with a liquid crystal display.

[0030] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0031] The present invention provides a method for preventing false alarms of SF6 gas density relays due to low-temperature liquefaction, which is used to prevent the SF6 gas density relays from sending false alarm signals due to liquefaction of SF6 gas in electrical equipment under low-temperature environments. The technical solution of this application makes slight changes to the existing density relays, so that the alarm contacts of the SF6 gas density relay will not be falsely triggered within a certain density range at low temperatures. When the temperature rises, the liquefied SF6 gas in the electrical equipment will re-gasify, causing the SF6 gas pressure to increase, thereby restoring the SF6 gas density relay to a normal working state.

[0032] The technical solution of this application has the following benefits: First, in a low-temperature environment, when SF6 gas is liquefied, if the density value of the gaseous SF6 gas (at 20°C) is lower than the alarm pressure value but higher than the locking pressure value, the SF6 gas density relay will not falsely alarm, thereby reducing the number of maintenance personnel going to the site for unnecessary safety confirmation work. Second, this method is simple and reliable, and only requires minor changes to the original density relay to achieve it, and the increased cost is negligible relative to the entire density relay. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 It is a structural schematic diagram of an SF6 density relay with a low-temperature liquefaction prevention false alarm function in an embodiment of the present invention;

[0035] Figure 2 It is a structural schematic diagram of a meter core assembly of an SF6 density relay with a low-temperature liquefaction prevention false alarm function in an embodiment of the present invention;

[0036] Figure 3 It is a schematic diagram of the positional relationship between the liquefaction prevention false alarm limit control rod and the end seat arc surface when an SF6 density relay with a low-temperature liquefaction prevention false alarm function is in a normal working state in an embodiment of the present invention;

[0037] Figure 4 It is a schematic diagram of the positional relationship between the anti-liquefaction false alarm limit control rod and the arc surface of the end seat when the SF6 density relay with low-temperature anti-liquefaction false alarm function is in the anti-liquefaction false alarm state in the embodiment of the present invention;

[0038] Figure 5 It is a schematic diagram of the positional relationship between the anti-liquefaction false alarm limit control rod and the arc surface of the end seat when the SF6 density relay with low-temperature anti-liquefaction false alarm function is in the liquefaction trigger alarm action state in the embodiment of the present invention;

[0039] Figure 6 (a)-(d) are schematic diagrams showing the relative position relationship between the arc surface of the end seat and the hump protrusion of the liquefaction prevention false alarm limit control lever during the liquefaction triggering alarm process of an SF6 density relay with a low-temperature liquefaction prevention false alarm function in an embodiment of the present invention;

[0040] Figure 72 is a schematic diagram of the structure of another SF6 density relay with a low-temperature liquefaction prevention false alarm function according to an embodiment of the present invention;

[0041] Figure 8 It is a structural schematic diagram of an intelligent remote transmission module of another SF6 density relay with low-temperature liquefaction prevention false alarm function in an embodiment of the present invention.

[0042] Legend:

[0043] 1. Connector; 2. Case; 3. Cover;

[0044] 4. Meter core assembly; 401. Baden tube of pressure measuring element; 402. End seat; 403. Movement; 404. Pointer; 405. Magnetic auxiliary electric contact; 406. Ω-type bimetallic temperature compensation sheet; 407. Limit control lever for preventing false alarm of liquefaction;

[0045] 5. Dial; 6. Junction box; 7. Intelligent remote transmission module; 8. Case assembly; 9. Remote transmission junction box. DETAILED DESCRIPTION

[0046] In order to make the above and other features and advantages of the present invention more clear, the present invention is further described below in conjunction with the accompanying drawings. It should be understood that the specific embodiments given herein are for the purpose of explaining to those skilled in the art and are only exemplary and not restrictive.

[0047] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0048] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0049] SF6 gas density relay (or SF6 gas density monitoring device) is a device for monitoring the density of SF6 gas in electrical equipment. It is a pressure measuring device with electrical contact output characteristics after temperature compensation. The density of SF6 gas on SF6 electrical equipment is expressed by the pressure of SF6 gas after temperature compensation, that is, the pressure value at 20°C. It can be seen from the basic physical properties of SF6 gas that it is a gas that is easier to liquefy than air. The state of SF6 depends on its parameters such as pressure and temperature.

[0050] In low-temperature areas (such as Xinjiang, Inner Mongolia, northern Hebei and Northeast China), the winter temperature is extremely low, and the outdoor temperature can even reach -40℃ or lower. In such an environment, the SF6 gas in SF6 high-voltage electrical equipment is easy to liquefy, causing the gas density and pressure to gradually decrease. This liquefaction phenomenon is the main reason for the SF6 gas density relay to generate false alarms.

[0051] Generally, it is not allowed to add SF6 gas when the gas is in a liquefied state. This is because after adding, the pressure will increase, causing the liquefaction point to increase as well. The added gas will liquefy immediately, and the density and pressure of the gas cannot be increased. When the temperature rises, the liquefied SF6 will vaporize, causing the pressure inside the gas chamber to rise abnormally, exceeding the allowable pressure range. This will cause unnecessary stress on the sealing parts inside the equipment, causing damage to the sealing parts, thus causing SF6 gas leakage.

[0052] In order to solve this problem, the present application provides a method for preventing false alarms of SF6 gas density relays due to low temperature liquefaction. The method makes minor changes to the original SF6 gas density relay, thereby reducing false alarms caused by SF6 gas liquefaction during use, and solves the problem of false alarms of SF6 gas density relays due to low temperature liquefaction of SF6 gas from the perspective of the product itself. This can not only ensure the safe operation of the power grid, but also reduce the workload of operation and maintenance personnel.

[0053] Embodiment 1:

[0054] like Figure 1 , Figure 2 As shown, an SF6 gas density relay of this embodiment is mainly composed of a connector 1, a case 2, a cover 3, a core assembly 4, a dial 5, and a junction box 6, wherein the case 2 and the cover 3 constitute the housing of the SF6 gas density relay. The connector 1 is fixed on the case 2, the core assembly 4 is installed in the case 2, the cover 3 is sealed at the port of the case 2, the dial 5 is arranged in the cover 3, and the junction box 6 is installed on the case 2.

[0055] The meter core assembly 4 includes a pressure measuring element Baden tube 401 (or simply Baden tube), an end seat 402, a movement 403, a pointer 404, a magnetic auxiliary electric contact 405, an Ω-type bimetallic temperature compensation sheet 406, and an anti-liquefaction false alarm limit control rod 407. Among them, one end of the pressure measuring element Baden tube 401 is sealed and welded to one end of the joint 1, and the other end of the joint 1 is installed at the interface of the gas chamber of the electrical equipment to be tested. The pressure measuring element Baden tube 401 and the joint 1 form a sealed cavity to form an internal gas passage. The gas in the electrical equipment can be transmitted to the pressure measuring element Baden tube 401 of the meter core assembly 4 through the joint 1, so that the pressure on the pressure measuring element Baden tube 401 is equal to the gas pressure in the electrical equipment. The other end of the pressure measuring element Baden tube 401 and one end of the Ω-type bimetallic temperature compensation sheet 406 are fixed on the end seat 402, and the other end of the Ω-type bimetallic temperature compensation sheet 406 is fixedly connected to the movement 403. The pointer 404 is mounted on the movement 403, and the magnetic-assisted electric contact 405 and the movement 403 are fixed to the joint 1 by screws. The pressure measuring element Baden tube 401 and the Ω-type bimetallic temperature compensation sheet 406 interact with each other to monitor the gas density value, and the position of the contact paddle of the magnetic-assisted electric contact 405 can be adjusted to set the position point corresponding to the alarm and locking pressure parameters of the electrical equipment.

[0056] When the gas density of the electrical equipment decreases, the pressure measuring element Baden tube 401 will produce a downward displacement, and the movement 403 drives the pointer 404 to rotate in the direction of pressure reduction through the connected Ω-type bimetallic temperature compensation sheet 406. When the pointer 404 rotates to the set alarm or lock point, the contact of the magnetic auxiliary electric contact 405 is turned on, generating an electrical signal at the corresponding position, thereby realizing the alarm or lock function. At the same time, the pointer 404 displays the current gas density value in the electrical equipment on the dial 5.

[0057] The SF6 gas density relay in this embodiment is a minor modification of the original SF6 gas density relay: an outwardly protruding arc surface (or an outwardly convex arc surface) is provided on the surface of one end of the Baden tube 401 of the end seat 402 connected to the pressure measuring element; the anti-liquefaction false alarm limit control rod 407 is a structure added to the watch core assembly 4, one end of which is fixed on the rotating shaft of the movement 403, and the other end is a free end, extending to the bottom of the arc surface of the end seat 402. Among them, a hump protrusion is provided on the free end, and the hump protrusion is a structure formed by a smooth protrusion of the free end toward the outer edge of the arc surface of the end seat 402. The top two sides of the hump protrusion form a first arc surface (or a first concave arc surface) and a second arc surface (or a second concave arc surface) that are concave relative to the hump protrusion, and the first arc surface is closer to the end seat 402 than the second arc surface. When the SF6 gas in the electrical equipment is liquefied under low temperature, the hump of the anti-liquefaction false alarm limit control rod 407 can block the end seat 402 from moving downward due to the reduction of the SF6 gas liquefaction pressure in a certain density range under low temperature, thereby preventing the Ω-type bimetallic temperature compensation sheet 406 from driving the movement 403 to rotate the pointer 404 and triggering the contact of the magnetic auxiliary electric contact 405 to be turned on. Therefore, even if the SF6 gas in the electrical equipment is liquefied and the SF6 gas density reaches the alarm threshold, the SF6 gas density relay will not issue a false alarm signal.

[0058] The principle of SF6 gas density relay (density relay for short):

[0059] The gas circuit inside the density relay is connected to the gas chamber of the electrical equipment. The air pressure inside the density relay is equal to the air pressure inside the gas chamber of the electrical equipment. 20) changes, the density relay can follow the changes in real time. The working principle of the density relay is: the gas in the electrical equipment body flows into the pressure measuring element Baden tube 401 in the meter core assembly 4 through the joint 1, and the pressure of the pressure measuring element Baden tube 401 and the pressure of the electrical equipment body air chamber are always kept equal. As the gas pressure inside the electrical equipment increases or decreases, the pressure measuring element Baden tube 401 will expand outward or contract inward accordingly (the reference direction is the center of its own curvature), and the end seat 402 and the Ω-type bimetallic temperature compensation sheet 406 will move with the movement of the pressure measuring element Baden tube 401. For example, when the gas pressure inside the electrical device increases, the pressure measuring element Baden tube 401 expands outward (the reference direction is the center of its own curvature), the end seat 402 and the Ω-type bimetallic temperature compensation plate 406 move outward with the movement of the pressure measuring element Baden tube 401, and the other end of the Ω-type bimetallic temperature compensation plate 406 pulls the movement 403, causing the pointer 404 to rotate clockwise, thereby increasing the indication of the pointer 404; when the gas in the electrical device leaks or liquefies, the gas pressure inside the electrical device decreases. At this time, the gas pressure in the pressure measuring element Baden tube 401 also decreases, the pressure measuring element Baden tube 401 contracts inward, the end seat 402 and the Ω-type bimetallic temperature compensation plate 406 move inward with the movement of the pressure measuring element Baden tube 401, and the other end of the Ω-type bimetallic temperature compensation plate 406 pushes the movement 403, causing the pointer 404 to rotate counterclockwise, thereby reducing the indication of the pointer 404. When the air pressure of the electrical equipment drops to the alarm threshold value preset by the magnetic-assisted electric contact 405, the contact is turned on, and an alarm signal indicating that the air pressure of the electrical equipment is too low is issued, notifying the operation and maintenance personnel to perform maintenance. If the air pressure drops further and reaches the locking threshold value preset by the magnetic-assisted electric contact 405, the contact is turned on, and a locking signal indicating that the air pressure of the electrical equipment no longer meets the safety working conditions is issued. To ensure safety, the electrical equipment will be linked and stop working.

[0060] Low temperature alarm situation:

[0061] In the cold winter, when the temperature reaches the liquefaction temperature of SF6, the SF6 gas in the electrical equipment will liquefy due to the temperature drop, which leads to the reduction of SF6 gas in the electrical equipment and the reduction of SF6 gas pressure, which in turn reduces the displayed value of the density relay. The pressure measuring element Baden tube 401 in the density relay will move inward, and the end seat 402 and the Ω-type bimetallic temperature compensation sheet 406 will also move inward with the pressure measuring element Baden tube 401. The other end of the Ω-type bimetallic temperature compensation sheet 406 pushes the movement 403, causing the pointer 404 to rotate counterclockwise, and the distance between the pointer 404 and the magnetic assist type electric contact 405 paddle contact gradually decreases. If the temperature continues to drop, when the magnetic assist type electric contact 405 paddle contact is turned on, a liquefaction false alarm signal will be issued. At this time, the operation and maintenance personnel will receive an alarm signal of insufficient SF6 gas, and the operation and maintenance personnel need to inflate the equipment. However, when the temperature rises above the liquefaction temperature, the liquefied SF6 gas will return to a gaseous state. At this time, the amount of SF6 gas inside the electrical equipment may far exceed the amount required for operation, and there may be operational risks. Therefore, the operation and maintenance personnel need to restore the gas pressure value of the electrical equipment to the rated value, which brings great trouble to the operation and maintenance work.

[0062] Methods for preventing false alarms of SF6 gas density relays due to low temperature liquefaction:

[0063] The SF6 gas density relay in this embodiment has made minor changes to the existing density relay: 1) the surface of the end seat 402 close to one end of the Baden tube 401 is set as a convex arc surface; 2) an anti-liquefaction false alarm limit control rod 407 is added to the meter core assembly, one end of the anti-liquefaction false alarm limit control rod is fixed on the rotating shaft of the movement 403, and the other end extends to the bottom of the arc surface of the end seat 402, and a hump is provided on the anti-liquefaction false alarm limit control rod 407. In this embodiment, the hump of the anti-liquefaction false alarm limit control rod 407 cooperates with the arc surface of the end seat 402 in a low temperature environment, so that the alarm contact of the density relay will not be triggered when the SF6 gas density is within a certain range.

[0064] Figure 3 The figure shows the relative position of the actuator of the low-temperature type liquefaction-proof false alarm SF6 gas density relay during normal monitoring. Before the air temperature reaches the liquefaction temperature of SF6 gas, the pressure measuring element Baden tube 401, the end seat 402, the Ω-type bimetallic temperature compensation sheet 406, the movement 403, the pointer 404 and the magnetic assist type electric contact 405 form a motion mechanism. There is no direct contact between the end seat 402 and the liquefaction-proof false alarm limit control rod 407, and a certain gap distance is maintained. In this way, the pressure measuring element Baden tube 401 can move freely as the gas pressure inside the electrical equipment body increases or decreases.

[0065] like Figure 4 , Figure 5 , Figure 6 As shown in (a)-(d), a schematic diagram of the relative position of the actuator of the low-temperature type anti-liquefaction false alarm SF6 gas density relay in the anti-false alarm state when the SF6 gas is liquefied and the liquefaction trigger alarm state is shown. When the SF6 gas in the electrical equipment reaches the liquefaction temperature, the gas pressure in the electrical equipment decreases as the temperature decreases, and the pressure in the pressure measuring element Baden tube 401 decreases, causing the end seat 402 to move in the direction of the hump protrusion of the anti-liquefaction false alarm limit control rod 407. Before the magnetic auxiliary electric contact 405 triggers the alarm, the hump protrusion of the anti-liquefaction false alarm limit control rod 407 contacts the arc surface of the end seat 402, preventing the pressure measuring element Baden tube 401 from continuing to move inward. As the ambient temperature further decreases, the apex of the arc surface of the end seat 402 gradually approaches the apex of the hump protrusion of the anti-liquefaction false alarm limit control rod 407. When the SF6 gas pressure (at 20°C) drops to the set control threshold for releasing the anti-liquefaction false alarm, the vertex of the arc surface of the end seat 402 is in a critical state of contact with the vertex of the hump of the anti-liquefaction false alarm limit control rod 407. At this time, if the SF6 gas inside the electrical equipment continues to liquefy, the pressure measuring element Baden tube 401 will further deform inward, causing the end seat 402 to continue to move inward and break away from the vertex of the hump of the anti-liquefaction false alarm limit control rod 407. In this case, the SF6 gas pressure value of the electrical equipment measured by the density relay is the actual SF6 gas pressure value (at 20°C). When the remaining gaseous SF6 gas pressure after the electrical equipment is liquefied is lower than the locking pressure value, the magnetic auxiliary electric contact 405 triggers the alarm action, and the secondary circuit will send a locking signal to the background to control the electrical equipment to be linked and locked and stop working. As the temperature rises, the liquefied SF6 gas gradually returns to its gaseous state, and the density relay also returns to its normal monitoring state. The mechanism action process of the meter core assembly 4 is opposite to that during liquefaction, and eventually the density relay returns to its normal monitoring state.

[0066] In this embodiment, in order to explain the technical solution of the present invention more clearly, the following examples are given for illustration.

[0067] Assume there is a density relay with parameters of 0.50 / 0.45 / 0.40, its rated value is 0.50MPa, alarm value is 0.45MPa, lock value is 0.40MPa, and the anti-liquefaction false alarm interval is set to 0.41~0.46MPa. The following is the action process of the density relay under different pressure and temperature conditions:

[0068] Electrical equipment is filled with 0.50MPa SF6 gas. When the temperature of SF6 gas drops to -33℃, part of SF6 gas begins to liquefy. As the temperature continues to drop, more and more SF6 gas is liquefied.

[0069] The pressure in the pressure measuring element Baden tube 401 decreases with the liquefaction process, causing the end seat 402 to move toward the hump of the anti-liquefaction false alarm limit control rod 407. When the SF6 gas pressure drops to 0.46MPa, the hump of the anti-liquefaction false alarm limit control rod 407 contacts the arc surface of the end seat 402 and prevents the end seat 402 from continuing to move inward. At this time, the pressure measuring element Baden tube 401 remains relatively stationary.

[0070] As the temperature further decreases, the SF6 gas pressure continues to decrease to 0.45 MPa. Since the end seat 402 is blocked by the hump of the anti-liquefaction false alarm limit control rod 407, the Ω-type bimetallic temperature compensation sheet 406 will not follow the displacement of the end seat 402, and the movement 403 will not drive the pointer 404 to rotate. Therefore, the magnetic auxiliary electric contact 405 will not trigger the alarm action.

[0071] When the temperature of SF6 gas further drops and the pressure of gaseous SF6 gas drops to 0.41MPa, the pressure measuring element Baden tube 401 further deforms inward, causing the end seat 402 to break away from the hump apex of the anti-liquefaction false alarm limit control rod 407. At this time, the Ω-type bimetallic temperature compensation sheet 406 follows the displacement of the end seat 402, and the movement 403 drives the pointer 404 to rotate counterclockwise. Finally, the magnetic auxiliary electric contact 405 contacts are turned on, and a low pressure alarm signal is sent to the background, notifying the operation and maintenance personnel to perform maintenance.

[0072] When the temperature rises, the density relay will return to normal monitoring status.

[0073] Through the above technical solutions, the design of the anti-liquefaction false alarm limit control rod and the end seat can effectively prevent the false alarm caused by the liquefaction of SF6 gas. When the SF6 gas pressure drops below the alarm threshold, the hump will block the downward displacement of the end seat, thereby avoiding the movement of the movement and triggering the magnetic auxiliary electric contact to be misconnected. In this way, even if the SF6 gas density reaches the preset alarm threshold, the density relay will not issue a false alarm signal.

[0074] Embodiment 2:

[0075] See also Figure 7 and Figure 8 As shown in the structural diagram, the difference between the second embodiment and the first embodiment lies in the design of the density relay. In addition to the mechanical structure of the first embodiment, the second embodiment further adds an intelligent remote transmission module 7, a case assembly 8 and a remote transmission junction box 9. The case assembly 8 is connected to the case 2 described in the first embodiment, and the connection method can be direct contact connection or other forms. The intelligent remote transmission module 7 is installed inside the case assembly 8, and the remote transmission junction box 9 is installed on the case assembly 8.

[0076] The working principle of this low-temperature type liquefaction-proof false alarm intelligent SF6 gas density relay is exactly the same as that of the first embodiment. When the SF6 gas pressure drops below the alarm threshold, the hump will block the downward displacement of the end seat 402, thereby preventing the movement 403 from rotating and triggering the magnetic auxiliary electric contact 405 to conduct. In this way, even if the SF6 gas density reaches the alarm threshold, the density relay will not issue a false alarm signal.

[0077] By adding the intelligent remote transmission module 7 and the remote transmission junction box 9, the density relay can transmit the SF6 gas density data to the remote monitoring system by wireless or wired means, realizing remote monitoring and data collection. In this way, the SF6 gas density can be conveniently monitored and analyzed in real time, thus improving the operating efficiency and safety of the equipment.

[0078] Specifically, the intelligent remote transmission module 7 is composed of multiple components, including a micro intelligent processor, a pressure sensor, a temperature sensor, a communication module and a power module. The processor can be a general-purpose computer, an industrial computer, a CPU, a single-chip microcomputer, an ARM chip, an AI chip, an MCU, an FPGA, a PLC, an industrial control mainboard, an embedded main control board, and other intelligent integrated circuits. The power module can select a switching power supply, an AC 220V or a DC power supply, or an LDO (low voltage difference linear regulator), a programmable power supply, a solar panel, a battery or a rechargeable battery. The pressure sensor can be various types of pressure sensing elements, such as a pressure sensor and a pressure transmitter. The temperature sensor can be of various types, including thermocouples, thermistors and semiconductor sensors. They can be divided into two types: contact and non-contact. In terms of sensor materials and electronic component characteristics, temperature sensors often use thermal resistors and thermocouples. In short, temperature acquisition can be achieved by using various temperature sensing elements, such as temperature sensors, temperature transmitters, etc. The communication module can communicate by wire or wirelessly. Wired communication methods include industrial buses such as RS232, RS485, CAN-BUS, fiber optic Ethernet, 4-20mA, Hart, IIC, SPI, Wire, coaxial cable and PLC power carrier, etc. Wireless communication methods include mobile networks such as 2G / 3G / 4G / 5G, WIFI, Bluetooth, Lora, Lorawan, Zigbee, infrared, ultrasonic, sound waves, satellite communication, light wave transmission and quantum communication, etc. In addition, wireless communication can be carried out using the 5G / NB-IOT communication module (such as NB-IOT) built into the sonar and sensor.

[0079] Among them, pressure sensors can be divided into absolute pressure sensors, relative pressure sensors, or sensors with both absolute and relative pressure measurement functions. The quantity can be determined according to actual needs. Pressure sensor forms include diffused silicon pressure sensors, MEMS (micro-electromechanical systems) pressure sensors, chip-type pressure sensors, coil induction pressure sensors (such as Baden tubes with induction coils) and resistive pressure sensors (such as Baden tubes with sliding wire resistors). These sensors can have analog output or digital output. When collecting pressure, various types of pressure elements can be used, such as diffused silicon, sapphire, piezoelectric, and strain gauges (including resistance strain gauges and ceramic strain gauges). In addition, devices such as pressure transmitters can be used for signal conversion and amplification.

[0080] The intelligent remote transmission module 7 monitors the gas pressure P and temperature T of the electrical equipment through the pressure sensor and the temperature sensor, and calculates the corresponding 20°C pressure value P 20 (i.e., gas density value). The intelligent remote transmission module 7 can compare the error performance of the gas density relay at different temperatures and in different time periods to evaluate the performance of the gas density relay and electrical equipment. The density relay can display the density value on site in real time, or display the density value monitoring results through the background. The specific method can be flexibly selected according to the needs. The intelligent remote transmission module 7 has the function of real-time online display of density value, pressure value, temperature value and other data, and provides functions such as change trend analysis, historical data query and real-time alarm. It can monitor the gas density value online, or monitor the density value, pressure value and temperature value at the same time. In addition, the module also has a self-diagnosis function, which can report abnormal conditions in time, such as disconnection, short circuit alarm and sensor damage. The module can also compare the error performance of the gas density relay within the same temperature range in different time periods to evaluate the performance of the device, and provide a comparison of historical data with current data. In addition, it can also perform a physical examination on the density relay to evaluate whether the density value of the gas density relay and the monitored electrical equipment is normal. By determining and analyzing the normal and abnormal density values ​​of the electrical equipment itself, the gas density relay, the pressure sensor and the temperature sensor, it is possible to determine, compare and analyze the status of the electrical equipment gas density monitoring, the device itself and the gas density relay. The intelligent remote transmission module 7 may also include an analysis system (expert management analysis system) for detecting, analyzing and determining the problem points to evaluate the status of the gas density monitoring, gas density relay and monitoring elements. It may also monitor the contact signal status of the gas density relay and transmit its status remotely.

[0081] There are flexible ways to check the density relay, including: 1) On-site notice: For example, the status of the density relay is directly displayed on site through indicator lights, digital displays or LCD screens. 2) Online remote communication: The data of the density relay is uploaded to the background monitoring system through remote communication for real-time analysis and recording. 3) Wireless upload: Using wireless communication technology, the data of the density relay is wirelessly transmitted to a specific terminal device, such as a mobile phone or other mobile device. 4) Other ways of uploading: According to specific needs, other ways can be selected to upload the data of the density relay to a specified location or device. 5) Alarm signal line or dedicated signal line upload: The abnormal results are transmitted to the remote device or system through the alarm signal line or dedicated signal line for processing and recording. 6) Upload alone or bundled with other signals: The data of the density relay can be uploaded alone, or it can be transmitted and recorded together with other related signals. In short, the density relay can judge the gas status inside the electrical equipment and automatically issue an alarm when an abnormality occurs. These alarm information can be uploaded to the remote device or system in different ways, such as online monitoring platform, mobile phone, etc., and can also be displayed and alarmed on site to remind the on-site operator.

[0082] The method for preventing false alarm of low temperature liquefaction of SF6 gas density relay in the second embodiment is exactly the same as the method steps described in the first embodiment, and will not be repeated here.

[0083] It should be noted that the SF6 gas density relay in the present application may include a density relay with an indication (such as a density relay with a pointer display, a density relay with a digital display, or a density relay with a liquid crystal display), and may also include a density relay without an indication (i.e., a density switch).

[0084] In summary, the present invention provides a method for preventing false alarms of SF6 gas density relays from low temperature liquefaction, aiming to prevent false alarms when SF6 gas is liquefied. The technical solution of the present application makes slight changes to the original density relay, so that the hump protrusion of the anti-liquefaction false alarm limit control rod matches the arc surface of the end seat, so that in a low temperature environment, when the SF6 gas density is in a certain specific range, the alarm contact of the density relay will not be triggered. When the temperature rises, the liquefied SF6 gas in the electrical equipment will be re-gasified, resulting in an increase in the SF6 gas pressure, so that the density relay returns to a normal working state. The technical solution of the present application has the following benefits: First, in a low temperature environment, when SF6 gas is liquefied, if the density value of the gaseous SF6 gas (at 20°C) is lower than the alarm pressure value but higher than the locking pressure value, the SF6 gas density relay will not falsely alarm, thereby reducing the number of maintenance personnel going to the site for unnecessary safety confirmation work. Second, the method is simple and reliable, and only requires slight changes to the original density relay to be implemented, and the increased cost is negligible relative to the entire density relay.

[0085] The specific embodiments of the present invention are described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions made to the present invention are also within the scope of the present invention. Therefore, the equalization changes and modifications made without departing from the spirit and scope of the present invention should be included in the scope of the present invention.

Claims

1. A method for preventing false alarm of SF6 gas density relay from low temperature liquefaction, the SF6 gas density relay comprising a housing and a core assembly arranged in the housing, the core assembly comprising a Baden tube, an end seat, a movement, a temperature compensation sheet, a pointer and a magnetic auxiliary electric contact, wherein: One end of the end seat is fixed to the end of the Baden tube, and the other end of the end seat is connected to one end of the temperature compensation sheet; characterized in that the method for preventing false alarm of low temperature liquefaction includes: The surface of the end seat close to one end of the Baden tube is set to be a convex arc surface; A liquefaction-proof false alarm limit control rod is added to the watch movement assembly, one end of the liquefaction-proof false alarm limit control rod is fixedly arranged on the rotating shaft of the movement, and the other end extends to the bottom of the arc-shaped surface of the end seat, and a hump protrusion is provided on the liquefaction-proof false alarm limit control rod, and the hump protrusion is a structure formed by a smooth protrusion of the anti-liquefaction false alarm limit control rod toward the outer edge of the arc-shaped surface of the end seat, and a first arc-shaped surface and a second arc-shaped surface that are concave relative to the hump protrusion are formed on both sides of the top of the hump protrusion, and the first arc-shaped surface is closer to the arc-shaped surface of the end seat than the second arc-shaped surface; When the air temperature does not reach the liquefaction temperature of SF6 gas, there is a gap between the arc surface of the end seat and the first arc surface of the anti-liquefaction false alarm limit control rod, and the SF6 gas density relay normally monitors the SF6 gas density value in the electrical equipment; When the SF6 gas in the electrical equipment reaches the liquefaction temperature, the gas pressure in the electrical equipment decreases as the temperature decreases, and the pressure in the Baden tube decreases, causing the end seat to move toward the hump of the anti-liquefaction false alarm limit control rod, and the distance between the end seat arc surface and the first arc surface is reduced; Before the magnetic assist type electric contact triggers the alarm, the first arc surface of the anti-liquefaction false alarm limit control rod contacts the arc surface of the end seat, the hump prevents the end seat from continuing to move inward, and the Baden tube remains relatively static; When the SF6 gas density in the electrical equipment drops to the alarm threshold, the magnetic auxiliary electric contact does not trigger the alarm action because the end seat is blocked by the hump of the anti-liquefaction false alarm limit control rod; As the temperature drops further, the SF6 gas in the electrical equipment continues to liquefy, and the apex of the end seat arc surface gradually moves toward the apex of the hump of the anti-liquefaction false alarm limit control rod. When the SF6 gas density drops to the preset release threshold of the anti-liquefaction false alarm control, the apex of the end seat arc surface contacts the apex of the hump of the anti-liquefaction false alarm limit control rod and is in a critical state. If the SF6 gas inside the electrical equipment continues to liquefy, the Baden tube will further deform inward, causing the arc surface of the end seat to continue to move inward, break away from the hump of the anti-liquefaction false alarm limit control lever, and slide toward the second arc surface. At this time, the SF6 gas pressure value of the electrical equipment measured by the SF6 gas density relay is the actual SF6 gas pressure value.

2. The method for preventing false alarm of SF6 gas density relay from low temperature liquefaction according to claim 1, characterized in that: The method also includes: when the vertex of the arc surface of the end seat is separated from the vertex of the hump protrusion and placed behind the second arc surface, when the pressure of the gaseous SF6 remaining after the electrical equipment is liquefied is lower than the locking threshold, the magnetic auxiliary electric contact triggers an alarm action. At this time, the secondary circuit sends a locking signal to the background to control the electrical equipment to be linked and locked and stop working.

3. The method for preventing false alarm of SF6 gas density relay from low temperature liquefaction according to claim 1, characterized in that: The method further comprises: Preset a false alarm interval for preventing liquefaction for the SF6 gas density relay, where the false alarm interval is when the density value of the SF6 gas in the gaseous state is higher than the blocking threshold and lower than the alarm threshold; and The position of the free end of the anti-liquefaction false alarm limit control rod is determined. The position can ensure that before the gas density value of the SF6 gas in the Baden tube drops to the alarm threshold, the first arc surface of the hump protrusion contacts the arc surface of the end seat, and when the gas density value of the SF6 gas in the Baden tube drops to the anti-liquefaction false alarm interval, the hump protrusion can prevent the arc surface of the end seat from sliding from the first arc surface to the second arc surface, thereby making the contacts of the magnetic-assisted electric contacts non-conductive.

4. The method for preventing false alarm of SF6 gas density relay from low temperature liquefaction according to claim 1, characterized in that: The method also includes: as the temperature rises, the liquefied SF6 gas gradually returns to a gaseous state. During this process, the mechanism action process of the meter core component is opposite to that during liquefaction, and finally the SF6 gas density relay returns to a normal monitoring state.

5. The method for preventing false alarm of SF6 gas density relay from low temperature liquefaction according to claim 4, characterized in that: When the liquefied SF6 gas begins to return to its gaseous state, the gas pressure inside the electrical equipment gradually increases; The pressure in the Baden tube increases, causing the second arc surface of the self-liquefaction false alarm limit control rod of the arc surface of the end seat to move toward the vertex of the hump; When the SF6 gas density rises to the set control threshold for releasing the false alarm of anti-liquefaction, the vertex of the arc surface of the end seat contacts the vertex of the hump of the limit control rod of the false alarm of anti-liquefaction and is in a critical state; As the temperature further increases, the end seat arc surface passes over the top of the hump and is placed inside the first arc surface with surface-to-surface contact; When the SF6 gas inside the electrical equipment continues to return to the gaseous state, the Baden tube gradually returns to its original state, the arc surface of the end seat separates from the first arc surface of the anti-liquefaction false alarm limit control rod, and the SF6 gas density relay returns to the normal monitoring state.

6. The method for preventing false alarm of SF6 gas density relay from low temperature liquefaction according to claim 1, characterized in that: The temperature compensation element is an Ω-type bimetallic temperature compensation sheet.

7. The method for preventing false alarm of SF6 gas density relay from low temperature liquefaction according to claim 1, characterized in that: The gas density relay includes a density relay with an indication or a density relay without an indication, wherein the density relay with an indication includes a density relay with a pointer display, a density relay with a digital display, or a density relay with a liquid crystal display.

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