Self-source check type gas density relay

Abstract

The utility model provides a self-source verification type gas density relay, which comprises a piston unit, a temperature control chamber and a heating unit, and the temperature control chamber is filled with clean water; the piston unit is provided with a pressure sensor and a temperature sensor; a piston cylinder, a pressure sensor and a temperature sensor of the piston unit are all located in clean water, and a piston shaft extends out of the temperature control chamber; a piston cavity of the piston unit is communicated with the outside through an air delivery pipe; a valve is mounted on the gas conveying pipe; the heating unit acts on the piston cylinder. According to the density relay provided by the utility model, the clean water is surrounded outside the piston cylinder, and the heating unit is arranged outside the piston cylinder, so that a built-in ice-water mixture cavity can be formed at the periphery of the piston cylinder to provide a temperature standard source, and meanwhile, the built-in piston unit can provide dynamic density fitting and determine a plurality of pressure standard points to realize real self-checking; the self-checking convenience of the on-site density relay is improved, and the safe operation of power equipment is ensured.

Description

TECHNICAL FIELD

[0001] The utility model relates to SF6 insulation gas leakage monitoring technical field, specifically is a kind of self-source calibration formula gas density relay. BACKGROUND

[0002] Density relay can monitor SF6 insulation gas pressure and temperature in real time, calculate the insulation gas density at this time, when gas leakage causes gas density to drop to a certain degree, density relay will trigger alarm or lockout switch action, prevent insulation gas density too low to increase insulation breakdown risk.Therefore, the periodic calibration of density relay is necessary work to ensure the safety of power equipment.

[0003] Traditional density relay verification mode needs to connect density relay calibrator, and the value and function of density relay are verified, but the method has large workload, and frequent disassembly of pipeline can easily increase gas leakage risk.At the same time, most of the density relays with self-checking function currently change the size of piston cavity or gas temperature through built-in piston unit or temperature sensing cavity, so that the SF6 gas density in the density relay changes and approaches alarm / lockout point, but this kind of self-checking method can only detect whether the device can normally trigger alarm or lockout action when the gas density in the density relay drops to the set value, but the accuracy of the temperature and gas pressure value detected by the density relay is not checked, and the main problem of this kind of self-checking method is that there is no standard reference source for comparison, such as known constant standard temperature and determinable standard pressure value. SUMMARY

[0004] The technical problem to be solved by the utility model is how to improve the accuracy and convenience of self-checking of gas density relay.

[0005] The utility model solves the above technical problems by the following technical means:

[0006] Self-source calibration formula gas density relay, including piston unit, also including temperature control chamber, heating unit, the temperature control chamber is filled with clean water;The piston unit is provided with pressure sensor, temperature sensor;The piston cylinder of piston unit, pressure sensor, temperature sensor are all located in clean water, and piston shaft extends outside temperature control chamber;The piston cavity of piston unit is communicated with outside through gas conveying pipe;Valve is installed on the gas conveying pipe;The heating unit acts on piston cylinder.The utility model provides a kind of novel self-source calibration formula gas density relay, by surrounding clean water outside piston cylinder and heating unit outside piston cylinder, can form the ice-water mixture cavity that provides temperature standard source around piston cylinder, while built-in piston unit can provide dynamic density fitting, determine multiple pressure standard points to realize real self-checking, improve the convenience of self-checking of field density relay, and guarantee the safe operation of power equipment.

[0007] Further, the temperature control chamber comprises a closed shell, pure water is filled in the shell, and a refrigerator is fixed in the shell; the piston unit is fixed in the shell and immersed in the clean water, and the piston unit comprises a piston driving shaft, the piston driving shaft penetrates through the shell and is connected with the driving unit.

[0008] Further, the temperature control chamber further comprises a water bag; the water bag is located in the shell, and the pure water is located in the water bag; and the refrigerator is located between the water bag and the shell.

[0009] Further, the tail part of the piston unit is provided with an exhaust port, one end of the gas conveying pipe is sealingly connected with the exhaust port, and the other end of the gas conveying pipe penetrates through the shell and is sequentially provided with an electromagnetic valve and a joint.

[0010] Further, the heating unit is a heating wire, and the heating wire is wound on the outer wall of the piston cylinder of the piston unit.

[0011] Further, the refrigerator is a semiconductor refrigerator, and the hot side of the semiconductor refrigerator is cooled through the shell.

[0012] Further, the piston unit is fixed to the shell through the support.

[0013] Further, the support comprises at least two supporting rods, and one supporting rod is arranged on each of two opposite sides of the piston cylinder; one end of the supporting rod is fixed to the outer wall of the piston cylinder, and the other end of the supporting rod is provided with a screw hole; a hole is formed in the shell, a sleeve is fixed in the hole, one end of the sleeve penetrates through the water bag and enters the water bag, and a bolt is screwed through the sleeve and the screw hole at the end of the supporting rod.

[0014] Further, the refrigerator comprises a plurality of refrigerating plates arranged at intervals, and the sleeve is located between two refrigerating plates.

[0015] Further, the position, where the sleeve penetrates through the water bag, is sealingly fixed by sealing glue.

[0016] The novel self-source calibration type gas density relay has the advantages that:

[0017] The novel self-source calibration type gas density relay has the advantages that:

[0018] The relay of the utility model adopts the water bag, can play the heat preservation and heat insulation effect, and can meet the need of volume expansion of the pure water during solidification. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a vertical sectional structure schematic view of the density relay in the embodiment 1 of the utility model;

[0020] Figure 2 It is solid-liquid mixed state around the piston cylinder in the density relay in the embodiment 1 of the utility model;

[0021] Figure 3 It is the pressure-density relation diagram of SF6 at 0 DEG C by test and table look-up. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantage of the embodiment of the utility model more clear, the technical scheme in the embodiment of the utility model will be clearly and completely described below, obviously, the described embodiment is a part of the embodiment of the utility model, not all the embodiment. Based on the embodiment in the utility model, all other embodiments obtained by the person skilled in the art without making creative labor belong to the protection scope of the utility model.

[0023] Embodiment 1

[0024] This embodiment records a self-source calibration type gas density relay, through the structure combination of ice-water mixture constant temperature cavity and density fitting piston, the temperature compensation distortion problem caused by environmental fluctuation or aging of sensor is solved, the absolute reliable temperature reference is established, and the real simulation of gas density continuous change curve is realized. The specific structure is as shown in Figure 1 The shell 1 is welded with good metal material of heat conduction performance and is placed with a water bag 2 with certain elasticity inside, generally adopts polytetrafluoroethylene rubber bag, the water bag 2 is provided with clean water, and the clean water in the embodiment generally adopts pure water. Between the water bag 2 and the shell 1, the refrigerator 3 is fixed, generally adopting semiconductor refrigerator 3. The refrigerator 3 is in contact with the shell 1, and heat can be dissipated through the shell 1. The piston unit 4 is located in the water bag 2, and the piston drive shaft 41 passes through the water bag 2 and the shell 1 and is driven connected with the external driving motor 5. The position of the piston drive shaft 41 passing through the water bag 2 can fix the water inlet of the water bag 2 to the inner wall of the shell 1 by melting or gluing, the piston drive shaft 41 passing through the water inlet of the water bag 2 can fix the water inlet of the water bag 2 to the inner wall of the bearing hole at the top of the shell 1 by melting or gluing, and the piston drive shaft 41 passing through the bearing hole of the shell 1 can be sealed by a sealing bearing, so as to avoid the overflow or entry of pure water between the water bag 2 and the shell 1, which affects the operation of the refrigerator 3.

[0025] In this embodiment, the outer wall of the piston cylinder 42 of the piston unit 4 is fixed with a temperature sensor 43, which is glued to the bottom wall or side wall of the piston cylinder 42 and used to detect the temperature around the piston cylinder 42. The piston cylinder 42 is also provided with a gas pressure sensor 44, which is usually installed at the tail of the piston cylinder 42 and can obtain real-time internal pressure information. The piston cylinder 42 is made of aluminum shell, and the surface thereof is wound with heating wires (not shown in the figure), or the surface of the aluminum shell is slotted, and the heating wires are embedded in the slots. The tail of the piston cylinder 42 is provided with an exhaust hole, and the gas conveying pipe 45 passes through the water bag 2, the shell 1 and is connected with the external sulfur hexafluoride gas tank. The electromagnetic valve 46 and the joint 47 are installed at the position of the gas conveying pipe 45 outside the shell 1, and the joint 47 is used to connect with the sulfur hexafluoride gas tank. The position of the water bag 2 through which the gas conveying pipe 45 passes is a connecting port, which is fixed and sealed with the inner wall of the wire hole of the shell 1 by hot melting or gluing, and the wire hole is used for the wire and signal line of the gas conveying pipe 45 and other sensors, heating wires and all the wires to pass out; the wire hole is realized by a sealing rubber ring or a sealing joint 47, so as to avoid the leakage of pure water. In this embodiment, the piston cylinder 42, the heating wires, the gas pressure sensor 44 and the temperature sensor 43 are completely immersed in the pure water and are in the same environment.

[0026] The refrigeration device 3 of this embodiment is provided with refrigeration plates on the other five sides except the side through which the piston driving shaft 41 passes out, and the refrigeration plates are arranged at intervals.

[0027] In order to avoid that the piston cylinder 42 shakes and breaks the piston driving shaft 41, the piston cylinder 42 is fixed outside the shell 1 by a support in this embodiment, and specifically, as shown in Figure 1 , Figure 2 , the support is at least two support rods 6, Figure 1 four support rods 6. The plurality of support rods 6 are symmetrically arranged on both sides of the piston cylinder 42, one end of the support rod 6 is welded or bolted with the outer part of the piston cylinder 42, and the other end is provided with a screw hole. A hole is opened on the shell, and a sleeve 60 is fixed in the hole. One end of the sleeve 60 passes through the water bag 2 into the water bag, and the sleeve 60 and the screw hole at the end of the support rod 6 are screwed by the bolt 61, so that the piston cylinder is fixed in the water bag 2. The position of the sleeve 60 passing through the water bag is sealed and fixed by sealing glue. Through the design of the sleeve, a channel is provided for the bolt, and the water bag can be sealed and fixed, so as to ensure the sealing of the water bag.

[0028] The relay of the embodiment is assembled in the following way. The top cover and the bottom plate of the shell 1 are assembled after the production. The refrigerating device 3 and the water bag 2 are installed in place. The water inlet of the water bag 2 is directed to the top of the shell 1. The piston unit 4 is placed in the water bag 2 and is fixed tightly by bolts and supporting rods. The bottom of the water bag 2 and the bottom of the shell 1 are bored. The opening of the water bag 2 and the opening of the bottom cover of the shell 1 are fixed by hot melting or adhesive sealing. The electric wires and signal lines of the temperature sensor 43, the heating wire and the gas pressure sensor 44 and the gas delivery pipe 45 are passed out of the bottom hole of the water bag 2 and the shell 1. The bottom opening of the shell 1 is blocked by a sealing joint 47. The electromagnetic valve 46 and the joint 47 connected with the sulfur hexafluoride gas tank are installed on the pipe outside the shell 1. At this time, the top cover and the bottom cover of the shell 1 are welded and fixed with the four walls of the shell 1. The top cover is provided with an axle hole through which the piston driving shaft 41 is passed. The opening of the top of the water bag 2 and the peripheral wall of the axle hole are fixed by hot melting or adhesive sealing. Then, pure water is injected into the water bag 2. The pure water should completely immerse the piston cylinder 42. Finally, the bearing hole is blocked by a sealing bearing to complete the assembly. When in use, the piston driving shaft 41 needs to be connected with the driving motor 5.

[0029] The working principle of the relay of the embodiment is as follows.

[0030] (1) Establishing temperature reference

[0031] Firstly, the refrigerating device 3 is started to continuously cool the high-purity water in the sealed cavity to below -20℃ to ensure that the water body completely solidifies into solid ice. After the water body completely solidifies, the heating wire in the piston cylinder 42 is started to directionally heat the contact area of the piston unit 4 to make the ice layer around the piston cylinder 42 melt until a solid-liquid coexistence state is formed, as shown in FIG. 6. The experience value can be determined by experiment. The heating time is set after heating for a maximum time and the appropriate ice-water mixture under the same power. Figure 2

[0032] The piston unit 4 is completely immersed in the ice-water mixed medium. The whole body reaches thermodynamic equilibrium through heat conduction, thereby providing an absolute temperature reference source for gas density measurement. At this time, the indication of the temperature sensor 43 is read. If the deviation from the reference temperature 0℃ is ≤±0.1℃, it is considered to be in normal working state.

[0033] (2) P / L linear fitting

[0034] ​Calculations reveal the initial position of piston cylinder 42, typically at 1 / 2L; the position that satisfies saturated vapor pressure, typically at 1 / 4L; and the pressure reduction position, typically at 3 / 4L. L represents the length of piston cylinder 42, and 1 / 4L, 1 / 2L, and 3 / 4L are volume divisions from the tail to the top of piston cylinder 42 (the portion of the piston chamber located in the piston's forward direction is the tail). The external gas chamber is connected to piston unit 4 via an interface, driving the piston to move upwards from the bottom to the initial position to extract gas. After extraction, the microcontroller controls solenoid valve 46 to close the gas port. At this point, the piston chamber is disconnected from the external gas chamber, and the piston chamber contains a fixed amount of SF6 gas.

[0035] 1) Determine the indicated value of the saturated vapor pressure point.

[0036] The piston is initially positioned at 1 / 2L, and the initial SF6 gas pressure inside the piston chamber is 1MPa. At this point, the stepper motor 5 drives the piston to move towards the bottom of the piston chamber, compressing its volume. Since the saturated vapor pressure of SF6 at 0℃ is approximately 1.2MPa (absolute pressure), when the piston chamber begins to compress to the critical pressure of 1.2MPa, the system is in a gas-liquid coexistence state. If the volume is further compressed, the gas will continue to liquefy. However, further compression will not increase the pressure. This is because when the gas reaches its liquefaction point, i.e., enters a gas-liquid coexistence state, the pressure remains at the level of the saturated vapor pressure. The saturated vapor pressure is a constant value that depends only on the type of substance and temperature, and is independent of volume. Therefore, continuing to compress the container volume will only cause more gas to liquefy, while the pressure remains constant until all the gas is completely liquefied, at which point the pressure will rise again.

[0037] Since the piston chamber is immersed in an ice-water mixture at 0°C, after a period of time, the gas temperature inside the piston chamber will be the same as the ambient liquid temperature, i.e., the gas temperature T0 is also 0°C. Therefore, when the piston moves to the initial preset position of 1 / 4L, the SF6 in piston chamber A will inevitably begin to liquefy. Because the pressure of SF6 gas in a gas-liquid coexistence state will be maintained at the level of saturated vapor pressure, according to tables (IEC 60376, IEEE standards), the saturated vapor pressure of SF6 gas at 0°C is 1.2 MPa, let P be the pressure. a At this point, by comparing the reading P of the gas pressure sensor 44 on piston chamber A, if PP a When the pressure is ≤±0.005MPa, the pressure test value of gas pressure sensor 44 at that point can be considered accurate.

[0038] 2) The pressure-density relationship of SF6 at 0℃ was plotted through experiments and table references, such as... Figure 3 As shown, this diagram can be built into the microcontroller of the relay and can be directly called for calculation.

[0039] When the piston moves to 1 / 2L, the reading P1 of the gas pressure sensor 44 is recorded, and the reading is determined based on the data from the microcontroller built into the device. Figure 3 The curve automatically calculates the corresponding gas density. At this point, when the control motor 5 drives the piston to move to 3 / 4L, the reading P2 of the gas pressure sensor 44 is recorded, and the reading is determined according to the data stored in the microcontroller of the device. Figure 3 The curve automatically calculates the corresponding gas density. Since the temperature and the total amount of gas remain constant, the gas density at this location can be calculated using the density equation (1). ,like If the value is ≤±1%, it means that the value at that point is accurate.

[0040]

[0041] In the formula: m —Gas mass (kg); V —Gas volume (m³); T —Absolute temperature (K).

[0042] Therefore, the multi-point readings of the gas pressure sensor 44 can be verified using the above method based on the built-in SF6 pressure-density relationship curve, thus truly completing the multi-point self-calibration of the gas pressure sensor 44.

[0043] (3) Alarm value / lockout value self-check

[0044] ①Cavity connection and reset:

[0045] Open solenoid valve 46 to release the gas inside the piston to the outside, thereby reducing the pressure of the gas inside the piston chamber. After the pressure reduction is complete, close solenoid valve 46. Record the gas pressure inside the piston chamber as P0 and the piston position as L0 at this time.

[0046] ②Alarm point simulation and recording:

[0047] When the working air pressure drops to the alarm value, the density relay will trigger an alarm.

[0048] By controlling the stepper motor 5 to drive the piston to move in the same direction (increasing the piston chamber volume), the gas density value is calculated in real time based on the reading of the gas pressure sensor 44. If the reading drops to the alarm pressure value, observe whether the density relay triggers the relevant action.

[0049] ③ Locking point simulation and recording:

[0050] When the working gas pressure drops to the lockout value, the density relay will trigger the lockout action.

[0051] By controlling the stepping motor 5 to drive the piston to move in the same direction (to increase the piston cavity volume), the gas density value is calculated in real time according to the value shown by the gas pressure sensor 44, and if the value decreases to the locking pressure value, whether the density relay triggers the related action is observed.

[0052] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some technical features can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A self-calibrated gas density relay, comprising a piston unit (4), characterized in that, It also includes a temperature control chamber and a heating unit. The temperature control chamber is filled with clean water. The piston unit (4) is equipped with a pressure sensor (44) and a temperature sensor (43). The piston cylinder (42), pressure sensor (44), and temperature sensor (43) of the piston unit (4) are all located in the clean water, and the piston shaft extends out of the temperature control chamber. The piston chamber of the piston unit (4) is connected to the outside through a gas supply pipe (45). A valve is installed on the gas supply pipe (45). The heating unit acts on the piston cylinder (42).

2. The self-calibrated gas density relay according to claim 1, characterized in that, The temperature control chamber includes a closed shell (1), clean water is filled inside the shell (1), and a cooler (3) is fixed inside the shell (1); the piston unit (4) is fixed inside the shell (1) and immersed in clean water, the piston unit (4) includes a piston drive shaft (41), the piston drive shaft (41) extends out of the shell (1) and is connected to the drive unit.

3. The self-calibrated gas density relay according to claim 2, characterized in that, The temperature control chamber also includes a water bag (2); the water bag (2) is located inside the shell (1), and clean water is located inside the water bag (2); the cooler (3) is located between the water bag (2) and the shell (1).

4. The self-calibrated gas density relay according to any one of claims 2 or 3, characterized in that, The piston unit (4) has a piston chamber located at the tail end in the piston's forward direction. The tail end has an exhaust port. One end of the gas supply pipe (45) is sealed to the exhaust port, and the other end extends out of the housing (1) and is sequentially equipped with a solenoid valve (46) and a connector (47).

5. The self-calibrated gas density relay according to any one of claims 1 to 3, characterized in that, The heating unit is a heating wire, which is wound around the outer wall of the piston cylinder (42) of the piston unit (4).

6. The self-calibrated gas density relay according to any one of claims 2 or 3, characterized in that, The cooler (3) is a semiconductor cooler (3), and its hot side dissipates heat through the housing (1).

7. The self-calibrated gas density relay according to claim 6, characterized in that, It also includes a bracket, through which the piston unit (4) is fixed to the housing (1).

8. The self-calibrated gas density relay according to claim 7, characterized in that, The support includes at least two support rods (6), with at least one support rod (6) on each of the two opposite sides of the piston cylinder (42) of the piston unit (4); one end of the support rod (6) is fixed to the outer wall of the piston cylinder (42), and the other end has a screw hole; a hole is opened on the housing (1), and a sleeve (60) is fixed in the hole. One end of the sleeve (60) passes through the water bag (2) and enters the water bag. A bolt (61) passes through the sleeve (60) and threadedly engages with the screw hole at the end of the support rod (6).

9. The self-calibrated gas density relay according to claim 8, characterized in that, The refrigerator (3) includes multiple spaced-apart cooling plates, and the sleeve (60) is located between two cooling plates.

10. The self-calibrated gas density relay according to claim 8, characterized in that, The sleeve (60) is sealed and fixed at the position where it passes through the water bag with sealant.

Images