Gas pressure monitoring device for gas-insulated switchgear, gas pressure monitoring method, and gas leak location identification method

Abstract

To provide a low-cost gas pressure monitoring device for a gas insulated switchgear and a gas pressure monitoring method therefor.SOLUTION: A gas pressure monitoring device comprises: at least two cylindrical containers 21 and 23 constituting a gas insulated switchgear and having flanges receiving inner pressures; and a bolt 11b with a sensor in which at least one of sensors 1, 2 is mounted at an inner diameter side and an outer diameter side of the cylindrical container in an axial direction of at least one bolt in a plurality of bolts fastening flanges 21a and 23a of the two cylindrical containers with each other. The gas pressure monitoring device is installed in the cylindrical container, estimates a pressure change in the cylindrical container from a stress change which occurs in the bolt with the sensor after operation start of the gas insulated switchgear, and monitors a pressure of an insulation gas.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a gas pressure monitoring device and a gas pressure monitoring method for a gas-insulated switchgear, and a method for specifying the location of a gas leak, and in particular to a gas pressure monitoring device and a gas pressure monitoring method for a gas-insulated switchgear suitable for detecting gas pressure by observing changes in the pressure of insulating gas sealed in a cylindrical container such as a gas-insulated switchgear, and a method for specifying the location of a gas leak in a gas-insulated switchgear suitable for specifying the location of a gas leak from a flange of a cylindrical container. [Background technology]

[0002] Gas-insulated switchgear is a device that instantly cuts off the current and quickly turns it on to supply power in order to protect equipment such as transformers in substations when an abnormal current flows in the power grid due to a lightning strike or other cause.

[0003] This gas-insulated switchgear has a structure in which multiple gas pressure vessels that constitute gas circuit breakers, disconnecting switches, earthing switches, etc. are connected together, and the gas that is usually sealed in the gas pressure vessels is sulfur hexafluoride (hereinafter referred to as SF6).

[0004] SF6 is an inert gas and has superior arc-extinguishing properties compared to other gases, but because its global warming potential is 24,000 times that of CO2, gas leaks are subject to management.

[0005] As a conventional technique for detecting SF6 gas leakage in a gas-insulated switchgear, for example, there is a gas leak inspection method described in Patent Document 1.

[0006] The gas leak inspection method described in Patent Document 1 is composed of a pressure sensor that measures the gas pressure inside a gas pressure vessel, a temperature sensor that measures the surface temperature of the gas pressure vessel, a recording unit, etc. The gas pressure measured by the pressure sensor is converted to a value at a reference temperature of 20°C, and then linear regression is performed on the pressure measurement results. A gas leak is detected by determining whether the slope of the regression line exceeds the slope of a gas leak at a specified concentration.

[0007] Furthermore, Patent Document 2 discloses a fault location assessment device as a conventional technique for assessing the gas compartment in which a fault has occurred using a strain sensor in a gas-insulated switchgear.

[0008] The fault point assessment device described in Patent Document 2 is composed of a strain detection means, a current measurement means, a recording unit, etc., attached to the metal pipe that constitutes the gas compartment, and when the current detected by the gas-insulated switchgear exceeds a predetermined value, the gas compartment, which is the fault point, is assessed based on the signal recorded from the strain detection means.

[0009] Furthermore, a gas pressure monitoring device for gas-insulated switchgear is described in Patent Document 3 as a conventional technology in which a pressure gauge is installed in a gas circuit breaker that constitutes a gas-insulated switchgear to observe the pressure of the enclosed SF6 gas, and an attendant periodically checks the reading of the pressure gauge to determine whether or not there is a leak of SF6 gas. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-57135 [Patent Document 2] Japanese Patent Application Publication No. 2019-9948 [Patent Document 3] Japanese Patent Publication No. 2020-72614 Summary of the Invention [Problem to be solved by the invention]

[0011] However, the gas leak inspection method described in Patent Document 1 requires a gas pressure sensor to be installed for each gas compartment, and the gas is guided from inside the sealed container to an external pressure sensor through piping. This means that multiple gas seals are required to monitor one sealed container, and there is a possibility that gas may leak from these seals.

[0012] Furthermore, in the fault point assessment device described in Patent Document 2, a strain sensor is attached to the outer surface of a metallic cylindrical container that constitutes the gas-insulated switchgear, and the strain value is monitored using this strain sensor, thereby obtaining a fault point assessment device with a low risk of gas leakage. However, because the metallic cylindrical container has a certain rigidity, it is expected that the change in output of the strain sensor in response to a change in gas pressure during operation of the gas-insulated switchgear will be small.

[0013] Therefore, it is considered difficult for the fault point assessment device described in Patent Document 2 to detect gas leakage inside the cylindrical container with high accuracy.

[0014] Furthermore, with the gas pressure monitoring device for gas-insulated switchgear described in Patent Document 3, even if a sudden increase in the amount of gas leakage occurs in a gas circuit breaker that has deteriorated over time, it may not be detected by an attendant who makes patrol inspections about once a week. Also, since leakage of insulating gas from a gas circuit breaker is a phenomenon that appears after a considerable number of years have passed since installation and the circuit breaker has deteriorated, installing and operating a device that automatically monitors the gas pressure from the time the gas circuit breaker is first installed would be wasteful and could result in high maintenance costs for the monitoring device.

[0015] The present invention has been made in view of the above points, and a first object thereof is to provide a low-cost gas pressure monitoring device for gas-insulated switchgear and a gas pressure monitoring method therefor.

[0016] A second object of the present invention is to provide a method for identifying a gas leak position in a gas-insulated switchgear, which is capable of identifying the location of gas leakage from the flange of a cylindrical container. [Means for solving the problem]

[0017] In order to achieve the first object, the gas pressure monitoring device for a gas-insulated switchgear of the present invention comprises at least two cylindrical containers that constitute the gas-insulated switchgear and have flanges that are subjected to internal pressure; a plurality of bolts that fasten the flanges of the two cylindrical containers together; at least one of the plurality of bolts, a sensor-equipped bolt having at least one sensor attached to each of the inner diameter side and the outer diameter side of the cylindrical container in the axial direction of the bolt; a pressure gauge that is installed on the cylindrical container and reads the pressure of the insulating gas when the insulating gas is sealed inside the cylindrical container; a measurement recording unit that records the readings of the pressure gauge and the output value of the sensor; and an evaluation unit that calculates the relationship between the pressure of the insulating gas when the insulating gas is sealed inside the cylindrical container and the stress acting on the sensor-equipped bolt, and is characterized in that after operation of the gas-insulated switchgear starts, the pressure monitoring device estimates pressure changes inside the cylindrical container from stress changes that occur in the sensor-equipped bolt and monitors the pressure of the insulating gas.

[0018] In order to achieve the first object, the gas pressure monitoring method for a gas-insulated switchgear of the present invention is characterized in that it targets at least one bolt among a plurality of bolts that fasten together flanges of at least two cylindrical containers that constitute the gas-insulated switchgear and are subjected to internal pressure, detects the pressure of the insulating gas inside the cylindrical container while the gas-insulated switchgear is in an operating state using a sensor attached to the bolt, and estimates changes in stress acting on the bolt based on the detection value from the sensor to monitor the pressure of the insulating gas.

[0019] In addition, in order to achieve the second object, the method for identifying the location of a gas leak in a gas-insulated switchgear of the present invention is characterized in that a sensor for detecting stress acting on at least one of a plurality of bolts fastening flanges of at least two cylindrical containers that constitute the gas-insulated switchgear and are subjected to internal pressure is installed on the bolt of each of the two cylindrical containers, and the stress values ​​acting on the flanges of the two cylindrical containers detected by the sensor are compared to identify the location of the gas leak from the flange. [Effects of the Invention]

[0020] According to the present invention, a simple and low-cost gas pressure monitoring device for gas-insulated switchgear can be obtained that has a low risk of gas leakage and is capable of monitoring gas pressure without changing the existing device configuration, and it is also possible to identify the location of gas leakage from the flange of the cylindrical container. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a perspective view showing an example in which two cylindrical containers are connected to each other via flanges in a configuration of a gas-insulated switchgear that is the subject of the present invention. [Figure 2] FIG. 2 is a cross-sectional perspective view taken along line AA in FIG. [Figure 3] 1 is a cross-sectional view showing a connecting portion of two cylindrical containers in a gas pressure monitoring device for gas-insulated switchgear according to a first embodiment of the present invention. [Figure 4] 1 is a cross-sectional view showing the connecting portion of two cylindrical containers in a gas pressure monitoring device for gas-insulated switchgear according to a first embodiment of the present invention, illustrating the state before insulating gas is sealed in the two cylindrical containers. [Figure 5] 1 is a cross-sectional view showing the connecting portion of two cylindrical containers in a gas pressure monitoring device for gas-insulated switchgear according to a first embodiment of the present invention, illustrating a state in which the filling of insulating gas into the two cylindrical containers has begun. [Figure 6] FIG. 2 shows the connection portion of two cylindrical containers in the gas pressure monitoring device for gas-insulated switchgear according to the first embodiment of the present invention, illustrating the state after insulating gas of a specified pressure has been sealed into the two cylindrical containers. [Figure 7] FIG. 10 is a diagram showing an example of the relationship between the pressure gauge readings recorded when insulating gas is sealed into two cylindrical containers and the output values ​​of the strain sensor in the gas pressure monitoring device for the gas-insulated switchgear according to the first embodiment of the present invention. [Figure 8] 4 is a diagram showing an example of the relationship between the gas pressure in the cylindrical container and the bolt stress in the gas pressure monitoring device for the gas-insulated switchgear according to the first embodiment of the present invention. FIG. [Figure 9] FIG. 2 is a diagram showing a flow of a gas pressure monitoring method for a gas-insulated switchgear according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] The gas pressure monitoring device for gas-insulated switchgear, the gas pressure monitoring method, and the gas leak location identifying method of the present invention will be described below based on the illustrated embodiments. Note that the same reference numerals are used for the same components throughout the drawings. [Example]

[0023] FIG. 1 shows an example of a gas-insulated switchgear configuration that is the subject of the present invention, in which two cylindrical containers are connected to each other via a flange.

[0024] As shown in Fig. 1, a typical gas-insulated switchgear 100 has a structure in which a plurality of cylindrical containers (Fig. 1 shows only a first cylindrical container 21 installed vertically and a second cylindrical container 23 extending horizontally from the first cylindrical container 21) are connected together. Conductors (not shown) are arranged inside the first and second cylindrical containers 21 and 23, and electricity is passed through these conductors from a bus bar in a substation.

[0025] 1, an insulating gas, such as SF6 gas, is sealed at a predetermined pressure in first and second metallic cylindrical containers 21 and 23. The first cylindrical container 21 is fitted with a flange 21a for connection to the second cylindrical container 23, and flanges 21b and 21c for connection to other cylindrical containers (not shown). A pressure gauge 104 that indicates the gas pressure inside the first cylindrical container 21 is installed on the flange 21c of the first cylindrical container 21.

[0026] The installation position of the pressure gauge 104 is not limited to the flange 21c of the first cylindrical container 21, but may be installed on the flange 21b of another first cylindrical container 21, or a port capable of measuring the pressure inside the first and second cylindrical containers 21 and 23 may be provided on the outer circumferential surface of the first cylindrical container 21 other than the flange, and the pressure gauge 104 may be attached to that port. That is, the gas pressure monitoring device of the gas-insulated switchgear 100 of this embodiment uses an existing pressure gauge.

[0027] Furthermore, the first and second cylindrical containers 21 and 23 are connected by a plurality of bolts via the flange 21a of the first cylindrical container 21 and the flange 23a of the second cylindrical container 23. The flange 21a of the first cylindrical container 21 and the flange 23a of the second cylindrical container 23 are generally designed to have a predetermined rigidity so as to comply with the standards of the first and second cylindrical containers 21 and 23. Therefore, if the flanges are rigid and do not deform at all even at the maximum operating pressure of the gas-insulated switchgear 100, this does not correspond to the present invention.

[0028] FIG. 2 shows a cross-sectional view along line AA of the connection portion where the first cylindrical container 21 and the second cylindrical container 23 are connected by multiple bolts via the flange 21a of the first cylindrical container 21 and the flange 23a of the second cylindrical container 23.

[0029] 2 are hollow containers having a predetermined wall thickness, and conductors (not shown) are disposed inside the first and second cylindrical containers 21 and 23. A spacer 22 is disposed between the flange 21a of the first cylindrical container 21 and the flange 23a of the second cylindrical container 23. The material of the spacer 22 may be either a metal such as an aluminum alloy or a non-metal such as an epoxy resin, but the material of the spacer 22 is not important in the present invention.

[0030] In FIG. 2, a flange 21 a of a first cylindrical container 21 , a flange 23 a of a second cylindrical container 23 , and a spacer 22 are connected by a bolt fastener consisting of a headed bolt 11 and a nut 12 .

[0031] The bolt fastener in this embodiment is a combination of a headed bolt 11 and a nut 12, but it may also be a so-called stud bolt with no head, with both ends fastened with nuts 12.

[0032] 2, the diameter of the headed bolt 11 is smaller than the thickness of the flange 21a of the first cylindrical container 21 and the flange 23a of the second cylindrical container 23, and is generally configured to have dimensions that provide a predetermined bending rigidity. Therefore, when a rigid bolt that does not deform at all even under the maximum operating pressure is used, this may be considered to be different from the present invention.

[0033] Next, the configuration of the gas pressure monitoring device of the gas-insulated switchgear 100 in this embodiment will be described with reference to Fig. 3. Fig. 3 is based on a cross-sectional view taken along line AA of the connection between the flange 21a of the first cylindrical container 21 and the flange 23a of the second cylindrical container 23 shown in Fig. 2, and shows the state in which the strain sensors 1 and 2 are attached to the headed bolt 11, and the connection state from the signal wires 101 of the strain sensors 1 and 2 to the evaluation unit 106 and the monitoring monitor 107 via the strain amplifier 102 and measurement and recording unit 103.

[0034] In FIG. 3, an O-ring groove 22c for sealing insulating gas such as SF6 gas is provided at the connection portion between the spacer 22 and the flange 21a of the first cylindrical container 21 and the flange 23a of the second cylindrical container 23, and an O-ring 24 made of a predetermined material is fitted inside this O-ring groove 22c.

[0035] In addition, strain sensors 1 and 2 are provided on the outer surface of headed bolt 11b at a position approximately midway between the end faces of flange 21a of first cylindrical container 21 and flange 23a of second cylindrical container 23 in the axial direction of headed bolt 11b.

[0036] Strain sensor 2 is provided on the inner diameter side of first and second cylindrical containers 21 and 23, and strain sensor 1 is provided on the outer diameter side. Signal wires 101 from strain sensors 1 and 2 pass through headed bolt 11b, are pulled out from bolt head 11a of headed bolt 11b to the outside, and are connected to strain amplifier 102. The strain signal amplified by strain amplifier 102 is then input to measurement and recording unit 103.

[0037] The measurement and recording unit 103 receives the signals from the strain sensors 1 and 2 and the readings from the pressure gauge 104 when SF6 gas is sealed in the first and second cylindrical containers 21 and 23. The surface temperatures 105 of the first and / or second cylindrical containers 21 and / or 23 are also input (the surface temperatures 105 of the first and / or second cylindrical containers 21 and / or 23 are detected by a temperature sensor, not shown).

[0038] Based on the results recorded by the measurement recording unit 103, the gas pressures in the first and second cylindrical vessels 21 and 23 are estimated and monitored using a gas pressure monitoring method comprising steps 1 to 6, which will be described later.

[0039] According to this embodiment, by replacing one of the multiple flange fastening bolts connecting the first and second cylindrical vessels 21 and 23 constituting the gas-insulated switchgear 100 with a bolt with a strain sensor (headed bolt 11b), the pressure inside the first and second cylindrical vessels 21 and 23 can be estimated as in steps 2 and 4 described below. Since no additional work is required to guide the pressure from the first and second cylindrical vessels 21 and 23 to the strain sensors 1 and 2, a gas pressure monitoring device can be provided for an existing gas-insulated switchgear 100 without any modification.

[0040] Next, using the flow diagram of the gas pressure monitoring device of the gas-insulated switchgear 100 of this embodiment shown in Figure 9, the details of the gas pressure monitoring method of this embodiment will be explained using Figures 4, 5, 6, 7 and 8.

[0041] [Step 1 (S1)] During periodic inspection of the gas-insulated switchgear 100 several years after installation, the SF6 gas inside the first and second cylindrical containers 21 and 23 is discharged, and at least one of the bolts connecting the flange 21a of the first cylindrical container 21 and the flange 23a of the second cylindrical container 23 is replaced with a headed bolt 11b equipped with strain sensors 1 and 2, and the bolt is tightened to the specified torque using a bolt fastener consisting of the headed bolt 11b and a nut 12.

[0042] As shown in FIG. 4, which shows the connection between the flange 21a of the first cylindrical container 21 and the flange 23a of the second cylindrical container 23 at the time when bolt tightening by the bolt fastener is completed, there is a gap g21 between the flange 21a of the first cylindrical container 21 and the spacer 22, and there is a gap g23 between the flange 23a of the second cylindrical container 23 and the spacer 22, but generally the gaps g21 and g23 are filled with caulking, grease, or the like.

[0043] Strain sensors 1 and 2 are attached to approximately the center of the headed bolt 11b in the axial direction, and are located away from gaps g21 and g23. Therefore, even if the caulking deteriorates, it is believed that outside air and direct sunlight will not come into direct contact with strain sensors 1 and 2 through gaps g21 and g23, and deterioration of strain sensors 1 and 2 can be suppressed more effectively than in the prior art, in which strain sensors are attached to the outer surfaces of the first and second cylindrical containers 21 and 23.

[0044] [Step 2 (S2)] As shown in FIG. 5, which shows the connection between the flange 21a of the first cylindrical container 21 and the flange 23a of the second cylindrical container 23 at the time when the injection of SF6 gas or the like into the first and second cylindrical containers 21 and 23 is started, a pressure P initial is at work.

[0045] At this time, the SF6 gas acts on the surface of the O-ring groove 22c of the spacer 22, causing the flange 21a of the first cylindrical container 21, the flange 23a of the second cylindrical container 23, and the spacer 22 to elastically deform.

[0046] During the time when gas is being sealed into the first and second cylindrical containers 21 and 23, the strain amplifier 102 and the measurement recording unit 103 are activated, and the pressure values ​​inside the first and second cylindrical containers 21 and 23 during gas sealing and the output values ​​of the strain sensors 1 and 2 are recorded in the measurement recording unit 103.

[0047] A predetermined pressure P is applied to the first and second cylindrical containers 21 and 23. constant As shown in FIG. 6, which shows the connection between the flange 21a of the first cylindrical container 21 and the flange 23a of the second cylindrical container 23 when SF6 gas or the like is sealed in up to 1000 MPa, the flange 21a of the first cylindrical container 21 and the flange 23a of the second cylindrical container 23 are bent and deformed by the gas pressure, and as a result, the headed bolt 11b is also bent and deformed.

[0048] Figure 7 shows a graph 300 which is an example of the relationship between the pressure reading of the pressure gauge 104 when SF6 gas is sealed into the first and second cylindrical containers 21 and 23 and the output value 301 of strain sensor 1 and the output value 302 of strain sensor 2.

[0049] In Figure 7, output value 301 of strain sensor 1 indicates the measurement value of strain sensor 1 on the outer diameter side of the first and second cylindrical containers 21 and 23, and output value 302 of strain sensor 2 indicates the measurement value of strain sensor 2 on the inner diameter side of the first and second cylindrical containers 21 and 23.

[0050] The vertical axis of graph 300 in Figure 7 is the output voltage of a sensor (not shown). Before SF6 gas was injected, the strain amplifier 102 took the zero point of strain. As the gas pressure increased, the output value 302 of strain sensor 2 on the inner diameter side became larger than the output value 301 of strain sensor 1 on the outer diameter side. Therefore, the evaluation unit 106 calculates the stress acting on the headed bolt 11b from the output values ​​301 and 302 of the two strain sensors 1 and 2 using equation (1).

[0051] σ T =E×1 / 2×(ε 301 +ε 302 ) (1) where σ T is the tensile component of the stress acting on the headed bolt 11b, E is the longitudinal elastic modulus of the material of the headed bolt 11b, ε 301 ,ε 302are the strain values ​​at the strain sensors 1 and 2. The relationship between the stress acting on the headed bolt 11b calculated from equation (1) and the pressure values ​​inside the first and second cylindrical containers 21 and 23 is shown in graph 303 of FIG.

[0052] [Step 3 (S3)] When the filling of the first and second cylindrical containers 21 and 23 with gas such as SF6 gas is completed, the gas pressure is monitored in the following steps.

[0053] [Step 4 (S4)] That is, when the gas-insulated switchgear 100 is in operation, the output values ​​301 and 302 of the strain sensors 1 and 2 and the surface temperature 105 of the first and second cylindrical containers 21 and 23 are acquired at predetermined time intervals and recorded by the measurement and recording unit 103, and the bolt stress value is calculated by the evaluation unit 106 based on the above-mentioned formula (1). Then, the relationship between the stress acting on the headed bolt 11b shown in FIG. 8 and the pressure values ​​inside the first and second cylindrical containers 21 and 23 is calculated from the graph 303 in FIG. 8 as the bolt stress value σ measure to pressure value P estimaiton The relationship between these two is found from the curve in Figure 8.

[0054] The pressure value is converted to a pressure equivalent at 20°C using the equation of state for real gas. As a change in pressure value, the decrease ΔP from the specified gas pressure is calculated as shown in graph 303 of Fig. 8, which shows the relationship between the stress acting on the headed bolt 11b and the pressure value inside the first and second cylindrical containers 21 and 23.

[0055] [Step 5 (S5)] If the gas pressure in the gas-insulated switchgear 100 drops, the current interruption performance of the gas circuit breaker may drop, possibly resulting in an inability to interrupt. Therefore, in step 5 (S5), the evaluation unit 106 described above evaluates whether or not the 20°C converted pressure ΔP has reached a predetermined threshold value, and if the 20°C converted pressure ΔP has reached the predetermined threshold value, a pressure drop alarm is displayed on the monitoring monitor 107 or the like, as in step 6 (S6). If the evaluation unit 106 determines that the 20°C converted pressure ΔP has not reached the predetermined threshold value, the process returns to step 4 (S4) and the evaluation is performed again.

[0056] According to the gas pressure monitoring method of this embodiment, at least one bolt (headed bolt 11b) among the multiple bolts that fasten the flanges 21a and 23a of the first and second cylindrical containers 21 and 23 that make up the gas-insulated switchgear 100 for SF6 gas or the like can be targeted, and pressure changes inside the first and second cylindrical containers 21 and 23 when the gas-insulated switchgear 100 is in an operating state can be estimated from changes in stress acting on the headed bolt 11b.Therefore, a gas pressure monitoring device with a lower risk of gas leakage can be obtained than a conventional configuration in which gas pressure is guided from a cylindrical container to a pressure sensor through piping.

[0057] Furthermore, since the strain sensors 1 and 2 are provided on the headed bolt 11b, which is more susceptible to deformation than the outer surface of a conventional cylindrical container, the device can be provided as one that can be used both to detect changes in gas pressure during operation of the gas-insulated switchgear 100 and to assess the fault point in the event of an accident occurring within the gas-insulated switchgear 100.

[0058] Furthermore, it is possible to provide a low-cost gas pressure monitoring device to an existing gas circuit breaker that has deteriorated over time, without requiring additional work to install a sensor.

[0059] Therefore, according to this embodiment, for a gas-insulated switchgear 100 that has a risk of SF6 gas leakage over time, the gas pressure can be monitored by replacing the flange fastening bolts with headed bolts 11b using strain sensors 1 and 2 without changing the existing device configuration, thereby providing a simple and low-cost gas pressure monitoring device. [Example]

[0060] A second embodiment of the gas pressure monitoring device for gas-insulated switchgear according to the present invention will be described below.

[0061] In Example 2, which is not specifically illustrated or described, the stress acting on the flange fastening bolts is calculated by dividing it into a tensile component and a bending component, and the pressure change inside the first and second cylindrical containers 21 and 23 is estimated from the change in these two stress components.

[0062] That is, the evaluation unit 106 calculates the classification of the stress acting on the headed bolt 11b from the output values ​​301 and 302 of the two strain sensors 1 and 2 using the above-mentioned formula (1) and the following formula (2).

[0063] σ B =E×1 / 2×(ε 301 -ε 302 ) (2) where σ B is the bending component of the stress acting on the headed bolt 11b.

[0064] In FIG. 8, although not shown, the tensile component σ of the stress acting on the headed bolt 11b T Similarly, as the pressure of the gas increases, the bending component σ of the headed bolt 11b B also increases.

[0065] Therefore, in step 2 (S2) of the flow of the gas pressure monitoring method in FIG. 9, the stress increase due to the gas pressure increase is σ T <σ B And, σ T If is small, the gas pressure monitoring in step 3 (S3) is performed with σB.

[0066] In this embodiment, by attaching two strain sensors 1 and 2 to the flange fastening bolt, it is possible to accurately grasp changes in gas pressure inside the first and second cylindrical containers 21 and 23 even if the magnitude relationship between the tensile and bending components of the stress acting on the headed bolt 11b changes.

[0067] One example of a case in which the stress acting on the headed bolt 11b may decrease is when the strain sensors 1 and 2 themselves are damaged or the wiring is broken. However, even in such a case, by using two strain sensors 1 and 2, if the output of one of the strain sensors changes significantly, it is possible to diagnose an abnormality in the sensor itself. [Example]

[0068] A method for identifying a gas leak location in a gas-insulated switchgear will be described below as a third embodiment of the present invention.

[0069] In this embodiment, headed bolts 11b equipped with strain sensors 1 and 2 are incorporated into the flanges 21a and 23a of the first and second cylindrical containers 21 and 23 that constitute the gas-insulated switchgear 100, which has deteriorated over time, to identify the locations of minute gas leaks from the flanges 21a and 23a of the first and second cylindrical containers 21 and 23.

[0070] In other words, since it is believed that the flange where a gas leak is occurring will show signs of a decrease in bolt stress more quickly, by comparing the stress values ​​acting on the flanges 21a and 23a of the first and second cylindrical containers 21 and 23 detected by the strain sensors 1 and 2, it is possible to identify the location of minute gas leaks in the flanges 21a and 23a while the gas-insulated switchgear 100 is in operation.

[0071] The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0072] 1, 2...strain sensor, 11, 11b...headed bolt, 11a...bolt head, 12...nut, 21...first cylindrical container, 21a, 21b, 21c...flange of first cylindrical container, 22...spacer, 22c...O-ring groove, 23...second cylindrical container, 23a...flange of second cylindrical container, 24...O-ring, 100...gas-insulated switchgear, 101...signal line from strain sensor, 102...strain amplifier, 103...measurement recording unit, 104...pressure gauge, 105...surface temperature of cylindrical container, 106...evaluation unit, 107...monitoring monitor, 301, 302...output value of strain sensor, g21, g23...gap.

Claims

1. A gas pressure monitoring method for a gas-insulated switchgear, comprising the steps of: detecting, with a sensor attached to at least one bolt among a plurality of bolts fastening flanges of at least two cylindrical containers that constitute a gas-insulated switchgear and are subjected to internal pressure, the pressure of the insulating gas inside the cylindrical container while the gas-insulated switchgear is in an operating state; and estimating changes in stress acting on the bolt based on the detected value by the sensor, thereby monitoring the pressure of the insulating gas.

2. a measurement and recording unit that records readings from a pressure gauge and output values ​​from the sensor when an insulating gas is sealed inside the cylindrical container, and an evaluation unit that calculates a relationship between the pressure of the insulating gas when the insulating gas is sealed inside the cylindrical container and a stress acting on the sensor-equipped bolt; and a gas pressure monitoring method for a gas-insulated switchgear, comprising: a gas insulated switchgear that fastens flanges of at least two cylindrical containers that are subjected to internal pressure; a sensor-equipped bolt having at least one sensor attached to each of the inner diameter side and the outer diameter side of the cylindrical container in the axial direction of the bolt; a pressure gauge that is installed on the cylindrical container and an output value from the sensor when an insulating gas is sealed inside the cylindrical container are recorded; an evaluation unit that calculates a relationship between the pressure of the insulating gas when the insulating gas is sealed inside the cylindrical container and a stress acting on the sensor-equipped bolt; and a gas pressure monitoring method for a gas-insulated switchgear that monitors the pressure of the insulating gas by estimating changes in pressure inside the cylindrical container from changes in stress occurring in the sensor-equipped bolt after operation of the gas-insulated switchgear has started.

3. 3. A gas pressure monitoring method for a gas-insulated switchgear according to claim 2, comprising:

10. A gas pressure monitoring method for gas-insulated switchgear, wherein the surface temperature of the cylindrical container detected by a temperature sensor is recorded in the measurement and recording unit.

4. 3. A gas pressure monitoring method for a gas-insulated switchgear according to claim 2, comprising: A gas pressure monitoring method for gas-insulated switchgear, characterized in that the stress acting on the sensor-equipped bolt is calculated by dividing it into a tensile component and a bending component, and the pressure change inside the cylindrical container is estimated from the change in the two detected stress components, thereby monitoring the pressure of the insulating gas.

5. a plurality of bolts fastening the flanges of the two cylindrical containers together; a sensor-equipped bolt, which is at least one of the plurality of bolts and has at least one sensor attached to each of the inner diameter side and the outer diameter side of the cylindrical container in the axial direction of the bolt; a pressure gauge, which is installed on the cylindrical container and reads the pressure of the insulating gas when the insulating gas is sealed inside the cylindrical container; a measurement and recording unit which records the readings of the pressure gauge and the output value of the sensor; and an evaluation unit which calculates the relationship between the pressure of the insulating gas when the insulating gas is sealed inside the cylindrical container and the stress acting on the sensor-equipped bolt, a gas pressure monitoring device for a gas-insulated switchgear, characterized in that after operation of the gas-insulated switchgear starts, a pressure change inside the cylindrical container is estimated from a stress change occurring in the sensor-equipped bolt, and the pressure of the insulating gas is monitored.

6. 6. The gas pressure monitoring device for gas-insulated switchgear according to claim 5, a pressure monitoring device for a gas-insulated switchgear, wherein the sensor is provided on the outer peripheral surface of the sensor-equipped bolt at a position approximately midway between the end faces of the flanges of each of the two cylindrical containers in the axial direction of the sensor-equipped bolt.

7. 7. The gas pressure monitoring device for gas-insulated switchgear according to claim 6, 10. A gas pressure monitoring device for gas-insulated switchgear, wherein the measurement and recording unit records the surface temperature of the cylindrical container detected by a temperature sensor.

8. A method for locating a gas leak location in a gas-insulated switchgear, comprising: installing a sensor for detecting stress acting on at least one of a plurality of bolts fastening flanges of at least two cylindrical containers that constitute a gas-insulated switchgear and are subjected to internal pressure, the sensor being for detecting stress acting on each of the bolts of the two cylindrical containers; and comparing the stress values ​​acting on the flanges of the two cylindrical containers detected by the sensor to locate the location of the gas leak from the flange.

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