Vacuum leak detector and vacuum device

Abstract

To provide a detector capable of detecting vacuum leaks at low cost.SOLUTION: A vacuum leak detector (10) is provided, comprising an alkali metal body (12) disposed inside a vacuum vessel (20) that designed to generate heat from reaction with the insulating gas (30) contained in the atmosphere outside the vacuum vessel, and a temperature measurement device (11) capable of measuring temperature of the alkali metal body.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to vacuum leak detectors and vacuum devices. [Background technology]

[0002] Patent Document 1 discloses a method for detecting vacuum leaks in a vacuum interrupter placed in SF6 gas. This method involves adjusting the contacts of the vacuum interrupter to a predetermined gap length and checking the withstand voltage of the contacts. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-86696 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the method disclosed in Patent Document 1 requires contacts with an adjustable gap length and a high-voltage power supply, which increases the cost required for detecting vacuum leaks.

[0005] The present disclosure aims to provide a detector or the like that can detect vacuum leaks at low cost. [Means for solving the problem]

[0006] In order to solve the above problem, a vacuum leak detector according to one embodiment of the present disclosure comprises an alkali metal body arranged inside a vacuum vessel and generating heat by reacting with gas contained in the atmosphere outside the vacuum vessel, and a temperature measuring device capable of measuring the temperature of the alkali metal body. [Effects of the Invention]

[0007] According to one aspect of the present disclosure, a detector or the like capable of detecting vacuum leaks can be realized at low cost. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of a vacuum circuit breaker equipped with a vacuum leak detector according to a first embodiment of the present disclosure. [Figure 2] FIG. 10 is a schematic diagram of a vacuum circuit breaker including a vacuum leak detector according to a second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Embodiment 1] An embodiment of the present disclosure will be described in detail below. In the following description, a vacuum circuit breaker will be described as a device installed in high-voltage power equipment. However, the vacuum leak detector and vacuum device of the present disclosure can also be applied to other power equipment such as substation equipment.

[0010] 1 is a schematic diagram of a vacuum circuit breaker 1 including a vacuum leak detector 10 according to an embodiment of the present disclosure. The vacuum circuit breaker 1 is a device that interrupts a high-voltage electrical circuit by utilizing the dielectric strength and arc-extinguishing ability of a vacuum. The vacuum circuit breaker 1 includes the vacuum leak detector 10, a vacuum vessel 20, and a vessel 40.

[0011] The container 40 is a container that forms the exterior of the vacuum circuit breaker 1, and houses the vacuum leak detector 10 and the vacuum container 20 inside. Although not shown, the container 40 also houses other items that are generally provided in vacuum circuit breakers, such as electrical circuits. The container 40 is filled with insulating gas 30.

[0012] The vacuum vessel 20 is a vessel whose interior is maintained in a vacuum state. Although not shown, two conductive contacts are inserted from the outside into the vacuum vessel 20, and an electric circuit can be formed by bringing the contacts into contact with each other inside the vacuum vessel 20. Because the inside of the vacuum vessel 20 is in a vacuum state, an arc that occurs between the contacts when the electric circuit is interrupted can be quickly extinguished.

[0013] The insulating gas 30 is a gas having insulating properties. The insulating gas 30 fills the periphery of the vacuum vessel 20 inside the vacuum circuit breaker 1. In other words, the vacuum vessel 20 is placed under an atmosphere of the insulating gas 30. The insulating gas 30 may be, for example, sulfur hexafluoride gas (SF6), but is not limited to this.

[0014] The vacuum leak detector 10 detects leakage of the insulating gas 30 into the vacuum vessel 20. The vacuum leak detector 10 includes a temperature measuring device 11 and an alkali metal body 12.

[0015] The alkali metal body 12 is disposed inside the vacuum vessel 20. The alkali metal body 12 is made of an alkali metal and is selected to chemically react with the gas contained in the insulating gas 30. Therefore, if the insulating gas 30 leaks into the vacuum vessel 20, the alkali metal body 12 will generate heat by reacting with the insulating gas 30 leaking from outside the vacuum vessel 20.

[0016] The temperature measuring device 11 is capable of measuring the temperature of the alkali metal body 12. The temperature measuring device 11 is arranged outside the vacuum vessel 20 and connected to the alkali metal body 12 via a cord or the like. The cord or the like is airtightly inserted through the vacuum vessel 20. Note that the temperature measuring device 11 does not necessarily have to be arranged outside the vacuum vessel 20, and may be arranged inside the vacuum vessel 20 or outside the vacuum circuit breaker 1.

[0017] According to the above configuration, when a vacuum leak occurs in the vacuum vessel 20 placed under an insulating gas 30 atmosphere in the electric power equipment, the insulating gas 30 flows into the vacuum vessel 20, causing the alkali metal body 12 to react with the insulating gas 30 and generate heat. The temperature measuring device 11 detects the generated temperature, thereby making it possible to detect the occurrence of a vacuum leak in the electric power equipment.

[0018] The temperature measuring device 11 may be a thermocouple. The temperature measuring device 11 is connected to the alkali metal body 12 via a bush or the like provided in the vacuum vessel 20. This allows the thermocouple, which is the temperature measuring device 11, to measure the temperature of the alkali metal body 12 and detect a vacuum leak. However, as in another embodiment described later, the temperature measuring device 11 is not limited to a thermocouple.

[0019] The alkali metal body 12 may be formed of lithium (Li). When SF6 is used as the insulating gas 30, Li and SF6 undergo a chemical reaction shown in chemical reaction formula (1). 8Li+SF6→6LiF+Li2S (1)

[0020] In addition, the enthalpy change from before to after the reaction is -1265.67 kJ / mol per 1 mol of SF6 gas, so 1265.67 kJ of heat of formation is generated per 1 mol of SF6 gas. Therefore, if we rewrite chemical reaction equation (1) as thermochemical reaction equation (2), we get the following: 8Li+SF6=6LiF+Li2S+1265.67[kJ]...(2)

[0021] As described above, Li reacts with SF6, which is widely used as an insulating gas in power equipment, causing a temperature rise. Therefore, the vacuum leak detector 10 can detect vacuum leaks in power equipment that uses SF6 as an insulating gas.

[0022] In the above description, the vacuum leak detector 10 is exemplified as a device provided in the vacuum circuit breaker 1. However, the vacuum leak detector 10 can be applied to any power equipment that has a vacuum container, and can also be applied to, for example, transformers and vacuum valves.

[0023] Furthermore, the type of alkali metal forming the alkali metal body 12 may be changed depending on the type of insulating gas 30. For example, when the insulating gas 30 is dry air, the alkali metal body 12 may be formed of an alkali metal other than Li that reacts with oxygen in the dry air. In this case, if a vacuum leak occurs in the vacuum vessel 20 and dry air flows into the vacuum vessel 20, the alkali metal body 12 reacts with oxygen and the temperature rises. The temperature measuring device 11 detects this increased temperature, thereby making it possible to detect the occurrence of a vacuum leak.

[0024] Furthermore, although the vacuum leak detector 10 can be applied to electric power equipment as described above, the vacuum leak detector 10 can also be used in other devices as long as the alkali metal body 12 generates heat by reacting with gas contained in the atmosphere outside the vacuum vessel 20. For example, if the vacuum vessel 20 is used in the atmosphere, the alkali metal body 12 may be formed of an alkali metal other than Li that reacts with oxygen in the atmosphere.

[0025] [Alkali metal body 12] The following is an example of a selection method for selecting the size of the alkali metal body 12 suitable for the temperature measuring device 11 to detect a temperature rise. The alkali metal body 12 is Li, the inside of the vacuum vessel 20 is a cubic space with a side length of 0.2 m (volume V = 8 L), and the temperature T of SF6 outside the vacuum vessel 20 is 293 K (20°C). At this time, a vacuum leak occurs in the vacuum vessel 20, and the pressure P inside the vacuum vessel 20 rises to 1.0 × 10 -2 Consider the case where the SF6 atmosphere is [Pa].

[0026] By rearranging the equation of state for an ideal gas, the following equation (3) is derived.

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[0027] By multiplying both sides by the molecular weight M, the mass density ρ is calculated using the following equation (4).

number

[0028] Since the volume of the vacuum vessel 20 is 8 L, the mass m of the SF6 molecule in the vacuum vessel 20 is expressed by the following equation (5).

number

[0029] In equation (5), the molecular weight of SF6, M = 146.06 [g / mol], and the internal pressure, P = 1.0 × 10 -2 [Pa], gas constant R = 8.31 × 10 3 By substituting [Pa·L / K·mol] and temperature T=293[K], m=4.799×10 -6 It becomes [g].

[0030] Dividing the mass m by the molecular weight M of SF6 = 146.06 [g / mol], the amount of SF6 present in the vacuum vessel 20 is n = 3.286 × 10 -8 It becomes [mol].

[0031] The calorific value Q is calculated assuming that all of the SF6 present in the vacuum circuit breaker 1 flows into the vacuum vessel 20 and reacts with the alkali metal body 12. As shown in thermochemical reaction formula (2), the heat of formation per 1 mol of SF6 is 1265.67 kJ, so Q = 0.0416 J.

[0032] The specific heat c of Li is 3.59 [J / g·K], the temperature increment is △T, and the mass of the alkali metal body 12 is m Li Then, the amount of heat generated Q is expressed by the following formula (6) using the specific heat formula.

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[0033] From equation (6), the mass m of the alkali metal body 12 required when the temperature increment of the alkali metal body 12 is 10 [K] is Li is derived as shown in the following equation (7).

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[0034] For example, the volume of a lithium foil with a thickness of 0.002 cm, a width of 1 cm, and a length of 1 cm is 0.002 cm 3 ] and the specific gravity of Li is 0.53 [g / cm 3 ] to the mass of the lithium foil m Li is 1.06 x 10 -3 That is, by placing the lithium foil having the above dimensions in the vacuum vessel 20 as the alkali metal body 12, the amount of lithium in the vacuum vessel 20 is 1×10 -2 When all of the SF6 reacts with the lithium foil, a temperature rise of about 10[K] is obtained. A temperature rise of 10[K] is detectable by many commonly used thermocouples. Therefore, heat generation in the lithium foil can be detected with a general thermocouple, and vacuum leaks can be detected.

[0035] The mass and volume of the alkali metal body 12 are determined based on many variables, such as the heat of reaction generated by the reaction between the alkali metal body 12 and the gas contained in the insulating gas 30, the volume of the vacuum vessel 20, and the temperature increment ΔT detected by the temperature measuring device 11. Therefore, the above values ​​are merely an example of a selection method.

[0036] [Embodiment 2] Another embodiment of the present disclosure will be described below with reference to Fig. 2. For ease of explanation, members having the same functions as those described in the first embodiment will be denoted by the same reference numerals, and their description will not be repeated.

[0037] 2 is a schematic diagram of a vacuum circuit breaker 1A including a vacuum leak detector 10A according to another embodiment of the present disclosure. Vacuum circuit breaker 1A differs from vacuum circuit breaker 1 in that vacuum leak detector 10A and vacuum vessel 20A are included instead of vacuum leak detector 10 and vacuum vessel 20.

[0038] Vacuum vessel 20A differs from vacuum vessel 20 in that it is provided with a viewport 21A on the side surface. Because viewport 21A is transparent, the interior of vacuum vessel 20A can be seen through viewport 21A. Viewport 21A only needs to be transparent to infrared light of the measurement wavelength, and may be made of, for example, tempered glass.

[0039] Vacuum leak detector 10A differs from vacuum leak detector 10 in that it includes temperature measuring device 11A instead of temperature measuring device 11. Temperature measuring device 11A is a radiation thermometer or a thermograph. Alkali metal body 12 is disposed inside vacuum vessel 20 at a position visible from viewport 21A. Therefore, the temperature of alkali metal body 12 can be measured from viewport 21A by temperature measuring device 11A, which is a radiation thermometer or a thermograph.

[0040] Vacuum leak detector 10A also provides the same effects as vacuum leak detector 10. Furthermore, vacuum leak detector 10A eliminates the need to provide a bushing in vacuum vessel 20, allowing the configuration of vacuum vessel 20A to be simplified.

[0041] 〔summary〕 The present disclosure can also be expressed as follows:

[0042] A vacuum leak detector according to aspect 1 of the present disclosure includes an alkali metal body disposed inside a vacuum vessel that generates heat by reacting with gas contained in the atmosphere outside the vacuum vessel, and a temperature measuring device capable of measuring the temperature of the alkali metal body.

[0043] A vacuum leak detector according to a second aspect of the present disclosure is the same as the first aspect, wherein the vacuum vessel is placed under an insulating gas atmosphere in a power facility, and the alkali metal body generates heat by reacting with the insulating gas.

[0044] A vacuum leak detector according to a third aspect of the present disclosure is the same as that of the first or second aspect, wherein the alkali metal body is formed of Li.

[0045] A vacuum leak detector according to a fourth aspect of the present disclosure is the same as any one of the first to third aspects, wherein the temperature measuring device is a thermocouple.

[0046] A vacuum leak detector according to a fifth aspect of the present disclosure is the same as that of any one of the first to third aspects, wherein the temperature measuring device is a radiation thermometer or a thermograph.

[0047] A vacuum device according to a sixth aspect of the present disclosure includes the vacuum leak detector of any one of the first to fifth aspects.

[0048] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. [Explanation of symbols]

[0049] 1, 1A vacuum circuit breaker 10, 10A Vacuum Leak Detector 11, 11A temperature measuring device 12, 12A Alkali metal body 20, 20A vacuum vessel 21A Viewport 30 Insulating gas

Claims

1. an alkali metal body disposed inside the vacuum vessel and generating heat by reacting with gas contained in the atmosphere outside the vacuum vessel; a temperature measuring device capable of measuring the temperature of the alkali metal body.

2. The vacuum vessel is placed under an insulating gas atmosphere in an electric power facility, 2. The vacuum leak detector of claim 1, wherein said alkali metal body generates heat upon reaction with said insulating gas.

3. 2. The vacuum leak detector of claim 1, wherein the alkali metal body is formed of Li.

4. 10. The vacuum leak detector of claim 1, wherein the temperature measuring device is a thermocouple.

5. The vacuum leak detector of claim 1 , wherein the temperature measuring device is a radiation thermometer or a thermograph.

6. A vacuum system comprising a vacuum leak detector according to any one of claims 1 to 5.

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