Methods, apparatus, uses, and equipment for gas density monitoring

Abstract

In order to mechanically monitor the gas density of greenhouse gases in a more climate-friendly and cost-effective way, the present invention provides a density monitoring method (10) for monitoring the gas density of a harmful gas, comprising: a) providing a closed reference space (26) with a partition (28) movably arranged between the reference space (26) and the harmful gas (10) to be monitored, b) providing a reference gas (56) having at least a half-fold lower global warming potential than the harmful gas (10) in the reference space (26) at a reference gas pressure higher than the filling pressure of the harmful gas (10), c) compensating by a spring device (32) the force acting on the partition (28) due to an increase in the reference gas pressure in the reference space (26), and d) detecting the deflection of the partition (28) to monitor the gas density. Furthermore, a gas density monitor (14), the use of the gas density monitor (14) in the method, and an electrical installation comprising the same are proposed.

Description

Technical Field

[0001] The present invention relates to a density monitoring method for monitoring the gas density (concentration) of harmful gases. The present invention further relates to a density monitor for monitoring the gas density of harmful gases. The present invention further relates to the use of a density monitor for monitoring the gas density of harmful gases. Finally, the present invention relates to an electrical equipment comprising a sealed or closed space such as a housing, a container, a tank, etc. containing an insulating gas (harmful gas) that has an adverse effect on the environment, and a density monitor for monitoring the gas density of the insulating gas.

Background Art

[0002] Regarding the technical background, the following documents are referred to.

[0003] [1] “Insulating gas density monitoring”, a pamphlet by Trafag AG, having the print symbol of “H70558a Trafag AG 11 / 2021”. [2] DE 10 2010 055 249 B4 [3] DE 10 2013 115 007 B4 [4] DE 10 2016 123 588 A1 [5] WO 2019 / 192857 A1 [6] Wikipedia “Treibhauspotential” (global warming potential), downloaded from the following on January 20, 2022: https: / / de.wikipedia.org / wiki / Treibhauspotential [7] Website of Novec Isoliergase 3M Deutschland (website of Novec insulating gas 3M Germany), downloaded from the following on January 20, 2022: https: / / www.3mdeutschland.de / 3M / de_DE / novec - de / anwendungen / isoliergas / [8] “Powering a sustainable future. 3M TM Novec TM "Insulating Gases," a 3M brochure, is available for download from January 20, 2022, at: https: / / multimedia.3m.eom / mws / media / 14086000 / novec-insulating-gases-for-power-generation.pdf [9] “SF6 ERSATZ G3 Flyer”, Brochure downloaded on January 20, 2022 from: https: / / www.gegridsolutions.com / products / brochures / sf6-ersatz_g3-flyer-ger.pdf

[10] DE 10232823 A1

[0004] A density monitor is a device, particularly a measuring device, for monitoring the gas density of a gas being monitored. As is known from references [1] to [5], density monitors are particularly used to monitor the density of gas (SF6) used as an insulator in gas-insulated high-voltage and medium-voltage equipment such as voltage switchgear, converters, pipelines, switching devices, and transformers.

[0005] For this purpose, for example, a density monitor based on the principle of electronic measurement is known from reference

[10] . This includes an electron density sensor as a transducer / detector, which has a crystal oscillator placed in the gas and supplies a frequency signal proportional to the gas density. This frequency signal is then supplied to an electronic evaluation unit.

[0006] On the other hand, density monitors based on mechanical measurement principles are well-established in the market, are highly reliable due to their mechanical measurement principles, and require little maintenance even over very long periods. In the simplest and most common case, a partition that operates through a reference space (reference volume) is connected to a measurement space (measurement volume), and changes in gas density cause the partition to move, activating a switch. For this purpose, for example, in density monitors known from references [1] to [5], a partition made of metal bellows is connected to a switch, and movement of the partition beyond a minimum distance triggers the switching process. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] German Patent No. 10 2010 055 249 Specification ([2] DE 10 2010 055 249 B4) [Patent Document 2] German Patent No. 10 2013 115 007 Specification ([3] DE 10 2013 115 007 B4) [Patent Document 3] German Patent Application No. 10 2016 123 588 Specification ([4] DE 10 2016 123 588 A1) [Patent Document 4] International Publication No. 2019 / 192857 ([5] WO 2019 / 192857 A1) [Patent Document 5] German Patent Application No. 10232823 (

[10] DE 10232823 A1) [Non-patent literature]

[0008] [Non-Patent Document 1] [1] “Insulating gas density monitoring”, Trafag AG brochure, print code “H70558a Trafag AG 11 / 2021”. [Non-Patent Document 2] [6] Wikipedia “Treibhauspotential” (Global Warming Potential), https: / / de.wikipedia.org / wiki / Treibhauspotential [Non-Patent Document 3] [7] Webseite Novec Isoliergase 3M Deutschland, https: / / www.3mdeutschland.de / 3M / de_DE / novec- de / anwendungen / isoliergas / [Non-Patent Document 4] [8] “Powering a sustainable future. 3MTM NovecTM Insulating Gases”, https: / / multimedia.3m.eom / mws / media / 14086000 / novec-insulating-gases-for-power-generation.pdf [Non-Patent Document 5] [9] “sf6 ersatz g3 Flyer”, https: / / www.gegridsolutions.com / products / brochures / sf6-ersatz_g3-flyer-ger.pdf [Overview of the project] [Problems that the invention aims to solve]

[0009] The objective of this invention is to make density monitoring more environmentally friendly by using a mechanical measurement principle that utilizes a reference space (volume). [Means for solving the problem]

[0010] To solve this problem, the present invention provides a density monitoring method according to claim 1, and a density monitoring apparatus, method of use, and electrical equipment according to the dependent claims.

[0011] A favorable embodiment is the subject of the subclaim.

[0012] According to its first aspect, the present invention provides a density monitoring method for monitoring the gas density of a harmful gas, including the following. That is, a) providing a closed reference space with a partition arranged between the reference space and the harmful gas to be monitored, b) providing a reference gas having a global warming potential at least as low as one-half that of the harmful gas, within a reference volume, at a reference gas pressure increased compared to the harmful gas pressure for the harmful gas, c) compensating, by means of a spring device, for the force acting on the partition due to the increase in the reference gas pressure within the reference space, and d) detecting the displacement movement of the partition to monitor the gas density.

[0013] According to a further aspect, the present invention provides a density monitor for monitoring the gas density of a harmful gas, including the following. That is, a measurement space (volume), a connection part for connecting the measurement space (volume) to a room where a harmful gas is present, a closed reference space (volume) filled with a reference gas different from the harmful gas to be monitored (global warming potential GWP < 100. Here, GWP indicates the value in terms of CO2 equivalent based on 100 years in accordance with IPCC AR5.), in which, during the intended operation of the density monitor, the reference gas is filled at an excessive pressure compared to the pressure within the measurement space, a partition separating the reference space from the measurement space, a partition displacement movement detection device for detecting the displacement movement of the partition, and spring means for elastically applying a force to the partition to compensate for the excessive pressure within the reference space.

[0014] According to a further aspect, the present invention provides the use of a density monitor as described below for monitoring the gas density of a harmful gas. That is, the density monitor has a measurement space, A connection part for connecting the measurement space to a space containing harmful gases, A closed, enclosed standard space, A partition wall separates the reference space and the measurement space, A bulkhead deflection detection device for detecting the deflection movement of a bulkhead, It has at least one spring device for elastically applying force to the bulkhead, Here, the reference space contains a reference gas with a global warming potential (GWP) < 100, which differs from the hazardous gases being monitored. Here, GWP represents the CO2 equivalent value over 100 years based on IPCC AR5, and the reference gas pressure is greater than the pressure of the hazardous gases in the measurement space. Here, we provide the use of a density monitor, in which the force acting on the partition wall due to an increase in the reference gas pressure within the reference space is compensated by a spring device.

[0015] In a further embodiment, the present invention provides an electrical installation comprising a room (space) filled with an insulating gas as a hazardous gas, and a density monitor connected to the room for monitoring the gas density of the hazardous gas. That is, the density monitor is: The measurement space connected to the aforementioned room, A reference space filled with a reference gas different from the hazardous gas being monitored, wherein the global warming potential (GWP) of this reference gas is GWP < 100, where GWP is the CO2 equivalent value over 100 years based on IPCC AR5, and the reference space has an excessive pressure compared to the pressure of the hazardous gas spreading within the room. A partition wall separates the reference space and the measurement space, A bulkhead deflection detection device for detecting the deflection movement of a bulkhead, The system comprises at least one spring device that elastically applies force to a bulkhead to compensate for excessive pressure within the spring reference space.

[0016] Preferred embodiments of at least one aspect of the present invention include: b1) A gas with GWP < 100, preferably GWP < 20, and particularly preferably GWP > 2 is provided as a reference gas in the reference space. Here, GWP represents the CO2 equivalent over 100 years according to IPCC AR5.

[0017] Preferred embodiments of at least one aspect of the present invention include: b2) Provide a gas from a group including air, N2, O2, noble gases, Ar, Kr, He, CO2, and mixtures of the aforementioned gases, or mixtures of the aforementioned gases with other gases, as a reference gas in the reference space.

[0018] Preferred embodiments of at least one aspect of the present invention include: Within the reference space, the reference gas is provided at a reference gas pressure 2.5 to 45 percent higher than the harmful gas pressure.

[0019] Preferred embodiments of at least one aspect of the present invention include: c1) To compensate for the force caused by the increase in the reference gas pressure, a first spring force of a spring device is applied to the bulkhead acting in the direction toward the reference space.

[0020] For example, the spring device has a first spring that exerts a first spring force. Preferably, the first spring is formed as a first compression spring that acts on the harmful gas side of the partition wall and pushes toward the reference space.

[0021] Preferred embodiments of at least one aspect of the present invention include: c2) To expand the range over which gas concentrations can be monitored, a second spring force is applied to the partition wall acting in the direction of the harmful gas.

[0022] For example, the spring device has a second spring that exerts a second spring force. The second spring is preferably formed as a second compression spring acting on the partition wall from the side of the reference space.

[0023] Preferred embodiments of at least one aspect of the present invention include: The initial spring force is adjusted according to the harmful gas pressure and / or reference gas pressure. In particular, a preferred embodiment of the present invention includes selecting the spring constant of the first spring according to the harmful gas pressure and / or reference gas pressure.

[0024] Preferred embodiments of at least one aspect of the present invention include: The second spring force is adjusted according to a desired gas density value or gas density range for at least one switching point or switching range. In particular, the second embodiment includes selecting the spring constants of the first and / or second springs according to a desired gas density value or gas density range for at least one switching point or switching range.

[0025] Preferred embodiments of at least one aspect of the present invention include: Select the preload of at least one spring in the spring device according to a desired gas density value or gas density range for at least one switching point or switching range.

[0026] Preferred embodiments of at least one aspect of the present invention include: The effectiveness of at least one spring in the spring device is limited to a portion of the deflection path of the bulkhead.

[0027] Preferred embodiments of at least one aspect of the present invention include: The effectiveness of the first spring is limited to a range below a predetermined gas density threshold.

[0028] According to a preferred embodiment of at least one aspect of the present invention, a metal bellows is provided for separating a reference space from a measurement space containing harmful gases, and a partition wall is formed in contact with the metal bellows.

[0029] Preferably, the reference gas is selected from the group including air, N2, O2, noble gases, Ar, Kr, He, CO2, and mixtures of the aforementioned gases or of the aforementioned gases with another gas.

[0030] In a preferred embodiment of at least one aspect of the present invention, it is assumed, or may be assumed, that a first spring acts on the partition wall in the direction toward a reference space to compensate for forces caused by excessive pressure, and that a second spring acts on the partition wall in the direction toward a harmful gas to expand the range over which the gas concentration can be monitored.

[0031] Preferably, the use of the present invention or its advantageous embodiments is useful for carrying out the method or its advantageous embodiments according to the present invention.

[0032] Preferably, a density monitor according to the present invention or a preferred embodiment is formed to carry out the method or a preferred embodiment of the present invention. Preferably, the method or a preferred embodiment of the present invention is carried out using a density monitor according to the present invention or a preferred embodiment.

[0033] Preferably, the method or an advantageous embodiment of the present invention is carried out in an electrical installation or an advantageous embodiment of the present invention.

[0034] Features or steps disclosed in one aspect of the present invention (method, apparatus, usage, equipment) or in an advantageous embodiment thereof may also be provided in one of the other aspects of the present invention or in an advantageous embodiment thereof.

[0035] An advantageous embodiment of the present invention relates to the use of density monitors, such as density monitors using low greenhouse gases, particularly green gases, i.e., climate-neutral gases, and density monitoring methods performed using them. A preferred embodiment of the present invention relates to a mechanically operated monitoring device without SF6, configured to monitor the density of SF6.

[0036] In particular, density monitors based on the reference chamber principle (mechanical measurement principle) are envisioned. Preferably, density monitors are used to monitor gas density in high-voltage switchgear (gas-insulated switchgear, outdoor switchgear, "dead tanks") to avoid damaging arcs and ensure the safety of equipment over long periods (e.g., 30 years). Temperature-compensated pressure switches are a special embodiment of density monitors. Temperature compensation is achieved, in particular, through a reference space thermally connected to the gas being monitored.

[0037] As is known from references [1] to [5], this type of density monitor or temperature-compensated pressure switch measures against a reference space. In conventionally known density monitors of this type, the reference space must be airtightly filled with the same gas being monitored as the gas being measured, at a pressure approximately the same as the equipment pressure. This means that known density monitors of this type must be filled with greenhouse gases such as SF6, which are to some extent harmful to the environment. To date, to ensure adequate temperature compensation, it is necessary to use the same insulating gas used by the equipment manufacturer. The gas chamber (equipment gas) and the reference space are separated, for example, by a metal bellows. The difference in density and pressure between the gas chambers causes a mechanical stroke in the metal bellows. This gas (SF6) is a greenhouse gas with a very high GWP (>10,000) and is subject to increasingly stringent environmental laws. See reference [6] for more information. The behavior of the gas and the function of the density monitor are specifically described in reference [1], which is referenced for more details.

[0038] In a preferred embodiment, the density monitor is a purely mechanical density monitor and typically has two to four switching points (e.g., switching point 1 = alarm 640 kPa, switching point 2 = refilling procedure required 620 kPa, switching point 3 = emergency shutdown 600 kPa). The thresholds of the switching points lie on so-called isochores so that false alarms are not caused by purely temperature effects. In this example, for a known density monitor, the optimal filling pressure in the reference space is 620 kPa. The errors of the other two switching points are a few kPa in the temperature ranges of -25°C and 50°C.

[0039] In the principle of a reference gas chamber, in order to properly compensate for temperature (for example, to enable outdoor use from -60°C to +60°C), the internal reference space must be filled with the same equipment gas.

[0040] Traditionally, SF6, CF4, N2, and mixtures thereof have been used in high-voltage technologies for liquefaction. In recent years, alternative gases with less environmental impact have become available on the market, and the GWP has already decreased significantly (referenced in references [7]-[9]). However, many facilities around the world are still filled with SF6, as are the reference chambers of the density monitors used. Furthermore, the replacement gases that need to be filled into the reference chambers in older density monitors with reference space principles still have considerably high global warming potentials.

[0041] A preferred embodiment of the present invention uses a gas with little or no climate impact (i.e., a non-greenhouse gas in this case), such as N2, Kr, or Ar, as the filling gas for the reference chamber. Overfilling is performed to achieve the same isocaustivity (specified in kPa / °C) as SF6 (or other greenhouse gases used as insulating gas). In particular, filling pressures about 3-40% higher are used to simulate the required filling pressure for SF6 between, for example, 1 bar and 12 bar. Therefore, the reference gas (e.g., a climate-neutral gas, i.e., a gas that does not contain greenhouse gases) is preferably filled at pressures of 1.5 bar and 20 bar.

[0042] In a preferred embodiment, a gas widely and inexpensively available on the market, such as industrial air, N2, Ar, or CO2, is used as the reference gas. Although CO2 is known as a greenhouse gas, it is far more climate-friendly than the greenhouse gas being monitored because its GWP = 1. Other noble gases are also possible or can be added. For example, the reference chamber may be filled in an inert (protective) gas atmosphere that already corresponds to the subsequent atmosphere within the reference chamber and welded for an airtight seal.

[0043] The density monitor preferably has a filling opening for filling a reference space and / or for changing the composition or pressure of the reference pressure.

[0044] To achieve the same accuracy and switching point distance as previous mechanical density monitors with a reference volume principle, it is preferable to partially compensate for the higher force of the gas pressure spring.

[0045] In a preferred embodiment of the present invention, at least two additional springs are used to compensate for the effects of this force.

[0046] The first spring helps to compensate for the force in the reference chamber. The first spring exerts a first elastic force on the partition wall, directly or indirectly, in the direction toward the reference space. For example, if the first spring is embodied as a compression spring, it acts on the partition wall from the harmful gas side, e.g., the measurement space side.

[0047] The first spring is preferably selected according to the pressure, for example, having a spring constant between 15 N / mm and 140 N / mm at filling pressures between 1 bar and 12 bar.

[0048] The second spring applies a second elastic force to the bulkhead in the opposite direction to the first elastic force. In particular, the second spring exerts a second elastic force on the bulkhead directly or indirectly toward the harmful gas. If the second spring is embodied as a compression spring, it is, for example, housed in a reference space and acts on the bulkhead from the reference space side.

[0049] The spring constant of the second spring is preferably around 20-30 N / mm. The second spring serves to extend the range relative to the reference chamber. This makes it possible, for example, to space the switching points far apart from each other or to expand the display range.

[0050] By selecting or setting different spring constants, preloads, and / or effective paths for the first and second springs, the density monitor can be adapted to common pressures, desired switching points or display ranges, and harmful gases.

[0051] To adjust the effective path, for example, at least one stopper may be provided to restrict the action of at least one spring to one or more specific regions of the deflection path of the partition wall.

[0052] A preferred embodiment of the present invention provides a temperature-compensated density monitor ("green gas" density monitor) that does not use environmentally harmful gases.

[0053] It is preferable to provide density monitors for high-voltage and medium-voltage switchgear that are temperature-compensated and use green gases (such as nitrogen, argon, and helium).

[0054] Adjusting the gradient of the isocorate (isocore) for customer gases (plant gas, adiabatic gas, hazardous gas) is preferably achieved by overfilling the reference chamber with green gas. This additional force from the gas spring can be compensated using the spring force.

[0055] A preferred embodiment uses a noble gas as the reference gas. For example, using argon gas (green gas) allows the reference chamber to be sealed under pressure (argon gas) without the use of additional components such as expanders or balls.

[0056] In a preferred embodiment, force compensation by the spring device or at least one of its springs is limited to a portion of the measurement range. For example, the first spring functions only in the low pressure range. Preferably, the first spring is used only up to the lowest switching alarm. This configuration results in a more accurate switching point because the spring is not used at the switching point.

[0057] In a preferred embodiment, different pressure ranges can be achieved through the interaction between the spring force and the reference force (i.e., the force due to the reference gas pressure in the reference space). Depending on the desired pressure range, the spring forces and preloads of the first and second spring elements can be designed accordingly.

[0058] A spring device can also be configured in other ways. For example, it can be configured as a spring device comprising at least one, or preferably more, springs. A “spring” should be understood as an elastically deformable mechanical element that exerts a spring force. A spring can be formed by one or more spring elements acting in parallel and / or series. The spring or spring element can be, for example, a coil spring, a gas spring, a rubber spring, an elastomer block, a leaf spring, a torsion spring, a bending spring, a spring ring, a disc spring, etc. Metal springs, especially compression coil springs, are preferred.

[0059] The following describes an exemplary embodiment in more detail with reference to the attached drawings. It shows the following: [Brief explanation of the drawing]

[0060] [Figure 1] This shows a cross-sectional view of a density monitor measurement sensor according to one embodiment of the present invention. [Figure 2] A cross-sectional view of the lower part of a density monitor connected to electrical equipment, according to a further embodiment of the present invention, is shown. [Figure 3] Figure 2 shows a cross-sectional view of the upper part of the density monitor. [Modes for carrying out the invention]

[0061] These figures illustrate different embodiments of a density monitor 14 connected to an electrical installation 12 filled with a harmful gas 10, with Figure 1 showing a measuring sensor 16 of the density monitor 14 according to an embodiment to illustrate the functional principle. Figure 3 shows an exemplary embodiment of a switching and / or display unit 18 of the density monitor 14 that can be connected to the measuring sensor 16 according to one of the embodiments.

[0062] Electrical equipment 12 is particularly gas-insulated high-voltage or medium-voltage equipment, such as high-voltage or medium-voltage switchgear, high-voltage or medium-voltage converters, high-voltage or medium-voltage pipelines, high-voltage or medium-voltage switching devices, or transformers. For gas insulation, the space 24 of the electrical equipment 12 is filled with insulating gas. Such insulating gases are greenhouse gases with high global warming potential (GWP) and are therefore harmful gases that have adverse effects on the climate. For example, the harmful gas 10 used as insulating gas in equipment 12 is one of the following gases: SF6, CF4 and N2, mixtures thereof, or SF6-substituted gases, as described in more detail in references [7]-[9]. The pressure at which the harmful gas 10 exists in the space 24 is hereafter referred to as the harmful gas pressure. This pressure (e.g., pressure SF6) is given as a predetermined filling pressure on the equipment side.

[0063] The density monitor 14 is used to monitor the gas density of the hazardous gas 10. The density monitor 14 has a measuring sensor 16 formed as a sensor for the equipment gas.

[0064] According to the illustrated embodiment, the density monitor 14 comprises a measurement space 20, a connection part 22 for connecting the measurement space 20 to a space 24 of electrical equipment 12 containing harmful gas 10, a closed reference space 26, a movable or divertable partition wall 28 for separating the reference space 26 from the measurement space 20, a partition wall divergence detection device 30 for detecting the divergence movement 31 of the partition wall 28, and a spring device 32.

[0065] The connection section 22 is formed as a pressure connection section for connecting the measurement space 20 to the space 24 of the equipment 12 in a pressure-resistant and liquid-tight manner. At least one gas passage 23 to the equipment 12 is formed in the connection section 22. In the illustrated embodiment, the connection section 22 has several gas introduction sections 23.

[0066] In a preferred embodiment, to form the measurement space 20 and the reference space 26, the interior of the housing 34 of the measuring sensor 16 is divided into several chambers by at least one metal bellows 36. The measurement chamber 38, which communicates with the connection 22, forms the measurement space 20. The reference chamber 40, which forms the reference space 26, is separated from the measurement space 20 by a metal bellows 36 or by one of a plurality of metal bellows 36a. A partition wall 28 is formed in contact with these metal bellows 36, 36a.

[0067] For example, the partition wall 28 is formed by the bellows base (bottom portion) 42 of the metal bellows 36, 36a.

[0068] In the illustrated embodiment, the reference chamber 40 is formed between a plurality of metal bellows 36a, 36i. The outer metal bellows 36a, with a partition wall 28, isolates the reference chamber 40 from the measurement space 20. The inner metal bellows 36i isolates the reference chamber 40 from the switching and display unit 18.

[0069] The partition deflection detection device 30 detects the movement of the partition wall 28, i.e., deflection 31, caused by changes in the pressure of the harmful gas relative to the pressure in the reference space 26. Since the reference space 26 is thermally connected to the measurement space 20 and therefore thermally connected to the harmful gas 10, temperature compensation is performed. Thus, as described in detail in reference [1], the gas density can be measured via the deflection 31 of the partition wall by the principle of the reference chamber.

[0070] The partition wall deviation detection device 30 has a transmission element 44 for transmitting the deviation of the partition wall 28 to the switching and / or display elements 46a-46d, 48 of the display unit 18. For example, a switching rod 49 connected to the partition wall 28 for common movement functions as the transmission element 44. The switching rod 49 has a pressure plunger 50 and a cross rod 52 having arms 54a-54d of different lengths. This makes it possible to switch different (e.g., first to fourth) switching elements 46a-46d at different positions of the partition wall 28's deviation to emit different alarm or switch-off signals, and thus enable switching at different gas density values ​​(switching points). Furthermore, the plunger 50 can drive a customized display unit 48.

[0071] An upper stopper 66 is positioned on the switching rod 49 to restrict the movement of the partition wall 28 if the pressure in the measurement space is too high.

[0072] In the density monitors described in references [1] to [5], the reference chamber is filled with the same gas and pressure as the equipment 12, whereas in the embodiment of the present invention, the reference space 26 is filled with a reference gas 56 that is different from the hazardous gas 10. This reference gas 56 has a significantly lower global warming potential than the hazardous gas 10. For example, the GWP of the reference gas 34 is lower than the GWP of the monitored hazardous gas 10 by a number of 2 or more.

[0073] In particular, a gas having a global warming potential (GWP) < 100, preferably GWP < 20, and especially preferably GWP < 2, is used as the reference gas. Particularly preferred is the use of low-cost, widely available gases on the market, such as industrial air or compressed air, N2, O2, Ar, or CO2. Here, CO2, with a global warming potential (GWP) of 1, is still significantly more climate-friendly than any insulating gas. In other embodiments, noble gases such as Ar, Kr, and He are used. In particular, when welding protection gases such as Ar and Kr are used, the reference chamber 40 can be immediately airtightly sealed during filling by welding.

[0074] As is known from reference [1], gas density is measured along an isocortic curve.

[0075] To equalize the isococcal gradient between the reference gas and the hazardous gas being monitored, the reference gas 56 is filled into the reference chamber 40 at a predetermined equipment filling pressure, i.e., an overpressure compared to the hazardous gas filling pressure. The overpressure is, for example, 2.5% to 45%. Therefore, the reference gas pressure is 2.5% to 45%, preferably 3% to 40%, higher than the hazardous gas pressure. Table 1 shows examples of various equipment filling pressure values ​​for SF6 as the gas being monitored and N2 containing 5% He as the reference gas.

[0076] [Table 1]

[0077] In possible embodiments, when manufacturing the density monitor 14, it is preferable that the reference chamber 40 is pre-fabricated as a separate structural unit filled by an airtight connection between an inner metal bellows 36a and an outer metal bellows 36i, and then installed within the housing 34. In the embodiments shown in Figures 1 and 2, the reference chamber 40 is formed by an inner bellows 40i, a bellows base 42, an outer bellows 40a, and a flange cover 62 which is part of the housing 34 of the sensor 16 (also called the sensor equipment). The bellows 40a, 40i are formed as metal bellows 36a, 36i and, as shown in the figures above, are connected at their ends to the flange cover 62 in a fluid-sealed (airtight and liquid-sealed) manner. The flange cover is provided with a filling hole 64 for filling the reference chamber 40. Thus, the density monitor is equipped with a filling device for filling the reference chamber 40 and / or for changing the reference gas or changing the reference gas pressure. This allows the reference gas pressure to be adapted to changes in the filling pressure within the equipment 12, and as a result, the excess pressure in the reference chamber 40 relative to the filling pressure within the equipment 12 can be adjusted.

[0078] The spring device 32 is intended to compensate for at least some of the following effects: namely, to compensate for at least some of the effects resulting from using a climate-friendly reference gas in the reference chamber instead of the harmful gas that should be monitored for temperature compensation.

[0079] Because the reference gas pressure increases compared to the harmful gas pressure, the gas spring formed from the filled metal bellows 36 exerts a greater force than conventional density monitors. The spring device 32 is designed to compensate for this force, especially due to excessive pressure.

[0080] In the illustrated embodiment, the spring device 32 has a first spring 58 that exerts a first spring force on the partition wall 28 in the direction of the reference gas. The first spring force functions to compensate for the force acting on the partition wall 29 due to the excess pressure in the reference space 26.

[0081] The first spring 58 is selected according to the filling pressure and, in embodiments with the measuring sensor 16 shown in the drawing, the typical dimensions shown in reference [1], and the reference gas according to Table 1, has a spring constant of, for example, between 15 N / mm at a filling pressure of 1 bar and 140 N / mm at a filling pressure of 12 bar. The first spring 58 functions to compensate for the force in the reference chamber. In general, the spring constant needs to be selected according to the respective measuring sensor, and in particular according to the area of ​​the partition or other pressurized surface.

[0082] The appropriate value can be easily found using a simple experiment based on the example and explanation provided in reference [1].

[0083] In the illustrated embodiment, the first spring 58 is formed as a compression spring and is positioned on the contact side of the diaphragm 28, i.e., within the measurement space 20, to exert a first spring force on the side of the partition wall 28 facing the equipment 12 or the measurement space 20. A spring guide 68 for guiding the first spring 58 is attached to the partition wall 28, for example, as a pin-shaped projection protruding from a bellows base 42. The free end of the projection of the spring guide 68 functions as a lower stopper 70 that restricts the movement of the partition wall 28 toward the measurement space 20.

[0084] Furthermore, the spring device 32 has a second spring 60 that exerts a second spring force on the partition wall 28 in the direction of the measurement space 20 or the harmful gas 10. The second spring 60 can extend the measurement range. In exemplary embodiments using the reference gas and filling values ​​in Table 1, and the typical dimensions in reference [1], the second spring 60 has a spring constant of approximately 20-30 N / mm. The second spring 60 serves to extend the range of the reference chamber 40, for example, to create a distant switching point or an extended display range.

[0085] In the illustrated embodiment, the second spring 60 is also formed as a compression spring and is positioned on the side of the partition wall 28 facing the reference chamber 40 within the reference chamber 40, and is used to set a switching point or display range.

[0086] By selecting and / or adjusting the spring constants and possible preloads of the springs 58 and 60 of the spring device 32, the measuring sensor 16 can be adjusted to a predetermined pressure, measuring range, and switching point or switching range.

[0087] Furthermore, the effective path of at least one spring, for example, the first spring 58, can be restricted by at least one stopper (not shown).

[0088] In one example, the first spring 58 acts only in the low-pressure range. For instance, the first spring is used only up to the lowest switching alarm, after which it strikes a stopper stationary against the housing 34, and the bulkhead 28 moves without being subjected to the first spring force in the remaining effective range. This arrangement results in more accurate and higher switching points because the first spring is not used at other switching points.

[0089] Using the density monitor 14, a density monitoring method can be performed to monitor the gas density of the harmful gas 10, and this method includes the following steps: a) Provide a closed reference space 26, which includes a partition wall 28 positioned between the reference space 26 and the harmful gas 10 to be monitored. b) A reference gas 56 having a low global warming potential, which is at least half that of the harmful gas 10, is supplied into the reference space 26 at a reference gas pressure that is higher than the filling pressure of the harmful gas 10. c) The force acting on the partition wall 28 due to the increased reference gas pressure within the reference space 26 is compensated by at least one spring device 32. d) The gas density is monitored by detecting deviations in the partition wall 28.

[0090] Further embodiments of this method, the density monitor 14 and its use, and the equipment 12 are achieved by applying the measures described herein, namely by filling the reference space 26 with a more climate-friendly reference gas 56, and by compensating for the inconvenience caused by the deviation between the harmful gas 10 being monitored and the reference gas 56 by higher pressure in the reference chamber 40 and by force compensation by a spring device 32 performed on the density monitor operating in the reference space. This is described in references [1] to [5]. Therefore, further possible features of embodiments of the density monitor 14 according to the present invention and their use are explicitly referenced and cited in references [1] to [5].

[0091] In a preferred embodiment of the density monitoring method, even highly climate-detrimental greenhouse gases such as SF6 can be monitored mechanically and temperature-compensated, without requiring such climate-detrimental gases to be present in the manufacture and operation of the density monitor 14 itself. In addition to the environmental benefits of using climate-friendly gases as reference gases, the costs associated with the manufacture, transportation, assembly, and setup of the density monitor 14 can also be significantly reduced. This is because the density monitor 14 does not require the safety measures and procedures necessary for hazardous gases, and can use much cheaper gases as reference gases.

[0092] Any drawbacks regarding the accuracy and normal spread of the switching point or display are preferably eliminated by a spring device 32 that operates purely mechanically using a simple spring.

[0093] According to some embodiments not shown in detail, the spring device 32 may include an adjustment device for changing at least one force parameter of the spring device 32. For example, the spring device 32 may include a preload adjustment device for adjusting the preload of at least one of the springs 58, 60, in particular the second spring 60. This means that, in particular, the display area and at least one or more switching points, or the distance between them (with respect to gas density), can be adjusted.

[0094] To mechanically monitor greenhouse gas densities in a more climate-friendly and cost-effective manner, a density monitoring method (10) for monitoring the densities of harmful gases has been proposed, which includes: a) Provide a closed reference space (26) with a movable partition (28) positioned between the reference space (26) and the harmful gas (10) to be monitored. b) A reference gas (56) with a low global warming potential (at least half) compared to the hazardous gas (10) is provided in the reference space (26) at a reference gas pressure higher than the filling pressure (10) of the hazardous gas. c) The force acting on the partition wall (28) due to the increased reference gas pressure within the reference space (26) is compensated for by the spring device (32). d) The gas density is monitored by detecting deviations in the partition wall (28).

[0095] Furthermore, a gas density monitor (14), its use in such a process, and an electrical installation (12) equipped therewith are proposed. [Explanation of symbols]

[0096] 10. Harmful Gases 12 Electrical equipment 14 Density Monitor 16 sensors 18 Switching and / or display unit 20 Measurement space 22 Connection part 23. Gas introduction section to the equipment 24 rooms (gas room with electrical equipment) 26 Reference space 28 Bulkhead 30. Bulkhead deviation motion detection device 31 Deviation 32 Spring device 34 Sensor housing 36 Metal bellows 36a Outer metal bellows 36i Inner metal bellows 38 Measurement Chamber 40 Reference Chamber 40a Bellows outer side (reference chamber) 40i Bellows Interior (Reference Chamber) 42 Bellows base (partition wall - reference chamber) 44 Communication elements 46a First switching element 46b Second switching element 46c Third switching element 46d Fourth switching element 48 Display section 49 Switching Rod 50 plungers 52 Cross Rod 54a First Arm 54b Second Arm 54c Third Arm 54d Fourth Arm 56. Standard gas 58. First spring 60 Second spring 62 Flange cover 64 Filling port (reference chamber) 66 Upper stopper 68 Spring Guide 70 Lower stopper

Claims

1. A density monitoring method (10) for monitoring the gas density of harmful gases, a) Provide a closed reference space (26) with a movable partition (28) between the reference space (26) and the harmful gas (10) to be monitored, b) A reference gas (56) with a low global warming potential (GR) of at least half that of the hazardous gas (10) is provided in the reference space (26) at a reference gas pressure higher than the filling pressure of the hazardous gas (10). c) The force acting on the partition wall (28) due to the increase in the reference gas pressure in the reference space (26) is compensated by the spring device (32), d) A density monitoring method that includes detecting deviation movement of a partition wall (28) in order to monitor the gas density.

2. The density monitoring method according to claim 1, characterized in that step b) includes at least one of the following steps. b1) A step of providing a reference gas (56) with GWP < 100, or GWP < 20, or GWP < 2, where GWP is the CO2 over 100 years according to IPCC AR5. ２ The converted value is shown. b2) Air, N ２ , O ２ Noble gases, Ar, Kr, He, CO ２ A gas is provided as a reference gas (56) from the group consisting of at least two mixtures of these gases, and mixtures formed from one or more of these gases and additional gases that are added.

3. The density monitoring method according to claim 1 or 2, further comprising step b) providing a reference gas (56) with a reference gas pressure 2.5 to 45% higher than the filling pressure of the harmful gas (10).

4. c1) The step of applying a first spring force of a spring device (32) acting toward the reference space (26) to the bulkhead (28) in order to compensate for the force caused by the increased reference gas pressure, c2) A density monitoring method according to any one of claims 1 to 3, characterized by comprising the step of applying a second spring force acting in the direction of a harmful gas to a partition wall (28) in order to expand the range over which the gas density can be monitored.

5. The density monitoring method according to claim 4, characterized by comprising at least one of the following steps. 5.1 Select a first spring force corresponding to the filling pressure of the harmful gas (10) and / or the reference gas pressure. 5.2 The spring constant of the first spring (58) of the spring device (32) that exerts the first spring force is selected according to the filling pressure of the harmful gas (10) and / or the reference gas pressure. 5.3 The second spring force is adjusted according to a gas density value or gas density range that is desirable for at least one switching point or switching range. 5.4 Select spring constants for the first spring (58) of the first spring device (32) that exerts a first spring force, and / or the second spring (60) of the second spring device (32) that exerts a second spring force, according to a gas density value or gas density range desirable for at least one switching point or display range. 5.5 Select a preload for at least one spring (58, 60) of the spring device (32) that corresponds to a desired gas density value or gas density range for at least one switching point or indication or switching range. 5.6 The effect of at least one spring (58, 60) in the spring device (32) is limited to a portion of the deflection path of the bulkhead (28). 5.7 The first spring force acting on the first spring (58) in the spring device (32) is limited to a range below a predetermined gas density threshold.

6. The density monitoring method according to any one of claims 1 to 5, characterized in that, in step a), metal bellows (36a, 36) are provided to separate a reference space (26) from a measurement space (20) containing harmful gas (10), and a partition wall (28) is formed in contact with the metal bellows (36a, 36).

7. A density monitor (14) for monitoring the gas density of a harmful gas (10), Measurement space (20) and A connection part (22) for connecting the measurement space (20) to the space (24) containing the harmful gas (10), Unlike the hazardous gas (10) being monitored, the closed reference space (26) is filled with a reference gas (56) having a global warming potential (GWP) < 100, where GWP is defined as the 100-year CO2 warming potential based on IPCC AR5. ２ The conversion value is shown, and the reference gas (56) is a closed reference space (26) that is filled with an excess pressure compared to the standard pressure or filling pressure of the harmful gas (10) when the density monitor (14) is operating as intended. A partition wall (28) separates the reference space (26) from the measurement space (20), A bulkhead deflection detection device (30) for detecting the deflection movement of the bulkhead (28), The spring mechanism (32) is a density monitor that elastically applies force to the partition wall (28) to compensate for excessive pressure in the reference space (26).

8. The reference gas (56) is air, N ２ , O ２ Noble gases, Ar, Kr, He, CO ２ The density monitor according to claim 7, characterized in that it is selected from the group consisting of, at least two mixtures of these gases, and a mixture formed from one or more of these gases and an additional gas to be added.

9. The spring device (32) is A first spring (58) acts on the partition wall (28) in the direction toward the reference space (26) to compensate for the force caused by excessive pressure, In order to expand the range over which the gas density can be monitored, a second spring (60) acts on the partition wall (28) in the direction toward the measurement space (20), A density monitor according to any one of claims 7 or 8, characterized by comprising:

10. The use of a density monitor (14) for monitoring the gas density of a harmful gas (10), wherein the density monitor (14) Measurement space (20) and A connection part (22) for connecting a measurement space (20) to a room (24) containing a harmful gas (10), Closed reference space (26), A partition wall (28) separates the reference space (26) from the measurement space (20), A bulkhead deviation detection device (30) for detecting deviation movement of the bulkhead (28), The device includes a spring device (32) that applies elastic force to the partition wall (28), Here, unlike the harmful gas (10) to be monitored, a reference gas (56) having a global warming potential GWP < 100 is filled at a reference gas pressure higher than the filling pressure of the harmful gas (10), where GWP indicates the conversion value in 100 years based on IPCC AR5 for CO ２ and is shown as Here, the force acting on the partition wall (28) due to the increased reference gas pressure in the reference space (26) compared to the filling pressure of the harmful gas (10) is compensated by a spring device (32) using a density monitor.

11. The reference gas (56) is air, N ２ , O ２ Noble gases, Ar, Kr, He, CO ２ The use of a density monitor according to claim 10, characterized in that it is selected from the group consisting of, at least two mixtures of these gases, and mixtures of one or more of these gases with further gas additives.

12. The spring device (32) is To compensate for the force caused by excessive pressure, a first spring (58) acts on the partition wall (28) in the direction toward the reference space (26), Use of a density monitor according to claim 10 or 11, further comprising: a second spring (60) acting on a partition (28) in the direction toward a harmful gas (10) in order to extend the range over which the gas density can be monitored.

13. A use of a density monitor according to any one of claims 10 to 12, or a density monitor according to any one of claims 8 to 9, for carrying out the method according to any one of claims 1 to 6.

14. A room (24) filled with a harmful gas (10) as an insulating gas having a predetermined filling pressure, A density monitor (14) according to any one of claims 7 to 9 used, An electrical device (10) for monitoring the concentration of harmful gases is connected to a room (24).

15. The electrical equipment according to claim 14, characterized in that the reference gas pressure in the reference space (26) is 2.5 to 45% higher than the filling pressure.

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