Methods, apparatus, uses and installations 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 of a harmful gas. The present invention further relates to a density monitor for monitoring the gas density of a harmful gas. The present invention further relates to the use of a density monitor for monitoring the gas density of a harmful gas. Finally, the present invention relates to an electrical installation comprising a sealed / closed space such as a housing, container, tank, etc., containing an insulating gas (harmful gas) that has a negative impact on the environment, and a density monitor for monitoring the gas density of the insulating gas. [Background technology]

[0002] For technical background, reference is made to the following documents:

[0003] [1] “Insulating gas density monitoring”, brochure of Trafag AG, bearing the printed symbol “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 on 20 January 2022 from: https: / / de.wikipedia.org / wiki / Treibhauspotential [7] Website Novec Isoliergase 3M Deutschland, downloaded on 20 January 2022 from: https: / / www.3mdeutschland.de / 3M / de_DE / novec- de / anwendungen / isoliergas / [8] “Powering a sustainable future. 3M TM Novec TM “Insulating Gases”, 3M brochure downloaded on January 20, 2022 from: 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, in particular a measuring device, for monitoring the gas density of a gas to be monitored. As is known from documents [1]-[5], density monitors are used in particular for monitoring the density of gases (SF6) used as insulation in gas-insulated high- and medium-voltage installations, such as voltage switchgear, converters, pipelines, switching devices, transformers, etc.

[0005] For this purpose, for example from the literature

[10] , density monitors based on the electronic measurement principle are known, which are equipped with an electronic density sensor as transducer-detector, which has a quartz oscillator that is placed in the gas and provides a frequency signal proportional to the density of the gas, which is then fed to an electronic evaluation unit.

[0006] On the other hand, density monitors based on mechanical measuring principles are well established on the market and, due to their mechanical measuring principle, are very reliable and require almost no maintenance even over very long periods of time. In the simplest and most common case, a partition operating through a reference space is connected to the measurement space, such that a change in gas density causes a movement of the partition and thus an actuation of a switch. For this purpose, for example, in density monitors known from the literature [1]-[5], a metal bellows partition is connected to a switch, such that a movement of the partition over a minimum distance triggers the switching process. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] German Patent Application No. 10 2010 055 249 ([2] DE 10 2010 055 249 B4) [Patent Document 2] German Patent Application No. 10 2013 115 007 ([3] DE 10 2013 115 007 B4) [Patent Document 3] German Patent Application No. 10 2016 123 588 ([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”, brochure by Trafag AG, printed designation “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 Summary of the Invention [Problem to be solved by the invention]

[0009] The aim of the present invention is to make density monitoring more environmentally friendly by using a mechanical measurement principle with 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 device, a method of use and an electrical installation according to the dependent claims.

[0011] Advantageous embodiments are the subject matter of the subclaims.

[0012] According to a first aspect thereof, the present invention provides a density monitoring method for monitoring the gas density of a harmful gas, comprising: a) providing a closed reference space with a partition between the reference space and the hazardous gas being monitored; b) providing a reference gas having a global warming potential that is at least two times lower than the harmful gas in a reference volume at an increased reference gas pressure compared to the harmful gas pressure for the harmful gas; c) compensating the force acting on the partition wall due to an increase in the reference gas pressure in the reference space by means of a spring device; and d) monitoring gas density by detecting deflection of the bulkhead.

[0013] According to a further aspect, the present invention provides a density monitor for monitoring gas density of a harmful gas, comprising: Measurement space (volume), a connection for connecting the measurement space (volume) to a room in which harmful gas is present; a closed reference space (volume) filled with a reference gas (global warming potential GWP<100, where GWP indicates a 100-year CO2 equivalent value in accordance with IPCC AR5) different from the hazardous gas to be monitored, the reference gas being filled at an excess pressure compared to the pressure in the measurement space during the intended operation of the density monitor; a partition separating the reference space from the measurement space; a bulkhead shear motion detection device for detecting shear motion of the bulkhead; and a spring means for resiliently exerting a force on the septum to compensate for excess pressure in the reference space.

[0014] According to a further aspect, the present invention provides the use of a density monitor for monitoring the gas density of a harmful gas, comprising: A measurement space; a connection part for connecting the measurement space to a space containing harmful gas; A closed and sealed reference space, A partition wall separating the reference space and the measurement space; a bulkhead deflection detector for detecting deflection of the bulkhead; at least one spring device for elastically exerting a force on the bulkhead; Wherein, the reference space contains a reference gas having a global warming potential GWP<100, which is different from the harmful gas to be monitored, where GWP indicates a 100-year CO2 equivalent value based on IPCC AR5, and the reference gas pressure is greater than the pressure of the harmful gas in the measurement space; Here, the use of a density monitor is provided in which the force acting on the diaphragm due to an increase in the reference gas pressure in the reference space is compensated by a spring device.

[0015] According to a further aspect, the present invention provides an electrical installation comprising a room (space) filled with an insulating gas as a harmful gas, and a density monitor connected to said room for monitoring the gas density of the harmful gas, the density monitor comprising: a measurement space connected to the room; A reference space filled with a reference gas different from the harmful gas to be monitored, the reference gas having a global warming potential GWP<100, where GWP indicates a 100-year CO2 equivalent value based on IPCC AR5, the reference space having an excessive pressure compared to the pressure of the harmful gas spreading in the room; a partition wall separating the reference space and the measurement space; a bulkhead deflection detector for detecting deflection of the bulkhead; and at least one spring device that elastically applies a force to the partition to compensate for excess pressure in the spring reference space.

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

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

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

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

[0020] For example, the spring device comprises a first spring exerting a first spring force, preferably formed as a first compression spring acting on the harmful gas side of the partition wall and pushing it towards the reference space.

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

[0022] For example, the spring device has a second spring exerting a second spring force, which 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: Adjusting the initial spring force in response to the hazardous gas pressure and / or the reference gas pressure. In particular, preferred embodiments of the present invention include selecting a spring constant of the first spring in response to the hazardous gas pressure and / or the reference gas pressure.

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

[0025] Preferred embodiments of at least one aspect of the present invention include: A preload of at least one spring of the spring device is selected 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 of the spring device is limited to a portion of the deflection path of the septum.

[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] In accordance with a preferred embodiment of at least one aspect of the present invention, a metal bellows is provided for separating the reference space from the measurement space containing the noxious gas, and the partition is formed adjacent the metal bellows.

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

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

[0031] Preferably, the use according to the invention or an advantageous embodiment thereof serves to carry out the method according to the invention or an advantageous embodiment thereof.

[0032] Preferably, the density monitor according to the invention or an advantageous embodiment thereof is configured to carry out the method according to the invention or an advantageous embodiment thereof. Preferably, the method according to the invention or an advantageous embodiment thereof is carried out using a density monitor according to the invention or an advantageous embodiment thereof.

[0033] Preferably, the method according to the invention or an advantageous embodiment thereof is carried out in an electrical installation according to the invention or an advantageous embodiment thereof.

[0034] Features or steps disclosed with respect to one of the aspects of the invention (method, device, use, installation) or advantageous embodiments thereof may also be provided for one of the other aspects of the invention or advantageous embodiments thereof.

[0035] Advantageous embodiments of the invention relate to the use of density monitors, such as density monitors using gases with low greenhouse effect, in particular green gases or climate neutral gases, as well as density monitoring methods carried out therewith. A preferred embodiment of the invention relates to a monitoring device arranged to monitor the density of SF6, which operates mechanically without the use of SF6.

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

[0037] As is known from documents [1]-[5], this type of density monitor or temperature compensated pressure switch measures against a reference space. In such density monitors known from the past, the reference space must be filled gas-tight with the same gas to be measured as the gas to be monitored, at a pressure approximately equal to the installation pressure. This means that this type of known density monitor must be filled with a greenhouse gas, such as SF6, which is to some extent harmful to the environment. To date, to ensure sufficient temperature compensation, it is necessary to use the same insulating gas as used by the installation manufacturer. The gas chamber (installation gas) and the reference space are separated, for example, by a metal bellows. The density and pressure differences between the gas chambers result in a mechanical stroke of the metal bellows. This gas (SF6) is a greenhouse gas with a very high GWP (>10,000) and is subject to increasingly stringent environmental legislation. For this, see document [6]. The behaviour of the gas and the functioning of the density monitor are specifically described in document [1], to which document [1] is referred for more detailed points.

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

[0039] The principle of the reference gas chamber requires that the internal reference space be filled with the same facility gas in order to provide proper temperature compensation (eg to allow outdoor use from -60°C to +60°C).

[0040] Traditionally, for liquefaction, SF6, CF4, N2 and their mixtures have been used in high-voltage technology. In recent years, alternative gases with less harmful environmental impact have been available on the market, which have already significantly reduced their GWP (see references [7]-[9]). However, many installations around the world are still filled with SF6, as are the reference chambers of the density monitors used. Moreover, the replacement gases that must be filled in the reference chambers of previous density monitors with the reference space principle still have a significantly high global warming potential.

[0041] A preferred embodiment of the invention uses a gas with low or, more preferably, no climatic impact (i.e. here a gas with no greenhouse effect) such as N2, Kr or Ar as the filling gas of the reference chamber. In order to achieve the same isochoricity (specified in kPa / °C) as SF6 (or other greenhouse gas used as insulating gas), an overfill is performed. In particular, to simulate the required filling pressure of SF6, for example between 1 bar and 12 bar, a filling pressure about 3-40% higher is used. Thus, the reference gas (for example a climate neutral gas, i.e. a gas without greenhouse gases) is preferably filled at a pressure between 1.5 bar and 20 bar.

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

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

[0044] To achieve density monitor accuracy and switching point distances similar to previous mechanical density monitors with 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 effect of this force.

[0046] The first spring serves to compensate for the forces of the reference chamber. The first spring exerts a first elastic force directly or indirectly on the partition wall in the direction towards 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. from the measurement space side.

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

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

[0049] The spring constant of the second spring is preferably around 20-30 N / mm. The second spring serves for range extension with respect to the reference chamber, which allows, for example, to place switching points farther apart from each other or to extend 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 prevailing pressures, desired switch points or display ranges, and hazardous gases.

[0051] To adjust the effective path, for example, at least one stop may be provided which limits the action of the at least one spring to one or more specific regions of the deflection path of the bulkhead.

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

[0053] Preferably, a density monitor for high and medium voltage switchgear is provided that has temperature compensation and uses green gas (nitrogen, argon, helium, etc.).

[0054] Adjustment of the slope of the isochor for customer gases (plant gases, insulating gases, hazardous gases) is preferably accomplished by overfilling the reference chamber with green gas. This additional force from the gas spring can be compensated for using the spring force.

[0055] A preferred embodiment uses a noble gas as the reference gas, for example argon gas (green gas), which 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, the force compensation by the spring device or at least one of its springs is limited to a part of the measuring range. For example, the first spring only functions in the low pressure range. Preferably, the first spring is only used up to the lowest switching alarm. This arrangement allows a more accurate switching point, since no spring is used at the switching point.

[0057] In a preferred embodiment, different pressure ranges can be realized through the interaction of the spring force with a reference force (i.e., a force due to a reference gas pressure in a 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] The spring device can also be configured in a different way. For example, it can be configured as a spring device with at least one, but preferably several, springs. A "spring" is to be understood as an elastically deformable mechanical element exerting a spring force. The spring can be formed by one spring element or several spring elements acting in parallel and / or in series. The spring or spring element can be, for example, a coil spring, a gas pressure spring, a rubber spring, an elastomeric block, a leaf spring, a torsion spring, a bending spring, a spring ring, a disc spring, etc. Metal springs, in particular compression coil springs, are preferred.

[0059] Exemplary embodiments are explained in more detail below with reference to the accompanying drawings, which show: [Brief description of the drawings]

[0060] [Figure 1] 1 illustrates a cross-sectional view of a measurement sensor of a density monitor according to one embodiment of the present invention. [Diagram 2] 13 shows a cross-sectional view of a lower portion of a density monitor connected to electrical equipment according to a further embodiment of the present invention; [Diagram 3] 3 shows a cross-sectional view of the top of the density monitor of FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0061] These figures show different embodiments of a density monitor 14 connected to an electrical installation 12 filled with a harmful gas 10, with Fig. 1 showing a measurement sensor 16 of the density monitor 14 according to an embodiment for illustrating the functioning principle, and Fig. 3 showing an exemplary embodiment of a switching and / or display part 18 of the density monitor 14, which can be connected to the measurement sensor 16 according to one of the embodiments.

[0062] The electrical installation 12 is in particular a gas-insulated high- or medium-voltage installation, such as a high- or medium-voltage switchgear, a high- or medium-voltage converter, a high- or medium-voltage pipeline, a high- or medium-voltage switching device or a transformer. For gas insulation, the space 24 of the electrical installation 12 is filled with an insulating gas. Such insulating gases are greenhouse gases with a high global warming potential (GWP) and therefore harmful gases that have a negative impact on the climate. For example, the harmful gas 10 used as insulating gas in the installation 12 is one of the gases SF6, CF4 and N2, mixtures thereof or SF6 substitutes, as described in more detail in documents [7]-[9]. The pressure at which the harmful gas 10 is present in the space 24 is referred to below as the harmful gas pressure. This pressure (e.g. pressure SF6) is given as a predefined filling pressure on the installation side.

[0063] The density monitor 14 is used to monitor the gas density of the harmful gas 10. The density monitor 14 has a measurement sensor 16 which is configured as a sensor for the facility gas.

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

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

[0066] To form the measurement space 20 and the reference space 26, in a preferred embodiment, the interior of the housing 34 of the measurement sensor 16 is divided into several chambers by at least one metal bellows 36. A measurement chamber 38 communicating with the connection 22 forms the measurement space 20. A reference chamber 40 forming the reference space 26 is separated from the measurement space 20 by the metal bellows 36 or by one of a number of metal bellows 36a. A partition wall 28 is formed in contact with this metal bellows 36, 36a.

[0067] For example, the partition wall 28 is formed by the bellows base (bottom surface 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 the partition 28 separates the reference chamber 40 from the measurement space 20. The inner metal bellows 36i separates the reference chamber 40 from the switching and display portion 18.

[0069] The bulkhead deflection detector 30 detects the deflection 31 of the bulkhead 28 caused by the change in pressure of the hazardous gas relative to the pressure in the reference space 26. The reference space 26 is thermally connected to the measurement space 20 and thus also to the hazardous gas 10, thereby providing temperature compensation. Thus, the reference chamber principle allows the measurement of the gas density via the deflection 31 of the bulkhead, as explained in detail in [1].

[0070] The diaphragm deflection detector 30 comprises a transmission element 44 for transmitting the deflection of the diaphragm 28 to the switching or display elements 46a-46d, 48 of the switching and / or display unit 18. For example, a switching rod 49 connected to the diaphragm 28 for a common movement serves as the transmission element 44. The switching rod 49 comprises a pressure plunger 50 and a cross rod 52 with arms 54a-54d of different lengths. This allows different (e.g. first to fourth) switching elements 46a-46d to be switched at different positions of the deflection of the diaphragm 28 and thus at different gas density values ​​(switching points), for example to emit different alarm or switch-off signals. Furthermore, the plunger 50 can drive a customized display unit 48.

[0071] An upper stop 66 is arranged on the switching rod 49 to limit the movement of the partition 28 if the pressure in the measuring space is too high.

[0072] While in the density monitors of documents [1]-[5] the reference chamber is filled with the same gas and at the same pressure as the equipment 12, the reference space 26 in the embodiment of the present invention is filled with a reference gas 56 that is different from the harmful gas 10. This reference gas 56 has a significantly lower global warming potential than the harmful gas 10. For example, the GWP of the reference gas 34 is lower than the GWP of the harmful gas 10 being monitored by dividing it by a factor of two or more.

[0073] In particular, gases with a GWP<100, preferably GWP<20, particularly preferably GWP<2, are used as reference gases. Particular preference is given to using low-cost and widely available gases on the market, such as industrial or compressed air, N2, O2, Ar or CO2, where CO2, with its global warming potential GWP=1, is still significantly more climate-friendly than any insulating gas. In other embodiments, noble gases, such as Ar, Kr, He, are used. In particular, when welding protection gases, such as Ar, Kr, are used, the reference chamber 40 can be immediately sealed gas-tight during filling by welding.

[0074] As is known from the literature [1], the gas density is measured along an isochoric curve.

[0075] In order to equalize the isochoric gradient of the reference gas and the hazardous gas to be monitored, the reference gas 56 is filled in the reference chamber 40 with a predetermined facility filling pressure, i.e. with an overpressure compared to the hazardous gas filling pressure. The overpressure is, for example, 2.5%-45%. The reference gas pressure is therefore 2.5%-45%, preferably 3%-40%, higher than the hazardous gas pressure. Examples of different facility filling pressure values ​​for SF6 as the monitored gas and N2 with 5% He as the reference gas are shown in Table 1.

[0076] [Table 1]

[0077] In a possible embodiment, when manufacturing the density monitor 14, the reference chamber 40 is preferably prefabricated as a separate structural unit filled by a gas-tight connection of the inner metal bellows 36a and the outer metal bellows 36i and then installed in the housing 34. In the example shown in Fig. 1 and Fig. 2, the reference chamber 40 is formed by the inner bellows 40i, the bellows base 42, the outer bellows 40a and a flange cover 62 which is part of the housing 34 of the sensor 16 (also called the sensor installation). The bellows 40a, 40i are formed as metal bellows 36a, 36i and are connected in a fluid-tight (gas-tight and liquid-tight) manner at their ends, which are shown in the above figures, to the flange cover 62. The flange cover is provided with a filling hole 64 for filling the reference chamber 40. The density monitor thus comprises a filling device for filling the reference chamber 40 and / or for replacing the reference gas or for changing the reference gas pressure. This allows the reference gas pressure to be adapted to changes in the filling pressure in the facility 12 and, as a result, the excess pressure in the reference chamber 40 relative to the filling pressure in the facility 12 can be adjusted.

[0078] The spring device 32 is intended to at least partially compensate for the effects that arise from the use of a climate-friendly reference gas in the reference chamber instead of the harmful gas to be monitored for temperature compensation.

[0079] As the reference gas pressure increases compared to the noxious gas pressure, the gas spring formed from filled metal bellows 36 exerts a greater force than conventional density monitors. The spring device 32 is specifically configured to compensate for this force due to excess pressure.

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

[0081] The first spring 58 is selected depending on the filling pressure and, in the embodiment with the measurement sensor 16 shown in the drawing, the typical dimensions given in document [1] and the reference gas according to table 1, has for example a spring constant 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 serves to compensate the forces of the reference chamber. In general, the spring constant must be selected depending on the respective measurement sensor and, in particular, depending on the area of ​​the partition or other pressurized surface.

[0082] Suitable values ​​can be easily found using simple experimentation based on the examples and explanations given in the literature [1].

[0083] In the embodiment shown, the first spring 58 is formed as a compression spring and exerts a first spring force on the contact side of the diaphragm 28, i.e., on the side of the diaphragm 28 that is arranged, for example, in the measurement space 20 and faces the device 12 or the measurement space 20. A spring guide 68 that guides the first spring 58 is attached to the diaphragm 28, for example as a pin-shaped projection that projects from the bellows base 42. The free end of the projection of the spring guide 68 serves as a lower stop 70 that limits the movement of the diaphragm 28 towards the measurement space 20.

[0084] Furthermore, the spring device 32 comprises a second spring 60 which exerts a second spring force on the partition 28 in the direction of the measurement space 20 or the harmful gas 10. The second spring 60 allows to extend the measurement range. In an exemplary embodiment using the reference gases and filling values ​​of table 1 and the typical dimensions of document [1], the second spring 60 has a spring constant of about 20-30 N / mm. The second spring 60 serves to extend the range of the reference chamber 40 and can, for example, create far-away switching points or an extended indication range.

[0085] In the embodiment shown, the second spring 60 is also formed as a compression spring and is located in the reference chamber 40 on the side of the partition 28 facing the reference chamber 40 and is used to set a switching point or indication range.

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

[0087] Additionally, the effective path of at least one spring, for example the first spring 58, may be limited by at least one stop (not shown).

[0088] In one example, the first spring 58 only acts for the low pressure range, for example, the first spring is only used up to the lowest switching alarm, after which it hits a stop that is stationary relative to the housing 34, and the bulkhead 28 moves without the first spring force for the remaining effective range. This arrangement allows for more accurate and higher switching points, since the first spring is not used for other switching points.

[0089] The density monitor 14 can be used to perform a density monitoring method for monitoring the gas density of the hazardous gas 10, the method including the following steps: a) Providing a closed reference space 26 with a partition 28 disposed between the reference space 26 and the hazardous gas 10 to be monitored. b) A reference gas 56 having a global warming potential that is at least two times lower than that of the harmful gas 10 is fed into the reference space 26 at a reference gas pressure that is increased compared to the filling pressure of the harmful gas 10 . c) The force acting on the partition 28 due to the increased reference gas pressure in the reference space 26 is compensated for by at least one spring device 32 . d) Monitoring gas density by detecting deflection of bulkhead 28.

[0090] Further embodiments of the method, the density monitor 14 and its use as well as the installation 12 are achieved by applying the measures described herein, i.e. by filling the reference space 26 with a more climate-friendly reference gas 56 and by compensating the inconvenience caused by the deviation between the monitored harmful gas 10 and the reference gas 56 by a higher pressure in the reference chamber 40 and a compensating force by the spring device 32 on the density monitor operating in the reference space. This is described in documents [1]-[5]. For further possible features of the embodiments of the density monitor 14 according to the invention and their uses, explicit reference and inference is therefore made to documents [1]-[5].

[0091] In a preferred embodiment of the density monitoring method, the gas density can be monitored in a mechanical and temperature compensated manner even for highly climate-harming greenhouse gases such as SF6, without such climate-harming gases being required for the manufacture and operation of the density monitor 14 itself. In addition to the environmental aspects of using a climate-friendly gas as the reference gas, the costs of manufacturing, transporting, assembling and setting up the density monitor 14 are also significantly reduced, since the density monitor 14 does not require the safety precautions and measures required for harmful gases and much cheaper gases can be used as the reference gas.

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

[0093] According to some embodiments not shown in detail, the spring device 32 may be provided with an adjustment device for changing at least one force parameter of the spring device 32. For example, the spring device 32 is provided with 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, in particular, that the display area and at least one or several switching points or their mutual distance (in terms of gas density) can be adjusted.

[0094] In order to mechanically monitor the gas density of greenhouse gases in a more climate-friendly and cost-effective manner, a density monitoring method (10) for monitoring the gas density of harmful gases has been proposed, which includes: a) Providing a closed reference space (26) with a partition (28) movably disposed between the reference space (26) and the hazardous gas (10) to be monitored. b) providing a reference gas (56) having a global warming potential at least two times lower than that of the hazardous gas (10) in the reference volume (26) at a reference gas pressure higher than the filling pressure (10) of the hazardous gas; c) The force acting on the partition (28) due to the increased reference gas pressure in the reference space (26) is compensated for by a spring device (32). d) Monitoring gas density by detecting deflection of the bulkhead (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 23 Gas inlet to equipment 24 Room (Electrical Equipment Gas Chamber) 26 Reference space 28 Bulkhead 30 Bulkhead deviation detection device 31 Deflection 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 inside (reference chamber) 42 Bellows base (partition - reference chamber) 44 Transmission Elements 46a First switching element 46b Second switching element 46c Third switching element 46d Fourth switching element 48 Display section 49 Switching rod 50 Plunger 52 Cross Rod 54a 1st Arm 54b 2nd Arm 54c 3rd Arm 54d 4th Arm 56 Reference 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 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 hazardous gas (10) to be monitored; b) providing a reference gas (56) having a global warming potential at least two times lower than that of 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 the force acting on the partition (28) due to an increase in the reference gas pressure in the reference space (26) by means of a spring device (32); d) detecting deflection of the bulkhead (28) to monitor gas density.

2. 2. The density monitoring method of claim 1, wherein step b) comprises at least one of the following steps: b1) Providing a gas as a reference gas (56) having a GWP < 100, preferably a GWP < 20, particularly preferably a GWP < 2, where GWP is the percentage of CO2 emissions over 100 years according to IPCC AR5. ２ Shows the conversion value. b2) Air, N ２ , O ２ , rare gases, Ar, Kr, He, CO ２ A gas from the group consisting of mixtures of at least two of these gases with one another and mixtures essentially formed from one or more of these gases with a further gas added is provided as a reference gas (56).

3. The density monitoring method according to claim 1 or 2, wherein step b) comprises providing a reference gas (56) with a reference gas pressure that is 2.5-45% higher than the filling pressure of the hazardous gas (10).

4. c1) applying a first spring force of a spring device (32) acting in a direction towards the reference space (26) to the partition (28) to compensate for the force caused by the increased reference gas pressure; c2) applying a second spring force to the partition (28) acting in the direction of the harmful gas in order to expand the range in which the gas density can be monitored.

5. 5. The density monitoring method according to claim 4, characterized in that it comprises at least one of the following steps: 5.1 Select a first spring force depending on the filling pressure of the harmful gas (10) and / or the reference gas pressure. 5.2 Selecting a spring constant of the first spring (58) of the spring device (32) exerting a first spring force depending on the filling pressure of the harmful gas (10) and / or the reference gas pressure. 5.3 Adjusting the second spring force according to a desired gas density value or range for at least one switching point or range. 5.4 Select a spring constant for the first spring (58) of the spring device (32) exerting a first spring force and / or the second spring (60) of the spring device (32) exerting a second spring force according to a gas density value or gas density range desired for at least one switching point or indication 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 Limiting the effect of at least one spring (58, 60) in the spring device (32) to a portion of the deflection path of the bulkhead (28). 5.7 Limiting a first spring force acting on a first spring (58) in the spring device (32) to a range below a predetermined gas density threshold.

6. 6. The method for monitoring density according to claim 1, characterized in that in step a) a metal bellows (36a, 36) is provided for separating the reference space (26) from the measurement space (20) containing the harmful gas (10), and a partition (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), comprising: A measurement space (20); a connection (22) for connecting the measurement space (20) to a space (24) containing the harmful gas (10); A closed reference space (26) filled with a reference gas (56) having a global warming potential (GWP) of <100, different from the harmful gas (10) to be monitored, where GWP is the percentage of CO2 per 100 years according to IPCC AR5. ２ a closed reference space (26) which indicates a conversion value and in which a reference gas (56) is filled at an excess pressure compared to the standard pressure of the hazardous gas (10) or the filling pressure of the hazardous gas (10) when the density monitor (14) is operating as intended; a partition (28) separating the reference space (26) from the measurement space (20); a bulkhead shear motion detection device (30) for detecting shear motion of the bulkhead (28); A spring means (32) resiliently applies a force to the septum (28) to compensate for excess pressure in the reference space (26).

8. The reference gas (56) is air, N ２ , O ２ , rare gases, Ar, Kr, He, CO ２ 8. The density monitor according to claim 7, characterized in that the gases selected from the group consisting of mixtures of at least two of these gases with one another and mixtures essentially formed from one or more of these gases with a further gas being added.

9. The spring device (32) a first spring (58) acting on the partition (28) in the direction towards the reference space (26) to compensate for the force caused by the excess pressure; a second spring (60) acting on the partition (28) in a direction towards the measurement space (20) to expand the range in which the gas density can be monitored; A density monitor according to claim 7 or 8, characterized in that it comprises:

10. 1. Use of a density monitor (14) for monitoring the gas density of a harmful gas (10), comprising: A measurement space (20); a connection (22) for connecting the measurement space (20) to a room (24) containing the harmful gas (10); A closed reference space (26), a partition (28) separating the reference space (26) from the measurement space (20); a bulkhead deflection detector (30) for detecting deflection of the bulkhead (28); a spring device (32) for applying a resilient force to the partition wall (28); Here, the reference space (26) is filled with a reference gas (56) different from the hazardous gas (10) to be monitored and having a global warming potential GWP<100 at a reference gas pressure higher than the filling pressure of the hazardous gas (10), where GWP is the CO2 concentration in 100 years according to IPCC AR5. ２ Show the conversion value, Use of a density monitor, wherein the force acting on the partition (28) by the reference gas pressure in the reference space (26) increased compared to the filling pressure of the harmful gas (10) is compensated by a spring device (32).

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

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

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

14. a chamber (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 for use, An electrical installation in which a device (10) for monitoring gas concentrations of harmful gases is connected to a room (24).

15. 15. Electrical installation 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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