HK1170841B - An encapsulated switchgear, a process for providing the same, and the use of a dielectric compound having a boiling point of above -25℃ in an insulation medium for an encapsulated switchgear - Google Patents

Description

Encapsulated switching device, method for providing same and use of a dielectric compound having a boiling point above-25 ℃ in its insulating medium

The present invention relates to an encapsulated switchgear, a method for providing an encapsulated switchgear and the use of a dielectric compound having a boiling point above-25 ℃ in an insulating medium for an encapsulated switchgear, in particular a medium voltage encapsulated switchgear.

In medium or high voltage encapsulated switchgears, the electrically active element is arranged in a gastight housing which defines an insulating space, which usually contains an insulating gas and which separates the housing from the electrically active element without letting electrical current through. Thus, the metal-encapsulated switchgear configuration is more space-saving compared to a switchgear insulated only by the surrounding air.

For conventional encapsulated switchgears, an insulating gas comprising a dielectric compound having a boiling point below-25 ℃ is used to prevent condensation over the full operating temperature range. The required pressure of the insulating gas and/or the amount of dielectric compound contained in said insulating gas is determined by gas pressure measurements (with or without temperature compensation) or direct density measurements.

The equipment used for gas pressure measurement is typically relatively complex and expensive.

In addition, it is generally necessary for the insulating gas to have a slight overpressure, which in medium-voltage switchgears is often about 100 mbar to about 500 mbar, in order to allow accurate pressure measurements in the insulating space of the switchgear. Due to this overpressure, the enclosure of the switchgear may be subjected to mechanical stress and is therefore prone to gas leakage if appropriate technical measures are not taken.

However, the requirements on the gas tightness of the switching devices currently used are very strict, since conventional insulating gases with high insulating and arc extinguishing properties have some environmental impact when released into the atmosphere, and in particular have a relatively high Global Warming Potential (GWP).

For this reason, the housing of the switching device must be very robust even in the above-mentioned overvoltage situations.

Also, in order to allow repair work to be performed inside the enclosure, a device is required which evacuates the enclosure before opening it and then reintroduces the insulating gas before operation of the switchgear can be restarted.

The construction of the switchgear housing is therefore relatively complex, which, in addition to the expensive gas pressure measuring devices, is also due to the relatively high costs of conventional switchgear.

With regard to the potential impact of the switchgear on the environment and the corresponding constructional requirements for the housing, attempts have been made in the past to replace the conventional insulating gas with a suitable substitute.

For example, WO2008/073790 discloses a dielectric gaseous compound which has, among other properties, a boiling point in the range of about-20 ℃ to about-273 ℃, which has low ozone depletion, preferably no ozone depletion and which has a GWP of less than about 22,200. In particular, WO2008/073790 discloses a number of different compounds that do not fall under the general chemical definition.

Furthermore, EP-A-0670294 discloses the use of perfluoropropane as dielectric gas and EP-A-1933432 relates to trifluoroiodomethane (CF)₃I) And to the use thereof as insulating gas in gas-insulated switchgear.

In order to improve the breakdown field strength compared to standard insulating mediA, US-A-4175048 proposes A gaseous insulator comprising A compound selected from the group consisting of perfluorocyclohexene and hexafluoroazomethane.

However, the use of compounds according to the documents given above in encapsulated switchgear requires complex gas pressure measurement measures as indicated above. Also, if a large amount of insulating gas leaks from the housing, the reaction time for establishing sufficient insulating properties is often relatively long. In this case, it must be understood that the panel is disassembled to prevent damage to the switchgear.

The object of the present invention is therefore to provide a packaged switching device which can be operated in an environmentally friendly manner and at the same time allows a very simple and cost-effective design by meeting the highest safety requirements.

The term "encapsulated switchgear" according to the present invention includes air-insulated or gas-insulated metal (or other) encapsulated switchgear.

The term "electrically active element" as used in the context of the present invention is to be interpreted broadly to include conductors, wire arrangements, switches, conductive parts, etc.

The invention allows the establishment of a two-phase system due to the feature that the dielectric compound contained in the insulating medium comprises a compound having a boiling point above-25 ℃. The system comprises an insulating gas comprising a gaseous part of the dielectric compound under operating conditions. The gaseous portion is in equilibrium with the liquid portion of the dielectric compound. Thus, the liquid part acts as a reservoir for the dielectric compound, which enters the gas phase at a very low gas partial pressure.

The present invention is based on the following findings: a certain concentration of the dielectric compound in the insulating gas of such a two-phase system can be achieved by a suitable selection of the dielectric compound, which is sufficient for most applications of encapsulated switchgears and in particular for medium-voltage encapsulated switchgears.

In view of this, dielectric compounds having a relatively high vapor pressure are particularly preferred. Examples of such dielectric compounds are described in detail below.

If the insulating gas leaks from the enclosure, the equilibrium between the gas phase and the liquid phase (and thus the required concentration of the dielectric compound in the insulating gas) is maintained or easily reestablished. Therefore, even if the case leaks, the required insulation performance is maintained. Therefore, there is no need to immediately interrupt the operation, which makes the switchgear very safe.

Given the fact that a sufficient concentration of the dielectric compound and thus a sufficient insulating property can be easily established as long as at least a part of the dielectric compound is in the liquid phase, a complicated gas pressure measuring device can be avoided. In contrast, a simple check for the presence of the liquid fraction is sufficient to ensure that the insulating gas contains a sufficient concentration of dielectric compound and thus has the required high insulating properties.

According to a preferred embodiment, the switchgear device of the invention comprises a container defining at least a part for containing the liquid part of the dielectric compound contained in the enclosure. This allows checking the required insulation properties by simply checking the liquid level in the container.

The container is usually arranged in an insulating space.

In order to ensure that the presence of the liquid fraction contained within the housing can be determined by checking the liquid level in the container, it is further preferred that the housing comprises a collecting device for collecting at least a part of the liquid fraction of the dielectric compound and transferring it to the container. According to a particularly preferred embodiment, the inner surface of the bottom wall of the housing is at least partially inclined, thus forming a spout opening into the container. The container is therefore preferably arranged at the lowest point of the insulation space. During operation, liquid collected at the bottom of the housing flows down the sloped inner surface of the bottom wall of the housing and is received by the container.

In addition, the switchgear preferably comprises an indicator for determining the amount of liquid part of the dielectric compound in the insulating space, the indicator being arranged in a compartment which is spaced apart from the insulating space and which is connected with the container by a passage. Generally, the indicator is formed by a portion of the channel that extends into a separate compartment.

According to a further embodiment, the housing comprises a transparent area allowing the container and/or the indicator to be viewed from the outside. Thus, the determination of a sufficient insulating property of the insulating gas can be made by simply observing and visually checking whether or not a liquid phase is present through the transparent region. The transparent region may, for example, be in the form of a surface glass, on which the lowest operating level of the liquid is indicated.

In the above-mentioned embodiments, wherein the indicator is formed by a portion of the channel extending into the separate compartment, said portion is typically transparent. As in this embodiment, the compartment comprising the indicator is typically placed according to the height of the insulating space, a direct measurement is possible, since the liquid in the compartment and the liquid in the insulating space will have the same level at the same pressure.

In principle, the dielectric compound and optional carrier gas may be introduced at any location in the insulating space. In order to allow introduction of the dielectric compound into the system during operation, a corresponding apparatus may be provided. For example, a nozzle may be provided in the housing wall through which an aerosol, in which small droplets of a liquid dielectric compound are dispersed in a carrier gas, may be introduced into the insulating space. Alternatively, the liquid dielectric compound can be introduced into the bottom part of the insulating space and preferably into the container through an inlet without a carrier gas.

The invention allows the use of dielectric compounds which have excellent insulating properties, in particular high breakdown field strengths, and which at the same time are non-toxic and have no influence on the environment when released into the atmosphere. This also makes the design of the switchgear simpler, since it is not necessary to provide a device for withdrawing and reintroducing the insulating medium. If repair work has to be carried out and therefore the enclosure of the switchgear has to be opened, the insulating gas is simply released into the atmosphere. The liquid part of the dielectric compound, which is usually quite small, can be removed with a simple outlet, stored in a simple reservoir and reintroduced by pouring it back into the insulating space after the completion of the repair work and before restarting the operation of the switchgear.

According to a preferred embodiment, the dielectric compound is a fluoroketone having 4 to 12 carbon atoms. Thus, an insulating medium having high insulating ability and extremely low GWP can be provided.

In general, the fluoroketones according to this embodiment have the following general structure:

R1-CO-R2

wherein R1 and R2 are at least partially fluorinated chains which, independently of one another, are straight-chain or branched and have from 1 to 10 carbon atoms. This definition encompasses perfluoroketones as well as hydrofluoroketones. Generally, these fluoroketones have a boiling point of at least-5 ℃ at ambient pressure.

It has now been found that for many applications of the insulating gas, such as in the medium-pressure range, a sufficient concentration or molar ratio, i.e. the ratio between the number of molecules of the fluoroketone and the number of molecules of the remaining components of the medium (typically the carrier gas or buffer gas), and thus also a sufficient breakdown field strength, can be obtained even at very low operating temperatures, e.g. down to about-5 ℃ or even lower, without additional measures such as external heating or vaporization.

Preferably, the fluoroketone has from 4 to 10 carbon atoms, more preferably from 4 to 8 carbon atoms, and most preferably 6 carbon atoms (also known as C6-fluoroketone). As mentioned above, the C6-fluoroketone may be a perfluoroketone (having the formula C)₆F₁₂O) or hydrofluoroketones.

Among the most preferred fluoroketones having 6 carbon atoms, it has been found that dodecafluoro-2-methylpentan-3-one is particularly preferred.

It was previously only believed that dodecafluoro-2-methylpentan-3-one (also known as 1, 1, 1, 2,2, 4, 5, 5, 5-nonafluoro-4- (trifluoromethyl) -3-pentanone, perfluoro-2-methyl-3-pentanone or CF₃CF₂C(O)CF(CF₃)₂) Can be used for completely different applications, namely processing of molten reactive metals (as mentioned in WO 2004/090177), for cleaning of steam reactors (as mentioned in WO 02/086191) and in fire extinguishing systems or in liquid form for cooling electronic systems or in small power plants for Rankine processes (as mentioned in EP- ｃA-1764487).

Dodecafluoro-2-methylpentan-3-one is transparent, colourless and virtually odourless. The structural formula is as follows:

dodecafluoro-2-methylpentan-3-one has an average life of about 5 days in the atmosphere and has a GWP of only about 1. In addition, its Ozone Depletion Potential (ODP) is zero. Therefore, the environmental burden is much lower than any conventional insulating gas.

In addition, dodecafluoro-2-methylpentan-3-one is non-toxic and provides outstanding margins of safety for humans.

Dodecafluoro-2-methylpentan-3-one has a boiling point of 49.2 ℃ at 1 bar. Its vapor pressure (i.e., the pressure at which the vapor is in equilibrium with its non-vapor phase) is about 40kPa at 25 ℃. In view of this high vapor pressure of dodecafluoro-2-methylpentan-3-one, insulating gases having a breakdown field strength sufficient for many applications, in particular in the medium-pressure range, are also generally available at very low temperatures, as low as, for example, -30 ℃.

According to a preferred embodiment of the invention, the insulating gas is a gas mixture comprising, in addition to the dielectric compound and in particular the fluoroketone, a carrier (or buffer) gas. In a particularly preferred embodiment, the gas mixture comprises air or is air, in particular dry air, or comprises or is at least one air component, in particular selected from carbon dioxide (CO)₂) Oxygen (O)₂) And nitrogen (N)₂). Alternatively, the insulating gas may consist essentially of a dielectric compound.

Based on the discovery that dodecafluoro-2-methylpentan-3-one decomposes at temperatures of 550 deg.C or higher to highly reactive fluorocarbon compounds having a relatively low number of carbon atoms, it is preferred that the insulating gas contains sufficient oxygen (O)₂) With which fluorocarbon compounds can react to form inert compounds, such as CO₂。

The insulating properties of the insulating gas, and in particular its breakdown field strength, can be controlled by the temperature, pressure and/or composition of the insulating medium. By using a two-phase system comprising a dielectric compound, in particular a fluoroketone, in both liquid and gas phases, an increase in temperature not only causes an increase in absolute pressure, but also an increase in the concentration of the dielectric compound in the insulating gas due to the higher vapor pressure.

According to a particularly preferred embodiment of the invention, the molar ratio of the fluoroketone, in particular of dodecafluoro-2-methylpentan-3-one, in the insulating gas is at least 1%, preferably at least 2%, more preferably at least 5%, more preferably at least 10%, most preferably at least 15%. These preferred molar ratios are referred to given standard or specified operating conditions. In the case of deviations, the molar ratios can also differ from these preferred values.

The significance of an insulation medium comprising dodecafluoro-2-methylpentan-3-one in a molar ratio of at least 1% or 2%, respectively, is based on the following findings: the insulating gas with this molar ratio can also be obtained at very low temperatures as low as-30 ℃ (for 2%) and at very low temperatures as low as-40 ℃ (1%) and has a dielectric strength sufficient for, for example, medium-voltage gas-insulated switchgears which are operated at insulating gas pressures below 1.5 bar, in particular around 1 bar.

In addition to the switchgear described above, the invention also relates to a method in which a dielectric compound is introduced into the insulation space of the switchgear, said dielectric compound being introduced in such an amount that, under operating conditions, the insulation medium comprises an insulation gas containing a gaseous part of said dielectric compound, said gaseous part being in equilibrium with a liquid part of said dielectric compound. A two-phase system (two-part system) with the above-mentioned advantages can thus be established in the insulation space of the switchgear.

According to a preferred embodiment of the method, the dielectric compound is introduced in a liquid state, whereby only a part of the dielectric compound evaporates in the insulating space. Thus, the two-phase system can be established in a very simple and easy manner.

It is further preferred that the dielectric compound is introduced into the bottom part of the insulating space. This allows the fill level of the dielectric compound to be monitored immediately after introduction. Furthermore, according to this embodiment a uniform distribution of the gaseous fraction in the insulation space can be easily established.

The invention therefore relates in particular to medium-voltage encapsulated switchgear. The term "medium voltage" as used herein refers to a voltage in the range of 1kV to 72 kV. However, applications in the high voltage range (greater than 72kV) and in the low voltage range (below 1kV) are equally feasible.

The skilled person is aware of medium voltage encapsulated switchgear to which the invention is particularly suitable. For example, reference is made here to a medium-voltage switchgear of the ZX series (ABB AG), a medium-voltage switchgear of the GHA type (AREVA T & D) or a medium-voltage switchgear of the NXPLUS C type (Siemens AG).

The invention is described in further detail in connection with fig. 1 via the following embodiments, fig. 1 schematically representing a medium voltage encapsulated switchgear according to the invention.

According to fig. 1, the switchgear 2 comprises a housing 4 defining an insulating space 6 and an electrically active element 8 arranged in the insulating space 6. In the embodiment shown, the electrically active element 8 comprises a switching element 9 and three bus bars 11a, 11b, 11c connected to said switching element 9. The insulating space 6 contains an insulating medium containing an insulating gas. The insulating gas comprises a gaseous portion of a dielectric compound in equilibrium with a liquid portion of the dielectric compound.

The droplets 10 of the liquid fraction that condense on the wall 12 of the housing 4 flow or fall downwards in a direction towards the bottom wall 12' (as indicated by the arrows). In the embodiment shown in fig. 1, the bottom wall 12 ' has a multi-stage configuration, in which the segment 12 ' a is inclined (in particular slightly inclined), turned downwards into a strongly inclined (in particular vertical) segment 12 ' b and opens into the container 14. Thus, liquid collected at the bottom of the housing flows down the inner surface of the bottom wall 12' and drains into the reservoir 14. The inner surface of the bottom wall 12' acts as a collecting device 15 for collecting the liquid part of the dielectric.

A passage 16, preferably in the form of a tube, leads from the container 14 to an indicator 18, which indicator 18 is in the embodiment shown in the figures comprised in a compartment 20 arranged in the front 21 of the panel and is thus spaced apart from the insulating space 6.

In the embodiment shown, the indicator 18 is formed by a portion of the channel 16 that extends into the compartment 20, the portion being transparent. Also, the outer wall 20' of the compartment 20 is transparent, thus forming a crystal.

Since the compartment 20 comprising the indicator 18 is arranged in correspondence of the height of the container 14, a direct measurement of the filling level of the container 14 can be made by observing through the outer wall 20' of the compartment 20.

Alternatively, the crystal may be formed by a transparent portion of the housing itself. In this embodiment, the surface glass is arranged so that the container in the insulating space can be observed from the outside. As a particular option, the crystal itself can be a container.

List of reference numerals

2 switching device

4 outer cover

6 insulating space

8 electrically active element

9 switching element

11a, 11b, 11c bus bar

12 casing wall

12' bottom wall of housing

12' a bottom wall

12' b bottom wall vertical section

14 container

15 collecting device

16 channels

18 indicator

20 compartments

Outer wall of the 20' compartment

21 front panel

Claims (46)

1. Encapsulated switchgear comprising a housing (4) defining an insulating space (6) and an electrically active component (8, 9, 11a, 11b, 11c) arranged in the insulating space (6), the insulating space (6) containing an insulating medium, characterized in that the insulating medium contains a dielectric compound having a boiling point higher than-25 ℃ and being a fluoroketone having 4-12 carbon atoms.

2. The encapsulated switchgear device of claim 1, said dielectric compound having a boiling point higher than-20 ℃.

3. Encapsulated switching device as claimed in claim 2, characterized in that the fluoroketone has 4 to 10 carbon atoms.

4. Encapsulated switching device as claimed in claim 3, characterized in that the fluoroketone has 4 to 8 carbon atoms.

5. Encapsulated switching device according to claim 4, characterised in that the fluoroketone has 6 carbon atoms.

6. The encapsulated switchgear as claimed in claim 5, characterized in that said fluoroketone is of formula C₆F₁₂Perfluoroketone of O.

7. The encapsulated switchgear as claimed in claim 6, characterized in that said fluoroketone is dodecafluoro-2-methylpentan-3-one.

8. The encapsulated switchgear as claimed in claim 1, characterized in that the insulating medium comprises, under operating conditions, an insulating gas containing a gaseous part of the dielectric compound, the gaseous part being in equilibrium with a liquid part of the dielectric compound, and the insulating gas is a gas mixture, the gas mixture further comprising a carrier gas.

9. Encapsulated switchgear according to claim 8, characterized in that the carrier gas contains air or at least one air component.

10. Encapsulated switchgear according to claim 9, characterized in that the air component is selected from the group consisting of carbon dioxide, oxygen and nitrogen.

11. The encapsulated switchgear as claimed in claim 1, characterized in that said insulating medium comprises, under operating conditions, an insulating gas containing a gaseous part of said dielectric compound, said gaseous part being in equilibrium with a liquid part of said dielectric compound, and it comprises a container (14) defined for containing at least a part of the liquid part of said dielectric compound contained in said enclosure (4).

12. Encapsulated switchgear according to claim 11, characterized in that it further comprises collecting means (15, 12 ', 12a ', 12b ') for collecting at least part of the liquid part of the dielectric compound and transferring it to the container (14).

13. The encapsulated switchgear device according to claim 11, characterized in that it further comprises an indicator (18) for determining the amount of the liquid part of the dielectric compound in the insulating space (6), the indicator (18) being arranged in a space spaced from the insulating space (6) and connected to the container (14).

14. The encapsulated switchgear device of claim 13, said housing (4) comprising a transparent area allowing the container (14) and/or said indicator (18), respectively, to be observed from the outside.

15. The encapsulated switchgear of any of claims 1 to 14, said switchgear being a metal encapsulated switchgear.

16. The encapsulated switchgear of any one of claims 1 to 14, said switchgear being a medium voltage encapsulated switchgear.

17. Encapsulated switchgear comprising a housing (4) defining an insulating space (6) and an electrically active component (8, 9, 11a, 11b, 11c) arranged in the insulating space (6), the insulating space (6) comprising an insulating medium comprising a fluoroketone-containing dielectric compound having a boiling point higher than-25 ℃ and being of 4-12 carbon atoms, characterized in that under operating conditions the insulating medium comprises an insulating gas containing a gaseous part of the dielectric compound, the gaseous part being in equilibrium with a liquid part of the dielectric compound.

18. The encapsulated switchgear device of claim 17 said dielectric compound having a boiling point above-20 ℃.

19. The encapsulated switchgear device of claim 18 said dielectric compound having a boiling point above-5 ℃.

20. The encapsulated switchgear as claimed in claim 17, characterized in that the dielectric compound is a fluoroketone having 4 to 10 carbon atoms.

21. The encapsulated switchgear as claimed in claim 20, characterized in that the dielectric compound is a fluoroketone having 4 to 8 carbon atoms.

22. The encapsulated switchgear as claimed in claim 21, characterized in that the dielectric compound is a fluoroketone having 6 carbon atoms.

23. The encapsulated switchgear as claimed in claim 22, characterized in that said fluoroketone is of formula C₆F₁₂Perfluoroketone of O.

24. The encapsulated switchgear as claimed in claim 23, characterized in that said fluoroketone is dodecafluoro-2-methylpentan-3-one.

25. The encapsulated switchgear as claimed in claim 23, characterized in that the insulating gas is a gas mixture, which further comprises a carrier gas.

26. The encapsulated switchgear as claimed in claim 25, characterized in that the carrier gas comprises air or at least one air component.

27. The encapsulated switchgear as claimed in claim 26, characterized in that the air component is selected from the group consisting of carbon dioxide, oxygen and nitrogen.

28. The encapsulated switchgear of any of claims 17-27, said switchgear being a metal encapsulated switchgear.

29. The encapsulated switchgear of any one of claims 17 to 27, said switchgear being a medium voltage encapsulated switchgear.

30. Encapsulated switchgear comprising a housing (4) defining an insulating space (6) and an electrically active component (8, 9, 11a, 11b, 11c) arranged in the insulating space (6), the insulating space (6) containing an insulating medium, characterized in that the insulating medium contains a dielectric compound having a boiling point higher than-5 ℃ and being a fluoroketone having 4-12 carbon atoms.

31. The encapsulated switchgear as claimed in claim 30, characterized in that the insulating medium comprises an insulating gas containing a gaseous part of the dielectric compound, which gaseous part is in equilibrium with a liquid part of the dielectric compound, and the insulating gas is a gas mixture, which gas mixture further comprises a carrier gas, under operating conditions.

32. The encapsulated switchgear as claimed in claim 31, characterized in that the carrier gas comprises air or at least one air component.

33. The encapsulated switchgear as claimed in claim 32, characterized in that the air component is selected from the group consisting of carbon dioxide, oxygen and nitrogen.

34. The encapsulated switchgear device according to claim 30, characterized in that it comprises a container (14) defining at least a part for containing the liquid part of said dielectric compound contained in said enclosure (4).

35. The encapsulated switchgear device according to claim 34, characterized in that it further comprises a collecting device (15, 12 ', 12a ', 12b ') for collecting at least a part of the liquid part of the dielectric compound and transferring it to the container (14).

36. The encapsulated switchgear as claimed in claim 34, characterized in that it further comprises an indicator (18) for determining the amount of the liquid part of the dielectric compound in the insulating space (6), the indicator (18) being arranged in a space spaced apart from the insulating space (6) and connected to the container (14).

37. The encapsulated switchgear device of claim 36, said housing (4) comprising a transparent area allowing the container (14) and/or said indicator (18), respectively, to be observed from the outside.

38. The encapsulated switchgear of any one of claims 30 to 36, said switchgear being a metal encapsulated switchgear.

39. The encapsulated switchgear of any one of claims 30 to 37, said switchgear being a medium voltage encapsulated switchgear.

40. Method of providing an encapsulated switchgear according to any of claims 7 to 29 by introducing a dielectric compound into the insulation space (6) of the switchgear, wherein the amount of the dielectric compound introduced is such that under operating conditions the insulation medium comprises an insulation gas comprising a gaseous part of the dielectric compound, which gaseous part is in equilibrium with a liquid part of the dielectric compound.

41. The method of claim 40, wherein said dielectric compound is introduced in a liquid state, whereby only a portion of said dielectric compound evaporates into said insulating space (6).

42. The method of claim 41, wherein the dielectric compound is introduced into a bottom portion of the insulating space (6).

43. Use of a dielectric compound having a boiling point higher than-25 ℃ in an insulating medium comprising an insulating gas containing a gaseous part of the dielectric compound in equilibrium with a liquid part of the dielectric compound under operating conditions for encapsulated switchgear.

44. Use of a dielectric compound according to claim 43, wherein the encapsulated switchgear is a medium voltage encapsulated switchgear.

45. The use of claim 43, wherein the dielectric compound has a boiling point above-20 ℃.

46. The use of claim 45, wherein the dielectric compound has a boiling point above-5 ℃.