Gas insulating device with liquefaction prevention means

Abstract

A medium or high voltage electrical device (10) and a method for maintaining the composition of an insulating gas mixture within the medium or high voltage electrical device, the device (10) comprising a sealed chamber (12) for containing electrical components, a gas mixture ensuring electrical insulation and / or extinguishing of electrical arcs generated within the chamber, the gas mixture comprising at least one insulating gas and at least one diluent gas, and a receptacle (20) having an opening The receptacle has a portion (26) and at least one wall (22, 24), at least one wall (22, 24) being a heatable wall (24), the receptacle being positioned to receive liquefied gas, and the device (10) comprises a sealed chamber (12) having a receptacle (20) further comprising a heating element (42) for heating the heatable receptacle walls (22, 24), and a dielectric insulation layer (30) located between the heatable receptacle wall (24) and the chamber (12).

Description

[Technical Field]

[0001] The present invention relates to a medium or high voltage electrical device including an insulating gas mixture and a means for maintaining the gas composition, and a method thereof. [Background technology]

[0002] In many medium- and high-voltage electrical devices, electrical insulation and arc quenching can be achieved by insulating gases within the enclosed device. This insulating gas must have relatively high dielectric strength, good thermal conductivity, and low dielectric loss. One commonly used insulating gas is SF6. Another insulating gas used in medium- and high-voltage devices contains a mixture of heptafluoroisobutyronitrile and a diluent gas. However, at low temperatures, the insulating gas may liquefy, thereby reducing the concentration of the gaseous insulating gas within the electrical device, potentially affecting the isolation properties of the device.

[0003] Once liquefied, the liquid may not immediately revert to the gas phase even if the temperature within the electrical device increases. This may be the case if the entire electrical device is heated. This is because the transition from liquid to gas is an endothermic process, cooling the liquid and thereby slowing its evaporation from the liquid to gas.

[0004] Methods and devices are known for heating the entire enclosure of a gas-insulated electrical device above the liquefaction temperature of the insulating gas, but these methods and devices result in significant heat loss and consume a significant amount of energy to maintain the entire equipment at a constant temperature.

[0005] Therefore, there is a need for improved apparatus and methods for maintaining the composition of insulating gas mixtures at low temperatures. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] US Patent Application Publication No. 2014 / 083737 Summary of the Invention

[0007] The invention is defined in the appended claims.

[0008] In one aspect, the present invention provides a medium or high voltage electric device comprising: a sealed chamber having electrical components; a gas mixture ensuring electrical insulation and / or extinguishing of electric arcs generated in the chamber, the gas mixture comprising at least one insulating gas and at least one diluent gas; and a receptacle having an opening and at least one wall, the at least one wall being heatable, the receptacle positioned to receive a liquefied gas, the device further comprising a heating element for heating the heatable receptacle wall; and a dielectrically and thermally insulating layer located between the heatable receptacle wall and the chamber.

[0009] In a second aspect, the present invention provides a method for maintaining the composition of an insulating gas mixture in a medium or high voltage electrical device, wherein the gas mixture ensures electrical insulation and / or extinguishing of electrical arcs generated in the device, the device being according to the first aspect, the device further comprising temperature, liquid and / or pressure sensors, the method comprising: collecting liquefied gas in a receptacle; heating the liquefied gas collected in the receptacle with a heating element when the temperature or pressure falls below a threshold temperature or pressure, or when the liquid level rises above a threshold level; The present invention provides a method comprising:

[0010] The invention may be put into practice in various ways and some specific embodiments will now be described by way of example for illustrating the invention with reference to the accompanying figures. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view of a device according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] The meanings of terms used in this specification are explained below to explain the present invention in detail.

[0013] As used herein, the terms "medium voltage" and "high voltage" are used in their conventionally accepted manner. In other words, the term "medium voltage" refers to voltages greater than 1000 volts (V) for AC and 1500 V for DC, but not exceeding 52,000 V for AC or 75,000 V for DC. The term "high voltage" refers to voltages strictly greater than 52,000 V for AC or 75,000 V for DC.

[0014] As used herein, the term "comprising" means "including," but not limited to, the specified components, process steps, etc. The term "comprising" encompasses, but is not limited to, instances of "essentially comprising," the specified components, process steps, etc.

[0015] The terms gas, insulating gas, gas mixture, and gas insulating mixture may be used interchangeably herein.

[0016] The gas mixture or gas insulator may be a gas mixture containing a fluorinated compound. For example, the fluorinated compound may be heptafluoroisobutyronitrile. Other possible fluorinated compounds may be 1,1,1,3,4,4,4-heptafluoro-3-(trifluoromethyl)-2-butanone (CF3C(O)CF(CF3)2), 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1,3,3,3-tetrafluoropropene (HFO-1234ze), or fluorooxirane. Combinations of any of these gases may also be used.

[0017] Heptafluoroisobutyronitrile, also known herein as iCFCN, has the formula (I) of (CF)CFCN and corresponds to 2,3,3,3-tetrafluoro-2-trifluoromethylpropanenitrile, which has CAS number 42532-60-5. The boiling point is −4.9° C. at 1013 hPa (the boiling point is determined in accordance with ASTM D1120-94, “Standard Test Method for Boiling Point of Engine Coolants”).

[0018] The gas mixture may comprise a fluorinated compound and a diluent gas. Preferably, the gas mixture comprises heptafluoroisobutyronitrile and a diluent gas.

[0019] The diluent gas is a natural gas or gas mixture with a very low or even zero global warming potential (GWP). The diluent gas can be carbon dioxide, nitrogen, oxygen, or air with a GWP equal to 1, advantageously dry air with a GWP equal to 0, or a mixture thereof. The diluent gas can be selected from the list consisting of carbon dioxide, nitrogen, oxygen, air (80% N2 and 20% O2), advantageously dry air, and any mixture thereof.

[0020] The gas mixture may contain at least 80% by volume, preferably at least 90% by volume, of carbon dioxide. Advantageously, heptafluoroisobutyronitrile can be used in a mixture of carbon dioxide and oxygen.

[0021] The apparatus or device 10 of the present invention includes a housing defining a leak-proof insulating space or sealed chamber, and an electrically active part or electrical component disposed within the insulating space. As used herein, the terms leak-proof insulating space, insulating space, and sealed chamber are used interchangeably. The insulating space may include a gas insulating mixture. The gas insulating mixture may include heptafluoroisobutyronitrile, as described above.

[0022] The terms "electrically active part" and "electrical component" may be used interchangeably. They should be interpreted broadly and may include conductors, conductor arrangements, switches, conductive components, surge arresters, etc. In particular, the apparatus of the present invention includes switchgear, in particular gas-insulated encapsulated switchgear, or parts and / or components thereof, in particular busbars, bushings, cables, gas-insulated cables, cable joints, current transformers, voltage transformers, surge arresters, earthing switches, disconnectors, load break switches, and / or circuit breakers. The switchgear may be metal-encapsulated switchgear.

[0023] When the device is used outdoors, low ambient temperatures cool the housing, including the housing walls and chamber walls, which also cools the insulating gas mixture within the housing. The insulating gas may condense along the walls of the device, creating gradients or variations in gas concentration and changes in the insulating properties of the insulating gas.

[0024] Gradients and / or variations in gas concentration can be avoided by having an electrical device that includes a sealed chamber with electrical components, a receptacle within the chamber for collecting the liquefied gas, and a heating element for reheating the liquefied gas in the local environment.

[0025] Device 10 includes a sealed chamber 12. By sealed, we mean that chamber 12 is leakproof to the gas contained therein. Sealed chamber 12 includes a central shell having a length extending between two end portions. In one embodiment, chamber 12 has a cylindrical shape. In another embodiment, chamber 12 has another geometric shape. Chamber 12 includes an upper portion and a bottom portion, or bottom. The bottom portion is located proximate the lowest point within chamber 12. The bottom portion of chamber 12 includes a surface referred to as the chamber floor. The chamber floor is a surface within device 10 proximate the lowest point within chamber 12. The upper portion is located proximate the highest point within chamber 12.

[0026] 1 , device 10 includes a receptacle 20 within chamber 12. Receptacle 20 is positioned within chamber 12 to receive condensed or liquefied insulating gas. In one embodiment, at least one wall of chamber 12 is sloped toward receptacle 20 so that liquid flowing down the wall of chamber 12 due to gravity flows toward receptacle 20. For example, a portion of the wall within chamber 12 can be shaped like a condensing finger to direct liquid down the side of the finger and into receptacle 20.

[0027] The receptacle 20 includes at least one wall 22. The receptacle 20 may include a receptacle bottom wall, or floor 24. The receptacle wall 22 may be adjacent to the receptacle floor 24.

[0028] At least one receptacle wall is heatable. The heatable wall may be in proximity to the heating element 42. The heatable wall may be adjacent to the heating element 42. The heatable wall may comprise the heating element 42. The heating element 42 may be integral with the heatable wall.

[0029] The receptacle 20 further includes an opening 26 that communicates with the chamber 12. The communication between the opening 26 and the chamber 12 may be direct. The receptacle opening 26 may be flush with the chamber floor.

[0030] The receptacle walls 22 may extend below the chamber floor. The receptacle walls 22 form a recess or receptacle 20 in the chamber floor to allow collection of the liquefied gas 60. The receptacle walls 22 may be integral with the chamber floor.

[0031] The receptacle 20 may be a covered branch pipe or hand hole. As used herein, the terms branch pipe and hand hole may be used interchangeably. The branch pipe may be cylindrical. The branch pipe may form the receptacle wall 22. The branch pipe wall may be a heatable wall. The branch pipe may have an opening 26 opposite its attachment point in the chamber floor. The opening may be directly opposite its attachment point to the chamber floor or the branch pipe opening 26 may be flush with the chamber floor. The branch pipe may extend downward, away from the floor of the sealed chamber 12. The branch pipe may have an end segment with a flange joint 16 surrounding the branch pipe opening 26 on the opposite side from the chamber floor.

[0032] The manifold opening 26 facing the chamber floor can be closed with a manifold cover or lid 40 to form the receptacle floor 24. The cover or lid 40 can be removably attached to the manifold. The manifold cover 40 can have a heatable wall. The manifold cover 40 can include a heating element 42. The heating element 42 can be integrally built into the manifold cover 40. The heating element 42 can be attached to the manifold cover 40.

[0033] In some embodiments, the receptacle 20 may be a channel that extends along part or all of the chamber floor. The channel may be a semicircular channel. The channel floor may be a heatable wall. The channel may also include two side walls and a floor. In this embodiment, the channel floor and / or the channel wall may be a heatable wall.

[0034] The receptacle may be configured to maximize the surface area of ​​the liquefied gas therein, allowing for optimization of the area available for gas-liquid re-evaporation / exchange. The surface area of ​​the liquid within the receptacle may be approximately 10 cm 2 ~about 5000cm 2 , about 50cm 2 ~about 2500cm 2 , about 75cm 2 ~About 1000cm 2 The receptacle may be further configured to minimize the depth of the liquefied gas within the receptacle. The depth of the liquid within the receptacle may range from about 0.1 cm to about 50 cm, from about 1 cm to about 35 cm, or from about 5 cm to about 25 cm.

[0035] The receptacle may have a volume that is less than about 10%, less than about 15%, less than about 20%, or less than about 25% of the total volume of the electrical device.

[0036] A dielectric insulating layer 30 is located between the heatable receptacle wall and the chamber 12. The insulating layer 30 may be a washer. The insulating layer 30 allows for isolating the heatable receptacle wall from the chamber wall. This insulating layer 30 therefore prevents the entire chamber 12 from heating, thereby reducing the energy consumption of the device and effectively heating and re-evaporating only the liquid in the receptacle 20. The insulating layer may be made of polyethylene, polyfluoroethylene, polyamide, polypropylene, polystyrene, polycarbonate, polymethyl methacrylate, polysulfone, polyetherimide, polyetheretherketone, Parylene N™, Nuflon™, silicone, and epoxy resin.

[0037] Preferably, the receptacle 20 is not located in close proximity to an electroactive component, i.e., away from areas with high electrical gradients, to avoid possible discharges. In one embodiment, the receptacle 20 is not located directly underneath an electrical component.

[0038] The heating element 42 is coupled to a power source that operates to supply power to the heating element 42. The power source may be modulatable, i.e., it may modulate the power supplied to the heating element 42. The heating element 42 may be resistively heated, powered by a power source. The power source may be a battery or may be powered by a network.

[0039] In some embodiments, the manifold flange 16 , the insulating layer 30 , and the manifold cover 40 may be held together in place with at least one bolt 50 .

[0040] The receptacle 20 may further be fitted with at least a temperature sensor, a pressure sensor, and / or a liquid sensor. The chamber may include at least a temperature sensor, a pressure sensor, and / or a liquid sensor. The sensors may be coupled to a controller. The controller operates to receive output signals from one or more of the sensors and then modulate power to the heating element 42.

[0041] A temperature sensor may be used to monitor the temperature within the receptacle and / or chamber. The temperature sensor may also monitor the ambient temperature, i.e., the temperature in the vicinity of the device 10. A pressure sensor may be used to monitor the gas pressure within the receptacle and / or gas-insulated switchgear. A liquid sensor may be used to monitor the presence and / or amount of condensed gas collected within the receptacle.

[0042] The operation of the heating means 42 may depend on data read out from temperature, pressure and / or liquid sensors. The heating means 42 may be modulatable.

[0043] In one embodiment, the receptacle 20 can be continuously heated by keeping the heating element 42 continuously on. In another embodiment, the heating element 42 is turned on only when a temperature sensor in the receptacle 20 or chamber 12 drops below a predetermined threshold temperature.

[0044] The predetermined threshold temperature may be about 5° C., 10° C., 15° C., or 20° C. above the gas liquefaction temperature. The threshold temperature depends on the pressure of the gas at which chamber 12 is filled. This can be calculated using the pressure-temperature curve of the gas mixture being filled. The threshold temperature can be less than about -5°C, -10°C, -15°C, -20°C, -25°C, or -30°C.

[0045] The heating element 42 can be turned on when the liquefied gas in the receptacle 20 exceeds a threshold level, as sensed by a liquid sensor.

[0046] The heating element 42 may be turned on when the pressure in the chamber 12 falls below a threshold pressure, which may be calculated using the pressure-temperature curve of the gas mixture being filled.

[0047] The liquefaction temperature of heptafluoroisobutyronitrile depends on the pressure within the device 10. The liquefaction temperature of the gas can be calculated based on its pressure curve. Below the liquefaction temperature, heptafluoroisobutyronitrile condenses from the gas phase. The heptafluoroisobutyronitrile gas may condense on the coldest part of the enclosure, such as the walls of the gas-insulated electrical device 10. The condensate may then flow down the walls of the device 10 and into a receptacle 20, which may be located at the lowest point within the leak-proof chamber 12 of the gas-insulated device 10. The condensate may also be collected via a condensation finger positioned within the chamber 12 above the receptacle 20. The liquefied heptafluoroisobutyronitrile is collected in the receptacle 20 using gravity. The liquefied gas may then be locally heated within the receptacle 20 to re-evaporate.

[0048] In a method for maintaining an insulating gas mixture composition within a medium or high voltage electrical device 10, the method includes collecting liquefied gas in a receptacle 20 and heating the liquefied gas within the receptacle 20 with a heating element 42 when the temperature or gas pressure falls below a threshold temperature or threshold pressure or when the liquid level rises above a threshold level.

[0049] Heating and evaporating the condensate within the receptacle 20 is advantageous because it requires heating a small area. Additionally, because the receptacle 20 is small compared to the sealed chamber 12, the local temperature within it is higher than within the entire apparatus 10. This offsets the endothermic effect of evaporation and provides an additional energy boost for evaporating the condensate. Additionally, as the gases re-evaporate, convection currents that occur during re-evaporation allow for mixing of the gases within the gas mixture in the apparatus 10. This allows the gas composition to remain stable at temperatures below the condensation temperature of the condensable gases.

[0050] At least one of the walls of the recess or receptacle 20 is heated, which allows the heptafluoroisobutyronitrile condensate to re-evaporate.

[0051] Electrical devices 10 that use alternative insulating gases, such as SF, can be retrofitted for use with heptafluoroisobutyronitrile as the insulating gas. In some embodiments, electrical devices containing these alternative gases may be retrofitted to include a receptacle according to the present disclosure. In such retrofitting, the airtight enclosure 12 of the electrical device 10 may be adapted to include a receptacle 20 according to the present disclosure. This may involve fitting an existing structural manifold with an insulating washer 30 and a lid 40 equipped with a heating element 42.

[0052] All features of each aspect of the invention described above may be applied to other aspects of the invention mutatis mutandis. [Explanation of symbols]

[0053] 10 Gas-insulated electrical devices, gas-insulated devices, medium-voltage or high-voltage electrical devices and equipment 12 Sealed chamber, leak-proof chamber, airtight enclosure 16 Flange joints, branch pipe flanges 20 receptacles 22 Receptacle Wall 24 Receptacle Floor 26 Receptacle opening, branch pipe opening 30 Dielectric insulation layer, insulating layer, isolation layer, insulating washer 40 Branch pipe cover, lid 42 Heating elements, heating means 50 volts 60 Liquefied Gas

Claims

1. A medium or high voltage electrical device (10), comprising: A sealed chamber (12), electrical components, a gas mixture ensuring electrical insulation and / or extinguishing of electric arcs generated in said sealed chamber (12), said gas mixture comprising at least one insulating gas and at least one dilution gas; and A receptacle (20), the receptacle (20) comprising an opening (26) and at least one wall (22, 24), the at least one wall (22, 24) being a heatable wall (24), the receptacle (20) being positioned to receive liquefied gas (60); The device (10) further comprises a heating element (42) for heating the heatable receptacle walls (22, 24). Receptacle (20) a sealed chamber (12) comprising: a dielectric thermal insulation layer (30) positioned between the heatable receptacle wall (24) and the sealed chamber (12); Equipped with The receptacle (20) is positioned at the bottom of the sealed chamber (12); the sealed chamber (12) includes a chamber floor, the opening (26) of the receptacle (20) is flush with the chamber floor, and at least one receptacle wall (22, 24) extends below the chamber floor; The receptacle (20) comprises a wall (22) formed from a branch pipe extending below the chamber floor, the branch pipe opening (26) away from the chamber floor comprising a flange (16) and a cover (40); The heating element (42) is disposed in the cover (40); The device (10), wherein the dielectric insulating layer (30) is a washer disposed between the flange (16) and the cover (40).

2. 2. The device (10) of claim 1, wherein at least one wall of the sealed chamber (12) is inclined toward the receptacle (20) to allow liquefied gas (60) to flow into the receptacle (20).

3. The device (10) of claim 1 or 2, wherein the heating element (42) is adjacent to the heatable receptacle wall (22, 24).

4. The device (10) according to any one of claims 1 to 3, wherein the heatable wall (24) comprises a heating element (42).

5. 5. The device (10) of claim 1, further comprising one or more of a temperature sensor for monitoring a temperature within the device (10), a liquid sensor for monitoring a liquid level, and a pressure sensor for monitoring a pressure.

6. The device (10) of any one of claims 1 to 5, wherein the receptacle (20) is positioned remotely from the electrical component.

7. 1. A method for maintaining the composition of an insulating gas mixture in a medium or high voltage electrical device (10), the gas mixture ensuring electrical insulation and / or extinguishing of an electric arc generated in the device (10), the device (10) being as claimed in any one of claims 1 to 6, the device (10) further comprising a temperature, liquid and / or pressure sensor, the method comprising: collecting liquefied gas (60) in a receptacle (20); heating the liquefied gas (60) collected in the receptacle (20) with a heating element (42) when the temperature or pressure falls below a threshold temperature or pressure, or when the liquid level rises above a threshold level; A method comprising:

8. The method of claim 7, wherein the threshold temperature is -5°C, -10°C, -15°C, -20°C, or -25°C.

9. The gas mixture comprises heptafluoroisobutyronitrile, 1,1,1,3,4,4,4-heptafluoro-3-(trifluoromethyl)-2-butanone (CF ３ C(O)CF(CF ３ ) ２ 9. The method of claim 7 or 8, comprising a fluorinated compound selected from the list consisting of: 2,3,3,3-tetrafluoropropene (HFO-1234 yf), 1,3,3,3-tetrafluoropropene (HFO-1234 ze), fluorooxirane, or any combination thereof.

Images