METHOD FOR INCREASING THE DIELECTRIC STRENGTH INSIDE AN ELECTRICAL SWITCHGEAR

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for increasing the dielectric strength inside the enclosure of an electrical device, this method consisting of placing inside said enclosure a dielectric material in liquid or solid form, and then bringing this material to a temperature and / or pressure allowing its total or partial evaporation inside the enclosure.

[0002] The present invention also relates to an electrical device, in particular a medium or high voltage electrical protection device, comprising a chamber filled with a dielectric material in solid or liquid state, said chamber being able to be opened so as to allow the introduction of said material, then to be closed and sealed so as to allow the evaporation of this material, then the containment of the resulting gases inside said chamber. STATE OF PRIOR ART

[0003] It is increasingly common in the field of medium or high voltage electrical devices, such as medium voltage circuit breakers, to seek to improve the dielectric performance of these devices intended to be filled with ambient air, dry air or a neutral gas.

[0004] A known solution is to replace air with high-performance gases such as SF6 or Fluoroketone (C5FK). Indeed, at equivalent pressure, the dielectric strength of air is between 2.5 and 3 times lower than that of SF6. These gases are always introduced in gaseous form.

[0005] Another solution is to significantly increase the pressure of the air or neutral gas.

[0006] Another solution is to use insulating liquids in the form of oil.

[0007] However, replacing air with so-called high-performance gases generates significant design constraints (need to use valves, pressure gauges, etc.) and induces highly complex industrial processes (use of gas cylinders, vacuum processes, etc.) which are best avoided whenever possible.

[0008] Indeed, the use of fluoroketone (C5FK) requires the implementation of a complex filling process. After sealing the tank, its contents are evacuated, then the C5FK is filled, and finally an inert gas is added until a given pressure is reached, which requires a pressure gauge and a valve.

[0009] Thus, when implementing such processes, the device is filled with gas after a vacuum has been obtained.

[0010] In addition to the above, there is increasing effort to move away from the use of SF6 gas, given the supposed impact of this gas on the phenomenon of global warming, its global warming potential (GWP) being 22800 times greater than that of CO2, making it the gas with the strongest impact on the greenhouse effect.

[0011] As for the handling of fluoroketone in liquid form in an open filling process, this should be avoided given the risks of liquid spillage by operators in the factory and gas vaporization in the workshops.

[0012] We are familiar with document WO 2012 / 080269 A1 describing a process for mixing a dielectric gas with a carrier gas in a chamber of an electrical device.

[0013] We also know of document FR2980631 A1 describing a process according to the preamble of claim 1.

[0014] We also know of document EP 2 904 617 A1 describing an enclosure of electrical equipment filled with a gas comprising an organofluorinated compound and equipped with a molecular sieve.

[0015] The present invention solves or mitigates these problems and proposes a method for improving the dielectric strength inside the enclosure of an electrical device, this method being easily implemented without significant implementation constraints and limiting to a minimum the exposure of operators to gas vapors. DESCRIPTION OF THE INVENTION

[0016] To this end, the invention proposes a method according to claim 1.

[0017] According to a particular characteristic, the aforementioned evaporation is accelerated by heating the material to a certain temperature, this temperature being higher than the ambient temperature or between a temperature attainable in an industrial environment and the ambient temperature.

[0018] The main advantage of a temperature higher than ambient temperature lies in the acceleration of the evaporation process.

[0019] Depending on a particular characteristic, the aforementioned enclosure, before the container is placed inside, is filled exclusively or not exclusively with ambient air, dry air, or a neutral gas.

[0020] According to another embodiment, a vacuum is created inside said enclosure, then it is filled exclusively or not exclusively with a pure gas or a mixture containing N2, CO2, or O2 before the container is put in place or after the container is put in place or after the container is put in place. DESCRIPTION OF SEVERAL EMBODIMENT METHODS ACCORDING TO THE INVENTION.

[0021] However, other advantages and features of the invention will become clearer in the detailed description that follows and refers to the accompanying drawings, which are given solely by way of example and in which: THE figures 1 to 3 are schematic representations illustrating the process in principle, according to three different implementations shown respectively on the figures 1a, 1b and 1c only the figure 1c corresponds to the invention. The figures 4 to 7 illustrate the different stages of a process according to a particular embodiment not forming part of the invention, The figures 8 , 9 And 10 schematically illustrate three other embodiments of the process not covered by the invention, and The Fig. 8a , Fig. 8b Fig. 8c, Fig. 9a, Fig. 9b And Fig. 10a, Fig. 10b correspond respectively to the different stages of these three achievements.

[0022] On the figures 1 to 3, is illustrated a method according to the invention allowing to improve the dielectric strength inside an enclosure E belonging to a medium or high voltage electrical device, such as a medium voltage circuit breaker, this enclosure being, in this particular embodiment, previously filled with air.

[0023] The first step in this process involves obtaining an open container 1 that allows for the filling of a dielectric material 2 in solid or liquid form; this container can be left open, as illustrated in the fig.1a , which can be closed and sealed as illustrated on the figure 1b , or, according to the invention, be adapted to receive a porous substrate such as a sponge 3, said substrate being filled with a dielectric liquid.

[0024] A second step in this process is illustrated on the figure 2, consists of introducing this container 1 inside the enclosure E of the device at room temperature or at a temperature lower than room temperature in an air-conditioned room, these temperatures being lower than the boiling point of the liquid.

[0025] According to a third step described on the figure 3 , enclosure E is closed and sealed, and liquid evaporation can occur; heating the enclosure above ambient temperature can accelerate the evaporation phenomenon.

[0026] The gas vapors released during this evaporation mix with the air, which increases the dielectric performance of the device.

[0027] According to a second embodiment not covered by the invention illustrated in the figures 4 to 7 , the aforementioned enclosure E comprises a lower part 4 and an upper part 5, these two parts each supporting electrical conductors 6.

[0028] This lower part 4 has a housing 7 intended to receive a bag 8, which bag is intended to contain a dielectric liquid.

[0029] On the figure 4 , enclosure E is in the open position which allowed the introduction of the aforementioned bag 8.

[0030] The upper part 5 has a needle-shaped portion 9 adapted to pierce the aforementioned bag 8 when the enclosure E is closed, a step illustrated in the figure 5 .

[0031] Thus, this perforation can be made either when closing the enclosure E, or by providing a specific shape on the movable part 5 of the enclosure E, this specific shape being able to perforate the container 1 by the actuation of a mechanical control (not shown) provided in the enclosure.

[0032] On the figure 6 , enclosure E is closed and allows the release of gas vapors.

[0033] On the figure 7After a certain time, depending on the temperature, the dielectric material is totally or partially in a gaseous state. The device is then ready for use.

[0034] The following passages of the text corresponding to figures 8 to 10 represent examples that are not part of the invention.

[0035] According to another embodiment illustrated on the figure 8 , the container 1 and the enclosure E are connected to each other by a connection zone z, communication between the two being prevented by the fact that the container 1 is closed by a sheet 10 made of a material such as aluminium, this sheet being able to be perforated by the actuation of a mechanical means provided for this purpose in the enclosure E causing the movement of the elements forming needle 11, so as to establish communication between the enclosure and the container.

[0036] Thus, on the figure 8aCommunication is prevented by the presence of this sheet 10. The enclosure E has a valve 13 at its upper part, intended for venting the enclosure before filling with gas N2, for example. On the figure 8b Communication is being established through the performance of this sheet 10.

[0037] On the figure 9 , the connection zone z includes a valve 12 suitable for establishing the connection between the container 1 and the enclosure E when the latter are joined together.

[0038] Thus, on the figure 9a , valve 12 is in the open state, while on the figure 9b , valve 12 is in the closed state.

[0039] On the Figure 10 , the connection zone z has two valves 12 and 14 suitable for establishing the connection between the container 1 and the enclosure E when the latter are joined together.

[0040] Thus, on the figure 10a, valves 12 and 14 are in the closed state, while on the figure 10b , valves 12 and 14 are in the open state after the connection between enclosure E and container 1.

[0041] In all these designs, the use of a heating process in the cell accelerates evaporation.

[0042] These gas vapors g mixed with the air present in enclosure E, exhibit a dielectric strength greater than that of pure air, at the same pressure.

[0043] For example, 0.060 bars at 20°C of Fluoroketone C6FK provides the same dielectric performance as approximately 0.300 bars of SF6.

[0044] Thus, there is no need to place a large quantity of Fluoroketon C6FK, for example, to significantly improve the dielectric strength of a medium or high voltage device.

[0045] Thus, since this dielectric material is liquid at room temperature (for example, with a boiling point of 49°C in the case of C6FK), it can be handled in a liquid state rather than a gaseous one, which is very useful from an industrial perspective. With this quantity and considering the saturated vapor pressure curve, it is possible to guarantee both that this liquid will evaporate completely in the tank in which it is placed and that the material will remain liquid from the highest operating temperatures down to 15°C. Of course, this lower value can be adjusted by modifying the partial pressure of the material or by selecting a different material.

[0046] For a cell volume of 30 litres, it is necessary to supply approximately 15mL of C6FK liquid to reach the previously mentioned pressure.

[0047] Other dielectric materials may be used besides that described above, these materials preferably having the following properties: A global warming potential (GWP) of less than 3000. A boiling point below 60°C. A toxicity (TWA) greater than 50 ppm. Classification of the material as non-flammable.

[0048] The list below enumerates different possible families of chemical substances, which could be used advantageously: Hydrofluoroethers (HFE). Hydrofluoroolefins (HFO) Fluoroketones.

[0049] The implementation of the process of the invention according to the embodiment described above, in which the porous substrate is a sponge, which is broadly defined as a porous substrate, could be as follows: The chemical manufacturer (or a subcontractor specializing in chemical packaging) supplies a sponge containing the exact quantity of insulating liquid required for a given device. To prevent any vaporization during transport and storage, this sponge is packaged in a sealed container or bag.

[0050] During the assembly phase, users open the bag and place the sponge inside the cell just before sealing it. Because the boiling point of this insulating fluid is high, vaporization is very slow, giving the user ample time to close the enclosure. Advantageously, the boiling point could be between 0 and 60°C.

[0051] According to another embodiment not part of the invention, the container is a sealed package or bag that contains the exact amount of liquid needed to fill the tank. During the assembly phase, this sealed package or bag is placed in a specific location inside the tank, and when the lid for closing the tank is put in place, an element of this lid punctures the sealed package or bag, causing the release of liquid vapors.

[0052] According to the invention, a process has been developed to increase the dielectric strength of air or other neutral gas introduced into the enclosure (in a pressurized state or at atmospheric pressure or below atmospheric pressure) in a sealed enclosure belonging to a medium or high voltage electrical device, using an additional cartridge which must be placed in the cell before the enclosure is sealed.

[0053] This implementation method is particularly simple and inexpensive, avoiding any complex handling such as vacuuming, the use of valves and other injection and evacuation processes.

[0054] Thanks to this latest method (airtight packaging or bag), the user no longer has any contact with the liquid during assembly or in the event of uncontrolled vaporization. There is no time constraint between placing the container in the chamber, sealing the chamber, and opening the container.

[0055] The invention therefore offers a technical solution for easily depositing the insulating material inside the device.

[0056] According to the invention, when the container is a sponge, for example, the user does not have to handle the fluorinated liquid, which previously required precision, precautions, and the management and storage of the bottles. The user simply needs to handle the sponges while wearing gloves, as handling sponges is easier than handling a liquid.

[0057] The solution, not covered by the invention, of using a container suitable for perforation is the safest from the point of view of user safety, because the latter is never in contact with the fluid and its vapors.

[0058] The invention is advantageously applicable to any electrical device comprising a housing having a dielectric function.

[0059] The invention is particularly applicable to any medium voltage electrical protection device such as a circuit breaker, a switch, a busbar, etc.

Claims

1. Method for increasing the dielectric strength of ambient air, dry air or a neutral gas present inside the enclosure of an electrical unit, this method consisting in placing a dielectric material inside said enclosure, this dielectric material being placed inside said enclosure in liquid form, then being brought to a temperature and / or a pressure allowing the total or partial evaporation thereof inside the enclosure, characterized in that said material (2) is retained inside its container (1) during the handling allowing said container (1) to be put in place in the enclosure E, by virtue of means comprising an absorbent substrate (3) filled with the dielectric liquid and a sealed packaging that is able to transport said substrate and from which said substrate can be removed before being placed in the enclosure just before said enclosure is closed, then the evaporation of this material (2) is caused at a certain moment after this putting in place in the enclosure E so as to allow the dispersion of the gases g resulting from this evaporation inside the enclosure E.

2. Method according to Claim 1, characterized in that the abovementioned evaporation is accelerated by the heating of the material (2) to a certain temperature, this temperature being higher than the ambient temperature or else between a temperature T0 that can be reached in an industrial environment and the ambient temperature.

3. Method according to Claim 1 or 2, characterized in that the abovementioned enclosure E, before the container (1) is put in place, is filled at least partly with ambient air (a), dry air or else a neutral gas.

4. Method according to either one of Claims 1 and 2, characterized in that a vacuum is created inside said enclosure E, then it is filled at least partly with a pure gas or a mixture containing N2, CO2, or O2 before the container is put in place or else after the container is put in place.