Air-cooled disconnector with cooling slots

Abstract

The invention relates to a high-voltage circuit breaker (1) and a disconnector (2) for operation in the air, extending along an axis (XX '), comprising a housing (3), said disconnector comprising a hollow current conductor (10, 20, 30) in said housing and extending along the axis (XX'), said conductor comprising at least one lower elongated slot (12a, 22a, 32a) and at least one upper elongated slot (11a, 21a, 31a) extending along said axis, each of the slots has a width w and a length l, open airflow cross-section. The ratio between the outer diameter surface of the hollow flow conductor (10, 20, 30) and the total flow cross-section of all notches in the same plane perpendicular to the axis (XX ') is between 70 and 100.

Description

Technical Field

[0001] The present invention relates to the field of air-cooled disconnectors for generator circuit breakers. Background Art

[0002] The generator circuit breaker and corresponding disconnector operate in air and are contained in a closed housing.

[0003] Cooling such devices is important because the high current from the power plant generator flowing through the generator circuit breaker and its attached disconnector generates a lot of heat. This heat must be efficiently transferred to the outside to limit the temperature of the live parts to standard limits. To enhance heat transfer, several methods are used, such as:

[0004] - a heat transfer fluid which moves to the outside in a hot state, cools down, and returns to the inside in a cold state;

[0005] - a fan, which blows air into the housing and increases the heat exchange between the cold housing and the hot electrical components;

[0006] - Natural convection, which transfers heat from hot live components to the cool enclosure via natural fluid movement.

[0007] Natural cooling is promoted by placing cooling fins and cooling holes. The cooling holes are located at several locations all around the disconnector. They have oval, circular, triangular and rectangular shapes. The size, location and shape of such solutions are determined by trial and error. Like other solutions of the prior art, this approach does not take into account the 3D effects of air circulation, skin and proximity effects and temperature-dependent resistivity. By doing so, the prior art design causes current to be concentrated near the cooling holes and / or stagnant areas where there is no air movement, ultimately leading to undesirable local hot spots.

[0008] Knowing the vicious cycle (high temperature leads to increased resistivity, leading to even higher losses and therefore even higher temperatures), these hot spots are a serious risk to the overall performance of the equipment.

[0009] The maximum nominal current of a device is the current that does not cause a temperature above the maximum temperature of the device (i.e., a hot spot). Therefore, the hot spot limits the nominal current, not the overall design. It is of clear interest to the builder to tighten the design to prevent hot spots.

[0010] Furthermore, prior art designs are often found through trial and error to be unreliable because it is impossible to capture all hot spots with a limited number of temperature sensors.

[0011] Specifically, prior art designs do not take into account the effects of air circulation (which may be locally reduced to zero in stagnant areas), nor do they take into account that current may be concentrated at locations close to the holes, resulting in higher current density and further Joule heating at those locations.

[0012] A more efficient solution is needed, both for the disconnector and for the housing. Summary of the invention

[0013] The invention firstly relates to an optimized design of cooling slots in a hollow current-carrying conductor for an air-cooled disconnector.

[0014] The present invention particularly relates to a disconnector for a high-voltage circuit breaker or a high-voltage circuit breaker and a disconnector extending along an axis (XX') (or axial direction), the disconnector comprising a housing and a hollow current-carrying conductor in the housing, the conductor comprising at least one lower elongated slot and at least one upper elongated slot extending along the axis.

[0015] The cutter may include a female component, a tube shell and a movable tube for connecting the female component and the tube shell; the notch may be provided to any of the components, for example, to only one component (such as the tube shell) or to 2 components or to all 3 components.

[0016] The invention also relates to a method for cooling a disconnector or circuit breaker and a disconnector operating in air, extending along an axis (XX'), said disconnector comprising a housing and a hollow current-carrying conductor in said housing, said conductor comprising at least one lower slot and at least one upper slot extending along said axis, in which conductor circulates a current, for example between 10 kA and 30 kA or even up to 50 kA, whereby air circulates from said at least one lower slot to said at least one upper slot.

[0017] In the high voltage disconnector or the circuit breaker and disconnector according to the invention, or in the method according to the invention, each of the notches may have a width between 5 mm and 40 mm, for example 8 mm or 10 mm or 20 mm or 30 mm, the width being measured perpendicularly to the axis (XX') or in a plane perpendicular to the axis (XX').

[0018] Preferably, the maximum nominal current is in the range of 10 kA to 50 kA, for example 30 kA, depending on the configuration of the equipment.Thus, the current during operation of the power device can be set from 0 kA to the maximum nominal current.

[0019] The present invention relates to the cooling of hollow disconnectors, such as disconnectors of the type attached to or attached below a high voltage generator circuit breaker. The disconnector according to one aspect of the invention is operated, insulated and cooled in ambient air. To improve its performance, a natural cooling method is implemented, which does not require expensive cooling fans or cooling circuits using cooling liquids.

[0020] Therefore, the present invention also relates to a method for air cooling a disconnector of a generator circuit breaker, the disconnector comprising an internal hollow portion or a hollow conductor extending along an axis (XX') (or axial direction), the method comprising circulating air through at least one bottom slot, then through said hollow portion inside the disconnector or through said hollow conductor and through at least one upper slot.

[0021] For example, the present invention relates to a method for cooling a disconnector of a generator circuit breaker operating in air, the disconnector comprising an internal hollow portion or a hollow conductor, the method comprising:

[0022] - circulating cold air through a bottom slot preferably located at or close to the lowest possible position of the conductor, then heating up inside the hollow conductor or hollow live conductor, the hot air exiting at a top slot preferably located at or close to the highest possible position of the conductor; the driving force of this natural circulation is the temperature dependence of the air density, which causes an upward movement of the hot air under the effect of gravity;

[0023] - or cool air is circulated through two or more bottom slots preferably located at or close to the lowest possible position of the conductor and then heated inside the hollow conductor or hollow live conductor, with the hot air exiting at two or more top slots preferably located at or close to the highest possible position of the conductor.

[0024] In both cases, the driving force for natural circulation is the temperature dependence of air density, which causes an upward movement of hot air under the effect of gravity.

[0025] In the device or method according to the invention, an air-cooled disconnector is implemented, comprising a hollow current-carrying conductor extending along an axis (XX') (or axial direction), which is provided with at least two cooling slots extending along the axis or in a direction parallel to the axis, the cooling slots preferably being opposite or facing each other, or for example, 2 pairs of cooling slots are provided, the cooling slots preferably being opposite or facing each other.

[0026] Thus, air can flow from the coldest area at the bottom of the housing through the bottom slots in the hollow conductor, heat up and become lighter inside, and then flow out of the conductor through the top slots, and then flow to the ceiling of the housing. At the ceiling of the housing, the hot air of the hollow conductor cools down and flows to the left and right sides of the housing, and finally cools, becomes heavier and denser, and then falls to the bottom of the housing. The cycle can then begin again.

[0027] The invention allows for more efficient natural cooling of the conductors while saving conductive material.

[0028] According to various embodiments of the device or method according to the present invention:

[0029] - the notches preferably have an elongated linear shape, each of the notches may have a length between 20 mm and 400 mm, such as 40 mm or 60 mm or 80 mm or 200 mm, the length being measured along the axial direction or along a direction or axis parallel to the axial direction;

[0030] - and / or any of the top and / or bottom notches may be divided into a number of aligned notches to increase the mechanical strength of the hollow conductor;

[0031] - and / or the hollow conductor has 2 slots at the top and 2 slots at the bottom, the spacing between each pair of cooling slots being, for example, between 10° and 80°, for example, 10° or 30° or 70°;

[0032] - and / or the outer diameter of the hollow current-carrying conductor is between 30 cm and 200 cm;

[0033] - and / or the number of notches at the top and / or at the bottom of the device is at least equal to 1 or 2 or 3 or 4 or equal to n (n<10); for example, the conductor comprises at least 1, 2, 3 or more lower notches and the same or different (e.g. for mechanical reasons) number of upper notches, the lower notches and the upper notches preferably facing each other; - and / or the outer diameter of the hollow current-carrying conductor (e.g. 180.000 mm 2 ) and the sum of the air flow cross-sections of all upper and all lower slots (e.g. 2400mm 2 ) should preferably be comprised in the range of 70 to 100. Outside this range, the cooling notches are inefficient because they either require the removal of too much conductive material (which results in higher current density and therefore higher Joule losses and consequently higher temperatures) or they are too small (very small notches block the natural cooling air circulation, resulting in ineffective cooling and therefore higher temperatures).

[0034] The gas flow cross section of the slot is parallel to XX' of the cutter.

[0035] Preferably, at least one notch has rounded ends at the interior of the conductor, which facilitates the flow of fluid along the interior of the conductor. The skin effect is known to concentrate current at the exterior of the conductor, so this rounded shape should preferably be achieved only at the interior or inner surface of the conductor, where the electrical cross-section reduction is less important.

[0036] In the axial direction (XX'), one or more (preferably all) cooling slots preferably have at least one circular or elliptical end, which allows the current to flow smoothly around the circular or elliptical end without generating current concentration. Preferably, both ends of the one or more or all slots are circular or elliptical.

[0037] According to the invention, different sets of notches can be implemented. Parameters such as width and / or length and / or shape and / or design and / or number of notches and / or radial distribution of notches can vary. Depending on the needs, it is recommended to consider the trade-offs in the case of introducing larger or larger notches:

[0038] - reduced current cross section; the presence of the cooling notches reduces the available current cross section and increases the current density in the remaining conductor, leading to higher Joule losses and, therefore, higher temperatures;

[0039] - Natural convection becomes stronger because air can travel more easily through wider bottom and top slots; wider slots or openings have lower pressure drop and a higher quality cool air flow can enter the hollow cutter and thus cool it more efficiently from the inside.

[0040] Technical solution 1. A high-voltage circuit breaker and disconnector for operating in air, which extends along an axis and includes a housing, the disconnector includes a hollow current-carrying conductor in the housing and extending along the axis, the conductor includes at least one lower elongated slot and at least one upper elongated slot extending along the axis, each of the slots has a width w and a length l, the product of l and w gives the airflow cross-section of the slot, and the ratio between the outer diameter surface of the hollow current-carrying conductor and the total airflow cross-section of all slots is between 70 and 100.

[0041] Technical Solution 2. The high voltage circuit breaker / disconnector according to Technical Solution 1, wherein:

[0042] - the conductor comprises at least 1, 2, 3 or more lower notches and the same or different number of upper notches, the lower notches and the upper notches preferably facing each other,

[0043] - and / or at least one of the upper notch and / or the lower notch is divided into several aligned notches.

[0044] Technical Solution 3. The high-voltage circuit breaker / disconnector according to Technical Solution 2 comprises 2 or more lower notches and 2 or more upper notches:

[0045] - each of the notches in the upper portion is separated from the adjacent notch by an angle between 20° and 60°,

[0046] - and / or each of the notches of the lower notch is separated from an adjacent notch by an angle between 20° and 60°.

[0047] Technical Solution 4. The high-voltage circuit breaker / disconnector according to Technical Solution 3:

[0048] - the notches in the upper notch are separated by an angle of 10°;

[0049] - and / or the notches in said lower notches are separated by an angle of 10°.

[0050] Technical Solution 5. According to the high-voltage circuit breaker / disconnector according to any one of Technical Solutions 1 to 4, the width of each notch is between 5 mm and 40 mm.

[0051] Technical Solution 6. A high-voltage circuit breaker / disconnector according to any one of Technical Solutions 1 to 5, wherein the surface of one or more lower slots through which air flows into the hollow conductor is the same or similar to the surface of one or more upper slots through which air flows out of the hollow conductor within a range of 5%.

[0052] Technical Solution 7. According to the high-voltage circuit breaker / disconnector according to any one of Technical Solutions 1 to 6, the hollow current-carrying conductor has an outer diameter between 30 cm and 200 cm.

[0053] Technical Solution 8. A high-voltage circuit breaker / disconnector according to any one of Technical Solutions 1 to 7, wherein the notch is oriented toward the inner surface of the disconnector.

[0054] Technical Solution 9. A high-voltage circuit breaker / disconnector according to any one of Technical Solutions 1 to 8, wherein at least one of the notches has at least one circular edge at the interior of the hollow conductor in a curved direction from the axis XX'.

[0055] Technical Solution 10. A high-voltage circuit breaker / disconnector according to any one of Technical Solutions 1 to 9, wherein at least one of the notches has at least one circular or elliptical edge at the interior of the hollow conductor in a direction parallel to the axis XX'.

[0056] Technical Solution 11. A high-voltage circuit breaker / disconnector according to any one of Technical Solutions 1 to 10, wherein the casing is filled with air.

[0057] Technical Solution 12. A high-voltage circuit breaker / disconnector according to any one of Technical Solutions 1 to 11, wherein one or more bottom notches and / or upper notches point toward the inner surface at an angle of 5 to 30°.

[0058] Technical Solution 13. A three-phase circuit breaker / disconnector, each phase comprising a high-voltage circuit breaker / disconnector according to any one of Technical Solutions 1 to 12.

[0059] Technical Solution 14. A method for cooling a circuit breaker and a disconnector according to any one of Technical Solutions 1 to 13 operating in air, wherein a current between 10 kA and 50 kA circulates in the conductor, whereby air circulates from the at least one lower slot to the at least one upper slot.

[0060] Technical solution 15. The method according to Technical solution 14, whereby the air is driven by natural convection to circulate from the at least one lower slot to the inner surface of the conductor and then to the at least one upper slot. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] - Figure 1 and Figure 2 An example showing a generator circuit breaker and its disconnector to which the present invention can be applied;

[0062] - Figure 3A and 3B An example of a cutter according to the invention with its different components is shown;

[0063] - Figure 4A and 4B Display includes dual notches ( Figure 4A ) and three notches ( Figure 4B ) of the present invention;

[0064] - Figure 5A and 5B A simplified model of a cutter according to the present invention is shown, comprising a single notch at the bottom and a single notch at the top;

[0065] - Figure 5C , 5D and 5E gives Figure 5A and 5B The calculation results of the simplified model shown in Figure 5C Display temperature graph; Figure 5D displays a cooling air velocity graph; and Figure 5E A current density diagram showing a device according to the present invention;

[0066] - Fig. 6A and 6B A simplified model showing an embodiment of a cutter according to the invention, comprising 3 notches at the bottom and 3 notches at the top;

[0067] - Figure 6C , 6D and 6E gives Fig. 6A and 6B The calculation results of the simplified model shown in Figure 6C Display temperature graph, Fig.6D Displays a cooling air velocity graph, and Fig. 6E A current density diagram showing a device according to the present invention;

[0068] - Fig. 7A The results (in terms of temperature rise) are shown for different notch widths w (measured in the radial cross section of the cutter) for a configuration with one top notch and one bottom notch;

[0069] - Figure 7B Results (in terms of temperature rise) are shown for different numbers of top and bottom notches;

[0070] - Figure 7C The results (in terms of temperature rise) are shown for different angles between the notches (measured in a radial cross section of the cutter);

[0071] - Fig. 8A and 8B A view showing the preferred shape of a single top notch and a single bottom notch in radial cross section of the cutter;

[0072] - Fig. 9A and 9B A view showing a preferred shape of the design including two top notches and two bottom notches in a radial cross section of the cutter;

[0073] - Figures 10A-10E a top or bottom view showing a preferred shape of one or more upper notches;

[0074] - Fig.11 Natural cooling flow through a disconnector according to an embodiment of the present invention and including upper and lower notches oriented relative to the vertical direction is shown. DETAILED DESCRIPTION

[0075] The structure of the device to which the present invention can be applied is Figure 1 and Figure 2 Displayed on.

[0076] It comprises a generator circuit breaker 1 (which can be connected to a busbar via a braided wire 4, which itself can be linked to a generator) and a disconnector 2 (which can be connected to a busbar via a braided wire 4, which itself can be linked to a transformer, such as a step-up transformer), both extending along an axis XX'. The outer diameter of the disconnector casing 30 depends on the rated current and can vary, for example, from 30 cm to 200 cm.

[0077] Both the generator breaker 1 and the disconnector 2 may be supported by an insulator 5 that separates the central live components from a grounded housing or casing 6 .

[0078] The cutter 2 may include three main components, such as Figure 2 . The hollow air-cooled and insulated disconnector has an outer diameter (outer diameter of the tube shell 30) of, for example, between 30 cm and 200 cm, depending on its performance. It may include a female component 10, which can be completely and preferably permanently connected to the generator circuit breaker 1, the movable tube 20 and the tube shell 30. Typically, both components 10 and 30 have almost the same outer diameter. The movable tube 20 can connect the generator to the transformer via axial movement along the axis (XX'). In other words, the hollow movable tube 20 opens and closes the contact with the other fixed side 30 (tube shell). The entire device may also include an earthing switch, a generator starting switch, a current and voltage transformer, and a surge suppressor, which are not shown in the figure. The device is in a housing or casing 3 filled with air. The housing 3 cannot exchange air with the external atmosphere 6; it protects the current-carrying parts (busbars, braided wires, circuit breakers, disconnectors) from environmental influences, keeps the magnetic field inside, and prevents accidental grounding of live parts.

[0079] A current or nominal current between 10 kA and 30 kA or even up to 50 kA can flow in the disconnector. The nominal current is the maximum current that can flow through the device. Currents higher than the nominal current may cause overheating and may damage the equipment. In operation, the current flowing through the circuit breaker and disconnector varies from 0 kA to the nominal current (e.g. 30 kA).

[0080] according to Figure 3A and 3B In the example of a cutter according to the invention shown above, one or more cooling slots 11a, 21a and 31a are located at the top, and one or more cooling slots 12a, 22a and 32a are located at the bottom of the cutter (more precisely, at least one of the components 10, 20, 30 of the cutter, as explained above). Figure 3A As can be seen above, such cooling slots may be present on all three components 10 , 20 and 30 .

[0081] The remainder of this description focuses on notches made in package 30 , but is also applicable to notches that may be made in other components 10 , 20 .

[0082] Preferably, the cooling slot 32 a at the bottom of the component 30 is adjacent to the insulator 5 .

[0083] Each notch preferably extends along (or parallel to) the axis XX'. The effect of such notches will be discussed below. In this application, the "top" (or "upper") and "bottom" (or "lower") parts of the conductor must be understood with reference to the direction of gravity g (e.g. Figure 1 and 11 shown above).

[0084] Figure 3B A cross section of the package 30 is shown. Due to the presence of the insulator 5, the bottom notch 32a and the top notch 31a are slightly offset from each other.

[0085] Figure 4A and 4B A device according to the invention is shown, comprising 2 bottom notches and 2 upper notches ( Figure 4A ) and 3 bottom notches and 3 upper notches ( Figure 4B ). The angle α is the angular spacing between the parallel notches, measured in a plane perpendicular to the axis XX' (or in a radial cross section of the cutter).

[0086] In view of the different computer simulations performed for the disconnector according to the invention and presented below, a simplified model embodiment of the disconnector 2 and its housing 3 is used, as shown in FIG. Figure 5A and 5B It is shown above that the embodiment comprises a ring or hollow tube corresponding to the hollow tubular shell 30 of the cutter in a frame corresponding to the casing 3 (for example, thickness te 12 mm). In all simulations, symmetric boundary conditions were chosen.

[0087] Figure 5A and 5B The simulation results of the model of the embodiment are Figure 5C , 5D ( Figure 5C and 5D Both include temperature and speed scales) and 5E are shown: Figure 5C Display temperature distribution, Figure 5D gives the air velocity distribution, and Figure 5E The current density near the notch is given (the current density is higher around the notch). The simulation model includes one cooling notch 31a at the top of the disconnector and one cooling notch 32a at the bottom of the disconnector.

[0088] Fig. 6A and 6BAnother simplified model of a cutter 2 according to an embodiment of the present invention is shown above, which embodiment includes three cooling slots 31a, 31b and 31c at the top of the cutter and three cooling slots 32a, 32b and 32c at the bottom of the cutter. Figure 6C , 6D 6E shows the simulation results of another simplified model: Figure 6C Given the temperature distribution, especially near the notch, Fig.6D displays the air velocity distribution, and Fig. 6E Shows the current density near the top and bottom notches.

[0089] Regardless of the number of top cooling slots 31a and / or 31b and / or 31c and bottom cooling slots 32a and / or 32b and / or 32c, their positions may be an optimal trade-off between:

[0090] - a reduction in the cross-section for the current flow due to the presence of the notches 31a to 31c and 32a to 32c (this generates more heat due to the higher current density and therefore the stronger Joule effect around the notches);

[0091] - and more efficient natural cooling by convection; but more cooling of the conductors 30 will carry away and transport more heat, which in turn will heat the housing 3 .

[0092] also:

[0093] - better cooling may result in more heat being transferred by the gas close to the casing, which in turn may be heated;

[0094] - and / or more Joule heating close to the cooling slots leads to more heat dissipation, which again may heat up the housing.

[0095] The cutter according to the invention may have, for example:

[0096] - Only 1 cooling slot 31a at the top of the cutter and 2 cooling slots 32a and 32b at the bottom;

[0097] - 2 cooling slots 31a and 31b at the top of the cutter and only 1 cooling slot 32a at the bottom;

[0098] - Only one cooling slot 31a at the top and only one cooling slot 32a at the bottom of the cutter (eg Figure 5A and 5B shown above).

[0099] - 3 cooling slots 31a, 31b and 31c at the top of the cutter and 3 cooling slots 32a, 32b and 32c at the bottom (eg Figure 4B, 6A and 6B).

[0100] - Several top cooling slots and several bottom cooling slots, the number of top and bottom cooling slots can be the same or different; for example, for mechanical reasons, there may be 2 slots at the top (each with a width of, for example, w=10 mm) and 3 slots at the bottom (each with a width of, for example, w=6.67 mm) (for mechanical reasons).

[0101] The notch according to the invention allows saving between 1% and 3% of conductive material (see Fig. 7A , 7B -7C, commented on below), making the conductor 30 (or the corresponding part of the disconnector) lighter.

[0102] More generally, each slot may have a width w (see Figure 5E ), the width w is between 0.2 cm and 4 cm, for example 1 cm, measured perpendicularly to the axis (XX') (see Fig. 7A ).

[0103] The outer diameter surface of the hollow current-carrying conductor 30 and the added slot cross section (which is the width w multiplied by the length l multiplied by the number of all slots (31a and 32a) (see Figure 5E )) is preferably between 70 and 100, more preferably between 80 and 90, more preferably equal to or close to 85. A ratio outside the range of 70 to 100 is not conducive to obtaining the best results (if the ratio is within the range of 70 to 100, a higher temperature rise will occur).

[0104] Best results are obtained if the surface of all lower slots through which air flows is equal or similar (within ±10%, preferably ±5%) to the surface of all upper slots through which air flows.

[0105] In other words, if the sum of all cross-sections through which air passes is referred to as A, and the outer heat transfer surface of the notched conductor is referred to as B, the ratio B / A should preferably be in the range of 70 to 100.

[0106] As is clear from the above, the invention also encompasses a solution in which a single notch is made at the top and a single notch is made at the bottom of the conductor in front of the notch at the top. But tests have shown that this solution with only 2 single notches may lead to excessive concentration of current around the notch and result in increased Joule losses and temperature if the single notch is too large. Therefore, an alternative is:

[0107] - comprising 2 notches made at the top of the conductor and 2 notches made at the bottom of the conductor (preferably in front of the notch at the top) (see Figure 4A and Fig. 9A and 9B ) embodiments;

[0108] - comprising 3 notches made at the top of the conductor and 3 notches made at the bottom of the conductor (preferably in front of the notches at the top) (see Figure 4B , 6A and 6B) embodiments.

[0109] According to one aspect of the invention, air flows by convection from the bottom of the housing, through the bottom slot 32a, up through the conductor, and then through the upper slot 31a. The invention provides efficient natural cooling of the conductor while saving material. However, the housing is heated by the heat transferred by the airflow, so attention must also be paid to the temperature of the housing.

[0110] Only one phase is discussed above, but the present application is applicable to a 3-phase circuit breaker / disconnector, each phase having a structure according to the present invention.

[0111] The invention may be applied, for example, to circuit breakers in which very high nominal currents (eg 10 kA and 50 kA) circulate and / or in which voltages range from 10 kV to 40 kV.

[0112] Now combine Figure 8A-11 Describing another aspect of the invention:

[0113] - Fig. 8A and 8B A cross section in the radial direction of a cutter is shown, the cutter having a configuration of one top notch and one bottom notch. Fig. 8A An enlarged view of the upper notch 31 a and the rounded edge 34 a at the interior surface 33 of the hollow conductor 30 is shown. Figure 8B Magnified views showing the lower notch 32a and the rounded edge 35a at the inner surface 33 of the hollow conductor 30; the arrows in these views show the fluid flow along the inner surface 33: it is clear that the rounded edges 34a and 35a at the inner part of the hollow conductor facilitate this fluid flow; since the skin effect concentrates the current at the outer part of the conductor, it is preferred to perform shape optimization only at the inner part of the conductor to achieve a smoother fluid flow, where reducing the electrical cross section is not so important;

[0114] - Fig. 9A and 9B A cross section in the radial direction of the cutter is shown, which has an arrangement of two top notches 31a and 31b and two bottom notches 32a and 32b. Fig. 9AAn enlarged view showing the upper notches 31a and 31b and the rounded edges 34a and 34b at the interior of the hollow conductor 33. The rounding on the interior allows for smooth fluid flow and low pressure drop around the corners. Fig. 9B An enlarged view showing the lower notches 32a and 32b and the rounded edges 35a and 35b at the interior of the hollow conductor 30. The notches and therefore the cooling air are directed towards the hot conductor surface; the same effect as above is achieved in favouring the fluid flow along the surface 33; preferably the rounded edges 35a, 35b are formed only on the side 33 along which the fluid should flow. The rounded edges 35a and 35b have a positive diffusion effect, resulting in a lower pressure drop and therefore making it easier for the air to pass through the notches;

[0115] - Figures 10A-10E Several cooling slot configurations are shown according to embodiments of the invention, all slots 31a-31c having rounded ends 36. All 5 figures show a view from the top of the housing to the cutter, but similar configurations apply to the bottom slots 32a-32c. Fig. 10A (respectively 10C or 10D) showing 1 (respectively 2 or 3) notches 31a (respectively 31a and 31b or 31a, 31b and 31c) symmetrically positioned with respect to a vertical plane including the axis XX' of the hollow tube; Fig. 10E A configuration including two double notches 31a, 31b, a single notch 31c, and another double notch 31d and 31e is shown. In all configurations, the rounded end 36 allows for a smooth current path without local current concentration. Fig. 10B As shown above, a single cooling slot can also be divided into two or more aligned cooling slots, which can have rounded and / or oval ends 36, with the same beneficial effect on the temperature rise. For reasons of mechanical stability, the top and bottom slots 31a1, 31a2 (see Fig. 10B ) can be divided into 2, 3 or even more (e.g. 10) slots aligned along the axial direction, such as in Fig. 10B As in the example shown above, where the notches are aligned but split into two notches, the small bridge of conductive material between them greatly increases the strength and rigidity of the entire conductor structure.

[0116] The invention realizes natural convection of a natural fluid, which flows from hot live parts to a cold housing and takes away heat. For high constant currents, for example in the range of 10 to 30 kA, natural cooling is sufficient to keep the temperature of live parts below the limit. No additional cooling devices such as fans or heat pipes are required. Improving and optimizing natural convection helps to cool the equipment more efficiently and allows the user to obtain even higher nominal currents with the same product afterwards without additional investment.

[0117] The present invention relates to optimized cooling of specialized equipment for air-insulated generator circuit breakers and disconnectors located within a housing. Through in-depth analysis of the positioning, shape and size of cooling slots, performance is significantly improved while at the same time saving conductive material.

[0118] The inventors of the present invention simulated different configurations and derived different features of the cooling slots to reduce the temperature rise while saving conductive material. These features are the design and / or location and / or shape and / or width and / or length of the cooling slots.

[0119] like Figure 5A and 5B In the arrangement shown above, in which only one notch at the top and one notch at the bottom are included, the two notches preferably face each other. In the arrangement comprising multiple notches at the top and / or multiple notches at the bottom, a symmetrical design should be preferred, see for example Figure 4A and 4B . Figure 4A and 4B The angle shown in should be kept above 10° and below 80° (see Figure 7C ).

[0120] like Fig.11 As shown above, the notches (in this example, 2 bottom notches and 2 upper notches) are preferably oriented differently to obtain better results:

[0121] - on the underside, the slots 32a and 32b are preferably spaced apart from each other (from the outside to the inside of the conductor 30) and oriented so that the cold cooling air flow can be directed toward or along the hot inner disconnector surface 33; in fact, the cold air coming in through the slots has considerable kinetic energy, which is used to efficiently exchange heat with the inner surface of the disconnector. The slots can be directed toward the inner surface at an angle β ranging from 5 to 30 degrees from the vertical;

[0122] - On the upper side, the notches 31a and 31b preferably converge towards each other (from the inside to the outside of the conductor 30) and are preferably oriented so as to provide as little resistance as possible to the heated gas flow leaving the hollow interior of the disconnector. The notches are thus directed so that the gas flow requires the least amount of turning. The notches may be directed towards the inner surface at an angle β in the range of 5 to 30° from the vertical.

[0123] Figures 7A-7C The temperature rise is shown for different design parameters and / or different devices (having different diameters), different slot widths, and / or different numbers of slots, and / or different angles between adjacent slots.

[0124] Fig. 7AThe upper portion shows the maximum temperature rise for devices having the same diameter and geometry. The maximum temperature rise is indicated at the top of each graph and varies between 70.3 Kelvin and 72.9 Kelvin.

[0125] The 1st device (on the left, temperature rise 72.9 Kelvin) has no notch, and each of the other devices has 1 notch at the top and 1 notch at the bottom, with different widths of 5mm, 10mm, 15mm, 20mm, 30mm, 40mm (from left to right).

[0126] Fig. 7A The lower part shows the Fig. 7A Material consumption of the same device arranged in the same order in the upper part, starting from the left, the device has no notch (100% material). Integrating or adding increasingly wider notches results in lower conductive material consumption.

[0127] Figure 7B The upper part of the graph shows the maximum temperature rise for different numbers of slots and the same device diameter and the same gas flow cross section (except for device 1, which has no slots and therefore a cross section of 0). The maximum temperature rise is indicated at the top of each graph and varies between 69.8 Kelvin and 72.9 Kelvin.

[0128] The first device (on the left, maximum temperature rise 72.9 Kelvin) has no notches; the next device on the right has 1 notch at the top and 1 notch at the bottom (maximum temperature rise of the device 70.3 Kelvin, each notch has a width of 20 mm); the next device on the right has 2 notches at the top and 2 notches at the bottom (maximum temperature rise of the device 70.0 Kelvin, each notch has a width of 10 mm); and the last device on the right has 3 notches at the top and 3 notches at the bottom (maximum temperature rise of the device 69.8 Kelvin, each notch has a width of 6.7 mm).

[0129] Figure 7B The lower part shows the Figure 7B Material consumption of the same devices arranged in the same order as above, starting from the left, the device has no notch (100% material), the other 3 devices consume the same amount of aluminum (98.6%), and all 4 devices have the same outer diameter.

[0130] Figure 7C The upper part of shows the maximum temperature rise for different angles α between adjacent notches for the same device diameter. The maximum temperature rise is indicated on the top of each graph and varies between 69.8 Kelvin and 72.9 Kelvin.

[0131] The first device (on the left, maximum temperature rise 72.9 Kelvin) has no notches. The other devices have 2 notches at the top and 2 notches at the bottom, and are separated by angles of 10° (device with maximum temperature rise 70.0 Kelvin), 20° (device with maximum temperature rise 69.8 Kelvin), 30° (device with maximum temperature rise 69.9 Kelvin), 40° (device with maximum temperature rise 69.8 Kelvin), 60° (device with maximum temperature rise 69.9 Kelvin), 80° (device with maximum temperature rise 70.2 Kelvin), 100° (device with maximum temperature rise 70.7 Kelvin), respectively.

[0132] Preferably, the angle α between adjacent notches is between 20° and 60°.

[0133] Figure 7C The lower part shows the Figure 7C Material consumption of the same devices arranged in the same order in the upper part, starting from the left, the device without notches (100% material) and the other devices consuming the same amount of aluminum (98.6%).

[0134] Figures 7A-7C It is shown that the invention allows to reduce the temperature rise by a few Kelvin, for example from 72.9 Kelvin to 69.8 Kelvin, a temperature reduction of more than 4%, while saving 1.4% of conducting material. This allows higher current circulation: it is estimated that the heating is reduced by 4% (due to the presence of the notch), so it is possible to increase the rated current by about 4%, while still limiting the temperature rise to 75 Kelvin. For example, a device with a maximum current of 20 kA (without notch) can be used for currents up to 20.8 kA with the cooling notch according to the invention.

[0135] Keeping the maximum temperature rise of the conductors below 75 Kelvin allows saving on cooling fans that would otherwise have to be implemented around the conductors.

[0136] The invention allows reducing the maximum temperature or hot spot temperature, which allows optimizing the installation and achieving higher nominal currents without increasing the conducting cross section.

Claims

1. A high-voltage circuit breaker and disconnector for operation in air, extending along an axis (XX'), comprising a housing (3), said disconnector comprising a hollow current-carrying conductor (10, 20, 30) in said housing and extending along the axis (XX'), said conductor comprising at least one lower elongated slot (12a, 22a, 32a) and at least one upper elongated slot (11a, 21a, 31a) extending along said axis, each of said slots having a width w and a length l, the product of l and w giving the gas flow cross section of said slot, the ratio between the outer diameter surface of said hollow current-carrying conductor (10, 20, 30) and the total gas flow cross section of all slots being between 70 and 100.

2. A high voltage circuit breaker / disconnector according to claim 1, whereby: - the conductor comprises at least 1, 2, 3 or more lower notches (12b, 22b, 32b) and the same or different number of upper notches (11a, 21a, 31a), the lower notches and the upper notches preferably facing each other, - and / or at least one of the upper notch and / or the lower notch is divided into a plurality of aligned notches (31a1, 31a2).

3. The high voltage circuit breaker / disconnector according to claim 2, comprising 2 or more lower notches (12a, 12b, 22a, 22b, 32a, 32b) and 2 or more upper notches (11a, 11b, 21a, 21b, 31a, 31b): - each of the notches of the upper part (11a, 21a, 31a) is separated from the adjacent notch (11b, 21b, 31b) by an angle between 20° and 60°, - and / or each of the slots of the lower slots (12a, 22a, 32b) is separated from an adjacent slot (12b, 22b, 32b) by an angle between 20° and 60°.

4. The high voltage circuit breaker / disconnector according to claim 3: - the notches in the upper notches (11a, 21a, 31a) are separated by an angle of 10°; - and / or the notches in said lower notches (12a, 22a, 32a) are separated by an angle of 10°.

5. The high voltage circuit breaker / disconnector according to any one of claims 1 to 4, the width of each notch (11a-11c, 12a-12c, 21a-21c, 22a-22c, 31a-31c, 32a-32c) being between 5 mm and 40 mm.

6. The high voltage circuit breaker / disconnector according to any one of claims 1 to 5, wherein: The surface of the one or more lower slots through which air flows into the hollow conductor (12a, 22a, 32a) is the same or similar to the surface of the one or more upper slots through which air flows out of the hollow conductor (11a, 21a, 31a) within 5%.

7. A high voltage circuit breaker / disconnector according to any one of claims 1 to 6, said hollow current carrying conductor having an outer diameter of between 30 cm and 200 cm.

8. The high voltage circuit breaker / disconnector according to any one of claims 1 to 7, wherein: The notch is oriented toward an inner surface (33) of the cutter.

9. The high voltage circuit breaker / disconnector according to any one of claims 1 to 8, wherein: At least one of the notches has at least one rounded edge (34a, 35a, 34b, 35b) at the interior of the hollow conductor in a curvilinear direction from the axis XX'.

10. The high voltage circuit breaker / disconnector according to any one of claims 1 to 9, wherein: At least one of the notches has at least one circular or elliptical edge (36) at the interior of the hollow conductor in a direction parallel to the axis XX'.

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