Patent Grant
9437380
The present invention relates to switching units or switching gear and more particularly to cooling of a switching unit or switching gear which is solid-insulated with insulating resin.
Switching gear is installed as a power reception/distribution device in a power system to receive generated power from a power plant and distribute it to a load. A switching unit is installed in switching gear and is a key part of the switching gear which houses a switch.
Recently, in urban areas there has been a problem that power consumption concentrates in certain regions and construction of distributing substations in response to the growing demand for power consumption is difficult and there is shortage of space for installation of power distributing pipes. In addition, the demand for higher operating rates of supply facilities is growing. In order to respond to the demand, studies have been conducted on the construction of efficient power supply facilities which encourage a high voltage system to absorb loads by boosting the distribution voltage, namely increasing the capacity per line. To this end, distributing implements and substation equipment for the high voltage system must be more compact.
Also, since the inside of the switching gear is hot mainly in the current conduction area when a large current flows, the cooling performance must be improved for a large current to flow. An example of switching gear with a function to improve the cooling performance as mentioned above is described in Patent Literature 1. Patent Literature 1 describes that cooling performance is improved by providing resin or metal fins on the resin layer covering the switching gear.
Patent Literature 1: Japanese Patent Application Laid-Open No. 2001-160342
However, according to Patent Literature 1, the connected fin bottoms form a rectangle in a plan view, but the vacuum valve formed inside the resin layer is cylindrical and the positions of the fin bottoms and the inner shape of the resin layer are not correlated. If the fins are made of resin, since resin is lower in thermal conductivity than metal and a temperature distribution occurs, simply using fins to a large extent is hardly expected to improve the heat radiation effect dramatically. On the other hand, since switching gear is installed in a confined space, an increase in its size is undesirable.
Therefore, the present invention has an object to provide a switching unit or switching gear which enhances heat radiation performance and eliminates the need for an increase in the size.
In order to solve the above problem, the switching unit according to the present invention includes: a switch which includes a fixed electrode, a movable electrode facing the fixed electrode and moving in the axial direction to contact or leave the fixed electrode, a bus side conductor connected to one of the electrodes and connected to a bus, and a load side conductor connected to the other electrode and connected to a load; and insulating resin located in a way to cover the periphery of the switch, in which the insulating resin has fins formed in a circumferential direction on an outer surface of the insulating resin and the distance between the periphery of the switch and the bottoms of the fins is almost constant in the circumferential direction.
According to the present invention, it is possible to provide a switching unit or switching gear which enhances heat radiation performance and eliminates the need for an increase in the size.
Next, the preferred embodiments of the present invention will be described. The embodiments described below are just examples and obviously the invention is not limited to the embodiments described below.
Next, the first embodiment will be described referring to
As shown in
The vacuum valve 26 has, in a vacuum container 8 constituted by connecting a fixed side ceramics insulating cylinder 29, movable side ceramics insulating cylinder 30, fixed side end plate 31 and movable side end plate 32: a fixed side electrode 16; a movable side electrode 17; a fixed side conductor 5 connected to the fixed side electrode 16; a movable side conductor 6 connected to the movable side electrode 16, a movable side conductor 6 connected to the movable side electrode 17; and an arc shield 25 for protecting the ceramic insulating cylinders 29 and 30 from arcs during electrode opening/closing operation. The fixed side conductor 5 is connected to a cable bushing center conductor 15 to supply power to the load. The cable bushing center conductor 15 is located perpendicularly to the fixed side conductor 5 and conductors concentrate in the area between the cable bushing center conductor 15 and fixed side conductor 5, so the temperature easily rises in the area during use. Thus, in the area around an intersection where a plurality of conductors gather, heat generation density increases and heat accumulates during use. In addition, a bellows 22 is located on the movable side to enable movement of the movable side conductor 6 while keeping the vacuum condition inside the vacuum valve 26. The vacuum valve 26 keeps the vacuum inside it through the bellows 22 connected to the movable side end plate 32 and movable side conductor 6 and enables the movable side electrode 17 and movable side conductor 6 to move in the axial direction to perform switching between the On and Off states. A bellows shield 33 is located near the joint between the bellows 22 and movable side conductor 6 to protect the bellows 22 from arcs, etc. during switching operation and also can alleviate concentration of electric fields at the ends of the bellows 22. The movable side conductor 6 is connected to an aerial-insulated and solid-insulated actuating rod 18 for the vacuum valve 26, and the vacuum valve actuating rod 18 is connected to an actuator (not shown). A fixed side field alleviating shield 34 is located around the fixed side ceramics insulating cylinder 29 to alleviate concentration of electric fields at the joint with the fixed side end plate 31 and a movable side field alleviating shield 35 is located around the movable side ceramics insulating cylinder 30 to alleviate concentration of electric fields at the joint with the movable side end plate 32.
The grounding disconnection part 27, connected to a bus bushing center conductor 14, includes a bushing fixed electrode 3 connected to the bus through this center conductor, a grounding side fixed electrode (guide) 19 as ground potential, and a middle fixed electrode located at the axial midpoint between them and electrically connected to the movable side conductor 6 on the vacuum valve 26 side through a flexible conductor 20, and its inside is aerially insulated. These fixed electrodes have the same inside diameter and are arranged in line. When a grounding disconnection part movable conductor 4 linearly moves in the grounding disconnection part 27 with respect to these fixed electrodes, switching to three switching positions, namely positions for making the circuit, breaking the circuit, and grounding, can be made. The grounding disconnection part movable conductor 4 is coupled to an aerial-insulated and solid-insulated actuating rod 12 and can move through an operating mechanism (not shown). Since the portion of the grounding disconnection part movable conductor 4 which is to contact the above fixed contacts is a spring contact 10, it can contact them reliably without hindering movement of the grounding disconnection part movable conductor 4, due to its elastic force.
The bus bushing 13 is formed by covering the periphery of the bus bushing center conductor 14 with the insulating resin 2 and the cable bushing 28 is formed by covering the periphery of the cable bushing center conductor 15 with the insulating resin 2.
As material for the actuating rod 12 for the vacuum valve, the actuating rod 18 for the grounding disconnection part and the insulating resin 2, epoxy resin is used in consideration of insulation properties and mechanical strength and because of high formability. Also, the actuating rods 12 and 18 and the insulating resin 2 are solid-insulated by themselves and aerial-insulated by the ambient gas.
The grounding disconnection part movable conductor 4, fixed side conductor 5, movable side conductor 6, air area 7 and vacuum container 8 are integrally cast with the insulating resin 2 and resin radiating fins 1 of the same material as the insulating resin 2 are provided on the outer surface of the insulating resin 2 covering the grounding disconnection part movable conductor 4, fixed side conductor 5, and movable side conductor 6. As shown in
Furthermore, in this embodiment, as shown in
Next, how the switching unit according to this embodiment is used will be described. When the switching unit is connected to the power system, power is supplied into the switching unit from the bus and if the grounding disconnection part 27 is in the closed position and the vacuum switch is turned on, power is supplied from the power system through the bus to the load in the following order: the bus bushing center conductor 14 to the bushing fixed electrode 3 to the spring contact 10 to the grounding disconnection part movable conductor 4 to the spring contact 10 to the middle fixed electrode 9 to the flexible conductor 20 to the movable side conductor 6 to the movable side electrode 17 to the fixed side electrode 16 to the fixed side conductor 5 to the cable bushing center conductor 15 via the cable. In this case, the above current conduction areas generate Joule heat depending on the resistance value. When high voltage is applied as in switching gear, the amount of generated heat is very large and consideration of heat radiation performance is indispensable in the manufacture of a device.
The Joule heat generated at various parts with the power on is large at the area of contact between the bushing fixed electrode 3 and the grounding disconnection part movable conductor 4 through the spring contact 10 and at the area of contact between the movable side electrode 17 and the fixed side electrode 16; and also near these areas, particularly near the area where the fixed side conductor 5 and vacuum container end are fixed, there is an environment in which radiated heat easily accumulates locally. Also since the temperatures of the grounding disconnection part movable conductor 4, fixed side conductor 5 and movable side conductor 6 as conductors in the switch rise, emission of thermal electrons is accelerated with rise in the temperatures, resulting in deterioration in insulation performance. A possible approach to preventing temperature rise is to suppress heat generation and a concrete approach may be to increase the sizes of the grounding disconnection part movable conductor 4, fixed side conductor 5 and movable side conductor 6 to decrease the current density or increase the contact pressure on the electrodes 16 and 17 in the switching part to decrease the contact pressure. However, the former approach leads to a larger unit size and the latter leads to increased capacity per line because the operating mechanism needs a larger driving force. As a consequence, in either case, the unit may have to be larger.
Therefore, as a countermeasure against temperature rise, improvement of heat radiation performance is effective rather than decrease of resistance to reduce the amount of generated heat. For improvement of the heat radiation performance, considering that the Joule heat generated at various parts of the switch with the power on is mainly derived from heat generation at contacts between electrodes and at conductors, it is more effective to radiate the heat mainly near these heat-generating spots. However, when the switching unit is integrally cast with the insulating resin 2 like the switching unit according to this embodiment, if the whole outer surface of the insulating resin 2 is shaped to have cooling fins, cooling fins are provided on all the areas including an area where the temperature difference between the outer surface of the insulating resin 2 and the switching gear board housing the switching unit is small, namely an area which does not require improved heat radiation performance.
Particularly when insulating resin fins are provided, since resin is lower in thermal conductivity than metal, a temperature distribution will occur in the insulating resin fins and heat will not be transferred to a remoter area from the heat generating spot, so the presence of radiating fins in such area scarcely contributes to improvement in heat radiation performance. Since the presence of fins all over the outer surface leads to an increase in the weight of the switching unit, it is desirable to determine the shape of fins and their positions so as to contribute well to improvement in heat radiation performance, rather than to provide fins all over.
For this reason, in the switching unit according to this embodiment, the resin radiating fins between the cable bushing center conductor 15 and the vacuum valve 26 have a large height and remoter fins from that area have a smaller height. Also, the fins around the spring contact 10 and bushing fixed electrode 3 have a large height and remoter fins from that area have a smaller height.
Also since the Joule heat generated at various parts of the switch with the power on is mainly derived from heat generation at electrode contacts and conductors, it is more effective to radiate heat mainly near the heat generating spots. However, if fins are formed all over the outer surface of the integrally cast switch without correlation with the outer shape of the switch located inside the insulating resin, the same type of fins are present even in areas where the temperature difference between the resin outer surface and the board is small. When the fins are formed of insulating resin, a temperature distribution will occur in the fins because the thermal conductivity of resin is lower than that of metal. Therefore, when resin radiating fins are used, the presence of the resin radiating fins all over may lead to an increase in the weight of the switch, so it is useful to determine the fin shape and fin positions appropriately in consideration of the radiation efficiency of the fins. In other words, if the fin height and the interval between fins are fixed, it is difficult to perform effective cooling depending on the characteristics of resin.
In this embodiment, as for the shape of the resin radiating fins in the circumferential direction of the vacuum container 8 and grounding disconnection part 27, the height gradually changes in the circumferential direction in order to ensure strength and insulation performance. The bottoms 1b of the resin radiating fins are formed so that resin distance 1W between the resin radiating fin bottoms 1b and the outer periphery of the vacuum container 8 is kept constant (namely, when a single resin-covered switch is used, the pattern made by connecting the bottoms of the resin radiating fins is similar to the pattern of the outer periphery of the switch. If there are a plurality of resin-covered switches, an area between switches deviates from similarity) so that the heat radiation performance can be improved while the required minimum resin height for strength and insulation performance is ensured. In addition, inner curvature 1b-out of the fin with the largest radial height among the resin radiating fins is made larger than inner curvature 1b-in of the fins other than the fin with the largest height. The reason is that because the resin radiating fin with the largest height deforms relatively largely and stress may concentrate on the tips 1t of the resin radiating fins 1 and the bottoms 1, its curvature is made the largest to reduce stress concentration. In addition, the resin radiating fin with the largest height is considered to cause electric fields to concentrate relatively easily. However, as mentioned above, when the inner curvature 1b-out of the resin radiating fin with the largest height is larger than the inner curvature 1b-in of the fins other than the fin with the largest height, concentration of electric fields can be alleviated. In other words, tolerance can be improved in terms of stress and field strength by adoption of the above structure. A flat part 2p where no resin radiating fins 1 exist is formed on part of the resin layer outermost surface so that the resin layer flat part 2p is made nearer to the resin layer outer surface than the tips 1t of the resin radiating fins 1. This protects the resin radiating fins through contact of the resin layer outer surface during assembling work, etc.
As mentioned above, Joule heat is generated in current conduction areas while current flows. The generated Joule heat is transferred to the surrounding medium and released outside from the surrounding medium. Here, the heat generated by both the cable bushing center conductor 15 and the conductors in the vacuum valve 26 is transferred to the insulating resin 2 between the cable bushing center conductor 15 and the vacuum valve 26, so higher radiation performance is required there. In this embodiment, the resin radiating fins between the cable bushing center conductor 15 and the vacuum valve 26 have a larger fin height and remoter fins from this area have a smaller fin height. In the area, a heat accumulation spot, the fins have a larger height to improve heat radiation performance. On the other hand, as the distance from the area as a heat accumulation spot increases, the density of conductors decreases and such remoter areas are no longer near a heat generating spot and also because the thermal conductivity of insulating resin fins is low, heat is hardly transferred from a heat accumulation spot; from both the above viewpoints, the need for improvement in heat radiation performance becomes smaller. Therefore, in order to avoid an increase in the size, in remoter areas from a heat accumulation spot, the resin radiating fins 1 are made to have a smaller height.
Similarly the insulating resin 2 around the spring contact 10 and bushing fixed electrode 3 covers the bushing fixed electrode 3, grounding disconnection part movable conductor 4, and the contact area between the spring contact 10 and bushing fixed electrode 3 and constitutes a heat accumulation spot. For this reason, the resin radiating fins 1 in this area are made to have a larger fin height and remoter fins from the area are made to have a smaller height.
The above not only improves cooling performance but also eliminates the possibility that the unit is larger than necessary.
Basically the resin radiating fins 1 are intended to expand the surface of heat transfer to the surroundings to reduce the surface heat density, so the larger the heat transfer area is, the better the performance is. However, expansion of the surface area more than necessary might cause a decline in surface thermal conductivity and a decline in the efficiency of heat transfer to the tips of the resin radiating fins 1. In other words, it is when the whole heat radiating surface has the same temperature as the heat source that the resin radiating fins 1 are most effective. Thus, in the case of metal, the thermal conductivity is high and a temperature distribution hardly occurs; on the other hand, in the case of the insulating resin 2, the thermal conductivity is low and a temperature distribution occurs to a large extent, so the resin radiating fins 1 are not made uniform in height but their height is gradually changed (height is changed in the fin longitudinal or axial direction and the circumferential direction) so that the resin radiating fins 1 perform cooling effectively.
In the switching unit according to this embodiment, the height of the resin radiating fins 1 gradually changes in the fin longitudinal direction (movable electrode axial direction) to deliver higher cooling performance than when the height does not change. In addition, the bottoms 1b of the resin radiating fins are shaped so that the resin distance 1W between the resin radiating fin bottoms 1b and the periphery of the vacuum container 8 is kept constant in order to ensure the required minimum resin height for strength and insulation performance and enhance heat radiation performance. In addition, the tips 1t and bottoms 1b of the resin radiating fins 1 have the required minimum curvatures to ensure strength and insulation performance according to height 1d of the resin radiating fins 1 (when height 1d is larger, the curvature is larger) and a flat part 2p where no resin radiating fins 1 exist is formed in part of the resin layer outermost surface and the resin layer flat part 2p is made nearer to the resin layer surface than the tips 1t of the resin radiating fins 1 to protect the resin radiating fins through contact of the resin layer outer surface during assembling work, etc. and eliminates the possibility that the unit is larger than necessary.
The height is large in a heat accumulation spot and in remoter areas from the spot, the height is smaller, thereby permitting more appropriate cooling for a temperature condition which occurs with the power on.
The switching unit according to this embodiment is formed by integrally molding the breaker and the grounding switch with insulating resin 2 and compactness is achieved by improvement of insulation characteristics and optimization. In this compact switching unit, sealability is high and heat easily concentrates, so the need for improved heat radiation performance is considerable rather than the need for reduction of heat generation. In this embodiment, resin radiating fins 1 are provided on the insulating resin 2 of the above switching unit and the fin height gradually changes in the longitudinal and circumferential directions and the tips 1t and bottoms 1b of the resin radiating fins have the required minimum curvatures to ensure strength and insulation performance according to height 1d, so that the fins are more appropriate. In addition, this eliminates the need for an increase in the size of the unit and does not prevent the unit from being compact. Rather, as a switching unit with heat radiation performance, the unit is very compact.
Furthermore, in this embodiment, the grounding disconnection part serves as a grounding switch which has a circuit breaking function, and due to this point as well as the above points, more compactness is achieved. Furthermore, the adoption of both vacuum insulation and aerial insulation makes it possible to provide a switch which is not large even if an aerial grounding disconnection part is employed. In the case of a switching unit which adopts either or all of these means to achieve compactness in this way, usually the heat generation density would increase and the heat radiation space would decreases; on the other hand, since the resin radiating fins 1 according to this embodiment improve heat radiation performance, desirably they eliminate the need for an increase in the size of the unit.
In the switching unit and switching gear according to this embodiment, the insulating resin has fins formed on the insulating resin outer surface in the circumferential direction and the distance of the vacuum valve and the periphery of the aerial-grounding disconnection part from the resin radiating fin bottoms is circumferentially almost constant and in consideration of temperature distribution attributable to low thermal conductivity peculiar to resin radiating fins, the radiation efficiency is improved to prevent the unit size from being larger than necessary, without sacrificing cooling performance. If these fins are not used, the unit must be larger for heat radiation; rather, the presence of these fins improves heat radiation performance and contributes to making the entire unit more compact. With the above structure, cooling performance can be improved in a low-resistance circuit switch which can turn on and off high voltage/high current, breaks the circuit and perform grounding.
In this embodiment, the outer surface of the insulating resin 2 has a flat part 2p and the tip of the insulating resin 2 is located inside the flat part 2p surface, so the fin tips are not damaged even when the switching unit after being cast with the insulating resin 2 is laid down during assembling work, etc.
In addition, in this embodiment, inner curvature 1b-out of the fin with the largest fin radial height is larger than inner curvature 1b-in of the fins other than the fin with the largest height, which permits stress concentration on the fin with the largest fin radial height and also alleviates concentration of electric fields. For this embodiment, it has been explained that only the fin with the largest fin radial height has a large inner curvature; however, it is also effective to make fins with larger radial height have larger curvatures and fins with smaller height have smaller curvatures, according to the fin radial height. In addition, it becomes possible to ensure strength and insulation performance of the edges of the outer surface of the resin layer covering the conductors and container.
Also in this embodiment, the resin radiating fins 1 are oriented in four different directions at regular intervals of 90 degrees as shown in
The second embodiment will be described referring to
As shown in
In addition, the tips of the metal radiating plates 1m have the required minimum curvature (roundness) for insulation performance so that the plates can function as insulating shields.
In this embodiment, due to the presence of the radiating plates 1m, heat from a heat accumulation spot is moved to an area where heat should be radiated. The height of the resin radiating fins 1 is the largest around the radiating plate 1m nearest to the insulating resin 2 surface among the radiating plates 1m and in axially remoter areas from around the radiating plate 1m nearest to the insulating resin 2 surface, the height is smaller, so that the moved heat can be efficiently radiated. More preferably, when the radiating plates 1m are formed (connected) on the conductors inside the insulating resin 2 and the edges of the vacuum valve 26 in a way to surround the conductors and the area around the vacuum valve 26, heat from the conductors and the vacuum valve 26 is transferred to the radiating plates 1m, where heat is accumulated, so in an area where the surface temperature of the insulating resin 2 outer surface near the heat-accumulated radiating plate 1m is highest, the height of the resin radiating fins 1 in the longitudinal direction is largest and in the other areas, the height is smaller.
It is obvious that even when the metal radiating plates 1m are combined with the resin radiating fins 1 as in this embodiment, the same various advantageous effects as described in connection with the first embodiment can be brought about. What is common to both the embodiments is that the height of the resin radiating fins is not uniform in the longitudinal and circumferential directions but the height gradually changes and in order to achieve further advantageous effects the height of the resin radiating fins in a heat accumulation spot is made the largest to enhance cooling performance.
The third embodiment will be described referring to
In the first and second embodiments, the tips of the resin radiating fins 1 form two pairs of planes: a pair of planes facing each other with the aerial grounding disconnection part 27 or the vacuum valve 26 between them and a pair of planes facing each other with the aerial grounding disconnection part 27 and the vacuum valve 26 between them; on the other hand, in this embodiment, as shown in the sectional view of
As in this embodiment, it is possible that metal radiating plates 1m are provided and resin radiating fins 1 are located only on a pair of planes facing each other. Another approach that no metal radiating plate 1m is provided and resin radiating fins 1 are located only on a pair of planes facing each other is not excluded. To what extent the cooling performance should be improved depends on the amount of supplied current, the temperature of the installation environment and so on. It is obvious that various modifications as described here are possible.
The fourth embodiment will be described referring to
The switching gear according to this embodiment is roughly comprised of a bus 40 connected to the power system to receive power, a switching unit 46 being connected to the bus 40 and including a switch, a cable 42 for distributing power from the switching unit 46 to a load, a cable head 45 for connecting the switching unit 46 according to the first embodiment and the cable 42, an actuator 43 for operating the switch in the switching unit 46, and a control device chamber 44 housing a protective relay, etc. to protect a device at the time of detection of overcurrent, stroke of lightning, etc.
The switching unit 46 is not limited to the abovementioned one according to the first embodiment and it may be any one of other various switching units including the ones according to the abovementioned embodiments. At least the abovementioned advantageous effects are not impaired by applying any of such switching units to the switching gear.
In the switching gear according to this embodiment, the switching unit 46 has resin radiating fins for heat radiation, the height of which gradually changes not only in the longitudinal direction but also in the circumferential direction, so the cooling performance can be improved in the switching gear as a whole because a main heat generating spot in the switching gear (board) is the switching unit.
Another noteworthy point is that the whole switching gear can be compact because the switching unit as a main component of the switching gear can be compact.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-121480 | May 2012 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2013/060580 | 4/8/2013 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2013/179772 | 12/5/2013 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 3716098 | Dotto | Feb 1973 | A |
| 4123618 | Cushing | Oct 1978 | A |
| 4540863 | Bettge et al. | Sep 1985 | A |
| 6735068 | Hartman | May 2004 | B1 |
| 6897396 | Ito | May 2005 | B2 |
| 20010002666 | Ito | Jun 2001 | A1 |
| Number | Date | Country |
|---|---|---|
| 59-4141 | Jan 1984 | JP |
| 60-54126 | Mar 1985 | JP |
| 2-128335 | Oct 1990 | JP |
| 5-303929 | Nov 1993 | JP |
| 8-132711 | May 1996 | JP |
| 2001-6502 | Jan 2001 | JP |
| 2001-28858 | Jan 2001 | JP |
| 2001-160342 | Jun 2001 | JP |
| 2005-74885 | Mar 2005 | JP |
| 2012-69345 | Apr 2012 | JP |
| Entry |
|---|
| International Search Report (PCT/ISA/210) dated Jun. 4, 2013 with English-language translation (Four (4) pages). |
| Korean Office Action issued in counterpart Korean Application No. 10-2014-7033134 dated Apr. 21, 2016 with English-language translation (eleven (11) pages). |
| Number | Date | Country | |
|---|---|---|---|
| 20150102013 A1 | Apr 2015 | US |
