POWER SWITCHING DEVICE |
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申请号 | EP15709654.6 | 申请日 | 2015-03-04 | 公开(公告)号 | EP3060745B1 | 公开(公告)日 | 2018-01-03 |
申请人 | Siemens Aktiengesellschaft; | 发明人 | KRISTENSEN, Knut, Schonhowd; | ||||
摘要 | A power switching device for operation in an underwater environment is provided. The power switching device has a base unit with a pressure compensated enclosure. The enclosure forms a single base chamber filled with a liquid or gel. A power input and at least a first power output are mounted to the base unit. A pressure resistant wall is mounted to the base unit and separates a base chamber from a switching chamber. Penetrators are arranged in the pressure resistant wall. Input busbars and output busbars are directly connected to the penetrators in the base chamber. | ||||||
权利要求 | |||||||
说明书全文 | The present invention relates to a power switching device for under water operation, in particular for operation in a deep sea environment, and to a method of assembling a power switching device. Due to the increasing energy demand, offshore oil and gas production is moving into deeper waters. Wells for hydrocarbon production can be located in water depth down to 3.000 meters or more and a considerable distance from shore. For ensuring an efficient and secure production, processing facilities are being installed at the ocean floor in proximity to such well. Installations on the ocean floor can comprise a range of components, including pumps, compresses and the like as well as a power grid for providing such components with electric power. The power grid installed at the ocean floor may for example comprise a transformer, switching equipment, drives including variable frequency converters and the like. These components are exposed to pressures of up to or even in excess of 300 bars (at a depth of 3.000 meters). To protect such components from the corrosive environment of the surrounding seawater and to deal with the high pressures, pressure resistant enclosures or pressure compensated enclosures can be used. A device for switching power in a power grid located at the ocean floor may for example employ several compartments to prevent electric equipment from coming into contact with seawater. As an example, the document The document The document The document It is desirable to improve the safety and reliability of a switching device operated at the ocean floor. It is also desirable to provide an improved functionality and electrical operation. Furthermore, it is beneficial if such switching device is relatively compact and light-weight, in order to reduce costs of transportation and installation as well as costs of the device itself. Accordingly, there is a need for an improved switching device operable in an underwater environment, and to mitigate at least some of the drawbacks mentioned above. This need is met by the features of the independent claims. The dependent claims describe embodiments of the invention. An embodiment of the present invention provides a power switching device for operation in an underwater environment, in particular in a deepsea environment, which may be adapted to be operated at the ocean floor. The power switching device comprises a base unit having a pressure compensated enclosure, wherein the pressure compensated enclosure forms a single base chamber filled with a liquid or gel, for example a dielectric liquid. It further comprises a switching assembly having a pressure resistant enclosure which forms a switching chamber and comprises at least a first switch, in particular a high voltage circuit breaker (CB), disposed in the switching chamber. A power input and at least a first power output are mounted to the base unit, in particular to the pressure compensated enclosure thereof. Plural power distribution busbars are arranged in the base chamber of the base unit. The plural power distribution busbars comprise at least a set of input busbars which form part of an input electrical connection that leads from the power input to the first switch. They further comprise at least a first set of output busbars which form part of a first output electrical connection that leads from the first switch to the first power output. A pressure resistant wall is mounted to the base unit and separates the base chamber from the switching chamber. Penetrators are arranged in the pressure resistant wall. The penetrators are configured to lead the input electrical connection and the output electrical connection through the pressure resistant wall. The input busbars and/or the output busbars are directly connected to the penetrators in the base chamber. By providing only a single base chamber between the power input and the penetrators leading into the switching chamber, the complexity of the power switching device and its weight and size may be reduced. Furthermore, the inventors of the present invention have discovered that in contrast to the general belief, providing a single chamber in which the power distribution equipment is disposed in fact improves the reliability of the power switching device and the protection against water ingress compared to an approach which uses plural separate chambers that are sealed from each other. In particular, plural separate chambers require a number of additional components, such as additional electrical connections, boot seals, inspection hatches, pressure compensators and the like. Each additional component is associated with an additional risk of failure. The reduced complexity provided by the single base chamber of the present embodiment thus in fact improves reliability, even though only a single barrier against the surrounding seawater is provided compared to a plural chamber approach having two barriers. Furthermore, the configuration of the present embodiment allows the input and output busbars to be directly connected to the penetrators which lead the electrical connections into the switching chamber, thus improving the electrical performance of the power switching device. Losses, arcing and potential failure of electrical connections may thus be reduced. In an embodiment, the pressure resistant enclosure of the switching assembly is configured to maintain a predefined internal pressure in the switching chamber when the power switching device is deployed under water. Preferably, the predefined internal pressure is a pressure below 10 bar. In an embodiment, the input busbars and/or the output busbars may for example be connected by means of bolts to a conductive core of the respective penetrator, and the respective busbar may for this purpose comprise a bent portion or a flexible busbar section. The first switch may be arranged and configured such that it is capable of connecting and disconnecting the power input from the power output. Thereby, a switching mechanism or protection mechanism may be provided. As an example, the first switch may be controlled so as to open upon occurrence of an overvoltage or overcurrent, or it may be controlled so as to turn on and off the power supply to a load, such as a compressor or pump installed at the ocean floor. The pressure resistant wall comprising the penetrators may be termed penetrator plate. In an embodiment, the pressure resistant wall is fixedly mounted to the pressure compensated enclosure of the base unit and closes an opening in the pressure compensated enclosure thereof. It may for example be mounted by means of bolts or it may be welded. The pressure resistant enclosure of the switching chamber may have an opening and it may be mounted to the pressure resistant wall such that the pressure resistant wall closes the opening in the pressure resistant enclosure. Accordingly, there may be only a single wall between the base chamber and the switching chamber, thus requiring fewer penetrations and reducing the complexity of the power switching device. The pressure resistant wall may be a circular metal plate. In an embodiment, the power switching device further comprises at least a first and a second seal between the pressure resistant wall and the pressure compensated enclosure of the base unit. The at least two seals may comprise at least one, preferably two elastomeric seals. In another embodiment, the at least two seals may comprise at least one, or even at least two metal seals. In other configurations, both metal and elastomeric seals can be provided. An example configuration may have one or two metallic seals and one or two elastomeric seals. Additionally or alternatively, a weld may be provided between the pressure resistant wall and the pressure compensated enclosure of the base unit. In an example configuration, one or more elastomeric seals may be provided, and the pressure resistant wall may in addition be welded to the pressure resistant enclosure of the base unit. In such configurations, an effective sealing against the ingress of seawater into the single base chamber and thus an effective protection of the electric components disposed in the base chamber can be achieved. The seals may for example be implemented as flange seals, they may be ring shaped seals sealing between a flange of the pressure compensated enclosure and the pressure resistant wall. In an embodiment, the power input comprises electrical conductors leading into the base chamber, and the input busbars may be directly connected to the electrical conductors. The power input may for example be provided in form of a connector or a penetrator passing a conductor into the base chamber. The input busbars may be mounted directly to such conductor, e.g. by making use of a band or flexible busbar section which is fixed to the conductor by a fastening element, such as a screw. In particular, the input busbars and/or the output busbars may run continuously between the power input or the power output, respectively, and the penetrators of the penetrator plate. In such configuration, an efficient and low-loss transport of electric power through the power switching device may be achieved. The configuration may be similar for further switches and power outputs of the power switching device. In an embodiment, the power input may be a three-phase power input and the power output may be a three-phase power output. In such configuration, each set of busbars may comprise at least three busbars. In an embodiment, the switching assembly comprises at least two switches, and the power switching device further comprises a second power output mounted to the base unit. The plural power distribution busbars arranged in the base chamber may comprise a second set of output busbars which form part of a second output electrical connection with leads from the second switch to the second power output. The power input connection may then also connect to the second switch to provide power thereto. Plural consumers may thus be switched using such power switching device. The pressure resistant enclosure of the switching assembly may be a cylindrical enclosure which is closed at one end and open at the other end. At the open end, the pressure resistant enclosure may be fixedly mounted to the pressure resistant wall, e.g. by means of bolts or welding. Furthermore, at least two seals may be provided between the pressure resistant enclosure and the pressure resistant wall. In particular, at least one or two metal seals and/or at least one or two elastomeric seals may be provided, e.g. one elastomeric seal and two metal seals. In an embodiment, the power switching device may further comprise a (first) support frame arranged inside the base chamber and mounted to the pressure resistant wall. The input busbars and/or the output busbars may comprise busbar sections supported by the first support frame. By providing such support frame fixed to the pressure resistant wall, the assembly of the power switching device may be facilitated, since the support frame together with the busbar sections may be slid into a cylindrical section of the pressure compensated enclosure of the base unit. The support frame may be welded or bolted to the pressure resistant wall. The first support frame may comprise sliding elements, such as gliders, which may be made of a plastic material, for supporting the frame against an inner wall of the cylindrical section of the pressure compensated enclosure of the base unit, so that assembly is facilitated. In an embodiment, the power switching device may comprise a (second) support frame arranged inside the switching chamber and mounted to the pressure resistant wall. At least the first switch may be supported by this (second) support frame. Thus, assembling the switching assembly may be facilitated. The second support frame may furthermore support one or more additional switches and may furthermore support electrical connections inside the switching chamber, such as cables or the like. The second support frame may be adapted to be slid into a cylindrical section of the pressure resistant housing of the switching assembly. The second support frame may be fixed to the pressure resistant wall by welding, by bolting or the like. Although such configuration may not allow a disassembly of the power switching device into separate modules, since the electric components are fixed to the pressure resistant wall, it may have benefits with respect to the assembly. In an embodiment, the pressure compensated enclosure of the base unit comprises a first cylindrical section having an opening at a first end, the pressure resistant wall being mounted to the first end to close the opening. It further has a second cylindrical section, wherein the first and the second cylindrical sections meet in a cross junction or a T-junction to form the base chamber. A relatively compact design of the pressure compensated enclosure and thus of the base unit and the power switching device may thereby be achieved. The single base chamber may be the whole interior space inside the pressure compensated enclosure of the base unit which is formed by the first and second cylindrical sections. The busbars may be directly arranged inside this interior space of the pressure compensated enclosure. In particular, they are not surrounded by further chambers or walls, the pressure compensated enclosure providing a single barrier between the busbars and the surrounding ambient medium, in particular seawater. The pressure compensated enclosure may comprise further cylindrical sections, e.g. mounted perpendicular to the second cylindrical section, e.g. for providing mounting space for power inputs or power outputs, e.g. on a closing plate closing the end of such additional cylindrical section. In an embodiment, the plural power distribution busbars may comprise busbar sections extending along the axial direction of the first cylindrical section and busbar sections extending along the axial direction of the second cylindrical section. These busbar sections may be interconnected at the cross junction or the T-junction of the first and second cylindrical sections of the pressure compensated enclosure. In such configuration, a continuous busbar connection from the power input or power output to the penetrators of the pressure resistant wall may be achieved. In an embodiment, the first and second cylindrical sections meet in a cross junction and the first cylindrical section may have a further opening at a second end adjacent to the cross junction, the second opening being closed by a closing plate or by a pressure compensator. By means of such opening in proximity to the cross junction, easy access to the different busbar sections in the power switching device becomes possible, and assembly thereof may be facilitated. In particular, the connection of the busbar sections in the first cylindrical section and the busbar sections in the second cylindrical sections can be performed in efficient way. In an embodiment, the second cylindrical section may have a first opening closed by a closing plate on which the power input is provided, and a second opening at a second end, wherein the second end is adapted to be mounted to a corresponding second end of a pressure compensated enclosure of a second base unit. The input busbars may be configured to extend through the second opening into the pressure compensated enclosure of the second base unit. In such configuration, an extension of the power switching device by further base units having respective switching assemblies becomes possible. As an example, the power switching device may comprise one, two, three, or more additional base units having respective switching assemblies. In an embodiment, the pressure compensated enclosure of the base unit comprises an enclosure section (in particular the above mentioned second cylindrical section) extending along a longitudinal direction. The switching assembly may extend perpendicular to this longitudinal direction, and the input busbars may comprise a first busbar section extending parallel to the longitudinal direction within the enclosure section and a second busbar section extending perpendicular to the longitudinal direction towards the switching assembly. In an embodiment, the power input may be mounted to a first end of the second cylindrical section of the pressure compensated enclosure of the base unit, and the power output may be mounted to the cylindrical wall of the second cylindrical section, for example by means of the above mentioned additional cylindrical section. Accordingly, one, two or more power outputs may extend perpendicular to the longitudinal direction of the second cylindrical section. Furthermore, the output busbars may comprise a busbar section that extends perpendicular to the longitudinal direction towards the power outputs. In an embodiment, the power switching device further comprises a pressure compensator that is in fluid communication with the base chamber of the base unit and that is configured to balance a pressure inside the base chamber to an ambient pressure prevailing outside the power switching device when the power switching device is installed under water, for example at the ocean floor. Such pressure compensator may for example be a single wall bellows type pressure compensator formed of formed metal bellows, as described in In an embodiment, the switching assembly, in particular the pressure resistant enclosure, may be configured to maintain a predefined internal pressure in the switching chamber when the power switching device is deployed under water, e.g. on the ocean floor. The predefined internal pressure may be a pressure in a range between about 1 and about 10 bar, for example a pressure below 10 bar, below 5 bar or below 2 bar. The predefined internal pressure may be about atmospheric pressure, e.g. it may be a pressure close to atmospheric pressure, it may for example be a pressure of about 1.5 bar. The switching chamber may be filled with a gas or a liquid. In an embodiment, the switching chamber may be filled with SF6. The first switch and the further switches may for example be vacuum circuit breakers. In an embodiment, directly connected refers to a connection without any intervening elements. In an embodiment, a connecting element of the input busbars and/or the output busbars, such as a bent busbar portion or a flexible busbar section, is mounted to the penetrators in the base chamber to provide said direct connection. Mounting may for example occur by bolting, welding or soldering the connecting element of a busbar to a conductive core of the respective penetrator. In an embodiment, the direct connection between the input busbars and/or the output busbars and the penetrators in the base chamber is provided without any intermediate cable connection, but the respective busbar is connected to the conductor of the respective penetrator by relatively short connecting element, for example having a length of less than 20% or less than 10% of the length of the respective busbar. Such connecting element can be a busbar portion, a flexible busbar section, a conductor section (insulated or non-insulated) or the like. A further embodiment of the invention provides a method of assembling a power switching device for operation in an underwater environment, in particular a deepsea environment. The method comprises the steps of providing a base unit comprising a pressure compensated enclosure, a power input mounted to the base unit, and at least a first power output mounted to the base unit; providing a pressure resistant wall comprising penetrators arranged in the pressure resistant wall; directly connecting sections of input busbars which form part of an input electrical connection and/or sections of output busbars which form part of a first output electrical connection to the penetrators of the pressure resistant wall; mounting the pressure compensated enclosure of the base unit to the pressure resistant wall to form a single base chamber in which the input busbars and the output busbars are arranged; mounting a pressure resistant enclosure to the pressure resistant wall so as to form a switching chamber, wherein at least a first switch is disposed in the switching chamber; configuring the input electrical connection such that it leads from the power input to the first switch via the input busbars and the penetrators; and configuring the output electrical connection such that it leads from the first switch to the first power output via the penetrators and the output busbars. By such method, advantages similar to the ones outlined further above with respect to the power switching device may be achieved. It should be noted that the above description of steps is not meant to indicate a particular order of the steps; rather, the steps may be performed in a different order. As an example, the pressure compensated enclosure may be mounted after mounting the pressure resistant enclosure, or they may be mounted simultaneaously. In a further embodiment, the method may comprise: providing a pressure resistant wall comprising at least a first frame; arranging sections of input busbars which form part of an input electrical connection and sections of output busbars which form part of a first output electrical connection on the first frame; and mounting the pressure compensated enclosure of the base unit to the pressure resistant wall to form a single base chamber in which the first frame and the input busbars and output busbars are arranged. By making use of the frame and the busbars in the above outlined configuration, the assembly of the power switching device is facilitated. In an embodiment, the pressure resistant wall may further comprise a second frame, and the method may further comprise the step of arranging at least the first switch, in particular a high voltage circuit breaker, on the second frame. Accordingly, assembly of the power switching device may be further facilitated. In embodiments of the method, the method may be performed so as to assemble a power switching device in any of the above outlined configurations. In particular, the method may comprise steps as described above with respect to embodiments and configurations of the power switching device. It is to be understood that the features mentioned above and those said to be explained below can be used not only in the respective combinations indicated, but also in other combinations or in isolation, without leaving the scope of the present invention. Further embodiments of the invention are conceivable. As an example, in some embodiments, the input busbars and the output busbars may not be connected directly to the penetrators of the pressure resistant wall. They may for example be connected indirectly, e.g. via an intervening electrical connection. The claims of one or more divisional applications may be aimed such embodiment or at further aspects, for example at the enclosure of the switching device, the supporting frame of the busbar sections or other aspects disclosed herein. The foregoing and other features and advantages of the invention will become further apparent from the following detailed description read in conjunction with the accompanying drawings. In the drawings, like reference numerals refer to like elements.
In the following, embodiments of the invention will be described in detail with reference to the accompanying drawings. It is to be understood that the following description of the embodiments is given only for the purpose of illustration and is not to be taken in a limiting sense. It should be noted that the drawings are to be regarded as being schematic representations only, and elements in the drawings are not necessarily to scale with each other. Rather, the representation of the various elements is chosen such that their function and general purpose become apparent to a person skilled in the art. Power input 12 and power outputs 13, 14 may for example be provided in the form of penetrators which are mounted in a penetrator feed-through provided in the wall of the pressure compensated enclosure 11. A conductor 25 can thus for example be led from outside the enclosure 11 into the single base chamber 90 of the base unit 10. Outside the enclosure 11, an underwater cable may terminate at the power input 12. In other configurations, a part of a connector may be provided as the power input 12 or the power outputs 13, 14, the connector part then leading a conductor 25 into the chamber 90 of base unit 10. Further configurations are conceivable. Base chamber 90 is formed by a first cylindrical section 15 and a second cylindrical section 16 of the pressure compensated enclosure 11. In the example of To lead electrical connections into and out of the switching chamber 54, penetrators 61, 62 and 63 are provided in the pressure resistant wall 60, which may thus also be termed penetrator plate. The penetrators 61, 62, 63 may for example comprise a conductor 65 disposed in a body of insulating material 66. The penetrator disclosed in the document The switching assembly 50 comprises a first switch 51 and a second switch 52. In other embodiments, only a single switch or more than two switches may be provided. The switches may for example be high voltage (HV) circuit breakers, in particular vacuum circuit breakers. They may be used for protective measures, e.g. cutting off the power in case of a short circuit, or may be used for switching on and off equipment coupled to the power outputs 13, 14. An input electrical connection is provided from the power input 12 to the first and second switches 51, 52. A set of input busbars 20 is used inside the base chamber 90 to provide the input electrical connection. The power switching device 100 can be configured as a three-phase system, and accordingly, the set of input busbars 20 may comprise three busbars, one for each phase. Each busbar may have a section 21 which runs along the axial direction of the first cylindrical section 15 of the enclosure 11 and a second section 22 which runs along the axial direction of the second cylindrical section 16 of enclosure 11. A first output electrical connection from the first switch 51 to the first power output 13 is inside the base chamber 90 provided by a first set of output busbars 30. A second output electrical connection from the second switch 52 to the second power output 14 is provided inside base chamber 90 by a second set of output busbars 40. It should be clear that each set of output busbars may again comprise three busbars, one for each phase of electric power. Similar to the input busbars, the output busbars each comprise a section running parallel to the axial direction of the first cylindrical section 15 and a section running parallel to the axial direction of the second cylindrical section 16 of the enclosure 11. Each of the penetrators 61, 62 and 63 may accordingly comprise three penetrators, one for each phase. In the example of The ends of the busbars 20, 30, 40 may for this purpose be provided with bent portions or flexible busbar sections in order to achieve a suitable arrangement of the penetrators 61, 62, 63 in the penetrator plate 60. Flexible busbar sections may be provided in form of thin strips of plates, e.g. copper plates, which are stacked together in order to form the busbar section, thus making the busbar section flexible. These may be bolted to the conductor 65 of the penetrator by means of a bolt. On their other ends, the busbars 20, 30, 40 may be directly connected to the conductor 25 of the power input 12 or of the power outputs 13, 14, respectively. Again, the conductors 25 can be provided with a threaded hole towards which the end of the busbar is bolted. Flexible or bent busbar sections may be employed to achieve a desired arrangement of the power input 12 and the power outputs 13, 14. Accordingly, in such configuration, a continuous busbar electrical connection can be achieved inside the base chamber 90 from the power input 12 to the first and second switches 51, 52 and from these switches to the power outputs 13, 14. A reliable and efficient transport of electric power inside the base unit 10 can thus be achieved. Inside the switching chamber 54, the electrical connections may be provided in any suitable way, for example by means of cables or further busbars. The power switching device 100, in particular the pressure resistant enclosure 55 and the pressure compensated enclosure 11, are adapted to enable a deployment of the power switching device 100 at water depths of at least 1,000 m, preferably at least 3,000 m. Penetrator plate 60 may thus be configured to withstand differential pressures of at least 100 bar, preferably at least 300 bar. Power switching device 100 may be adapted to supply electric power to a pump, a compressor or other equipment operated at the ocean floor. The power switching device 100 may be adapted to be operated in a voltage range of about 1,000 to about 100,000 V, in particular of about 10,000 to about 80,000 V. It may for example be operated at about 36,000 V or at about 72,000 V. Base unit 10 further comprises a pressure compensator (not shown). The pressure compensator is in fluid communication with the base chamber 90. The pressure compensator provides pressure balancing between the pressure in base chamber 90 and the pressure prevailing outside the power switching device 100. The pressure compensator may for example comprise a bellows which can contract and expand in accordance with changes of the volume of the medium filling the base chamber 90. Such medium may for example be a liquid or gel, in particular a dielectric liquid. Such pressure compensator is for example disclosed in the document By providing a single base chamber 90 and continuous busbar connections inside the base chamber 90, a compact and efficient power switching device 100 can be obtained. Furthermore, a significant reduction in weight can be achieved, due to the compact size of the enclosures 11 and 55. Furthermore, the complexity of the power switching device 100 is reduced since only a single base chamber 90 is provided. Compared to devices having separate chambers in separate modules, or having one chamber nested within the other, several advantages can be achieved. These include that only one volume needs to be pressure compensated, whereas with separate chambers, a pressure compensator for each chamber is required. Furthermore, such configurations require more electrical connections, boot seals, inspection hatches and the like. Since all these elements bear a certain risk of failure, the overall reliability of the power switching device 100 can be improved due to the reduced complexity. As an example, by using two chambers each having a pressure compensator, which may be regarded as a weak point, the risk of failure is doubled. In contrast, the risk of failure can be reduced with embodiments of the present invention. The dashed line in In the example of A first opening of the first cylindrical section 50 is closed by the penetrator plate 60. The opening 19 at the other end can be closed by a further closing plate. By means of this second opening 19, access can be gained to the busbar sections 21, 22 of the input busbars 20 and to respective sections of the output busbars 30, 40. Assembly of the busbar sections is thus facilitated. Instead of mounting a closing plate at this position 19, a pressure compensator may be mounted for providing pressure compensation of the base chamber 90. Furthermore, a second supporting frame 72 can be similarly attached to the penetrator plate 60. The second supporting frame holds in the example of As illustrated in Note that in other configurations, frame 71 may by a cylindrical frame, and the busbar sections may in such configuration be distributed around the cylindrical face of the frame. For connecting e.g. the first busbar sections 21 to the second busbar sections 22 in the junction of the cylindrical enclosure sections 15, 16, the assembly illustrated in As can be seen from the above, a power switching device 100 is provided which has a single pressure compensated base chamber, thus reducing complexity and increasing the reliability of the power switching device. Furthermore, continuous busbar connections are provided inside the base chamber. Assembly of such continuous busbar connections is achieved by providing a housing having first and second cylindrical sections and providing access to busbar connections, and by further mounting busbar sections to a frame which is attached to the penetrator plate 60. While specific embodiments are disclosed herein, various changes and modifications can be made without departing from the scope of the invention. The present embodiments are to be considered in all respects as illustrative and non-restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein. |