A conservator device for use with an offshore electrical induction device

Abstract

A conservator device (1) for use with an electric induction device (2). The electric induction device (2) comprises a liquid-filled volume, and the conservator device comprises a tank (3), and one or more wall primary wall members (4) provided within an inner volume (V) of the tank (3). The primary wall members (4) are adapted to horizontally divide the inner volume (V) of the tank into a plurality of compartments (C). The secondary wall members (5) are provided within the inner volume (V) of the tank, and are adapted to vertically divide the inner volume (V) of the tank, or one or more of said compartments, into an upper compartment (CU) and a lower compartment (CL). One or more of said upper compartments (CU) are provided with a respective bladder (6) inside the respective upper compartment (CU). Each respective bladder (6) is attached to the tank (3) such that an inner volume of the bladder (6) is fluidly separated from a remaining portion of the inner volume (V) of the tank (3), and each bladder (6) is fluidly connected to ambient air through a first port (8) of the tank (3). The tank (3) comprises a second port (7) adapted to provide a liquid connection between said remaining portion of the inner volume of the tank (3) and a liquid-filled volume of the electric induction device (2). The primary (4) and / or secondary (5) wall members are adapted to enable liquid flow between the compartments (C, CU, CL).

Description

Technical field

[0001] The present invention relates to a conservator device for use with an electrical induction device in offshore conditions. The electrical induction device may be a transformer or a shunt reactor and the electrical device comprises a chamber being at least partly filled with a liquid, such as oil. Temperature changes make the liquid expand and contract and the conservator device is provided to receive and hold a portion of the liquid in response to increased temperature forcing liquid out of the chamber.Background

[0002] Offshore substations are for example used to transfer power to shore from offshore wind farms. The offshore substations comprise liquid-immersed induction devices such as power transformers and shunt reactors. The induction devices are immersed in an insulation liquid that changes volume depending on its temperature. Each induction device is therefore fitted with a conservator device to contain the additional volume of liquid as it expands.

[0003] The induction device comprises cellulose insulation with material properties that degrade in the presence of oxygen. To prevent influx of oxygen from the atmosphere into the insulation liquid, the conservator device may be fitted with a barrier separating the insulation liquid from air. The barrier can be a flexible bladder or diaphragm, where the space inside the bladder or above the diaphragm is in communication with the atmosphere. Alternatively, the conservator device can be sealed from the atmosphere and filled with nitrogen, in which case no flexible bladder or diaphragm is needed.

[0004] The offshore substation may be assembled far from the final installation site and transported to the final offshore installation site by sea. In deep water, the offshore substation may be placed on a floating platform. The conservator device may be exposed to sea wave motion creating a sloshing movement of the liquid inside the expansion tank. The sloshing movement involves large forces that may damage the bladder or diaphragm. Further, oil sloshing inside the conservator device may damage the barrier or other components, such as an oil level indicator. Further, sloshing may cause false alarm in a Buchholz relay. Accordingly, sloshing of the insulation liquid should be avoided in order to mitigate failure of the electric induction device.

[0005] An object of the present invention is thus to provide an improved conservator device suitable for offshore use.Summary

[0006] According to a first aspect of the invention, this and other objects are achieved by an conservator device according to claim 1 with alternative embodiments defined in the dependent claims. The conservator device comprises: a tank, and one or more wall primary wall members provided within an inner volume of the tank. The one or more primary wall members are adapted to horizontally divide the inner volume of the tank into a plurality of compartments.

[0007] The conservator device further comprises one or more wall secondary wall members provided within the inner volume of the tank. The one or more secondary wall members are adapted to vertically divide the inner volume of the tank, or divide one or more of said compartments, into a respective upper compartment and a respective lower compartment.

[0008] One or more of the upper compartments are provided with a respective bladder inside the respective upper compartment.

[0009] Each respective bladder is attached to the tank such that an inner volume of the bladder is fluidly separated from a remaining portion of the inner volume of the tank, and each bladder is fluidly connected to ambient air through a first port of the tank. Accordingly, the remaining portion of the inner volume of the tank is all of the inner volume of the tank except for the volume occupied by the bladders.

[0010] The tank comprises a second port adapted to provide a liquid connection between said remaining portion of the inner volume of the tank and a liquid-filled volume of the electric induction device.

[0011] The one or more primary and / or secondary wall members are adapted to enable liquid flow between the compartments. Liquid flow may be enabled by designing the wall members such that fluid may flow around the wall members, or by providing an array or through openings in the wall members, or by using a porous liquid-permeable material for the wall members (applies to both primary and secondary wall members).

[0012] The conservator device is used to act as a conservator device for liquid of the electric induction device. Upon expansion of liquid in the electric induction device caused by heating of the liquid, liquid flows into the inner volume of the tank of the conservator device, forcing air out of the bladder. The liquid is typically an insulation liquid, such as a suitable oil.

[0013] The bladder prevents air from mixing with liquid inside the tank. By horizontally dividing the inner volume into compartments using the primary wall members, movement of liquid within the tank is mitigated by the primary wall members, thus reducing sloshing liquid inside the tank. The secondary wall members dampen the flexible mass of the liquid inside the tank.

[0014] The sloshing movement may be severe at resonance frequency. The liquid has an effective mass (convective mass + impulsive mass). Impulsive mass is related to rigid-motion and convective mass is associated with flexible-mass. The convective mass is the mass that is moving and creating the sloshing. Dividing the conservator into several compartments will reduce the convective mass and thereby reduce the sloshing. Hence, a suitable horizontal division of the inner volume of the tank into compartments will mitigate resonance frequency effects on sloshing.

[0015] The one or more secondary wall members may be adapted to be vertically movable in response to varying liquid level in the tank such that the vertical position of the one or more secondary wall member is raised in response to rising liquid level, and such that the vertical position of the one or more secondary wall members is lowered in response to falling liquid level.

[0016] The vertical movability of the at least one secondary wall member enables the secondary wall to limit vertical movement of liquid for higher liquid levels as well as for lower liquid levels, and thus enables improved restriction of movement of the liquid at varying liquid levels. This in turn, improves protection from damage of internal components, e.g. barrier / bladder / diaphragm, oil level indicator, etc. Furthermore, the secondary wall members can indicate liquid level in the tank.

[0017] The vertical position of the one or more secondary wall members may be governed by a support mechanism, said support mechanism being powered by actuators controlled by an electronic control unit based on a signal from a liquid level sensor adapted to determine one or more liquid levels in the tank, or said support mechanism comprising a buoyant body adapted to float in liquid in the tank for controlling the vertical position of the one or more secondary wall members based on a vertical position of the buoyant body.

[0018] The secondary wall members and / or the primary wall members may be liquid-permeable.

[0019] The liquid-permeability of the wall members enable a restricted flow of liquid through the whole wall member, thus mitigating any need of leaving a gap between the tank and the respective wall member for liquid to flow through and further enables improved damping of local pressure build-up by the primary walls upon acceleration of the tank.

[0020] The primary and secondary wall member(s) may be made of porous material.

[0021] The porous material enables an even flow of liquid over the whole surface of each wall member.

[0022] The primary and secondary wall member(s) may comprise an array of through openings providing said fluid-permeability.

[0023] The array of through openings enables use of a solid material for the wall members, thus providing for improved robustness and improved control over local liquid flow rates over the surface of the wall members.

[0024] The primary and secondary wall members may be plates. The plates are easy to produce and provide a planar support for the bladder, thus reducing wear and risk of failure of the bladder. Plate-formed wall members also provide improved stiffness.

[0025] The at least one primary wall member may extend from an upper portion of the tank towards a lower portion of the tank.

[0026] The at least one primary wall member may extend substantially vertically. The vertical direction refers to the direction after installation of the conservator device, i.e. in use (in still weather conditions).

[0027] Each primary wall member may cover a respective whole cross-section of the tank.

[0028] By covering a whole cross-section of the tank, the primary wall member provides improved rigidity to the tank.

[0029] A second aspect of the invention relates to a system comprising an electric induction device and the conservator device according to any one of the preceding claims.

[0030] The electric induction device may be a transformer or a shunt reactor.Brief description of drawings

[0031] Figs. 1-5 are schematic illustrations not drawn to scale. Fig. 1 shows a cross-sectional side view of a system comprising an electric induction device and a conservator device according to an embodiment. Fig. 2 shows a top view of the system device also shown in fig. 1. Fig. 3 show an embodiment of a first wall member comprising an array of through openings. Fig. 4 shows an alternative embodiment of the system also shown in fig. 1. In fig. 4, the conservator device of the system comprises a higher number of compartments. Fig. 5 shows a top view of the system also shown in fig. 4. Detailed description

[0032] Embodiments of the present invention will hereinafter be described with reference to the appended drawings.

[0033] As shown in fig. 1, a conservator device (1) is suitable for use with an electric induction device 2, such as a transformer or a shunt reactor. The electric induction device 2 comprises a liquid-filled volume. Temperature variations of the liquid in the liquid-filled volume causes the liquid to expand and contract and the conservator device 1 forms an expansion chamber for liquid of the liquid-filled volume of the electric induction device 2.

[0034] It is an object of the invention to improve the longevity of the conservator device 1 when used at sea, i.e. in conditions at which the conservator device 1 is exposed to accelerations.

[0035] The conservator device 1 comprises a tank 3, and one or more wall primary wall members 4 provided within an inner volume V of the tank 3. The one or more primary wall members 4 are adapted to horizontally divide the inner volume V of the tank into a plurality of compartments C.

[0036] Accordingly, a plurality of compartments distributed in a horizontal plane are formed, thereby reducing the maximum horizontal distance between wall structures of the conservator device 1.

[0037] The conservator device 1 further comprises one or more wall secondary wall members 5 provided within the inner volume V of the tank. The one or more secondary wall 5 members are adapted to vertically divide the inner volume V of the tank, or one or more of said compartments, into an upper compartment CU and a lower compartment CL.

[0038] One or more of said upper compartments CU are provided with a respective bladder 6 inside the respective upper compartment CU. It should be understood that although the bladders are illustrated schematically as rectangular boxes, they typically exhibit a more irregular shape with rounded corners. The bladders are made of a flexible material, such as NBR, NBR-reinforced polymer, polyurethane or any other suitable material. The flexible material may be an elastic material.

[0039] The bladder 6 may be formed as a bag or other structure with flexible walls enabling a volume of the bladder 6 to adapt in response to liquid being force into or out of the tank 3.

[0040] Each respective bladder 6 is attached to the tank 3 such that an inner volume of the bladder 6 is fluidly separated from a remaining portion of the inner volume V of the tank 3, and each bladder 6 is fluidly connected to ambient air through a first port of the tank 2.

[0041] For example, the bladder 6 may comprise an opening or port provided with a suitable fitting which seals to the tank or to a conduit leading out of the tank 3. The bladder 6 may be attached to the tank 3 by any suitable means, such as by said fitting or conduit. The conduit may comprise a header fluidly connecting multiple bladders 6 to a port of the tank 3 exposed to atmospheric pressure. By fluidly connecting each bladder 6 to an outside of the tank 3 such that each bladder 6 is exposed to atmospheric pressure, the volume of each bladder adapts to changes of liquid volume in the tank 3. The use of a header inside the tank 3 enables use of only one port of the tank 3 for all bladders 6, thus simplifying production and assembly of the conservator device 1.

[0042] The tank 3 comprises a second port 7 adapted to provide a liquid connection between the remaining portion of the inner volume of the tank 3 and a liquid-filled volume of the electric induction device 2.

[0043] Here, the remaining portion refers to the portion of the inner volume of the tank 3 fluidly separated from the inner volume of the bladders 6.

[0044] The tank 3 may be formed in any suitable way, such as by welding together structural members of a suitable metal or plastic material, or using fiber-reinforced plastics. The tank 3 may be formed from two or more parts joined together using flanges and mechanical fasteners. The tank 3 may be an elongated body adapted to be installed with a longitudinal axis of the tank 3 oriented substantially horizontally. The elongated body may be cylindrical or any other suitable shape. The tank 3 is typically installed on top of the electrical induction device 2 such that gravity is able to force liquid from the tank 3 into the electrical induction device 2. It should be understood that the orientation of the tank 3 may vary slightly without departing from the scope of the invention. Generally, the tank should exhibit a certain minimum volume by design, and by orienting the tank horizontally, the total height of the installation is reduced.

[0045] The one or more primary 4 and / or secondary 5 wall members are adapted to enable liquid flow between the compartments C, CU, CL.

[0046] Liquid flow may be enabled by designing the wall members such that fluid may flow around the wall members, or by providing an array or through openings in the wall members, or by using a porous liquid-permeable material for the wall members (applies to both primary and secondary wall members).

[0047] In this embodiment, the one or more primary 4 and / or secondary 5 wall members are fluid-permeable but in other embodiments, any other configuration of the wall members 4, 5 could alternatively be used as long as they allow for liquid flow between the compartments C, CU, CL, as mentioned above.

[0048] In this embodiment, the primary 4 and secondary 5 wall members are made of porous material but in other embodiments they would have any other suitable configuration. For example, the primary 4 and secondary 5 wall members could comprise an array of through openings 9 providing said fluid-permeability, as shown in fig. 3.

[0049] In this embodiment, the primary 4 and secondary 5 wall members are plates but in other embodiments any other suitable form of the wall members may be used instead, such as a suitable sheet material.

[0050] In the embodiment shown in figs. 1-2, the at least one primary wall member 4 extends from an upper portion of the tank 3 towards a lower portion of the tank 3.

[0051] The at least one primary wall member 4 extends substantially vertically but may in other embodiments extend obliquely between an upper portion of the tank 3 and a lower portion of the tank 3.

[0052] The vertical extent is the extent when the conservator device is oriented in its intended orientation in use, which is typically evident by studying the position of the port for liquid (downwards) and the port for air to the bladder(s) (upwards).

[0053] Each primary wall member 4 covers a respective whole cross-section of the tank 3 but may in other embodiments cover only a portion of the cross-section of the tank. For example, for a cylindrical tank 3, each primary wall member may be substantially circular and thus cover the entire cross-section of the tank 3.

[0054] The primary wall members are attached to the tank by welding but may in other embodiments be attached in any other suitable way, such as by adhesive or by using mechanical fasteners.

[0055] The secondary wall members 5 are attached to the primary wall members 4 but may in other embodiments be attached to the tank 2 or to a combination of the tank 2 and the primary wall members 4.

[0056] In other embodiments (not shown in the figures), otherwise identical to the embodiments described above, the one or more secondary wall members 5 may be adapted to be vertically movable in response to varying liquid level in the tank 3 such that the vertical position of the one or more secondary wall member 5 is raised in response to rising liquid level, and such that the vertical position of the one or more secondary wall members 5 is lowered in response to falling liquid level.

[0057] The vertical position of the one or more secondary wall members 5 may be controlled in any suitable way, such as by being governed by a support mechanism, said support mechanism being powered by actuators controlled by an electronic control unit based on a signal from a liquid level sensor adapted to determine one or more liquid levels in the tank 3. Alternatively, the support mechanism comprises a buoyant body adapted to float in liquid in the tank 3 for controlling the vertical position of the one or more secondary wall members 5 based on a vertical position of the buoyant body. The support mechanism may be as simple as a buoyant body attached to the secondary wall member 5, or the buoyant body may be connected to the secondary wall members using any suitable mechanical system, for example comprising a linkage and / or wire.

[0058] The present invention also relates to a system S comprising an electric induction device 2 and the conservator device 1 according to any one of the preceding claims. The electric induction device 2 may be a transformer or a shunt reactor. Table of reference numerals1conservator device2electric induction device3tank4primary wall members5secondary wall members6bladder7first port of tank (for liquid)8second port of tank (for air)9array of through openingsVinner volume of tankCcompartmentsCUupper compartmentsCLlower compartments

Claims

1. A conservator device (1) for use with an electric induction device (2), said electric induction device (2) comprising a liquid-filled volume, and said conservator device comprising: a tank (3), one or more wall primary wall members (4) provided within an inner volume (V) of the tank (3), said one or more primary wall members (4) being adapted to horizontally divide the inner volume (V) of the tank into a plurality of compartments (C), one or more wall secondary wall members (5) provided within the inner volume (V) of the tank, said one or more secondary wall members (5)being adapted to vertically divide the inner volume (V) of the tank, or one or more of said compartments, into an upper compartment (CU) and a lower compartment (CL), wherein one or more of said upper compartments (CU) are provided with a respective bladder (6) inside the respective upper compartment (CU), each respective bladder (6) being attached to the tank (3) such that an inner volume of the bladder (6) is fluidly separated from a remaining portion of the inner volume (V) of the tank (3), and each bladder (6) being fluidly connected to ambient air through a first port (8) of the tank (3), and said tank (3) comprising a second port (7) adapted to provide a liquid connection between said remaining portion of the inner volume of the tank (3) and a liquid-filled volume of the electric induction device (2), wherein the one or more primary (4) and / or secondary (5) wall members are adapted to enable liquid flow between the compartments (C, CU, CL).

2. A conservator device (1) according to claim 1, wherein the one or more secondary wall members (5) are adapted to be vertically movable in response to varying liquid level in the tank (3) such that the vertical position of the one or more secondary wall member (5) is raised in response to rising liquid level, and such that the vertical position of the one or more secondary wall members (5) is lowered in response to falling liquid level.

3. A conservator device (1) according to claim 2, wherein the vertical position of the one or more secondary wall members (5) is governed by a support mechanism, said support mechanism being powered by actuators controlled by an electronic control unit based on a signal from a liquid level sensor adapted to determine one or more liquid levels in the tank (3), or said support mechanism comprising a buoyant body adapted to float in liquid in the tank (3) for controlling the vertical position of the one or more secondary wall members (5) based on a vertical position of the buoyant body.

4. The conservator device according to any one of claims 1-3, wherein the one or more primary (4) and / or secondary (5) wall members are fluid-permeable.

5. The conservator device (1) according to claim 4, wherein the primary (4) and secondary (5) wall member(s) is / are made of porous material.

6. The conservator device (1) according to claim 4, wherein the primary (4) and secondary (5) wall member(s) comprise an array of through openings (9) providing said fluid-permeability.

7. The conservator device (1) according to any one of the preceding claims, wherein primary (4) and secondary (5) wall members are plates.

8. The conservator device (1) according to claim any one of the preceding claims, wherein the at least one primary wall member (4) extends from an upper portion of the tank (3) towards a lower portion of the tank (3).

9. The conservator device (1) according to any one of the preceding claims, wherein the at least one primary wall member (4) extends substantially vertically.

10. The conservator device (1) according to any one of the preceding claims, wherein each primary wall member (4) covers a respective whole cross-section of the tank (3).

11. A system (S) comprising an electric induction device (2) and the conservator device (1) according to any one of the preceding claims.

12. A system (S) according to claim 11, wherein the electric induction device (2) is a transformer or a shunt reactor.

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