Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/08—Cooling; Ventilating
  • H01F27/10—Liquid cooling
  • H01F27/12—Oil cooling
  • H01F27/14—Expansion chambers; Oil conservators; Gas cushions; Arrangements for purifying, drying, or filling

Definitions

• 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.
• 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.
• the induction device comprises cellulose insulation with material properties that degrade in the presence of oxygen.
• 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.
• the conservator device can be sealed from the atmosphere and filled with nitrogen, in which case no flexible bladder or diaphragm is needed.
• 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.
• 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.
• An object of the present invention is thus to provide an improved conservator device suitable for offshore use.
• 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.
• 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.
• One or more of the upper compartments are provided with a respective bladder inside the respective upper compartment.
• 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.
• 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.
• 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).
• 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.
• the bladder prevents air from mixing with liquid inside the tank.
• the primary wall members 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.
• 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.
• 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.
• 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.
• the secondary wall members can indicate liquid level in the tank.
• 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.
• the secondary wall members and/or the primary wall members may be liquid-permeable.
• 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.
• the primary and secondary wall member(s) may be made of porous material.
• the porous material enables an even flow of liquid over the whole surface of each wall member.
• the primary and secondary wall member(s) may comprise an array of through openings providing said fluid-permeability.
• 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.
• 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.
• the at least one primary wall member may extend from an upper portion of the tank towards a lower portion of the tank.
• 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).
• Each primary wall member may cover a respective whole cross-section of the tank.
• the primary wall member By covering a whole cross-section of the tank, the primary wall member provides improved rigidity to the tank.
• 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.
• the electric induction device may be a transformer or a shunt reactor.
• 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.
• 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.
• 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.
• One or more of said upper compartments CU are provided with a respective bladder 6 inside the respective upper compartment CU.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• the one or more primary 4 and/or secondary 5 wall members are adapted to enable liquid flow between the compartments C, CU, CL.
• 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).
• 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.
• the primary 4 and secondary 5 wall members are made of porous material but in other embodiments they would have any other suitable configuration.
• 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 .
• 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.
• 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.
• 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.
• 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).
• 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.
• each primary wall member may be substantially circular and thus cover the entire cross-section of the tank 3.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Transformer Cooling (AREA)

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Citations (3)

• 2024
  • 2024-06-24 EP EP24184043.8A patent/EP4672282A1/fr active Pending
• 2025
  • 2025-06-24 WO PCT/EP2025/067694 patent/WO2026002954A1/fr active Pending

Patent Citations (3)

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