EP4672283A1

EP4672283A1 - Expansion vessel for use with an electric offshore induction device

Info

Publication number: EP4672283A1
Application number: EP24184044.6A
Authority: EP
Inventors: Lokman HOSAIN; Tor Laneryd; Jigar Narsinhbhai TANK; Joakim Johansson
Original assignee: Hitachi Energy Ltd
Current assignee: Hitachi Energy Ltd
Priority date: 2024-06-24
Filing date: 2024-06-24
Publication date: 2025-12-31
Also published as: WO2026002958A1

Abstract

A conservator device (1) for use with an electric induction device (2), said electric induction device comprising a liquid-filled volume. The conservator device (1) comprises: a tank (3), one or more wall members (4) provided within an inner volume of the tank (3), said one or more wall members (4) being adapted to horizontally divide the inner volume of the tank (3) into a plurality of compartments (C). One or more of said compartments (C) is provided with a respective barrier (6) being flexible and attached to the tank (3) such that the barrier (6) fluidly separates a dry portion of the inner volume of the tank (3) from a remaining portion of the inner volume of the tank (3), wherein each dry portion of the inner volume of the tank (3) is fluidly connected to ambient air by a first port (8) of the tank (3). The tank (3) comprising a second port (7) adapted to enable 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). Further, the one or more wall members (4) are liquid-permeable.

Description

Technical field

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

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 oxy-gen. 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.
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 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.

Summary

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 members provided within an inner volume of the tank. The one or more wall members are adapted to horizontally divide the inner volume of the tank into a plurality of compartments. One or more of said compartments are provided with a respective barrier. Each respective barrieris flexible and attached to the tank such that the barrier fluidly separates a dry portion of the inner volume of the tank from a remaining portion of the inner volume of the tank. Further, each dry portion of the inner volume of the tank is fluidly connected to ambient air by a first port of the tank. Accordingly, the remaining portion of the inner volume of the tank is typically all of the inner volume of the tank except for the volume occupied by the barrier(s) and air. The tank further comprises a second port adapted to enable 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 wall members are liquid-permeable.
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 the flexble barrier to deform, thus forcing air out of the tank and vice versa. The liquid is typically an insulation liquid, such as a suitable oil.
The barrier prevents air from mixing with liquid inside the tank. By horizontally dividing the inner volume into compartments using the wall members, movement of liquid within the tank is mitigated by the wall members, thus reducing sloshing motions of liquid inside the tank.
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 wall members upon acceleration of the tank.
The provision of multiple compartments reduces the size of each barrier needed and thus reduces its tendency to move upon sloshing, thus mitigating fatigue of the barrier. Reduced fatigue of the barrier mitigates rupture of the barrier. Rupture of the barrier would cause severe failure due to contamination with oxygen. Presence of oxygen in insulation oil will accelerate degradation and might irreversibly damage the insulation system and increase risk of fire hazard. To replace a barrier and decontaminate liquid/oil would be very costly in off-shore installations and cause severe consequences due to interruption in operation of the electrical induction device. Furthermore, mitigating sloshing of liquid in the tank reduces stress on the conservator and the electrical induction device caused by sloshing forces. Thus, a reduction of sloshing will increase system stability. Further, the sloshing movement is 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 wall member(s) may be made of porous material providing said liquid-permeability.
The porous material enables an even flow of liquid over the whole surface of each wall member.
Alternatively, the wall member(s) may comprise an array of through openings providing said liquid-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 one or more wall members may be plates.
The plates are easy to produce and provide a planar support for the barrier, thus reducing wear and risk of failure of the barrier. Plate-formed wall members also provide improved stiffness.
The at least one wall member may extend from an upper portion of the tank towards a lower portion of the tank.
The at least one 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 wall member may cover a respective whole cross-section of the tank.
By covering a whole cross-section of the tank, the wall member provides improved rigidity to the tank.
The barrier may comprise a bladder.
As an alternative, or compliment to a bladder, the barrier may comprise a diaphragm being attached to the tank around a circumferential portion of the respective diaphragm, said attachment being formed by a direct attachment between the tank and at least a portion of the respective diaphragm and/or by an attachment between the one or more wall members and least a portion of the respective diaphragm.
The walls of the bladder or the diaphragm provide said fluid separation, whilst enabling a variable volume on each side of the bladder or diaphragm to account for varying amounts of liquid and air in the tank.
A second aspect of the invention relates to a system comprising an electric induction device and the conservator device described above.
The electric induction device may be a transformer or a shunt reactor.

Brief description of drawings

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 in which the barrier comprises a bladder.
Fig. 2 shows a top view of the system device also shown in fig. 1.
Fig. 3 show an embodiment of a 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.
Fig. 6 shows a cross-sectional side view of a system comprising an electric induction device and a conservator device according to an embodiment in which the barrier comprises a diaphragm.
Fig. 7 shows a top view of the system device also shown in fig. 6.

Detailed description

Embodiments of the present invention will hereinafter be described with reference to the appended drawings.
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.
It is an object of the invention to improve longevity of the conservator device 1 when used at sea, i.e. in conditions at which the conservator device 1 is exposed to accelerations.
The conservator device 1 comprises a tank 3, and one or more wall wall members 4 provided within an inner volume V of the tank 3. The one or more wall members 4 are adapted to horizontally divide the inner volume V of the tank 3 into a plurality of compartments C.
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.
One or more of said compartments C are provided with a respective barrier 6 comprising a bladder.
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 forced 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 by a first port 8 of the tank 3.
For example, the bladder 6 may comprise an opening or port provided with a suitable fitting which seals to the tank 3 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 the first port 8 of the tank 3. 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 6 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 8 of the tank 3 for all bladders 6, thus simplifying production and assembly of the conservator device 1.
The tank 3 further comprises a second port 7 adapted to enable 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.
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.
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. 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 3 horizontally, the total height of the installation is reduced.
In the embodiment of figs. 1 2, 6 and 7, the wall member(s) is/are made of porous material providing said liquid-permeability. In other embodiments the wall members 4 could have any other suitable configuration. For example, the wall members 4 could comprise an array of through openings 5 providing said liquid-permeability, as shown in fig. 3.
In this embodiment, the wall members 4 are plates but in other embodiments any other suitable form of the wall members may be used instead, such as a suitable sheet material.
In this embodiment, the at least one wall member 4 extends from an upper portion of the tank 3 towards a lower portion of the tank 3.
In this embodiment, the at least one 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) 6 (upwards).
In this embodiment, each 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 3. For example, for a cylindrical tank 3, each wall member may be substantially circular and thus cover the entire cross-section of the tank 3.
The wall members are 4 attached to the tank 3 by welding but may in other embodiments be attached in any other suitable way, such as by adhesive or by using mechanical fasteners.
The embodiment shown in figs. 6 and 7 corresponds to the one of figs. 1 and 2, except for the barrier 6 comprising a diaphragm instead of a bladder. In this embodiment, only one diaphragm is shown but in other embodiments two or more diaphragms may be provided instead.
The diaphragm is attached to the tank 3 around a circumferential portion of the diaphragm. The attachment is formed by a direct attachment between the tank 3 and at least a portion of the respective diaphragm and/or by an attachment between the one or more wall members and least a portion of the respective diaphragm. Portions of two or more diaphragms may be interconnected or formed in one piece to provide a liquid seal between the diaphragms.

The present invention also relates to a system S comprising an electric induction device 2 and the conservator device 1 described above. The electric induction device 2 may be a transformer or a shunt reactor.

Table of reference numerals

1	conservator device
2	electric induction device
3	tank
4	wall members
5	array of through openings
6	barrier
7	second port of tank (for liquid)
8	first port of tank (for air)
V	inner volume of tank
C	compartments

Claims

A conservator device (1) for use with an electric induction device (2), said electric induction device comprising a liquid-filled volume, and
said conservator device (1) comprising:
a tank (3),

one or more wall members (4) provided within an inner volume of the tank (3),

said one or more wall members (4) being adapted to horizontally divide the inner volume of the tank (3) into a plurality of compartments (C),

one or more of said compartments (C) being provided with a respective barrier (6) being flexible and attached to the tank (3) such that the barrier (6) fluidly separates a dry portion of the inner volume of the tank (3) from a remaining portion of the inner volume of the tank (3), wherein each dry portion of the inner volume of the tank (3) is fluidly connected to ambient air by a first port (8) of the tank (3),

said tank (3) comprising a second port (7) adapted to enable 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 wall members (4) are liquid-permeable.
The conservator device according to claim 1, wherein the wall member(s) is/are made of porous material providing said liquid-permeability.
The conservator device according to claim 1, wherein the wall member(s) comprise an array of through openings providing said liquid-permeability.
The conservator device according to any one of claims 1-3, wherein the one or more wall members are plates.
The conservator device according to claim any one of claims 1-4, wherein the at least one wall member extends from an upper portion of the tank towards a lower portion of the tank.
The conservator device according to any one of claims 1-5, wherein the at least one wall member extends substantially vertically.
The conservator device according to any one of claims 1-6, wherein each wall member covers a respective whole cross-section of the tank.
The conservator device (1) according to any one of claims 1-7, wherein the barrier (6) comprises a bladder.
The conservator device (1) according to any one of the preceding claims, wherein the barrier (6) comprises a diaphragm being attached to the tank (3) around a circumferential portion of the respective diaphragm,
said attachment being formed by a direct attachment between the tank (3) and at least a portion of the respective diaphragm and/or by an attachment between the one or more wall members (4) and least a portion of the respective diaphragm.
An electric induction device comprising the conservator device according to any one of the preceding claims.
An electric induction device according to claim 10, wherein the electric induction device is a transformer or a shunt reactor.