EP4672284A1

EP4672284A1 - Equalizing tank for use with an electric offshore induction device

Info

Publication number: EP4672284A1
Application number: EP24184047.9A
Authority: EP
Inventors: Lokman HOSAIN; Tor Laneryd; Esa Virtanen
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: WO2026002438A1

Abstract

A conservator device (1) for use with an electric induction device (2), said electric induction device (2) comprising a liquid-filled volume. The conservator device (1) comprises a tank (3) and two or more diaphragms (6) provided inside the tank (3). Each diaphragm (6) is attached to the tank (3) around a circumferential portion of the respective diaphragm (6) such that the diaphragms (6) jointly divide the inner volume of the tank (3) into a first volume (V1) for liquid and a second volume (V2) for air. The tank (3) is provided with a first port (8) fluidly connecting the second volume (V2) to ambient air, and a second port (7) enabling fluid connection between the first volume (V1) and the liquid-filled volume of the electric induction device (2). Portions of one or more of said diaphragms (6) are attached to the tank (3) via a rigid support structure (4, 10, 11) attached to the tank (3).

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 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.

Summary

According to a first aspect of the invention, this and other objects are achieved by a conservator device according to claim 1 with alternative embodiments defined in the dependent claims. The conservator device comprises a tank, and two or more diaphragms provided inside the tank. Each diaphragm is attached to the tank around a circumferential portion of the respective diaphragm such that the diaphragms jointly divide the inner volume of the tank into a first volume for liquid and a second volume for air.
The diaphragms 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 diaphragm adapts its shape in response to liquid being forced into or out of the tank. Portions of the circumference of each diaphragm can be attached either directly to the tank or indirectly via some intermediate structure attached to the tank. Accordingly, the diaphragms are supported around a circumferential edge portion of each diaphragm, such movement of each diaphragm is controlled at the edge portion, thereby preventing diaphragms from scraping against each other or against the tank. This increases the lifetime of each diaphragm.
The conservator device further comprises one or more primary wall members provided within the first volume of the tank. The one or more primary wall members are adapted to horizontally divide the first volume into a plurality of compartments.
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.
The tank is provided with a first port fluidly connecting the second volume to ambient air, and a second port enabling fluid connection between the first volume and the liquid-filled volume of the electric induction device.
The conservator device is used to act as an expansion vessel 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 first volume of the tank of the conservator device, forcing air out of the second volume. The liquid is typically an insulation liquid, such as a suitable oil.
The diaphragms and any structures attaching them to the tank 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 motions of liquid inside the tank. The combination of diaphragm and local support of the diaphragm enables a variable liquid volume in the tank whilst preventing the diaphragm from rubbing against the tank or against itself, and thus reduces fatigue of the diaphragm membrane. Reduced fatigue of the diaphragm mitigates rupture of the diaphragm. Rupture of the diaphragm 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 diaphragm 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 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 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. A multitude of small holes with the same cross sectional area as a large hole will prevent fast fluid motion but allow slow fluid motion. Thus, provision a a fluid-permeable primary wall mitigates the effect of violent sloshing motion while still allowing the conservator to perform the function of receiving expanding liquid and again venting it back to the electric induction device
Portions of one or more of said diaphragms may be attached to the tank via the one or more of the primary wall members. Thereby, portions of the circumference of each diaphragm not directly attached to the tank will be attached to wall members extending between tank walls, such that the whole circumference of each diaphragm is supported.
The tank may be elongated and extend along a longitudinal axis, wherein the primary wall members are distributed along the longitudinal axis such that each compartment extends along a sub-portion of the length of the tank. The elongated tank may be cylindrical. The elongated shape enables a low total height of the conservator device when orienting the longitudinal axis horizontally. In use, the tank is typically positioned above the electric induction device, for example attached on top of the electric induction device.
The primary wall members may extend substantially perpendicularly to the longitudinal axis.
The primary wall members may be made of porous material providing said fluid-permeability.
Each one of the one or more primary wall members may comprises an array of through openings providing said fluid-permeability.
The one or more primary wall members may be plates.
The conservator device may further comprise one or more secondary wall members provided within the first volume, said one or more secondary wall members being adapted to vertically divide the first volume.
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 of the system may be a transformer or a shunt reactor.

Brief description of drawings

Figs. 1-8 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 a first embodiment.
Fig. 2 shows a top view of the system device also shown in fig. 1.
Fig. 3 shows a cross-sectional side view of a system comprising an electric induction device and a conservator device according to a second embodiment.
Fig. 4 shows a top view of the system device also shown in fig. 3.
Fig. 5 shows a shaded perspective view of the system also shown in figs. 3 and 4.
Fig. 6 shows a cross-sectional side view of a system comprising an electric induction device and a conservator device according to a third embodiment.
Fig. 7 shows a top view of the system device also shown in fig. 6.
Fig. 8 shows an embodiment of a wall member comprising an array of through openings.

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.
Three exemplary embodiments are shown in the appended figures. In all embodiments, the conservator device 1 is suitable for use with an electric induction device 2, said electric induction device 2 comprising a liquid-filled volume. The conservator device 1 comprises: a tank 3, at least one diaphragm 6 provided inside the tank 3, each diaphragm 6 being attached to the tank 3 around a circumferential portion of the respective diaphragm 6 such that the diaphragms 6 jointly divide the inner volume of the tank 3 into a first volume V1 for liquid and a second volume V2 for air. The conservator device 1 further comprises one or more primary wall members 4 provided within the first volume V1 of the tank 3, said one or more primary wall members 4 being adapted to horizontally divide the first volume V1 into a plurality of compartments C. The tank 3 is also provided with a first port 8 fluidly connecting the second volume V2 to ambient air, and a second port 7 enabling fluid connection between the first volume V1 and the liquid-filled volume of the electric induction device 2.
In embodiments in which more than one diaphragm 6 is used, a portion of each diaphragm 6 in the interface between adjacent diaphragms 6 needs to be supported by a suitable rigid support structure. The rigid support structure may comprise one or more primary wall members 4 and/or one or more separate support members 10 attached to the tank 3 and adapted to support the diaphragms. Such support members 10 are schematically illustrated in the embodiment of figs. 1 and 2 as a support plate 11, and in figs. 6 and 7 as beams, whereas the primary wall members 4 are used to provide support to the diaphragms 6 in the embodiment of figs. 3-5.
The illustrated support plate 11 has one opening for each diaphragm 6, but may in other embodiments have any suitable number of openings enabling liquid flow past the support plate, but not between the first volume V1 and the second volume V2 of the tank 3. At least a portion of the circumference of each diaphragm 6 is attached to the support plate 11. As shown in fig. 1, the support plate 11 is typically attached between two tank members together forming the tank 3, although any other suitable attachment of the support plate 11 to the tank 3 could alternatively be used instead. The support plate 11 seals to the tank 3 such that air cannot flow around the support plate 11, thereby fluidly separating the first volume V1 and the second volume V2.
If one or more support members 10 are used to support portions of the diaphragms 6, the primary wall portions 4 may be positioned anywhere suitable to mitigate sloshing, but when the primary wall members 4 are used to support portions of the diaphragms 6, the primary support members 10 must be positioned between diaphragms 6, such as in the embodiment of figs. 3-5.
The one or more primary wall members 4 are preferably liquid-permeable but may alternatively in other embodiments be designed to allow flow of liquid past the respective primary wall member 4, for example by letting the respective primary wall member 4 extend over only a portion of a cross-section of the tank 3 between a diaphragm 6 and a lower portion of the tank 3.
The liquid-permeability of the wall members enable a restricted flow of liquid through the whole primary wall member 4, thus mitigating any need of leaving a gap between the tank 3 and the respective primary wall member 4 for liquid to flow through and further enables improved damping of local pressure build-up by the primary wall members 4 upon acceleration of the tank 3.
As shown in figs. 3 and 5, portions of one or more of said diaphragms 6 may be attached to the tank 3 via the one or more of the primary wall members 4. By attaching portions of the diaphragms 6 to the tank 3 via the primary wall members 4, there is no variable size opening between the diaphragm 6 and each primary wall member 4 and thus flow of liquid past each primary wall member 4 is better controlled independently of the volume of liquid present in the conservator device 1. Further, fewer parts are needed, since there is no need for additional support members 10 when multiple diaphragms 6 are used and attached to the tank 3 via primary wall members 4. Also, the attachment between primary wall member 4 and diaphragm 6 mitigates wear between the primary wall members 4 and the diaphragms 6.
Although the tank 3 may have any suitable shape, the tank 3 is preferably elongated and extends along a longitudinal axis L. For elongated tanks 3, the primary wall members 4 are distributed along the longitudinal axis L such that each compartment C extends along a sub-portion of the length of the tank 3. In the embodiments of figs. 1-7, the tank 3 is cylindrical.
The primary wall members 4 extend substantially perpendicularly to the longitudinal axis L but may in other embodiments alternatively extend at an angle to the longitudinal axis L.
The primary wall members 4 are made of porous material providing said fluid-permeability but may in other embodiments, for example be provided with an array of through openings 9 providing said fluid-permeability, as shown in fig. 8. Alternatively, the primary wall members are adapted such that liquid is able flow around them, as mentioned above.
The one or more primary wall members 4 are plates but may in other embodiments have any other suitable configuration.
As shown in fig. 6, the conservator device may further comprise one or more secondary wall members 5 provided within the first volume V1. The one or more secondary wall members are adapted to vertically divide the first volume V1. In other embodiment, the secondary wall members 5 may alternatively be omitted or positioned elsewhere within the first volume V1, such as further down.

As shown in figs. 1, 3 and 6, it is further suggested to provide a system S comprising an electric induction device 2 and the above-described conservator device 1. The electric induction device 2 may be a transformer or a shunt reactor.

1	conservator device
2	electric induction device
3	tank
4	primary wall members
5	secondary wall members
6	diaphragm(s)
7	first port of tank (for liquid)
8	second port of tank (for air)
9	array of through openings
10	support member
11	support plate
V1	first volume of tank
V2	second volume of tank
C	compartments
S	system
L	longitudinal axis

Claims

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 (1) comprising:
a tank (3),

two or more diaphragms (6) provided inside the tank (3), each diaphragm (6) being attached to the tank (3) around a circumferential portion of the respective diaphragm (6) such that the diaphragms (6) jointly divide the inner volume of the tank (3) into a first volume (V1) for liquid and a second volume (V2) for air,

wherein the tank (3) is provided with a first port (8) fluidly connecting the second volume (V2) to ambient air, and a second port (7) enabling fluid connection between the first volume (V1) and the liquid-filled volume of the electric induction device (2), and

wherein portions of one or more of said diaphragms (6) are attached to the tank (3) via a rigid support structure (4, 10, 11) attached to the tank (3).
The conservator device (1) according to claim 1, further comprising one or more primary wall members (4) provided within the first volume (V1) of the tank (3), said one or more primary wall members (4) being adapted to horizontally divide the first volume (V1) into a plurality of compartments (C).
The conservator device (1) according to claim 2, wherein the one or more primary wall members (4) are liquid-permeable.
The conservator device (1) according to any one of claims 2-3, wherein portions of one or more of said diaphragms (6) are attached to the tank (3) at least via the one or more of the primary wall members (4).
The conservator device (4) according to any one of claims 2-4, wherein the tank (3) is elongated and extends along a longitudinal axis (L), wherein the primary wall members (4) are distributed along the longitudinal axis (L) such that each compartment (C) extends along a sub-portion of the length of the tank (3).
The conservator device (1) according to claim 5, wherein the primary wall members (4) extend substantially perpendicularly to the longitudinal axis (L).
The conservator device (1) according to any one of claims 2-6, wherein the primary wall members (4) are made of porous material providing said fluid-permeability.
The conservator device (1) according to any one of claims 2-6, wherein each one of the one or more primary wall members (4) comprises an array of through openings (9) providing said fluid-permeability.
The conservator device (1) according to any one of claims 2-8, wherein the one or more primary wall members (4) are plates.
The conservator device (1) according to any one of claims 1-9, further comprising one or more secondary wall members (5) provided within the first volume (V1), said one or more secondary wall members (5) being adapted to vertically divide the first volume (V1).
A system (S) comprising an electric induction device (2) and the conservator device (1) according to any one of the preceding claims.
A system (S) according to claim 11, wherein the electric induction (2) device is a transformer or a shunt reactor.