Tap changer assembly and transformer box assembly

Abstract

The present disclosure relates to a tap changer assembly (100), comprising a tap changer assembly housing (110) which completely surrounds a tap changer volume 10 and an overflow volume (12), respectively. The tap changer assembly (100) further comprises at least a portion of a tap changer (13) located in the tap changer volume (10). The tap changer volume (10) and the overflow volume (12) can be connected to each other via an overflow assembly (16). The overflow assembly (16) is such that when the pressure in the tap changer volume (10) is lower than a predetermined overflow pressure threshold, fluid communication between the tap changer volume (10) and the overflow volume (12) via the overflow assembly (16) is prevented, and when the pressure in the tap changer volume (10) is equal to or higher than the predetermined overflow pressure threshold, fluid communication between the tap changer volume (10) and the overflow volume (12) via the overflow assembly (16) is enabled. The tap changer volume (10) and the overflow volume (12) are aligned along an axis (Z), wherein the tap changer assembly housing (110) has a maximum internal cross-sectional area that surrounds the tap changer volume (10) and is orthogonal to the axis (Z). When fluid communication between the tap changer volume (10) and the overflow volume (12) via the overflow assembly (14) is enabled, at least 10% of the maximum internal cross-sectional area between the tap changer volume (10) and the overflow volume (12) is enabled for fluid communication via the overflow assembly (14). The present disclosure also relates to a transformer tank assembly (300), comprising a transformer tank (30) and a tap changer assembly (100) according to the above.

Description

Technical Field

[0001] The present disclosure relates to a tap changer assembly and a transformer tank assembly including the tap changer assembly. Background Art

[0002] The tap changer is used to control the output voltage of the transformer by providing the possibility of connecting or disconnecting additional turns in the transformer winding. The tap changer includes a set of fixed contacts that can be connected to a plurality of taps of the regulating winding of the transformer, wherein these taps are located at different positions in the regulating winding. By connecting or disconnecting different taps, the effective number of turns of the transformer can be increased or decreased, thereby adjusting the output voltage of the transformer. The tap changer is equipped with a housing filled with insulating oil. This housing is in turn installed in the transformer box so that a part of the tap changer housing is accessible from the outside of the transformer box.

[0003] In the event of a trip between the contacts within the tap changer housing, a short-circuit arc discharge of hundreds of thousands of amperes may be generated. This will instantly vaporize the surrounding insulating oil, which will send a dynamic pressure shock wave along the tap changer assembly housing, subsequently creating a significant overpressure within the housing. If the energy released is too much, the top cover (and possibly the bottom of the housing behind it) will be blown off and the oil will be pushed through the opening, potentially starting a dangerous transformer fire.

[0004] It is critical not to push the oil out of the case and to delay the fault as long as possible so that the circuit breaker has time to activate and stop the current that forms the arc.

[0005] Existing equipment relies on pressure relief devices (PRDs) or explosion relief valves that are configured for low pressure trip levels (slightly above the expected normal operating pressure). However, testing and field experience have shown that existing equipment is unable to fully depressurize under larger energy faults.

[0006] US2012 / 242443 relates to a device for preventing an on-load tap changer from exploding. The device comprises a rupture element which can rupture when the pressure in the tank exceeds a predetermined threshold.

[0007] WO 2007 / 009960 relates to a pressure relief device having an expansion chamber. Summary of the invention

[0008] It is therefore an object of the present disclosure to provide an improved tap changer assembly. More specifically, it is an object of the present disclosure to provide a tap changer assembly that is capable of handling large and rapid pressure increases (e.g., pressure increases caused by tripping) inside the tap changer assembly. Another object of the present disclosure is to provide a transformer tank assembly including the tap changer assembly.

[0009] According to a first aspect of the present disclosure, a tap changer assembly is provided, comprising a tap changer assembly housing that completely surrounds a tap changer volume and an overflow volume, respectively. The tap changer assembly also includes at least a portion of the tap changer located in the tap changer volume. The tap changer volume and the overflow volume can be connected to each other via an overflow assembly. The overflow assembly is such that when the pressure in the tap changer volume is lower than a predetermined overflow pressure threshold, fluid communication between the tap changer volume and the overflow volume via the overflow assembly is blocked. When the pressure in the tap changer volume is equal to or higher than the predetermined overflow pressure threshold, fluid communication between the tap changer volume and the overflow volume via the overflow assembly is enabled. The tap changer volume and the overflow volume are aligned along an axis. The tap changer assembly housing has a maximum internal cross-sectional area that surrounds the tap changer volume and is perpendicular to the axis. When fluid communication between the tap changer volume and the overflow volume via the overflow assembly is enabled, at least 10% of the area of ​​the maximum internal cross-sectional area between the tap changer volume and the overflow volume is enabled for fluid communication via the overflow assembly.

[0010] The tap changer assembly housing typically encloses at least a portion of the tap changer (e.g., a shunt switch and / or a tap selector) within the tap changer volume. The tap changer assembly housing may be mounted in the transformer tank such that at least a portion of the tap changer assembly housing is accessible from outside the transformer tank.

[0011] The overflow volume is also surrounded by the tap changer assembly housing and can be connected to the tap changer volume via the overflow assembly. If a trip occurs in the tap changer volume, the pressure in the tap changer volume will increase rapidly. If the pressure exceeds a predetermined overflow pressure threshold, a fluid connection between the tap changer volume and the overflow volume via the overflow assembly is enabled. Thereby, the pressure in the tap changer volume is released into the overflow volume, so that the overpressure is at least not immediately released to the outside of the tap changer assembly housing.

[0012] In order to quickly provide pressure relief between the tap changer volume and the overflow volume, it is desirable that a relatively large area between the tap changer volume and the overflow volume be enabled for fluid communication via the overflow assembly.

[0013] Optionally, the tap changer assembly housing is such that when the pressure in the tap changer volume is below a predetermined precautionary pressure threshold, fluid communication between the tap changer volume and the environment surrounding the tap changer volume is prevented. The predetermined precautionary pressure threshold is greater than a predetermined overflow pressure threshold. When the pressure in the tap changer volume equals or exceeds the predetermined precautionary pressure threshold, fluid communication between the tap changer volume and the environment surrounding the tap changer volume is enabled.

[0014] As described above, the predetermined precautionary pressure threshold is selected such that it is greater than the predetermined overflow pressure threshold. Thus, in the event of an overpressure in the tap changer volume, the pressure is first released into the overflow volume. If, for example, the pressure in the tap changer volume and / or in the overflow volume increases more, the pressure is released into the surroundings of the tap changer volume. If the tap changer assembly housing is mounted together with the transformer tank, the tap changer volume can be at least partially mounted inside the transformer tank, so that the surroundings of the tap changer volume are the environment inside the transformer tank. The purpose of the predetermined precautionary pressure threshold is to release the overpressure in the tap changer volume and to delay the second additional step of the pressure increase in the overflow volume.

[0015] Optionally, when pressure in the tap changer volume equals or exceeds a predetermined precautionary pressure threshold, fluid communication between the tap changer capacity and the environment surrounding the tap changer volume is enabled by allowing a rupture in a tap changer assembly housing completely surrounding the tap changer volume.

[0016] Thus, the tap changer assembly housing may be configured and designed such that when the pressure in the tap changer volume exceeds a predetermined preventive pressure threshold, the portion at least partially surrounding the tap changer volume will rupture and release pressure to the surrounding environment of the tap changer volume. The tap changer assembly housing (for example) may have a reinforced bottom and flexible side walls. A flexible tap changer assembly housing will take longer to reach the predetermined preventive pressure threshold than a rigid tap changer assembly housing. Purely by way of example, a portion of the tap changer assembly housing that at least partially surrounds the tap changer volume and is intended to be positioned in the aforementioned transformer tank may be adapted to rupture when the pressure in the tap changer volume equals or exceeds the predetermined preventive pressure threshold. Purely by way of example, a portion of the tap changer assembly housing that at least partially surrounds the tap changer volume may include a wall portion having a weakened portion that causes the wall portion to rupture at a pressure equal to or exceeding the predetermined preventive pressure threshold.

[0017] Optionally, the tap changer assembly further comprises a pressure relief assembly connected to the overflow volume. The pressure relief assembly is such that when the pressure in the overflow volume is below a predetermined relief pressure threshold, fluid communication between the overflow volume and the surrounding environment of the overflow volume via the pressure relief assembly is prevented. The predetermined relief pressure threshold is greater than a predetermined overflow pressure threshold. When the pressure in the overflow volume is equal to or exceeds the predetermined relief pressure threshold, fluid communication between the overflow volume and the surrounding environment of the overflow volume via the pressure relief assembly is enabled.

[0018] Since the predetermined release pressure threshold is greater than the predetermined overflow pressure threshold, the overflow volume will contain overpressure until the pressure in the overflow volume reaches the predetermined release pressure threshold, at which point the pressure will be released to the surroundings of the overflow volume. If the tap changer assembly housing is mounted together with the transformer tank, the overflow volume is usually at least partially mounted outside the transformer tank. Thus, the surroundings of the overflow volume may be the environment outside the transformer tank. The purpose of the predetermined release pressure threshold is to provide an additional means for releasing overpressure in the tap changer volume (particularly overpressure in the overflow volume) to prevent an explosion of the overflow volume.

[0019] Optionally, the predetermined relief pressure threshold is greater than the predetermined prevention pressure threshold.

[0020] Thus, fluid communication between the overflow volume and the surroundings of the overflow volume via the pressure relief assembly can be enabled only after fluid communication between the tap changer volume and the surroundings of the tap changer volume has been enabled.

[0021] Optionally, the overflow assembly includes a fluid passageway that is closed by the biased cover when fluid communication between the tap changer volume and the overflow volume is blocked. The fluid passageway is open when fluid communication between the tap changer volume and the overflow volume is enabled.

[0022] The offset cover may cover an area equal to or greater than 50%, preferably greater than 90%, of the maximum internal cross-sectional area of ​​the tap changer assembly housing. A spring element (e.g., a spring bolt) may be arranged around an outer edge of the offset cover to urge it against the fluid passage. The spring bolt is configured to enable fluid communication via the fluid passage when the pressure in the tap changer volume is equal to or greater than a predetermined overflow pressure threshold. The spring bolt arranged around the outer edge of the offset cover allows a large area of ​​the fluid passage to be quickly opened to enable fluid communication between the tap changer volume and the overflow volume.

[0023] Optionally, the overflow assembly comprises a fluid passage which is closed by a rupture disk when fluid communication between the tap changer volume and the overflow volume is blocked.The rupture disk is adapted to rupture when the pressure in the tap changer volume is equal to or above a predetermined overflow pressure threshold.

[0024] A rupture disk is a device designed to quickly relieve pressure if it exceeds a predetermined threshold.

[0025] According to a second aspect of the present disclosure, a transformer tank assembly is provided, comprising a transformer tank and a tap changer assembly as defined above. The tap changer assembly housing is assembled with the transformer tank such that at least a portion of the tap changer volume is arranged inside the transformer tank.

[0026] Optionally, the surroundings of the tap changer volume are at least partially located inside the transformer tank, such that a breach in the tap changer assembly housing completely surrounding the tap changer volume results in fluid communication between the tap changer volume and the transformer tank interior.

[0027] Optionally, the tap changer assembly housing is assembled with the transformer tank such that at least a portion of the overflow volume is arranged outside the transformer tank.

[0028] Optionally, the surrounding environment of the overflow volume is an environment outside the transformer tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Further objects, advantages, and features of the present disclosure will become apparent from the following description of one or more embodiments with reference to the accompanying drawings, in which:

[0030] FIG. 1 shows a schematic side view of a prior art tap changer assembly.

[0031] FIG. 2 illustrates a pressure release sequence of the prior art tap changer assembly of FIG. 1 .

[0032] Figure 3 A schematic side view of a tap changer assembly according to the present disclosure is shown.

[0033] Figure 4 Shows Figure 3 Pressure relief sequence of the tap-changer assembly. DETAILED DESCRIPTION

[0034] The present disclosure is developed in more detail below with reference to the accompanying drawings which show examples of embodiments. The present disclosure should not be considered limited to the examples of embodiments described. Throughout the description, the same reference numerals refer to the same elements.

[0035] FIG1 shows a schematic side view of a prior art tap changer assembly 100′, which includes a tap changer volume 10′ (in which at least a portion of a tap changer 13′ is enclosed). The tap changer assembly 100′ can be assembled with a transformer tank 30, which does not constitute a part of the tap changer assembly 100′. The transformer tank 30 is represented in the figure by only a portion of the wall surrounding the transformer tank volume. In practice, the transformer tank 30 accommodates a transformer (not shown), which can be immersed in insulating oil inside the transformer tank 30. The tap changer assembly 100′ is usually mounted on the wall of the transformer tank 30 so that a portion of the tap changer assembly 100′ can be accessed from the outside 32 of the transformer tank 30. At least a portion of the tap changer 13′ is further electrically connected to the transformer inside 34 of the transformer tank 30 (i.e., inside the transformer tank volume). The tap changer allows increasing or decreasing the effective number of turns of the transformer winding, thereby adjusting the output voltage of the transformer.

[0036] On the outside of the transformer tank 30, the tap changer volume 10' may be sealed by a reinforced top cover 11' that includes a pressure relief device (PRD), such as a spring biased pressure relief device and / or a bursting disc or explosion proof valve. In the event of a trip between contacts within the tap changer volume 10', a short circuit arc discharge of several hundred kiloamperes may be generated. This will immediately vaporize the surrounding insulating oil and send a dynamic pressure shock wave along the tap changer volume 10', followed by a significant overpressure within the tap changer volume 10'. If the released energy is too much, the top cover 11' (behind which the bottom of the housing may be) will be blown out and the oil will be pushed through the opening, thereby potentially starting a dangerous transformer fire. The prior art tap changer assembly 100' with a pressure relief device shown in FIG. 1 is configured for a low pressure trip level slightly above the expected normal operating pressure. In the event of a larger energy fault, it is not possible to fully depressurize the tap changer volume 10'.

[0037] As shown in FIG. 2 , in the event of a short circuit and overpressure, a first pressure relief 1 ′ is performed to the outside 32 of the transformer tank 30 through the pressure relief device, and then a second pressure relief 2 ′ may be performed to the transformer tank.

[0038] Figure 3 A schematic side view of a tap changer assembly 100 according to the present disclosure is shown. The tap changer assembly 100 comprises a tap changer assembly housing 110 which completely surrounds a tap changer volume 10 and an overflow volume 12, respectively. The tap changer assembly 100 further comprises at least a portion of a tap changer 13 located in the tap changer volume 10. The tap changer volume 10 and the overflow volume 12 may be connected to each other via an overflow assembly 14. The overflow assembly 14 is configured such that when the pressure in the tap changer volume 10 is below a predetermined overflow pressure threshold, fluid communication between the tap changer volume 10 and the overflow volume 12 via the overflow assembly 14 is prevented. When the pressure in the tap changer volume 10 is equal to or above the predetermined overflow pressure threshold, fluid communication between the tap changer volume 10 and the overflow volume 12 via the overflow assembly 14 is enabled.

[0039] The overflow assembly 14 may include a fluid passage 16 that may be closed by a biased cover 140 when fluid communication between the tap changer volume 10 and the overflow volume 12 is blocked. When fluid communication between the tap changer volume 10 and the overflow volume 12 is enabled, the fluid passage 16 is open.

[0040] When fluid communication between the tap changer volume 10 and the overflow volume is blocked, the fluid passage 16 may alternatively be closed by a rupture disk (not shown). The rupture disk may be adapted to rupture when the pressure in the tap changer volume 10 is equal to or above a predetermined overflow pressure threshold. The rupture disk is designed to quickly release pressure when the pressure exceeds a predetermined threshold, but requires replacement after having been triggered.

[0041] The tap changer volume 10 and the overflow volume 12 may be aligned along the axis Z. The tap changer assembly housing 110 may have a maximum internal cross-sectional area that surrounds the tap changer volume 10 and is perpendicular to the axis Z. Figure 3 In the embodiment of the present invention, the tap changer volume 10 is illustrated as a prismatic volume along the axis Z. However, it is also conceivable that the tap changer volume 10 may be non-prismatic, so that the cross section of the tap changer volume 10 orthogonal to the axis Z may vary. In any case, the maximum internal cross-sectional area of ​​the tap changer assembly housing 110 is the maximum internal cross-sectional area surrounding the tap changer volume 10.

[0042] When fluid communication between the tap changer volume 10 and the overflow volume 12 via the overflow assembly 14 is enabled, at least 10% of the cross-sectional area between the tap changer volume 10 and the overflow volume 12 is enabled for fluid communication via the overflow assembly 14. By providing a relatively large area for fluid communication via the overflow assembly 14, it is ensured that the pressure in the tap changer volume 10 can be quickly released into the overflow volume 12.

[0043] The biasing cover 140 may cover an area equal to or greater than 50%, preferably greater than 90%, of the maximum internal cross-sectional area of ​​the tap changer assembly housing 10. Spring bolts 142 may be arranged around the outer edge of the biasing cover 140 to urge it against the fluid passage 16. The spring bolts 142 are adapted to allow the biasing cover 140 to open the fluid passage 16 and enable fluid communication via the fluid passage 16 when the pressure in the tap changer volume 10 is equal to or greater than a predetermined overflow pressure threshold. The use of spring bolts arranged around the outer edge of the biasing cover, rather than a hinged cover, allows a relatively large area of ​​the fluid passage to be quickly opened, thereby enabling fluid communication between the tap changer volume 10 and the overflow volume 12. Other biasing means (not shown) may be used to urge the cover 140 to seal the fluid passage 16 instead of or in addition to the above-mentioned spring bolts 142 when the pressure in the tap changer volume 10 is below the predetermined overflow pressure threshold. Purely by way of example, such biasing means may be obtained by a magnetic element (not shown) or a sealing member which biases the cover 140 to seal the fluid passage 16 by means of gravity.

[0044] The tap changer assembly housing 110 may also be adapted such that fluid communication between the tap changer volume 10 and the surroundings of the tap changer volume 10 is prevented when the pressure in the tap changer volume 10 is below a predetermined precautionary pressure threshold, wherein the predetermined precautionary pressure threshold is greater than a predetermined overflow pressure threshold. When the pressure in the tap changer volume 10 is equal to or exceeds the predetermined precautionary pressure threshold, fluid communication between the tap changer volume 10 and the surroundings of the tap changer volume 10 is enabled.

[0045] The tap changer volume 10 may comprise a reinforced surface 18, for example an end surface (eg a reinforced bottom) of the tap changer volume 10. The reinforced surface 18 may be arranged perpendicular to the Z axis.

[0046] A portion of the tap changer assembly housing 110 that surrounds the tap changer volume 10 may be provided with a flexible wall. The flexible wall may be made, for example, of fiberglass. The flexible wall of the tap changer volume 10 may have a cylindrical shape and may engage with the reinforcing surface 18 at an interface between the flexible wall and the reinforcing surface 18. Compared to a rigid wall, the flexible wall may delay the point in time at which a specific pressure (e.g., a predetermined overflow pressure threshold or a predetermined prevention pressure threshold) is reached. More time may allow the circuit breaker to disconnect the current and extinguish the arc that generates the overpressure. Thus, further pressure release from the tap changer volume 10 may not be required.

[0047] When the pressure in the tap changer volume 10 equals or exceeds a predetermined precautionary pressure threshold, fluid communication between the tap changer volume 10 and the surrounding environment of the tap changer volume 10 can be enabled by allowing a tap changer assembly housing 110 (e.g., a flexible wall surrounding the tap changer volume 10) that completely surrounds the tap changer volume 10 to rupture. The connection between the flexible wall and the reinforced surface 18 can be adapted to rupture when the pressure in the tap changer volume 10 equals or exceeds the predetermined precautionary pressure threshold. Thus, although purely by way of example, the surrounding environment of the tap changer volume can be at least partially inside the transformer tank 30. The flexible wall and the reinforced surface 18 can be adapted such that a rupture in the tap changer assembly housing 110 that completely surrounds the tap changer volume 10 results in fluid communication between the tap changer volume 10 and the interior of the transformer tank 30.

[0048] The tap changer assembly 100 may further include a pressure relief assembly 19 connected to the overflow volume 12. The pressure relief assembly 19 is such that when the pressure in the overflow volume 12 is below a predetermined relief pressure threshold, fluid communication between the overflow volume and the surrounding environment of the overflow volume 12 via the pressure relief assembly 19 is prevented. The predetermined relief pressure threshold is greater than the predetermined overflow pressure threshold. When the pressure in the overflow volume 12 is equal to or exceeds the predetermined relief pressure threshold, fluid communication between the overflow volume 12 and the surrounding environment of the overflow volume 12 via the pressure relief assembly 19 is enabled.

[0049] Since the predetermined release pressure threshold is greater than the predetermined overflow pressure threshold, the overflow volume will contain the overpressure until the pressure in the overflow volume reaches the predetermined release pressure threshold, at which time the pressure will be released to the surroundings of the overflow volume. The predetermined overflow pressure threshold set by the pressure relief assembly 19 is higher than the conventional pressure relief device included in the top cover 11' in Figures 1 and 2. The purpose of the predetermined release pressure threshold is to provide a further delay to release the overpressure in the tap changer volume 10 (especially the overflow volume 10) to prevent an explosion of the overflow volume 12 (which may cause oil to leak into the surroundings of the overflow volume 12).

[0050] The predetermined release pressure threshold may be greater than the predetermined prevention pressure threshold.Thus, fluid communication between the overflow volume 12 and its surroundings via the pressure relief assembly 19 can be enabled only after fluid communication between the tap changer volume 10 and its surroundings has been enabled.

[0051] Figure 3 A second embodiment of the present disclosure is also shown. A transformer tank assembly 300 is provided, comprising a transformer tank 30 (only partially shown) and a tap changer assembly 100 as described above. The tap changer assembly housing 110 is assembled with the transformer tank 30 such that at least a portion of the tap changer volume 10 is arranged inside the transformer tank, i.e., in the interior 34 of the transformer tank 30. When fluid communication between the tap changer volume 10 and the surrounding environment of the tap changer volume 10 is enabled, it can be defined as fluid communication between the tap changer volume 10 and the interior 34 of the transformer tank 30.

[0052] The tap changer assembly housing 110 can be assembled with the transformer tank 30 so that at least a portion of the overflow volume 12 is arranged outside the transformer tank, that is, arranged outside 32 of the transformer tank 30. Therefore, the surrounding environment of the overflow volume 12 can be defined as the environment outside the transformer tank 30.

[0053] Figure 4 Shows Figure 3In the event of a short circuit and overpressure, when the pressure in the tap changer volume 10 is equal to or higher than a predetermined overflow pressure threshold, a first pressure release 1 occurs by enabling fluid communication from the tap changer volume 10 to the overflow volume 12 via the overflow assembly 14 (which may be a biased cover 140).

[0054] When the pressure in the tap changer volume 10 equals or exceeds a predetermined precautionary pressure threshold, the second pressure release 2 may occur by enabling fluid communication between the tap changer volume 10 and the surrounding environment of the tap changer volume 10. As described above, such fluid communication may be achieved by a rupture in the tap changer assembly housing 110.

[0055] In the case of very high overpressure, when the pressure in the overflow volume 12 equals or exceeds a predetermined release pressure threshold, a third pressure relief 3 may be performed by enabling fluid communication between the overflow volume 12 and the surrounding environment of the overflow volume 12 via the pressure relief assembly 19. To avoid damage and personal injury, such fluid communication may be directed by a conduit to control the discharge of, for example, transformer oil away from areas near the overflow volume 12 that may be occupied by people.

[0056] By providing a sequence of pressure release events, dangerous leakage of oil outside the transformer tank 30 can be avoided, and transformer fires can be prevented. By delaying / extending the overpressure development time, time can also be provided to allow the circuit breakers of at least a portion of the tap changer 13 to disconnect the current and extinguish the arc to stop the increase of overpressure. In addition, since at least each of the first pressure release 1 and the second pressure release 2 can be performed without any leakage to the outside of the transformer tank assembly 300, the above process means that the risk of fluid leakage from the transformer tank assembly 300 is appropriately low.

[0057] The sequence can be established by ensuring that the predetermined relief pressure threshold is greater than the predetermined overflow pressure threshold and the predetermined prevention pressure threshold. In addition, the predetermined prevention pressure threshold is greater than the overflow pressure threshold.

[0058] The transformer tank assembly 300 and / or the tap changer assembly 100 may further include an oil conservator (not shown) which can be fluidly connected to the transformer tank 30 and / or the overflow volume 12 via a conduit (not shown). The conduit may include a gate valve, a sensor, and a control unit such that when the sensor detects a predetermined overpressure in the tap changer assembly 100, the control unit disables fluid communication between the oil conservator and the transformer tank 30 and / or to the overflow volume 12. Thereby, it may be ensured that in the unlikely event that the overflow volume 12 ruptures due to overpressure, oil is prevented from leaking to the outside 32 of the transformer tank 30.

Claims

1. A tap changer assembly (100), comprising a tap changer assembly housing (110), the tap changer assembly housing completely enclosing a tap changer volume (10) and an overflow volume (12), the overflow volume being separated from the surrounding environment of the overflow volume via the tap changer assembly housing, the tap changer assembly (100) further comprising at least a portion of a tap changer (13) located in the tap changer volume (10), the tap changer volume (10) and the overflow volume (12) being connectable to each other via an overflow assembly (14), It is characterized in that The overflow assembly (14) enables: - in the event that the pressure in the tap changer volume (10) is less than a predetermined overflow pressure threshold, fluid communication between the tap changer volume (10) and the overflow volume (12) via the overflow assembly (14) is prevented, and - in case the pressure in the tap changer volume (10) is equal to or higher than the predetermined overflow pressure threshold, fluid communication between the tap changer volume (10) and the overflow volume (12) via the overflow assembly (14) is enabled, wherein the tap changer volume (10) and the overflow volume (12) are aligned along an axis (Z), wherein the tap changer assembly housing (110) has a maximum internal cross-sectional area which surrounds the tap changer volume (10) and is orthogonal to the axis (Z), and wherein, when fluid communication between the tap changer volume (10) and the overflow volume (12) via the overflow assembly (14) is enabled, the maximum internal cross-sectional area is ) and the overflow volume (12) is enabled for fluid communication via the overflow assembly (14), and wherein the overflow assembly (14) includes a fluid passage (16) which is closed by a biasing cover (140) in case fluid communication between the tap changer volume (10) and the overflow volume (12) is prevented, and which is open in case fluid communication between the tap changer volume (10) and the overflow volume (12) is enabled, The tap changer assembly (100) further comprises a pressure release assembly (19), the pressure release assembly being arranged on the tap changer assembly housing and connected to the overflow volume (12), the pressure release assembly (19) enabling: - fluid communication between the overflow volume (12) and the surrounding environment of the overflow volume (12) via the pressure relief assembly (19) is prevented in the event that the pressure in the overflow volume (12) is below a predetermined release pressure threshold, the predetermined release pressure threshold being greater than the predetermined overflow pressure threshold, and - In case the pressure in the overflow volume (12) equals or exceeds the predetermined relief pressure threshold, fluid communication between the overflow volume (12) and the surrounding environment of the overflow volume (12) via the pressure relief assembly (19) is enabled.

2. The tap changer assembly (100) according to claim 1, wherein: The tap changer assembly housing (110) enables: - fluid communication between the tap changer volume (10) and the environment surrounding the tap changer volume (10) is prevented in case the pressure in the tap changer volume (10) is below a predetermined prevention pressure threshold, the predetermined prevention pressure threshold being greater than the predetermined overflow pressure threshold, and - In case the pressure in the tap changer volume (10) is equal to or exceeds the predetermined precautionary pressure threshold, fluid communication between the tap changer volume (10) and the surroundings of the tap changer volume (10) is enabled.

3. The tap changer assembly (100) according to claim 2, wherein: In case the pressure in the tap changer volume (10) equals or exceeds the predetermined precautionary pressure threshold, fluid communication between the tap changer volume (10) and the environment surrounding the tap changer volume (10) is enabled by allowing a rupture in the tap changer assembly housing (110) that completely surrounds the tap changer volume (10).

4. The tap changer assembly (100) according to claim 2, wherein the predetermined release pressure threshold is greater than the predetermined prevention pressure threshold.

5. A transformer tank assembly (300), comprising a transformer tank (30) and a tap changer assembly (100) according to any one of the preceding claims, wherein the tap changer assembly housing (110) is assembled with the transformer tank (30) so that at least a part of the tap changer volume (10) is arranged inside the transformer tank (30).

6. The transformer tank assembly (300) of claim 5, when dependent on claim 3, wherein: The environment surrounding the tap changer volume (10) is at least partially located inside the transformer tank (30), so that the breach in the tap changer assembly housing (110) completely surrounding the tap changer volume (10) results in fluid communication between the tap changer volume (10) and the interior (34) of the transformer tank (30).

7. A transformer tank assembly (300), comprising a transformer tank (30) and a tap changer assembly (100) according to any one of claims 1 to 4, wherein the tap changer assembly housing (110) is assembled with the transformer tank (30) so that at least a portion of the overflow volume (12) is arranged outside the tank.

8. The transformer tank assembly (300) of claim 7, when dependent on claim 1, wherein: The surrounding environment of the overflow volume (12) is the environment outside the transformer tank (30).

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