FIELD OF THE INVENTION

The present invention relates to the field of electric power, especially high voltage electric power generation, such as wind turbines. Specifically, the invention relates to an external housing for high voltage enclosure for providing a safe housing of gas-isolated high voltage switchgear.

BACKGROUND OF THE INVENTION

In a typical wind turbine suited for generating electric power to an electric grid, a gas-isolated High Voltage (HV) switchgear is necessary. Such switchgear provides a safety risk, since harmful gases serving as electric isolation in such HV switchgear may leak. Further, in case of a fault, a possible blowout leading to a powerful pressure wave may involve health risks for persons present near the HV switchgear. For these reasons, the HV switchgear needs to placed away from immediate presence of unqualified persons. Thus, for this reason placing the HV switchgear in the tower of a wind turbine may require safety precautions in the form of further encapsulation or elaborate safety procedures before entering the tower. Moreover, this would impose limitations for personel without the necessary qualifications for working near HV equipment in accessing the wind turbine tower.

Placing the HV switchgear in a separate external enclousure outside the wind turbine tower often involves substantial costs, and complicates construction work involved in building a wind turbine system, e.g. transport or on-site building of a HV switchgear enclosure.

SUMMARY OF THE INVENTION

Thus, according to the above description, it is an object of the present invention to provide a wind turbine system with a safe enclosure for the gas-isolated HV switchgear, and which is still easy to handle in the construction process, and which can be provided in a low cost version. In a first aspect, the invention provides a housing serving to enclose a gas- insulated HV switchgear with a blowout outlet, wherein the housing is arranged for position on the ground, wherein the housing comprises

- a base arranged for mounting at least partly below ground level, the base forming a compartment with an upwards facing opening, and

- an enclosure arranged for mounting on the base, wherein the enclosure forms an enclosed space, the enclosure comprising

- at least one wall element,

- a floor with an opening serving to connect to the compartment of the base via the upwards facing opening of the base, wherein the high voltage switchgear is arranged to be mounted on the floor so as to cover the opening of the floor, and wherein the blowout outlet of the high voltage switchgear is connected with the compartment of the base via the opening of the floor,

- a top part comprising a ceiling element and a roof element forming a compartment with a blowout opening to the environment, and

- a blowout channel connecting the compartment at the base and the compartment of the top part

wherein the base and the enclosure are seperable until mounting of the enclosure.

Such housing is advantageous for increasing safety in wind turbines, where nominal voltage levels of 10-35 kV, or even up to 66 kV, is handled by gas- isolated switchgear, where both gas leakages and blowouts in case of failures cause risks of health problems for unprotected persons present near such HV switchgear. Enclosing the HV switchgear in a housing placed outside the wind turbine tower, e.g. a distance away from the tower, safety in the tower is increased. By providing a separate housing for the HV switchgear, preferably with a lockable door, it can be ensured that only qualified persons come near the HV switchgear. Moreover, personnel without HV equipment qualification can enter the tower.

The housing can be formed by low cost elements with compact dimensions, and still provide sufficient protection in case of a blowout caused by a fault in the HV switchgear. This is due to the blowout path from the HV switchgear blowout outlet, down to the compartment in the base, via the blowout channel, e.g. along a wall of the enclosure, and to yet another compartment formed between the ceiling element and the roof element. Thus, the blowout pressure is released via two compartments forming chambers that help to reduce the pressure before being let out to the environment.

Further, the blowout opening to the environment can be placed well above ground level due to this opening being formed at the top part of the housing. Even further, the first chamber will typically be located below ground level. This helps to increase safety for persons located near the housing in case of a blowout.

The housing is further advantageous, since the proposed housing can be transported easily on a road vehicle, since the enclosure and base can be separated for transport and assembled on-site. Especially, the base can be positioned inside the partly assembled enclosure for transport, thereby serving to limit the outer dimensions of the housing, especially the height.

Still further, mounting the base in the ground, the necessary HV cables can be placed below ground level and enter via the base and up to the HV switchgear in the enclosure. The cables can be mounted in the base before or after the HV switchgear is mounted in the enclosure, thus relaxing the construction process.

It is to be understood that the housing can be used for enclosing HV switchgear for wind turbines, as well as other applications involving a gas-isolated high voltage switchgear, e.g. for electricity generators and utilities for other types of sustainable energy sources such as PV, waves etc.

By "High Voltage" is understood an electric AC voltage having an RMS value higher than 1 kV. In typical embodiments for wind turbines, the HV switchgear is capable of handling AC RMS voltages of at least 10 kV, such as 10-40 kV, or even up to 66 kV or 72.5 kV.

In the following, preferred embodiments and features will be described.

The blowout channel may be formed by an element being separate from the wall elements, or one wall element can form part of the blowout channel. The blowout channel can be connected to the base compartment via the opening of the floor serving to connect the blowout outlet of the HV switchgear, or a separate smaller opening in the floor.

The base may be arranged for being positioned inside the enclosure during transportation of the housing, so as to limit the outer dimensions of the housing for transport, e.g. for road transport. The base may be formed by a monolithic concrete element or made of another material suitable for being positioned in the ground. Preferably, the base has a hole positioned to be below ground level, when mounted, wherein the hole is arranged to allow one or several HV cables to enter the compartment of the base and connect to the HV switchgear via the opening in the floor. Further ground cables, e.g. 24 V DC and 230 V AC for supply for light etc. to the housing, may enter the base via dedicated holes below ground level.

To facilitate mounting of the enclosure onto the base, the base may comprise a plurality of upward facing pins arranged to fit matching holes of the enclosure, e.g. holes on an underside of the floor. This allow first mounting the base in the ground, and then mounting a complete pre-fabricated enclosure part onto the base in the correct position.

The top part is preferably removable, so as to allow the HV switchgear to enter the housing for installation from above, e.g. the top part can be mounted removable to a frame carrying wall parts by means of bolts. This helps to facilitate on-site mounting of the HV switchgear compared to a having an enclosure with a fixed top part, and further the requirement for size of a door opening can be limited.

The enclosure may be formed by a metal frame onto which the floor, a plurality of wall elements, and the top part are mounted.

In a preferred embodiment, the enclosure comprises a plurality of wall elements formed by corrugated metal plates, and the floor is formed by a concrete slab. Preferably, the roof and ceiling elements are formed by metal plates. Such structure can provide the necessary strength and endurance, and still have a light weight to allow road vehicle transportation of a completely assembled enclosure, e.g. with the base positioned inside the enclosure during transportation. The blowout opening to the environment may comprise an elongate downward facing opening formed between the roof element and the ceiling element. The housing may further enclose a HV step-up transformer inside the enclosed space, the HV step-up transformer being electrically connected to step-up a voltage to a higher voltage level, especially a voltage of 60-150 kV, e.g. 66 kV, required for connection to an electric grid. Preferably, the housing comprises a door allowing a person to enter the enclosed space, such as for service or inspection of the HV switchgear.

In a second aspect, the invention provides a wind turbine system arranged to generate electric power, the wind turbine system comprising

- a wind turbine comprising a rotor blade system, an electric generator connected to be driven by the rotor blade system, a tower with a nacelle for housing the electric generator, and a gas-isolated HV switchgear electrically connected between the electric generator and an electric grid output from the wind turbine, and

- a housing according to the first aspect for enclosing the HV switchgear, wherein the housing is positioned away from the tower.

In an embodiment, the system comprises a plurality of wind turbines with respective electric generators connected to respective gas-isolated HV switchgears arranged inside the enclosure of the housing. Thus, one single housing can be used to accommodate HV switchgear for e.g. 2-10 wind turbines. Further, even more equipment in common for the plurality of wind turbines can be placed inside the housing, e.g. a step-up transformator serving to step-up electric voltage to such as 60-150 kV, e.g. 66 kV, for grid connection.

In a third aspect, the invention provides a method for mounting a gas-isolated high voltage switchgear inside a housing, the method comprising

- providing a base forming a compartment with an upwards facing opening,

- mounting the base partly below ground level, - providing an enclosure forming an enclosed space, the enclosure comprising wall elements, a floor with an opening, a top part comprising a ceiling element and a roof element forming a compartment with a blowout opening to the environment, and a blowout channel,

- mounting the enclosure onto the base, so that the blowout channel connects the compartment of the base with the compartment of the top part, and

- mounting the HV switchgear on the floor inside the enclosed space, so as to cover the opening of the floor, and so that a HV switchgear blowout outlet is connected with the compartment of the base via the opening of the floor.

It is to be understood that the same advantages and preferred embodiments and features apply for the second and third apsects, as described for the first aspect, and the aspects may be mixed in any way. BRIEF DESCRIPTION OF THE FIGURES

The invention will now be described in more detail with regard to the

accompanying figures of which FIG. 1 illustrates a wind turbine system embodiment with a wind turbine and an external ground based housing enclosing a high voltage switchgear of the wind turbine,

FIG. 2 illustrates a housing base embodiment,

FIG. 3 illlustrates a side section view of a housing embodiment with blowout routes indicated,

FIG. 4 illustrates a top section view of a housing embodiment,

FIG. 5 illustrates illustrates a front view of a housing embodiment,

FIG. 6 illustrates illustrates, and

FIG. 7 illustrates steps of a method embodiment.

The figures illustrate specific ways of implementing the present invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set. DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a wind turbine system embodiment. The wind turbine has three rotor blades BL for driving an electric generator located inside the nacelle NC on top of a tower TW. Typically, a power converter system in a wind turbine can be placed up-tower or down tower. Wind turbines may generate an electric power of at least 1 MW, such as 2-10 MW, or more. The electric generator and power converter system generate High Voltage (HV) AC or DC RMS voltages in the 1-66 kV range. Thus, switchgear for switching on/off such voltages typically involves gas-isolated HV switchgear causing a safety risk, partly due to possible gas leakages, and partly due to the risk of a blowout or explosion in case of a fault. Thus, for safety reasons it is proposed to position HV switchgears outside the wind turbine tower. The invention provides a housing H with a base B to be placed in the ground and forming a base for an enclosure ENC with a floor, wall elements, and a top part serving to provide an enclosed space in which the HV switchgear HVS can be placed. The HV cable for connecting the wind turbine with the HV switchgear HVS is indicated with dashed line, and as seen the HV cable enters the housing H from the ground via the base B. The housing provides a blowout route involving a compartment in the base B as well as a compartment in the top part of the enclosure to relieve the high pressure in case of a blowout.

FIG. 2 shows an example of a base B for the housing H of FIG. 1. The base B in the pictured embodiment is formed by a concrete element being generally rectangular in shape and with a flat bottom part and with walls perpenduclar to the bottom part. The walls and bottom form a compartment, and the upper part of the walls form a plane face, thus providing an opening to the compartment of the base B.

Four guiding pins P1-P4 serve to facilitate mounting of the enclosure ENC onto the base by guiding the enclosure ENC into place to fit respective holes in the bottom part of the floor F.

The skilled person will be able to devise bases with shapes different to the embodiment shown and able to fulfil the same purpose. FIG. 3 illustrates a preferred housing H embodiment. The housing has a base B arranged for mounting at least partly below ground level, the base B forming a compartment Cl with an upwards facing opening. An enclosure ENC is mounted on the base B. The enclosure ENC forms an enclosed space E_SP between vertical wall elements W, a plane horizontal floor F with an opening F_0 serving to connect to the compartment Cl of the base B via the upwards facing opening of the base B. The high voltage switchgear HVS is arranged to be mounted on the floor F so as to cover the opening F_0 of the floor F. The high voltage switchgear HVS has a blowout outlet at its bottom, which connects to the compartment Cl of the base B via the opening F_0 of the floor F. A top part TP of the enclosure ENC comprises a ceiling element CL and a roof element R forming together a

compartment C2 with a blowout opening BL_0 to the environment. A blowout channel BLC is here shown as a plane plate forming a channel together with a wall element W. The blowout channel BLC connects the compartment Cl at the base B at one end, and the compartment C2 of the top part TP at its opposite end.

The black arrows show the blowout route BLR from the bottom of the HV switchgear HVS, via the base compartment Cl, via a separate hole in the floor F, through the blowout channel BLC, and to the compartment C2 at the top part TP, where a downward facing blowout opening BL_0 is formed on both sides of the top part, namely elongate openings BL_0 formed by the roof element R and the ceiling element CL. Thus, two compartments Cl, C2 serve to absorp the high pressure wave from the HV switchgear in case of a blowout, therefore providing only a limited pressure outlet at the blowout openings BL_0.

Preferably, the housing H is dimensioned, so that the blowout openings BL_0 is positiond at a height of such as 1.8-2.5 m above ground level, to avoid immediate danger for a person on the ground near the housing H.

A HV cable (not shown) for connection to the HV switchgear HVS via the opening F_0 in the floor F can enter the base B through an opening C_0 below ground level.

Preferably, the total height of the enclosure ENC itself is 2.4-2.6 m, so as to allow the enclosure to be manufactured as one unit and transported on a road vehicle. Preferably, the base is positioned inside the enclosure ENC during transporting, thus lowering the total height of the housing H, when transported. The top part is preferably removable, to provide an upward facing opening to the enclosed space E_CP for mouting the switchgear in the enclosure ENC from above.

Preferred materials are:

- Floor F and base B: concrete.

- Wall elements W: corrugated metal plate.

- Blowout channel BLC: metal plate, a separate channel or integrated with a wall element W.

- Ceiling element CL and roof element R: metal plate.

The enclosure ENC may be formed by a metal frame fixed to the concrete floor F slab, and with wall elements W and top part TP fixed to the frame.

The enclosure can be manufactured in modules, e.g. each module being formed by a frame and floor F of fixed dimensions, and where two or more modules can be combined to form a larger housing H, if required. E.g. this may be useful for reducing costs, e.g. to provide housings H for wind turbine plants, where HV switchgear for several wind turbines can be enclosed in one single housing H, e.g formed by a plurality of combined enclosure modules sharing one or more base(s).

FIG. 4 illustrates a top section view of an embodiment showing the rectangular floor F and the rectangular floor opening F_0 , as well as the blowout channel BLC, here shown as a separate channel BLC arranged separate from the nearest wall W element. The blowout channel BLC connects to the base B via a hole in the floor F being separate from the floor opening F_0 which is arranged to be covered by the HV switchgear HVS, when mounted.

FIG. 5 illustrates af frontal view of the embodiment of FIG. 1, where one side of the enclosure ENC is in the form of a door D allowing a person to enter the enclosed space E_SP. E.g. the door D has a lock to prevent unauthorized personnel to enter the enclosure ENC. The base B is shown in section view, and the HV cable opening C_0 to the compartment Cl is seen along with two horizontal beems BM1, BM2 fixed in the walls of the base. The beams BM1, BM2 serve to fix the HV cable (not shown) in order to bend from a horizontal position in the ground to a vertical position in order to connect to the HV switchgear HVS inside the enclosure ENC.

FIG. 6 illustrates an example of a wind turbine system embodiment with a plurality of wind turbines WT1-WT6 all connected via HV cables to one common housing H which provides an enclosure for respective gas-isolated HV switchgears HVS1_6 for the wind turbines WT1-WT6. One electric output cable from the housing H serves to connect all wind turbines WT1-WT6 to an electric grid E_G.

FIG. 7 illustrates steps of an embodiment for a method for mounting a gas- isolated HV switchgear inside a housing. The method comprising providing P_B a base forming a compartment with an upwards facing opening, mounting M_B the base partly below ground level preferably with the upward facing opening flush with ground level. Next, providing P_ENC an enclosure forming an enclosed space, the enclosure comprising wall elements, a floor with an opening, a top part comprising a ceiling element and a roof element forming a compartment with a blowout opening to the environment, and a blowout channel. Next, mounting M_ENC the enclosure onto the base, so that the blowout channel connects the compartment of the base with the compartment of the top part, and mounting M_HVS the HV switchgear on the floor inside the enclosed space, so as to cover the opening of the floor, and so that a HV switchgear blowout outlet is connected with the compartment of the base via the opening of the floor.

Preferably, the method comprises pre-fabricating the enclosure and base, and transporting the housing with the base positioned inside the enclosure, e.g. on a road vehicle. Preferably, the base is mounted M_B in the ground, e.g. on a sand foundation, and the HV cable is entered into the base. Next, the enclosure is fixed onto the base. These steps can be performed before the HV switchgear arrives on- site. When the HV switchgear is ready to be installed, the top part of the enclosure can preferably be removed, so as to allow the HV switchgear to enter the enclosure from above, and subsequently, the top part can then be re- installed, and the enclosed HV switchgear is then ready for operation. Alternatively, the door of the enclosure is dimensioned, so that the HV switchgear can be enter the enclosed space of the enclosure via the door opening.

To sum up: the invention provides a wind turbine system with a wind turbine having a HV switchgear positioned inside a housing positioned on the ground, external to the wind turbine tower to provide increased safety inside the tower. The housing has a concrete baseframe forming a compartment, and an enclosure part mounted on the baseframe. The blowout of the HV switchgear is connected to the baseframe compartment via an opening in the floor of the enclosure part, and a blowout channel connects the baseframe compartment to a compartment formed between a ceiling and a roof of the enclosure part, and this upper compartment has a blowout opening to the environments, preferably posisioned at least 2 m above ground level. The enclosure part has a door to allow a person to enter the housing, and wall elements of the enclosure part are preferably formed by metal plates. The blowout compartments of the baseframe and upper compartment serve to lower pressure of a blowout, and thus helps to provide a safe blowout output to the environment.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is to be interpreted in the light of the accompanying claim set. In the context of the claims, the terms "including" or "includes" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.