Patent Description:
A power transformer is equipment used in an electric grid of a power system. Power transformers transform voltage and current in order to transport and distribute electric energy.

A tap-changer is used to change the turn ratio between windings in a transformer. This ratio determines the voltage ratio between the windings and is essential for the stabilization of network voltage under variable load conditions. Tap changers usually exist in two primary types, no-load tap changers (NLTC) and on-load tap changers (OLTC). A NLTC, also known as off-circuit tap changer (OCTC) or de-energized tap changer (DETC), is a tap changer utilized in situations in which a transformer's turn ratio does not require frequent changing and it is permissible to de-energize the transformer system. This type of transformer is frequently employed in low power, low voltage transformers in which the tap point often may take the form of a transformer connection terminal, requiring the input line to be disconnected by hand and connected to the new terminal. An OLTC, also known as on-circuit tap changer (OCTC), is a tap changer in applications where a supply interruption during a tap change is unacceptable, the transformer is often fitted with a more expensive and complex on load tap changing mechanism. OLTCs may be generally classified as either mechanical, electronically assisted, or fully electronic.

When transformers are introduced on floating platforms out in the sea, new types of mechanical load conditions will be present. Such conditions are alternating accelerations in different directions due to waves in the sea.

An in-tank tap changer is a tap changer that is located inside a transformer tank. In-tank tap changers are normally only fixated towards a transformer tank cover, which is satisfying if there are not any repetitive alternating accelerations present. However, continuous alternating accelerations, especially in the horizontal plane, could cause fatigue in different parts of this fixation towards the transformer tank cover. There is need for a solution that will help the tap changer sustain repetitive changes in horizontal acceleration both regarding high magnitude and number. <CIT> shows a tap changer that is supported by the transformer against the tank wall.

The present disclosure presents an improved viable solution of a transformer arrangement that handles the issues described above.

It is an object of embodiments herein to handle movement of a tap changer in a transformer, or at least to achieve an alternative to known solutions within the technical field.

According to an aspect the object is achieved by providing a transformer arrangement. The transformer arrangement comprises a transformer, a transformer tank and at least one tap changer. The tap changer is arranged to be connected to said transformer. The transformer arrangement further comprises at least one support structure. The support structure is arranged to be connected to the tap changer and to extend between the tap changer and at least two support members. The at least two support members are located between the tap changer and at least two points on an inner surface of the transformer tank. The at least one support structure is arranged to reduce pendular movement of the tap changer.

According to another aspect the above-mentioned object is also achieved by providing a method for assembling a transformer arrangement. The transformer arrangement comprises a transformer, a transformer tank and at least one tap changer. The transformer arrangement further fixates a support structure to the tap changer and at least two support members located between the tap changer and at least two points on an inner surface of the transformer tank. The support structure is arranged to reduce pendular movement of the tap changer.

It is furthermore provided herein use of a transformer arrangement wherein the transformer arrangement is located on a floating platform.

Embodiments herein are based on the realisation that by providing a transformer arrangement comprising at least one support structure arranged between a tap changer and at least one support member, wherein the at least one support member is connected to an inner surface of a transformer tank, the tap changer is supported by an additional support towards the transformer tank. Thereby pendular movement of the tap changer can be reduced and thus the movement of the tap changer is handled in an efficient manner. Even though some embodiments have been summarized above, the claimed subject matter is defined in the attached claims.

Further technical features of the invention will become apparent through the following description of one or several exemplary embodiments given with reference to the appended figures, where:.

It should be noted that the drawings have not necessarily been drawn to scale and that the dimensions of certain elements may have been exaggerated for the sake of clarity.

A transformer arrangement <NUM> according to embodiments herein is illustrated in <FIG>. The transformer arrangement <NUM> comprises a transformer, a transformer tank <NUM> and at least one tap changer <NUM>. The tap changer <NUM>, which may be an OLTC, is arranged to be connected, e.g. fixated, to the transformer. The tap changer <NUM> may comprise at least one tap selector <NUM> that extends in a longitudinal direction of the transformer. The transformer arrangement <NUM> further comprises at least one support structure <NUM> which is arranged to be connected to the tap changer <NUM> and to extend between the tap changer <NUM> and at least one support member <NUM> located between the tap changer <NUM> and at least one point on an inner surface of the transformer tank <NUM>. According to some embodiments the support structure <NUM> may be connected to the tap changer <NUM> at a height that is within <NUM>% of the height of a centre of gravity of said tap changer <NUM>. the support structure <NUM> may be connected close to the tap changer <NUM> centre of gravity. According to some embodiments the transformer tank <NUM> comprises at least one corner and the support structure <NUM> may be arranged to be connected to the tap changer <NUM> and to extend between the tap changer <NUM> and the at least one corner of the transformer tank <NUM>. According to some embodiments the transformer tank <NUM> comprises at least one beam structure and the support structure <NUM> may be arranged to be connected to the tap changer <NUM> and to extend between the tap changer <NUM> and the at least one beam structure of the transformer tank <NUM>. According to some embodiments the transformer arrangement <NUM> comprises at least one adjusting means <NUM>, located between the at least one support member <NUM> and the at least one point on the inner surface of the transformer tank <NUM>. The support structure <NUM> may further comprise at least one sensor and/or at least one accelerometer (not shown) for monitoring the transformer arrangement <NUM>.

According to some embodiments the tap changer <NUM> of the transformer arrangement <NUM> comprises a cover flange <NUM>, e.g. a tap changer top flange, and the tap changer <NUM> is arranged to be fixated to a transformer cover <NUM> via the cover flange <NUM>. This is illustrated in <FIG>.

The transformer arrangement <NUM> may also comprise means such as a manhole and/or a handhole <NUM>. The manhole and/or the handhole <NUM> may be located on the transformer tank <NUM>. The manhole and/or the handhole <NUM> may be used to enable access for connecting the at least one support member <NUM> with the transformer tank <NUM>. The connection of the at least one support member <NUM> with the transformer tank <NUM> may then be adjusted by using the adjusting means <NUM>. <FIG> illustrates the transformer arrangement <NUM> comprising the handhole <NUM>.

The at least one support structure <NUM> is arranged to reduce pendular movement of the tap changer <NUM>. The transformer arrangement <NUM> thus hinders the pendulum movement, e.g. motion, of the tap changer <NUM> by adding the at least one support structure <NUM>. The pendulum movement of the tap changer <NUM> may be reduced around the top fixation, e.g. around the cover flange <NUM>, by reducing movement in the horizontal plane of lower parts of the tap changer <NUM>. Thereby the tap changer <NUM> is not only fixated to the transformer, e.g. to the transformer cover <NUM> via the cover flange <NUM>, as the support structure <NUM> is an additional support towards the transformer tank <NUM>, and/or towards a point related to the tank wall, for avoiding pendular motion of the tap changer <NUM>.

<FIG> illustrates a schematic overview of the transformer arrangement <NUM> according to embodiments herein. As mentioned above, the transformer arrangement <NUM> comprises a support structure <NUM> arranged to be connected to the tap changer <NUM> and to extend between the tap changer <NUM> and at least one support member <NUM> located between the tap changer <NUM> and at least one point on an inner surface of the transformer tank <NUM>. The tap changer <NUM> may be an in-tank tap changer. According to some embodiments the support structure comprises at least two support members <NUM> located between the tap changer <NUM> and at least two points on an inner surface of the transformer tank <NUM>. According to some embodiments the at least one support member <NUM> may comprise an electrical insulated material. Examples of electrical insulating materials that the support member may comprise is fiberglass reinforced polyester. The at least one support structure <NUM> may be fixated closely to the tap changer <NUM> centre of gravity and extend towards at least one point on an inner surface of the transformer tank <NUM>. The at least one point on the inner part of the transformer tank <NUM> may be a part not being influenced by pressure change, i.e. does not move, during vacuum filling, oil filling or lifting of the transformer. Such part of the transformer tank <NUM> may be the corner, an additional beam structure or a stiff part of the transformer tank <NUM>. According to some embodiments the transformer arrangement <NUM> comprises at least one adjusting means <NUM>, located between the at least one support member <NUM> and the at least one point on the inner surface of the transformer tank <NUM>. The at least one adjusting means <NUM> may make the at least one support member <NUM> adjustable between the transformer tank <NUM> and the tap changer <NUM>. <FIG> also shows a tap selector <NUM>, and the tap changer <NUM> may comprise at least one tap selector <NUM> that extends in a longitudinal direction of the transformer. The tap selector <NUM> may comprise a fine tap selector and/or a change-over selector.

The method actions for assembling a transformer arrangement <NUM>, according to embodiments herein, will now be described with reference to a flowchart depicted in <FIG>. The actions do not have to be taken in the order stated below but may be taken in any suitable order. Actions performed in some embodiments are marked with dashed boxes. The transformer arrangement <NUM> comprises transformer, a transformer tank <NUM> and at least one tap changer <NUM>.

The transformer arrangement <NUM> may fixate the tap changer <NUM> to the transformer cover <NUM>. The tap changer may be an OLTC. According to some embodiments the transformer comprises a cover flange <NUM> and fixating the tap changer <NUM> to the transformer cover <NUM> may comprise fixating the tap changer <NUM> to the transformer cover <NUM> via the cover flange <NUM>. Furthermore, fixation in horizontal direction after tanking of the transformer and after fixation of the tap changer <NUM> to the transformer cover <NUM>, e.g. top cover, may also support all today used assembly methods such as cover mounted or fork mounted tap changers.

The transformer arrangement <NUM> then fixates the support structure <NUM> to the tap changer <NUM> and at least one support member <NUM> located between the tap changer <NUM> and at least one point on an inner surface of the transformer tank <NUM>. The at least one support member <NUM> may comprise an electrically insulating material. According to some embodiments the support structure <NUM> comprises the at least two support members <NUM> located between the tap changer <NUM> and at least two points on an inner surface of the transformer tank <NUM>. The support structure <NUM> may be connected, e.g. fixated, to the tap changer <NUM> at a height that is within <NUM>% of the height of a centre of gravity of said tap changer <NUM>. The transformer tank <NUM> may comprise at least one corner and the support structure <NUM> may be arranged to be connected to the tap changer <NUM> and to extend between the tap changer <NUM> and the at least one corner of the transformer tank <NUM>. The transformer tank <NUM> may comprise at least one beam structure and the support structure <NUM> may be arranged to be connected to the tap changer <NUM> and to extend between the tap changer <NUM> and the at least one beam structure of the transformer tank <NUM>.

The support structure <NUM> is thus arranged to reduce pendular movement of the tap changer <NUM>.

The transformer arrangement <NUM> may fixate the at least one adjusting means <NUM> to the at least one support member <NUM> and the at least one point on the inner surface of the transformer tank <NUM>.

The transformer arrangement <NUM> may add adjusting means <NUM> in the transformer tank <NUM> to make the at least one support member adjustable between the transformer tank <NUM> and the tap changer <NUM> to provide stress released fixation.

An advantage with embodiments herein is that the tap changer can withstand repetitive changes in horizontal acceleration both regarding high magnitude and number.

Another advantage of embodiments herein is that the risk of oil leakage between the transformer and the tap changer <NUM> will be reduce by hindering the pendulum motion that could start wearing the sealing system.

Another advantage of embodiments herein is also improvement of earthquake performance.

According to embodiments herein the transformer arrangement <NUM> is located on a floating platform. The transformer arrangement <NUM> may come to its best use for floating applications as waves will add inclinations and alternating accelerations in all directions. In such floating applications the tap changer <NUM>, e.g. in-tank tap changer, needs to improve performance in the horizontal plane direction. The vertical direction is normally already strong enough due to existing gravity and internal pressure withstand of the tap changer <NUM> acting in the same direction and thereby already considered.

It is to be noted that any feature of any of the aspects may be applied to any other aspect, wherever appropriate. Likewise, any advantage of any of the aspects may apply to any of the other aspects.

Claim 1:
A transformer arrangement (<NUM>) comprising a transformer, a transformer tank (<NUM>) and at least one tap changer (<NUM>) that is arranged to be connected to said transformer, wherein the transformer arrangement (<NUM>) further comprises at least one support structure (<NUM>) which is arranged to be connected to the tap changer (<NUM>) and to extend between the tap changer (<NUM>) and at least two support members (<NUM>) located between the tap changer (<NUM>) and at least two points on an inner surface of the transformer tank (<NUM>), wherein the at least one support structure (<NUM>) is arranged to reduce pendular movement of the tap changer (<NUM>).