Electrical device with dual voltage regulation for power grid

Abstract

An electrical device (3) for power grids, comprising a transformer (6) housed in a tank (1) and having a dual voltage regulation system. The device comprises a first no-load tap changer (DETC) (11) and a second on-load tap changer (OLTC) (12). Both tap changers are associated with a primary winding (7) of the transformer. The DETC (11) performs a first voltage regulation by establishing an operating range, while the OLTC (12) performs a fine and automatic second regulation within the range set by the DETC (11). The combination of the two tap changers (11, 12) with the electrical taps (13-20) of the primary winding (7) allows to change the number of turns to regulate the voltage in the secondary winding (8), thus increasing the ability of the device to adapt to power grid fluctuations.

Description

Technical Field

[0001] This invention relates to electrical infrastructure, such as power distribution networks, and specifically to an electrical device, such as a transformer, characterized in that it includes multiple tap changers, such as on-load tap changers and off-load tap changers. Combining these two types of tap changers in the same electrical device optimizes voltage regulation and improves operating efficiency, thereby adapting in real time to changes in load or power generation (e.g., distributed generation) and performing periodic adjustments during maintenance.

[0002] This combination allows for an expansion of the output voltage range in the secondary windings of electrical equipment and is particularly suitable for applications requiring precise voltage regulation under varying load conditions, in order to adapt to new voltage regulation needs arising from changes in the power grid. Background Technology

[0003] Maintaining the output voltage of high-voltage electrical equipment (such as transformers) within the permissible or desired range, depending on the load or power generation conditions, is traditionally achieved by changing the turns ratio of the equipment, thereby correspondingly altering the voltage ratio between the primary and secondary windings. For this purpose, high-voltage electrical equipment is equipped with a device called a tap changer, which can be an off-load tap changer or an on-load tap changer, meaning that tap switching can be performed whether the equipment is de-energized or energized. The tap changer increases or decreases the number of turns in the primary winding, thereby changing the turns ratio, in other words, changing the voltage in the secondary winding.

[0004] A de-energized load tap changer (DETC) requires the transformer to be de-energized to change the electrical tap position. While DETCs do not offer the same flexibility as on-load tap changers (OLTCs), they are useful for adjustments that do not require frequent execution. Therefore, DETCs are used to adjust the turns ratio during planned maintenance. In its applications, DETCs are particularly suitable for periodic and infrequent adjustments, such as adapting the transformer to grid conditions.

[0005] On the other hand, on-load tap changers (OLTCs) allow the transformer taps to be changed during transformer operation without interrupting power supply. This is crucial for maintaining grid stability during load or generation fluctuations. There are two main types of OLTCs: one uses resistors to limit current during tap switching, and the other uses reactors to achieve the same purpose.

[0006] Smart transformers (also known as "Smart Transformers" or VRDTs, or Voltage Regulating Distribution Transformers) used in power grids (such as low-voltage distribution networks) allow for automatic regulation of the output voltage in the secondary windings during operation, thereby improving the stability and quality of power supply.

[0007] However, these smart transformers currently rely entirely on on-load tap changers (OLTCs), meaning their configurations cannot be modified once manufactured. This limits their flexibility and adaptability to different locations and evolving distribution networks, such as due to the integration of distributed generation or the increasing demand for electric vehicle charging, both now and in the short to medium term. This is problematic because smart transformers are typically installed without considering the characteristics of the low-voltage grid or its ability to change over time.

[0008] As mentioned earlier, with the increasing integration of distributed generation, electric vehicles, heat pumps, and other technologies into the grid, these grid changes are becoming more frequent. These factors can cause voltage fluctuations in the low-voltage grid, thus limiting the integration of these new technologies. The volatility of renewable energy sources, such as solar and wind power, can cause grid fluctuations, affecting power supply stability. Similarly, distributed generation can introduce power quality problems, such as voltage fluctuations and harmonics; adapting existing infrastructure to accommodate distributed generation may also require significant investment. On the other hand, the additional electricity demand for electric vehicle charging can overload existing infrastructure, especially during unmanageable peak hours, leading to voltage congestion in the low-voltage distribution network.

[0009] The aforementioned problems, such as low-voltage distribution network congestion due to high electricity demand during peak hours, arise because smart transformers equipped only with OLTCs cannot extend their voltage range further to meet the electricity demand once a certain limit is reached. While OLTCs can automatically maintain grid stability during load fluctuations, these fluctuations may be so large during peak demand periods that the OLTC cannot perform further tap changes. In other words, it cannot further increase the turns ratio of electrical equipment or transformers, and therefore cannot provide the required output voltage in the secondary windings of the electrical equipment to meet the electricity demand.

[0010] Therefore, it is obvious that it is necessary to obtain as many turns ratios as possible without changing the transformer's structural layout. Summary of the Invention

[0011] The present invention is applied to electrical facilities, such as power distribution networks, and relates to an electrical device, such as a transformer, designed to solve each of the above problems.

[0012] The electrical device of the present invention relates to a device with dual voltage regulation, that is, the electrical device allows for a first regulation, in which a voltage range is established, and then allows for a second voltage regulation within the voltage range established by the first regulation. For this purpose, the electrical device includes one or more tap switches, such as a first tap switch and a second tap switch, wherein the first tap switch performs the first voltage regulation by establishing a voltage range, and the second tap switch performs the second voltage regulation within the voltage range established by the performed first regulation.

[0013] The electrical equipment for the power grid is housed in a enclosure and insulated by an insulating medium, such as a dielectric liquid, which at least partially fills the enclosure.

[0014] The electrical equipment also includes at least one inlet in the enclosure, the at least one inlet corresponding to at least one phase of a high-voltage power grid. The electrical equipment may be a transformer and includes at least one primary winding and at least one secondary winding, the at least one primary winding being connected to at least one phase of the high-voltage power grid, and the at least one secondary winding being connected, for example, to at least one phase and a neutral phase of a low-voltage power grid, or, for example, to at least one phase of another high-voltage power grid.

[0015] The at least one tap changer of the electrical equipment is provided with at least one electrical tap per phase, and the electrical tap is associated with at least one connection point of the primary winding, the number of turns in the primary winding being variable, thereby allowing adjustment of the voltage in the secondary winding of the electrical equipment.

[0016] The electrical equipment of the present invention may include two tap switches, namely a first tap switch and a second tap switch, wherein each tap switch is connected to its corresponding electrical tap.

[0017] In this sense, it has been considered that the first tap changer can be a de-energized tap changer (DETC), and the second tap changer can be an on-load tap changer (OLTC). Combining the DETC with the OLTC allows the distribution system operator (DSO) to modify the operating range of the OLTC as needed, thereby maximizing the efficiency of electrical equipment, reducing voltage congestion, and increasing acceptance capacity without altering the structural layout of the electrical equipment or transformers. That is, the first tap changer (DETC) performs a first voltage regulation by establishing a voltage range, while the second tap changer (OLTC) performs a second voltage regulation within the voltage range established by the first voltage regulation. Thus, depending on the location or electrical tap of the first tap changer (DETC), the voltage range can be extended or widened to higher or lower voltage values.

[0018] Combining a de-energized tap changer (DETC) and an on-load tap changer (OLTC) in the same electrical device makes smart transformers more flexible and capable of managing voltage congestion in the power grid, such as in low-voltage grids, because the combination widens the voltage range in the secondary winding of the electrical device.

[0019] The first de-energized tap changer (DETC) and the second on-load tap changer (OLTC) are mounted under the cover of the electrical equipment and are at least partially immersed in the insulating medium contained in the electrical equipment.

[0020] The first tap changer may include an operating part located on the cover of the electrical equipment. When the first tap changer is a de-energized type (DETC), the operating part allows manual operation of the first tap changer from outside the electrical equipment enclosure when the electrical equipment is de-energized. However, it has also been considered that the first tap changer may also be operated automatically.

[0021] The second on-load tap changer (OLTC) includes a motor powered by any low-voltage power source, which allows the second on-load tap changer (OLTC) to be automatically operated so that the second on-load tap changer can be electrically connected to its respective electrical tap.

[0022] Each tap changer, namely the first tap changer and the second tap changer, can be connected to one of its corresponding electrical taps, and the number of turns in the primary winding of the electrical equipment varies based on the combined connection of the electrical taps of the first tap changer and the second tap changer.

[0023] Therefore, the first tap changer can be operated when necessary to establish a new voltage range or adjust the automatic operation of the second tap changer. For example, the first tap changer can be of the de-energized type (DETC) and the second tap changer can be of the on-load type (OLTC).

[0024] The combination of a de-energized tap changer (DETC) and an on-load tap changer (OLTC) allows smart transformers to adapt to the specific current and future needs of each installation scenario by operating the DETC, even if initial conditions evolve and the initial DETC placement is no longer optimal. In short, this combination allows a wide range of applications to be covered with a single electrical device design, as each distribution transformer station with this device may have different voltage regulation requirements. Attached Figure Description

[0025] Figure 1A schematic single-line diagram of a combination of a first tap switch and a second tap switch included in the electrical device with dual voltage regulation of the present invention is shown.

[0026] Figure 2 A front view of the electrical device of the present invention is shown, in which the positions of the first tap switch and the second tap switch are shown inside the same electrical device. Detailed Implementation

[0027] A preferred embodiment is described below with reference to the accompanying drawings, but this does not limit or narrow the scope of protection of the present invention.

[0028] like Figure 2 As shown, the electrical device (3) for the power grid of the present invention can be, for example, a transformer, which includes multiple tap switches (11, 12), such as a first off-load tap switch (11) and a second on-load tap switch (12). Thus, the electrical device (3) includes dual voltage regulation, that is, the first tap switch (11) performs a first voltage regulation by establishing a voltage range, while the second tap switch (12) performs a second voltage regulation within the voltage range established by the first regulation performed by the first tap switch (11).

[0029] like Figure 2 As shown, the electrical equipment (3) is housed in a enclosure (1) and insulated by an insulating medium (2), such as a dielectric liquid, which at least partially fills the enclosure (1). The electrical equipment (3) also includes at least one inlet (4) in the enclosure (1), the at least one inlet corresponding to at least one phase (5) of a high-voltage power grid; and a converter (6) having at least one primary winding (7) and at least one secondary winding (8), the at least one primary winding being connected to at least one phase (5) of the high-voltage power grid, and the at least one secondary winding being connected to at least one electrical phase (9) and a neutral phase (10) of a low-voltage power grid.

[0030] Similarly, each phase of the tap changer (11, 12) is provided with at least one electrical tap (13, 14, 15, 16, 17, 18, 19, 20), such as Figure 1 As shown, the electrical device (3) includes at least one connection point (21, 22, 23, 24, 25, 26, 27, 28) on the primary winding (7), the at least one connection point being associated with at least one electrical tap (13, 14, 15, 16, 17, 18, 19, 20), the number of turns in the primary winding (7) being variable, thereby enabling adjustment of the voltage in the secondary winding (8) of the electrical device (3).

[0031] The first off-load tap changer (11) and the second on-load tap changer (12) are mounted below the cover (29) of the electrical equipment (3) and are at least partially immersed in the insulating medium (2) of the electrical equipment (3) itself. The arrangement of the first tap changer (11) and the second tap changer (12) below the cover (29) can be horizontal, such as... Figure 2 As shown, it can also be vertical (this arrangement is not shown in the attached figure).

[0032] As an example embodiment shown in the accompanying drawings, the first off-load tap changer (11) includes an operating part (30) located on the cover (29) of the electrical equipment (3), which allows the first tap changer (11) to be manually operated from outside the housing (1) of the electrical equipment (3) when the electrical equipment (3) is de-energized. The first off-load tap changer (11) can be connected to electrical taps (13), (14), or (15). On the other hand, the second on-load tap changer (12) includes a motor (31) powered by any low-voltage power supply, which allows the second tap changer (12) to be automatically operated, such that the second tap changer can be electrically connected to electrical taps (16), (17), (18), (19), or (20).

[0033] Therefore, especially as Figure 1 As shown, the first off-load tap changer (11) and the second on-load tap changer (12) can be connected to one of their respective electrical taps (13, 14, 15, 16, 17, 18, 19, 20), and the number of turns in the primary winding (7) varies based on the combined connection of the electrical taps (13, 14, 15) of the first tap changer (11) and the electrical taps (16, 17, 18, 19, 20) of the second tap changer (12).

Claims

1. An electrical device for a power grid, the electrical device being housed in a enclosure (1) and insulated by an insulating medium (2) that at least partially fills the enclosure (1), the electrical device (3) comprising: - At least one inlet (4) in the enclosure (1), the at least one inlet (4) corresponding to at least one phase (5) of the high-voltage grid; - Converter (6), the converter comprising: - At least one primary winding (7), said at least one primary winding (7) being connected to said at least one phase (5) of the high-voltage power grid; and - At least one secondary winding (8), said at least one secondary winding (8) is connected to at least one phase (9, 10) of another high-voltage grid or low-voltage grid. - At least one tap changer (11, 12), wherein each phase of the at least one tap changer (11, 12) is provided with at least one electrical tap (13, 14, 15, 16, 17, 18, 19, 20); and - At least one connection point (21, 22, 23, 24, 25, 26, 27, 28) on the primary winding (7), said at least one connection point being associated with said at least one electrical tap (13, 14, 15, 16, 17, 18, 19, 20), the number of turns in said primary winding (7) is variable, thereby allowing regulation of the voltage in said secondary winding (8) of said electrical device (3), The electrical equipment (3) is characterized in that it further includes a second tap switch (11, 12), wherein the first tap switch (11) is connected to at least one electrical tap (13, 14, 15), and the second tap switch (12) is connected to at least one electrical tap (16, 17, 18, 19, 20).

2. The electrical equipment according to claim 1, characterized in that, The first tap changer (11) is an off-load tap changer, and the second tap changer (12) is an on-load tap changer.

3. The electrical equipment according to claim 2, characterized in that, The first off-load tap changer (11) and the second on-load tap changer (12) are installed under the cover (29) of the electrical equipment (3) and are at least partially immersed in the insulating medium (2).

4. The electrical equipment according to claim 3, characterized in that, The first de-energized tap changer (11) includes an operating part (30) located on the cover (29) of the electrical equipment (3), the operating part allowing the first tap changer (11) to be manually operated from outside the housing (1) of the electrical equipment (3) when the electrical equipment (3) is de-energized, the first de-energized tap changer (11) being connectable to the electrical tap (13), the electrical tap (14) or the electrical tap (15).

5. The electrical equipment according to claim 3, characterized in that, The second on-load tap changer (12) includes a motor (31) powered by any low-voltage power source, the motor allowing automatic operation of the second tap changer (12) such that the second tap changer can be electrically connected to the electrical tap (16), the electrical tap (17), the electrical tap (18), the electrical tap (19), or the electrical tap (20).

6. The electrical equipment according to any one of claims 2 to 5, characterized in that, The first off-load tap changer (11) and the second on-load tap changer (12) are connected to one of their respective electrical taps (13, 14, 15, 16, 17, 18, 19, 20), and the number of turns in the primary winding (7) varies based on the combined connection of the electrical taps (13, 14, 15) of the first tap changer (11) and the electrical taps (16, 17, 18, 19, 20) of the second tap changer (12).

7. The electrical equipment according to any one of the preceding claims, characterized in that, The insulating medium (2) is a dielectric liquid.

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