EP3494584B1 - Electrical device having a plurality of cooling units - Google Patents

Description

The invention relates to an electrical device for connection to a high-voltage network with a vessel which is filled with an insulating fluid, an active part arranged in the vessel which has a magnetizable core and partial windings for generating a magnetic field in the core, and a cooling device for cooling the Isolating fluids, wherein at least one thermal barrier delimits the cooling spaces, in each of which at least one partial winding is arranged.

Such an electrical device is from the EP 2 833 378 A1 already known. A medium-frequency transformer is shown there, which has a housing filled with insulating fluid, in which an active part is arranged. The active part has a core which forms a closed magnetic circuit, a section of the core being enclosed by a secondary and a primary winding which are arranged concentrically to one another. In order to be able to increase the frequency of the medium-frequency transformer without an additional temperature increase, an insulating element is arranged between the primary and secondary windings, which is equipped with a conductive shield on both sides. The conductive shields on both sides of the insulating element are electrically connected on the one hand to the primary winding and on the other to the secondary winding, so that the formation of high electrical field strengths is avoided. Due to the thermal insulation, cooling tubes, which are connected to a cooling unit, extend on both sides of the thermal element.

The US 2013/0307654 A1 discloses a transformer having a tank and an active part arranged in the tank. The tank or boiler is filled with an insulating fluid. A cooling unit, which is connected to the interior of the boiler, is provided for cooling the insulating fluid. The The cooling unit has a pump for circulating the insulating fluid and a heat exchanger which is arranged in the air flow of a fan of the cooling unit. To improve the cooling performance, a so-called emergency cooling unit is provided, which has a pipeline system that extends through the interior of the windings.

From the EP 0 616 341 A1 a transformer with tank and active part is known, the active part again consisting of a core with low and high voltage winding. The boiler or tank is filled with an insulating fluid that is circulated through a cooling unit. Guide tubes or channels are also formed in the interior of the tank in order to guide the insulating fluid specifically over the windings and through the core.

Transformers or chokes, which are connected to a high-voltage network, each have a vessel that is usually filled with a mineral insulating oil as the insulating fluid. In the case of a transformer, a low-voltage and a high-voltage winding, which are inductively coupled to one another via a magnetizable core, are arranged in the vessel. In addition to insulating the windings, the insulating fluid also serves to cool the transformer. For this purpose, the insulating oil, which is heated during operation, is conducted to dissipate the heat via a cooling device attached to the outside of the vessel. The cooling is set so that a maximum temperature of the insulating fluid is not exceeded, since otherwise the solid insulation of the transformer could be damaged.

Alternative insulating fluids, such as ester or silicone oils, are increasingly being used in transformers, which have a higher temperature resistance. These alternative insulating fluids ensure a higher level of fire safety and are also biodegradable. Improved environmental compatibility of insulating fluids is particularly necessary for off-shore applications. Due to the improved thermal resistance of these alternative insulating fluids, the transformer can be operated at higher temperatures. In this context, reference is made to the IEEE 1276 (1997) standard.

In addition to the conventional, ie currently predominantly used, insulation systems and materials, so-called high-temperature insulation for electrical devices is known. However, these are costly. For this reason, so-called hybrid solutions have been proposed, in which both high-temperature materials and conventional materials were used as insulation. For example, the barrier system of the insulation has conventional insulation materials, while the conductor winding insulation is carried out using high-temperature materials. However, the hybrid solutions have the disadvantage that, despite the use of expensive high-temperature insulating materials, the operating temperature of the insulating fluid is significantly below the temperature that would be possible if high-temperature insulating materials were used exclusively due to the conventional insulating materials still being used.

The object of the invention is therefore to provide an electrical device of the type mentioned at the beginning which is inexpensive and at the same time can be operated at higher temperatures.

The invention solves this problem in that the cooling device has at least two cooling units and each cooling unit is set up to cool an associated partial winding, at least one partial winding having temperature ranges in which insulating materials with different thermal load capacities are arranged.

According to the invention, a thermal barrier in interaction with at least two cooling units ensures that at least two partial windings can be operated in different temperature sections, which are referred to here as cold room temperatures. The thermal barrier takes care of that Formation of at least two cooling spaces which are each connected to one of the cooling units. Within the scope of the invention, the cooling units can thus set different cooling space temperatures, that is to say different temperatures of the insulating fluid and / or the windings, in the cooling spaces connected to them. The cooling space temperature is expediently set in such a way that a maximum operating temperature predetermined for this cooling space is not exceeded. In this way it is possible to use different insulating materials in the cold rooms. In addition, for example, the partial winding that is arranged in a cooling space that allows higher cooling space temperatures can be designed to be low in insulating material.

In the context of the invention, there are advantages if a partial winding is arranged in the cooling space in which higher cooling space temperatures occur during normal operation, which partial winding is designed for lower operating voltages. Here, for example, the use of three-phase mains cable windings is possible.

According to the invention, the partial windings have different insulations. For example, a first part-winding has high-temperature insulation, while a second part-winding and all further part-windings have the usual insulation made of materials that are designed for lower temperatures. The term “insulation” here also includes barrier systems and spacers that are used in addition to the insulation of the winding conductors.

Furthermore, enamelled copper wires coated with various insulating varnishes, which can withstand even high temperatures, are available on the market. This also applies, for example, to a wire with a coating made of Pyre-ML-polyimide, which is thermally stable up to 220 ° C. Due to the small thickness of its lacquer layer, a good heat transfer from the wire to the insulating fluid is guaranteed.

Other partial windings which are arranged in a cooling space in which the insulating fluid has a lower cooling space temperature, however, are expediently equipped with the usual conventional, ie not high temperature resistant partial winding insulation or barrier systems.

In the context of the invention, the material of the insulating material is advantageously selected as a function of the position of the respective insulation in relation to the so-called hot point of the winding. A hotspot temperature is the hottest temperature of the electrical conductor of the partial winding which is in thermally conductive contact with the solid insulating material or the insulating fluid when the electrical device is in operation. Thus, for example, the conductor insulation is selected so that the material is not damaged even when the hot spot temperature is reached. In other words, the conductor insulation can withstand the maximum winding temperature. Solid insulation with a certain distance from the hottest points of the respective partial winding, on the other hand, can be assigned to a lower thermal class if the corresponding temperature gradient permits.

In the context of the invention, the cooling device has at least two cooling units, each cooling unit being set up to cool an associated cooling space. By using two cooling units, one of the cooling units can be connected to a partial winding via supply and discharge lines, for example, in such a way that the insulating fluid cooled by a cooling unit is circulated in a targeted manner via a selected partial winding and ensures that the required cooling room temperature is set in the cooling room .

Since different vertical distances to the yoke of the core are required due to the different voltages of the partial windings, the layered winding substructure can be used for the targeted supply of the insulating fluid to the selected partial winding. The insulating material disks of the substructure are expediently designed in such a way that that a separation of the flow of the insulating fluid to the respective partial windings is provided.

Due to the separation of the flow of the insulating fluid through the cooling spaces, the cooling circuits can be completely separated from one another in terms of flow, or they can partially use a common space. In terms of flow, this space can be in front of or behind the cooling rooms.

The thermal barrier advantageously forms an inlet opening which is connected to an outlet of the cooling device. This connection, or in other words the connection between the respective cooling unit and the inlet opening, can be designed as desired within the scope of the invention. It is essential that the main part of the insulating fluid flow emerging from the respective cooling unit reaches the inlet opening.

There are further advantages if the inlet opening is formed by a thermal barrier which at least partially defines a cooling space in which a high-voltage winding is arranged. Due to the higher voltage, the high-voltage winding is equipped with more complex insulation. In order to use conventional materials for the said insulation there, the high-voltage winding must be cooled more than the low-voltage winding, which is insulated with high-temperature materials.

In the context of the invention, the fluid-filled cooling spaces separated from one another by the barrier system are expediently hydraulically connected to one another. This connection can be made via the connection to a common expansion vessel used by both cooling chambers, or via a partially open design of winding substructures or winding superstructures.

According to a further development in this regard, the thermal barrier encloses a partial winding at least in sections. The thermal barrier is designed as a hollow cylinder, for example, and is arranged concentrically with at least one partial winding. According to this advantageous further development, the thermal barrier forms a guide or, in other words, cooling channels for the insulating fluid flow, so that the insulating fluid is guided over the partial winding. The cooling channels can be designed in a meandering shape.

According to an expedient further development in this regard, the thermal barrier is also an electrical barrier, at least in sections.

The first partial winding is expediently a low-voltage winding and a second partial winding is a high-voltage winding. The two windings are concentric with one another and, for example, also with a core section extending through the inner low-voltage winding. In other words, the electrical device according to this embodiment of the invention is a transformer with concentric upper and lower voltage windings as partial windings. The partial windings are advantageously designed as circumferentially closed cylindrical windings.

According to a variant in this regard, a first cooling unit for cooling the low-voltage winding and a second cooling unit for cooling the high-voltage winding are set up. As already stated, it is expedient here for the cooling device to apply colder insulating fluid to the high-voltage winding so that it can be operated at lower temperatures. The low-voltage winding and the high-voltage winding are in turn equipped with different insulating materials as partial winding insulation, which can withstand the different cold room temperatures.

In principle, the cooling spaces are hydraulically coupled to one another within the scope of the invention. According to an advantageous variant for this purpose, the cooling space in which the high-voltage winding is arranged is hydraulically connected to the cooling space in which the low-voltage winding is arranged via an expansion vessel.

According to a variant, a cooling unit is designed as a closed circulating cooling system, a pump being provided for circulating the insulating fluid. A second cooling unit is connected to the interior of the vessel, the first cooling unit and the interior of the electrical device being connected to one another only via an expansion vessel. According to this variant, a hydraulic connection of the cooling spaces takes place exclusively via the expansion vessel, which is absolutely necessary anyway due to the temperature-dependent volume expansion of the insulating fluid.

The gaps between the individual barriers and between the winding and the vessel, which are not required for cooling or for guiding the insulating fluid, can advantageously be closed by means of inserts to avoid bypasses.

As already stated, it is advantageous within the scope of the invention that the cooling device has a feed line which forms an outlet opening arranged below the first partial winding and in particular below the high-voltage winding. According to this variant, the cooled insulating fluid exits the cooling device via the supply line and is introduced directly into the cooling space of the first partial winding, so that the first partial winding is more strongly cooled than the further partial windings that are downstream of the first partial winding in the flow direction of the insulating fluid.

At least one cooling unit is advantageously connected to the winding substructure and / or winding superstructure of a partial winding in such a way that, during normal operation, the respective over the cooling units guided flows of the insulating fluid are separated from one another.

Each cooling unit expediently has at least one cooling register. The term cooling register should also include radiators here. At least one or each cooling unit can be a passive cooling unit or else have a circulation pump for circulating the insulating fluid via a cooling register. The cooling register can be equipped with one or more fans or fans.

According to a further variant, the cooling registers are connected to the vessel of the electrical device in such a way that they have different perpendicular distances from a floor surface defined by the base surface of the vessel. In other words, the cooling registers are attached to the vessel at different heights. In a further development in this regard, the cooling units are passive cooling units and do not have a circulation pump. In the case of passive cooling units, the circulation speed of the insulating fluid over the cooling register is determined by the height offset between the center of the warm fluid column in the cooling channels of the respective partial winding and the center of the cold fluid column of the respective cooling register. Since the partial windings are supported on the lower yoke of the core and thus have a fixed distance from the floor, this dependence of the circulation speed on the said height difference can also be described with the aid of the distance of the respective cooling register to the floor plane, which is defined by the bottom of the vessel .

Further components of the electrical device, for example step switches, are assigned to one of the two cooling circuits flowing through the cooling chambers according to their respective permissible operating temperature.

The cooling device advantageously has a control unit with temperature sensors, the temperature sensors are set up to detect the temperature of a partial winding and / or to detect the temperature of the insulating fluid in a partial winding. The control unit is, for example, equipped with a threshold value for each cooling unit, so that the cooling output of the respective cooling unit can be controlled as a function of the respective threshold value. The respective threshold value is determined depending on the temperature resistance of the insulating materials of the partial windings. If the temperature detected by the temperature sensors reaches the threshold value, the control unit controls either a circulating pump or a fan of the respective cooling unit and thus increases the cooling capacity of said cooling unit.

The temperature sensors are set up to detect the temperature of a partial winding and / or to detect the temperature of the insulating fluid. The temperature sensors can therefore also directly detect the temperature of the winding conductor within the scope of the invention.

According to a further variant, at least one partial winding has several temperature ranges in which insulating materials with different thermal load capacities are arranged. It can be advantageous here if insulating materials with a lower thermal load capacity are arranged in each upstream temperature range than in downstream temperature ranges which lie behind the upstream temperature range in the direction of flow of the insulating fluid.

In an expedient further development for this purpose, a temperature sensor for measuring a hot spot temperature is arranged in at least two temperature ranges, which provides temperature measurement values on the output side that are compared with a threshold value previously defined depending on the insulating materials used in the respective temperature range, a control signal being generated on the basis of this comparison becomes. Depending on the design, this can trigger a warning signal, cause shutdown, a reduction triggered by the load of the electrical device or used to control the cooling system.

According to the invention, operation at higher temperatures is made possible, with an expensive conversion, for example, of the winding parts rich in insulating material of a high-voltage winding to high-temperature insulating materials. In addition, a higher current density in the winding conductors and thus a significant reduction in size are possible. In the context of the invention, an increase in the temperature of the insulating fluid leads to a considerable increase in the temperature difference to the external cooling medium such as air or water. This increases the effectiveness of the cooling considerably, so that the electrical device according to the invention can be made more compact.

Due to the high viscosity of ester and silicone-based insulating fluids, there are also fluidic and cooling advantages when operated at higher temperatures. It is possible to optimize the losses for normal load, provided a high overload margin is provided.

For certain applications, the wide temperature spread of the insulating liquid enables the effective use of external evaporative coolers and coolers based on heat pipes.

Advantageously, several fluidically connected temperature ranges in the cooling room are equipped with sensors for measuring the hot spot temperature of the partial winding in the respective temperature range, the signals of each of these temperature sensors being assigned their own threshold values for triggering control functions which relate to the thermal class of the partial winding used in the respective temperature ranges Insulating materials are matched.

Figuren 1 bis 7

unterschiedliche Ausführungsbeispiele des erfindungsgemäßen elektrischen Geräts in einer teilweise geschnittenen Seitenansicht schematisch verdeutlichen.

Further useful refinements and advantages of the invention are the subject matter of the following description of exemplary embodiments of the invention with reference to the figures of the drawing, the same reference symbols referring to components that have the same effect and where

Figures 1 to 7

schematically illustrate different embodiments of the electrical device according to the invention in a partially sectioned side view.

Figure 1 shows a first exemplary embodiment of the electrical device 1 according to the invention in a sectional side view, the electrical device being designed as a transformer 1. The transformer 1 has a vessel 14 in which a magnetizable core 2, a low-voltage winding 3.1 and a high-voltage winding 3.2 are arranged concentrically to one another as part of the winding according to the invention. Said windings 3.1, 3.2 are designed as a hollow cylinder. The high-voltage winding 3.2 can be connected to a high-voltage network via a connection (not shown in the figures), and the low-voltage winding 3.1 can be connected to a distribution network or a load via a connection line, also not shown. The high and low voltage windings 3.1, 3.2 are inductively coupled to one another via the magnetizable core 2, so that the high voltage winding 3.2 induces a voltage in the low voltage winding 3.1 or vice versa.

The vessel 14 is filled with an insulating fluid 30 and, in the present case, a commercially available ester. A thermal barrier 4 is arranged between the high-voltage winding 3.2 and the low-voltage winding 3.1. The thermal barrier 4 is circumferentially closed and also designed as a hollow cylinder. It completely encloses the also cylindrical low voltage winding 3.1. An expansion vessel 18 is arranged above the vessel 14, which serves to absorb the temperature-related fluctuations in volume of the insulating fluid 30.

To cool the partial windings 3.1 and 3.2, a cooling device is provided which has two cooling units, a first cooling unit having a cooling register 15.1, a circulating pump 16.1 and a temperature sensor 22.1, a supply line 37.1 and a return line 38.1. The second cooling unit has a cooling register 15.2, a circulation pump 16.2, a temperature sensor 22.2, a supply line 37.2 and a return line 38.2. The feed line 37.1 has an outlet opening 32 which is arranged below the radially inner low-voltage winding 3.1. An inlet opening of the return line 38.1 is directly connected to a winding superstructure 9.1 of the winding 3.1. The winding superstructure 9.1 is fluidically sealed, which means that the flow of the insulating fluid 30 is guided by the winding superstructure. The return line 38.1 is connected to the expansion vessel 18 via a connecting line, which in turn is connected to the interior of the vessel 14 of the transformer 1 via a second connecting line. The supply line 37.2 of the second cooling unit opens with its outlet opening directly into the side wall of the vessel 14. The return line 38.2 is connected near the upper edge of the vessel. The inner wall of the thermal barrier 4 thus delimits a first cooling space in which the low-voltage winding 3.1 is arranged. The outer wall of the thermal barrier 4, together with the vessel 14, delimits a second cooling space in which the high-voltage winding 3.2 is located. According to the in Figure 1 The illustrated embodiment, the insulating fluid 30 cooled by the first cooling unit 15.1, 16.1, 37.1, 38.1 is fed via the sealed winding substructure 8.1 directly to the low-voltage winding 3.1 and from there directly back to the cooling register 15.1. In this exemplary embodiment, the hydraulic coupling of the cooling spaces takes place only via the expansion vessel 18. Different cooling space temperatures arise in the cooling spaces. The Insulations are adapted to these cold room temperatures.

The temperature sensors 22.1 and 22.2 are each connected to a control unit (not shown in the figures) via a signal line. If the temperature of the insulating fluid 30 detected by the temperature sensors 22.1 or 22.2 exceeds a threshold value previously set for the respective partial winding 3.1 or 3.2, the control unit increases the output of the circulating pump and thus the output of the respective cooling unit. The threshold values were determined depending on the thermal class of the insulating materials of the respective partial windings.

Figure 2 shows an embodiment of the electrical device 1 according to the invention, in which the hydraulic coupling of the cooling circuits takes place via the upper winding structures 9.1, 9.2 of the partial windings 3.1, 3.2, which are open at the top. A mixture of the insulating fluid 30 occurs above the partial windings 3.1 and 3.2. The insulating fluid 30 is cooled differently in the cooling units assigned to each partial winding 3.1, 3.2. Thus, in the cooling circuit for the partial winding 3.2, whose winding conductors are equipped with complex high-voltage insulation, a higher cooling effort is operated. In other words, the insulating fluid 30 is cooled to a lower temperature.

The cooling space of the partial winding 3.1 and the core 2 are included in the cooling circuit formed by the cooler 15.2.

The partial winding 3.1 with lower demands on its dielectric strength, which therefore has a low proportion of insulating materials compared to the other partial winding, is equipped with an insulation of a higher thermal class and can thus be operated at a higher temperature. Equipping this partial winding with high-temperature insulating materials only requires low costs. In the context of the invention, it is useful to have partial windings with a comparative low dielectric strength to operate at a higher temperature than the partial windings with a high dielectric strength.

The design of the core 2 for higher temperatures requires only very little effort, since no molded parts are required and an electrical field stress does not have to be taken into account. As a result, the core 2 is also exposed to higher operating temperatures.

The supply of the insulating fluid 30 cooled in separate cooling units to the partial windings 3.1 and 3.2 takes place via the winding substructure 8.1, 8.2 of the respective partial winding 3.1 and 3.2.

The winding substructure 8.1, 8.2 built up in layers in each case is used for the separate supply of the insulating fluid 30 to the partial windings 3.1, 3.2 separated by the thermal barrier. The insulating disks of the respective winding substructure 8.1, 8.2, not shown in detail here, are designed in such a way that a separation of the flow of the insulating fluid 30 to the respective partial windings 3.1 and 3.2 is provided.

To decouple the fluid flows, the winding substructures 8.1 and 8.2 are sealed against one another. Furthermore, at least one connecting line 37.1 is provided, which extends between the cooling unit 15.1, 16.1 and the winding substructure 8.2, so that the flow of the cooled insulating fluid is sealed off from the interior of the vessel 14. In the exemplary embodiment, the cooling register 15.1 is connected directly to the winding substructure 8.2 via a pipe 37.1.

In the exemplary embodiment, the spaces 40 between the partial windings 3.2 and the vessel 14 that are not required for cooling or for guiding the insulating fluid 30 are closed by means of enclosures 11.2 to avoid bypasses.

Figure 3 shows a further embodiment of the invention with two cooling spaces separated by the thermal barrier 4. The thermal barrier 4 comprises cylindrical sections 4.1 and 4.2 and a partition 4.5. In the embodiment shown, the thermal barrier 4 made of a thermally insulating material causes a thermal and fluidic decoupling of the radially outer partial winding 3.2 from the inner partial winding 3.1 and the core 2 of the transformer 1. In other words, the decoupling is achieved by separating the insulating fluid flows both cooling circuits achieved by means of the thermal barrier 4.

In the exemplary embodiment shown, an electrical barrier 7 is integrated into the barrier 4 as a section. For the thermal separation of the insulating fluid flow, the winding substructure 8.2 of the partial winding 3.2 is fluidically connected to the supply line 37.2, which leads to the cooler register 15.2 of the second cooling unit arranged outside the vessel. The radially inner partial winding 3.1 and the cooling channels of the core 2 are open to the fluid space of the vessel 14. Furthermore, the supply line 37.1 of the first cooling register 15.1 is connected to the vessel 14 at a level below the lower edge of the partial winding 3.1. The inner partial winding 3.1 and the core 2 are thus supplied with cooled insulating fluid 30 by a “free” flow that is not guided. In addition to a winding substructure 8.1 or 8.2, each partial winding has a winding superstructure 9.1, 9.2. Each winding superstructure 9.1 and 9.2 is open to the fluid space of the vessel 14. Through the openings of their winding superstructure 9.1, 9.2, both cooling spaces are hydraulically connected to one another via the interior of the vessel, ie the fluid space of the vessel 14.

In order to absorb the thermally induced fluctuations in volume of the insulating fluid 30, the interior of the vessel 14 and thus both cooling spaces are connected to the expansion vessel 18. It occurs within the said fluid spaces of the transformer 1 Due to the temperature dependence of the density of the insulating fluid 30 to form a thermal stratification of the insulating fluid 30. This thermal stratification is reinforced by the high viscosity of the insulating fluid 30 used and the very low flow velocities in the large cross section. In the special embodiment, this effect is used for the thermal separation of the two cooling circuits. For this purpose, according to the invention, the connection of the return line 38.2 to the cooling register 15.2 is arranged below the connection of the return line 38.1 to the cooling register 15.1. In order to avoid mixing of the insulating fluid 30 heated to different degrees, a further section 4.5 of the thermal barrier 4 is provided in the usually open area above the windings. This section 4.5 projects beyond the electrical barrier 7. In the exemplary embodiment, the vertical distance H5 from the upper edge of section 4.5 of the thermal barrier 4 to the return line 38.2 is a multiple of the flow-limiting diameter of the return line 38.2. This prevents insulating fluid 30, which has a significantly higher temperature and which has flowed through the low-voltage winding 3.1, from getting into the return line 38.2.

In order to avoid the formation of bypasses, potential undesired flow channels 10.5, for example between sections 7.5 of the barrier system 4 and the electrical barrier 7, are completely or partially closed at one of their ends by inserts made of insulating material.

In the exemplary embodiment shown, the partial windings 3.1 and 3.2 form vertically superposed temperature ranges 5.1, 5.2, 5.3 and 6.1, 6.2 within the cooling chambers, which are equipped with electrical insulation made of insulating materials that have a different thermal load capacity from temperature range to temperature range. Thus, the thermal load capacity of the insulating materials in the temperature range 5.1 through which the insulating fluid 30 first flows is lower than the insulating materials the downstream temperature ranges in the direction of flow. In addition, insulating materials of different thermal classes can be used at least partially within the temperature ranges. The thermal load capacity of an insulating material can be lower if it maintains the necessary distance to the hottest point of the temperature range, for example to a certain winding position. Thus, for example, the thermal class can be graded within a temperature range 5.1, depending on whether the insulating material is used as conductor insulation, spacer, potential control ring or barrier.

This arrangement can be used for a wide variety of insulating materials and thus different temperature ranges. An exemplary assignment of the thermal classes to the temperature ranges shown in the exemplary embodiment is given below. In the exemplary embodiment, an insulating fluid based on an ester is used.

Design example for a winding arrangement according to Fig. 3 (Thermal classes of insulating materials according to EN 60085: 2008) Temperature range 5.1 5.2 5.3 6.1 6.2 Conductor insulation B (130 ° C) F (155 ° C) H (180 ° C) E (120 ° C) B (130 ° C) Spacers E (120 ° C) B (130 ° C) F (155 ° C) A (105 ° C) E (120 ° C) Barrier system / potential control rings A (105 ° C) E (120 ° C) B (130 ° C) A (105 ° C) A (105 ° C)

The term “spacer” is intended to include radial and axial spacers such as strips, tabs, intermediate layers or the like. The term "barrier system" is intended to include barriers, angle rings, caps, discs, insulating cylinders or the like.

The grading of the thermal performance of the insulating materials can also be done within the thermal classes EN 60085, there is a multitude of possibilities, for example a graduation in differences of less than 10K is also possible.

Furthermore, in the exemplary embodiment, the hot spots of the temperature ranges are equipped with thermal sensors 25.1, 25.2, 25.3, 26.1, 26.2, which are each connected to a control unit (not shown in the figure). In the exemplary embodiment, a sensor 27, 28 for measuring the maximum temperature of the insulating liquid 30 is also arranged in the area of the respective outlet opening in the winding superstructure 9.1 or 9.2.

In Figure 3 five temperature ranges 5.1, 5.2, 5.3, 6.1, 6.2 are provided, each of which is equipped with insulating materials from 3 different thermal classes. This results in different permissible maximum temperatures for each temperature range. The insulating fluid 30 must not reach the maximum temperature permissible for the insulating fluid in the temperature ranges arranged at the front in the flow path, since otherwise the temperature gradient from the winding to the insulating fluid 30 in the winding regions through which the flow subsequently flows becomes too low for adequate cooling.

Since, as described, the permissible temperatures are different in the various temperature ranges, it makes sense to monitor the temperatures in the temperature ranges separately. In the exemplary embodiment, the hot spots of all temperature ranges are therefore equipped with thermal sensors and the signals are fed to a control unit. Each of these signals is assigned a threshold value tailored to the thermal class of the insulating materials of the corresponding winding area. If one of the temperature signals exceeds the threshold value assigned to it, a control signal is generated. Depending on the design, this can trigger a warning signal, shutdown and lower the load of the trigger electrical device or be used to control the cooling system.

Different threshold values for cooling system control, warning and triggering are preferably assigned to the signal of each temperature sensor 25.1, 25.2, 25.3, 26.1, 26.2.

Fig. 4 shows a further embodiment in which one cooling unit is designed as an active cooling unit and has a circulation pump 16.2, while the other cooling unit is a passive cooling unit 15.1, in which the insulating fluid 30 is circulated through the cooling register 15.1 due to a temperature difference that occurs.

In the exemplary embodiment shown, the winding 3.2 with the higher high-voltage requirements, that is to say the winding with a high proportion of insulating materials and insulating parts that are complex to manufacture, is forcefully cooled by the active cooling unit 15.2, 16.2. The partial winding 3.2 is again enclosed by cylindrical sections 4.1 of the thermal barrier 4. The cooled insulating fluid 30 is supplied via the fluidically sealed winding substructure 8.2, which is connected to the cooling unit 15.2 and the pump 16.2 via the supply line 37.2.

The vessel 14 is also connected to the cooling register 15.1. The more strongly cooled partial winding 3.2 is provided with insulating materials of a low thermal class. Since large differences in the temperatures of the insulating fluid 30 inside and outside the thermal barrier 4 occur during the operation of a transformer 1 shown, additional barrier sections 4.6 are provided which prevent fluid flow directly on the wall of the barrier 4.2 and thus reduce the thermal influence on the partial winding 3.2 . In the exemplary embodiment, electrical barriers and angular rings that follow the barrier section 4.2 are provided with shims which prevent the fluid flow within the channel between the barriers.

In this exemplary embodiment, only the partial winding 3.1 has two temperature ranges 5.1 and 5.2. Regarding the temperature ranges, the explanations apply Figure 6 here accordingly.

Figure 5 shows an embodiment of a transformer 1 with natural cooling (ONAN cooling). Here, the movement of the insulating liquid is caused by thermal lift. The insulating fluid 30 heated by the partial windings 3.1, 3.2 rises due to its lower density compared to the insulating fluid 30 in the wider vicinity of the winding and is replaced by cold insulating fluid 30 flowing in from below. The difference in weight between the warm column of liquid in the winding channels and the colder column of liquid in the cooling register 15.1 or 15.2 creates a pressure difference which serves as the driving force for the fluid circuit. In addition, a higher geometric arrangement of the cold insulating fluid column of the cooling register leads to an increase in the pressure difference that drives the coolant flow. This effect is used in the exemplary embodiment in order to supply a winding 3.1 with an increased pressure and thus a higher volume flow of the insulating liquid. For this purpose, the cooling register 15.1, which supplies the winding 3.1 with cooled insulating fluid, is arranged at a greater distance from the center of the winding 3.1 than the cooling register 15.2, which is provided for supplying the partial winding 3.2 and the core 2.

This height offset is described here - due to the fixed distance between the partial winding and a floor level defined by the bottom of the vessel - by the distance between the respective cooling register and the said floor level. These different heights are therefore taken into account here as the perpendicular distance H1, H2 of the respective cooling register 15.1, 15.2 to the floor plane which is defined by the floor of the vessel 14.

H1 is greater than H2. Since both partial windings 3.1 and 3.2 are supported on the lower yoke of the core 4, their centers are approximately the same height. Accordingly, the distance between the center of the first cooler 15.1 and the center of the first winding 3.1 is greater than the distance between the center of the second cooler 15.2 and the center of the second winding 3.2.

If this driving force is too high, then due to the flow resistance in the winding, there is a strong secondary flow of the insulating fluid 30 between the partial winding and the vessel wall of the transformer 1, which reduces the effectiveness of the cooling. In order to avoid this, in the exemplary embodiment the cooled insulating fluid 30 is supplied to the winding 3.1 connected to the higher-level cooling unit 15.1 via the winding substructure 8.1 which is fluidically sealed for this purpose.

The insulating fluid flow is thus adapted to the different operating temperatures of the two partial windings and their different flow resistances.

The cooling register 15.1 and / or 15.2 can be equipped with fans within the scope of the invention.

Figure 6 shows a further embodiment of the electrical device 1 according to the invention, which differs from that in Figure 5 The exemplary embodiment shown differs in that the cooling registers 15.1 and 15.2 are equipped with fans 17. The cooling register 15.1 and the cooling register 15.2 have a different number of fans 17. In addition, the cooling registers 15.1 and 15.2 are at the same height. The supply line 37.1 of the first cooling unit is arranged exactly below the first partial winding 3.1, that is to say the low-voltage winding. The thermal barrier 4, in contrast to that in FIG Figures 1 to 5 shown embodiments up to the upper wall of the vessel 14, wherein the return line 38.1 the cooling space inside the thermal barrier 4 with the cooling register 15.1 connects. The first cooling unit therefore again forms a closed, circulating cooling circuit, the hydraulic coupling between the first cooling space and the second cooling space, which is defined by the outer wall of the thermal barrier 4 and the inner wall of the vessel 14, taking place via the expansion vessel 18. The corresponding connecting lines are provided for this.

Since the thermal and fluidic separation of the windings also continues above the windings in the exemplary embodiment, both cooling rooms are each equipped with their own Buchholz relay 20 in order to monitor gas accumulations in both cooling rooms.

When the load on the transformer 1 increases, the temperatures rise differently in the two partial windings 3.1, 3.2 and are initially cooled without fan support (ONAN cooling). The fans 17 are switched on or controlled differently for each cooling circuit at different temperatures for the two subsystems.

In the exemplary embodiment, the cooling unit for the cooling space with the partial winding which is equipped with insulating materials of a lower thermal class is switched to fan operation at a lower temperature than the cooler for the partial winding with insulating materials of a higher thermal class. In order to be able to operate both partial windings at full load, the cooling register 15.2 has a larger number of fans 17 than the cooling register 15.2.

Figure 7 shows a further embodiment of the invention of the electrical device 1 according to the invention, which is essentially according to the embodiment Figure 1 corresponds, however, the cooling units 15.1 and 15.2 are each designed as passive cooling units, so that the cooling units each have no circulation pump.

Further components, not shown here, of the electrical device 1, for example step switches, are assigned to one of the two cold rooms according to their respective permissible operating temperature.

Claims (15)

1. Electrical device (1) for connecting to a high-voltage network, having

   - a vessel (14) which is filled with an insulating fluid (30),

   - an active part which is arranged in the vessel (14) and which has a magnetizable core (2) and partial windings (3.1, 3.2) for generating a magnetic field in the core (2), and

   - a cooling device (15) for cooling the insulating fluid (30), there being at least one thermal barrier (4) which delimits cooling spaces in each of which there is arranged at least one partial winding (3.1, 3.2), wherein the cooling device (15) has at least two cooling units, and each cooling unit is designed to cool an associated partial winding (3.1, 3.2), characterized in that at least one partial winding has, along the flow of the insulated fluid, temperature regions (5.1, 5.2, 5.3) in which insulating materials of different thermal loadability are arranged.
2. Electrical device (1) according to Claim 1,
   characterized in that
   the thermal barrier (4) forms at least one inlet opening which is connected to an outlet of the cooling device (15).
3. Electrical device (1) according to one of the preceding claims,
   characterized in that
   the thermal barrier (4) encloses a partial winding at least in certain portions.
4. Electrical device (1) according to one of the preceding claims,
   characterized in that
   the thermal barrier (4) is an electrical barrier at least in certain portions.
5. Electrical device (1) according to one of the preceding claims,
   characterized in that
   the first partial winding is a low-voltage winding (3.1) and a second partial winding is a high-voltage winding (3.2), wherein the windings (3.1, 3.2) are arranged concentrically to one another and to a core portion (2) extending through the inner low-voltage winding.
6. Electrical device (1) according to Claim 5,
   characterized in that
   a first cooling unit (15.1, 16.1) is designed to cool the low-voltage winding (3.1), and a second cooling unit (15.2, 16.2) is designed to cool the high-voltage winding (3.2).
7. Electrical device (1) according to Claim 6,
   characterized in that
   the cooling space in which the high-voltage winding is arranged is hydraulically coupled to the cooling space in which the low-voltage winding is arranged via an expansion vessel.
8. Electrical device (1) according to one of the preceding claims,
   characterized in that
   at least one cooling unit (15.1, 16.1) is connected to the winding base (8.1, 8.2) and/or winding top (9.1, 9.2) of a partial winding (3.1, 3.2) in such a way that the flows of the insulating fluid (30) that are in each case guided via the cooling units (15.1, 16.1) during normal operation are separated from one another.
9. Electrical device (1) according to one of the preceding claims,
   characterized in that
   each cooling unit (15) has a cooling register (15.1, 15.2).
10. Electrical device (1) according to Claim 9,
    characterized in that
    the cooling registers (15.1, 15.2) have different vertical spacings (H1, H2) from a bottom plane (35) defined by a bottom surface of the vessel (14).
11. Electrical device (1) according to one of the preceding claims,
    characterized in that
    the partial windings (3.1, 3.2) have different partial winding insulations.
12. Electrical device (1) according to one of the preceding claims,
    characterized in that
    the cooling device has a control unit with temperature sensors, wherein the temperature sensors are designed to detect the temperature of a partial winding and/or to detect the temperature of the insulating fluid in a partial winding.
13. Electrical device (1) according to Claim 12,
    characterized in that
    in each case a temperature sensor for measuring a hotspot temperature is arranged in at least two temperature regions (5.1, 5.2, 5.3) and provides temperature measurement values on the outlet side which are compared with a threshold value predetermined in dependence on the insulating materials used in the respective temperature region, wherein a control signal is generated on the basis of this comparison.
14. Electrical device (1) according to one of the preceding claims,
    characterized in that
    a plurality of fluidically connected temperature regions (5.1, 5.2, 5.3) in the cooling space are equipped with sensors (25.1, 25.2, 25.3) for measuring the hotspot temperature of the partial winding (3.1, 3.2) in the respective temperature region (5.1, 5.2, 5.3), and the signals of each of these temperature sensors are each assigned dedicated threshold values for triggering control functions which are tailored to the thermal class of the insulating materials used in the respective temperature regions (5.1, 5.2, 5.3) of the partial winding (3.1, 3.2).
15. Electrical device according to one of the preceding claims,
    characterized in that
    each of the fluidically and thermally separated partial windings (3.1, 3.2) has dedicated sensors for temperature monitoring of the winding temperature (25.3, 26.2) and/or sensors (27, 28) for measuring the maximum insulating fluid temperature in the thermally separated cooling spaces of the windings (3.1, 3.2), and the sensors are connected to a control unit which is provided with means for monitoring the observance of the admissible temperatures of the windings (3.1, 3.2) and/or of the insulating fluid (30), which are different for each cooling space, and for independently controlling the cooling units (15.1, 15.2) respectively assigned to a cooling space.

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