EP3316268A1 - Transformer with heated radiator element - Google Patents

Abstract

An electrical appliance (5) for connection to a high-voltage network comprising a boiler (6) which is filled with an insulating fluid (7) and in which a magnetizable core (8) and at least one portion (10) of the core (8) enclosing winding (9) are arranged, and a Kühlanlange (11) comprising at least one radiator (1), which is outside of the boiler (6) and connected thereto for circulating the insulating fluid (7) via the radiator (1) wherein the radiator (1) has at least two heat exchange members (3) connected in parallel to accelerate a cold start and can also be carried out at lower temperatures, it is proposed that only one of the heat exchange members (3) be used as a heated heat exchanger member (3). 12) is in heat-conducting connection with a heat source which generates heat upon starting the operation of the electrical device (5).

Description

The invention relates to an electrical device for connection to a high-voltage network with a boiler, which is filled with an insulating fluid and in which a magnetizable core and at least one winding enclosing a portion of the core are arranged, and with a cooling system comprising at least one radiator, is disposed outside of the boiler and connected thereto for circulating the insulating fluid through the radiator, wherein the radiator has at least two heat exchange members connected in parallel.

The invention further relates to a method for cold starting an electrical device.

Such a device and such a method are known to those skilled in the art. For example, transformers have a boiler filled with insulating fluid, in which a magnetizable core is arranged. The core forms a leg, which is arranged concentrically to a surrounding undervoltage and high-voltage winding. The insulating fluid is used for electrical insulation of the lying at a high voltage potential during operation of the electrical device windings relative to the lying at ground potential boiler. In addition, the insulating fluid provides the necessary cooling of the windings. For this purpose, the insulating fluid heated by the windings is circulated via radiators mounted on the outside of the boiler.

The viscosity of the insulating fluid is temperature dependent and increases very sharply at decreasing temperatures. Due to the increased viscosity, at low outside temperatures, below -10 ° C, the circulation of the insulating fluid through the radiator (s) is impaired. This is particularly problematic after prolonged standstill of the electrical device, since the insulating fluid is then completely cooled. The high viscosity is to be considered in view of the reduced cooling capacity of the cooling system during cold start of the electrical device, since the windings can otherwise be overheated.

For example, a transformer is started at idle or under reduced load. If the electrical equipment has active cooling, pumps for circulating the insulating fluid via the radiator can not be switched on until the insulating fluid in the boiler has exceeded a minimum temperature threshold. However, in some cases this temperature threshold is only reached after a few days.

In addition, more and more alternative insulating fluids, such as esters and silicone oils are used in electrical appliances of the type mentioned above. Although ester oils as insulating fluids have improved environmental compatibility. The disadvantage, however, is that they can have such a high viscosity at temperatures in the range of below -10 that a cold start of the electrical device has become virtually impossible.

The object of the invention is therefore to provide an electrical device and a method of the type mentioned, with which a cold start can be inexpensively accelerated and performed at lower temperatures.

The invention solves this problem, starting from the electrical device mentioned above in that only one of the heat exchange members is as a heated heat exchange member in heat-conducting connection with a heat source which generates heat when starting the operation of the electrical device.

Based on the above-mentioned method, the invention solves the problem in that in an electrical device of the type mentioned only one of the heat exchange members is heated as a heated heat exchange member by means of a heat source.

According to the invention, there is provided an electrical appliance which utilizes the heat energy provided by a heat source to facilitate the cold start to selectively heat a single heat exchange member of a radiator. As a result of this heating, the heated heat exchange member heats up so that, in the case of a cold start, the insulating fluid is initially conducted after a short time exclusively via the heated heat exchange member. The circulation of the heated insulating fluid through the heated heat exchange member provides there for an additional increase in temperature. From the thus heated Wärmeaustauchglied the heat is transferred gradually to the other heat exchange members.

In the context of the invention, the heating of a single heat exchange member is sufficient to bring the heating of the electrical appliance in motion. The additional effort in the manufacture of the electrical device or the implementation of the method according to the invention is therefore limited to a minimum. High additional costs are avoided according to the invention. In addition, the invention allows the use of alternative insulating fluids in colder climates.

The design of the cooling system is basically arbitrary within the scope of the invention. Thus, the cooling system may be a so-called active cooling system having pumps for circulating the insulating fluid over the radiator (s). Deviating from this, the cooling system can also be a passive cooling system, in which the movement of the insulating fluid is caused solely by thermal buoyancy. The insulating fluid heated by the winding (s) increases due to its lower density relative to the heated fluid and is replaced by inflowing colder insulating fluid. The difference in weight of the differently heated liquid columns in the winding channels or in the boiler on the one hand and the cooling system on the other hand generates a pressure difference, which serves as a driving force of the fluid circuit.

In a passive cooling system based on a natural flow of the insulating fluid, the circulation in the cooling system begins by heating the insulating fluid in the heated heat exchange member because the resistance in the form of a highly viscous insulating fluid is reduced to such an extent that the driving pressure differential drives the circulation.

In the case of a pumped oil flow, heating quickly reaches a temperature level that allows the pumps to be switched on. The power required by the pump during cold startup is reduced.

The term heat exchange member is to be understood in the context of the invention, a hollow body through which the insulating fluid is passed. With its outside, the heat exchange member is in heat-conducting contact with the outside atmosphere, so that the heat of the heated insulating fluid can be discharged via the wall of the heat exchange member to the outside atmosphere. To improve the heat transfer, the heat exchange member consists of a material with a high thermal conductivity, for example of a suitable metal. The heat exchange is further improved when the heat exchange member forms a large heat exchange surface. Thus, the heat exchange member, in other words the radiator member, for example, plate-shaped and has mutually parallel plates or panels. The panels can each delimit meandering flow channels through which the insulating fluid is passed.

By contrast, each heat exchange member is tubular and has one or more mutually parallel tubular heat exchange elements. Tubular elements also have a large surface area.

The radiators may be equipped in the invention with fans or fans, with which the cooling of the insulating fluid can be further improved.

According to an advantageous variant of the invention, the heat source is an electric heating source. The electric heating source is connected to start a cooled electrical device to a power supply, so that there is a heating of the heated heat exchange member. As already stated, the insulating fluid is then passed substantially over the heated heat exchange member, whereby its temperature gradually increases further and is thus provided for radiating the heat to the remaining heat exchange members.

According to an expedient further development, the electric heating source forms heating wires which rest against the heated heat exchange member. Heating wires are inexpensive available on the market and easy to bring in contact with the heat exchanger member to be heated. This variant is therefore particularly inexpensive. Heating wires can also be easily retrofitted and even attached during operation.

In a variant of the invention deviating from this, the heat source is the boiler filled with insulating fluid, the boiler and / or the insulating fluid being heat-conductively connected to the heated heat exchanger member via at least one heat pipe. According to this variant of the invention, a separate electric heating source has become superfluous. Instead, the heating of the boiler, which occurs when the operation is started under reduced load, is utilized in order to reduce the viscosity of the insulating fluid in the heated heat exchanger element. Thus, the electrical device is started, for example, at idle, which essentially comes to a heating of the core. The heated winding provides for heating of the surrounding insulating fluid and conventional convection for heating the boiler housing. The in the Boiler or the insulating fluid existing heat is transmitted by means of at least one heat pipe to the heated heat exchange member.

Heat pipes, so-called "heat pipes", essentially have a hermetically encapsulated housing in which a working medium, such as water, is in the liquid and gaseous phase. In the heat pipe, for example, a capillary structure is further arranged, for example. If the heat pipe is heated at its heat receiving end, the liquid present there evaporates and passes through the gas phase to the colder heat release end. This is where condensation starts, releasing heat. The condensed liquid working medium is transported via the inner capillary structure back to the heat receiving end of the heat pipe.

A heat pipe is thus a heat exchanger with which high heat flows can be transmitted at a low temperature difference. The or each heat pipe is connected according to this development either with the insulating fluid within the boiler heat-conducting or with the boiler itself. The heat of the insulating fluid or the boiler ensures evaporation of the working fluid within the heat pipe and for the transport of the gaseous working fluid to the colder end of the heat pipe, which emits due to the heat-conducting compound resulting in condensing condensation enthalpy to the heated heat exchange member.

According to an expedient further development, each heat pipe with its heat-receiving end in contact with the outer wall of the boiler, wherein the heat-emitting end of the heat pipe is in contact with the heated heat exchange member. In other words, the heat pipe is directly adjacent to the boiler and to the heated heat exchange member. When arranging a heat pipe outside the boiler, the oil compatibility of the heat pipe need not be checked. Furthermore is also a risk of electrical equipment due to damage to the heat pipe impossible.

Advantageously, a plurality of heat pipes are provided in the context of this variant. In addition, it is possible even equipped electrical equipment, such as transformers or reactors, which are set up for connection to a high voltage network, subsequently equipped with externally mounted on the boiler heat pipes, so as the cold start behavior of the respective transformer or the respective throttle in the frame to improve the process of the invention.

Suitably, each radiator has an upper inlet and a lower return, which are each connected to the boiler via the heat exchange members, wherein the heated heat exchange member has the smallest distance to the boiler. The heat exchanger member with the smallest distance to the boiler is referred to in the context of the invention as the innermost heat exchange member. Due to the small distance, the innermost heat exchange member can be heated easily and inexpensively.

According to an expedient further development in this regard, a plurality of heat pipes, ie at least two heat pipes are provided, which extend in the region of the upper inlet and possibly also in the region of the lower return between the heated heat exchanger member and the boiler. For the start of the electrical device, it is advantageous to distribute the heat supply over the entire heat exchange member. Although, in stationary operation, a natural flow only occurs in the heated heat exchange member when the temperature of the insulating fluid in the external radiator is lower than the temperature of the insulating fluid in the boiler. Excessive heating of the heated heat exchange member could therefore result in a reduced recirculation rate. However, it was recognized that despite the good heat transfer of the heat pipes during normal operation, a sufficient temperature difference between the insulating fluid in the boiler and in the heated heat exchanger member sets.

In the context of the invention, it is expedient to provide a plurality of heat pipes in the upper region, ie in the region of the inlet of the radiator, since the boiler has the higher temperatures in this region.

According to a further embodiment of the invention, the heated heat exchange member is at least partially enclosed by a heat-damping layer. This thermal insulation simplifies and accelerates the heating of the insulating fluid in the heated heat exchange member.

Conveniently, the cooling system is a passive cooling system. As already stated, passive cooling systems do not have pumps, radiators or the like.

Deviating from this, however, the cooling system is an active cooling system, in particular radiators or radiator batteries with fans or fans are used in the invention.

Preferably, the electrical device in the invention comprises a cooling system which has a plurality of radiators, but only one radiator is equipped with a heated heat exchange member. The heated heat exchange member accelerates the heating of the first radiator. However, the heating radiates from this to the other radiators of the cooling system.

In an advantageous variant of the method according to the invention, the heated heat exchange member is heated by means of an electric heating source. It is particularly useful if the electric heating source forms heating wires.

According to a preferred variant of the method according to the invention, the heated heat exchange member is heated by means of at least one heat pipe through the warming during cold start boiler, each heat pipe between the boiler and the heated heat exchange member is arranged.

Figur 1

einen handelsüblichen Radiator in einer Seitenansicht,

Figur 2

ein Wärmeaustauschglied des Radiators gemäß Figur 1 in einer Draufsicht und

Figur 3

ein Ausführungsbeispiel des erfindungsgemäßen elektrischen Geräts in einer schematischen Seitenansicht zeigen.

Further embodiments and advantages of the invention are the subject of the following description of embodiments of the invention with reference to the figures of the drawing, wherein like-working components are provided with the same reference numerals, and wherein

FIG. 1

a commercial radiator in a side view,

FIG. 2

a heat exchange member of the radiator according to FIG. 1 in a plan view and

FIG. 3

an embodiment of the electrical device according to the invention in a schematic side view show.

FIG. 1 shows an embodiment of a commercially available radiator 1 in a schematic side view. It can be seen that the radiator 1 has an upper inlet 2, which is hydraulically connected to a return 4 via heat exchange or radiator members 3. The inlet 2 and the return 4 each have a left-facing inlet or outlet opening, via which the radiator 1 after its assembly with the interior of an in FIG. 1 not shown boiler communicates. The insulating fluid of the said boiler can then be circulated via the inlet 2, the heat exchanger members 3 and the return 4 via the radiator 1 with its heat exchanger members 3. The heat exchange members 3 are made of a thermally conductive material, such as a metal, and are in thermal contact with the outside atmosphere. Is the insulating fluid passed over the heat exchange members, Thus, heat is released from the heated insulating fluid to the colder outside atmosphere.

FIG. 2 shows a heat exchange member 3 in an end view. It can be seen that the heat exchange members 3 are plate-shaped. In other words, the in FIG. 1 shown radiator 1 to a so-called plate radiator. The plate-shaped heat exchange members 3 respectively delimit flow channels through which the insulating fluid circulated via the heat exchange members 3 is guided. Finally, the insulating fluid enters the collecting return line 4 and passes from there as a cooled insulating fluid back into the interior of the boiler.

FIG. 3 shows an embodiment of the electrical device 5 according to the invention, which is designed here as a transformer. The transformer 5 has a boiler 6, which is filled with an insulating fluid 7. In addition, in the boiler 6, a magnetizable core 8 and windings 9 are arranged, of which in the FIG. 3 however, only one winding is indicated schematically. However, the windings 9 here comprise a so-called high-voltage winding and a so-called low-voltage winding, which are arranged concentrically to a leg 10 as the core 8. However, the operation of such a transformer is known to the person skilled in the art, so that at this point will not be discussed in more detail. The necessary connection cables for connecting the windings to a high-voltage network are likewise not shown figuratively for reasons of clarity.

The transformer 5 is equipped with an outside of the boiler 6 mounted cooling system 11, the only one radiator 1 according to here FIG. 1 includes. It can be seen that the inlet 2 and the return 4 open into the interior of the boiler 6. Since the inlet 2 and the return 4 are connected to each other via heat exchanger members 3, a circulation of the insulating fluid 7 is made possible via the radiator. A heat exchange member 3, the smallest distance to the boiler. 6 has, so-called innermost radiator member 12 is connected via schematically indicated heat pipes 13 in heat-conducting connection with the outer wall of the boiler. 6

After a longer standstill of the electrical device 5, the insulating fluid 7 is completely cooled. In particular, at low outside temperatures, for example in the range of -10 to -50 degrees, the insulating fluid 7 has such a high viscosity, in other words so viscous that it is no longer circulated through the radiator 1 even after a long startup. For this reason, the heat pipes 13 are provided, with which an improved heat transfer between the boiler 6 and the innermost heat exchange member 12 is provided. Thus, in the context of the invention, the high-voltage winding of the windings 9 are connected to the high-voltage network. The undervoltage winding, however, is applied to an appropriate resistor, so that the transformer 5 is not operated under full load. A portion of the resulting heat is transferred by means of the heat pipes or heat pipes 13 to the heated heat exchange member 12, which is heated so including the insulating fluid 7 disposed therein. The temperature of the heated heat exchange member 12 is thus higher than that of the outer heat exchange members 13. The viscosity of the insulating fluid in the heated heat exchange member therefore decreases. Nevertheless, a temperature difference between the insulating fluid 7 within the boiler 6 and the insulating fluid within the heated heat exchange member 12, so that it comes to a pressure difference and thus to circulate the insulating fluid through the innermost heat exchange member 12 due to the different density of the insulating. In this case, continuously warmed insulating fluid passes through the supply line 2 to the heated heat exchange member 12, wherein a gradual heating of the other outlying heat exchange members 3 takes place. Finally, the insulating fluid 7 also passes over the more external heat exchange members 3 circulated. The transformer can then be operated under full load.

Finally, it should be noted that the load control during cold start can be arbitrary within the scope of the invention. Deviating from the above-mentioned reactions of the cold start, the electrical device according to the invention can also be started under full load.

Claims (13)

Electrical device (5) for connection to a high voltage network with - A boiler (6) which is filled with an insulating fluid (7) and in which a magnetizable core (8) and at least one portion (10) of the core (8) enclosing winding (9) are arranged, and - A cooling system (11) comprising at least one radiator (1) disposed outside of the boiler (6) and connected thereto for circulating the insulating fluid (7) via the radiator (1), wherein the radiator (1) at least has two heat exchange members (3) connected in parallel, characterized in that only one of the heat exchange members (3) as a heated heat exchange member (12) is in heat conducting connection with a heat source which generates heat upon starting the operation of the electrical apparatus (5). Electrical device (5) according to one of the preceding claims,
characterized in that the heat source is an electrical heating source. Electrical device (5) according to claim 2,
characterized in that the electrical heating source comprises heating wires which rest against the heated heat exchange member. Electrical device (5) according to claim 1,
characterized in that the heat source of the filled with insulating fluid boiler (6), wherein the boiler (6) and / or the insulating fluid (7) via at least one heat pipe (13) with the heated heat exchange member (12) is thermally conductively connected. Electrical device (5) according to the preceding claim,
characterized in that each heat pipe (13) contacts a heat receiving end of an outer wall of the boiler and a heat emitting end of the heated heat exchange member (12). Electrical device (5) according to one of the preceding claims,
characterized in that each radiator (1) has an upper inlet (2) and a lower outlet (4), which are connected to each other with the boiler (6) and via the heat exchanger members (3), the heated heat exchanger member (12) being having the smallest distance to the boiler (6). Electrical device (5) according to claim 6,
characterized in that heat pipes (13) extend both in the region of the upper supply line (2) and in the region of the lower return line (4) between the heated heat exchange member (12) and the boiler (6). Electrical device (5) according to one of the preceding claims,
characterized in that the heated heat exchange member (12) is at least partially enclosed by a thermal barrier coating. Electrical device (5) according to one of the preceding claims,
characterized in that the cooling system is a passive cooling system. Electrical device (5) according to one of the preceding claims,
characterized in that the cooling system comprises a plurality of radiators, but only one radiator has a heated heat exchange member. Method for cold starting an electrical appliance which comprises a boiler (6) filled with an insulating fluid (7) and in which a magnetizable core (8) and at least one winding (9) enclosing a section (10) of the core (8) are provided ), and a cooling system (11) comprising at least one radiator (1) disposed outside the boiler (6) and connected thereto for circulating the insulating fluid (7) via the radiator (1), the Radiator (1) has at least two mutually parallel heat exchange members (3), wherein only one of the heat exchange members (3) is heated as a heated heat exchange member (12) by means of a heat source. Method according to claim 11,
characterized in that the heated heat exchange member (12) is heated by means of an electric heating source. Method according to claim 11 or 12,
characterized in that the heated heat exchange member (12) is heated by at least one heat pipe (13) by the cold start heating boiler (6), each heat pipe (13) disposed between the boiler (6) and the heated heat exchange member (12) becomes.

Images