EP2511919A1 - Dry transformer heating - Google Patents

Abstract

The dry-type transformer (30) has a closed housing (32) provided with a transformer winding (34) and a transformer core (36). An insulating layer is formed around the transformer winding. The coil heating wires (40,44) are provided in insulating layer and are connected with transformer winding. An independent claim is included for encapsulated dry-type transformer.

Description

The invention relates to a dry-transformer heater, comprising a closed housing, at least one transformer winding arranged therein with at least one winding conductor each and an insulating layer surrounding each of these.

It is well known that in power distribution networks to adapt the voltage levels of various network components dry transformers are used. These have a power range of, for example, 100kVA to several 10MVA and are designed for nominal voltages between, for example, a few kV to 110kV. In contrast to oil transformers is dispensed with a liquid insulating, but for example, the windings of a solid insulating material, for example, a soaked in resin and subsequently cured Faserroving surrounded. In a three-phase transformer, three such windings are then arranged around a respective leg of a transformer core. To dissipate the heat loss generated during operation, cooling ducts through the windings are particularly necessary in a hot working environment to a greater extent.

For certain applications, it is necessary to encapsulate dry-type transformers, that is to say to arrange them within a closed housing. This may be the case, for example, with dry-type transformers operating within a very cold working environment or on a ship or an oil rig and against the effects of saline seawater. However, an encapsulation may occasionally be required alone because of their mechanical protection. In particular, in the event that an encapsulated transformer is subject to frequent use downtime due to use, it may lead to the formation of condensation inside the transformer housing, since the transformer then cools due to the lack of heating the winding losses. Even in continuous operation of a sealed transformer can cause condensation, if this is placed in a cold working environment that the winding losses do not lead to a sufficient heating of the transformer or of the housing, so that the dew point temperature is not exceeded. In this case, condensate collects on the inside surfaces of the housing or even on the surface of the windings at a longer standstill.

In order to avoid condensation phenomena within a transformer housing, it is therefore customary, if necessary, to install standstill heaters in the housing, for example heat radiators. These are usually arranged on both sides of the transformer core on the housing bottom due to a simplified arrangement and have an upwardly directed heating area. This has the consequence that the areas are heated on both sides of the transformer core and there the formation of condensation is avoided. However, the transformer windings and the housing area above it are not directly covered by the heating area, so that condensation may occur there, which may disadvantageously drip, in particular from the upper housing area onto the transformer windings underneath.

Based on this prior art, it is an object of the invention to provide an improved dry-transformer heating, which avoids this phenomenon. This object is achieved by a dry-type transformer heater of the type mentioned at the outset. This is characterized in that, in addition to the respective winding conductor, further means are provided for the direct primary introduction of a heat output into the respective insulation layer.

The designation of a housing in the context of this invention may mean both that the transformer winding is fixedly arranged in this housing and is movable therewith. But it is also meant that a transformer winding or even the entire transformer is arranged in a closed space, which actually does not belong directly to the transformer. This can be, for example, a locked room in the hull of a ship or even a room within a building.

Due to the direct primary entry of the heating power in the insulating layer of the transformer winding a local condensation is avoided in this particularly critical area, because there is provided specifically for a sufficient warming. In a particularly advantageous manner, however, the housing area is also miterwärmt over the transformer winding by the rising from the underlying, heated winding heat, so that a dripping of condensation on the transformer winding is avoided. The uncritical regions on both sides of the transformer core or the transformer windings are only indirectly covered by the heating effect on the insulation layer, so that it could indeed lead to condensation there. However, its dripping is harmless, since this takes place in an area where no windings are arranged.

According to a preferred embodiment of the dry-type transformer heating device, the means for the direct primary input of the heat output into the insulating layer can be regulated independently of the electrical operation of the transformer winding. This allows for both the operation of the dry-type transformer heating as pure standstill heating, as well as supplementary heating during transformer operation. The transformer windings are lossy, so that when operating the transformer in the transformer windings generates a heating power. Depending on the outside temperature and resulting power loss this may already be sufficient to prevent condensation, but if necessary, an additional heating power of the dry-transformer heating may be necessary. As a result of the controllability according to the invention, the means for the direct primary input of the heat output can be specifically controlled in such a way that a sufficiently high temperature above the dew point is ensured.

According to a further embodiment of the dry-type transformer heating according to the invention therefore at least one temperature sensor is provided and means to regulate the registered heat output such that the temperature of the insulating layer is above the respective dew point. Accordingly, a control and / or regulating device is to be provided, which predetermines the registered heating power as a function of the measured temperature in accordance with a specific control characteristic. Preferred arrangement points for one or more temperature sensors are the inner wall region of the housing above the transformer core or the transformer windings, because condensation occurring there would disadvantageously drip onto the high-voltage windings and in extreme cases could lead to a short circuit or other fault, for example.

According to a particularly preferred embodiment of the dry-type transformer heating according to the invention, at least one coil heating wire is arranged on the surface of the insulating layer as a means for the direct primary input of the heat output. A Spulenheizdraht is an electrical conductor, which heats up due to its internal resistance during flow of an electric current accordingly. A daily application to the insulating layer of a transformer winding is not critical, if necessary, this can also be a suitable temperature-resistant and thermally conductive adhesive can be used. Due to the insulating layer, which surrounds the transformer winding, no isolation problems with the winding conductor of the transformer winding are to be expected. In this way, a targeted heat input is made possible on the surface of the high-voltage winding that is particularly critical with respect to condensation. Preferably, the Spulenheizdraht is flat, in particular with predominantly parallel track distances, arranged on the surface, so that it can be heated according to homogeneous.

In accordance with a further embodiment of the dry-type transformer heater according to the invention, at least one coil heating wire is arranged within the insulation layer. This must then be inserted in the production of the insulation directly into this, which is technically but unproblematic production, because appropriate winding machines for the production of the transformer winding anyway available stand. An insulating layer usually consists of a multi-layer wound resin-impregnated fiber roving, wherein the Spulenheizdrähte are then bring relatively close to the surface. In this way, the heating wires are on the one hand protected by the insulating layer, on the other hand, a more homogeneous distribution of a demand-generated heating power is guaranteed. Incidentally, the advantages of a coil heating wire arranged in this way correspond to the advantages of a heating wire arranged on the coil surface. Of course, a combination of both arrangement variants is possible or else the arrangement of several Spulenheizdrahtten to the same high-voltage winding.

In a further preferred embodiment of the dry-type transformer heating, at least one coil heating wire is laid at least in sections in meandering fashion. This allows a particularly homogeneous heating of the corresponding portion of the surface of the high-voltage winding or of its surrounding insulating layer.

According to the invention, it is also provided that the spacing between adjacent Spulenheizdrahtabschnitte is compressed in certain areas of the insulating layer, which applies to both Spulenheizdrähte within the insulating layer and outside of the insulating layer. Thus, in surface areas in which a higher entry of heat output makes sense, for example at the terminals of the high-voltage winding, a surface area with denser coil heating wires is provided. In less critical areas, it is sufficient to lay the coil heating wires less tightly.

In accordance with a further embodiment of the dry-type transformer heater according to the invention, at least one coil heating wire is electrically connected to a winding conductor of the transformer winding. For isolation reasons, the arrangement of the Spulenheizdrähte within the insulation layer is preferable here. In this way, the Spulenheizdraht is set to a defined potential and further reduces the risk of insulation breakdowns to the winding conductor. It should be noted, however, that a voltage source which is provided for a current flow through the Spulenheizdraht must also be set to the conductor potential. This is not always advantageous.

Therefore, it is provided according to a further embodiment of the dry-type transformer heating according to the invention that at least one Spulenheizdraht an electrically short-circuited loop is formed, which is arranged such that when operating the transformer winding, a voltage in the loop is induced. This has accordingly at least in sections a Wickelsinn, which corresponds to that of the winding conductor of the transformer winding.

According to a further embodiment of the invention, the electrically short-circuited loop is variable in its electrical resistance by a series-connected electrical component. Such a component may for example be a switch, by means of which the winding can be activated as needed. But it can also be a variable resistor or a power electronic circuit, which fulfills this purpose. The latter is characterized in particular by a good controllability.

According to a further variant of the invention, an electrical voltage source is provided for generating a current flow through at least one heating wire. Depending on the control functionality to be implemented, this can either be a constant voltage source or else a controllable voltage source.

In accordance with a further embodiment of the invention, at least one UV emitter directed onto the insulation layer is provided. This is arranged for example on an inner side wall of the housing. The UV rays generate a heat input when they hit the insulation layer directly. In the case of a three-phase transformer, on each side of each of the three windings at least one such UV radiator is necessary, that is to say in total of at least six.

The advantages mentioned for the dry-transformer heating naturally also apply to an encapsulated dry-type transformer comprising a transformer core and a dry-transformer heater, wherein in each case at least one transformer winding is arranged around one of preferably three limbs of the transformer core. In an arrangement of a plurality of transformer windings, these are together with the associated transformer core in a common Housing arranged, which ultimately also a common heating system can be provided. Preferably, however, each transformer winding or the surrounding insulating layer is provided with respective means for recording a heat output.

Further advantageous embodiment possibilities can be found in the further dependent claims.

Reference to the embodiments illustrated in the drawings, the invention, further embodiments and other advantages will be described in detail.

Fig. 1

einen Schnitt durch einen ersten gekapselten Trockentransformator,

Fig. 2

einen Schnitt durch einen zweiten gekapselten Trockentransformator sowie

Fig. 3

einen Schnitt durch einen dritten gekapselten Trockentransformator.

Show it:

Fig. 1

a section through a first encapsulated dry-type transformer,

Fig. 2

a section through a second encapsulated dry-type transformer as well

Fig. 3

a section through a third encapsulated dry-type transformer.

Fig. 1 shows a lateral section 10 through a first encapsulated dry-type transformer according to the prior art. In a common closed housing 12, a dry-type transformer is arranged, of which the transformer core is designated by the reference numeral 16 and a transformer winding arranged above a leg of the transformer core 16 is designated by the reference numeral 14. On both sides of the dry transformer at the bottom of the housing 12, two heating elements 18, 20 are arranged, which in two respective radiating areas indicated by the reference numerals 22 and 24 irradiate the lateral areas of the housing 12, but not the dry-type transformer located therein. In the irradiated and thus heated side areas condensation is indeed avoided, but especially in the middle upper region of the transformer housing, just above the dry transformer is not made for a sufficient entry of heat output, so that there is a condensation, as indicated by the reference numeral 26. This can disadvantageously drip on the underlying transformer and so for example lead to short circuits or malfunction of the dry-type transformer.

Fig. 2 shows a lateral section 30 through a second encapsulated dry-type transformer according to the invention. In a housing 32, a dry-type transformer with a transformer core 36 and a transformer winding 34 is shown, behind which two further invisible transformer windings are arranged. On the surface of the transformer winding 34, two areas 38 and 42 are indicated, in each of which a Spulenheizdraht is arranged meandering. In the first region 38, a narrow meandering shape 40 is selected, while in the second region 42 a further meandering shape 44 is selected. The entry of heat output per surface unit is thus correspondingly higher in the first region 38.

The heated transformer coil 34 outputs, primarily by rising of heated at the outer surface of the insulating layer of air, a portion of the registered thermal power to the located above the transformer roof part of the transformer housing 32, which is then also heated, as indicated by the radiating region with the reference numeral 48 , Therefore, especially at the particularly critical housing area above the transformer such a high temperature is reached that its temperature is above the respective dew point temperature. In the uncritical and unheated side areas within the housing, the formation of condensation is indicated at the respective ceiling areas by the reference numeral 46. However, this is harmless because it drips into areas of the housing 32 where no transformer winding is arranged.

Fig. 3 shows a section 50 through a third encapsulated dry-type transformer in a plan view. In a closed housing 58 three hollow cylindrical transformer windings 52, 54, 56 are arranged side by side, wherein a corresponding transformer core is not shown for illustrative reasons. The transformer windings 52, 54, 56 are surrounded radially on the outside by a respective insulation layer 60. Within this layer, a plurality of Spulenheizdrähte are indicated by the reference numeral 66, which are arranged in this example along the axial extent of the respective transformer windings. Of course, an arrangement transverse to this is conceivable, especially if a short-circuited induction loop is to be formed. With this it becomes possible, at Operation of the transformer without an additional voltage source to provide an entry of heat output in the insulating layer 60.

The transformer winding with the reference numeral 56 is hinted at the side of an infrared heater 62, as indicated by the reference numeral 64. Also in this way a direct primary energy input into the insulating layer 60 is possible.

LIST OF REFERENCE NUMBERS

10

Section through a first encapsulated dry-type transformer

12

first closed housing

14

first transformer winding

16

first transformer core

18

first heating element

20

second heating element

22

first emission area

24

second emission area

26

Condensation over transformer winding

30

Section through a second encapsulated dry-type transformer

32

second closed housing

34

second transformer winding

36

second transformer core

38

Area with first to be entered heat output

40

Coil heating wire in first meander shape

42

Area with second heat output to be entered

44

Coil heating wire in second meander shape

46

Condensation next to transformer winding

48

third emission area

50

Cut through third encapsulated transformer

52

third transformer winding

54

fourth transformer winding

56

fifth transformer winding

58

third closed housing

60

insulation layer

62

An infrared heating element

64

fourth radiation area

66

Spulenheizdraht

Claims (13)

Dry-type transformer heating, comprising a closed housing (12, 32, 58), at least one disposed therein transformer winding (14, 34, 52, 54, 56) having at least in each case one winding conductor and with a these respective surrounding insulation layer (60), characterized in that in addition to the respective winding conductor further means for direct primary entry of a heat output in the respective insulating layer (60) are provided. Dry-transformer heater according to claim 1, characterized in that the means for direct primary entry of the heat output in the insulating layer (60) independently of the electrical operation of the transformer winding (14, 34, 52, 54, 56) are controllable. Trockentransformatorheizung according to claim 2, characterized in that at least one temperature sensor is provided and that means are provided to regulate the registered heat output such that the temperature of the insulating layer (60) is above the respective dew point. Dry-transformer heater according to one of the preceding claims, characterized in that at least one Spulenheizdraht (40, 44) on the surface of the insulating layer (60) is arranged. Dry-transformer heater according to one of the preceding claims, characterized in that at least one Spulenheizdraht (66) in the insulating layer (60) is arranged. Dry-transformer heater according to one of claims 4 or 5, characterized in that at least one Spulenheizdraht (40, 44, 66) is at least partially laid meandering. Dry-transformer heater according to one of claims 4 to 6, characterized in that the distance between adjacent Spulenheizdrahtabschnitte in certain areas (38, 42) of the insulating layer is compressed. Dry-transformer heater according to one of claims 4 to 7, characterized in that at least one Spulenheizdraht (40, 44, 66) is electrically connected to a winding conductor of the transformer winding (14, 34, 52, 54, 56). Dry-transformer heater according to one of Claims 4 to 8, characterized in that an electrically short-circuited loop is formed by at least one coil heating wire (40, 44, 66), which is arranged in such a way that during operation of the transformer winding (14, 34, 52, 54, 56) induces a voltage in the loop. Dry-transformer heater according to claim 9, characterized in that the electrically short-circuited loop is variable by an electrical component connected in series in their electrical resistance. Dry-transformer heater according to one of claims 4 to 10, characterized in that an electrical voltage source for generating a current flow through at least one heating wire (40, 44, 66) is provided. Dry-transformer heater according to one of the preceding claims, characterized in that at least one of the insulating layer (60) directed UV emitter (62) is provided. An encapsulated dry type transformer comprising a transformer core (16, 36) and a dry transformer heater as claimed in any one of claims 1 to 12, wherein at least one transformer winding is disposed about one of preferably three legs of the transformer core.

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