EP2490230B1 - Insulation support strip - Google Patents

Description

The invention relates to an insulation strip, comprising a beam-like base module with preferably a rectangular-like cross section of a solid insulating material and at least one of its two ends provided fastening means. The invention also relates to an insulating truss and an oil transformer with inventive insulation strip.

It is well known that transformers having a rated power of 100 MVA and higher at a rated voltage of 110 kV and higher, for example also 800 kV, are usually designed as oil transformers having a weight of 200 t and higher. In this case, the active part of the transformer with iron core and windings is arranged inside a transformer vessel filled with oil, the oil serving both the electrical insulation and the improved cooling. The electrical connection of the respective terminals of the active part of the transformer with the Ausleitungsisolatoren on the outside of the oil boiler takes place here by electrical conductors which are surrounded at high voltages by a lying at the same potential, insulated shield tube, the isolation of either solid insulating materials or of a barrier system is formed. The barrier system is constructed radially symmetrical about the respective conductor and comprises an electrically conductive screen tube with, if necessary, a plurality of nested spaced isolation barriers. The barrier systems required for each individual conductor are located inside the oil-filled transformer tank passed through a gap formed between the transformer and boiler wall, but isolation-related minimum distances must be adhered to.

For reasons of mechanical stability and short-circuit strength, the insulated shield tubes and the other diversion components are to be supported or held at specific intervals, ie mechanically connected to, for example, the outer wall of the boiler or a suitable region of the transformer or supported by a support frame. For this purpose, support strips are used, among other things, which are to be made of an electrically insulating material. These are usually tubular support elements made of a plastic, which are connected to each other by means of respective - optionally articulated - connecting elements. The insulating ability of a support strip as such is less than the insulating ability of pure oil with identical isolation distance.

Thus, in the patent EP2445071 A1 discloses a vertical holder for high voltage leakage in oil transformers, which is particularly flexible and space-saving. This document is state of the art under Article 54 (3) EPC.

The disadvantage, therefore, that especially at high voltages of 380kV and reinforced in the range of 800kV and higher, the distances between the Ausleitungskomponenten to the adjacent Ölkesselwandungen or the active parts of the transformer due to insufficient insulation capacity of the support strips are to increase accordingly disproportionately. Otherwise, there is the danger of breakdowns along the creepage path, which is formed on the surface of the support strips or other insulation components. The oil-filled tank volume is thereby increased in a negative way and the power density of the oil transformer is disadvantageously reduced.

Based on this prior art, it is an object of the invention to provide an insulation strip strip for Ausleitungskomponenten in oil transformers, which is characterized by a particularly high isolation capability and flexibility.

This object is achieved by an insulation carrier strip according to claim 1.

The basic idea of the invention is to advantageously extend the respective creepage path along the surface of the insulation support strip according to the invention by milling the circumferential slots. An inventive slit in the Isolationsstrageleiste preferably rotates these on all their outer sides in a respective plane. The cross section of an insulating strip is preferably rectangular, but may also be circular, for example. Depending on the size of the oil boiler in which it is to be installed, the length of such an insulating support bar is, for example, 2 m with a square cross section of, for example, 10 cm by 10 cm.

As a starting material for such Isolationstrageleiste an easily milled material such as pressboard is suitable. Through the use of modern milling technologies can be milled from a monolithic press chip block or bar almost any array diversity for the circumferential slots, which may for example have a depth of 20mm for example, with a width of 10mm. The insulating ability of a slot, which is milled into a smooth surface itself, is higher than the insulating ability of a, for example, corrugated surface. As a result of the virtually unlimited possibilities of milling in slots according to the invention along the extension of the basic module, areas of the insulating carrier strip which prove to be particularly critical with respect to the field strength loading can be provided with a higher density of preferably identically shaped slots than areas which are less than one prove critical. Suitable, for example, 4 cm slot spacing in a critical range and 8cm to 15cm in a less critical area. Optionally, the slots in a longer section of the insulating support strip according to the invention can also be cut in a particularly high density, for example every 2 cm to 4 cm. As a result, an insulation strip strip according to the invention can be used particularly flexibly.

The attachment means at the ends of the insulation support bar are not necessarily designed as separate components, but may also include molded or chamfered geometries suitable for making a mechanical connection.

According to a preferred embodiment of the insulation strip strip according to the invention, an area with connecting means for further components to be supported is provided in the basic module. Such other components are, for example, supporting or holding elements for other transformer components such as discharge pipes or tap changers or else further insulation strips, which are then joined together to form an insulating support structure. Connecting means are, for example, holes that allow screwing, in which case screw should be used from an insulating material such as pressboard. But connecting means may for example also include a milled notch or the like, whereby then a positive connection with an adapted further component or another component is made possible.

According to a particularly preferred embodiment of the invention Isolationstrageleiste at least one U-shaped insulation plate is fitted positively into one of the circumferential slots. This means that an insulating strip with a rectangular cross-section is surrounded by the insulating plate from three sides, wherein preferably the fourth, open side of the insulating plate is designed to be overhanging. Due to the form-fitting fitting of the insulation plate whose plate thickness accordingly corresponds to the thickness of the partially circumferential slot, for example 8 mm, it can be easily pushed from one side edge to the desired slot and fixed with a suitable adhesive, for example casein, so that a force and form-fitting, Kriechwegfeste connection is given. The adhesive serves primarily to avoid that a creepage path can form over the slot. In order to be able to arrange one and the same form of insulating plates in different orientations in the respective slots, a square or even circular cross section of the insulating carrier strip is particularly suitable, wherein in the former an arrangement in a grid of 90 ° is possible.

However, by the required for this particularly simple way of handling recess in the insulation plate is a side edge of the insulation strip bar just not provided with a Kriechwegverlängernden barrier. Therefore, it is provided according to the invention to fit at least two U-shaped insulation plates in a common or in a respective separate slot, which in their orientation transversely to the elongated extent of the basic module are rotated against each other. For example, if four insulation plates are disposed in respective adjacent slots of a square-section insulation support bar twisted by 90 ° each, each of the four side surfaces along this isolation portion is covered three times by an insulation plate. In this way, a still homogeneous insulation along the Isolationstrageleiste is possible.

However, this embodiment also includes the option that two insulation plates are rotated against each other in the same slot, which then has accordingly twice the thickness of an insulating plate. This ensures that all side surfaces of the insulation strip strip are provided with a circumferential barrier. In order to avoid gaps in which breakdowns could develop, the insulation plates which partly collide at their two-dimensional sides are preferably also to be glued there. An insulation plate is similar to an insulation strip preferably made of a milled insulation material, such as pressboard.

According to a further embodiment of the invention Isolationstrageleiste the provided at least at one end of the basic module fastener in turn is connected to an insulation adapter module. An insulation support bar may have a considerable height, for example 3m, when provided as a vertical support on the inner sidewall of an oil boiler for a transformer. In order to enable a simplified installation of such an insulation strip, insulation adapter modules can be connected in advance as mounting elements, for example, with a part of the inner boiler wall during assembly. These are then arranged so that an insulation strip with their mutually provided fasteners can be easily connected to the respective insulation adapter modules.

According to the invention, it proves to be particularly advantageous if the connection between fastening means and insulation adapter module has a positive tongue and groove connection. Thus, an insulation strip with groove or spring can be particularly easily inserted into an insulation adapter module with a corresponding spring or groove. Slippage of such a connection can, for example be achieved by a fixing bolt or a fixing screw of an insulating material.

Preferably, the fastening means of the insulation strip strip or the insulation adapter module on their respective side facing away from the base module on a slot-like and open on one side mounting groove. This fastening groove serves to establish a connection with a fastening element which is fastened, for example, to a boiler wall or welded there. Such a groove, which is open at the side, allows the production of a mechanical connection by pushing laterally onto a bolt-like fastening element.

In a preferred variant of the invention, such a fastening element is designed rod-like and positively fitted with its one end into the slot-like fastening groove. The cross section of this rod-like fastening element has, for example, the shape of an elevated circular cross-section, so that a rectangular cross-sectional segment is provided between two semicircular cross-sectional segments. In conjunction with the slot-like groove thus results in a variable compensation option for any tolerance dimensions in boiler construction.

The object according to the invention is also achieved by an insulating stringer comprising a plurality of insulation strands according to the invention directly or indirectly interconnected. Such Isolationstraggerüst can serve in addition to the recording of diversion pipes or barriers and the inclusion of, for example, a tap changer. The advantages of such a framework correspond to those of an insulation strip according to the invention, namely a space saving by an improved insulation capacity.

According to a particular embodiment of the insulating truss, this comprises a bridge-like holder for a discharge pipe of an oil transformer. This preferably has a U-shape, which also has an advantageous effect on the extension of the creepage path. Likewise, in order to improve the insulation capacity, optional circumferential slots are also provided along the extension of the preferred manner made of a milled insulation material bridge-like holder provided in which also U-shaped insulation plates can be fitted.

The object of the invention is also achieved by an oil transformer, comprising at least one oil boiler and a transformer arranged therein with winding and core, wherein the oil transformer further comprises an insulating strip according to the invention or an inventive Isolationstraggerüst. Advantageously, the oil tank can be made smaller due to the then more compact arrangement, for example, the discharge components in its oil-filled interior.

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

eine exemplarische erste Isolationstrageleiste,

Fig. 2

ein exemplarisches erstes Isolationsadaptermodul,

Fig. 3

eine U-förmige Isolationsplatte,

Fig. 4

eine exemplarische zweite Isolationstrageleiste sowie

Fig. 5

ein exemplarisches Isolationstraggerüst.

Show it:

Fig. 1

an exemplary first insulation stringer strip,

Fig. 2

an exemplary first insulation adapter module,

Fig. 3

a U-shaped insulation plate,

Fig. 4

an exemplary second isolation stringer bar as well

Fig. 5

an exemplary isolation truss.

Fig. 1 shows an exemplary first Isolationsstrageleiste 10 in a plan view 10a and in a rotated by 90 ° thereto side view 10b. On both sides of a beam-like base module 12 ends 14, 16 are formed, which have respective fastening means, in this example a groove 22 and holes 24. These fasteners are used to attach the Isolationstrageleiste 10 either directly with a provided inside the boiler fastener or with an insulation adapter module, which quasi as an intermediate piece between the fastening element and Isolationstrageleiste serves and, if necessary, a simplified installation allows.

Along the extension of the insulation support strip a plurality of transverse thereto extending in a respective plane slots 18 are provided, which for example have a width of 12mm and a depth of 30mm. These serve on the one hand the extension of the creepage path along the outer surfaces of the insulation strip but on the other hand also the optional inclusion of U-shaped insulation plates, by which the insulation capacity of the insulation strip individually and, if necessary, can be further increased.

In the upper area connecting means 20 are provided to connect components to be supported therewith. The connecting means consist in this example of two holes through which screws or bolts can be inserted, so that thus a non-positive connection to other components with corresponding counterbores can be produced.

Fig. 2 shows an exemplary first insulation adapter module 30 in a three-dimensional perspective view. This has essentially a parallelepiped-like basic shape, which is adapted in its cross section to the cross section of an insulating strip to be joined thereto. At the in the connected state of the insulation strip side facing side a cuboid spring 32 is formed, which in turn is adapted in shape to a corresponding groove in the Isolationstrageleiste, so that thus a tongue and groove connection can be produced. To fix this connection, two bores 34 extending through the spring 32 are provided, which correspond with two bores of the groove of the insulation strip strip, not shown. Thus, a bolt or a screw can be introduced there in a simple manner, wherein these are preferably made of an insulating material.

On the side facing away from the spring of the insulation adapter module 30, a slot-like fastening groove 36, which is open on one side, is provided. This is suitable for receiving a rod-like fastener with an elongated circular cross-section, which with one of its two ends form-fit in the Fixing groove 36 is fitted. A transverse bore 38 is provided to fix the rod-like fastener in the mounting groove 36.

Fig. 3 shows a U-shaped insulation plate 50, which is preferably made of an insulating material such as pressboard and is positively fit into a slot of a matching Isolationstrageleiste square cross-section is fitted. The U-shaped insulation plate has a square base, is symmetrical to the axis of symmetry 52 and can be fitted in four different, each offset by 90 ° orientations on an associated Isolationsstrageleiste square cross section. The edges of the insulation plate 50 are rounded as roundings 54 to exclude any field strength problem.

The Fig. 4 shows an exemplary second isolation bar 60 in a plan view 60a and in a 90 ° rotated side view 60b. The insulation support strip 60 substantially corresponds to that in the Fig. 1 shown Isolationstrageleiste 10, but an insulation adapter module 66 and 68 are respectively provided at both ends thereof, which are fastened by means of a tongue and groove connection and are to be regarded as an extension of the insulation support bar 60 quasi. Rod-like fastening elements 70, 72 are provided on the respective ends of the insulation adapter modules 66, 68 facing away from the tongue-and-groove connection, which engage positively and non-positively in corresponding fastening grooves of the insulation adapter modules 66, 68 which are open to one side. Such fasteners 70, 72 may, for example, be intrinsically welded to the lower and upper boundaries of an oil boiler, such that an insulation stringer 60 may be mounted or inserted therebetween, similar to a column.

In the upper region of the insulation support strip 60, two bores are provided, which serve for connection to components to be held or with further insulation strips. Since these components are usually directly or indirectly connected to a component carrying a voltage, the connection region around the bores is mostly field strength critical. In order to increase the field strength loadability around this particularly critical area, corresponding U-shaped insulation splices 62, 64 are fitted in adjacent circumferential slots. To creep on all sides of the Isolationstrageleiste caused by this increase the U-shaped insulation plates are divided into a first group 62 and a second group 64, which are arranged in an alternating arrangement rotated by 180 °.

Fig. 5 shows an exemplary isolation truss frame 80 in a plan view. Between two vertically arranged insulating strips 82, 84 a bridge-like holder 86 is arranged, which carries a screen tube 88 in its center. By its U-shaped configuration of the creepage along the extension of the bridge-like holder 86 is extended in an advantageous manner. Around the connecting portion with the bridge-like holder 86, the insulation supporting strips 82, 84 are provided with U-shaped insulation plates fitted in respective slits. These selectively increase the creepage path in the region of the isolation lintels 82, 84, which are particularly field strength critical. Thus, the insulation strips 82, 84 have been individually improved with respect to their respective boundary conditions with regard to their insulation behavior.

LIST OF REFERENCE NUMBERS

10

exemplary first insulation stringer strip

10a

exemplary first isolation stringer bar in top view

10b

exemplary first Isolationstrageleiste in side view

12

exemplary bar-like basic module

14

first end of insulation bar

16

second end of insulation strip

18

circumferential slots

20

Connecting means for other components to be supported

22

groove

24

drilling

30

exemplary first insulation adapter module

32

feather

34

drilling

36

slot-like attachment groove open on one side

38

drilling

50

U-shaped insulation plate

52

axis of symmetry

54

curve

60

exemplary second insulation stringer

60a

exemplary second isolation bar strip in top view

60b

exemplary second Isolationstrageleiste in side view

62

first group of U-shaped insulation panels

64

second group of U-shaped insulation panels

66

second insulation adapter module

68

third insulation adapter module

70

first rod-like fastener

72

second rod-like fastener

80

exemplary insulation truss

82

third insulation stringer strip

84

fourth insulation stripe strip

86

bridge-like holder

88

screen tube

Claims (11)

1. Insulation support strip (10, 60, 82, 84) for high-voltage outgoing line components in oil transformers, comprising a beam-like basic module (12), with a preferably rectangular cross section, of a solid insulation material and with fastening means (22, 24) provided at at least one of its two ends (14, 16), wherein a number of adjacent slots (18) are provided, at least in certain portions, transversely in relation to the longitudinal extent of the basic module (12), running around said module on the outer sides thereof in a respective plane, characterized in that at least two U-shaped insulation plates (50, 62, 64) that are turned with respect to one another in their alignment transversely in relation to the longitudinal extent of the basic module (12) are fitted in a form-fitting manner in a common or respective slot (18).
2. Insulation support strip according to Claim 1, characterized in that a region with connecting means (20) for further components (86) to be supported is provided in the basic module (12).
3. Insulation support strip according to Claim 1 or 2, characterized in that it is produced from an insulation material that can be cut by milling.
4. Insulation support strip according to one of the preceding claims, characterized in that the fastening means (22, 24) provided at least at one end (14, 16) of the basic module (12) are for their part connected to an insulation adapter module (30, 66, 68).
5. Insulation support strip according to Claim 4, characterized in that the connection between the fastening means (22, 24) and the insulation adapter module (30, 66, 68) has a form-fitting tongue- (32) and-groove (22) connection.
6. Insulation support strip according to one of the preceding claims, characterized in that the fastening means (22, 24) and the insulation adapter module (30, 66, 68) have on their respective side facing away from the basic module (12) a fastening groove (36) that is similar to an oblong hole and is open on one side.
7. Insulation support strip according to Claim 6, characterized in that it also comprises at least one bar-like fastening element (70, 72), which is fitted by its one end in a form-fitting manner in the fastening groove (36) similar to an oblong hole.
8. Insulation support strip according to Claim 7, characterized in that the at least one bar-like fastening element (70, 72) has the cross section of an elongated circle.
9. Insulation support framework (80), comprising a number of insulation support strips (10, 60, 82, 84) according to one of Claims 1 to 8 that are directly or indirectly connected to one another.
10. Insulation support framework according to Claim 9, characterized in that it comprises a bridge-like holder (86) for an outgoing pipe (88) of an oil transformer.
11. Oil transformer, comprising at least one oil tank and a transformer arranged therein with a winding and a core, characterized in that the oil transformer also comprises an insulation support strip (10, 60, 82, 84) according to one of Claims 1 to 8 or an insulation support framework (80) according to either of Claims 9 and 10.

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