EP3001433B1 - Pin-isolator adapted for a transformer - Google Patents

Description

The invention relates to a feedthrough system for a connection of a dry-type transformer with externally grounded shielding, the coil winding of which is equipped with connections and taps, comprising a substantially circular-cylindrical post insulator and a connection inner conductor that extends through the post insulator and for the passage of a connection through the post insulator serves.

A dry-type transformer is a transformer that does not contain liquid insulating materials such as e.g. B. contains transformer oil. Dry-type transformers are usually used as power transformers, in particular as such in electrical power networks. They are therefore often designed as a three-phase alternating current transformer. Dry-type transformers are used particularly where, due to the physical proximity to people or property, oil-filled transformers cannot be used or only with significant fire protection measures, such as e.g. B. fire protection walls can be set up. There is also no need for oil collection pits to protect the groundwater.

As with liquid-filled transformers, dry-type transformers are usually designed with two-leg or three-leg iron cores made of electrical sheets insulated on both sides. The legs, which are provided with the coil windings, are connected to one another on both sides by yokes. To increase safety, it is known to provide the legs with an outer shield that completely encloses the legs, is made of an electrically conductive material, and is grounded.

With such a dry type transformer with an externally grounded shield, it is necessary to provide appropriate openings for the connections of the coil windings, since the connections are usually arranged laterally on the legs. The connections must be routed through the shielding, which is usually done using appropriate support insulators with a lead-through connection inner conductor, by means of which the connection is carried out on the outside of the shielding.

Transformers can be designed with taps on the coil windings on both the primary and secondary sides. The taps are used to adapt and use the transformer to different voltages. What was said above about the connections also applies to the taps on the transformer: these must also be routed through the shielding in appropriate support insulators.

For geometric reasons, however, appropriate space is required for this. Therefore, the tap often has to be positioned on the opposite side of the connections. This may not be possible due to a lack of space at the installation site. In such cases no taps could be provided.

The US 3,611,132A discloses a so-called plug-in bushing used for passing a high-voltage conductor through a grounded wall of a distribution transformer. The distribution transformer has a tank that is filled with insulating oil, which is intended both for insulation and for cooling the active part of the transformer, which is also located in the tank. The bushing has a rotationally symmetrical insulator through which a single high-voltage conductor extends. The insulator thus enables the high-voltage conductor to be routed through the tank, which is at ground potential, in a fail-safe manner.

The U.S. 3,001,005A also discloses a bushing having a rotationally symmetrical insulator through which a high voltage conductor extends longitudinally. This implementation also serves to insulate the high-voltage conductor through a wall of a transformer tank that is at ground potential.

The CA 830640A discloses a bushing system used to connect an oil-immersed transformer that has a grounded shield on the outside.

It is therefore the object of the invention to provide a bushing system of the type mentioned at the outset which allows the use of taps with a particularly space-saving configuration of a dry-type transformer.

This object is achieved according to the invention by the characteristics of claim 1.

The invention is based on the consideration that an additional post insulator for taps could be avoided by routing the taps together with the connections through the shielding through a common post insulator. For this purpose, the post insulator should have an additional inner conductor that is connected to the tap. The additional tapping inner conductor is electrically separated from the connection inner conductor by means of a corresponding spatial separation within the post insulator with insulating material lying between them.

In an advantageous embodiment of the feedthrough system, the post insulator has a plurality of tapped-through inner conductors for feeding through the shielding in each case with a tap. More taps lead to even greater flexibility of the transformer in terms of adapting to different voltages. The relocation of several tapping bushings into a joint bushing with the connection eliminates space problems that occur here.

In a further advantageous embodiment, a contact point connected to the connecting inner conductor of the post insulator and a contact point connected to the respective tapping inner conductor for each of the tapping inner conductors are arranged at an outer end of the post insulator. A covering cap of this type, which is screwed or plugged onto the post insulator, allows the external lines to be connected in a particularly simple manner.

Advantageously, contact points are arranged radially around a central contact point, i. H. the connecting lines between the contact point and connection and taps are arranged in a fan-like manner. This makes it particularly easy to connect the external cabling to the taps or the connector: the external cabling can remain permanently connected to the central contact point while only a straight, conductive connection is made from the central contact point to the contact point of the connector or one of the contact points of the tap connections must. In particular, this enables a simple change during operation.

In this case, an insulating material is advantageously arranged between the contact points, so that the electrical isolation is optimized.

In a further advantageous embodiment, the bushing system comprises a disc-shaped shielding ring which is made from an insulating material and encloses the post insulator in a flush manner. Because of the risk of breakdown, on the outside of the dry-type transformer, a large distance must be maintained between the external connection and the tapping connections on the post insulator and the shielding. This requires the use of correspondingly long post insulators, which protrude far out of the shielding on the outside. A disc-shaped shielding ring can be used to achieve a shorter distance between the external connection and the shielding, and thus a shorter post insulator can be used.

The shielding ring encloses the post insulator flush. On the one hand, this achieves a gapless, electrically tight insulation for the shielding, which on the other hand is easy to attach.

For reasons of symmetry, the shielding ring is advantageously in the form of a circular disk in order to ensure adequate insulation in all spatial directions. The shielding ring advantageously has more than three times the diameter of the post insulator. This refers to the bushing system seen from the axial direction of the post insulator. The shielding ring thus extends from the edge of the post insulator in each radial direction at least over a further diameter of the post insulator.

In an advantageous embodiment, the shielding ring tapers towards its outer edge. As the distance from the inner conductor of the post insulator increases, the distance between a point on the surface of the shielding and the connection on the post insulator increases, so that a smaller insulating thickness is required. The taper makes the shielding ring lighter and therefore more mechanically stable.

In a further advantageous embodiment, the shielding ring is made of cast resin. Casting resin has the advantage that it can be shaped completely flexibly due to the liquid processing. The shielding ring can thus be cast in a mold in a simple manner. Casting resin also has the high resistance required for this application and a corresponding dielectric strength.

A dry-type transformer with an outer grounded shield advantageously comprises a bushing system, as described above, arranged in a connection opening of the grounded shield. The shielding ring is arranged on the outside of the grounded shielding, which encloses one leg of the dry-type transformer.

Advantageously, the tapping inner conductors are connected to a winding in the area of the turn of the dry transformer associated with the connection inner conductor. In other words: the taps are arranged in the area of the winding end, i. H. near the winding associated with the transformer terminal. This ensures that the taps are at a similar potential as the connection.

Advantageously, the inner conductor for the tap and the inner conductor for the connection have a relative potential difference of less than 10%. This ensures that the inner conductors of the taps and connection, which are routed through the common post insulator, have only a small potential difference and breakdowns are avoided.

A dry transformer designed according to the aforementioned type is advantageously designed for a rated voltage of more than 1 kV and/or a rated power of more than 50 kVA. In the case of dry-type transformers of this power class in particular, the design of the bushing system described above, with a common bushing for connection and taps, is of considerable advantage.

The dry transformer is advantageously designed as a cast resin transformer, i. H. the insulation of the high-voltage windings consists of cast resin.

The advantages achieved with the invention are in particular that by carrying out the taps and the connections in a common post insulator of a dry-type transformer, a significant space saving can be achieved and the dry-type transformer can thus be used much more flexibly with regard to its installation location.

• FIG 1 ein Durchführungssystem für einen Anschluss und mehrere Anzapfungen eines Trockentransformators mit äußerer geerdeter Abschirmung im Längsschnitt,
• FIG 2 das Durchführungssystem in radialer Aufsicht, und
• FIG 3 einen Trockentransformator mit entsprechenden Durchführungssystemen an jedem seiner seitlichen Anschlüsse.

An embodiment of the invention is explained in more detail with reference to a drawing. Show in it:

• FIG 1 a feedthrough system for one connection and several taps of a dry-type transformer with externally grounded shielding in longitudinal section,
• FIG 2 the feedthrough system in radial plan view, and
• 3 a dry-type transformer with appropriate bushing systems on each of its side terminals.

Identical parts are provided with the same reference symbols in all figures.

The bushing system 1 described below is designed for cast-resin transformers with a nominal voltage of more than 1 kV and/or a nominal power of more than 50 kVA and accordingly has a corresponding size. It is therefore particularly suitable for power transformers in electrical energy networks.

The implementation system 1 is in the FIG 1 shown in longitudinal section. The inside of the transformer is located on the left, the outside on the right. The central, supporting component is a circular-cylindrical support insulator 2 (post), parallel to the axis of which is an electrical connecting inner conductor 4 and spaced apart from one another a total of four electrical tapping inner conductors. On the outside, the post insulator has a flange 6 at some distance from its outer end. The rest of the post insulator 2 is made of an insulating material known to those skilled in the art.

Connection inner conductor 4 and tapping inner conductor 5 are connected to a winding of the transformer in a common area, ie only a few turns apart from one another. The connection is designed in such a way that the tapping inner conductor 5 has a relative potential difference of -5%, -2.5%, +2.5% and +5% to the connection inner conductor 4 have.

The main purpose of the post insulator 2 is to enable electrical contact to the wire windings inside the transformer. This is because they are surrounded by a grounded, metallic shield that is applied as a conductive earth covering 8 to the cast resin coil 6 . This has a circular opening on the post insulator 2 , the diameter of which essentially corresponds to the outer diameter of the post insulator 2 . The post insulator is cast in one piece with the coil 6 and, like the coil 6, is partially covered by a layer of earth 8 that extends along the jacket of the post insulator 2 over a short distance to an O-ring 10 that extends in a groove extends circularly around the whole post insulator 2. The O-ring 10 is made of a conductive material.

The O-ring 10 is followed by a tapered but still circularly symmetrical section 12 of the post insulator 2. A shielding ring 14 is pushed onto the tapered section 12 of the post insulator 2 from the end, which is essentially shaped like a circular ring. The shielding ring 14 has an inner cylinder-jacket-shaped opening, the inside diameter of which essentially corresponds to the outside diameter of the post insulator 2 in the tapered section 12, but both components are designed for a press fit. The shielding ring 14 is rotationally symmetrical. Its outer diameter is about three times the outer diameter of the post insulator 2.

The axial thickness of the shielding ring 14 at its central opening is only slightly less than the axial length of the tapered section 12 of the post insulator 2. The shielding ring 14 is tapered in thickness towards its outer diameter. It is made entirely of cast resin.

At the outer end of the post insulator 2, ie in the outer base area of the cylinder, the connecting inner conductor 4 and the tapping inner conductor 5 are connected to exposed contact points 16. These are only covered by a cover cap 18 . Position and arrangement of the contact points 16 are based on the FIG 1 and the FIG 2 described.

FIG 2 shows the bushing system 1 from direction A, ie axially from the outside, below the covering cap 18. The circular diameter of the shielding ring 14 and of the post insulator 2 can be seen. The end base area of the post insulator 2 is also shown.

A central contact point 20 is arranged offset from the central axis of the post insulator 2 on the end base. This is only superficially provided and no inner conductor connects directly to this contact point 20 . An external cable 24 with insulation 26 is attached to the central contact point 20 by means of a screw 22 through the covering cap 18 .

The contact points 16 are evenly spaced in a radial pattern about the central contact point 20 on the end footprint, i. H. the connecting lines between each of the contact points 16 and the central contact point 20 form a uniform fan. Raised walls 28 made of insulating material are arranged between the contact points 16 and are made in one piece with the covering cap 18 .

A metal rod 30 in the length of the distance between contact points 16 and central contact point 20 can be used to establish a connection from central contact point 20 and thus from cable 24 to one of contact points 16, i.e. either to one of the tap inner conductor 5 or to the connection inner conductor 4 become. The other possible positions of the metal rod 30 are shown in dashed lines.

3 finally shows a dry transformer 38, which is designed as a cast resin transformer. It has an iron core made of layers of electrical steel. The iron core of the dry-type transformer 38 has three mutually parallel limbs wound with wire windings, each of which is surrounded by a grounded shielding 40 in the shape of a cylinder jacket. The legs are connected to one another at their ends by yokes 42 .

On each of the legs there are two lateral connection openings for connections and taps of the inner wire windings in the shielding 40, which are formed with the bushing system 1 described above. The connection openings are each in the middle of the upper and lower halves of the legs.

Claims (9)

1. Lead-through system (1) for a terminal of a dry transformer (38) with external earthed shielding (40), the coil winding of which dry transformer is equipped with terminals and taps, comprising a substantially circularcylindrical post insulator (2) and a terminal inner conductor (4) as well as at least one tap inner conductor (5) which extend through the post insulator (2) and serve for leading a terminal through the post insulator (2), wherein a contact point (16) connected to the terminal inner conductor (4) of the post insulator (2) and, for each of the tap inner conductors (5), a contact point (16) connected to the respective tap inner conductor (5) are arranged at an outer end of the post insulator (2),
   characterized in that
   the contact points (16) are arranged radially around a central contact point (20) to which no inner conductors are connected.
2. Lead-through system (1) according to Claim 1, in which the post insulator (2) has a plurality of led-through tap inner conductors (5) for leading in each case one tap through the shielding (40).
3. Lead-through system (1) according to Claim 1 or 2, in which an insulating material is arranged between the contact points (16).
4. Lead-through system (1) according to one of the preceding claims, which comprises a disc-shaped shielding ring (14) which is produced from an insulating material and surrounds the post insulator (2) in a flush manner.
5. Dry transformer (38) having an external earthed shielding (40), comprising a lead-through system (1) according to one of the preceding claims arranged in a terminal opening of the earthed shielding (40).
6. Dry transformer (38) according to Claim 5, in which the tap inner conductors (5) are connected to a turn in the region of the turn of the dry transformer (38) that is associated with the terminal inner conductor (4).
7. Dry transformer (38) according to Claim 5 or 6, in which tap inner conductors (5) and terminal inner conductors (4) have a relative potential difference of less than 10%.
8. Dry transformer (38) according to one of Claims 5 to 7, designed for a rated voltage of more than 1 kV and/or a rated power of more than 50 kVA.
9. Dry transformer (38) according to one of Claims 5 to 8, which is designed as a cast-resin transformer.

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