EP2577685B1 - Composite insulator - Google Patents

Description

The invention relates to a composite insulator according to the preamble of claim 1. Such a composite insulator comprises a core or trunk for load absorption, which is made in particular from a fiber-reinforced thermoset such as an epoxy resin or a vinyl ester. To provide the desired insulating properties and to protect against external, in particular weather-related influences, the core is surrounded by a protective layer, which is made in particular from an electrically insulating elastomer such as a silicone rubber.

In general, avoiding partial discharges is a must when isolating high-voltage electrical equipment. Such, e.g. Discharges resulting from local field increases lead to damage in the protective layer, in particular in the case of composite insulators, as a result of which the service life is reduced. In the case of composite insulators, measures to avoid local field increases are of great importance. As a suitable measure for high-voltage insulators, shielding electrodes are known, for example, which are attached to the live fittings and help there to avoid excessive fields at the ends of the fittings.

A major problem with high-voltage insulators is the extreme uneven distribution of the voltage curve along their length. The reason for this is the stray capacitance of the isolator to earth. Another problem is local discharges on dirty insulators, which are caused, for example, by excessive fields during local drying.

From the WO 2009/100904 A1 To avoid local field elevations, it is known to provide a composite insulator with a field control layer at least in sections, which comprises field-influencing particles. Such particles act, for example, resistively, capacitively or are semiconducting, and contribute to reducing voltage jumps along the insulator by means of a nonlinear connection of a corresponding electrical variable with respect to the voltage. In particular, microvaristors made of ZnO are mentioned which show an abrupt reduction in electrical resistance above a threshold voltage.

From the GB 1 334 164 A a ceramic high-voltage insulator can be seen, which has shields as an arc barrier. Trunk sections of the insulator lying between the individual screens are provided with a semi-conductive surface layer, in particular made of metal oxides. In addition, it is provided that the bottom and / or top of the first and the last screen are additionally provided with a semiconductive surface layer. This is intended to improve rollover behavior in the presence of moisture.

From the US 2004129449 A1 A high-voltage insulator can be seen, in which shields are applied to a core made of a fiber-reinforced material and consist of a silicone material with fillers of zinc oxide embedded therein.

From the DE 32 14 141 A1 To reduce a voltage gradient between an end shoe (fitting) and an insulator area, the arrangement of a so-called corona shield in the manner of a shielding electrode is provided, which has a semiconducting polymer.

In the GB 1 541 071 A To reduce mechanical stress, a conductive ring element is arranged on a lowermost screen, which is connected in an electrically conductive manner to an upper part of the fitting. An elastic element is arranged between the ring element and the partial area. In addition, an electrically conductive shield element in the manner of a shielding electrode can be arranged in the bottom shield.

The object of the invention is to provide a composite insulator of the type mentioned, which is further improved in terms of avoiding local discharges.

This object is achieved according to the invention by a composite insulator with the features of claim 1. The composite insulator has a protective layer which comprises, in sections, particles which influence the field of the insulator.

The invention is based on the consideration of placing the particles influencing the field along the insulator in a targeted manner on the insulator in such a way that discharges which occur during the service life under the external conditions to be expected and which can lead to destruction of the insulating protective layer are avoided as far as possible . For this purpose, investigations were carried out on long-rod composite insulators designed for a voltage of 420 kV. The long-rod composite insulators used had a creepage distance of 3.91 m in length with a number of 10 shields. The low number of shields was deliberately chosen in order to achieve a greater tendency of the insulators to breakdown in the test.

In a high-voltage laboratory, the isolators were artificially irrigated at an angle of 45 ° C in accordance with the IEC 60060-1 standard. The tests were carried out under AC voltage. The artificial rain had a conductivity of κ = +/- 100 µS / cm. The voltage applied was gradually increased. Resulting partial discharges were observed visually. As a result, at a voltage of 600 kV, for a conventionally manufactured long-bar composite insulator, the protective layer of which has no field-influencing particles, significant discharges were observed on the underside of the shields facing the high-voltage end of the insulator.

Based on this knowledge, the invention is based on the model concept that a sprinkling of the insulators forms a conductive coating on the top of the screens and along the shaft. As a result, arises over a conventional insulator, a high voltage drop across the dry underside of the shields. If the dielectric strength of the surrounding atmosphere is exceeded due to the resulting local field elevation, local discharges occur on the underside of the screens.

The invention provides that the field-influencing particles are provided in the area of the aforementioned dry zones of the isolator on the undersides of screens. For this purpose, the field-influencing particles are applied separately in sections, vulcanized, applied with the protective layer, injection molded, molded on or cast in. For this purpose, the field-influencing particles are expediently added to a suitable insulation material, in particular the material of the protective layer. This material is then cast on, glued or vulcanized onto the existing protective layer. The field-influencing particles can also be added to the protective layer in sections in the manufacture of the insulator. Alternatively, the material mixed with the field-influencing particles can also be encapsulated by the protective layer when the insulator is finally shaped.

The protective layer and also the material mixed with the field-influencing particles is preferably a silicone rubber, an ethylene-propylene copolymer (EPDM), an ethylene-vinyl acetate (EVA) or an epoxy resin. Accordingly, a section of silicone rubber, EPDM, EVA or epoxy resin mixed with field-influencing particles is applied.

Resistive or capacitive particles or semiconductor particles are preferably used as field-influencing particles. Microvaristors made of doped zinc oxide (ZnO) are particularly preferred. ZnO microvaristors show a non-linear current-voltage characteristic. Up to a threshold voltage, zinc oxide can be regarded as a high resistance and has an extremely flat current-voltage characteristic. Above the threshold voltage, the resistance drops abruptly, the current-voltage characteristic suddenly changes its slope.

If such field-influencing particles and in particular microvaristors, i.e. voltage-dependent resistors, are applied in sections to the insulator or with the protective layer, the conductivity, which is abruptly increased above the threshold voltage, reduces a local voltage or field increase, so that the undesirable local and destructive ones Discharges are prevented.

The composite insulator includes a number of shields from the protective layer to extend the creepage distance. The field-influencing particles are encompassed by the screens or arranged on the screens. When the composite insulator is in a standing position, the drying zones connected with high voltage jumps are on the underside of the screens. If the field-influencing particles are added to the protective layer of the screens or arranged on the screens, the discharges which occur there undesirably are avoided. This embodiment variant has shown that not all screens have to encompass the field-influencing particles. Only a partial number of the screens are therefore provided with the field-influencing particles. This depends on the voltage curve over the length of the composite insulator. As studies have shown, the highest voltage jumps on the shields, which are arranged at the live end, are obviously to be expected.

In a preferred embodiment, the part number of the screens provided with field-influencing particles is located at the live end. Accordingly, starting from the live end of the composite insulator, a number of the shields are initially provided with field-influencing particles. The subsequent screens are conventionally made without field-influencing particles.

Alternatively, starting from the live end of the composite insulator, a partial number of shields can be provided with field-influencing particles, then a partial number of shields can be manufactured conventionally and this arrangement can be repeated over the length of the composite insulator.

Furthermore, it has been shown that the screens as such do not have to be provided with the field-influencing particles as a whole. To reduce the voltage drop across the drying zone on the underside of the screens, it is sufficient to provide only the underside of the screens with field-influencing particles. This is sufficient to reduce the high voltage jumps between the ends of the shields and the core or the shaft of the insulator.

In a first embodiment variant in this regard, the field-influencing particles are vulcanized or glued on from a separate disk, in particular from the material of which, gluing, shrinking or vulcanizing, the separate disk is vulcanized or glued on. Alternatively, the separately manufactured disc containing the field-influencing particles can be cast into the screens during manufacture. Finally, it is also possible to encase the shields provided with the separate pane on the underside in a final manufacturing process from the protective layer, in particular by encapsulation or encapsulation.

According to another embodiment of the invention which can also be combined, the protective layer as such with particles which influence the field is preferably applied to the underside of the screens provided. For this purpose, the material of the protective layer is mixed with the field-influencing particles. Then the offset material is molded, cast or vulcanized onto the underside of the screens.

In a further preferred embodiment, the shields of the composite insulator are offset on the underside with ribs, which lead to a further extension of the creepage distance. The separate disk or the protective layer mixed with the field-influencing particles is preferably arranged on these ribs as described above. Due to the increased surface area due to the ribs, an improved connection between the shields and the separate pane or the subsequently applied protective layer mixed with field-influencing particles is achieved.

It has also been shown that, in particular in combination with shields provided with field-influencing particles on the underside, a further improvement of the composite insulator with regard to avoiding local discharges is achieved if the protective layer is provided with the field-influencing particles at least in sections along the core. In particular, the core is provided for a partial section in the vicinity of the live end of the composite insulator with the protective layer which comprises the field-influencing particles.

In a further preferred embodiment of the composite insulator, the shields and / or the core are surrounded by an outer protective layer which is free of field-influencing particles. Through such an outer protective layer, reference can be made, if necessary, to the specific external weather conditions to which the composite insulator is exposed during its use by means of a separate choice of material.

Fig. 1:

einen Langstab-Verbundisolator gemäß einer ersten Ausführungsvariante,

Fig. 2:

einen Langstab-Verbundisolator gemäß einer zweiten Ausführungsvariante,

Fig. 3:

einen Ausschnitt eines Langstab-Verbundisolators, wobei die Schirme auf der Unterseite mit einer feldbeeinflussende Partikel enthaltenden Scheibe versehen sind,

Fig. 4:

einen Ausschnitt aus einem Langstab-Verbundisolator, wobei die Schirme auf der Unterseite mit einer Schutzschicht versehen sind, die feldbeeinflussende Partikel umfasst,

Fig. 5:

einen Ausschnitt aus einem Langstab-Verbundisolator, dessen Kern gegenüber dem Verbundisolator nach Figur 4 zusätzlich mit einer Schutzschicht versehen ist, die feldbeeinflussende Partikel umfasst, und

Fig. 6:

einen Langstab-Verbundisolator gemäß Figur 5, wobei die Schirme einschließlich der mit feldbeeinflussenden Partikeln versetzten Schutzschicht von einer äußeren Schutzschicht umhüllt sind.

Embodiments of the invention are explained in more detail with reference to a drawing. Show:

Fig. 1:

a long-rod composite insulator according to a first embodiment,

Fig. 2:

a long-rod composite insulator according to a second embodiment,

Fig. 3:

a section of a long-rod composite insulator, the shields being provided on the underside with a pane containing field-influencing particles,

Fig. 4:

a section of a long-rod composite insulator, the shields being provided on the underside with a protective layer which comprises field-influencing particles,

Fig. 5:

a section of a long-rod composite insulator, the core of which compared to the composite insulator Figure 4 is additionally provided with a protective layer comprising field-influencing particles, and

Fig. 6:

a long rod composite insulator according to Figure 5 , wherein the screens, including the protective layer mixed with field-influencing particles, are encased by an outer protective layer.

In Figure 1 A long-bar composite insulator 1 is shown, which comprises a core 2 made of a glass fiber reinforced plastic, on which ten screens 4 are arranged to extend the creepage distance over the length. The connection fittings 5, 6 are attached to the ends of the core 2. The connection fitting 6 is provided for contacting a high voltage HV, and in this respect has the live end of the insulator 1.

The long-rod composite insulator 1 shown with a total of ten shields 4 is designed to isolate a voltage of approximately 400 kV. The core 2 is completely covered with a protective layer 8 made of a silicone rubber. The shields 4 are attached to this shell of the core 2. The screens 4 are also made of silicone rubber.

To avoid local discharges caused by excessive fields or large voltage jumps, the protective layer 8 of the core 2 is covered over the whole Length of the composite insulator 1 mixed with field-influencing particles 7. The field-influencing particles 7 are microvaristors made of doped ZnO. Furthermore, five of the total of ten shields 4 are made of silicone rubber mixed with field-influencing particles 7 at the live end of the composite insulator 1, ie following the armature 6.

In a sprinkling test, a long-rod composite insulator 1 shows accordingly Figure 1 compared to a conventional long-rod composite insulator without field-influencing particles, there is a significantly reduced tendency to discharge on the underside of the screens 4. This is due to the fact that the microvaristors made of ZnO become conductive at high voltages, so that the voltage jumps from the wetted upper side of the screens 4 to the section of the core 2 lying underneath are significantly reduced.

In Figure 2 is basically a under construction Figure 1 Similar long-rod composite insulator 1 shown. This differs in that the protective layer 8 along the core 2 is now not provided with field-influencing particles 7. Rather, only the five screens 4 adjacent to the live end of the composite insulator 1 are made from a protective layer 8 which is mixed with field-influencing particles.

This composite insulator 1 according to Figure 2 shows in a sprinkling test a significantly reduced tendency to roll over on the underside of the screens 4 compared to a conventional long-rod composite insulator without field-influencing particles 7.

In Figure 3 is a partial section of a long-bar composite insulator 1 according to the Figures 1 or 2 shown. Two screens 4 are shown in the vicinity of the live end, that is, in the vicinity of the armature 6.

The long-rod composite insulator 1 accordingly Figure 3 comprises the core 2 made of a glass fiber reinforced plastic. A protective layer 8 is on the core 2 made of silicone rubber. The shields 4 are mounted on this protective layer 8.

On the underside of the screens 4, a separate disk 10 made of prefabricated EPM, which contains field-influencing particles 7, is attached for influencing the field or for reducing high voltage jumps.

According to a first embodiment variant, the separate pane 10 is vulcanized on the underside in accordance with the upper screen 4. According to a second embodiment variant, the separate disk 10 containing the field-influencing particles is cast into the material of the screen 4, as can be seen on the lower screen 4.

According to Figure 4 The shields 4 of another variant of the long-rod composite insulator 1 comprise a number of circumferential ribs 12 on the underside. These ribs 12 are cast with a protective layer 8 ′ which contains the field-influencing particles 7. According to Figure 5 the long-rod composite insulator 1 has, at least in sections, a further surrounding protective layer 8 'on the core 2, which in turn is mixed with field-influencing particles.

According to Figure 6 the protective layer 8 ′ attached to the underside of the screens 4 is poured into the screens 4 with field-influencing particles. According to a final manufacturing step, the in Figure 6 Long rod composite insulator 1 shown is encased with an outer protective layer 13 made of silicone rubber, which does not comprise any field-influencing particles 7.

reference numeral

1

Composite insulator

2

core

4

umbrella

5

Connection fitting

6

Connection fitting

7

Particle influencing field

8th

Protective layer

8th'

Protective layer with field-influencing particles

10

disc

12th

Ribs

13

outer protective layer

HV

High voltage end

Claims (8)

1. Composite insulator (1) with a core (2), in particular of a fibre-reinforced thermoset, and with a protective layer (8, 8'), in particular of an insulating elastomer, surrounding this core (2), wherein the protective layer (8, 8') comprises in certain portions particles (7) influencing the field of the insulator (1) and wherein the protective layer (8, 8') has a number of sheds (4) to extend the creepage distance,
   characterized
   in that a partial number of sheds (4), i.e., a plurality of sheds (4) but not all sheds (4), comprise the protective layer (8, 8') with the field-influencing particles (7), in that the protective layer (8, 8') comprises the field-influencing particles (7) on the underside of this partial number of sheds (4) and in that the upper side of this partial number of sheds (4) is free from field-influencing particles (7).
2. Composite insulator (1) according to Claim 1,
   characterized
   in that the partial number of sheds (4) are located at the voltage-carrying end (HV).
3. Composite insulator (1) according to Claim 1 or 2,
   characterized
   in that a disk (10) containing the field-influencing particles (7) is vulcanized on or moulded in on the underside of at least a partial number of the sheds (4) .
4. Composite insulator (1) according to any one of the preceding claims,
   characterized
   in that the protective layer (8, 8') is mixed with the field-influencing particles (7) at least in certain portions along the core (2).
5. Composite insulator (1) according to any one of the preceding claims,
   characterized
   in that the sheds (4) and/or the core (2) are surrounded by an outer protective layer (13) that is free from field-influencing particles (7).
6. Composite insulator (1) according to any one of the preceding claims,
   characterized
   in that the protective layer (8, 8') is a silicone rubber, an ethylene-propylene copolymer (EPDM), an ethylene-vinyl acetate (EVA) or an epoxy resin, wherein a silicone rubber, EPDM, EVA or epoxy resin mixed with field-influencing particles (7) is applied in certain portions.
7. Composite insulator (1) according to any one of the preceding claims,
   characterized
   in that the field-influencing particles (7) are applied, vulcanized on, applied with the protective layer (8, 8') or moulded in on the undersides of sheds (4) .
8. Composite insulator (1) according to one of the preceding claims,
   characterized
   in that the field-influencing particles (7) are resistive or capacitive particles or semiconductor particles, in particular microvaristors of doped ZnO.

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