EP2243145B1 - Field-controlled composite insulator - Google Patents

Description

The invention relates to a field-controlled composite insulator comprising a rod or tube as insulator core made of fiber-reinforced plastic, which is coated with a screen cover and equipped at its ends with fittings.

The materials of an insulator are heavily loaded by the inhomogeneous distribution of the electric field across its surface. One of the causes lies in the structural design of an insulator. In particular, in the field of fittings, the field strength changes due to the transition from the insulating materials of the screens and the insulator core to a metallic material, because of the transition to ground potential at the mast crossbar or conductor potential, where the conductors are attached. To prevent the resulting local field disturbance, in particular field strength peaks, the so-called geometric field control can be used. By rounding corners and edges, the geometry of the workpieces, in particular the parts carrying the tension, is defused.

Another cause is the dirt deposits, a burden that affects an insulator overall. On composite insulators, which are exposed as outdoor installations of the weather, deposited over time thin dirt layers. Due to the electrical conductivity of these layers, charge currents can flow on the insulator surfaces. If these layers become moist, for example due to rain or dew, the conductivity is increased even further, which leads to increased current strengths of the leakage and discharge currents and to ohmic losses. This causes a heating of the dirt layers with the result of their drying. The drying dirt layers become locally high-impedance, so that high voltage drops can occur here. If this causes the electrical dielectric strength of the ambient air to be exceeded, glow discharges or electrical flashover discharges occur, which are the cause of aging and finally destruction of the material of the insulator surface.

As measures to equalize the electric field and to avoid local field disturbance, in particular field strength peaks, local coatings or coatings of insulating materials, such as plastics such as epoxy resins and polymers are applied with deposits of dielectric and / or ferroelectric materials as field control layers.

Of an embodiment of the high-voltage composite insulator according to the DE 32 14 141 A1 (local Fig. 2 ) it is known that a plurality of screens with a collar pushed over the core and a contact sleeve between the last screen and the metal fitting are semiconductive. In this embodiment of the insulator, there is the danger that metal particles and airborne dirt particles accumulate directly on the electrically semiconductive layer and from there - due to electrical interactions - can be easily washed away by the natural weathering. These particles can lead to local field strength increases and thus to damage the insulator with appropriate geometry.

From the DE 197 00 387 B4 a composite insulator is known whose screen element and optionally the core are each made of a semiconducting material. The semiconductor capability of the shield shell and the core are the same size at each point of the insulator. Against weathering and pollution, the screen cover must be additionally coated with a protective layer.

Next will be in the EP 1 577 904 A1 proposed a composite insulator, wherein between the core and protective layer at least in a section a field control layer is arranged, which contains the electrical field of the insulator influencing particles as a filler. Such a composite insulator is also from the DE 15 15 467 A1 known.

It is the object of the present invention to present a composite insulator in which the causes for the formation of local field disturbances, in particular field strength peaks and corona discharges, are largely eliminated by a field control layer tuned to the respective disturbance.

The object is achieved constructively with the help of the characterizing features of the insulator according to the invention according to claim 1 and by means of a method according to claim 15 for its production. Advantageous embodiments of the Insulator and the method for its preparation are claimed in the dependent claims.

The field control layer of the composite insulator according to the invention accordingly comprises a layer in which the proportion of the particles influencing the electric field is different over the length of the layer.

The galvanic contact between the field control layer and the fitting can be produced for example by conductive ink, metal rings or wire mesh. Outside the valve, the field control layer is surrounded by a protective layer or directly by the screens extruded seamlessly on the core. The insulator core as a pipe or rod is usually made of a fiberglass-reinforced thermoset such as epoxy or polyester resin.

The invention is suitable for all types of composite insulators, in particular for suspension insulators, post insulators or bushing insulators. The field of application starts at high voltages above 1 kV and is particularly effective at voltages above 72.5 kV.

The field control layer is usually made of the same material as the protective layer covering it. The protective layer can also be advantageous from a higher erosionsund Kriechstromfesten material. The protective layer is in any case made of a material with high insulation properties. Materials with these properties are elastomeric materials, for example, polymeric plastics such as silicone rubber (HTV) of hardness classes Shore A 60 to 90 or ethylene-propylene copolymer (EPM). On the thus prepared core with field control layer and protective layer, the screens are pushed, which may consist of the same material as the protective layer. The protective layer and the screens can also be extruded in one and the same operation of the same material on the core, as it is known from the patent EP 1147525 B1 is known.

The field control can be resistive or capacitive or in combination with each other. For this purpose, the material of the field control layer is filled with particles as filler, which cause the field control.

For resistive field control, also called ohmic field control, a field control layer with ohmic conductive (conductive) and / or semiconducting (semiconductive) fillers is provided. In the ohmic conductive fillers, the linear material dependence between voltage and current is utilized. The conductive fillers include, for example, carbon black, Fe 3 O 4 and other metal oxides.

There are semiconducting materials with a non-linear dependence between voltage and current. These properties have varistors, for example ZnO, which become conductive above a defined voltage or field strength and thus have the ability to limit overvoltages. Microvaristors are particularly suitable for resistive field control. These are varistors in powder form with grain diameters between 50 nm and 100 μm. With a suitable design, it can be achieved that a material filled with microvaristors, in particular a silicone material, exhibits high electrical conductivity and low power dissipation in continuous operation under surge stress.

Capacitive field control uses materials with dielectric properties such as TiO2, BaTi03 or TiOx. These materials have a high dielectric constant (permittivity).

Refractive field control is a special form of capacitive field control. By suitable arrangement of materials with different dielectric constants, the field lines at the transitions of the materials are so broken that local field disturbances, in particular field strength peaks, are eliminated as far as possible. The field control layer may consist of one layer or multiple layers, wherein the individual layers may have different field control properties.

The particles added as fillers to the layers of the field control layer have a diameter of 10 nm to 100 μm, preferably in a range of 0.1 μm to 10 μm. Their size depends on the thickness of the layer and the intensity and extent of the expected field disturbance.

The proportion of particles is between 50 and 90% by weight, preferably 70%.

The proportion of particles, the degree of filling, may be above the percolation limit, i. that the particles are in direct electrical contact.

The thickness of a layer of a field control layer may be 1 mm to 5 mm, usually 2 mm to 3 mm. It depends on the intensity and extent of the expected field disturbance.

The field control layer can consist of one layer and contain only resistive particles as filler. Such a layer is provided at the locations of the insulator to which preferably a resistive, an ohmic field control is required.

The field control layer can consist of one layer and contain only capacitive particles as filler. Such a layer is provided at the locations of the insulator to which preferably a capacitive, or in particular a refractive, field control is required.

The field control layer may consist of one layer and the proportion of the resistive or capacitive particles may be different over the length of the layer. With the same thickness, the intensity of the effect on the field disturbances can be changed locally by changing the proportion of fillers in the position. The change in the proportion of the filler is possible if the filler has not already been added to the material of the layer before application, but only in or before the nozzle for applying the layer is mixed with the material.

The thickness of a layer of a field control layer can change over its length. This is possible by changing the feed rate within the extruder, which applies the layer to the core.

The field control layer can also consist of at least two layers with resistive or capacitive particles as fillers. The one layer may have a higher proportion of resistive or capacitive particles than the other layer.

The field control layer may also consist of at least two layers, one layer containing exclusively resistive and another layer exclusively capacitive particles. For several layers one above the other, the layers may alternate in their order.

The field control layer may consist of one layer and contain a mixture of resistive and capacitive particles.

The field control layer can also consist of at least two layers, one layer containing a mixture of resistive and capacitive particles and the other layer containing only resistive or capacitive particles.

In the case of several layers one above the other, the layers may alternate in their order or composition in terms of their effect on the electric field. In addition, the proportion of capacitive and / or resistive particles in the individual layers of the layer may be different.

The field control layer can be applied over the entire length of the insulator core. However, it can also extend only over partial areas, such as in the field of fittings. The field control layer can also be divided into individual sections and thereby interrupted.

In the case where the field control layer is divided into individual sections and consists of at least two layers, one layer may be longer than the other bordering the layerless section and extending beyond the layer above or below to the layerless section, so that the field influencing character of this situation comes exclusively to effect.

By the above-described discontinuous arrangements of the layer high power losses can be avoided.

Optionally, the individual layers of a field control layer can be separated from one another by insulating intermediate layers if differences in the conductivity in the contact region of the two layers themselves could lead to undesired changes in the field.

The above-mentioned possible combinations of the number of layers, the arrangement of the individual layers within a layer and the degree of filling with capacitive and / or resistive particles makes it possible to occur at the possible locations where a harmonic inhomogeneity of the electric field can occur. to prevent or suppress them by means of a coordinated layer.

For resistive field control, microvaristors are preferred, in particular ZnO.

To protect the field control layer, it can be coated with a protective layer, for example an insulating HTV silicone extrudate layer with extremely good tracking, erosion and weathering resistance, onto which the screens are then pushed. This protective layer increases the outdoor resistance and can be up to 5 mm thick, advantageously between 2 mm and 3 mm.

On the core with the field control layer but also the umbrellas can be extruded directly without gaps, as it is known from the patent EP 1147525 B1 is known. Protective layer and umbrellas then consist of the same material.

The field control layer can be applied to the core by an extruder through which the core is pushed. If a layer with several layers is to be applied to the core, this can be done by a multi-stage nozzle or by several extruders arranged one behind the other. The application of the layers must be such that they adhere well to the insulator core and join together to form a layer. If necessary, the application of Haftverrnittiern required.

The invention offers the possibility of using a field control layer only at those points where critical disturbances of the electric field, in particular field strength peaks, can occur. As a result, the power losses at the insulators can be reduced to minimum values.

The composition of the field control layer of layers with resistive and / or capacitive particles or the structure of the layer of two or more layers, in particular with different particles and / or particle proportions, as well as the variation of the overlap lengths of the layers can advantageously on the field disturbances to be eliminated, in particular field strength peaks , especially caused by local pollution. The field distribution along the insulator is thereby made uniform. This avoids the formation of corona discharges, corona discharges and flashovers, which prevents premature aging of the material.

Fig. 1

einen Ausschnitt aus einem Verbundisolator mit einer Feldsteuerschicht, aus einer Lage bestehend, im Längsschnitt,

Fig. 2

einen Ausschnitt aus einem Verbundisolator mit einer Feldsteuerschicht aus zwei Lagen, wobei eine Lage nur einen Teil des Kerns überdeckt,

Fig. 3

einen Langstabisolator, bei dem die Bereiche gekennzeichnet sind, in denen eine Feldsteuerschicht aufgetragen ist,

Fig. 4

einen Langstabisolator, bei dem eine Feldsteuerschicht im Bereich der Armatur aufgetragen ist, an der die Leiterseile befestigt sind, Fig. 5 den Übergangsbereich von einem Isolatorkern zu einer Armatur im Längsschnitt,

Fig. 6

einen Vergleichstest zwischen einem Isolator mit Feldsteuerschicht und einem herkömmlichen Isolator bei anliegender Wechselspannung unter Beregnung und

Fig. 7

ein Ablaufdiagramm zur Erläuterung der Herstellung eines Isolators.

By way of examples, the invention will be explained in more detail. Show it:

Fig. 1

a section of a composite insulator with a field control layer, consisting of a layer, in longitudinal section,

Fig. 2

a section of a composite insulator with a field control layer of two layers, wherein a layer covers only a part of the core,

Fig. 3

a long-rod insulator, in which the areas are marked in which a field control layer is applied,

Fig. 4

a long-rod insulator in which a field control layer is applied in the region of the armature to which the conductor cables are attached, Fig. 5 the transition region from an insulator core to a valve in longitudinal section,

Fig. 6

a comparison test between an insulator with field control layer and a conventional insulator with applied AC voltage under irrigation and

Fig. 7

a flowchart for explaining the production of an insulator.

In FIG. 1 a longitudinal section through a composite insulator 1 is shown. In the present case, it is the section of a long-rod insulator. On a core 2 made of glass fiber reinforced plastic, a field control layer 3 is applied. In coordination with the occurring field disturbances, it can have capacitive or resistive properties. For example, it may contain ZnO microvaristors for resistive field control. The field control layer 3 is covered by a protective layer 4, which consists of an erosion and Kriechstromfesten material and the field control layer 3 protects against weathering and pollution. On this protective layer 4, the screens 5 are arranged at regular intervals, which are injected from one of the known polymeric plastics.

In FIG. 2 also a longitudinal section through a composite insulator 1 is shown. With the FIG. 1 Matching features are designated by the same reference numerals. In the present example, the field control layer 3 in a partial region of the insulator 1 consists of two layers 31 and 32, of which the layer 32 is arranged above the continuous layer 31. The two layers 31 and 32 may have different field control properties. So can the outer Layer 32 capacitive and the continuous layer 31 have resistive properties. Such an arrangement of the layers may be advantageous, for example, in the field of fittings in terms of constructive field disturbances. In the present example, the field control layer 3 is uniformly thick throughout. In the area where the field control layer 3 is double-layered, by reducing the extrusion, the inner layer 31 can be thinned. Thus, in a second step, the outer layer 32 can be applied so thick that a uniform, uniform layer thickness is achieved.

The FIGS. 3 and 4 show long-rod insulators 10, as used for example in high-voltage overhead lines. The structure of the field control layers of these insulators may for example correspond to the structure as in the in the FIGS. 1 or 2 is described insulators described. The insulators 10 each depend on a traverse 11 of a high-voltage mast, not shown here. The attachment takes place in a known manner with a fitting 12 made of metal. At the lower end, the conductor cables 14 are fastened by means of a further armature 13. In the present examples, the isolators 10, which are 4 meters in length, are only partially cut-off, as in FIG FIG. 3 represented, or only in a certain area on a fitting, as in FIG. 4 shown coated with a field control layer. The insulator 10 in FIG. 3 each has five equal areas 15 in which the core is covered with a field control layer. They are each interrupted by areas of equal size without field control layer. The insulator 10 in FIG. 4 has a portion 16 which is covered with a field control layer and which extends from the armature 13, to which the conductors 14 are attached, upwards over one third of the rod length.

FIG. 5 shows a schematic representation of a transition region from a fitting to the shield shell area in longitudinal section. It is a section through the end of an insulator with a fitting to which the conductors are attached, as in the Figures 3 or 4 is shown. Matching features with the Figures 2 . 3 and 4 are designated by the same reference numerals.

In the insulator 1 or 10, the core consists of a rod 2 made of glass fiber reinforced plastic, which is coated with a field control layer 3, the in turn is enveloped by a protective layer 4. On this protective layer, the umbrellas 5 are raised. The field control layer 3 corresponds in structure to that as shown in FIG FIG. 2 is shown. The end of the rod 2 is enclosed by the fitting 13. A layer 31 completely covers the core 2 of the insulator on the length visible in the illustration. It is a layer with resistive effect and contains microvaristors. On the outside there is a layer 32 with capacitive effect containing fillers with dielectric properties. The layer 32 extends from the interior of the fitting 13 to above the first screen 5. The capacitive field control is particularly suitable to reduce field strength peaks that are constructive, for example, by edges or stepped transitions, as they occur at the transition from a fitting to the insulator. To improve the conductive contact between the layers and the fitting of the core enclosing cavity of the fitting may be coated with a conductive paint. Also deposits of wire loops or wire nets are, as not shown, possible.

FIG. 6 shows the result of a comparison test between a long-rod insulator whose surface corresponds to a field control layer FIG. 1 coated and a conventional long-rod insulator as reference insulator, which was equipped exclusively with HTV silicone without field control layer. The umbrellas were each made of HTV silicone. The striking distance was 2765 mm. For both specimens, a 3 mm thick polymer layer (cross-sectional area: 1.8 cm 2) was applied to a GRP rod with a diameter of 16 mm. In one of the specimens, the polymer layer for field control were microvaristors, ZnO varistors in powder form, in a proportion of 50 to 90% by weight, preferably 70% by weight with a particle size of 10 nm to 100 μm, preferably between 0, 1 [mu] m and 10 [mu] m have been added. In the present example, the filling level of the microvaristors was above the percolation limit, ie the microvaristors were in direct electrical contact with each other.

In FIG. 6 On the left are the isolator with field control layer and on the right the reference insulator during the comparison test. With an applied AC voltage of 750 kV (effective), the insulators were irrigated. While the reference insulator under the bottom five, the conductor side facing screens shows strong discharge activities, the equipped with the field control layer insulator is completely discharge-free.

In FIG. 7 Fig. 3 is a flow chart for explaining the manufacture of an insulator. The core 2 of the insulator to be produced is a rod which consists of a glass fiber reinforced plastic. This rod 2 is guided in the feed direction 20 by successively arranged stations, where it is completed to the insulator. In the first station 21, a bonding agent 211 is applied so that the layers of the field control layer 3 to be subsequently applied are intimately joined to the core 2. In the extruder 22, a first layer 31 of the field control layer is applied, for example a layer with varistors, a layer with resistive character. If another layer is to follow, another extruder 23 is provided for applying the further layer 32, for example a layer with a capacitive character. Instead of two extruders arranged one behind the other, it is also possible to use a two-nozzle extruder which extrudes both layers one above the other onto the rod. The next extruder 24 applies the protective layer 4.

Depending on the manufacturing process of the screen cover, the insulator core can now be separated with a separating tool 25. In the next step 26, the screens can be extruded or the already prefabricated umbrellas 5 are postponed. A thermal treatment 27 for curing the field control layer, the protective layer and the screens concludes the manufacture of the insulator 1; 10 off. After preparing the ends of the rod, the fittings can be attached to it.

If the protective layer and the screen cover are applied in one and the same operation as a common layer on the insulator core 2, the production takes place in the station 26, according to the patent EP 1147525 B1 , A separation into individual, finished insulators 1; 10 takes place here only after the thermal treatment 27 with a cutting tool 28th

Claims (19)

1. Composite insulator (1, 10) containing a core (2) and a protective layer (4) which surrounds the core (2), wherein a field control layer (3) which contains particles, as a filler, which influence the electrical field of the insulator, is arranged between the core (2) and the protective layer (4) in at least one section (15, 16) of the insulator (1, 10),
   characterized in that
   the field control layer (3) has a stratum (31, 32) wherein the proportion of the particles which influence the electrical field differs over the length of the stratum (31, 32).
2. Composite insulator (1, 10) according to Claim 1,
   characterized in that
   the field control layer (3) consists of one, two or more strata (31, 32), and in that the individual strata (31, 32) have different field control characteristics.
3. Composite insulator (1, 10) according to Claim 1 or 2,
   characterized in that
   the field control layer (3) consists of one stratum (31, 32) and contains exclusively resistive or capacitive particles as a filler.
4. Composite insulator (1, 10) according to one of Claims 1 or 2,
   characterized in that
   the field control layer (3) consists of at least two strata (31, 32), and in that one of the strata (31, 32) has a higher proportion of resistive or capacitive particles than the other.
5. Composite insulator (1, 10) according to one of Claims 1 or 2,
   characterized in that
   the field control layer (3) consists of at least two strata (31, 32), and in that one of the strata (31) contains exclusively resistive particles, and the other stratum (32) contains exclusively capacitive particles.
6. Composite insulator (1, 10) according to one of Claims 1 or 2,
   characterized in that
   the field control layer (3) consists of one stratum (31, 32) and contains a mixture of resistive and capacitive particles.
7. Composite insulator (1, 10) according to one of Claims 1 or 2,
   characterized in that
   the field control layer (3) consists of at least two strata (31, 32), and in that one stratum (31, 32) contains a mixture of resistive or capacitive particles, and the other stratum (31, 32) contains exclusively resistive or capacitive particles.
8. Composite insulator (1, 10) according to one of Claims 1 or 7,
   characterized in that
   the strata (31, 32) in a field control layer (3) when there are a plurality of strata (31, 32) one on top of the other alternate with respect to their effect on the electrical field, in their sequence and/or composition.
9. Composite insulator (1, 10) according to Claim 8,
   characterized in that
   the proportion of the capacitive and/or resistive particles in the individual strata (31, 32) of the layer (3) is different.
10. Composite insulator (1, 10) according to one of Claims 1 or 9,
    characterized in that
    the field control layer (3) is applied in individual sections (15) over the length of the core (2) of the insulator (10).
11. Composite insulator (1, 10) according to Claim 10,
    characterized in that,
    in the case of a field control layer (3) which is subdivided into individual sections and consists of at least two strata (31, 32), one stratum (31, 32) in the boundary area to the layer-free section is longer than the other and extends beyond the stratum (31, 32) located above or below it, to the layer-free section.
12. Composite insulator (1, 10) according to one of Claims 1 or 11,
    characterized in that
    the individual strata (31, 32) of the field control layer (3) are separated from one another by a stratum composed of an insulating material.
13. Composite insulator (1, 10) according to one of Claims 1 to 12,
    characterized in that
    the proportion of the particles in a layer is between 50 and 90 per cent by weight, preferably 70 per cent by weight.
14. Composite insulator (1, 10) according to Claim 13,
    characterized in that
    the proportion of the particles, the filling level, is above the percolation limit.
15. Method for producing a composite insulator (1, 10) containing a core (2) and a protective layer (4) which surrounds the core (2), according to one of Claims 1 to 14,
    characterized in that
    a field control layer (3) comprising at least one stratum (31, 32) of an elastomer material having a proportion of particles, which influence the electrical field of the insulator (1, 10), which proportion changes over the length of the layer, is applied to the core (2) of the insulator (1, 10) in at least one section (15, 16), and in that the entire core (2) is coated with the applied field control layer (3) with the protective layer (4), and in that the insulator (1, 10) is then subjected to heat treatment (27) in order to vulcanize the plastics.
16. Method according to Claim 15,
    characterized in that
    the field control layer (3) is applied in at least two strata (31, 32) with different effects on the electrical field.
17. Method according to Claim 15 or 16,
    characterized in that
    the field control layer (3) is applied in sections (15) to the core (2) of the insulator.
18. Method according to Claim 17,
    characterized in that,
    in the case of a field control layer (3) which is subdivided into individual sections and consists of at least two strata (31, 32), one stratum (31, 32) is applied in the boundary area to the layer-free section, beyond the stratum (31, 32) which is located above or below it, to the layer-free section.
19. Method according to one of Claims 15 to 18,
    characterized in that
    the particles which influence the electrical field of the insulator (1, 10) are added to the extrudate in a different amount, during the application of the stratum (31, 32) of the field control layer (3) to the core (2).

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