CN102254648A - Electrical insulation and production of insulation products - Google Patents

Abstract

The invention relates to a method (100) for manufacturing electrical insulators for medium or high voltage equipment. The method (100) comprises the steps of: pushing all liquid components of the insulating material of the electrical insulator through a static mixer (101); adding at least one filler to the component (102); pushing the component with the at least one The filler is passed through a conduit comprising a rapidly turning screw mixing device to mix the components with the at least one filler into a final mixture of the insulating material (103); the final mixture is directed to a mold such as a hot press, or for vacuum casting a mold located in a vacuum chamber, the inlet of which is connected to the outlet of the mixing device, which is fluidly connected to the mold (104a, 104b); an electrical insulator (105) is formed by at least partially curing the final mixture; and molding the electrical insulator (106). This curing can be part of molding.

Description

Production of electrical insulation and insulation products

technical field

The present invention relates to electrical insulation products in general and to high or medium voltage products in particular. This document focuses on the details of the manufacturing process of insulated products such as barrier insulators.

The invention is based on a method for producing an electrical insulator and an electrical insulator produced by this method according to the independent claims.

Background technique

In the electrical equipment industry, thermosetting insulating materials are used, for example, in the production of dry-type distribution transformers, medium voltage (MV) embedded poles and other insulation. The mixing of highly filled insulating materials takes considerable time, often higher than 1 hour. The standard process involves mixing resin with filler and hardener with filler in separate tanks equipped with impeller mixers to prevent premature reactions. After a good filler dispersion has been achieved in both components, they are simultaneously pushed through so-called static mixers and injected into the mould.

The molding principle is traditional vacuum casting or automatic pressure gelling (vacuum assisted process is also possible).

Several reliable mixing systems for producing such castable compounds are commercially available, eg from Hedrich Vacuum Systems and HuebersVerfahrenstechnik.

Contents of the invention

It is seen as an object of the present invention to provide an improved and efficient method for producing electrical insulators.

This object is achieved by speeding up the production process with different hybrid processes for processing insulating materials. Instead of using conventional systems comprising separate containers for resin and hardener equipped with impeller mixers, the inventive system is based on a fast rotating screw conveyor.

According to an embodiment of the invention there is provided a method for manufacturing an electrical insulator for medium or high voltage equipment, the method comprising the steps of: pushing all liquid components of the insulating material of the electrical insulator through a static mixer, adding at least one filler to the component, pushing the component and the at least one filler through a pipeline comprising a rapidly turning screw mixing device to mix the component and the at least one filler into a final mixture of insulating materials, passing the final mixture through an outlet of the mixing device Inducted (in flow connection to a mold) to a mold, an electrical insulator is formed by at least partially curing the final mixture, and the electrical insulator is molded.

According to another embodiment of the invention, there is provided a method for manufacturing an electrical insulator for medium or high voltage equipment, the method comprising the steps of: pushing all liquid components of the insulating material of the electrical insulator through a static mixer, adding at least one filler Give the component, push the component and the at least one filler through a pipeline comprising a fast-turning screw mixing device to mix the component and the at least one filler into a final mixture of insulating materials, direct the final mixture to a Mold for vacuum casting (the mold being located in a vacuum chamber, the inlet of which is connected to the outlet of a mixing device, which is flow-connected to the mould), for forming an electrical insulator by at least partially curing the final mixture, and for molding the electrical insulator .

The curing described above may be part of molding.

According to another exemplary embodiment, there is provided the method according to the above and below mentioned embodiments, wherein at least two fillers are added to the component, and wherein the mixing ratio of the fillers of the insulating material follows a Fuller sieve curve, which has a Fuller distribution:

$\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; ,</span>$

where d is the particle size of the filler, D is the largest particle size, eg 300 μm, P is the fraction of particles smaller than or equal to d, and n is the fractionation coefficient, possibly 0.37 or 0.5.

A Fuller sieve curve describes an optimized filler composite of a mixture, which provides optimized properties of the mixture, such as optimized strength and porosity or voids, etc. of the mixture.

By optimizing the composition of the two fillers according to the above-mentioned Fuller distribution, the compactness of the fabricated insulator can be optimized, providing an ideal relationship between filler and component/matrix.

Components may include hardeners and resins.

Instead of using a batch mixer, a continuous mixer with very high shear is used. High shear reduces mixing time considerably compared to conventional impeller mixers which typically mix dispersion of fillers in resin and hardener with low shear resulting in rather long procedures.

The insulating material may be a standard filled epoxy (eg, with one filler size), typically silica, with a filler content of about 65% by weight (corresponding to about 44% by volume). The insulating material may comprise polymer concrete.

According to another embodiment of the invention, at least two fillers can be used, wherein the filler content is between 70% and 96% by weight (corresponding to about 49% to 91% by volume), and typically between 83% and 85% by weight. % by weight (corresponding to approximately 60% to 70% by volume). Polymer concrete can be used for each of the fillers.

Mixing by applying higher shear forces The time required for dispersion of fillers in resin and hardener can be reduced to at least one tenth compared to prior art devices (e.g. impeller mixers, etc.) due to the significantly increased mixing efficiency . Fillers, resins and hardeners may be considered as components of the insulating material of electrical insulators.

According to an embodiment of the present invention there is provided a method for the manufacture of insulators for medium or high voltage equipment in which material is pushed through a pipe, such as a cylindrical pipe or the like, which has a rapidly turning helix inside which induces high shear forces, resulting in packing Good dispersion in the material matrix. The components pass through the mixing screw, which includes a membrane degassing unit, in less than one minute. The high shear generated by this system allows for higher filler content, which can be achieved by applying multiple fillers.

Furthermore, the inventive method contributes to the following advantages:

Significantly reduced mixing times and thus increased production throughput

Reduced risk of filler particle settling and better dispersion

Higher filler content and thus reduced cost (experimentally demonstrated up to 85% by weight of silica, higher solids content will be possible by using larger numbers of different fillers and larger maximum filler particle size of)

Lower material loss due to relatively low volume of confined mixing channels

Possibly less wear: the mixing screw is manufactured with a special wear-resistant alloy, so abrasive fillers such as alumina can be processed with it.

Further embodiments, advantages and applications of the invention will become apparent from the following detailed description and drawings from the claims or combinations of claims.

Description of drawings

The gist of the invention will be explained in more detail in the following text with reference to exemplary embodiments which are illustrated in the accompanying drawings, which are schematically shown in the following:

Figure 1 is an optical micrograph of the first sample of polymer concrete mixed with a conventional impeller mixer;

Figure 2 is an optical micrograph of a second sample of polymer concrete mixed with a conventional impeller mixer;

Figure 3 is an overview (scanning electron micrograph) of an optical micrograph of a sample of an inventive polymer concrete mixed with a continuous screw mixer according to an exemplary embodiment of the present invention;

Figure 4 is a close-up view IV of the scanning electron micrograph shown in Figure 3, according to an exemplary embodiment of the present invention;

Figure 5 is a schematic representation of Fuller sieve curves for examples with different packings;

6A is a flowchart of a method for manufacturing an electrical insulator for medium or high voltage equipment, according to an exemplary embodiment of the present invention; and

Fig. 6B is a flowchart of a method for manufacturing an electrical insulator for medium or high voltage equipment, according to another exemplary embodiment of the present invention.

Detailed ways

The difference in the technical effect of the present invention will become clear when comparing the photomicrographs of polymer concrete produced by the method according to the invention with those produced by conventional production methods using impeller-type mixing devices .

When looking at Figure 1, which shows an optical micrograph of a first sample of polymer concrete mixed with a conventional impeller mixer, essentially three discernible regions can be identified. Reference numeral 1 denotes large silica filler particles with a typical mean diameter of 0.3mm, while 2 denotes voids and 3 denotes areas of small silica filler particles and epoxy matrix with a typical mean diameter of 0.016mm. In particular, the particles 1 and the voids 2 are of considerable size.

If the insulating material is subjected to high electric fields, a large void size may lead to partial discharges, which may cause degradation of the material during the lifetime of the insulating product.

Most commonly, insulation formulations consist of epoxy resins, hardeners, catalysts, fillers and other liquid or solid additives. A typical filler content might be 65% by weight.

Likewise, the case in Figure 2 shows an optical micrograph of a second sample of polymer concrete produced by mixing these components by conventional production methods using impeller-type mixing devices. The difference between the second sample and the first sample shown in Figure 1 is that the void content can be greatly reduced by applying a combination of vacuum degassing and vibration. Again, essentially three distinguishable regions can be identified.

Reference 4 indicates a resin-rich region with very low filler content, while 5 indicates large filler particles (comparable to reference 1 in Figure 1 ) and 6 indicates a region with small silica filler particles and epoxy matrix (comparable to that in The number 3 in Fig. 1 corresponds to). In particular, particles 4 and 5 are of considerable size. Again, heterogeneous composites may undergo long-term degradation if subjected to high electric fields.

A scanning electron micrograph of a first sample of a polymer concrete mixed according to the invention with the inventive production method is shown in FIG. 3 . Although the scale bar of this photomicrograph is 500 μm (micrometer), relatively large silica particles 1 (comparable to number 1 in FIG. 1 ) are easily identified. Reference numeral 3 indicates a region with small silica filler particles and epoxy matrix (comparable to reference numeral 3 in FIG. 1 ). Furthermore, the region indicated by arrow IV is included in FIG. 3 . Said zone IV is a close-up of number 3 and will be illustrated by FIG. 4 .

Regarding the ingredients needed to produce this polymer concrete, refer to Example 5 discussed in detail later. The step of pushing the mixture through a cylinder comprising a rapidly turning screw mixing device to produce the final mixture results in a flexural state shear modulus (Young's modulus) in the range of about 20 to about 30 GPa and a compression of about 30 to about 40 GPa State Young's modulus.

A close-up of Region IV shown in Figure 4 demonstrates that Region 3 comprises a relatively large number of small filler particles 7 in the 0.004 mm diameter range, larger particles 8 in the 0.016 mm diameter range and around particle 9. The high shear force applied to the mixture during the mixing step causes a uniform distribution of the particles. During this step, the mixture is forced through a cylinder comprising a continuous rapid turning helical mixing device in order to produce the final mixture and a thin film outgassing unit that induces a material with very low void content. The dark portion 10 of Figure 4 represents the epoxy matrix.

Figure 5 schematically shows a Fuller sieve curve. The Fuller sieve curve of Figure 5 describes the ratio of fillers of different sizes used to obtain a densely packed concrete as follows:

$\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; ,</span>$

d is the particle size, D is the largest particle size, which is 300 μm according to FIG. 5 , P is the ratio of particles smaller than or equal to d, and n is the classification coefficient. n is usually set to 0.5 for round particles and to 0.37 for crushed particles (Fuller W.B., Thompson S.E., The laws of proportioning concrete, Transactions of the American Society of Civil Engineers, Paper Nos. 1053, 1907, pp67-143). 600EST, W12 EST and Sihelco 30 are different fillers with different particle ratios.

A Fuller sieve curve describes an optimized filler composite of a mixture, which provides optimized properties of the mixture, such as optimized strength and porosity or voids, etc. of the mixture.

Figure 6A shows a flow chart of a method 100 for manufacturing electrical insulators for medium or high voltage equipment, comprising the steps of pushing all the liquid components of the insulating material of the electrical insulator through a static mixer 101, adding at least one filler to the set Part 102, pushing the component and the at least one filler through a pipeline comprising a fast turning screw mixing device to mix the component and the at least one filler into a final mixture 103 of insulating material, passing the final mixture through the mixing device The outlet (flow-connected to the mould) leads to the mold 104a, the electrical insulator 105 is formed by at least partially curing the final mixture, the electrical insulator 106 is molded, the final mixture is degassed 107 by a degassing unit, and at least partially outside the mould. The final mixture 108 is post-cured.

Figure 6B shows a flow chart of a method 100 for manufacturing an electrical insulator for medium or high voltage equipment, comprising the steps of pushing all the liquid components of the insulating material of the electrical insulator through a static mixer 101, adding at least one filler to the set Part 102, pushing the component and the at least one filler through a pipeline comprising a fast turning screw mixing device to mix the component and the at least one filler into a final mixture 103 of insulating material, directing the final mixture to a vacuum a mold for casting (the mold is located in a vacuum chamber, the inlet of which is connected to the outlet of the mixing device, which is flow-connected to the mould) 104b, by at least partially curing the final mixture to form an electrical insulator 105, casting the electrical insulator 106, The final mixture is degassed 107 by means of a degassing unit, and the final mixture is at least partially post-cured 108 outside the mould.

Modes for Carrying Out the Invention

Several ways of possible embodiments of the inventive method are disclosed and discussed below by way of example.

Example 1 (aromatic epoxy composition (aromatic epoxy composition))

Epoxy resin compositions were made with the components as given in Table 1. The components were mixed using different mixing devices (2 different production size impeller mixers, and a production size continuous screw mixer). The mixing time was recorded and approximately 4 mm thick square slabs (150 x 150 mm) were cast, cured at approximately 80°C for approximately 8 hours and post-cured at approximately 140°C for approximately 4 hours. Samples for mechanical testing were machined from these panels and tested according to the criteria given in Table 2. Five samples were tested for each of the listed properties.

The production specification impeller mixer consists of two separate mixing vessels (for epoxy resin and anhydride hardener) equipped with impellers. In these containers, the filler is dispersed into the resin and hardener separately. The two components are then forced through a static mixer.

In continuous screw mixers, epoxy compositions are prepared by volumetric dosing of liquid components through a static mixer. Thereafter the filler is added and dispersed by pushing all components through a cylindrical pipe equipped with a quick turn screw which also contains a membrane degassing unit.

Table 1 The raw material formulation of the aromatic epoxy composition (the formula is given in phr (parts per hundred parts of epoxy resin))

type product name producer phr epoxy resin Epikote EPR845 Hexion(DE) 100 Anhydride hardener Epikure EPH05389 Hexion(DE) 84 Silica filler W12 Quarzwerke(DE) 320

Comparing impeller mixers A and B, it was observed that impeller mixer A produced better results after about 240 min of mixing than impeller mixer B after about 480 min of mixing. For impeller mixer B, a slight increase in mechanical properties with mixing time was observed.

As seen in Table 2, the continuous screw mixer resulted in better mechanical properties compared to the two impeller mixers. Even with a very long mixing time of about 480 min, the mechanical properties of a continuous screw mixer cannot be achieved. The mechanical properties are a function of the dispersion of the filler in the matrix material, which in turn depends on the mixing efficiency. This mixing efficiency depends on both mixing time and mixing geometry. Continuous screw mixers create very high shear forces compared to impeller mixers, and thus lead to good dispersion even with very short mixing times in the range of about 1 minute.

Table 2 Mechanical test results of aromatic epoxies treated with different mixing devices

Examples 2 to 4 (manufacture of filled cycloaliphatic epoxy and polymer concrete for insulators)

Epoxy compositions (Table 3) were made with the components as given in Table 4.

Epoxy compositions are prepared by volumetric dosing of liquid components through a static mixer. Thereafter the filler is added and dispersed by pushing all components through a cylindrical tube containing a quick turn screw which also contains a membrane degassing unit. The rest time of the material in the spiral is in the range of minutes, typically less than 1 minute. The outlet of the mixing pipe is directly connected by a hose to the heated steel mold installed on the heat press. This steel formwork is used for medium voltage outdoor insulators. The mold on the hot press was at a temperature of 125°C. After injection and an additional two hours of curing, the part was demolded.

Table 3 example composition (the formula is given in phr (parts per hundred parts of epoxy resin))

formula Example 2 Example 3 Example 4 Araldite CY184 100 100 100 Aradur HY1235 90 90 90 DY062 0.54 0.54 0.54 Silbond W12EST 354 354 354 Sihelco 30 576 726 Filler content (wt.%) 65 83 85

Table 4 Raw Materials of Cycloaliphatic Epoxy Compositions

type product name producer Cycloaliphatic epoxy resin Araldite CY184 Huntsman Advanced Materials(CH) Anhydride hardener Aradur HY1235 Huntsman Advanced Materials(CH) Accelerator DY062 Huntsman Advanced Materials(CH) Silica fume Silbond W12EST Quarzwerke(DE) silica sand Sihelco 30 Sihelco(CH)

Example 5 (Homogeneous Mixing of Highly Filled Polymer Concrete)

Polymer concrete compositions (Table 5) were made with the components as given in Table 6. Four silica packings of different sizes were selected following the Fuller sieve curve to obtain dense packing. This leads to improved mechanical properties, reduced risk of precipitation, reduced material cost and increased thermal conductivity.

This example evaluates filler dispersion for two dispersion methods: a laboratory-scale impeller mixer and a production-scale continuous screw mixer. For a laboratory scale impeller mixer, mix the components until a homogeneous mixture is obtained (typically 30-60 min). The mix was then degassed at 5 mbar and cast in a slab mold giving a 6 mm thick slab. The panels were cured at 90°C for 2 hours and at 140°C for 10 hours. The mixing process for the continuous screw mixer is described in Examples 2-4. Small samples were cut from the plates and prepared for microscopy. Samples were characterized by optical and scanning electron microscopy.

Table 5 example composition (the formula is given in phr (parts per hundred epoxy resin))

formula Example 5 Araldite CY184 100 Aradur HY1102 90 DY070 0.3 Silbond 600EST 66 Silbond W12EST 131 Millisil W3 312 Sihelco 30 569 Filler content (wt.%) 65

Table 6 Raw Materials of Cycloaliphatic Epoxy Compositions

type product name producer Cycloaliphatic epoxy resin Araldite CY184 Huntsman Advanced Materials(CH) Anhydride hardener Aradur HY1135 Huntsman Advanced Materials(CH) Accelerator DY070 Huntsman Advanced Materials(CH) Silica fume Millisil W3 Quarzwerke(DE) Silica fume Silbond W12EST Quarzwerke(DE) Silica fume 600EST Quarzwerke(DE) silica sand Sihelco 30 Sihelco(CH)

Claims (13)

1. one kind is used for making or the method (100) of the electrical insulator of high-tension apparatus, and described method (100) comprises step:

The all liq component that pushes the insulating material of described electrical insulator is passed through static mixer (101);

Add at least one filler and give described component (102);

Thereby push the final mixture (103) that described component and described at least one filler are mixed into described component and described at least one filler by the pipeline that comprises fast steering spiral mixing arrangement described insulating material;

The outlets direct of described mixing arrangement that described final mixture is connected to mould by flow type is to mould (104a);

Form electrical insulator (105) by partly solidified at least described final mixture; And

The described electrical insulator of molding (106).

2. one kind is used for making or the method (100) of the electrical insulator of high-tension apparatus, and described method (100) comprises step:

The all liq component that pushes the insulating material of described electrical insulator is passed through static mixer (101);

Add at least one filler and give described component (102);

Thereby push the final mixture (103) that described component and described at least one filler are mixed into described component and described at least one filler by the pipeline that comprises fast steering spiral mixing arrangement described insulating material;

Described final mixture is guided to the mould that is used for vacuum pressing and casting, and described mould is arranged in vacuum chamber, and the inlet of described vacuum chamber is connected to the outlet of described mixing arrangement, and its flow type is connected to described mould (104b);

Form electrical insulator (105) by partly solidified at least described final mixture; And

The described electrical insulator of molding (106).

3. the method for claim 1 (100), wherein said mould is the part of vacuum chamber.

4. method as claimed in claim 1 or 2 (100) further comprises step:

By removal unit with described final mixture degasification (107);

Wherein said fast steering spiral mixing arrangement comprises this removal unit.

5. method as claimed in claim 1 or 2 (100), wherein said curing is at least partially in carrying out in the described mould.

6. method as claimed in claim 1 or 2 (100), wherein said completion of cure is carried out in mould.

7. as each described method (100) in the claim 1 to 6, further comprise step:

Outside described mould, at least in part, preferably in forced convection oven, afterwards solidify described final mixture (108).

8. as each described method (100) in the claim 1 to 7, wherein at least two fillers add described component to; And

The mixed proportion of the filler of wherein said insulating material is followed the Fuller sieve-analysis curve, and it has Fuller and distributes:

$P={\left(\frac{d}{D}\right)}^n,$

Wherein d is the particle size of described filler, and D is a maximum particle size, and P is the ratio that is less than or equal to the particle of d, and n is a gradation factor.

9. as each described method (100) in the claim 1 to 8, comprise that fast steering spiral mixing arrangement is mixed into described component and described at least one filler that final mixture obtains in about scope of 2 to about 40GPa, the case of bending Young's modulus in about scope of 10 to about 30GPa preferably thereby wherein push the step of described mixture by described pipeline.

10. as each described method (100) in the claim 1 to 9, the volume of wherein said at least two fillers constitute described electrical insulator insulating material volume at least 49%.

11. as each described method (100) in the claim 8 to 10, the ratio of wherein said filler is determined according to 0.5 gradation factor n.

12. as each described method (100) in the claim 8 to 10, the ratio of wherein said filler is determined according to 0.37 gradation factor n.

Be used for or the electrical insulator of high-tension apparatus 13. each described method (100) is made in basis such as the claim 1 to 12.

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