Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B19/00—Apparatus or processes specially adapted for manufacturing insulators or insulating bodies
  • H01B19/04—Treating the surfaces, e.g. applying coatings

Definitions

• the invention relates to a production method for an electrical insulator, a hydrophobic plasma polymer coating being applied to a molded part of the insulator.
• An electrical insulator is understood to mean any electrically insulating component in an electrical circuit or in an electrical system. Such an insulating component is, for example, a barrier layer used in a circuit, an insulating sheathing of a current-carrying conductor or an electronic circuit board.
• An electrical insulator in the sense of the present document is, however, in particular also an insulator such as is used in electrical switching technology for routing or spacing current-carrying lines.
• an electrical insulator is also understood to mean a high-voltage insulator of the type used for routing or spacing overhead lines of high-voltage technology.
• An insulating housing of a high-performance semiconductor or an electrical switching element such as a thyristor or a thyratron also represents an electrical insulator in the sense of the present document.
• Electrical insulators are made from a variety of different materials. However, mainly plastic, glass and ceramics, especially porcelain, are used.
• An electrical insulator is usually made from the materials mentioned by shaping a deformable raw material and then curing it. Depending on the material used, curing takes place by cooling, by exposure to light or, in the case of ceramics, by firing.
• the shaped insulator which can also consist of several sections of different materials (one then speaks of a composite insulator), is described in the following called the molded body.
• the production of such molded articles of electrical insulators is general prior art.
• An example of the manufacture of a ceramic high-voltage insulator is the Siemens company publication "High-Voltage Ceramics for all Applications - by the Pioneer of Power Engineering!, Order No. A 96001-U10-A444-X-7600, 1997.
• an electrical insulator If an electrical insulator is used over a longer period of time, it is subject to more or less severe surface contamination depending on the place of use, which can considerably impair the original insulation behavior of the clean insulator. It comes e.g. to superficial flashovers due to the pollution. Because a rough surface becomes dirty faster than a smooth surface, e.g. a ceramic insulator with a surface glaze that technically improves the insulator. For other electrical insulators, the application of dirt-repellent lacquers or coatings to reduce the surface contamination in the long-term behavior is common.
• silicone rubber tends to gradually absorb water in a humid environment despite its hydrophobic surface properties. In the case of high ambient air humidity, this leads to a temporary reduction in the insulation behavior and, in the case of high voltages to be isolated, in the event of flashovers, the insulator is destroyed. Because of the water retention, the flashover no longer occurs along the surface, but partly through the insulator itself. Dust and dirt particles are also embedded in the surface of the silicone rubber with the same negative effects.
• the container is let in as working gas hexamethyldisiloxane (HMDSO) and a plasma is again generated from this gas at a pressure of more than 1.12 mbar.
• HMDSO working gas hexamethyldisiloxane
• the removed alkali ions are replaced by chemically firmly bonded hydrophobic groups by means of a plasma polymerization process.
• a plasma-polymeric, hydrophobic coating is formed.
• the hydrophobicity and adhesion of the plasma polymer coating is disadvantageously dependent on the type of glaze. So it turns out that a brown glaze, which has much less sodium ions than a white glaze, offers better conditions for a plasma polymerisation process and indicates favorable chemical compounds for the formation of the hydrophobic layer.
• the known method accordingly produces a hydrophobic coating on the glaze of a ceramic insulator by plasma polymerization, the quality of the coating, however, being strongly dependent on the composition of the glaze.
• the procedure was carried out in a Leiden bottle on very small ceramic pieces. It is not suitable for coating large electrical insulators.
• the object of the invention is to provide a production method for an electrical insulator, a hydrophobic plasma polymer coating being applied to a molded piece of the insulator.
• the hydrophobic plasma polymer coating should be applied with the same quality regardless of the material of the molded part or the material of its surface.
• the applied plasma polymer coating should be permanent and hard and firmly connected to the material of the fitting.
• this object is achieved by a production process with the following steps:
• a molded piece of an insulator produced in a known manner is introduced into an evacuable chamber of a plasma reactor, the chamber is evacuated, a non-polar or non-polar working gas is admitted into the chamber, a working pressure between 1 and 2 is introduced into the chamber under continuous gas flow.
• 10 "5 mbar and 5 • 10 " 1 mbar by generating an electric field a plasma is formed from the working gas, the electrical power input per chamber volume between 0.5 kilowatt / m 3 and 5 kilowatt / m 3 and the gas flow per Chamber volume between 10 sccm / m 3 and 1000 sccm / m 3 is set that
• Plasma is maintained at least until a closed coating of the plasma polymer formed from the plasma of the working gas is formed on the surface of the molding, the field is switched off and the finished coated insulator is removed from the chamber.
• the unit sccm is a standard unit in plasma technology, means standard cubic centimeter (English: Standard cubic centimeter), and denotes the gas volume converted to standard conditions.
• the standard conditions are defined by a temperature of 25 ° C and a pressure of 1013 mbar.
• the invention is based on the fact that, according to the prior art, in the process for producing a hydrophobic plasma polymer coating on the glaze of a ceramic insulator, a working pressure of more than 1.12 mbar is used. At this relatively high working pressure, the mean free path between the ionized molecules in the plasma is relatively small. Interaction of the ionized molecules therefore leads to polymerisation and failure of the substance formed in the plasma. On the surface of the insulator itself, on which the plasma polymer should actually form, there are inhomogeneities in the coating. According to the prior art, ion bombardment forms on the surface of the substrate to be coated. This ion bombardment is inhomogeneous.
• the working pressure cannot simply be reduced, since then the pre-treated glaze can no longer be processed by the ions of the plasma. A replacement of the alkali ions knocked out of the glaze by chemically firmly bonded groups of the plasma polymer formed can then no longer be achieved.
• the plasma polymer coating formed in such a procedure is independent of the material of the chosen insulator. No pretreatment of the surface of the insulator is necessary to e.g. by knocking out alkali ions from a glaze using argon sputtering to create a reactive surface to which the plasma polymer then chemically binds. At the selected working pressure and the selected power input, the plasma polymer formed obviously crosslinks with one another so well that the chemical bond to the surface of the insulator is irrelevant.
• An abrasion-resistant and hard coating is formed from the plasma polymer.
• the non-polar or non-polar groups of working gas result in a less reactive, i.e. low-energy plasma polymer surface as coating on the surface of the insulator. This surface is highly hydrophobic, i.e. water repellent.
• the plasma polymer coating is resistant to UV exposure. Furthermore, such a coating or layer does not absorb water. The penetration of dust and dirt particles into the surface is also prevented.
• plasma polymer denotes a polymer produced by the plasma process which, in contrast to a polymer produced by conventional chemical means, has a significantly higher crosslinking of the individual molecular groups and teremander has, not directed, but is amorphous and also has a much higher density.
• a plasma polymer for example, is distinguished from a conventional polymer by a broadening of the infrared oscillation bands measured by IR spectroscopy.
• the method according to the invention offers the advantage that an electrical insulator with a permanent, abrasion-resistant and highly hydrophobic plasma polymer coating can be produced.
• the size and the material of the molded piece of the insulator intended for the assignment do not matter.
• the method is particularly relevant for insulators with large dimensions, e.g. High voltage insulators with lengths of a few meters, suitable.
• the electrical power input per chamber volume is between 1 kilowatt / m 3 and 3.5 kilowatt / 3 .
• the gas flow per chamber volume is set between 20 sccm / m 3 and 300 sccm / m 3 .
• the plasma is maintained until the plasma polymer coating has a layer thickness between 100 nm and 10 ⁇ m.
• an oxygen-containing gas in particular air
• a pressure between the chamber and the chamber is temporary 1 and 5 mbar prevail, with a gas being ignited for a period of between 1 second and 5 minutes.
• the plasma is ignited in a clocked manner. It has been shown that the homogeneity of the plasma polymer coating can be increased in this way.
• the plasma is ignited with a clock rate of 0.1 to 100 Hz.
• the plasma can be ignited by generating an electric field in a known manner.
• the electrical field can be injected inductively or capacitively by means of a microwave generator.
• Investigations have now shown that plasma ignition by applying a voltage to electrodes arranged on the chamber is particularly suitable for treating molded pieces of large and elongated insulators.
• One electrode is e.g. rod-shaped, while the other electrode is formed by the chamber wall itself. Two opposite rod-shaped electrodes can also be used.
• the plasma can be generated by an electric field that is constant over time.
• the electric field is an alternating electric field with a frequency between 1 kHz and 5 GHz.
• the actual frequency used depends on the working gas used.
• a working pressure between 1 * 10 " ⁇ mbar and 1 • 10 " 1 mbar is set in the chamber. It is particularly favorable for the production of the plasma polymer coating if a hydrocarbon, in particular actylene and / or methane, is used as the working gas.
• an organosilicon or an organofluorine compound is used as the working gas.
• the plasma polymer formed from the plasma of these compounds is characterized by a high degree of crosslinking of the individual molecular groups with one another. Due to this networking, the generated assignment is extremely stable and protected against external influences. It is extremely hard.
• plasma polymers which have been produced from the plasma of non-polar or non-polar groups having silicon-organic or fluorine-organic compounds show a high and permanent hydrophobicity.
• an additional gas is added to the working gas. It is advantageous if the additional gas is a noble gas, a halogen, in particular fluorine, oxygen, nitrogen or a mixture thereof.
• the manufacturing process for a plasma-coated insulator is particularly suitable for a high-voltage insulator.
• a high voltage insulator can have dimensions from a few centimeters to a few meters.
• the method is suitable for a long-rod insulator such as is used to support overhead lines.
• Such an insulator is used as a molded body with a number of shaped shielding ribs in order to enlarge the creepage distance between the two ends of the insulator.
• Such an insulator offers reliable protection against flashovers, even if its surface is dirty.
• an insulator provided with a plasma polymer coating in accordance with the production method according to the invention has a highly hydrophobic surface, it is reliably protected against dirt deposits by contaminants dissolved in water. In this way, since the insulator is protected against contamination, especially when it is left standing for a long time, it is not necessary to increase the creepage distance by forming shielding ribs. It is even conceivable to design the insulator in an ideal shape as an elongated tube. In this way, an enormous material saving is recorded compared to a conventional high-voltage insulator.
• the manufacturing process for producing the shaped body is also particularly simple and is also considerably cheaper than a manufacturing process for a shaped body provided with shielding ribs.
• the quality of the plasma polymer coating produced is independent of the material of the molded body of the electrical insulator, it is particularly expedient if the molded body is made of a fired ceramic, a glazed, fired ceramic, a glass or a plastic, such as a silicone rubber, for example. an epoxy resin or a glass fiber reinforced plastic.
• the manufacturing method according to the invention provides an insulator with a highly hydrophobic surface, which even surpasses the properties of a glazed ceramic insulator that is provided with no hydrophobic coating. The rough surface does not pose any difficulties for the application of the coating.
• a molded article made of a silicone rubber can also be closed by the process according to the invention an insulator with a hydrophobic plasma polymer coating.
• an insulator with a hydrophobic plasma polymer coating In this way, the good electrical and dirt-repellent properties of an insulator made of a silicone rubber are retained unchanged, with the undesirable properties of the silicone rubber, namely water retention and / or the storage of dust and dirt particles, being reliably avoided.
• any plastic can be further processed by the method according to the invention into a high-quality insulator provided with a hydrophobic surface.
• the invention makes it possible to produce a molded article for an insulator from any plastic and to provide this molded article with a hydrophobic coating by means of plasma polymerisation.
• Such a plastic insulator has a significantly improved long-term behavior with regard to its insulation capacity compared to a conventional plastic insulator.
• such plastic insulators have been able to replace expensive silicone rubber insulators.
• the invention also opens up the possibility of avoiding complex shapes for an insulator for increasing the creepage distance.
• a kneadable mass is produced in a known manner from the starting materials kaolin, feldspar, clay and quartz by mixing with water, from which a hollow cylindrical clay body with a number of shielding steps is produced by twisting off.
• the clay body is dried and fired into a shaped piece.
• the length of the shaped piece is approx. 50 cm.
• the shaped piece of the ceramic insulator becomes an evacuable chamber with a volume of 1 m 3
• Plasma reactor introduced. After evacuating the chamber, a mixture of hexamethyldisiloxane and He- lium introduced. With a continuous gas flow of 30 sccm of hexamethyldisiloxane and 30 sccm of helium, a working pressure of 9 • 10 "3 mbar m of the chamber is set by controlled pumping. Under these conditions, a plasma is ignited by means of electrodes in the working gas.
• the electrodes are ignited electrical alternating field with a frequency of 13.56 MHz and a power of 2 kW
• the molded piece, now provided with a hydrophobic plasma polymer coating, ie the finished high-voltage insulator, is removed from the ventilated chamber.
• a molded piece of the ceramic high-voltage insulator produced according to Example 1 is introduced into an evacuable chamber with a 350 liter volume of a plasma reactor. Vinyltnmethylsilane is used as the working gas. At a flow of 100 sccm, a working pressure of 1.5 • 10 "1 mbar m is set in the chamber. A plasma is ignited in the chamber by applying an electrical voltage to electrodes. The voltage is an AC voltage with a frequency of 13.56 The power consumed is 1.2 kW. The molded piece, which has a hydrophobic plasma polymer coating, is removed from the ventilated chamber after a period of 20 minutes.
• FIG. 1 shows a system for applying the hydrophobic plasma polymer coating to a molded piece of an insulator
• FIG. 1 shows a system for applying a hydrophobic plasma polymer coating on a molded piece of an electrical insulator.
• the system comprises a plasma reactor 1, which is designed as an evacuable metallic chamber 2 with a sight glass 3 arranged therein.
• a pump station 5 To evacuate the chamber 2, a pump station 5 is provided, which has an oldiffusion pump 6, a root pump 7 and a rotary vane pump 8 connected in series in series.
• a three-way valve 10 Via a three-way valve 10, either the pump station 5 or a ventilation valve 12 of the suction line 13 connected to the chamber 2 m can be activated.
• a controllable throttle valve 14 is additionally installed in the suction line 13 to control the pump power.
• a Pirani pressure measuring device 15 connected to the interior of the chamber 2 and a pressure indicator 17 connected to it are provided for pressure monitoring.
• the Pirani measuring device 15 works reliably up to a pressure range of 10 -3 mbar.
• a so-called baratron 19 is provided which is connected to the interior of the chamber 2.
• the Baratron 19 outputs reasonable pressure values down to a few 10 "4 mbar.
• a pressure controller 21 is connected to the outlet of the bar cartridge 19, which compares the measured actual value for the prevailing pressure with a predetermined target value, and controls the throttle valve 14 via a control line 22.
• the throttle valve 14 is opened a little less via the control line 22, so that the suction power of the pump station 5 with respect to the chamber 2 is reduced.
• An electrical supply unit 25 is provided for supplying current and voltage to the bar 19.
• a supply line 27 is connected to the chamber 2.
• a series of process gas lines 30 can be connected to the supply line 27 via a control valve 28 and a number of flow regulators 29.
• the process gas lines 30 are each joined to a compressed gas bottle for gas is ⁇ .
• the five process gas lines 30 shown in FIG. 1 are connected, for example, to pressurized gas bottles for hexamethyldisiloxane, vinyltrimethylsilane, argon, oxygen or nitrogen.
• a specific gas mixture can be put together via the flow regulator 29 and fed to the chamber 2 via the supply line 27.
• the corresponding flow of the components of the working gas is controlled via the flow regulator 29 by means of connecting lines 31 via a gas flow regulator 33.
• the gas flow regulator 33 itself is connected to the pressure regulator 21. In this way, with a given flow of components of the working gas, exactly a desired working pressure in the chamber 2 is achieved by actuating the throttle valve 14.
• a plasma is ignited in the working gas in the interior of chamber 2 by applying an electrical voltage an HF electrode 35. This is formed in the interior of the chamber 2 as an elongated rod electrode 36. As a second elec trode ⁇ a certain extent, the metallic housing acts of the chamber 2 itself. For generating the voltage is aorsgenera- gate 37 is provided.
• the shaped piece of the electrical insulator produced in a manner known per se is introduced into the chamber 2 of the plasma reactor 1.
• the chamber 2 is then evacuated by means of the pump station 5 with the three-way valve 10 in the appropriate position.
• the chamber is admitted with a defined inflow of oxygen.
• the pressure prevailing in the chamber is regulated to 3 mbar.
• a plasma with a duration of between 1 second and 5 minutes is ignited in the chamber 2 by means of the voltage generator 37 by applying an electrical voltage to the HF electrode 35. In this way, surface contaminants, especially fats and oils, are cleaned from the surface.
• the oxygen supply is then throttled by means of the corresponding flow controller 29.
• the chamber is evacuated again and the chamber is let in under controlled flow of 300 sccm hexamethyldisiloxane and helium.
• the suction power of the pump station 5 is controlled via the throttle valve 14 in such a way that the working pressure prevailing in the chamber 2 is 9 ⁇ 10 "2 mbar
• a plasma is ignited from the working gas in the voltage generator 37 by means of the HF electrode 35 m in the chamber 2.
• An alternating voltage with a frequency of 13.56 MHz is used as the voltage, and the power consumption is 3.5 kW to generate the hydrophobic plasma polymer coating.
• the plasma remains ignited for a period of 5 minutes to 60 minutes.
• the chamber 2 is then vented via the ventilation valve 12 when the three-way valve 10 is in the appropriate position and the throttle valve 14 is slowly opened.
• the finished insulator provided with a hydrophobic plasma polymer coating is removed from chamber 2.
• FIG. 2 shows a ceramic high-voltage insulator 45 in a partially broken open view with a number of shielding steps 46.
• the high voltage insulator consists of
• the high-voltage insulator 45 furthermore has connecting pieces 47 on both sides.
• the ceramic high-voltage insulator 45 was provided in a system designed according to FIG. 1 with a hydrophobic plasma polymer coating by igniting a plasma in the working gas hexamethyldisiloxane.
• this hydrophobic plasma polymer coating can be easily recognized in the enlarged section III shown in FIG. 3 according to FIG.
• the thickness of the coating applied is approximately 1000 nm. It can be seen very easily that a high degree of crosslinking has developed between the molecular groups of the plasma polymer coating.
• the plasma polymer coating has a high hardness, which can be explained by the oxygen bonds of the individual silicon atoms.
• the plasma polymer coating formed from this working gas also has a low energy and is therefore highly hydrophobic.
• the hydrophobicity and long-term stability of the plasma polymer coating produced according to the manufacturing process according to the invention is demonstrated in the following on the basis of tests:
• a glazed ceramic high-voltage insulator is compared with a ceramic high-voltage insulator which is identical in shape and which is provided with a hydrophobic plasma polymer coating.
• the plasma polymer coating was generated by plasma ignition in a working gas of hexamethyldisiloxane and helium. The parameters chosen were identical to those mentioned in Example 1.
• the duration for the formation of the plasma polymer coating was 30 minutes.
• the layer thickness of the applied plasma polymer coating was 1000 nm.
• the plasma polymer coating is applied directly to the glaze.
• both high-voltage insulators The length of both high-voltage insulators is 50 cm.
• the high-voltage insulators have nine shielding ribs, which are spaced apart by a shield spacing of 45 mm.
• the screen diameter is 223 mm; the stem diameter is 75 mm. Given the number of shields, both insulators have a length of 1612 mm.
• both insulators The insulation behavior of both insulators is tested in accordance with the salt spray method in accordance with IEC 507 (1991).
• the plasma polymer coating was applied directly to the glaze.
• both high-voltage insulators are washed with trisodium phosphate.
• air conditioning and mist conditioning tests and one-hour salt mist tests at a test voltage of 23 kV (AC voltage) are carried out on both high-voltage insulators at the highest salt mass concentration of 224 kg / m 3 .
• the test voltage and leakage current are continuously recorded.
• the flashover voltages determined on the high-voltage insulator with plasma polymer coating in the preconditioning test correspond to the measured flashover voltages of the glazed ceramic high-voltage insulator. This means that the increase in hydrophobicity due to the plasma polymer coating has no influence on the breakdown voltages.
• a ceramic high-voltage insulator designed according to experiment 1 and provided with a plasma-polymer coating is subjected to a 1000-hour salt spray test in accordance with IEC-1109. Even after being used in a salt spray for 1000 hours, the high-voltage insulator still had the same properties as at the start of the test. This proves the durability and the high hydrophobicity of the plasma polymer coating. Such a result cannot be achieved with untreated, glazed ceramic high-voltage insulators.
• the wetting angle is examined on three different ceramic high-voltage insulators, all of which are provided with a hydrophobic plasma polymer coating according to Example 1.
• the shaped pieces treated were all ceramic shaped pieces.
• the insulator material was additionally provided with a brown glaze, for fitting B with a white glaze.
• the insulator C fitting was unglazed.
• the wetting angles are determined according to standard DIN-EN 8 28 for distilled water and for NaCl-containing water with a NaCl content of 25% by weight. The result is summarized in Table 3. It should be noted that located on the surface of the unglazed insulator due to the size ⁇ ren roughness at the same hydrophobicity, a greater wetting angle setting as on the surfaces of the glazed insulator.

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• Treatments Of Macromolecular Shaped Articles (AREA)
• Insulating Bodies (AREA)
• Insulators (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)
• Coating Of Shaped Articles Made Of Macromolecular Substances (AREA)

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• 1998
  • 1998-08-07 DE DE19835883A patent/DE19835883A1/de not_active Withdrawn
• 1999
  • 1999-07-27 CN CN99809420A patent/CN1312945A/zh active Pending
  • 1999-07-27 EP EP99950435A patent/EP1114427A2/de not_active Withdrawn
  • 1999-07-27 WO PCT/DE1999/002302 patent/WO2000008658A2/de not_active Application Discontinuation
  • 1999-07-27 CZ CZ2001431A patent/CZ2001431A3/cs unknown
  • 1999-07-27 BR BR9912783-0A patent/BR9912783A/pt not_active IP Right Cessation
  • 1999-07-27 JP JP2000564212A patent/JP2002522876A/ja not_active Withdrawn
• 2001
  • 2001-02-07 NO NO20010658A patent/NO20010658L/no unknown
  • 2001-02-07 US US09/778,532 patent/US6497923B2/en not_active Expired - Fee Related

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