DE2741478A1 - METHOD OF MANUFACTURING OIL CABLES - Google Patents

Description

The invention relates to a method of making a oil-filled cable.

An oil cable, i.e. a cable that is filled with oil, basically shows such a structure that an oil channel of the cable is filled with an insulating oil. The oil pressure is controlled by an outside arranged pressure control device upright, thereby preventing the formation of empty spaces and decomposition of the cable will. Oil cables in this way have great reliability and are therefore economical. You can find in the meantime wide application in energy supply.

Although the process used to manufacture conventional oil cables is definitely is known, a summary of this method is briefly given below for the purpose of comparison with the invention.

(1) A wire or wire core is wrapped in paper and collected in a ring or wound on a roll.

(2) The cable core thus wound is placed in a drying tank and heated while reducing the pressure so that the moisture is removed

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Activity content of the paper insulation is lowered to a value of 0.1% or less.

(3) The paper insulation is then impregnated with a sufficiently dried and degassed insulating oil. The cable core must remain in a vacuum to avoid any renewed entry of moisture.

(4 ·) However, this method requires a long drying time, and consequently the manufacturing time of an oil cable increases in total. A reduction in the drying time is therefore very important, in particular to reduce manufacturing costs.

The object of the invention is primarily to reduce the drying time in the manufacture of oil cables. It should a method can also be specified in which the individual method steps in the manufacture of such a cable, namely wrapping with paper, drying, impregnating and applying a Protective cover, can be carried out one after the other.

This object is achieved according to the invention in that one Surrounds the core of the cable with damp paper insulation, which can be obtained by wrapping it with paper, including plastic paper, obtained by pressing heated, dried and degassed insulating oil into an oil duct and that this oil is radially passed through the paper insulation flow and can escape together with the moisture from the cable core, whereby the insulating oil obtained is heated, dried and degassed and pressurized to be sent back to the oil gallery for recycling.

In a preferred embodiment of the invention, a closed one extending in the longitudinal direction around the circumference of the core is provided Hardly planned; in this case, the core again has the moist paper insulation after the wrapping.

Here, the outer sheath made of aluminum or lead can be used to form the closed space between this outer sheath and the cable core are provided. Also the core of the cable can be in one

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Pipe to form the enclosed space are drawn in along the circumference of the cable core; after all, the core can can also be used in a vacuum drying tank to form this closed kaunie.

Further details, features and advantages of the invention emerge from the following description in some cases. Embodiments and on the basis of the schematic drawing and the claims. Show it:

1 shows the process step of impregnating and drying an oil cable which has an aluminum outer sheath around its core;

2 shows the cross section of a cable with a lead outer sheath which is provided at times;

3 shows a further embodiment of the invention using a drying tank;

4 shows an enlarged longitudinal section of the cable core according to Fig. 3;

5 shows a device in which the core of a cable is drawn into a tube and is dried and

FIG. 6 shows an enlarged longitudinal section of the cable core according to FIG. 5.

First of all, the exemplary embodiment according to FIG. 1 will be discussed, according to which an oil cable or an oil-filled cable is an aluminum outer sheath around a core of the cable, in Fig. 1 is the oil cable generally designated 10, and it has a paper wrapper to be treated. Basically, it includes a ladder 12, an oil channel 14, a paper insulation 16, an Alurainium outer shell 18 and a closed space 20, which extends in the longitudinal direction between the aluminum outer shell and the paper insulation extends; it forms an oil return channel. The end of the cable is provided with a cover 24- to prevent the leakage of oil. Such a cover is not required if oil is introduced from both ends.

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A heating device known per se: for drying and degassing the oil is denoted by 2G. The interior of this device is kept at reduced pressure by means of a vacuum device 28. For example, the oil flow is heated to about SO ⁰ C in order to dehydrate and dehumidify the oil; it flows through the device in the form of a spray or oil film.

The dried, degassed and heated oil is pressurized by a pump and introduced into the oil channel 14. While the radial flow of the oil, which is indicated by arrows, through the paper insulation, the oil absorbs the moisture and gases that are present in the paper insulation, and flows into the closed space 20. From here, the oil returned to heater 26 for drying and degassing via pipe $ 2. There this oil is in its initial state returned to be used again (recycling).

If the cable is comparatively long, the pressure drops in the middle area so that the drying process can take a long time even if the oil is supplied from both sides of the cable. However, this difficulty can be solved satisfactorily by increasing the pressure of the supplied oil.

The impregnation is in accordance with the method according to the invention completed when the desired degree of dryness is obtained and the oil circulation is interrupted. If an aluminum outer shell is used, so the completely impregnated product is ready for use. The method according to the invention is thus distinguished by a remarkable Simplicity.

If a lead outer sheath is used with such an oil cable, as a rule, there are hardly any interruptions between this lead outer sheath and the core of the cable. Accordingly, a cable core becomes after being wrapped in paper, provided with a lead sleeve 34 that is present at times and on the inner surface of which grooves are provided, so that enclosed spaces 36 between the core and the lead envelope

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are available for the purpose of oil forwarding. This completed Spaces are preferably designed so that they can be used to reduce of the flow resistance of the oil extend in the longitudinal direction. The subsequent impregnation step is the same as in the embodiment in which the cable was provided with an outer aluminum sheath. The temporarily The intended lead envelope should be removed immediately before any remaining lead envelope is applied. In some cases it can the oil will also flow in from the outside of the core.

In Fig. 3, a further embodiment of the invention is shown. The interior of a drying tank 11 can be kept at a comparatively high temperature and reduced pressure by means of steam heating or a heater and evacuation by means of a vacuum pump 13. A few pans 15 with a cable core 17 arranged therein are provided in the tank. 4- shows a longitudinal section of such a core 17. Here the conductor is designated with 19, the oil channel with 21 and the overlapping paper insulation with 23. The pipes 27 are provided as outlets for oil in the pans 15. The conventional heating device for drying and degassing oil is now designated by 29. An oil pump 31 is arranged in a line connecting the drying tank 11 to the heating device 29. A further oil pump 33 and a vacuum pump 13 are arranged in a the oil passages 21 of the ^lv abels connected with the heater 29 oil passage. Valves are provided with the reference symbol 35.

The following is the drying process of an oil-filled cable described, the device described above being used.

(1) The core 17 of the cable, which is a comparatively Having moist paper insulation after being wrapped in paper is wound up in the interior of a pan 15. There will be several Pans having cable cores are inserted into the drying tank 11, and the interior of the tank becomes at the same high temperature and maintained under the same reduced pressure as described above.

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(2) Simultaneously with the above-described step, a cable insulating, which was dried in the heater 29, and degassed and a temperature of 80 ⁰ g or more, brought by the pump 33 under pressure and is introduced into the oil passages 21 of the cores 17th

(3) The Ul then flows radially through the layered Paper insulation 23, as indicated by the arrows, and flows out there. As a result of this leakage of the oil Paper insulation dried and degassed.

(4) That through the cable cores 17 into the pan The oil 37 that has flowed is collected in the bottom area of the drying tank 11 and partially dried and degassed there (since the interior of the tank is kept at high temperature and reduced pressure). This oil 37 is transferred from the tank 11 into the heating device 29 a suction pump 31 passed for drying and degassing. In this device the oil is dried and degassed to the required sufficient extent. Then it will turn into the Oil channels 21 of the cable cores 17 initiated for reuse.

(5) After the drying has been carried out in the manner described above, the impregnation step is continued,

Another embodiment of the invention is shown in FIGS. Here, a cable core 40 has after being sheathed with paper a conductor 42, an inner oil passage 44 and an overlapping paper insulation 46. An essentially U-shaped Pipe section 48 has a comparatively large inside diameter and a length of approximately 500 to 600 m. The curved part is slightly raised and both ends are slightly inclined so that the oil flows towards both ends. The core 40 of the cable is in the pipe section 48 pulled. To support the introduction and removal of the cable core are rollers 50 with horizontal axes and rollers 52 arranged with vertical axes in the tube. To maintain a reduced pressure in the interior of the pipe is a vacuum pump 54 is provided. The heating device for drying and degassing is denoted by 56, the oil pumps by 58 and 60. Although in the embodiment according to FIG. 5, the oil

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inserted into the core of the cable at both ends of the oil channel as an alternative to this, the oil can naturally only flow in at one end. In this case you need to take precautions be taken against leakage of the oil at the other end of the ülkanales.

The drying process of an oil-filled cable with the just described device is as follows:

(1) After wrapping with paper, the core 40 of the Cable pulled into the Kohrbiegung 48; the annular openings between the cable core and the tube wall are sealed at both ends.

(2) The insulating oil heated and degassed in the heating device 56 has a temperature of 80 ° C. or more, is pressurized by the pump 53 and introduced into the inner oil duct of the core 40 of the cable at its two cortices. Equal-ZcLtX ₁ ; becomes the iimcnraun dos Rohres or dex ¹ ^ ear bend ;; 4d evacuated by means of the vacuum pump ^.

(3) The oil flows radially through the layers of paper insulation 4b - this is again illustrated by arrows. It then exits the core 40 of the cable. Based on these The flow of the insulating oil becomes the layered conductor insulation 46 dried and degassed. The oil leaked from the cable core 40 and entered the pipe 48 is used for drying purposes and degassing in the heating device 56 by means of the suction pump 60 withdrawn from both ends. In this device, the oil is again dried and degassed in the required oil. That so The oil obtained is fed to the oil channel 44 of the core 40 of the cable for repeated use.

The person skilled in the art recognizes that the invention has been written in the foregoing on the basis of examples and that, on the other hand, numerous Changes can be made without departing from the scope of the invention.

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The advantages obtained with the method according to the invention and effects can be specified as follows:

(1) The moisture in the layered paper insulation can be removed comparatively quickly and in large quantities, in addition, the drying time can be significantly reduced - this due to the high temperature in the dried and degassed state that flows through the paper insulation;

(2) The i> cable core without outer cover can practically without mechanical restriction to be dealt with; the creation of "soft spots" that lead to dielectric strength errors leading of the cable is avoided;

(3) The UI that has absorbed the moisture and the gases can be dried and degassed relatively easily, and the oil loss is reduced because the regenerated oil is reused.

(4) The treatment time is reduced, namely, because the treatment steps of wrapping with paper, application of the metallic cover and drying and impregnation are carried out one after the other will.

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Claims (6)

PATENT CLAIMS .j A process for the production of an oil-filled cable, characterized in that a core of the cable is wrapped with paper so that it has undried paper insulation after the wrapping, that heated, dried and degassed insulating oil is allowed to flow under pressure through a channel of the core, that the insulating oil is allowed to flow radially out of the core through the paper insulation, the paper insulation being dried and impregnated and that the oil thus discharged is then heated, dried, degassed and pressurized again, whereupon it flows into the oil channel again. 2. The method according to claim 1, characterized in that an outer shell is provided to form a closed, longitudinally extending space around the core, and that the insulating oil can then flow into the oil channel, radially through the paper insulation and into the closed space . 3. The method according to claim 1, characterized in that the ι of the undried paper insulation provided core is in a high temperature and reduced pressure having drying tank and then the heated insulating oil through the oil channel and radially through the insulating paper can escape from the core. 809812/0831 OR ¹ GINAL INSPECTED 77AH78 4. The method according to claim 1, characterized in that the core with its undried paper insulation is drawn into a tube, that an interior of the tube is kept under reduced pressure and the insulating oil is pressed out of the core through the oil channel and the paper insulation. 5. The method according to claim 2, characterized in that the outer sheath consists of aluminum and is used as a cable sheath. 6. The method according to claim 2, characterized in that a lead jacket is temporarily provided to form the closed space and oil duct. 809812/0831