DE3013954A1 - HUMIDITY PROTECTED PLASTIC-INSULATED ELECTRIC POWER CABLE - Google Patents

Description

Cable and metal works
Gutehoffnungshütte Aktiengesellschaft

April 10, 1980 1-1745

Moisture- proof, plastic-insulated electrical power cable (addendum to patent ... (application P 30 05 875.4))

The subject of the main patent is a moisture-protected plastic-insulated Electric power cable for medium or high voltage with a metallic screen arranged over the outer conductive layer Wires, the spaces between which are sealed in the longitudinal direction. Below the screen is in contact with the outer conductive layer in an open cross lay a layer of strips that swell when exposed to moisture. This measure enables a production technology problem-free achievable protection that is fully effective if moisture penetrates the cable due to damage to the sheath. The swellable tape sucks full, swells up and thus blocks the spaces between the wires of the umbrella. These shield wires can be developed by a Umsei or in the form of a so-called ceander location. In the latter case, the layer of the swellable tapes also serves to hold the individual wires the Ceander location, d. H. of the concentric conductor in the form of alternating Direction of lay of stranded single wires. The swollen material prevents the water from migrating further; the damage site remains local limited. Above all, by ciie measure according to the main patent, however ensures that the constipation agent is evenly distributed over the circumference

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of the cable are distributed, d. H. are available wherever necessary moisture penetration can take place.

The present invention relates to a further embodiment of the object according to the main patent. According to the invention, a screen present in the form of a closed metallic shell is in contact with the underneath outer conductive layer in an open regular lay a layer of strips that swell when exposed to moisture. This combination of closed Metal screen and the one already described in more detail in the main patent, in Open cross-lay tape has the advantage, among other things, that with a subsequent gap formation due to the heat play that occurs during the operation of the cable and despite the vastly different coefficients of thermal expansion of plastic insulation and metal of the closed shield between the outer conductive layer and the shield for sufficient Sealing of the cable is also taken care of in the longitudinal direction. The gap formation can be particularly noticeable in cables with a closed lead sheath as a screen, which is pressed onto the cable core and gradually rests tightly on the cable core during manufacture. However, if the core expands when the cable is in operation, the lead sheath can remain stretched will. In the event of a subsequent shrinkage of the insulation, this consequently remains longitudinal gaps between lead sheath and z. B. outer conductive layer. In the event of damage to the intrinsically watertight Shell and water ingress can dissipate the penetrated in the crevices Moisture. Then, however, damage to the insulation cannot be avoided here too »which is ultimately caused by" water treeing " electrical breakdowns.

Instead of a pressed-on lead jacket, the closed metallic shell but also consist of a longitudinally seam-welded, possibly corrugated metal strip of thin wall thickness, which is formed into a pipe. Because of the required conductivity copper and aluminum have proven to be the most suitable for this.

As already mentioned in the main patent, tapes in the form of so-called Swellable nonwovens have proven to be advantageous for the implementation of the invention, in which swellable materials are incorporated or incorporated «The basis

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Such swellable nonwovens form plastic layered nonwovens, their middle layer or layers of swellable material are built up or which contain such. The structure of such materials can be chosen, for example, so that materials capable of swelling on a "thicker" non-woven carrier, for example in powder form, for example based on cellulose or in the form of synthetic swelling compounds, applied and held by an overlying extremely thin fleece layer. This thin fleece layer ensures short-term access to water to the swellable material. The anchoring of the swellable materials in the fleece ensures a z. B. compared to an order of swellable powder simpler production process and ensures that the clogging materials are still present after the cable has been manufactured, transported and laid are present at the points where they effectively prevent the forwarding of water that has penetrated in the event of moisture penetration.

It can sometimes also be advantageous if the fleece material has indicators that indicate how far into the cable a water ingress may have occurred has spread lengthways.

Becomes a permanent electrically conductive connection between the outer conductive layer and screen are required, then it can be useful to produce the layer from conductive, swellable tapes. In this case it is possible because of the electrical Contact between the conductive layer and the screen is not interrupted, the swellable fleece material is applied in the form of a closed covering.

The invention is based on the example shown in the figure single core medium voltage cable explained in more detail.

Above the z. B. formed as a solid conductor conductor 11 is the inner conductive layer 12 arranged. It is covered by the insulation 13 made of a crosslinked or non-crosslinked polyethylene. The one covering this insulation outer conductive layer is denoted by 14.

In order to have a longitudinal migration between the To prevent the outer conductive layer 14 and the lead sheath 17, the two strips 15 and 16 of swellable nonwoven are arranged under the lead sheath 17. They are applied in an open regular lay to provide insulation in the case

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Nonwoven material to ensure sufficient electrical contact between the lead jacket 17 and the conductive layer 14. ^{The outer sheath 1} 18 made of a mechanically resistant material is attached to the lead sheath
Insulating material such as polyvinyl chloride.

The invention is of course not limited to the illustrated embodiment. So instead of the lead jacket, a copper or
Use aluminum jacket; Also, under the plastic jacket 18, there can also be a corrosion protection for the metal jacket arranged underneath.

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Claims (8)

Cable and metal works
Gutehoffnungshütte Aktiengesellschaft April 10, 1980 1-1745 Claims f i.jFeuchtigkeitsgeschütztes plastic! soliertes power cable for Mittel-- or high voltage with an outer conductive layer disposed over the metal shield according to patent ... (application P 30 05 875.4), characterized. that beneath the screen, which is in the form of a closed metallic shell, in contact with the outer conductive layer, a layer of strips that swell when exposed to moisture is arranged in an open cross lay. 2. Energy cable according to claim 1, characterized in that the closed metallic sheath is a lead or aluminum sheath. 3. Power cable according to claim 1, characterized in that the closed metallic sheath consists of a tube shaped, longitudinally welded, optionally corrugated, metal strip, for. B. made of copper or aluminum. 4. Energy cable according to claim 1, 2 or 3, characterized in that the swellable tapes are in the form of fleeces into which the swellable material is incorporated. 130043/0072 5. Energy cable according to claim 4, characterized in that the swellable tapes consist of a multilayer nonwoven material based on plastic, the middle layer or layers of which are made up of swellable material or contain such. 6. Energy cable according to claim 4, characterized in that there are powdery source materials between the individual layers of the nonwoven material. 7. Power cable according to claim 1 or one of the following, characterized in that the swellable tapes also contain indicators for the moisture detection. 8. Power cable according to claim 1 or one of the following, characterized in that the swellable tapes are conductive. 130043/0072