cable serving

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electrics

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what is "serving " of a cable? i mean something which covers the utmost exterior part of it....
also there are some other definitions used in xlpe cables
1- binder
2-"extruded" pvc sheath (what is exactly extrusion with regards to cables)
3- semiconductor XLPE screen (what good will make a semiconductor in a cable?)

thanks in advance..
 
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electrics said:
what is "serving " of a cable? i mean something which covers the utmost exterior part of it....
also there are some other definitions used in xlpe cables
1- binder
2-"extruded" pvc sheath (what is exactly extrusion with regards to cables)
3- semiconductor XLPE screen (what good will make a semiconductor in a cable?)

thanks in advance..
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electrics said:
http://img705.imageshack.us/img705/2682/adszlbd.jpg
http://img151.imageshack.us/img151/9941/14779099.jpg
u can also tell me the meaning of "BEDDİNG"
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1. binder ? usually a ribbon shape of some material which is spirally wrapped around the items it is to contain and hold in place.

2. extruded ? go to the following webpage to get a basic understanding of plastics extrusion: http://en.wikipedia.org/wiki/Plastics_extrusion . A sheath or jacket is an extruded overcoat of [near] constant thickness. A serving is one that the coating is impregnated into gaps of the substrate (such as the gaps between the steel wire armor, embedding the wire in the coating) and accomplished in a one extruder process. A bedding is something similar to serving in that voids which make up non-round inner product are filled so that a [near] constant thickness overcoat can be applied and result in a [near] round result.

3. semiconductor insulation layer ? Not a great explanation but... "The purpose of these semiconductor layers is to influence the electric field strength within the insulation layer. Environmental moisture diffusing into the cable insulation can promote the development of harmful "electrochemical trees" which shorten the useful service life of the cable. In order to avoid the entry of water or water vapours through the outer coating to the cable conductor the outer coating preferably consists of metal or a metal sheet in combination with an outer layer of PE or PVC (layer coating). The avoidance of water intrusion is of particular significance, since intruded water accelerates the aging processes of the insulating materials of the cable made of cross-linked polyethylene and thus leads to an early damage or failure of the cable." Copied in part from: http://www.electronics-manufacturers.com/info/cables-and-connectors/high-voltage-cable.html
 
Smart $ said:
1. binder ? usually a ribbon shape of some material which is spirally wrapped around the items it is to contain and hold in place.

2. extruded ? go to the following webpage to get a basic understanding of plastics extrusion: http://en.wikipedia.org/wiki/Plastics_extrusion . A sheath or jacket is an extruded overcoat of [near] constant thickness. A serving is one that the coating is impregnated into gaps of the substrate (such as the gaps between the steel wire armor, embedding the wire in the coating) and accomplished in a one extruder process. A bedding is something similar to serving in that voids which make up non-round inner product are filled so that a [near] constant thickness overcoat can be applied and result in a [near] round result.

3. semiconductor insulation layer ? Not a great explanation but... "The purpose of these semiconductor layers is to influence the electric field strength within the insulation layer. Environmental moisture diffusing into the cable insulation can promote the development of harmful "electrochemical trees" which shorten the useful service life of the cable. In order to avoid the entry of water or water vapours through the outer coating to the cable conductor the outer coating preferably consists of metal or a metal sheet in combination with an outer layer of PE or PVC (layer coating). The avoidance of water intrusion is of particular significance, since intruded water accelerates the aging processes of the insulating materials of the cable made of cross-linked polyethylene and thus leads to an early damage or failure of the cable." Copied in part from: http://www.electronics-manufacturers.com/info/cables-and-connectors/high-voltage-cable.html
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excuse me sir, what is the relation between semiconductor property and aging?? İ Couldnt get it:((by the way the other explanations was wonderful indeed thanks )
 
electrics said:
excuse me sir, what is the relation between semiconductor property and aging?? İ Couldnt get it:((by the way the other explanations was wonderful indeed thanks )
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I don't understand the reasoning completely myself, and thus the reason for copying someone else's explanation. Feel free to google a better explanation and post a link to it ;)

FWIW, my google search term was, "What is the purpose of semiconductor wire insulation layer?" or something very similar.
 
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electrics said:
excuse me sir, what is the relation between semiconductor property and aging?? İ Couldnt get it:((by the way the other explanations was wonderful indeed thanks )
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When you have a stranded conductor each strand (1st attachment) has a field around it, all those fields will interact with each other causing high density flux areas causing more electrical stress on the insulation than if a single conductor was used (2nd attachment). The semiconductor layer evens out the stresses from the induvidual strands therfore increasing cable life.
 
Why semi-con on HV cables?

Why semi-con on HV cables?

At low voltages corona is not much of a concern.

On medium and high voltage cables, corona could eat into the insulation and lead to a failure. Wrapping the conductor with semi-con smooths out the high voltage stresses, reducing corona.

Semi-con is extruded over the conductor to fill in the gaps between the outer strands.

It is placed over the insulation and under the copper tape shield (screen) to smooth voltage stresses on the insulation.

Check out Okonite or Southwire cable websites for detailed info.
 
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