Single vs Dual power cable insulation 1

[sranwar]

Can anybody tell me what is the difference between single layer Medium Voltage cable insulation and the dual layer MV cable insulation? And which type is better/ more utilized in the power industry?

 

[davidbeach]

Why don't you give examples of what you mean by single layer and dual layer? Dual layer may mean different things to different people.

 

[sranwar]

Well sometimes cable mfg have two layers of insulation, inner layer of linear low density PE and an outer layer of High density PE probably for flexibility and durability. This not always practiced. So my question is that is this a thing of the past? Is it not necessary anymore because of better compounds today?

I need to know this to decide wheather to put in cable specs or not. Just need some explanation why this be necessary. Thanks

 

[magoo2]

The single versus 2-layer insulation is a design variation with low voltage insulation (600 V class). I've never heard of it being mentioned with regard to medium voltage cable.

 

[sranwar]

ok lets say for 600 V application, would a single layer be as good as a dual layer? what is the difference ? Is the newer applications in industry are moving away from dual layer? thanks

 

[magoo2]

The two layer has become a standard since the 80s. It has a high density layer over a low density layer. The high density layer makes it more abuse resistant (mechanical protection). If it were a single layer, high density design, it would be too stiff.

You summarized it correctly in that the 2-layer design is used for the combination of durability and flexibility. It has become the industry standard. I don't believe anyone buys the single layer design anymore.

 

[7anoter4]

I don't think the use of low density PE is still permitted as this material is prohibited as carcinogenic.
See:

http://www.chemwide.com/productinfo/certi/09ldpe/03msds/MB9300.pdf

High density PE is thermoplastic PE and I think is not fire retardant at all. Usually High Density PE is still used for Underground High Voltage cables [I think Pirelli still does some time]as insulation.
The upper [outer] layer it is actually only a jacket and has poor insulation properties but has to be mechanically resistant as magoo2 already said,in order to be able to be pulled through conduits and ducts, for instance. If the cable is PVC made-for example- then the inner compound will be insulation and with good electrical properties and the jacket a good mechanical properties-so it is not the same compound.
Medium and High Voltage cables are provided also with a jacket but is not directly in contact with the insulation since they are many other layers-semiconducting layers and metallic shields and fillers and water barrier and other.

 

[waross]

I see a headache coming for the poor contractor who has to work to your spec. Pick an industry standard cable that you like and spec it by industry standard designations. Phone your local supplier and ask what cables he stocks that will serve your application. Try several suppliers. Spec a standard cable, please.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[sranwar]

Cable is for UG application and is important that it is flexible enough for it to be passed underground. I was just trying to figure out if thats what everybody else is doing. using dual insulated cable that is.

But I hear you waross.

Thank you all though. I will follow the KISS principle.
( Keep It Simple Stupid )