As per IEC in medium voltage cables, the insulation screen shall consist of a non-metallic semi-conducting layer in combination with a metallic layer. The non-metallic layer shall be extruded directly upon the insulation of each core and consist of
either a bonded or strippable semi-conducting compound. A layer of semi-conducting tape or compound may then be applied over the individual cores or the core assembly and then metallic non magnetic layer.
My question is: Do we need a additional layer of semi conducting tape if a layer of extruded semi conducting compound is applied over insulation. Insulation shield consists of two parts non metallic semi conducting compound + metallic non magnetic. So a semi conducting tape over semi conducting compound looks like repetition.
Semi conducting tape is required over semi conducting layer if the layer is stripable because in case semi conducting layer is stripable then something is required to hold the layer sticking to insulation. However if the cable is manufactured by triple extrusion, then XLPE insulation, conductor screening and insulation screening are all extruded in one operation by a special process called Triple Extrusion i.e. all three layers in one operation. This process ensures perfect bonding of inner and outer shielding with insulation. The formation of voids/protrusions at the interface of the semiconducting layer and insulation, too is eliminated in the triple extrusion process. Hence additional semi conducting tape for binding semi conducting layer with insulation is not required.
Please share your view if additional semi conducting tape is optional or mandatory? If optional then is there any other reason apart from what i have analysed above?
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Construction of Medium Voltage Cables
Re: Construction of Medium Voltage Cables
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