Insulation is PROVIDED to electrically isolate the individual cores from one another. The applied insulation must perform adequately in the specified temperature range, and its dielectric strength should be sufficient to sustain the electrical STRESSES.

Cable insulation should have:

• High Dielectric Strength
• Low dielectric constant
• Good Mechanical properties
• Resistance to Ageing
• High temperature withstandability

Insulating materials are classified as thermoplastic or thermoset. Thermoplastic materials lose their form upon heating. Thermoset materials MAINTAIN their form in spite of heating. Various types of insulating materials used are : PVC, XLPE, Rubber, Impregnated Paper, etc.

Polyvinyl Chloride (PVC):

Polyvinyl chloride (PVC or vinyl) is a thermoplastic. PVC compound is the standard insulation for cables rated at 11000 volts or less & sheathing of entire range of cables. PVC compound is a mixture of PVC resin, plasticizer, fillers, stabilizers, lubricant, pigment. The quantity and type of each ingredient determines the properties. A broad range of electrical, physical and chemical properties is possible. PVC has good electrical properties. It is tough and resistant to flame, moisture, and abrasion. Resistance to ozone, acids, alkalis, alcohol, and most SOLVENTS is also adequate. PVC can be made resistant to oils and gasoline.

PVC has the disadvantage of having a high dielectric constant and dissipation factor. Also plasticizer loss can cause hardening and cracking.

Crosslinked Polyethylene:

Crosslinked polyethylene (XLPE) is a thermoset. It is produced by compounding PE (polyethylene) with a crosslinking agent, like organic peroxide. The molecules of polyethylene are “crosslinked”, forming an interconnected network. The terms “CURED” and “vulcanised” are also used for “crosslinked“.

Elastomer:

Elastomeric material are used for insulation and for sheaths. They are applied mainly where the product has to be particular flexible. A wide range of elastomers is nowadays available to the cable industry. This makes possible the manufacture of compounds with specific properties, such as abrasion and oil resistance, weather and heat resistance and flame resistance, combined with good overall electrical and mechanical charateristics.

The classical elastomeric material, natural rubber, has declined in significance in recent years. In its place, the synthetic elastomers produced by the co-polymerisation of ethylene and propylene, are constantly finding new areas of application in cable engineering. This co-polymers, are generally known as EPR.

Rubber was the first insulant to be used in Electric cable manufacture but gave way to other insulants like paper, PVC, XLPE etc. Rubber is still considered the preferred insulation for flexible cables and cables where very small bending diameter is desired.

Paper:

Paper tapes of specific thickness and suitable widths are lapped around the conductor. The thickness of built up insulation depends on the rated voltage of the cable. Paper insulated cores are dried and impregnated using mass impregnating non-draining compound.

Insulation is provided to electrically isolate the individual cores from one another. The applied insulation must perform adequately in the specified temperature range, and its dielectric strength should be sufficient to sustain the electrical stresses.

Cable insulation should have:

Insulating materials are classified as thermoplastic or thermoset. Thermoplastic materials lose their form upon heating. Thermoset materials maintain their form in spite of heating. Various types of insulating materials used are : PVC, XLPE, Rubber, Impregnated Paper, etc.

Polyvinyl Chloride (PVC):

Polyvinyl chloride (PVC or vinyl) is a thermoplastic. PVC compound is the standard insulation for cables rated at 11000 volts or less & sheathing of entire range of cables. PVC compound is a mixture of PVC resin, plasticizer, fillers, stabilizers, lubricant, pigment. The quantity and type of each ingredient determines the properties. A broad range of electrical, physical and chemical properties is possible. PVC has good electrical properties. It is tough and resistant to flame, moisture, and abrasion. Resistance to ozone, acids, alkalis, alcohol, and most solvents is also adequate. PVC can be made resistant to oils and gasoline.

PVC has the disadvantage of having a high dielectric constant and dissipation factor. Also plasticizer loss can cause hardening and cracking.

Crosslinked Polyethylene:

Crosslinked polyethylene (XLPE) is a thermoset. It is produced by compounding PE (polyethylene) with a crosslinking agent, like organic peroxide. The molecules of polyethylene are “crosslinked”, forming an interconnected network. The terms “cured” and “vulcanised” are also used for “crosslinked“.

Elastomer:

Elastomeric material are used for insulation and for sheaths. They are applied mainly where the product has to be particular flexible. A wide range of elastomers is nowadays available to the cable industry. This makes possible the manufacture of compounds with specific properties, such as abrasion and oil resistance, weather and heat resistance and flame resistance, combined with good overall electrical and mechanical charateristics.

The classical elastomeric material, natural rubber, has declined in significance in recent years. In its place, the synthetic elastomers produced by the co-polymerisation of ethylene and propylene, are constantly finding new areas of application in cable engineering. This co-polymers, are generally known as EPR.

Rubber was the first insulant to be used in Electric cable manufacture but gave way to other insulants like paper, PVC, XLPE etc. Rubber is still considered the preferred insulation for flexible cables and cables where very small bending diameter is desired.

Paper:

Paper tapes of specific thickness and suitable widths are lapped around the conductor. The thickness of built up insulation depends on the rated voltage of the cable. Paper insulated cores are dried and impregnated using mass impregnating non-draining compound.