PVC, PE, XLPE, EPR are the typical insulation materials used for cables.
Following introduction of the insulation materials:
PVC (Polyvinyl Chloride) – is the most commonly used thermoplastic insulator for cables.
PVC is cheap, durable and widely available. However, the chlorine in PVC (a halogen) causes the production of thick, toxic, black smoke when burnt and can be a health hazard in areas where low smoke and toxicity are required (e.g. confined areas such as tunnels). Normal operating temperatures are typically between 75℃ and 105℃ (depending on PVC type). Temperature limits is 160℃ (<300mm2) and 140℃ (>300mm2).
PE (Polyethylene) – is part of a class of polymers called polyolefins. Polyethylene has lower dielectric losses than PVC and is sensitive to moisture under voltage stress (i.e. for high voltages only).
Thermosetting compounds are polymer resins that are irreversibly cured (e.g. by heat in the vulcanization process) to form a plastic or rubber:
XLPE (Cross-Linked Polyethylene) – has different polyethylene chains linked together (“Cross-linking”) which helps prevent the polymer from melting or separating at elevated temperatures. Therefore XLPE can be used for higher temperature applications. XLPE is characterized with higher dielectric losses than PE, but has better ageing characteristics and resistance to water treeing. Normal operating temperatures are typically between 90℃and 110℃. Temperature limit is 250℃.
EPR (Ethylene Propylene Rubber) – is a copolymer of ethylene and propylene, and commonly called an “elastomer”. EPR is more flexible than PE and XLPE, but has higher
dielectric losses than both. Normal operating temperatures are typically between 90℃ and 110℃. Temperature limit is 250℃