Wire insulation dielectric breakdown

Electrical Communications Low dielectric constant High volume/surface resistivity High dielectric breakdown voltage Flame resistance, thermal stability Wire and cable insulation, connectors... 

Most plastics are dielectrics or insulators (poor conductors of electricity) and resist the flow of a current. This is one of the most useful properties of plastics and makes much of our modern society possible through the use of plastics as wire coatings, switches and other electrical and electronic products. Despite this, dielectric breakdown can occur at sufficiently high voltages to give current transmission and possible mechanical damage to the plastic. 

Electrical Communications Low Dielectric Constant High Volume/Surface Resistivity High Dielectric Breakdown Voltage Flame Resistance, Thermal Stability Wire and Cable Insulation, Connectors... 

The exterior of foamed wire insulation can be coated with a solid layer (jacket) of ETFE or ECTFE for wires used in telecommunications and fiber optics. This arrangement allows the foamed perfluoro-polymer to provide good electrical properties while the skin layer supplies sufficient mechanical properties. A foamed FEP wire insulation (eore), with a thickness of 0.5 mm, was coatedl with 51 pm of an ETFE jacket it had a dielectric constant of 1.64 and dielectric breakdown strength of 26.6 kV/mm. 

Wires have been insulatedl and jacketed with ETFE and ECTFE resulting in excellent electrical and mechanical properties. A 24-gauge wire was insulated with an ETFE jacket and core. The jacket was solid (25 pm thick) and covered a foam insulation core (0.127 pm). This insulation had 45% void content and a dielectric breakdown voltage of 20 kV/mm. 

Eleetrieal properties of biodegradable polylactic acid films were measured and compared with those of erosslinked polyetlylene (XLPE) cimently used as insulation for cables and electric wire [10]. The volume resistivity, dielectric constant and dielectric loss tangent of PLLA were found to be almost the same as those of XLPE. However, the impulse breakdown strength of PLLA was 1.3 times that of XLPE. 

The wide use of polymers in the electrical industry arises from their excellent electrical insulation and dielectric isolation properties. However, these are dependent upon the polymer permeation properties. For instance, the sheathing of cables and wires is sensitive to the presence of water in the polymer. It has been shown that the most common form of insulation breakdown arises from electrochemical treeing. This arises from the simultaneous effects of an electric field and moisture present in the shielding, either initially present or by permeation. 

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