The centre of a conductor has low-frequency signals, while the conductor's surface has high frequency signals. As a result, high frequency signals are constrained to flow in a smaller area of conductors than low-frequency conductors. For this reason, effective China Electric Cable Wire resistance is important in high frequency signals compared to low-frequency signals. Furthermore, cable losses are frequency dependent, with high frequencies experiencing the most loss. Nevertheless, the conductor resistance increases because of the 'skin effect' happening at around 20 kHz.
Types of insulation
An insulator is a material that is resistant to the flow of electric current (a non-conductive material). It helps to resist the leakage of the electric current, preventing it from contacting other conductors. This helps to preserve the integrity of the wires against environmental threats like heat and water. Therefore, the effectiveness and safety of wires and cables depend on their insulation. The common types of cable insulators include:
Plastics
The plastic insulators include PVC (Polyvinyl Chloride), SR-PVC (Semi-Rigid PVC), Plenum PVC (Plenum Polyvinyl Chloride), PE (Polyethylene), PP (Polypropylene), PUR (Polyurethane), CPE (Chlorinated Polyethylene) and Nylon.
Rubber
The rubber insulators include TPR (Thermoplastic Rubber), Polychloroprene (Neoprene), SBR (Styrene Butadiene Rubber), Silicone, Fiberglass, EPR (Ethylene Propylene Rubber), Rubber, CSPE (Chlorosulfonated Polyethylene) and EPDM (Ethylene Propylene Diene Monomer).
Fluoropolymers
The Fluoropolymer insulators include PFA, PTFE (Polytetrafluoroethylene), FEP (Fluorinated Ethylene Propylene), ECTFE Halar, ETFE Tefzel, PVDF (Polyvinylidene Fluoride), TPE (Thermoplastic Elastomers).
Each of these types of insulators has typical uses, pros and cons. Furthermore, the degree of insulation is influenced by several factors such as the maximum voltage of the copper cable and the temperatures the wire/cable has to withstand. Typically, this affects the type and quality of insulation, sheathings, coverings and insulating sleeves.
Importance of wire & cable insulation
The electrical properties in wires and cables are influenced significantly by the insulation. As a result, high-frequency communication cables would require Polyethylene (PE) insulation because the attenuation and capacitance are minimal when this type of insulation is used. Furthermore, factors such as heat & flame resistance, mechanical toughness, moisture resistance, resistance to ionization, usage life and flexibility determine the insulation.
When you choose the type of cables to use, it is important to bear in mind insulation and shielding factors. Insulation and shielding when combined, can offer effective protection, although they both play an independent role in coaxial cable functioning. While the insulation does not offer protection against electromagnetic interference, it helps the cable to work properly by maintaining the centre conductor and shielding materials from coming into contact with it. On the other hand, cable shielding acts like an electromagnetic energy interceptor that prevents electrical interference from travelling to the centre of the cable and disrupting data signals.