Types of Insulation and Sheath in Cables – A Professional Guide to Power and Control Cables
Introduction: Conductor Insulation vs. Outer Sheath
In cables used for power and control transmission, there are two main protective layers:
- Insulation – A layer that surrounds each conductor individually, preventing electrical contact between conductors and between the conductors and their surroundings. Insulation materials are chosen based on electrical, thermal, and long-term durability properties.
- Outer Sheath (Jacket) – A layer that covers the entire cable structure (insulated conductors, fillers, shielding, etc.), protecting it from mechanical damage, environmental conditions, moisture, oils, radiation, and fire. Sheath materials are selected according to physical and environmental demands.
Distinguishing between these two roles is essential in cable engineering – each layer must be adapted to its specific purpose and the environmental conditions in which the cable operates.
Chapter 1: Types of Conductor Insulation (for Power and Control Cables)
- PVC (Polyvinyl Chloride)
- Operating temperature: up to 70°C (sometimes up to 90°C depending on manufacturer formulations)
- Advantages: Flexible, inexpensive, easy to process, water-, oil-, and chemical-resistant
- Disadvantages: Relatively low operating temperature, emits toxic gases when burned
- Applications: Control cables, low-voltage power cables, indoor systems in industry and buildings
- PE (Polyethylene)
- Operating temperature: up to 70°C
- Advantages: Low dielectric constant – excellent electrical insulation, highly resistant to moisture and chemicals, lightweight and cheap
- Disadvantages: UV-sensitive (unless carbon black is added), relatively flammable, less flexible
- Applications: Underground cables, outdoor installations, high environmental resistance applications where flexibility is not critical
- XLPE (Cross-Linked Polyethylene)
- Operating temperature: up to 90°C
- Advantages: High thermal resistance, excellent electrical insulation properties, water- and chemical-resistant
- Disadvantages: Less flexible than PVC, more expensive
- Applications: Low- and medium-voltage power cables, industrial electrical systems, feeder cables
- EPR (Ethylene Propylene Rubber)
- Operating temperature: up to 60°C (up to 90°C depending on manufacturer formulations)
- Advantages: High flexibility, maintains electrical properties in extreme temperatures, excellent resistance to moisture, oils, and chemicals
- Disadvantages: Relatively expensive, less common in general applications
- Applications: Portable cables, heavy industry, temporary power in building sites
- LSZH (Low Smoke Zero Halogen)
- Operating temperature: 90°C
- Advantages: Does not emit thick smoke or toxic gases in case of fire – increases safety
- Disadvantages: Stiffer, lower mechanical durability than PVC, more expensive
- Applications: Power and control cables in public buildings, electrical panels, closed areas with high people concentration
Chapter 2: Types of Outer Sheath
- PVC (Polyvinyl Chloride)
- Operating temperature: up to 70°C (sometimes up to 90°C depending on manufacturer formulations)
- Advantages: Flexible, inexpensive, easy to process, water-, oil-, and chemical-resistant
- Disadvantages: Relatively low operating temperature, emits toxic gases when burned
- Applications: Control cables, low-voltage power cables, indoor systems in industry and buildings
- LSZH (Low Smoke Zero Halogen)
- Operating temperature: up to 90°C
- Advantages: Fire-resistant, emits no halogens or thick smoke – enhances fire safety
- Disadvantages: Less flexible, moderate mechanical durability, higher cost
- Applications: Public buildings, train stations, tunnels, hospitals
- PE (Polyethylene)
- Operating temperature: up to 70°C
- Advantages: High mechanical strength, resistant to moisture, chemicals, and outdoor environments
- Disadvantages: Flammable (without additives), UV-sensitive if not black
- Applications: Medium-voltage cables, outdoor installations, underground infrastructure, direct burial
- PUR (Polyurethane)
- Operating temperature: up to 90°C
- Advantages: Excellent flexibility, outstanding resistance to abrasion, oils, and fuels
- Disadvantages: Sensitive to prolonged heat, relatively expensive
- Applications: Temporary power on construction sites, industrial machinery, portable cables, conveyors
- Rubber / CPE / PCP
- Operating temperature: up to 90°C
- Advantages: High mechanical durability, excellent flexibility, performs well in harsh outdoor conditions
- Disadvantages: Heavy, expensive, less suited for delicate environments
- Applications: Construction sites, temporary cables, kitchens, mobile electrical equipment
Table: Common Combinations of Insulation and Sheath in Cables
Conductor Insulation | Outer Sheath | Key Characteristics | Common Applications |
PVC | PVC | Inexpensive, flexible, suited for indoors | General control and power cables |
XLPE | PE | High moisture resistance, lightweight, cheap | Outdoor and underground systems |
XLPE | PVC | Heat-resistant insulation, basic sheath | Standard industrial systems |
XLPE | LSZH | Electrical performance + fire safety | Electrical panels, public buildings |
EPR | PUR | High endurance in demanding conditions | High thermal + abrasion resistance |
EPR | Rubber | Extremely durable in harsh environments | Very rugged cable combination |
LSZH | LSZH | Full fire-safety (halogen-free) | Full fire-safety (halogen-free) |
Conclusion
When designing an electrical or control system, it is important not only to choose the conductor cross-section and operating voltage, but also the appropriate combination of insulation and sheath materials, based on:
Thermal and electrical needs (for insulation)
Mechanical, environmental, and safety requirements (for the sheath)
A solid understanding of the available materials contributes to the cable’s reliability, durability, and higher safety level.