The two most common and effective types of insulation for modern underground cables are Cross-linked Polyethylene (XLPE) and Ethylene Propylene Rubber (EPR).

• XLPE (Cross-linked Polyethylene): This is a thermosetting material that has become the industry standard for medium and high-voltage cables. It's known for its superior electrical properties, high resistance to heat and chemicals, and long service life. Its primary advantage is its low dielectric loss, which means less energy is wasted as heat during transmission, making it highly efficient.

• EPR (Ethylene Propylene Rubber): EPR is a synthetic rubber compound prized for its excellent flexibility and resistance to moisture. It is often preferred for applications that require navigating tight bends or for systems where flexibility is a key installation factor. EPR insulation is less susceptible to "water treeing" (a form of moisture-induced insulation degradation) compared to older XLPE materials, making it a reliable choice for wet environments.

While XLPE has lower dielectric losses and is often more cost-effective for long, straight runs, EPR's flexibility and moisture resistance make it ideal for complex installations in demanding conditions.