Rated Voltage 220 kV XLPE Insulated (Flame Retardant) Power Cable

Executive Standards
The design, manufacture, and testing of the product strictly comply with national standards and enterprise-specific technical specifications:
- GB/T 18890-2015: "Power cables with cross-linked polyethylene insulation and their accessories for rated voltage of 220 kV (Um = 252 kV)" (core national execution standard).
- Q/320481SS365-2022: Enterprise-specific technical standard formulated for cables with flame retardant characteristics.
- GB/T 19666: General rules for flame retardant and fire-resistant wires and cables.

Model Code Definitions
The model accurately reflects the cable's material and protective layer construction through specific combinations:
- YJ: Cross-linked polyethylene (XLPE) insulation.
- LW: Metal sheath, typically a corrugated aluminium sheath, providing outstanding radial water resistance and very high mechanical impact strength.
- 02 / 03: Outer sheath material (02 – polyvinyl chloride PVC; 03 – polyethylene PE).
- -Z: Longitudinal water blocking construction, preventing water from penetrating longitudinally along the conductor or inside the metal sheath.
- Z(A/B/C): Flame retardant class designation (Class A, Class B, or Class C flame retardant).

Product Specification Range
The cable adopts a single-core construction, with specification design comprehensively covering requirements from urban high-voltage distribution to high-power backbone network transmission:
- Rated voltage (U₀/U): 127/220 kV (maximum voltage Um = 252 kV).
- Nominal conductor cross-sections:
  - Conventional specifications: 400, 500, 630, 800 (round conductor) mm².
  - Large cross-section specifications: 800 (segmented), 1000, 1200, 1400, 1600, 1800, 2000, 2200, 2500 mm².
  - Note: For specifications of 800 mm² and above, a segmented conductor construction is recommended. This effectively reduces skin effect and proximity effect, lowering temperature rise and losses during high-current transmission.

Core Technical Parameters
1. Temperature characteristics: The maximum continuous permissible conductor operating temperature is 90 °C; during a short circuit (max. 5 s), the maximum conductor temperature is 250 °C.
2. Partial discharge performance: Under stringent test voltages, the partial discharge magnitude is required to be very low (typically ≤ 5 pC at 1.5 U₀), ensuring long-term operational life under extra-high voltage electric fields.
3. Flame retardant characteristics: The flame retardant type can pass the bunched cable flame test specified in GB/T 18380, effectively inhibiting smoke spread and fire propagation during a fire.

Product Structural Characteristics
- Ultra-clean insulation system: Ultra-clean XLPE material and a fully enclosed triple-layer co-extrusion process are used to prevent impurities and air gaps, ensuring high purity of the insulation layer and uniform electric field distribution.
- Hermetically sealed aluminium sheath: The corrugated aluminium sheath not only provides 100% radial water blocking but also has a strong ability to withstand short-circuit current, and can serve as a system return conductor and earthing loop.
- Composite waterproof design: Combining the metal sheath, semi-conductive water blocking tape, and longitudinal water blocking compound forms a comprehensive watertight structure, thoroughly preventing insulation breakdown caused by the "water tree" phenomenon.

Applicable Scenarios
- Urban power grid hubs: Underground 220 kV backbone transmission networks in core areas of large central cities and megacities.
- Outgoing lines from major power plants: Outgoing lines from step-up substations of large nuclear power plants, very large thermal power plants, and water conservancy hubs.
- Industrial load mains: Dedicated high-voltage systems for heavy chemical industry bases, very large metallurgical parks, and other facilities with massive power demands.

Selection and Installation Recommendations
- Earthing protection design: Because the voltage of 220 kV lines is very high, the earthing method of the metal sheath (such as cross-bonding, single-point earthing with a protective device, etc.) must be carefully designed according to line length to eliminate losses caused by induced voltage.
- Bending radius control: Extra-high voltage cables are large in volume and very heavy. Dedicated pay-off racks and bending rollers must be used during installation, and the minimum bending radius is generally not less than 20 times the overall cable diameter.
- Condition monitoring solutions: For critical 220 kV lines, it is recommended to install distributed fibre optic temperature measurement systems and partial discharge online monitoring devices to achieve real-time monitoring and early warning for the power artery.