From the shore, offshore wind turbines look like a row of distant white windmills. But when the blades start turning, the electricity they make does not “fly” back to the city—and certainly not with one cable running from every turbine to the land.
The real path is hidden inside the tower, the offshore substation, and the seabed:
Collect → Step up → Cross the sea → Landfall → Onshore grid
How far the sea is, and how large the wind farm is, decides whether the link uses AC or DC.
1. Collecting Power From Many Turbines
Wind pushes the blades, the drive train and generator convert mechanical energy into electricity. Different turbine models vary in design, but the output usually passes through converters and small step-up units to reach the collection voltage the farm needs.
Multiple turbines are then linked by array cables in strings, feeding into the offshore substation.
Typical modern array voltages:
- Legacy farms: 33 kV AC
- New large farms: 66 kV AC
- Future ultra-large farms: 132 kV array systems in planning
Raising array voltage reduces current, cuts resistive loss, and lets each cable string serve more turbines.
2. The Offshore Substation: A Power Hub at Sea
Think of the offshore substation as a “power transfer station” built on the water.
It gathers the distributed output from all turbine strings, then steps the voltage up—typically to 132 kV, 220 kV, or 345 kV. For the same power, higher voltage means lower current, which reduces heat loss in the export cable.
Only after this stage is the power ready for the cross-sea journey.
3. Subsea Export Cables Are Not “Wires Soaked in Water”
An export cable is a engineered multi-layer system:
|
Layer |
Function |
|---|---|
|
Conductor |
Carries current (copper or aluminum) |
|
XLPE insulation |
Withstands high voltage, marine thermal cycles |
|
Water barrier |
Blocks longitudinal water penetration |
|
Armor (SWA/STA) |
Resists tension, abrasion, anchors, fishing gear |
|
Outer sheath |
Anti-corrosion, anti-biofouling, UV resistant |
Cable-lay vessels place the cable on the seabed. Critical sections are buried 1–3 m deep or protected with rock dumping to reduce damage from anchors and trawl gear.
After landfall, the cable enters an onshore substation and feeds the regional load center.
4. HVAC or HVDC? Distance Decides
Near shore, moderate capacity → HVAC
- Simple, mature, grid-friendly
- But AC submarine cables act like long capacitors
- Charging current grows with length
- Practical economic limit: ~80–100 km without heavy reactive compensation
Far shore, large capacity → HVDC (VSC/flexible DC)
- Offshore converter: AC → DC
- DC export cable to shore
- Onshore converter: DC → AC grid
- No capacitive charging penalty
- Common voltages: ±320 kV to ±525 kV
- Best for 100+ km routes and multi-terminal offshore grids
The converter stations add cost, but they remove the distance limitation and give better grid control.
5. Why Offshore Transmission Is Hard
The challenge is not only “the sea is wide.”
- Salt spray, humidity, and corrosion
- Typhoons, waves, and tidal movement
- Seabed mobility and burial conditions
- Anchor strikes and fishing-gear interaction
- Fault location and repair are slow—vessels, weather windows, jointing, reburial
That is why route selection, redundancy, online monitoring (DTS/DAS via integrated fiber), and maintenance vessels must be planned before construction starts.
Subsea cables are often only ~8–10% of CAPEX, but drive the majority of unplanned downtime and insurance claims.
6. Where Minfeng Cable Fits in the Chain
While full HVDC export cables are a specialist subsea scope, the onshore and platform-side electrical system still depends on rugged, standards-compliant cabling:
- XLPE insulated SWA/STA armored power cables (up to 35 kV) for collection, platform, and onshore tie-in
- LSZH fire-resistant cables with 3-hour circuit integrity for evacuation, control, and safety systems
- ACSR and 110 kV class conductors for grid connection and step-up interfaces
- 1500 V DC renewable cables for hybrid wind-solar platforms
- Built to IEC, TÜV, CCC, and project-specific specs
For offshore-adjacent projects, the rule is simple: the cable is the most exposed asset in the whole system. Armor, insulation, and certification are not optional.
Summary
Offshore wind does not reach the city by magic. It moves through:
Turbine → 66 kV array cable → offshore substation → HVAC or HVDC export → seabed → onshore grid
The further the farm, the more the cable—not the turbine—decides project reliability and cost.
For cable specs engineered for marine, industrial, and grid-edge environments, visit:
