Commercial Subsea HVDC vs. HVAC Cable Sizer
Evaluate offshore wind export cables, island microgrids, and cross-border interconnectors. Model charging reactive capacitance ($Q_c$), conductor ohmic losses ($I^2R$), shunt reactor requirements, and Voltage Source Converter (VSC-HVDC) break-even distance.
⚙️ Transmission Link Parameters
💵 Converter Stations & Marine CapEx
Full Life-Cycle Transmission Comparison (65 km Route) CIGRE B1 MODEL
| System Parameter | HVAC 3-Core Subsea | VSC-HVDC Bipole |
|---|---|---|
| Reactive Charging Current Loss: | 224 MVAR | 0 MVAR (DC = Zero Charging) |
| Total Conductor I²R Losses: | 34.2 MW (4.28%) | 18.1 MW (2.26%) |
| Total Subsea Cable CapEx: | $182.0 Million | $136.5 Million |
| Substations & Converters: | $45.0 Million (Shunt) | $280.0 Million (VSC) |
| Total Initial Project CapEx: | $227.0 Million | $416.5 Million |
| 25-Year Loss Penalty Cost: | $441.2 Million | $233.5 Million |
Subsea Transmission Physics & Critical Cable Limits
Subsea AC cables have high capacitance ($C \approx 0.2\ \mu\text{F/km}$) because the insulation is thin and water acts as an infinite ground plane. At distances beyond $50\text{–}60\text{ km}$, continuous charging current fills the conductor's thermal ampacity limit, leaving zero capacity to transmit real MW without massive onshore/offshore shunt reactors. HVDC operates at zero frequency ($f=0$), eliminating reactive charging and dielectric losses entirely.