Thesis title: IRIS Green Superconducting Line (GSL)
This thesis investigates the IRIS Green Superconducting Line (GSL) through COMSOL simulations and analytical calculations, with the aim of characterising the line’s physical behaviour, its power consumption and its potential applications. The GSL is designed to carry 1 GW (with 25 kV and 40 kA in direct current), employs magnesium diboride (MgB2), chosen for its higher Tc (permitting operation with helium gas at 20 K and the possibility of liquid hydrogen cooling), the feasibility of round-wire manufacture, and lower production cost compared with HTS tapes.
Magnetic analysis shows peak self-fields of B = 0.58 T for the single-cable (Salerno test station facility) configuration and B = 0.64 T for the two-cable operational arrangement; the 400 mT safety threshold is met at the cryostat boundary in the double-cable case and at approximately 0.5 m from the cryostat in the single-cable case. Mechanical analysis yields a maximum strand strain ε ≃ 0.15%, below the critical value εcrit = 0.35%, so that Ic is effectively unaffected by the predicted deformation. The critical-current study quantifies fault tolerance: the cable tolerates up to five fully broken petals while retaining a per-strand current margin ∆I ≈ 120.71 A and a temperature margin ∆T = 2.37 K; operation is still possible with up to 78 broken strands, albeit with very small margins (∆I = 1.7 A, ∆T = 0.04 K), which defines an operational damage limit.
Transition from superconducting to normal (resistive) state analysis indicates that the transition of a small portion of a single-strand produces a terminal-voltage change of order 0.73 nV and that 78 transit strands produce 0.24 μV; these levels are below typical voltage-tap sensitivity, so protection should rely primarily on local temperature-rise detection.
The power-consumption study shows how continuous cryogenic refrigeration dominates energy use for long runs, potentially offsetting Joule-loss savings; nevertheless, advantages include the possibility of a dual electrical/chemical energy vector with liquid hydrogen, high current at low voltage, reduced land take, and reuse of existing tunnels with higher power density. The GSL modularity allows downscaling for smaller power requirement (e.g. a single-petal configuration for ∼ 2 MW).
Overall, the IRIS GSL is a promising alternative to conventional HVDC lines in applications requiring very high currents and power, where cryogenics are available or where compact routing constraints favour superconducting links.