Frankfurt (Germany), 6-9 June 2011 Alex Geschiere Liandon member of Alliander Alex Geschiere – Netherlands – Session 1 – 1256 Superconducting cables A breakthrough in development

Frankfurt (Germany), 6-9 June 2011 Alex Geschiere – Netherlands – Session 1 – Paper 1256 Triax cable

Frankfurt (Germany), 6-9 June 2011 Alex Geschiere – Netherlands – Session 1 – Paper 1256 Cryostat design Stainless steel inner tube Vacuum insulation with multy layer insulation (MLI) Stainless steel outer tube Vacuum: sealed for life. Residual gasses will be absorbed by getter material

Frankfurt (Germany), 6-9 June 2011 Alex Geschiere – Netherlands – Session 1 – Paper 1256 Smart electrical behaviour very low Z high Z very low Z high Z very low Z high Z Low impedance during normal operation Low energy losses and Low impedance Low energy losses Stable voltage profile High impedance at increasing current Limiting of short circuit High impedance Limiting of short circuit currents

Frankfurt (Germany), 6-9 June 2011 Alex Geschiere – Netherlands – Session 1 – Paper 1256 Temperature profile Challenge: Limit the difference between maximum and minimum temperature in long length cables

Frankfurt (Germany), 6-9 June 2011 Alex Geschiere – Netherlands – Session 1 – Paper 1256 Challenge Fault Current Limiting High impedance at increasing current Limiting of short circuit high Z High impedance Limiting of short circuit currents Challenge: Resistive limiting will cause a significant amount of additional heat. Optimize heat management during faults.

Frankfurt (Germany), 6-9 June 2011 Alex Geschiere – Netherlands – Session 1 – Paper 1256 Breakthrough in cryostat design Heat leakage from 1.5 W/m to 0.5 W/m Reduced heat leakage in cryostat: - optimize MLI and spacers - mix of straight/rigid sections and corrugated/flexible sections

Frankfurt (Germany), 6-9 June 2011 Alex Geschiere – Netherlands – Session 1 – Paper 1256 Low friction design Low friction of Nitrogen mass flow Test of a 45 m low friction cryostat. A mass flow of 0.3 kg/s resulted in a pressure drop of only 5 mbar.

Frankfurt (Germany), 6-9 June 2011 Alex Geschiere – Netherlands – Session 1 – Paper 1256 Reduced AC losses AC losses from 1.5 W/m/phase to 0.2 W/m/phase at 3000 Amps Reduction of gaps between tapes Narrow HTS tapes will fit the conductor shape better Special low loss 2G-tapes

Frankfurt (Germany), 6-9 June 2011 Alex Geschiere – Netherlands – Session 1 – Paper 1256 Test of reduced AC losses Result form test: AC losses at 3000 Amps of 0.11 W/m/phase (goal 0.2 W/m/phase) Test of three different constructions/tape designs. Huge impact on AC losses.

Frankfurt (Germany), 6-9 June 2011  Significant improvement in development of HTS cables possible in a two years development program.  Results are proved by several tests. Alex Geschiere – Netherlands – Session 1 – Paper 1256