Jk. Sykulski et al., Prospects for large high-temperature superconducting power transformers: conclusions from a design study, IEE P-EL PO, 146(1), 1999, pp. 41-52
A design feasibility study has been conducted for a 240MVA high-temperature
superconducting grid auto-transformer. Conclusions are relevant to superco
nducting power transformers in general. It is argued that economic benefits
may be predicted, subject to assumptions about achievable conductor proper
ties, costs of components and power system operating requirements. Liquid n
itrogen cryogenics is relatively cheap and simple, and refrigeration power
demand is reduced by a factor of the order of 20 compared to the low-temper
ature case. Attention is drawn to the importance of AC losses in the superc
onductor and the difficulty of keeping these sufficiently low. Various tech
nical problem areas, and their likely influence on the overall design conce
pt, are reviewed. Three particularly important influences are identified: i
nsulating properties of liquid nitrogen coolant, required transformer perfo
rmance in the through fault condition, and mechanical strength to withstand
electromagnetic forces. Design proposals are detailed, and recommendations
made for future development of high-temperature superconductors for power
applications.