High Voltage in Superconducting Power Equipment — Prospects and Limits
Superconductivity offers a unique feature for heavy current flow, and strong magnetic fields. However, the Poynting vector which is the cross product of the magnetic field and the electrical stress is comprised within the insulating space. This fact enlightens the significance of a matching insulation design. Some insulators show fascinating intrinsic properties and may suggest the use of high dielectric stress, but the variety of applicable insulants is limited at low temperatures. Solids suffer from the thermomechanical mismatch against conductors. Cryogenic liquids can easily be vaporized unless a high pressure is maintained. Vacuum may be affected by leakage, and by strong magnetic fields. No “Superdielectric” does exist in practice. Hence, applicable dielectric stress may be as usual in conventional electrotechnique, but very high voltages are hard to apply. Medium high voltages seems to be much more adequate. Quite on the contrary of a quench which may be handled via a controlled discharge, a failure of the insulation system normally ends in a disaster. The design challenge is to guarantee an almost zero failure risk without relying on an excessive safety margin.
KeywordsBreakdown Voltage Partial Discharge Dielectric Strength Failure Risk Power Equipment
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- 1.A.D. Appleton, An introduction to the power applications of superconductivity, in: Handbook of Applied Superconductivity, Vol.2/part H1 (ed. B. Seeber); Institute of Physics, Bristol/UK (1998)Google Scholar
- 2.Electrial insulation in HTS power cables, fault current limiters and transformers, final report of CIGRE SC15TF1, ELECTRA no. 186,1999Google Scholar
- 8.J. Gerhold, Dielectric properties, in: Handbook of Applied Superconductivity, Vol.1/part F (ed. B. Seeber); Institute of Physics, Bristol/UK (1998)Google Scholar
- 10.R.W. Sillars. “Electrical Insulating Materials and their Applications,” Peter Peregrinus, Stevenage/UK (1973)Google Scholar
- 14.H. Okubo, H. Goshima, N. Hayakawa, and M. Hikita, High voltage insulation of superconducting power apparatus, Proceedings of the 9th International Symposium on High Voltage Engineering, Graz, Austria (1995), 9007/1-12Google Scholar
- 21.J. Gerhold, Dielectric strength of gaseous and liquid insulants at low temperatures, CIGRE — Symposium, Vienna (1987) 100-01Google Scholar
- 24.R.W. Fast and H.L. Hart, Use of glass beads to increase the breakdown voltage in subatmospheric, cold helium gas, Adv. Cryog. Eng. 35 (1990), 809–812Google Scholar