Practical conclusions from field trials of a superconducting cable

Abstract

Field trials of a Fully Flexible Superconducting Cable (60 kV/1000 A, design Klaudy-Kabelmetal) including the necessary potheads were performed successfully in a real grid for the first time in the world during the years 1977-1980 at Arnstein (Austria). The cable met all electrotechnical and cryotechnical field and test conditions. Encouraged by this success and based on the experiences gained in Arnstein as well as on further theoretical and practical investigations, the authors propose a simplified version of the Fully Flexible Arnstein cable with an improved new superinsulation saving the nitrogen cooling stage. The proposed cable is based on the corrugated tube principle (Wellmantel-technique of Kabelmetal) and offers an economically competitive and technically superior construction compared to presently favoured watercooled cables in the power range of 1 GW or even lower. This power rating is of interest already today for the electricity supply in densely populated areas and industrial centers. Fully Flexible Superconducting Cables have the following essential advantages over other superconducting and conventional cables: 1. The cable can be fabricated in great lengths (a couple of hundred meters) at low cost with well proven methods and equipment. 2. They can be reeled, shipped, and laid like any conventional cable in individual sections. 3. They require no sophisticated expansion elements as the thermal length changes occuring during cooling cycles of the cables are compensated for thanks the elasticity of the corrugated tubes. 4. They guarantee high operational safety since only a small number of splices and joints are necessary for connecting the individual sections of the cables. 5. They offer a high lifetime compared to conventional cables. 6. They are especially suited for the transmission of base load power at power ratings down to 1 GW and at voltages of 100 - 140 kV. 7. Being superconducting cables, they offer the possibility of perfect electromagnetic shielding towards their environment. Shield currents cause practically no losses. 8. The cables require surprisingly small trench widths - an advantage which can not be achieved with any type of normal conducting cables. Consequently Fully Flexible Superconducting Cables of the corrugated tube design will be of importance in connection with electrical high power transmission in future.