Danny G. Crook

Performance of 2G HTS Tapes in Sub-Cooled LN2 for Superconducting Fault Current Limiting Applications

Within the past few years a newer, more robust type of superconductor known as 2nd Generation High Temperature Superconductor (HTS) wire, has become available in sufficient quantity and lengths for developers to build prototype devices and test their capabilities. This new material offers the potential for revolutionary changes in superconducting transformers and Super conducting Fault Current Limiters to enable better thermal stability and fast quenching capabilities that can meet the stringent demands of large transient faults for distribution and transmission power lines. This manuscript discusses the manufacturing and latest tests and capabilities of sub-cooled superconducting fault current limiter device and modules designed for distribution and trans mission lines. We will also discuss the advantages and superior performance of the new 2nd Generation HTS superconductors under sub-cooled liquid nitrogen operation when used in super conducting fault current limiters. The feasibility demonstration and performance of sub-cooled SFCL superconducting modules for distribution and transmission SFCL devices will be discussed.

Surface Flashover of Cylindrical G10 Under ac and dc Voltages at Room and Cryogenic Temperatures

The results of experimental determination of surface flashover breakdown voltage under high voltage ac and dc for cylindrical G10 are presented. The results are analysed using Weibull statistics and are compared with theoretical field calculations obtained using Ansoft, which is a software package based on finite element analysis. The results show that there is significant improvement of the parameters such as surface flashover voltage and reliability of the results at 77 k over those at 293 K.

Simulation and Optimization of Cryogenic Heat Sink for Helium Gas Cooled Superconducting Power Devices

Superconducting power devices require cable terminations to be cooled within the operating cryogenic temperature range to reduce ambient heat influx. Shipboard power systems require the use of helium gas as coolant due to possible hazards by use of liquid cryogens. A model is being developed using finite element analysis to study the feasibility of a helium-gas-cooled heat sink for cable terminations. The results obtained using the COMSOL Multiphysics computing package are validated with an experimental setup. The coolant temperature and pressure drop correspond well with the theoretical results. Furthermore, the heat sink is geometrically optimized for given mass flow rate and input conditions to produce a better thermal and fluid performance in terms of temperature gain and pressure loss.