Fast insertion impedance of 2G HTS superconductors for megawatt AC and repetitive pulsed power operation

Abstract

Within the past few years a newer, more robust type of superconductor known as 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</sup> Generation (2G) High Temperature Superconductors (HTS) wire capable to operate in LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> has become available in sufficient quantity and lengths for developers to build prototype devices and test their capabilities. 2G HTS made possible to reduce size, weight and volume of electrical apparatus in few orders of magnitude and provide a fast switching power and energy transitions with negligible impedance in superconducting stage and fast transitions impedances in resistive stage. This transition is typically called quenching and is useful for driving high impedance loads, limiting fault currents and developing large steep insertion impedances useful in many pulsed power applications. Electrical equipments made out of copper or aluminum typically shows high current transitions, inrush and short circuiting faults currents that can reach 100's of kA. There is a need for having repeatable fast insertion impedance to transform high current transitions, useful for impedance matching, stabilization, robustness of large current transients and proper dielectric operation in Megawatt installations. Development of Superconducting Fault Current Limiters (SFCLs) has been pursued for decades and has been limited thermally and/or mechanically by the available superconducting materials performance characteristics. However, this new 2G material has re-invigorated the worldwide race to develop a successful SFCL device that meets the stringent demands of Megawatt power equipment. SuperPower is pursuing the development of modular SFCL based on its proprietary 2G HTS wire and SFCL technologies. We will discuss testing and improvements made to optimize Recovery Under Load (RUL) performance. We also discuss high power tests and the influence of the different variables that have an important impact in RUL. A wide operating RUL window has been tested in order to define where RUL is feasible. We will show the manufacturing and latest tests and capabilities of sub-cooled of the SFCL device and modules designed for distribution and transmission lines. We show the advantages and superior performance of the new 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</sup> Generation HTS superconductors under sub-cooled liquid nitrogen operation when used in SFCL.