Quench Detection and Protection of Cryocooler-Cooled YBCO Pancake Coil for SMES

Abstract

In this paper, we focus on the quench detection and protection of a cryocooler-cooled pancake coil for SMES wound with a YBCO bundle conductor composed of laminated electrically insulated YBCO-coated conductors. Because the normal-zone propagation velocity is much slower in a high-temperature superconducting (HTS) coil than in a low-temperature superconducting (LTS) coil, the detection of the non-recovering normal zone using a voltage signal is quite difficult. Quench detection is considered to be more difficult during SMES operation because of the noise of the converter or other equipment. Therefore, a quench must be detected using some other method. In the previous paper, we showed that a quench in the coil could be detected by observing the transposition of the current in the bundle conductor caused by local normal transition. In this paper, based on this quench detection method, we investigate the transposition of current and the thermal behavior during the quench detection and the dumping of the stored energy by an external resistance in coils wound with a YBCO laminated bundle conductor for SMES and determine the appropriate stabilizer thickness of the YBCO-coated conductors.

High normal zone propagation velocity in second generation high-temperature superconductor coated conductors with a current flow diverter architecture

“…The very high operating current densities (>MA cm −2 ) of second generation (2G) high-temperature superconductor (HTS) coated conductors (CCs) make them candidates of choice for developing power devices such as superconducting fault current limiters [1], superconducting cables [2], superconducting transformers [3], superconducting electromagnets [4], superconducting motors [5], superconducting magnetic energy storage [6], etc. However, one of the major issues with 2G HTS CCs is that they are prone to develop destructive 'hot spots', particularly when the transport current is close to their critical current (I c ).…”

Thermal Runaway of Conduction-Cooled Monofilament and Multifilament Coated Conductors

“…However, the initiation of thermal runaway in multifilament coated conductors has not been experimentally studied. Furthermore, previous experimental studies on thermal runaway did not directly discuss the conditions under which the conventional quench detection and protection scheme (i.e., detecting quench/thermal runaway using voltage taps and dumping the stored energy in an external dump resistor) could be applied [22][23][24][25][26][27][28][29][30][31][32].…”