Study on stabilization and quench protection of coils wound of HTS coated conductors considering quench origins – Proposal of criteria for stabilization and quench protection

Abstract

a b s t r a c tIt has been considered that HTS coils are hard to be quenched because of high quench energy due to high critical temperature and high specific heat of HTS wires. Therefore, attention to quench protection was not much paid. However, HTS coils still have possibility to be quenched during operation by mainly the following two origins, (a) presence of non-recoverable local defects in the conductors and (b) temperature rise of long part of the conductor. Actually, severe quench accidents, such as burning coils, are occurring in various places as scales of HTS increased. Purposes of this paper are to study on behaviors of normal zone and hot spot temperature of wires during quench detect/energy dump sequence and to find criteria for the stability and quench protection. In the paper, criteria are proposed for stability and quench protection of HTS coils. A criterion for the stability is that a coil can be operated stably without a quench against defects in coil windings and that for quench protection is that a coil can be safely protected from damages caused by a quench due to temperature rise of long part of coil wires. The criteria are used as design rules for HTS coils.

Quench Protection Characteristics of Coil Wound of Bi/Ag-Sheathed Wire

“…This jump indicates that a thermal run-away occurs and a coil is damaged. Details of those phenomena are shown in the reference [4]. Maximum threshold of V res vs. τ for safe coil protection is obtained by the numerical simulations and shown in Fig.…”

“…The authors investigate quench protection characteristics of coils wound of Bi/Ag-sheathed wires. It is considered that there are three kinds of causes of unexpected quenches during operation of HTS coils, a) local transient heat disturbances, b) appearance of non-recoverable local defects in the conductor which may be caused by fatigue effect due to repeated mechanical stresses [2] and c) appearance of long resistive zone caused by temperature rise of long part of the conductor due to malfunction of cryogenic system, for example [3], [4]. Quenches by the cause a) are rare in HTS coils because of high temperature margin of HTS wires.…”

Резистивные Состояния Композитных Сверхпроводников При Крипе Магнитного Потока

“…Ее основные положения были сформулированы для низкотемпературных сверхпроводящих композитов в рамках модели скачкообразного перехода из сверх-проводящего состояния в нормальное (так называемая модель критического состояния МКС), которая позво-лила не только упростить используемые методы ана-лиза, но и выписать аналитические критерии тепловой стабильности сверхпроводящего состояния [1][2][3]. Эта модель также широко используется и при описании тепловых процессов в композитах на основе высоко-температурных сверхпроводников (см., например, [4][5][6]). В рамках данного приближения предполагается, что транспортный ток равномерно распределен по сечению композита, а его значения в сверхпроводнике и матрице определяются мгновенными значениями температуры сверхпроводника.…”

An open-source 3D FE quench simulation tool for no-insulation HTS pancake coils

“…The quench behaviour of HTS magnets differs from low-temperature superconducting magnets. HTS magnets have lower normal zone propagation velocity [1], and the critical current density of an HTS tape strongly depends on the direction of the magnetic field [2]. Consequently, quench protection of HTS magnets is regarded as one of the challenging technical issues for HTS technology.…”