High temperature superconducting (HTS) transformers windings operate subcooled at atmospheric pressure to temperatures as low as 65 K, with minimal power dissipation from AC loss in normal operation. During short circuits, HTS transformers are subjected to transient heating by currents as much as 10x rated current for durations of up to 2 s. After isolating the fault, HTS transformers are required to cool back down to their base temperature while carrying the operating current. HTS transformer conductors are insulated, typically with wrapped self-adhesive polyimide tape, and windings consist of close packed conductors wound on composite formers. In this paper, the heat transfer, transient thermal response, and recovery performance of brass-laminated coated conductor HTS wire as well as metallic conductors in liquid nitrogen (LN2) were measured at a range of temperatures from 77 K to 64 K and pressures from atmospheric to 0.14 bar in heating and cooling situations. Measurements were made on bare tapes, and on tapes wrapped with polyimide insulation tape and with aramid paper as well as polymer coated tapes with a range of coating thickness. Heat transfer from tapes mounted with one face in contact with a glass-epoxy composite cylindrical former was measured for comparison with free-standing tapes. Using conductors with solid polymer coatings of optimized thickness immersed in subcooled LN2 results in the highest heat transfer and fast recovery following heating to 300 K by a high current pulse. Compared to a bare tape in LN2 at ambient pressure at 77 K, the heat transfer in a coated tape in 65 K subcooled LN2 can be very significantly enhanced, by up to a factor of 15x, and recovery can be 7x faster.

中文翻译：

---

金属和超导带在高电流脉冲下的传热和恢复性能增强，以改善高温超导变压器的故障限流行为

高温超导 (HTS) 变压器绕组在大气压下过冷运行至低至 65 K 的温度，在正常运行时交流损耗的功耗最小。在短路期间，HTS 变压器会受到高达 10 倍额定电流的电流的瞬时加热，持续时间长达 2 秒。隔离故障后，HTS 变压器需要在承载工作电流的同时冷却回其基础温度。HTS 变压器导体是绝缘的，通常使用缠绕的自粘聚酰亚胺胶带，绕组由缠绕在复合线圈上的密堆积导体组成。在本文中，传热、瞬态热响应、在 77 K 至 64 K 的温度范围和大气压至 0.14 bar 的加热和冷却条件下，测量了黄铜层压涂层导体 HTS 线以及金属导体在液氮 (LN2) 中的性能和恢复性能。测量是在裸胶带、用聚酰亚胺绝缘胶带和芳纶纸包裹的胶带以及具有一定涂层厚度的聚合物涂层胶带上进行的。为了与独立式胶带进行比较，测量了从一个面与玻璃环氧树脂复合圆柱模型接触的胶带的传热。将具有优化厚度的固体聚合物涂层的导体浸入过冷的 LN2 中，可在通过高电流脉冲加热至 300 K 后实现最高的热传递和快速恢复。