基于高温超导的高精度电压互感器研究

电压互感器的励磁误差由励磁电流在电压互感器绕组上的压降产生，是电压互感器误差的主要来源。双级励磁技术可以有效降低电压互感器的励磁电流，但绕组阻抗始终无法消除，励磁误差仍然存在。本文将77K高温超导技术应用于电压互感器，绕组和互感器铁心均工作在高温超导环境，达到超导态时绕组的阻抗为零，励磁电流经过绕组引起的压降也为零，可以从根本上消除励磁误差。分析了高温超导下的铜损和铁心磁性能，重点针对铁心的磁滞和涡流损耗进行了理论分析并提出抑制措施，设计了一台变比为1kV/10V的电压互感器的铁心和绕组结构，研制了高温超导电压互感器样机，设计了低温杜瓦容器及其外部冷屏设计，减小热量损失温度场，开展温度场仿真分析温度分布梯度。最后开展了误差校准，校准结果表明，该样机在20%~120%额定电压范围内，比值误差优于4×10-6，相位误差优于5μrad，比常温电压互感器的误差减小一个数量级。77K高温超导电压互感器对于提升电压互感器的精度具有重要意义，同时也可为更高电压等级的超导互感器研制提供理论支撑。

Research on high precision voltage transformer based on high temperature superconductivity

The excitation error of voltage transformer is caused by the voltage drop of the excitation current in the winding of voltage transformer, which is the main source of the error of voltage transformer. The two-stage excitation technology can effectively reduce the excitation current of the voltage transformer, but the winding impedance cannot be eliminated and the excitation error still exists. In this paper, 77K high temperature superconductivity technology is applied to voltage transformer (HTS-VT), the winding and transformer core are working in high temperature superconducting environment, when the superconducting state is reached, the impedance of the winding is zero, and the voltage drop caused by the excitation current through the winding is also zero, which can fundamentally eliminate the excitation error. The copper loss and core magnetic properties of HTS-VT were analyzed. The hysteresis and eddy current loss of the core are analyzed theoretically and the suppression measures are put forward. The core and winding structure of a voltage transformer with a ratio of 1kV/10V were designed. A prototype of HTS-VT voltage transformer was developed. The low temperature Dewar container and its external cold screen were designed to reduce the heat loss temperature field, and the temperature field simulation was carried out to analyze the temperature distribution gradient. Finally, its errors were calibrated, and the calibration results show that the ratio error of the prototype is better than 4×10-6 and the phase error is better than 5μrad in the rated voltage range of 20%~120%, which is an order of magnitude smaller than that of the normal temperature voltage transformer. 77K high temperature superconducting voltage transformer is of great significance for improving the precision of voltage transformer, and can also provide theoretical support for the development of higher voltage grade superconducting transformer.