水电站大容量高压发电机定子单相接地故障保护原理研究

Powerformer can be connected to the power grid in the absence of transformers directly, which reduces its construction, operation and maintenance cost greatly according to the accounting of Swedish consulting firm SWECO. Compared with the traditional generator, the innovation of the stator winding material causes the difference between the physical characteristics of the electrical parameters and the mathematical model. The improvement of the winding mode causes the different between the multiple physical fields’ distribution and the insulation level. The update of the grid connection causes a change in transmission path of the fault component and the protection scheme. For this reason, the project based on the electrical and physical properties of the Powerformer carries out for the research of the stator single phase ground fault protection. There are three main contents. Firstly, considering the magnetic field distribution of current-carrying wire core by split insulation, the boundaries jump of winding graded insulation parts, and the coupling effect of multiple physical fields based on the electric field, magnetic field and temperature field, the electrical parameters of stator winding will be calculated, and precise mathematical model will be built for the stator winding of the Powerformer. Secondly, the operation way of the Powerformer neutral point will be analyzed, according to the flux density distribution under the different tooth size, the mathematical description of turns electromotive force will be given, and analyzing the changing rule of the electric parameters and extracting fully accurate fault information will be done. Finally, the protection strategy which can identify the inside and outside fault for the single generator and selectively find out the fault generator from multiple generators will be proposed. The research results will provide theoretical support for the research of relay protection for new generation energy power system, and promote the development of power industry.

高压发电机可省去升压变压器与电网直联，据瑞典咨询公司SWECO核算，其建设、运行与维护费用大幅降低。与常规发电机相比：定子绕组材料的创新引起电气参数物理特性与数学模型的不同；绕制方式的改良引起多物理场分布与绝缘水平的不同；并网方式的更新引起故障分量传输路径与保护方案的变革。为此，本项目立足高压发电机电气及物理特性，开展定子单相接地保护研究，主要内容为：考虑载流分股绝缘线芯之间的磁场分布、绕组分级绝缘处的边界跃变、电场-磁场-温度场的多物理场耦合效应，计算定子绕组电气参数，构建高压发电机定子绕组精确数学模型；分析高压发电机中性点运行方式，针对不同齿部尺寸下磁密分布特性，给出每相每分支匝电动势的数学描述，并分析电气量的变化规律及提取准确充分的故障信息；提出基于单台及多台选择性的发电机定子单相接地故障保护策略。研究成果为新一代能源电力继电保护研究提供理论支撑，为助推我国电力行业发展提供技术保障。

高压发电机定子单相接地保护研究是国内外电力科学技术发展的重大需求，本项目立足于高压发电机独特的定子结构及电气特性，提出了一系列高压发电机定子单相接地故障保护方法。首先，为了准确刻画高压发电机定子绕组的数学模型，项目针对载流分股绝缘线芯之间的磁场分布、绕组分级绝缘处的边界跃变、电场-磁场-温度场的多物理场耦合效应，计算了定子绕组电感参数、电容参数、电阻参数，构建了精确定子绕组数学模型。同时定量刻画了高压发电机定子齿部各位置齿宽分布情况，针对高压发电机不同齿部尺寸下磁密分布特性，定性分析了高压发电机定子齿宽与每相每分支匝电动势的差异性分布。而后，为深入挖掘故障信息的本质特征和内在规律，项目基于故障信息的分布规律，借助能够挖掘并融合多维、多尺度、多变量的、故障特征量的人工智能算法，准确提取优质的故障信息，提出了利用利用S变换构造高压发电机定子单相接地故障下暂态零序电流幅-时-频矩阵，提取S变换幅-时-频矩阵相关系数、S变换暂态能量特征和暂态零序有功功率特征作为特征向量以及基于时域卷积网络的特征构造方法，实现故障发电机与健全发电机间故障特征量变化的数学描述。最后，为了解决高压输电网三次谐波电压波动对保护方案的干扰以及保护可靠性问题，项目创新性地提出计及匝电动势相位及幅值差异特性的基于电压量的定子接地保护原理；借助数据科学最新技术，提出面向单台或多台高压发电机直并网接线方式下的选择性保护方案；设计了基于电压量保护判据的面向单台高压发电机的定子接地保护和基于机器学习算法的无整定值的面向多台高压发电机的定子接地保护，提高了发电机定子接地保护的精度和鲁棒性。研究成果有望为新一代能源电力继电保护研究提供理论支撑，为助推我国电力行业发展提供技术保障。