Silicon carbide particle-loaded semi-conductive materials with electric field-dependent conductivity have been used for end-turn stress grading (SG) systems of high voltage rotating electrical machines for decades. Particularly, high voltage class turbogenerators use double-layer SG systems, at which two SG materials with different conductivities are applied, to reduce power dissipations within the SG materials. To prevent the excessive local heating of the SG material and resulting flashover, the field-dependent conductivities of the two SG materials, as well as length of the SG layer in the longitudinal direction along a coil, were optimized, by a nonlinear transient electrical field and thermal coupled analysis. The field-dependent conductivities of the SG materials were adjusted to the suitable ones by changing the average diameter of silicon carbide particles. Then, the appropriate length of the SG layer was selected to minimize the temperature rise in the system. As a result, the newly optimized double-layer SG system showed a 20% lower temperature rise, and more than 15% higher flashover voltage than the conventional ones. Therefore, the effectiveness of the optimized double-layer SG system is successfully confirmed.

中文翻译：

---

电场与热耦合分析优化高压旋转电机双层应力分级系统


具有电场相关电导率的碳化硅颗粒半导体材料几十年来一直用于高压旋转电机的端匝应力分级 (SG) 系统。特别是，高压级涡轮发电机使用双层SG系统，其中应用两种具有不同电导率的SG材料，以减少SG材料内的功率耗散。为了防止 SG 材料过度局部加热并导致闪络，通过非线性瞬态电场优化了两种 SG 材料的场相关电导率以及沿线圈纵向的 SG 层长度和热耦合分析。通过改变碳化硅颗粒的平均直径，将SG材料的场相关电导率调整到合适的值。然后，选择适当的SG层长度以最小化系统中的温升。结果，新优化的双层SG系统比传统系统的温升降低了20%，闪络电压提高了15%以上。因此，优化后的双层SG系统的有效性得到了成功证实。