基于场路直接耦合法的电压互感器匝间短路外特性分析

External characteristics analysis of voltage transformer inter-turn short circuit based on field-circuit direct coupling method

发电机出口电压互感器(TV)匝间短路将在系统中产生不平衡电压导致发电机基波零序定子接地保护动作,TV故障外特性对机组稳定运行有重要意义。对此,基于Maxwell和Simplorer软件对单相电压互感器电磁转换过程仿真,建立可在每一计算步长实现场路间数据交换的场路直接耦合有限元模型,针对TV一次绕组匝数大难以直接建模,提出绕组分组技术,并设计搭建了实验平台,对有限元仿真模型的准确性进行实验验证。基于有限元特征量计算结果,分析了TV不同运行状态的电、磁特征量,并给出了基于绕组分组技术的TV匝间故障解析模型。仿真验证结果表明:TV匝间故障解析模型进行一次电流、环流等故障特征量分析准确有效。

Voltage transformer(TV) interturn short circuit at generator outlet will cause unbalanced voltage in system, resulting in zero sequence stator ground fault protection of generator fundamental. The external characteristics of TV fault are of great significance to stable operation of the unit. In order to understand the external characteristics of TV fault, based on Maxwell and Simplorer software, a field circuit direct coupling finite element model for the electromagnetic conversion process of single-phase voltage transformer is established, which can realize data exchange between field circuits at each calculation step. In view of the large number of turns of TV primary winding, which is difficult to model directly, winding grouping technology is proposed. An experimental platform is designed and built to verify the accuracy of the simulation model. Based on the calculation results of finite element eigenvalues, the electrical and magnetic eigenvalues of TV in different operating states are analyzed,and the analytical model of TV inter turn fault based on winding grouping technology is further given. The simulation results show that, the TV turn-to-turn fault model is accurate and effective in analyzing the primary current, circulating current and other fault characteristic quantities.