隔直装置安装位置对电网主变压器直流偏磁电流分布影响研究

Research on Influence of Installation Position of DC Blocking Devices on DC Magnetic Bias Current Distribution of Main Transformer in Power Grid

摘要:

针对城市电网直流偏磁主变压器中性点安装隔直装置后，导致周围其他主变压器中性点直流增加出现直流偏磁这一现象，提出研究隔直装置安装位置对城市电网主变压器直流偏磁电流分布的影响。考虑地铁回流系统结构、换乘站综合接地系统连接特征以及地铁和城市电网空间、电气连接关系，基于CDEGS仿真软件建立西南某城市电网及地铁网络耦合模型。在此基础上，仿真分析了不同类型变电站安装隔直装置后，电网变电站主变压器直流偏磁电流幅值变化特征。分析结果表明，为地铁主变电所供电的220 kV变电站安装隔直装置后，与其直连的变电站主变压器直流偏磁电流总量减少超过15%，能够显著抑制直流偏磁电流，为城市电网变电站隔直装置安装位置确定提供理论依据。

关键词:隔直装置安装位置; 地铁杂散电流; 城市电网; 主变压器直流偏磁电流

Abstract:

A study on the influence of installation position of DC blocking devices on DC magnetic bias current distribution of main transformer in urban power grid is proposed after the installation of DC blocking devices at the neutral point of main transformer in urban power grid, which leads to the increase of DC at the neutral point of the surrounding main transformers and the phenomenon of DC bias magnetization. By considering the structure of subway return system, the grounding system of transfer stations and the spatial and electrical connection relationship between subway and urban power grid, a coupling model of urban power grid and subway network for a city in southwest China is established based on CDEGS simulation software. On this basis, the simulation analyzes the characteristics of amplitude change of DC magnetic bias current of main transformer in grid substation after the installation of DC blocking devices in different types of substations. The analysis results show that after installing DC blocking devices in 220 kV substation supplying the metro main substation, the total DC magnetic bias current of substation which directly connected to it is reduced more than 15%, which can significantly suppress the DC magnetic bias current and provides a theoretical basis for the determination of installation position of DC blocking devices in substations of urban power grid.

Key words:installation position of DC blocking devices; metro stray current; urban power grid; DC magnetic bias current of main transformer