Overvoltage reduction in the TN system of a building

To protect the equipment in a building struck directly by lightning, surge protective devices (SPDs) are installed between the N-phase and ground lines at the power utility substation of a TT system. In this case, when operating the SPD, the wiring system of the low-voltage distribution line will be a TN system. Although the overvoltage between these lines at the power utility substation can be limited during SPD operation, an overvoltage between these lines is induced at each floor distribution board connected thereafter. Here, we analyzed this overvoltage in the VSTL electromagnetic analysis software. The overvoltage was found to largely depend on the loop impedance of the wirings as the lightning current flowed from the structure to the protective ground line. The most effective solution was separating the ground lines from the power supply lines connected to the distribution boards of each floor with another electric pipe shaft.

为保护遭受雷击的建筑物内设备，在TT系统中的电源公用变电站，于N相和接地线之间安装了过电压保护装置（SPD）。在此情形下，当操作SPD时，低压配电线路的布线系统将转变为TN系统。尽管在SPD操作期间，可以在电源公用变电站内限制这些线路之间的过电压，但随后的每一层配电盘连接处仍会诱生过电压。在此，我们运用VSTL电磁分析软件对这一过电压进行了分析。研究发现，过电压主要取决于导线的回路阻抗，因为雷电流从结构流向保护接地线。最有效的解决方案是，通过另一根电管道立管将接地线与连接至每层配电盘的电源线分离。