杆塔冲击特性及测试回路的影响

Surge Characteristics of the Tower and Influence of the Measurement Circuit

为了准确计算雷击杆塔时塔身的电压响应,针对杆塔的冲击特性已经开展了大量的研究,但这些研究大多针对单独的杆塔,未考虑线路中杆塔的情况。本文基于FDTD方法建立了雷击杆塔的计算模型,并通过设置电压引线和电流引线模拟了测试回路存在的情况。雷击杆塔时杆塔的冲击特性与电流波形密切相关,雷电流下杆塔的冲击特性介于阶跃电流和斜波电流下的冲击特性之间。当只考虑流入杆塔部分的电流和塔顶电位时,带线路杆塔的冲击阻抗取值与单独杆塔的冲击阻抗取值几乎无区别。对杆塔的冲击阻抗进行测量时,测量系统与测量对象之间存在的电磁耦合会对结果造成影响,雷击情况下的冲击阻抗值比测试回路下的冲击阻抗值要大19%-34%。

In order to accurately calculate the voltage response of the tower when lightning strikes,a lot of research has been carried out on the surge characteristics of the tower,but most of these studies are about individual tower,without considering the tower with overhead lines. In this paper,the calculation model of lightning strikes to the tower is established based on FDTD method,and the existence of measurement circuit is simulated by setting voltage lead and current lead. The lightning striking characteristics of the tower is closely related to the current waveform,and the surge characteristics of the tower under lightning current are between the surge characteristic under the step current and the ramp current. When only the current flowing into the tower and the tower top potential are considered,the value of the surge impedance of the tower with overhead lines is almost indistinguishable from the value of the surge impedance of the individual tower. When measuring the surge impedance of the tower,the electromagnetic coupling between the measuring system and the measuring object will affect the result. The surge impedance value under lightning strike is 19% ~ 34% larger than that under the measurement circuit.