内设防雷引下线风力机雷击暂态特性分析

风力机塔筒内部增设引下线提供了一条新的防雷思路,但需要详细分析引下线泄流过程对塔筒内部电气线缆电磁干扰影响。通过EMTP软件搭建风力机叶片、塔筒和接地系统模型,分析引下线与塔筒分流情况,考虑引下线与内部电气线缆电磁耦合作用,计算不同高度处引下线与电缆线间电位差及平均电场强度。讨论引下线与电缆线安全距离及其受雷电流波头时间和土壤电阻率影响。研究结果表明:增设内部引下线后,绝大部分雷电流经由引下线泄散入地;引下线与电缆线间电位差可达MV级别,二者间平均电场强度极易击穿周围空气,发生侧向闪络;但引下线与电缆线间电位差随着塔筒高度的降低发生极性反转,平均电场强度也呈现出先降低后增加的变化趋势。缩短引下线与塔筒间等电位连接间距能够降低引下线和电缆线间电位差与平均电场强度。引下线与电缆线间的安全距离随着雷电流波头时间的缩短和雷电流幅值的增加而增大,随着土壤电阻率的降低而减小。增设内部引下线需要合理设置其与塔筒等电位连接间距和与内部电缆线安全距离。

Analysis on Lightning Transient Characteristic of Wind Turbine Equipped with Internal Down Conductor

Adding an internal down conductor provides a new way for lightning protection of the wind turbine, but it is necessary to analyze electromagnetic interference on internal cable line when lightning current flows through the down conductor. Circuit models of blades, tower and grounding system were established in EMTP to analyze current distribution characteristics of the down conductor and the tower. Voltage difference between the down conductor and the cable line and the average electric field were calculated which takes coupling effect into consideration. Safety distance between the down conductor and the cable line was presented and effects of current wave front time and soil resistivity were discussed. Research results show that: most of the lightning current flows through the down conductor and voltage difference between the down conductor and the cable line can be up to several MV which leads to side flashover easily. Voltage difference has a polarity reversal and average electric field firstly decreases and then increases with the decrease of height. Shortening equipotential bonding distance could reduce voltage difference and the average electric field effectively. Decrease of current wave front time or increase of current amplitude results in a rise of safety distance between the down conductor and the cable line while effect of soil resistivity is opposite. It is essential to set equipotential bonding distance and electrical safety distance properly when internal down conductor is adopted.