计及绕组波过程的牵引变压器防雷分析

Analysis of Lightning Protection of Traction Transformer Considering Wave Process

雷电冲击过电压有较大的幅值及陡度,侵入牵引变电所会对主变压器的绕组纵绝缘造成危害。为研究雷电侵入波对牵引变压器的影响,建立牵引变电所EMTP暂态模型,考虑雷击进线杆塔时,分析有无避雷器保护对牵引变压器上过电压参数的影响。安装避雷器后,变压器上的过电压幅值降低到最大允许耐压值以下,但其陡度减小幅度较小,对牵引变压器绕组的绝缘安全存在威胁。通过建立基于时域有限差分法的绕组多导体传输线模型,分析变压器绕组在雷电波入侵时的波过程。结果表明,雷击引起变压器绕组极不均匀电压分布,且前端绕组过电压幅值及振荡频率较高,存在绝缘隐患,应针对该位置进行重点保护。

The direct intrusion of lightning impulse overvoltage,with high amplitude and gradient,into traction substation,may severely damage the longitudinal insulation of the transformer windings.To study the impact of lightning intrusion wave on traction transformer,first,the EMTP transient model of traction substation was established.The influence of transformer with or without protection of lightning arrester on overvoltage parameters was analyzed and calculated,considering the condition of lightning striking the line tower.Analytical results showed that,with the protection of arrester,the amplitude of the overvoltage on the transformer decreased below the allowable value,while the gradient almost remained the same,which posed a threat to the insulation safety of the traction transformer windings.The multi-conductor transmission lines（MTLs）model based on finite difference time domain method was established to analyze the wave process of transformer windings at the time of lightening wave intrusion.The analytical results indicated that the lightning stroke caused uneven voltage distribution of the transformer windings,higher amplitude and oscillation frequency of the overvoltage of the front end winding and hidden insulation problem.Protection should be focused on this position.