城市架空配电线路与埋地电缆混合传输系统雷击可靠性分析

Reliability Analysis of Urban Overhead Distribution Lines Combined with Buried Cables Under Lightning Surge

城市配电线路建设会存在架空线路与埋地电缆混合传输现象,需要合理分析混合传输系统雷击可靠性以进行针对性防护。通过EMTP软件建立架空线路与埋地电缆混合传输系统模型,利用事件树方法估算系统雷击可靠性,分析电缆避雷器安装方式、杆塔接地电阻、埋地电缆长度等因素对系统雷击可靠性影响,最后讨论缩短故障修复时间提高系统雷击可靠性效果。研究结果表明:埋地电缆两端均安装避雷器时,系统雷击可靠性最高,略高于仅在一端安装避雷器情况。系统雷击可靠性随着线路杆塔接地电阻或埋地电缆长度的增加而降低,杆塔接地电阻对可靠性影响程度更明显。系统雷击可靠性随着系统平均故障修复时间的缩短而显著提高。需要尽可能降低线路杆塔接地电阻、缩短系统故障修复时间以确保混合传输系统雷击安全性。

Overhead lines combined with buried cables may exist in urban distribution construction so it is necessary to analyze reliability indices of overhead distribution lines combined with buried cables under the lightning surge.Equivalent models of 10 kV mixed transmission system were established in EMTP and reliability analysis was done by means of event tree method.Influences of installations of surge arresters,grounding resistance and cable line length on system reliability were analyzed.Finally,the protection effect of shortening fault repairing time was discussed.Research results show that: reliability indices is the highest when surge arresters are installed at both ends of the buried cable,which is slightly above that installed at only one end.Reliability indices decrease with increasing of grounding resistance or cable line length,which is more affected by grounding resistance.Shortening fault repairing time may improve system reliability significantly.It is essential to shorten fault repairing time and reduce grounding resistance as much as possible.