基于EMTP和BP神经网络的超高压电缆护套雷击感应电压研究

Investigation for Sheath Induced Voltage of Extra High Voltage Cable due to Lightning Surge Based on EMTP and BP Neural Network

电缆遭受雷电波冲击时金属护套感应产生的过电压极易击穿护层绝缘,需要的护套雷电浪涌感应电压进行合理计算和预测。本研究利用EMTP软件搭建架空线路-埋地电缆电路模型,计算雷击线路时电缆护套最大感应电压,分析电缆布置方式、电缆间距和长度、护套接地电阻、雷电流参数等因素对护套感应电压的影响。在仿真结果的基础上,提出一种基于BP神经网络模型预测电缆护套感应电压预测方法,并将预测结果与仿真模型进行对比。研究结果表明:电缆间距、电缆长度、护套层的接地电阻、雷击点距电缆距离、雷电流幅值与波前时间对护套感应电压存在较为明显的影响;电缆布置方式对护套感应电压存在一定影响;杆塔接地电阻变化几乎不影响护套感应电压。采用交叉互联接地方式时,护套雷电冲击感应电压仍然有可能超过绝缘耐受电压,建议安装护套浪涌保护器。根据仿真分析结果建立的BP神经网络预测模型预测结果与仿真结果之间的平均相对误差小于7%,具有良好的预测性能。

High induced voltage may occur in the cable sheath when lightning surge invades into cable line,which will result in breakdown of the insulation system,so it is necessary to calculate and forecast sheath induced voltage due to lightning surge exactly.Equivalent circuits of transmission line combined with buried cable were established in EMTP,the effect of different parameters,including cable structure,sheath ground resistance,tower ground resistance,amplitude and wave front time of the lightning current were investigated.A BP neural network model was designed based on the simulation results to predict the maximum induced voltage of the cable sheath.Research results show that:cable length,distance between the cable conductors,sheath ground resistance,amplitude and wave front time of the lightning current have more influence on the sheath induced voltage and cable arrangement also has certain effects,while tower ground resistance has little impact.It can be stated that the maximum sheath induced voltage when the sheaths are cross-bonded may also exceed its insulation level and the installation of line arresters are recommended.The mean absolute percentage errors between the induced voltages of the simulation and the proposed method were less than 7%,which verifies the proposed BP neural network model performance.