架空屏蔽电缆–大地耦合的感应电流谐振分析

Resonance Analysis on Induced Current of Coupling Between Overhead Shielded Cables and Ground

为了从理论上分析计算空间电磁场耦合在电缆上产生的感应电流,基于架空屏蔽电缆–大地回路的有源传输线模型,得到电缆两端接不同负载时,空间电磁场在电缆上产生的感应电流的解析表达式;分析了电缆感应电流的谐振机理,得到了谐振频率与电缆长度应满足的关系;并讨论了感应电流谐振与大地电导率、电缆架空高度等参数的关系。研究结果表明,当电缆感应电流发生谐振时,电缆–大地回路时间常数越大,感应电流越大;当大地电导率为0.01 S/m、照射波频率为75 MHz、电缆半径为4 mm、电缆距地高度为1 m、电缆长度为2 m、电缆两端架空时,电缆上感应电流的理论计算结果与实测结果之间的误差<5 d B。

In order to theoretically analyze and calculate induced current on cable caused by space electromagnetic field coupling, we obtained the analytic expression of the induced current for different terminal loads of cable by using the transmission line model with a distributed source of aerial shielded cable-ground circuit. Then we analyzed the resonance mechanism of induced current, and acquired the relationship between resonance frequency and cable＇s length. Additionally, we discussed the relationship among induced current resonance, ground conductivity, and cable＇s overhead height. The results show that, when resonance occurs in the induced current, its amplitude increases with the cables-ground circuit＇s time constant. Under preconditions including earth conductivity of 0.01 S/m, irradiation wave frequency of 75 MHz, cable radius of 4 mm, height between cable and ground of 1 m, cable length of 2 m, and both ends of cable being overhead, error between the theoretically calculated result and measured result of the cable induced current is below 5 dB.