3D FEM analysis of induced current in the shield of the buried cable by non-vertical channel

Abstract

The induced current in the buried cable shield is evaluated by solving the full-wave Maxwell equations with the Finite Element Method (FEM). Three different cases are considered for the lightning channel, including the “straight inclined” channel, “bent channel”, and “Tortuous channel”. Straight inclined lightning is one part channel that could have different angles with Z-axis at XZ and YZ plane. The bent lightning is included the upper part and lower part that are joined to each other at the “bent” point at height Ha. Different sizes are considered for the Ha, and angle of each part. The tortuous channel is a linear piecewise approximation of realistic lightning. The impact of the channel shape, channel angle, bent height, and lightning current waveform on the induced current in the buried cable shield is investigated. The results reveal that waveforms and peak value of the induced current are significantly affected by channel shape. Comparing the results of different lightning shapes reveals that the induced current peak and waveforms highly depends on the lightning channel shape between ground to 250 m height from the ground. Comparing the tortuous channel results with inclined and bent lightning reveals that bent lightning is a better approximation than inclined lightning. Statistical analysis of the results shows the effect of the channel shape for the case that lightning current waveform have faster rising time is more significant.