2) Induced Surge

During summer a very large negative charge develops in the upper part of lightning clouds.
If there is a power transmission or a communication line near this could, equilateral electric charges collect on the lines and it has high voltage.
An induced electrostatic surge occurs when there is a positive charge on the line near a negative charge from a lightning cloud. When the cloud releases its charge to another cloud or the ground, the charge on the cable is released and it travels in both directions as a wave.





When an electric discharge (lightning) occurs between a cloud and the ground, a severe electric current drifts and the induced surge produces an electromagnetic field.
If a power transmission line and a communication cable are nearby the lightning strike, they act as an antenna and electromagnetic induction causes abnormal voltage.
When an electric discharge occurs between lightning clouds or between a lightning cloud and the ground, abnormal electrostatic and electromagnetic voltage is induced to the neighboring power transmission line or communication line. This is called an induced surge and is illustrated in fig.2 (a) and (b).



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