Investigation of transient induced voltage to a communication line from an overhead power transmission line

A transient voltage induced on a communication line by an overhead power transmission line is investigated using analytical formulas of the voltage and the maximum voltage value and on results calculated with EMTP and using a frequency-domain method. A large transient induced voltage, which is several times greater than the steady-state induced voltage during a line-to-ground fault, is generated because of the different propagation times of the aerial and earth-return modes in the case of a switching surge with no source inductance and that of a line-to-ground fault surge. The transient induced voltage in the switching surge case, with a source inductance, can be neglected because it is of the same order as the steady-state induced voltage during a fault. Based on a parametric analysis of the induced voltage, it was found that, the transient and steady-state induced voltages generally increase as the line length and earth resistivity increase, and as the source inductance and separation between the power and communication lines decrease