Filtering properties of periodically grounded multiconductor power lines

This paper deals the effect of the periodical grounding of the shield wire in multiconductor power lines. The grounding of the shield wire is usually realized in order to prevent direct lightning of the power wire or the mitigate the induced overvoltages. However, this operation introduces a filtering property in the frequency behavior of the transmission line, which can be clearly observed in the characteristic impedance. It is worth to observe that, even if the grounding is performed just on the shield wire, the filtering property can be observed also on the phase wires. The paper also shows a methodology to deal with problems mixing concentrated and distributed parameters equations.