Implementation of Second Earthwire on L6 400 kV Transmission Line

The Earthwire is an important device to shield the transmission line from lightnings and to exchange information among the substations. OPGWs (Optical ground wires) are widely used for these purposes. Technical operations on the line impose a temporary implementation of a second earthwire between the two circuits. In this paper a study is undertook to understand the possible variations in the electric and magnetic field distribution and the induced currents due to the installation in a trial site of the second OPGW. In order to ensure reliabilty to the simulation, a comparison of three different calculation techniques has been conducted, and a boundary element Method has been then implemented in COMSOL Multiphysics to study a 3D configuration of the line and quantify the electric field around the pylons. To estimate the induced currents, the software ATP-EMTP has been used simulating the conditions with and without the second earthwire. Good agreement has been reached between the different numerical techniques for the field calculation, and a high value of induced current has been found on the ground wires in the case of the implementation of a second one. A measurement system has been built in Cardiff University to measure in June and August 2022 the induced current values and validate the numerical models.