A New Technology for Measuring Overhead Line and Cable Impedance Values and the Ground Impedance of Large Substations

The knowledge of overhead line and cable impedances is very important for the correct setting of impedance protection relays. Line-to-line impedances can be calculated with acceptable accuracy, but line-to-ground impedances have to be measured because the calculation does not fit within the real condition of the specific ground resistance with metallic pipes, cables, and other metallic parts in the ground.