DISPLACEMENT CURRENTS EFFECTS ON EARTH-RETURN PARAMETERS

The article presents the earth's contribution to self and mutual impedances of double-wired aerial lines passing over a homogenous earth (one-layered earth) due to its importance in electromagnetic compatibility problems in electric power systems. In order to clarify the earth contribution of aerial line impedance, the earth-return parameters (resistance and reactance) for numerous types of earth soil were computed from the point of view of takes into account the longitudinal displacement currents using Wise modification of Carson integration. The most popular earth soil types in our region that takes into consideration in this research are clay, loamy, and sandy soils. In all cases under study, the effect of displacement currents is classified by using the ratio of displacement current density to resistive current density (denoted by k-ratio) that depends on the electromagnetic properties of each earth soil type. Hence, the behaviors of the earth-return parameters for each type of earth soil are mainly explained according to the k-ratio. This research displays how the calculated values of earth-return parameters were affected when the displacement currents were taken into consideration. As a result, the relative differences of these calculated values that got using Wise and Carson calculation methods become noticeable when the k-ratio is greater than 0.1 for all cases under study.