AC overhead lines through their constructive asymmetry causes significant unbalance of currents and asymmetry of voltages on the three phases of the network. These unbalances of the operating conditions are even higher as the lines has greater lengths and the transported powers are higher and is therefore primarily characteristic for the transmission lines. The article presents the results of numerical assessment of the effects of impedance and admittance asymmetries for an untransposed double circuit overhead line, having 220 kV rated voltage. For this goal there were used the phase impedances respectively admittances matrices, determined by Kron's reduction method, applied to the primitive admittances respectively impedances matrices, the construction of which is based on the modified Carson's equations. The paper presents the results for two specific operating conditions: no load and natural load.