In this paper we analyze the impact of systematic errors in TRL calibration on the extracted equivalent circuit parameters of the measured device. We mainly focus on extraction of RLCG-parameters (resistance, inductance, capacitance, conductance) of transmission lines and inductors. We show how the uncertainties in measured S-parameters and in determined characteristic impedance propagate into RLCG-parameters. In particular, we emphasize the importance and the difficulty of an accurate determination of the imaginary part of characteristic impedance. We use the results of our sensitivity analysis to estimate the accuracy of RLCG-parameter extraction of a coplanar transmission line and a 2.2 nH spiral inductor. Finally, we propose an alternative method for determination of certain RLCG-parameters based on causal relationships.