Transmission lines are a vital yet often over simplified component in a power system. While digital power system models use impedance values to represent both the balanced and unbalanced states of a transmission line, these values are obtained from formulas using many simplifying assumptions. These values serve as accurate representations of a transmission line within the constraints of the assumptions. However, when conditions exist in a transmission line that are not accounted for in the modeling assumptions, significant error can result. Synchronized phasor measurement is a proven technology that has the ability to measure power system parameters and perform calculations in real time at speeds that were previously not possible. These real time calculations can be used to validate power system models, and predict dangerous transmission line conditions as system loading changes. Additionally, if transmission lines are closely monitored in real time, the ability to dynamically rate the transmission line's capacity becomes possible. This thesis work focuses on the use of a simplified calculation to determine transmission line positive sequence impedance. The benefit of using simplified calculations is that real time information can be analyzed without the additional overhead of processing vast amounts of historical data sets and critical loading events can be identified in time to take corrective action. Through the use of a minimal sample interval where all measurements represent the same system conditions, existing statistical methods may be readily applied and actual line parameters determined. As such, this work will focus strongly on quantifying the minimum sample interval and calculating actual positive sequence line parameters.