Power system software used for analysis and dynamic simulation and relay settings require accurate model parameters of different elements for precise results. For this, transmission line parameter verification is necessary at times, which changes due to atmospheric condition and aging. This paper presents a method for estimating the parameters of series compensated line online using synchronized time-domain data captured by the intelligent electronic devices at both ends of the line, which is free of the compensation model. The method uses traveling waves generated during disturbance to obtain the propagation constant of the line, which is used to estimate the resistance and the characteristic impedance of the line. Subsequently, the inductance and capacitance of the line are calculated. The proposed method is tested using PSCAD/EMTDC simulation data of an actual series compensated line in Indian power grid. Results demonstrate the accuracy of the proposed method.