Differential Equation Algorithm (DEA), which is used as an alternative method to Fourier and similar algorithms, is among the online parameter estimation algorithms used in transmission line protection. Pi or T equivalent circuit parameters (R, L and C) of the transmission line can be calculated efficiently by using the fundamental harmonic components of voltage and current. DEA is a general model-based parameter estimation method and it does not depend on the form of the signal (voltage/current). Due to this feature DEA provides an efficient parameter estimation. In addition to traditional trapezoidal DEA algorithm, Simpson 1/3, Simpson 3/8, Simpson 7, Medium Point, Forward Euler, Backward Euler, Runge-Kutta and Boolean algorithms were first proposed in this study and the parameter estimations were performed on an exemplary transmission line. Thusly, it is proven that alternative methods can be used effectively on relays as an algorithm to find the location of a fault in the line.