This paper presents a complete scheme for protection of transmission lines, including fault detection, fault classification as well as fault location. The fault location module utilizes the modeling of transmission lines through their differential equations. The differential equation for the line is solved having its resistence and inductance as parameters. In this approach there is no need for the algorithm inputs to be pure sinusoidal waves, allowing the presence of harmonics and DC component in the line as part of the solution to the problem. The software ATP was utilized for the modeling of the eletric system under study as well as for data collecting for analysis and test. The direct use of the differential equation do not give an acceptable estimation as far as digital relays are concerned because they have convergence times over two cycles. In this sense, a 5th order median filter was utilized, providing faster diagnosis for the fault location estimation. For the fault types tested, the estimation for the fault location utilizing line parameters has shown itself highly satisfactory for protection purposes. This work has shown that the algorithm outputs converge in less than one and a half cycles after the fault occurrence, presenting a much faster response for digital relays.
System Protection; Digital Protection; Diferential Equation
