Unsynchronized parameter free fault location scheme for hybrid transmission line

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This paper proposes a new unsynchronized parameter-free fault location scheme for transmission lines (an overhead line (OHL) combined with an underground cable (UGC)). Utilizing unsynchronized measurements at both ends, the proposed method accurately locates faults without requiring OHL and UGC parameters. Therefore, the variation of OHL and UGC parameters values do not affect its accuracy. In this method, first using distributed line model for UGC and OHL, the fault location problem is converted into a system of nonlinear equations problem according to both pre-fault and fault measurements. Then, using a novel algorithm, the system of nonlinear equations is solved. This algorithm consists of two stages which in the first one, the system of nonlinear equations is converted into an optimization problem and in the next stage, using the first stage results, the problem is solved by a modified Newton method. Simulation results performed by MATLAB, verify the high accuracy of the proposed method in determining the fault location (whether in UGC or in OHL). In these simulations, it is shown that the proposed method is independent of the fault resistance, synchronization angle, and fault type and consequently, is superior to the existing methods. Moreover, the simulation results confirm the ability and efficiency of the proposed model in estimating OHL and UGC parameters.