Effects of Dynamic Fault Impedance Variation on Accuracy of Fault Location Estimation for Series Compensated Transmission Lines

This paper investigates and compares the effects of dynamic fault impendence variation on the accuracy of estimating location of faults on series compensated transmission lines, using a novel fault location algorithm based on the measurement of instantaneous signals, derived from both ends of high voltage transmission lines. In order to estimate fault location accurately, it is necessary to compute precisely the voltage drops in series compensation units during the fault. However, the methods available for such computations induce considerable errors in fault location estimation algorithms, due to the complexity of the series compensation units. Furthermore, in these methods, fault impedance has been assumed fixed during the fault. In this paper, the fault impedance used in the models has been considered variable and its dynamic inclusion in the fault estimation algorithm has been investigated. The developed algorithm has been tested using the ATP software with 400KV, 300km long transmission line interconnecting two equivalent power systems. The algorithm performed well with fixed fault impedance. However, by representing the fault impedance in its dynamic form, the accuracy of the algorithm has not changed. Such simulation of the fault impedance is more accurate than the assumption of fixed values. The presented results show that the new algorithm is capable to estimate accurately the location of faults under different conditions, including dynamic fault impedance. The paper will discuss the results obtained and conclusion will be made on the novel scheme for fault location estimation on series compensated high voltage transmission lines. Key-Words: Fault location, Fault impedance, Transmission lines, Series compensation, Instantaneous signals, ATP software