Fault Location in Series Compensated Transmission Lines

Due to the integration of modern technology such as electric vehicles, the emphasis is expected to shift from mechanical to electric power. Therefore, the need of increasing the power transmission capacity of the electric grid gets highlighted. Since, the construction of transmission lines is a tedious task owing to legalities, environmental impacts and high costs, the series compensated transmission lines are gaining popularity due to lesser costs and faster construction time. The series capacitor compensated transmission lines are very crucial lines due to the greater power being transmitted through them. Therefore, an accurate fault location becomes a prerequisite for limiting the loss of revenue and power continuity. However, fault location in series capacitor compensated transmission lines face multifaceted challenges due to the variety of factors including but not limited to the presence of sub-synchronous frequency components in the measured signals, interdependence of the fault current level and operation of series capacitor protection unit, presence of non-linear element, i.e., metal-oxide varistor as a part of series capacitor protection unit and dependence of the existing fault location algorithms on zero-sequence parameters of the series capacitor compensated transmission line which cannot be estimated accurately. In this thesis, the task of fault location in series capacitor compensated transmission lines has been explored in detail covering the entire spectrum of challenges starting from signal processing to how to obtain the fault location value with the least amount of uncertainty. In this thesis, firstly a phasor estimation technique called the Enhanced Prony-DFT based on analysis in discrete-time domain has been proposed which identifies and completely removes the transients present in the measured signal, thus yielding highly consistent and accurate phasors. Fault location in series compensated transmission line is used as metric for the verification of the accuracy of estimated phasors. Thereafter, the focus is shifted towards the fault location algorithms for series compensated transmission lines. All the studies found in literature have considered the location of series capacitor in the middle of the transmission line. Therefore, secondly the configuration of series compensated line when series capacitor is located at one of its ends is also studied. It is discovered that the well-known fault location algorithms for series compensated transmission lines yield significantly higher errors when the series capacitor is located at the end of a transmission line. Therefore, rendering the already existing fault location algorithms useless for practical applications. Thirdly, the impact of series capacitor protection unit on fault location has been investigated which leads to a significant observation that MOV may get bypassed before the interruption of the fault for numerous fault scenarios. Therefore, a new complimentary fault location technique is proposed which provides more precise and accurate fault location results for the fault scenarios where MOV gets bypassed before fault interruption. The proposed complimentary technique is relatively more immune to the adverse effects of measurement errors and errors in the estimation of zero sequence components as compared to the existing techniques.