Adaptive impedance relay for the protection of series compensated lines

Series capacitors provides a cost-efficient way to increase the transmission capacity per circuit of an existing transmission line. It also helps to increase the flexibilities in the load-flow distribution control and the stability levels of a power system. However, the series compensations of transmission lines are known to cause problems to the protection of these lines.; As the analysis in this thesis shows, series compensation mainly causes problems for non-pilot fast-relaying protection systems, such as an impedance type relay, but causes less problems for pilot protection systems. The severity of these problems caused by the series compensation for an impedance relay is determined by many factors: such as series capacitor's location (end-compensation or mid-compensation), relay PT location, series capacitor's protection circuit type. Some of these problems are easy to solve, which have been shown in the thesis. Among them, using impedance relays to protect a mid-compensated line is the most difficult one to solve.; An adaptive impedance relaying algorithm has been developed in this study to solve the protection of a mid-compensated line using impedance relays. In this thesis, a theoretical background of this adaptive algorithm was provided. The thesis also went on to analyze the feasibilities of this algorithm under different real situations. The simulation results of this study show that this adaptive algorithm can be used to solve the fast relaying problem of a mid-compensated line.