Voltage and current inversion challenges when protecting series-compensated lines — A case study

In order to increase power transfer capabilities, Idaho Power is upgrading two existing 230 kV series-compensated transmission lines from 28 percent compensation to 70 percent compensation. Protecting series-compensated lines is both a science and an art. This paper discusses the voltage and current inversion aspect of series-compensated lines where very little literature is available. A voltage inversion will challenge the security and dependability of both the directional and distance protection elements, whereas a current inversion will challenge the directional, distance, and differential protection elements. This paper will endeavor to add to the literature regarding how to adequately protect seriescompensated lines where the possibility of current inversion exists. Using series compensation to increase power transfer capabilities of transmission paths requires advanced simulation tools to ensure the reliability of line protection systems. This paper describes how to leverage transient simulation tools and a Real Time Digital Simulator to develop and verify optimized protection settings for series-compensated transmission lines prone to current inversion.