BOLD ™: New Line Design Meets New Impedance Measurement Method

This paper describes impedance measurements conducted by American Electric Power (AEP) on a new 345 kV transmission project near Fort Wayne, Indiana, featuring an innovative high-capacity/high-efficiency compact line design trademarked BOLD™ (Breakthrough Overhead Line Design). Measurements were performed in cooperation with OMICRON Electronics Corporation (OMICRON), a provider of testing and diagnostic solutions, which developed a novel method and instrumentation employed in this application. Results revealed close agreement (1–3% difference) between the measured and analytically obtained positive-sequence impedances for the measured line. Differences in zero-sequence impedances were much larger (about 20%), reflecting the use of a generic assumption for earth resistivity in computing transmission line electrical characteristics. Accurate knowledge of line impedances can enhance the reliability of protection settings, thus minimizing the risk of relay misoperations. Also, it can advance the quality of power system models used in planning, engineering and operating studies, as mandated by NERC under Reliability Standard MOD-032-1.