Modeling Zero Impedance Lines in Power System Applications

This paper presents a topological algorithm for determining observability of the zero-impedance line flows. It also determines whether the observable zero impedance line flow should be modeled as state variable or eliminated by contracting the line into a single node called super bus. Methodology to calculate flows on the contracted zero-impedance lines is also presented. Due to its general nature, the proposed approach is applicable to the state estimation, power flow and security analysis software. Several modeling features whose implementation has improved the reliability of the Energy Management System are described.