Insights into the L-index Voltage Stability Assessment; A Qualitative Approach

In this work, we investigate observed limitations that render the L-index voltage stability indicator unreliable for accurate assessment of the maximum power transfer margin. The approach favors a qualitative assessment over a quantitative system study. We observe two problems, guided by examples on a minimal system, with parallels on the IEEE 14-bus system: underreported Thevenin impedance, resulting in an overestimation of the maximum power transfer, and overcorrected load transfer from the load bus to the critical bus. We conclude that these difficulties need to be addressed for a comprehensive solution.