Mosaic Packing to Visualize Large-Scale Electric Grid Data

For large power systems, a continual challenge is to display wide-area data in a way that maximizes human users' situational awareness. This paper describes a new visualization technique that draws a mosaic of colored tiles to represent multiple data fields for electric grid objects, arranged to preserve geographic context. The key problem in creating these diagrams is packing the tiles onto the display space, minimizing the total displacement while forbidding overlaps. This paper formulates that problem and presents a horizontal-packing algorithm which is able to produce a feasible, quality solution at an interactive time scale. Illustrative examples are shown for using mosaics to monitor wide-area generator status and dispatch, bus voltages, and line and transformer limits. Mosaics can be customized in numerous ways to show different aspects of the system state, providing for human users a simultaneous sense of the wide-area summary, regional trends, and prominent outliers.