Juba5723 is actually singular (not just numerically singular). The rest appear to have really bad condition numbers; unclear whether they are singular in real life, or just numerically very sensitive. As they are often used to test algorithms designed for stable systems, we should add alternative shifted problems. See also https://morwiki.mpi-magdeburg.mpg.de/morwiki/index.php/Power_system_examples -- K. Lund + J. Saak
Many of the power systems have exactly 0 D terms that are stored as empty sparse structures. For the benchmarking tool and database, these have been deleted, and the systems are marked as lacking a D component. -- K. Lund