Semidiscretization may act like a deregularization

In electrical circuit simulation, a refined network approach is used to describe secondary and parasitic effects. This ansatz yields initial-boundary value problems of mixed partial-differential and differential-algebraic equations, so-called PDAE systems. One requirement for method-of-lines applications is that the analytical properties of the approximative DAE system are consistent with the original PDAE system. Especially, both should show the same sensitivity w.r.t. initial and boundary data. It is already known in the literature that semidiscretization may act like a regularization, i.e. the approximate DAE system is less sensitive than the PDAE model. Considering PDAE network models for interconnected electrical circuits, we show that the opposite can be true: semidiscretization may act like a deregularization of a PDAE network model, if the method-of-lines approach is not consistent with the information flow along characteristics.