Q:   Why does the fault simulation sometimes take so long after I added many IBR models to my network model?

A:   Each nonlinear IBR model in the network adds a nonlinear equation to the solution. The incremental computational burden due to nonlinear iterations grows significantly with the number of IBR models.  Even though a network model with 50 IBR models may solve quickly, increasing to 150 IBR models may require significantly more than triple the simulation time. We are working on techniques to improve solution speed for large networks with many IBR models.