The goal of this model is to test the ability of a Modelica tool to handle a large number of cascading events, which are generated by a large sparse system of implicit linear equations. As such, it mimicks the structure of large power system networks with event-triggered current limiters and tap changers.
The current generator feeds a growing current into a DC network which is made by N+1 equal conductive loads, N of which are protected by breakers. The current thus spreads equally through each load whose breaker is closed.
The last breaker is triggered when the current goes above 1 A; as a consequence, the same total current is spread over a number of loads which is one less than before, so that the current on each load is higher. The maximum currents of the remaining M-1 breakers is selected so that each breaker opening causes the current of one (and only one more) more breaker to exceed its maximum value. As a consequence, a chain of events is triggered that eventually causes M breakers to open, one for each event iteration.
Summarizing, the model contains an O(N)-size sparse algebraic loop, N zero-crossing functions each involving one variable solved for in the algebraic loop, and is designed to trigger an event iteration loop with M iterations.