Electrical network simulations are currently very important to the electricity sector. A major benefit from simulations is to permit a deeper insight into faulty network situations, that otherwise could eventually pass unnoticed. Currently, there are many algorithms that simulate linear networks, which comprise the majority of the tests done in a typical network, when subject to normal situations. However, there are large consumers, whose loads are nonlinear. These loads represent large influences to their power feeding network. Thus, it becomes necessary to model this nonlinear sub network so it can be inserted into the electrical network simulator. The purpose of this work is to develop a formulation approach for the nonlinear state equations that represents a nonlinear electrical network. The formulation of the network is, in this case, an essential part of the solution, since there are currently algorithms capable of solving nonlinear differential equations, like the ones that will be studied in this work.