Time Varying Electrical Load

I have a load profile of a transformer and want to model it as a load of the transformer. How do I go about it? Anyone familiar with the Simulink/Simpowersystem block execution technique could let me know if I have several such transformers connected to grid then at a particular instant are these profiles updated as load throughout the system (i.e parallel execution)or the solution of voltages is calculated serially going by one trafo after another?