  An open source software package for performing dynamic RMS simulation of
small to medium-sized power systems is presented, written entirely in the
Python programming language. The main objective is to facilitate fast
prototyping of new wide area monitoring, control and protection applications
for the future power system by enabling seamless integration with other tools
available for Python in the open source community, e.g. for signal processing,
artificial intelligence, communication protocols etc. The focus is thus
transparency and expandability rather than computational efficiency and
performance. The main purpose of this paper, besides presenting the code and
some results, is to share interesting experiences with the power system
community, and thus stimulate wider use and further development. Two
interesting conclusions at the current stage of development are as follows:
First, the simulation code is fast enough to emulate real-time simulation for
small and medium-size grids with a time step of 5 ms, and allows for
interactive feedback from the user during the simulation. Second, the
simulation code can be uploaded to an online Python interpreter, edited, run
and shared with anyone with a compatible internet browser. Based on this, we
believe that the presented simulation code could be a valuable tool, both for
researchers in early stages of prototyping real-time applications, and in the
educational setting, for students developing intuition for concepts and
phenomena through real-time interaction with a running power system model.
