Initially I demonstrated the power system and its principles, as I went further, I have discussed the review of gird in a power system and its capabilities and smart gird and its innovative idea if power grid which can be smartly coordinate the activities and how smart grid uses computer technology to improve the communication, automation, and connectivity of various components of the power network. Moreover, I planned a grid of a medium voltage level and calculated all the transformers, circuit breakers, I calculated the cross-section and chose the wires for the designed grid. I have also calculated the short circuit current and operational currents for the switchgears