Communication network of the Smart Grid is intended to serve a numerous amount of applications of different types. Its complicated structure often requires a utilization of several communication technologies: wireless, cable, etc. Power line communication (PLC) also remains a challenging solution for usage in this area. The present paper is targeted to explore the communication protocol of UPA (Universal Powerline Association) technology - one of Broadband PLC (BB-PLC) solutions, which are used today in the Smart Grid. In the paper the test field measurements of this technology are summarized and the development of the UPA simulation model is described. Among this description one of the most important stages of the simulation model design, i.e. calibration with the measurement results, is explained. The obtained simulation model is intended be used as a part of the PLC network planning tool.