The project deals with the development of an SW application enabling the use of data from phasor measurement unit (PMU), which are installed both at the medium voltage level (reclosers, intelligent section disconnectors) and on the low-voltage side of selected distribution transformers. The project is relatively unique, as the installation of similar monitors is not common, however, it can be expected in the future development of distribution systems. The developed application will be designed for analysis/control of operation before reconfiguration of the medium voltage (MV) system, especially in the case of interconnection of two radially supplied feeders (e.g. when looping feeders during fault localization, etc.). The user interface will also allow the display of the relevant part of the MV system on a map, and to assess the voltage condition between selected measuring points. A module for estimating circular power flows, that would arise after the switching of a selected disconnector interconnecting two separate areas of the MV system, will also be developed for the needs of this application. Thanks to its specific functions, the developed tool will contribute to increasing the operational reliability, operability, observability and security of distribution network. This will support the further development of distribution systems and the implementation of smart grid concepts.