This article describes a reference data set for a representative Norwegian radial, medium voltage (MV) electric power distribution system operated at 22 kV. The data set is developed in the Norwegian research centre CINELDI and will in brief be referred to as the CINELDI MV reference system. Data for a real Norwegian distribution system were provided by a distribution grid company. The data have been anonymized and processed to obtain a simplified but still realistic grid model with 124 nodes. The first part of the data set describes the base version of the reference system that represents the present-day state of the grid, including information on topology, electrical parameters, and existing load points. The data set also comprises a load data set with load demand time series for a year with hourly resolution and scenarios for the possible long-term load development. These data describe an extended version of the reference system with information on possible new load points being added to the system in the future. A third part of the data set is data necessary for carrying out reliability of supply analyses for the system. The base version of the reference system described in this article can be extended to represent other types of distribution grids (e.g., with a ring topology). The reference grid can be used for assessing new methods and principles for distribution system operation and planning, including assessment of flexibility resources, active distribution grid measures, grid reinforcement planning, grid reinvestment planning, reliability of supply analysis, self-healing, etc.