A medium voltage (MV) cable network is a substantial component of the distribution network. Present management of this grid segment is mainly based on the failure rate analysis, i.e., a rise in the number and kind of faults on the actual line means that its technical condition is getting worse. The efficiency of the power system is low and additional costs of repair works, supply interruption, difficulties in the investment planning and operation and maintenance works are necessary. The aim of the R&D works done in the realised project is to implement the management of the MV cable network based on the estimated condition of the individual cable line, obtained from diagnostic measurements. The diagnostic investigations of the cable lines are the reference. Many years of research work have led to the development of the Health Index based on diagnostic, technical and service data.