Ricerc@Sapienza

During the summer periods of the last few years there have been unexpected increased numbers of failures of underground cable joints of the medium voltage (MV) network both of e-distribuzione and of other Italian electrical distributors. As a result of this, the University of Roma 'La Sapienza' and e-distribuzione started a cooperation with the aim to investigate on causes of such failures and for finding the most appropriate countermeasures in terms of improvement of technologies, operative procedures and operation.

One of the parameters that has to be considered in designing underground cables is the thermal resistivity of the soil along their routes. In fact, the ampacity of the MV underground cables having different types of insulation is normally evaluated through the application of the IEC Standard 60287-x 'Electric cables - Calculation of the current rating'. This series of IEC Standard is formed of three parts as in the following: part 1: Formulae of ratings and power losses; part 2: Formulae for thermal resistance; part 3: Sections on operating conditions.