This research report describes an activity that is part of research for improving the reliability of the electricity system and in particular is part of project 1.4 ‘Components and materials for safety and resilience’. Under the pressure of the penetration of renewable energy, the electricity system has become increasingly widespread and interconnected. One of the strategies to improve its reliability is to migrate towards predictive maintenance that can anticipate failures. Among the grid components whose maintenance is more difficult to plan are certainly the insulating elements and especially those made of polymer matrix composites. These insulators are widely used in the grid and they are increasingly preferred to other insulation technologies such as paper-oil or SF6 gas. Failures have multiple causes; however, in alternating current power supply, the most frequent ones are partial discharges.

The aim of this research activity is to better understand the degradation mechanisms related to partial discharges and lay the foundations for predicting their evolution. This aim is pursued through the development of simulation codes based on first principles and the development of measurement systems that can be directly correlated to the developed model, since market available measurement systems do not always lend themselves to a direct correlation.

In particular, four main results have been obtained in this research line. The first one was the increase in performance of a previously developed partial discharge simulation code, by optimising its computational aspects. Therefore, the code is able to deal with more realistic cases.

The second result was the development of a chemical database that better reproduces the secondary emission process from metal and plastic surfaces. These parameters directly influence the results of the simulation code described above and, for this reason, their evaluation is of primary interest. The estimation techniques used are based on quantum chemistry computation (DFT).

The third result obtained was the construction of a first measuring head of an optical system for measuring the distortion of the electric field generated by partial discharge events. The first prototype, obtained in previous reference periods, was tested in realistic conditions and then a new measuring head was designed that significantly improves performance. Future developments will involve the realisation of electronic and software components with controls for this sensor.

The fourth result was the planning of a measurement campaign to characterise the partial discharge process in resin-insulated transformers in order to outline the problems and establish a subsequent investigation campaign.