Testing and modelling nanostructured insulation for capacitor and cables used for storage and delivery of electrical energy

The measurement of partial discharges (PD) is a commonly used tool to evaluate the healthiness of electrical insulation materials in high voltage systems such as HVDC cables. PD measurement is an important non-destructive test from predictive maintenance and asset management of high voltage equipment point of view which its activity can lead to premature failure. Modelling PD characteristics such as PD charge amplitude, PD repetition rate and partial discharge inception voltage (PDIV) is performed to provide an effective fundamental tool for the development of reliable quality control, commissioning tests and diagnostics procedures. In addition, a theoretical and analytical PD model can help in planning tests and evaluating the likelihood and meaningfulness of test data. In this PhD thesis PD characteristics such as charge amplitude, repetition rate and PDIV are modelled base on PD RC equivalent circuit from AC to DC. The PD models were validated against experimental data obtained from laboratory testing on multilayer specimens at University of Bologna. The PDIV model under DC applying voltage was also validated after performing PD measurements on MV cable as a function of different temperatures (loads) in Technical University of Berlin. Then, the PD models were used to design a real HVDC insulation system to endure electrical and thermal stresses under operation using COMSOL Multiphysics simulations. Finally, the effect of adding nano Silica with different functionalization to cable grade polymeric materials on electric and dielectric properties such as space charge, electrical conductivity, dielectric strength, and life test were investigated and evaluated experimentally.