Life and reliability estimation of DC-XLPE Cables under Type Test conditions using Bipolar Charge Transport model with parameters from the HEU-Newgen Project

High-voltage direct current (HVDC) cables are essential components for the future of global power transmission, enabling the efficient transfer of energy over distances that would be impractical for alternating current (AC) systems. Unlike AC cables, HVDC cables operate under a steady, unidirectional electrical stress, which affects their insulation performance and aging behavior. This makes their design and testing crucial for maintaining system reliability. A critical process for evaluating HVDC cable performance is the Type Test (TT), that compresses decades of operational aging into a shorter period by subjecting cables to combined electrical and thermal stresses in controlled conditions. Simulating these tests is extremely useful, as it enables engineers to study aging mechanisms, anticipate insulation failures, and refine cable designs in advance of going through costly and time-consuming physical testing. Conventional methods for estimating cable lifespan typically use simplified macroscopic conductivity models. However, these methods suffer some shortcomings and overlook the interactions between space charge dynamics and transient electric fields. This thesis introduces the application to TT simulations of the Bipolar Charge Transport (BCT) model, a microscopic approach for simulating electric field distributions within HVDC cable insulation. The BCT model accounts for charge injection, transport, and recombination processes, providing a more detailed representation of insulation behavior under high stress. Critical parameters, such as charge mobility and activation energies, are derived from the HEU-Newgen project, which provides a state-of the-art set of parameters for insulations employing cross-linked polyethylene for HVDC applications (DC-XLPE). A comparison is made between the BCT model and previously used methods, evaluating its ability to predict more accurately TT results, confirmed also by real test data.