Experiment and Simulation of Temperature Effects on Partial Discharge and Electrical Treeing in XLPE Insulation

Crosslinked polyethylene (XLPE) is a crucial insulating material for cables. Partial discharge (PD) and electrical treeing are key parameters for characterizing the state of XLPE. Studies have found that the temperature affects the PD and electrical treeing of XLPE. Yet, the theoretical analysis of this phenomenon is not sufficiently elaborated in-depth. To address this, this article constructs a testing platform for XLPE PD and electrical treeing, observing the development patterns of PD and electrical treeing at $50~^{\circ }$ C, $70~^{\circ }$ C, and $90~^{\circ }$ C. Experiments indicate that rising temperatures result in lower inception voltages for PDs, more frequent discharges, faster electrical tree growth, and a reduction in branching. To explore the theoretical mechanism behind the impact of temperature, this article first calculates the conductivity of cavities under different temperature conditions on a microscale using a fluid simulation model and measures the dielectric constant of XLPE at various temperatures. Then, combining a macroscale finite element simulation model, the effect of temperature on the frequency of PD occurrences is analyzed through multiscale simulation analysis. Subsequently, considering the effects of dielectric constant, critical breakdown strength, and dielectric loss tan $\delta $ at different temperatures, the phase field model is used to depict the growth of electrical trees under various temperatures. Ultimately, the simulation results show that an increase in temperature leads to a lower discharge field strength, an increase in the number of PDs, a faster growth rate of electrical trees, and a reduction in branching, which corresponds to and explains the experimental results. Temperature dependency of dielectric constant and critical breakdown strength are the key factors for the PD and electrical tree development patterns under different temperatures separately.