Thermal-Mechanical Accelerated Aging Tests of XLPO Insulation Based Photovoltaic Cables: Inverse Aging Behavior

The output power of photovoltaic (PV) systems relies greatly on their DC cable systems as these cables provide the link between the main PV systems components, solar modules, inverters, batteries, and charge controllers. These cable systems are exposed to harsh operating conditions such as ultraviolet radiation, thermal, electrical, and mechanical stresses. Thus, the cables’ insulation degrades, and their functionality is not assured. In this research, samples of DC PV cables have been exposed to combined simultaneous thermal and mechanical stresses for 258, 396, 636, 876, 1000, and 1120 hours. While the cable samples were placed in an air circulating oven at 120 °C, they have been bent on a mandrel of 6 cm diameter. The impact of the thermal-mechanical aging stresses on the cables’ insulation integrity has been explored by implementing the dielectric spectroscopy technique and the Shore D hardness measurement. The real and imaginary parts of permittivity presented a non-monotonic behavior with aging. Besides, the Shore D hardness increased after 396, and 636 aging hours. In contrast, it decreased after the subsequent aging cycles, 876, 1000, and 1120 hours. The obtained results suggest that the XLPO could recover its mechanical properties while being exposed to an elevated temperature for an extended period.