Study on Space Charge Behaviors and Trap Characteristics in LDPE/SiO2 under Thermal Aging

Space charge is a threat to cable insulation materials and polythene insulation gradually degrades in long service conditions. The degradation of low density polyethylene (LDPE) affects space charge formation, accumulation and dissipation, and the presence of space charge affects the performance of dielectric. This paper focuses on the space charge characteristics of LDPE/SiO2 nanocomposites under thermal aging. The SiO2 nanoparticles were added into LDPE matrix with single mass concentration 5wt%, and the LDPE and LDPE/SiO2 samples were aged at a hot spot temperature (90 degrees C). During thermal aging, the space charge distribution was measured at a regular interval (0, 10, 20, and 30 days) at room temperature. And the pulse electro-acoustic (PEA) method was used for space charge measurement. It was suggested that SiO2 nano-fillers increased the density and depth of traps in LDPE/SiO2 nanocomposites, and the LDPE/SiO2 samples had a certain anti-thermal aging ability at the initial aging stage. In addition, thermal aging changed the microstructure of LDPE materials, produced many chemical defects, and also increased the density and depth of traps. Generally, long term thermal aging had significant influence on the space charge behaviors of polyethylene materials, and appropriately filling SiO2 nanoparticles could delay the degradation of LDPE insulation materials.