Abstract
To develop compact and relatively low maintenance demanding high voltage transmission systems, polymeric insulators are widely replacing traditionally used insulators for the past several decades. Further efforts focusing on enhancing their antiaging performance by adding fillers to increase the reliability of power systems are being made through extensive research globally. Among the causes of degradation, corona discharge is considered of great concern and needs to be investigated at length. Toward that end, several types of high-temperature vulcanized silicone rubber (HTV-SiR) were reinforced with varying quantities of nano-sized boron nitride (BN) and silicon carbide (SiC) fillers are evaluated in this study. Test samples with different formulations are fabricated and exposed to alternating current (AC) corona discharge for a duration of 72 h. Thereafter, the induced modifications in their surface characteristics and bulk properties are assessed using several diagnostic and complementary techniques involving measurements of partial discharge and volume current, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR) spectroscopy. The volume current is recorded using a standardized three-electrode system at different levels of the test voltage and ambient temperature in an attempt to evaluate its dependence on the electric field and temperature. As a result of the conducted study and allied analysis, it is reported that the damaging impact of corona retards more in the case of loading HTV-SiR with nano-sized particles of BN as compared to SiC. The obtained FTIR spectra demonstrate an increase in the transmittance intensity of principal peaks in the aged samples, being higher in the unfilled SiR than its filled counterparts. It is further revealed that exposure of the studied samples to corona discharge elevates their volume current possibly due to charge injection and space charge effect, particularly at higher temperatures and strong electric field.