Impact of Sunlight and Stand-Off Distance on Detection of Pollution Deposit on Silicone Rubber Insulators Adopting Remote LIBS

Silicone rubber insulators have been coated with different concentrations of NaCl in order to analyze their pollution performance using LIBS study. Elemental analysis of LIBS spectral peaks has been successful in identifying the sodium peaks, there by indicating the presence of salt deposits. Regression coefficient (R2) has been used as a performance parameter in correlating the ESDD and normalized intensity ratio. A direct correlation between ESDD and the normalized intensity ratio of LIBS spectral data is noticed with a regression coefficient value greater than 0.975 and RMSE value less than 0.07 for all standoff distances in the present study. The percentage reduction in the normalized intensity ratio of the peaks corresponding to Na I in case of morning and mid-day are less than 10% and 20% respectively, compared to night at different ESDD values and different energies of laser pulse. Overall, the LIBS technique is successful in identifying the variations in the salt deposit density on the insulator surface even at far distances of 15 m and at any time of the day.