Silicone rubber (SR) insulators have been coated with different concentrations of NaCl to study the contamination level adopting laser-induced breakdown spectroscopy (LIBS) analysis. An elemental study of LIBS spectral data has identified the sodium peaks, thereby indicating the presence of salt deposits. A regression coefficient is used for a better understanding of the direct correlation between the salt deposit density (SDD) and the normalized intensity ratio, at various standoff distances. A marginal decrement in the normalized intensity ratio of the sodium peaks has been noticed in the case of readings taken at morning and midday, compared to those taken at night at different SDD values and different energies of the laser pulse. With increase in SDD, the intensity distribution characteristics have a right shift on the intensity scale. The polluted SR specimens are successfully classified by employing artificial neural network technique. Overall, the LIBS method is successful in identifying the variations in the salt deposition on the surface of the insulator, even at far distances of 15 m and at any time of the day.

Influence of Standoff Distance and Sunlight on Detection of Pollution Deposits on Silicone Rubber Insulators Adopting Remote LIBS Analysis

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.

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

The effect of corona aging on the surface potential dynamics and charge trap characteristics of silicone rubber alumina nanocomposite are examined using surface potential decay measurement. The aging was carried out by exposing the specimens to corona stress generated by a high-frequency AC multi needle-plane electrode system. The results show that the addition of alumina filler increases the surface potential decay time and maximum trap energy. A reduction in trap depth is observed with the corona aging, and the addition of alumina filler limits the degradation and change in charge trap distribution. The results of an analysis of the space charge behavior of different nanocomposites and their comparison are presented. The space charge variation analysis was carried out under the applied electric field of 20 kV/mm at room temperature using the pulsed electro-acoustic technique (PEA). Based on the results, the charge density, electric field, and charge trap distribution were deduced. It is concluded that the space charge concentration and enhancement in the electric field of the aged material increases with aging duration and it is maximum in the case of 60 min corona-aged pure silicone rubber. Analysis of the recovery of the charge dynamics of the sample after corona discharges at the different time intervals shows that the recovery of trap distribution is faster for a virgin sample and slower for the sample with 5 wt% of alumina. 

Parvathy Ganesh

Papers

Study on water droplet initiated discharges and charge trap characteristics of laser textured silicone rubber nanocomposites

Investigation of water droplet-initiated discharges on laser textured silicone nano-micro composites using UHF and fluorescent fibre techniques