272 / 2018-09-25 09:49:38

Elemental Analysis of Aged Composite Insulators Based on Laser Induced Breakdown Spectroscopy

silicone rubber insulators，Laser-induced breakdown spectroscopy（LIBS），Ageing，elemental analysis

Silicone rubber insulators have been widely used in power systems due to their light weight, high mechanical strength, good hydrophobicity and hydrophobicity migration, excellent flashover resistance and other advantages. However, silicone rubber, as an organic synthetic material, will inevitably aging under the action of electric field, ultraviolet radiation, acid rain and pollution for a long time, thus affecting the performance of insulators, and even cause flashover, string dropping and other failures when serious, resulting in hidden dangers to the safe and stable operation of the power grid. Therefore, it is very important to accurately evaluate the aging state of composite insulators and timely discover insulation defects to ensure the safe operation of power system. Aging of edge materials can be analyzed by measuring their surface morphology, element composition and content. Laser-induced breakdown spectroscopy (LIBS) is a fast and in-situ spectrochemical method for the determination of elements in a variety of states (solid, liquid and gaseous), which can realize non-destructive (or micro-damage) and multi-element simultaneous and rapid composition analysis. Based on these advantages, LIBS technology has been widely used in industrial processing, environmental chemical monitoring, biomedicine, archaeology, aerospace, agriculture and food and other fields. The new portable laser induced breakdown spectrometer developed at present can realize the scene survey . Therefore, it has very good application potential in the field detection of insulator aging degree. In this paper, the plasma temperature is calculated by Boltzmann plane method and the electron density is calculated by Stark broadening. The results show that the plasma excited by pulsed laser bombardment of silicone rubber insulator is in a local thermal equilibrium (LTE) state under the experimental conditions studied in this paper, and can be quantitatively analyzed by spectral data. Then the plasma emission spectra of the new and three field samples were analyzed. The relative elements corresponding to the characteristic peaks in the spectra could be obtained by comparing with the atomic standard and technology database (NIST). Then the plasma emission spectra of the new and three field samples were analyzed. The relative elements corresponding to the characteristic peaks in the spectra could be obtained by comparing with the atomic standard and technology database (NIST). Compared with the new silicone rubber samples, the on-site running silicone rubber samples have more elements than the new ones because of the contamination on the surface and the long-term permeation of contamination on the surface. There are obvious differences in element strength among three kinds of aging samples, among which K, Na, Fe and Ca are the most significant. With the increase of operation years, the contents of surface dirty elements increased significantly. In order to evaluate the aging status of composite insulators more accurately, we further analyzed the variation of matrix elements, impurity elements and contamination elements with the number of pulsed bombardment. It was found that the three types of aging insulators were from surface to interior under different bombardment pulses. The content of Al, Fe, Ca, K and other elements in the aging insulator showed a rapid decline trend under the first five pulses bombardment, and the content of elements tended to be stable after five pulses bombardment. However, the bombardment pulses were different when the aging degree tended to be stable. The aging time was about 7 times in 8 years, 5 times in 5 years and 3 times in 3 years. The contents of Al and Fe of new insulators are relatively stable from surface to interior. Therefore, it is suggested that the aging degree of running insulators can be evaluated by the variation of matrix elements, impurity elements and contamination elements with the number of pulse bombardment.