Study On The Aging Characteristics Of Composite Insulator Based On TSC

The aging of composite insulators has been one of the serious problems along with the increase of the installed number and the service years. And how to assess the aging state of composite insulators in service is of great importance to the reliability of transmission lines. In this thesis, the composite insulators in service were studied, which were installed under different service conditions like different service time and varied rated voltages. The primary investigation of aging characteristics of composite insulators had been carried out by various tests on samples of different service conditions including hydrophobicity test, Scanning Electron Microscopy (SEM) analysis, Fourier Transform Infrared Spectroscopy (FTIR) analysis and Thermally Stimulated Current (TSC) test.According to the hydrophobicity test results, the hydrophobicity of the sheds of composite insulators had partially lost. The hydrophobicity was almost completely lost after being immersed in water, but the hydrophobicity recovery was found with time extending. For samples with lighter aging degree, the hydrophobicity recovery was quite perfect, while for samples with greater aging degree, the hydrophobicity recovery was hardly achieved.The results of SEM and FTIR analysis of multiple composite insulators showed that there were a number of holes and cracks on the surface of sheds, the quantity would increase with the growing service time, and finally there were deep and wide cracks. The fracture of fundamental chains, side chains and some groups would be observed on the surface of sheds, which meant that the chemical structures of composited insulator had been destroyed. Moreover, the change of the internal groups was increased and the destruction of the chemical structures would be more severs along with the increase of service time.The TSC results indicated that the peak values and the corresponding internal space charge amounts became larger with the longer service time. Therefore, it could be drawn that the TSC characteristics would be one of the indexes of the service aging state of the sheds of composite insulators.Based on the comparison analysis of the previous tests, the hydrophobicity test could not reflect the true aging state of the service composite insulators, while the microscopic structure analysis of surface morphology (SEM and FTIR analysis) were incapable of conveniently establishing the quantization relationship with different service term of composite insulators. However, combining with the TSC characteristics, the aging state of composite insulator could be revealed quite well.The accomplishment of this thesis will help establishing a new method for evaluating the aging characteristics of composite insulators based on TSC characteristics of materials and a collective evaluating model for completing the aging properties of composite insulators.