Experimental and Theoretical Investigations on High Voltage Polymeric Insulators

Abstract

High Voltage Ceramic and glass Insulators have been widely used by various transmission and distribution utilities for several decades across the globe. Recently composite or silicone rubber insulators have evolved and are now replacing ceramic/glass insulators due to their improved advantages; however, these Insulators suffer from degradation over a period of service. The first few chapters of the thesis deal with the study of silicon rubber/polymer insulators under various climatic conditions. Exhaustive experimental studies were conducted to understand the degradation of insulators under different climatic conditions which prevail in the Country. Studies on polymer insulators under sub-zero and under extremely high-temperature conditions were attempted experimentally to evaluate their performance. During experimentation, the leakage current was continuously monitored. Later, material analysis, which is a very important aspect and essential to correlate with the morphological changes of the insulator surface, was examined. The experimental investigations demonstrate that there is a need to conduct multi-stress experimentation under specific climatic conditions before the Insulators are installed in the field. The next portion of the thesis work deals with the failure mechanism of a Fibre Reinforced Plastic (FRP) Rod. Some portion of the work deals with mathematical analysis being extended to condition monitoring of dielectric surfaces and understanding the performance of FRP rods under high AC voltages. Further, experimental investigations are performed on FRP Rods to analyze the behaviour witnessed, as the field failures reported on Silicon rubber Insulators, interesting results are reported. Condition monitoring of dielectric surfaces is very important; hence it was felt necessary to analyze the field performance of transmission/ distribution composite Insulators. To understand further, a mathematical analysis based on Chaos has been evaluated for leakage current data and quantization of comparative degradation for a dielectric surface is presented. Later, Empirical Mode Decomposition is also used for understanding leakage current and implied degradation under minimal data conditions, and the results are analyzed and presented. Subsequently, the Surface electric field of insulators exposed to HVDC is studied considering the temporal boundary conditions which may arise due to the capacitive-resistive transients. The last portion of the thesis deals with a theoretical study of the bulk conductivity of polymer material. The Electric Field dependence of conductivity on the application of voltage and subsequent space charge distribution is attempted, and the results are analyzed and presented. In short, this thesis is a work where both experimental, simulation and theoretical studies pertaining to silicone rubber insulators are presented.