PhD Colloquium of Sounak Nandi

Thesis Title: Experimental and Theoretical Investigations on High Voltage Polymeric Insulators

Research Supervisor: Dr Subba Reddy B

Date and Time: Thursday 30th June 2022, 3.00 pm

Venue: Online. Click here to join the meeting

Abstract: High Voltage Ceramic and glass Insulators are 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 in service.

The primary objective of the investigation relates to the performance of silicon rubber/polymer insulator under various climatic conditions, both experimentally and comprehend theoretically. 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 extreme high temperature conditions were attempted experimentally and their performance evaluated. During experimentation the leakage current was continuously monitored also material analysis which is very important factor and essential to correlate with the morphological changes of the insulator surface was studied. The experimental investigations demonstrate that there is a need to conduct multi-stress experimentation under specific climatic conditions before the Insulators are being installed in the field.

The next portion of the theses work deals with failure mechanism of 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/DC voltages. Further, experimental Investigations are performed on FRP Rods to analyse the behaviour witnessed like the field failures reported on Silicon rubber Insulators.

Condition monitoring of dielectric surfaces is very important; hence it was felt necessary to analyse 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, later Empirical Mode Decomposition is also used for understanding leakage current and implied degradation under minimal data condition.

Subsequently, Surface electric field of insulators exposed to HVDC is studied considering the temporal boundary conditions which may arise due to the capacitive-resistive transients, some experimental investigations are also conducted to compare the simulated results.

The last portion of the thesis emphases on the study of bulk conductivity of polymer material. The Electric Field dependence of conductivity on the application of voltage and subsequent space charge distribution is attempted.

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