Objectives
- To simulate electric field and potential distribution on glass disc insulator for the varying voltage stress and electrical conductivity.
- To perform a thermal assessment of the porcelain disc insulator and measure the spot temperature and corresponding corona inception and breakdown voltage.
To test the breakdown strength of the porcelain disc insulator at varying surface pollution scenarios. - To study partial discharge (PD) activity associated with pollution variation and ways to narrow down PD level on 24 kV polymer insulator.
Bikash Kafle
Masters by Research Student
bikashkafle98@gmail.com
Batch: 2021
Outcomes:
The study delves into the nuanced performance dynamics of insulators under dynamic surface conditions and varying voltage stress, yielding crucial insights that contribute to the understanding of their behavior within distribution networks. In the context of glass disc insulators, the research underscores the pronounced influence of applied voltage stress on the distribution of electric potential and field intensity. Notably, the cap region emerges as a susceptible area for electrical discharge initiation due to a higher concentration of the electric field.
Transitioning to porcelain disc insulators, thermal simulations and experiments reveal non-uniform temperature distributions, with the highest temperature recorded nearly 1℃ higher than the radiation temperature for constant heat rate in the pin of porcelain disc. For a significant increase in heat rate, up to 500 W, there is a temperature spike of 11.88℃, conducive to the condensation process within the insulator. With post-flashover, the temperature distribution in
porcelain insulators remains notably elevated, suggesting a substantial transformation during flashover, potentially leading to the formation of cracks and pores. Moreover, the research identifies the impact of temporary overvoltage in causing early discharge, leaving behind conductive paths for leakage current.
Comparative analysis of flashover strength decline in porcelain disc insulators under stationary
moisture and rainfall conditions reveals heightened vulnerability in the presence of rainfall. Additionally, rainfall is found to increase corona inception voltage, particularly in the proximity of pin and cap of the disc. More, the decline of both corona and flashover strength of disc insulators depends on pollutant material and its surface state.
The investigation extends to polymer insulators, highlighting a direct correlation between frequent voltage stress and partial discharge magnitude. Notably, even after reducing voltage stress from 160% to 120% of the rated voltage, partial discharge effects persist, indicating a lasting impact on insulator performance. Surface treatments with silicone are identified as effective in reducing partial discharge activity, offering a potential avenue for enhancing insulation performance. In conclusion, these results provide valuable insights into the intricate dynamics of insulator performance, considering both thermal and dielectric factors.
Supervisors
Assoc. Prof. Brijesh Adhikary
Associate Dean Department of Electrical and Electronics Engineering
School of Engineering, Kathmandu University
Assoc. Prof. Elin Fjeld Department of Electrical Engineering, Information Technology and Cybernetics
Faculty of Technology, Natural Sciences and Maritime Sciences
University of South-Eastern Norway