Download Influence of Grounded Back Electrode on AC Creepage Breakdown

School of Electrical, Computer and Energy Engineering
M.S. Final Oral Defense
Influence of Grounded Back Electrode on AC Creepage Breakdown Characteristics
by
Jiajun Liu
April 11, 2014
3 pm
ERC 490
Committee:
Dr. George Karady (chair)
Dr. Raja Ayyanar
Dr. Keith Holbert
Abstract
This thesis focuses on the influence of grounded back electrode on the breakdown
characteristics. With growing high voltage transmission grid, the reliability of the high
voltage devices attracts more attention than before. Insulation with grounded back
electrode is a common type of insulation which is adopted in many high voltage power
devices. While most of the power equipment work under AC voltage, most of the
research on back electrode is focused on the DC voltage. Therefore, it is necessary to
deeply investigate the influence of back electrode under AC applied voltage.
To investigate the influence of back electrode, the research is separated into two
phases, which are the experiment phase and the electric field analysis phase. In the
experiments, the breakdown voltages for both with and without back electrode are
obtained. The experimental results indicate that the grounded back electrode does have
impact on the breakdown characteristics. Then with the breakdown voltage, based on real
experiment model, the electric field is analyzed using computer software. From the field
simulation result, it is found that the back electrode also influences the electric field
distribution. The internal relationship between the electric field and breakdown voltage is
the key to explain all the results and phenomena observed during the experiment.
Additionally, the influence of insulation barrier on breakdown is also investigated.
Compared to the case without ground electrode, inserting barrier into the gap can more
significantly improve breakdown voltage.