Enhancement of Corona Onset Voltage Using PI/MWCNT Nanocomposite on HV Conductor

Ionization of air around the surface of the ac transmission line results in corona discharge, a form of plasma. In this proposed article, the effect of corona discharge in terms of corona loss (CL) due to the application of high voltage has been investigated using a specially designed small indoor corona cage. Initially, CL is measured for a 12-mm-diameter solid aluminum bare conductor (Al) and later steps are taken to suppress CL by coating the surface of Al conductor with polyimide (PI), polyimide/multiwalled carbon nanotube (PI/MWCNT) nanocomposites. PI/MWCNT is synthesized and characterized by permittivity and conductivity. The impact of MWCNT on CL reduction is realized by loading it in different weight percentage as 1 wt%, 3 wt%, and 10 wt% in PI. Maximum reduction of CL is observed at the electric field (E -field) of 25 kV/cm with 5.23%, 13.06%, 15.76%, and 23.53% for PI, 1 wt%, 3 wt%, and 10 wt% of PI/MWCNT-coated conductors, respectively. Corona onset voltage for bare and coated conductors is analyzed using quadratic law. Equivalent circuit parameters such as dynamic leakage conductance, geometric capacitance, and nonlinear capacitance for Al conductor-cage configuration are extracted from the experimental results.