School of Electrical, Computer and Energy Engineering
M.S. Final Oral Defense
Electric Potential and Field Calculation of HVDC Composite Insulators by Charge
Simulation Method
by
Jiahong He
November 21st, 2013
8:00 A.M.
ENGRC 490
Committee:
Dr. Ravi Gorur (chair)
Dr. Raja Ayyanar
Dr. Keith Holbert
Abstract
High Voltage Direct Current (HVDC) technology is being considered for several
long distance point-to-point overhead transmission lines, because of their lower losses
and higher transmission capability, when compared to AC systems. Insulators are used to
support and isolate the conductors mechanically and electrically. Composite insulators
are gaining popularity for both AC and DC lines, for the reasons of light weight and good
performance under contaminated conditions.
This research illustrates the electric potential and field computation on HVDC
composite insulators by using the charge simulation method. The electric field is
calculated under both dry and wet conditions. Under dry conditions, the field
distributions along the insulators whose voltage levels range from 500 kV to 1200 kV are
calculated and compared. The results indicate that the HVDC insulator produces higher
electric field, when compared to AC insulator. Under wet conditions, a 500 kV insulator
is modeled with discrete water droplets on the surface. In this case, the field distribution
is affected by surface resistivity and separations between droplets. The corona effects on
insulators are analyzed for both dry and wet conditions. Corona discharge is created,
when electric field strength exceeds the threshold value. Corona and grading rings are
placed near the end-fittings of the insulators to reduce occurrence of corona. The
dimensions of these rings, specifically their radius, tube thickness and projection from
end fittings are optimized. This will help the utilities design proper corona and grading
rings to reduce the corona phenomena.