Abstract: Porcelain specimens were fired at 6C/min to 1250C (dwell time 0.5-3h) and cooled at 6C/min to room temperature. Additionally, three different slower firing/cooling cycles were tried. Sintering profile and effects on MOR, crystalline phase content and morphology were investigated using dilatometry, 4-point bending strength, XRD and FEG-SEM respectively. Industrial-sized specimens prepared using the promising cycle were tested basing on the ANSI standards. Increasing dwell time from 1h to 3h at peak temperature of 1250C resulted in neither a significant effect on the quartz and mullite content nor MOR. Reducing the firing/cooling rate to below 6C/min, for peak temperature of 1250C (dwell time of 1h) does not result in improvement of strength of porcelain. The industrial sized specimen exhibited flashover voltages of 20.3kV (dry) and 9.3kV (wet) respectively, transverse strength of 12.5kN and bulk density of 2.27g/cm3, which are satisfactory. There was however dye penetration during porosity test. KeywordsDwell time, Microstructure, Porcelain, Strength.
Abstract: This paper investigates the influence of various
parameters on the behaviour of water droplets on polymeric surfaces
under high electric fields. An inclined plane test was carried out to
understand the droplet behaviour in strong electric field. Parameters
such as water droplet conductivity, droplet volume, polymeric
surface roughness and droplet positioning with respect to the
electrodes were studied. The flashover voltage is affected by all
aforementioned parameters. The droplet positioning is in some cases
more vital than the droplet volume. Surface damages were analysed
using Scanning Electron Microscopy (SEM) studies and by Energy
dispersive X-ray Analysis (EDAX). It is observes that magnitude of
discharge have direct influence on amount of surface da
Abstract: This study describes analysis of tower grounding
resistance effected the back flashover voltage across insulator string
in a transmission system. This paper studies the 500 kV transmission
lines from Mae Moh, Lampang to Nong Chok, Bangkok, Thailand,
which is double circuit in the same steel tower with two overhead
ground wires. The factor of this study includes magnitude of
lightning stroke, and front time of lightning stroke. Steel tower uses
multistory tower model. The assumption of studies based on the
return stroke current ranged 1-200 kA, front time of lightning stroke
between 1 μs to 3 μs. The simulations study the effect of varying
tower grounding resistance that affect the lightning current.
Simulation results are analyzed lightning over voltage that causes
back flashover at insulator strings. This study helps to know causes
of problems of back flashover the transmission line system, and also
be as a guideline solving the problem for 500 kV transmission line
systems, as well.
Abstract: Modern Society is strongly dependent on a reliable
power supply. The availability of cheap and reliable supply of
electrical energy is an indicator of societal welfare. Uninterrupted
reliable operation of a modern power system depends to a great
extent on reliable and satisfactory performance of insulators under
different environmental conditions. This paper reports result of
natural pollution tests that have been done at sites around city of
Aligarh (India). Flashover voltage per insulation distance (FOVUID)
of porcelain disc insulator for different pH values, ESDD has been
recorded for proper correlation between electrical and chemical
parameters. The pH of the contaminants has been suggested to be an
effective pollution severity indicator and may be used as a diagnostic
parameter for proper maintenance of porcelain insulators.