Abstract: The choice evaluation between oil-immersed and dry-type transformers is often controlled by cost, location, and application. This paper compares the electrical performance of liquid- filled and dry-type transformers, which will assist the customer to choose the right and efficient ones for particular applications. An accurate assessment of the time-average flux density, electric field intensity and voltage distribution in an oil-insulated and a dry-type transformer have been computed and investigated. The detailed transformer modeling and analysis has been carried out to determine electrical parameter distributions. The models of oil-immersed and dry-type transformers are developed and solved by using the finite element method (FEM) to compare the electrical parameters. The effects of non-uniform and non-coherent voltage gradient, flux density and electric field distribution on the power losses and insulation properties of transformers are studied in detail. The results show that, for the same voltage and kilo-volt-ampere (kVA) rating, oil-immersed transformers have better insulation properties and less hysteresis losses than the dry-type.
Abstract: In this study, electric field distribution analyses for
three pylon models are carried out by a Finite Element Method
(FEM) based software. Analyses are performed in both stationary and
time domains to observe instantaneous values along with the
effective ones. Considering the results of the study, different line
geometries is considerably affecting the magnitude and distribution
of electric field although the line voltages are the same. Furthermore,
it is observed that maximum values of instantaneous electric field
obtained in time domain analysis are quite higher than the effective
ones in stationary mode. In consequence, electric field distribution
analyses should be individually made for each different line model
and the limit exposure values or distances to residential buildings
should be defined according to the results obtained.
Abstract: This paper presents the effect of electric field
distribution which is an electric field intensity analysis. Consideration
of the dielectric heating of grains and insects, the rice and rice
weevils are utilized for dielectric heating analysis. Furthermore, this
analysis compares the effect of electric field distribution in rice and
rice weevil. In this simulation, two copper plates are used to generate
the electric field for dielectric heating system and put the rice
materials between the copper plates. The simulation is classified in
two cases, which are case I one rice weevil is placed in the rice and
case II two rice weevils are placed at different position in the rice.
Moreover, the probes are located in various different positions on
plate. The power feeding on this plate is optimized by using CST EM
studio program of 1000 watt electrical power at 39 MHz resonance
frequency. The results of two cases are indicated that the most
electric field distribution and intensity are occurred on the rice and
rice weevils at the near point of the probes. Moreover, the heat is
directed to the rice weevils more than the rice. When the temperature
of rice and rice weevils are calculated and compared, the rice weevils
has the temperature more than rice is about 41.62 Celsius degrees.
These results can be applied for the dielectric heating applications to
eliminate insect.
Abstract: Charging and discharging phenomenon on the surface
of materials can be found in plasma display panel, spacecraft
charging, high voltage insulator, etc. This report gives a simple
explanation on this phenomenon. A scanning electron microscope
was used not only as a tool to produce energetic electron beam to
charge an insulator without metallic coating and to produce a surface
discharging (surface breakdown/flashover) but also to observe the
visible charging and discharging on the sample surface. A model of
electric field distribution on the surface was developed in order to
explain charging and discharging phenomena. Since charging and
discharging process involves incubation time, therefore this process
can be used to evaluate the insulation property of materials under
electron bombardment.
Abstract: This paper presents the simulation the results of
electric field and potential distributions along surface of silicone
rubber polymer insulators. Near the same leakage distance subjected
to 15 kV in 50 cycle salt fog ageing test, alternate sheds silicone
rubber polymer insulator showed better contamination performance
than straight sheds silicone rubber polymer insulator. Severe surface
ageing was observed on the straight sheds insulator. The objective of
this work is to elucidate that electric field distribution along straight
sheds insulator higher than alternate shed insulator in salt fog ageing
test. Finite element method (FEM) is adopted for this work. The
simulation results confirmed the experimental data, as well.
Abstract: This paper presents the simulation results of electric field and potential distributions along surface of silicone rubber polymer insulators under clean and various contamination conditions with/without water droplets. Straight sheds insulator having leakage distance 290 mm was used in this study. Two type of contaminants, playwood dust and cement dust, have been studied the effect of contamination on the insulator surface. The objective of this work is to comparison the effect of contamination on potential and electric field distributions along the insulator surface when water droplets exist on the insulator surface. Finite element method (FEM) is adopted for this work. The simulation results show that contaminations have no effect on potential distribution along the insulator surface while electric field distributions are obviously depended on contamination conditions.
Abstract: In this paper, the computation of the electrical field distribution around AC high-voltage lines is demonstrated. The advantages and disadvantages of two different methods are described to evaluate the electrical field quantity. The first method is a seminumerical method using the laws of electrostatic techniques to simulate the two-dimensional electric field under the high-voltage overhead line. The second method which will be discussed is the finite element method (FEM) using specific boundary conditions to compute the two- dimensional electric field distributions in an efficient way.
Abstract: A power cable is widely used for power supply in
power distributing networks and power transmission lines. Due to
limitations in the production, delivery and setting up power cables,
they are produced and delivered in several separate lengths. Cable
itself, consists of two cable terminations and arbitrary number of
cable joints, depending on the cable route length. Electrical stress
control is needed to prevent a dielectric breakdown at the end of the
insulation shield in both the air and cable insulation. Reliability of
cable joint depends on its materials, design, installation and operating
environment. The paper describes design and performance results for
new modeled cable joints. Design concepts, based on numerical
calculations, must be correct. An Equivalent Electrodes
Method/Boundary Elements Method-hybrid approach that allows
electromagnetic field calculations in multilayer dielectric media,
including inhomogeneous regions, is presented.