ELECTRIC FIELD AND CURRENT DENSITY CHARACTERISTIC OF CONTAMINATED SOLID INSULATOR

The performance of an insulator may degrade over a time period. One of the main factor is due to presence of contamination on the insulator which leads to flashover, corona and damages the insulator. This study focuses on overhead XLPE cables used in distribution system with voltage rated 33kV. The contaminants are varied in order to study the behaviour of electric field and current density of the XLPE insulator. Contaminant used in this study is sodium chloride, lead and rain water. Quickfield software was used to draw and simulate the contaminated cable. The electrical conductivity of cable and contamination was used to represent every layer of the drawing. From the result produce, analysis on the electric field and current density of a contaminated and non-contaminated insulator was made. Analysis shows that the contaminated insulator has higher electrical field and current density compared to non-contaminated insulator. When the electrical conductivity is high, the electric field is the lowest and the current density is the highest in the insulator. Whereas, the XLPE insulator with sodium chloride contamination has the highest current density followed by rain water and lead because the conductivity of sodium chloride is the highest. The electric field strength of lead is the highest followed by rain water and sodium chloride

Space charges analysis on insulator with uniform layer contamination effect

High voltage direct current (HVDC) transmission provides an attractive alternative for bulk power transfer. However, HVDC transmission may have loss about half per unit length of high voltage alternating current (HVAC) at the same amount of power carried. This is due to the space charge formation around the conductor in HVDC cables. It is known that the presence of space charge inside an insulator may distort the local electric field and surface energy. This paper investigates the effect of electrostatics for space charge, electric field and surface energy in the HVDC cable in clean and contaminated conditions. The effect of uniform layer contamination from oil, sandstone and fresh water was conducted on 11 kV XLPE cable using finite element software under electrostatics study. The contamination layer was created around the XLPE cable by multifarious the radius of layer contamination from the conductor. The simulation results show that enlargement of contamination layer radius by 1.0 mm (light), 1.5 mm (medium) and 2.0 mm (heavy) resulted in the reduction of surface energy by 20% and electric field by 22% but increase the space charge amplitude by 76%. The study also found that fresh water can be considered as the worst contamination compared to oil and sandstone

Collapsibility behaviour of ABS P400 and PMMA used as sacrificial pattern in direct investment casting process

The feasibility of the Investment Casting (IC) process has been choose to be vital route in producing the metal alloy products. However, less report regarding the feasibility of portable Additive Manufacturing (AM) machines to be employed in casting process. Sacrificial wax pattern in casting process has been substitute with the AM material due to its brittleness and higher cost for hard tooling. Due to this constrain, the quality of fabricated AM materials, collapsibility analysis and strain induce was investigated. The patterns were made using ABS P400 and PMMA materials by two different types of technique which are Fused Filament Fabrication (FFF) and Polyjet technique. There were three different types of internal structures which are hollow, square and hexagon patterns. The thermal properties of the materials were studied by thermogravimetry analyzer (TGA) and linear thermal expansion. The collapsibility screening was determined to investigate the behavior of the patterns underneath the expansion. Apparently, patterns made by Polyjet technique shows better accuracy compare to FFF technique. It shows that, the PMMA error lies between -2.2 % until -0.63 % compared to ABS which is -2.4 % until 1.2% for hollow, square and hexagon patterns respectively. The data of the surface roughness were varies whereas internal structures does not play significant role in improving the surface roughness. From the strain analysis, it can be suggested that hexagon internal structure yield less stress compare to square patterns. In terms of collapsibility, hollow and hexagon patterns yield most successful warping whereas it indicates the patterns able to collapse underneath the expansion. Moreover, PMMA material tends to gain higher strain compared to ABS material whereas this can be illustrated by the graph of linear expansion. Nevertheless, to overcome the cracking of ceramic shell due to higher thermal expansion, different build layer thickness was adopted to overcome the issue

Electric Field Characteristics of HDPE-NR Biocomposite Under Breakdown Condition

It is critical to develop new insulating materials that can improve the performance of next generation high voltage cables for creating future electrical networks. The high electric field reduces the resistance of solid insulation and produces partial discharge through imperfections in a dielectric, causing the dielectric to age and eventually fail. Thus, this project seeks to analyse the electric field intensity of High Density Polyethylene (HDPE) in breakdown condition when added with 10g, 20g and 30g of different types of bio-filler such as coconut coir fibre, pineapple leaves fibre, and oil palm empty fruit bunch. This can be achieved by creating a two-dimensional (2D) axisymmetric electrostatic model by using the Finite Element Method Magnetics (FEMM) 4.2 software. The results showed that the unfilled HDPE biocomposites have a higher electric field intensity than 10g, 20g, and 30g biocomposite. This indicates that the maximum electric field intensity changes according to the permittivity and voltage of the bio-filler under breakdown conditions. As a result, the maximum electric field intensity was much lower for HDPE added with a 20g of the pineapple leaves fibre. Hence, pineapple leaves fibre was the best composition as it tends to improve the dielectric properties since it has a lower electric field intensity at the top electrode as compared to other compositions

Electric Field Characteristics of HDPE-NR Biocomposite Under Breakdown Condition

It is critical to develop new insulating materials that can improve the performance of next generation high voltage cables for creating future electrical networks. The high electric field reduces the resistance of solid insulation and produces partial discharge through imperfections in a dielectric, causing the dielectric to age and eventually fail. Thus, this project seeks to analyse the electric field intensity of High Density Polyethylene (HDPE) in breakdown condition when added with 10g, 20g and 30g of different types of bio-filler such as coconut coir fibre, pineapple leaves fibre, and oil palm empty fruit bunch. This can be achieved by creating a two-dimensional (2D) axisymmetric electrostatic model by using the Finite Element Method Magnetics (FEMM) 4.2 software. The results showed that the unfilled HDPE biocomposites have a higher electric field intensity than 10g, 20g, and 30g biocomposite. This indicates that the maximum electric field intensity changes according to the permittivity and voltage of the bio-filler under breakdown conditions. As a result, the maximum electric field intensity was much lower for HDPE added with a 20g of the pineapple leaves fibre. Hence, pineapple leaves fibre was the best composition as it tends to improve the dielectric properties since it has a lower electric field intensity at the top electrode as compared to other compositions