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The inviscid compressible flows represent the flow model of high-speed flow with the viscous effects can be ignored. Such flow phenomena appear when a high Reynolds number flow past trough a streamlined body at relative a low angle attack. The most commercial passenger airplane is operated at such flow condition, as results the aircraft industries have already put their efforts to develop the capability for solving the governing equation of inviscid compressible flow. The governing equation of inviscid compressible flow which is called as the Euler Equation can solved numerically. There are various numerical schemes had been developed and the most of them are dedicated for capturing the presence of shock wave phenomena which is normally appearing at high speed flow. The present work presents a comparative study over various numerical schemes which they are already been developed for solving the Euler equations. Those numerical schemes are the MacCormack Scheme, the Fourth Order Runge Kutta Scheme, The First and Second Order Flux Splitting Steger Warming Scheme, Flux Splitting Bram Van Leer Scheme, the Harten Yee TVD scheme, Roe Sweby TVD scheme, Davies – Yee TVD scheme and the Modified Four Order Runge Kutta and Harten Yee TVD scheme. These nine numerical schemes are applied to the case of flow past through nozzle. The flow phenomena may appear along the nozzle may be the form completely as an isentropic flow or the flow with shock wave. These two flow phenomena are depended the boundary condition of the flow problem under considered. The implementation to case of isentropic flow along the nozzle, those nine numerical schemes works well, and the number of iterations required nearly the same between one with the other except for the Fourth Order Runge Kutta Scheme. In the case of flow with shock wave, the Fourth Order Runge Kutta Scheme, Second Order Steger Warming and the Bram Van Leer Scheme are failing. The presence of shock wave, each numerical scheme requires more iteration number to achieve a convergent solution. The Modified Runge Kutta - Harten Yee scheme may represent an appropriate a numerical scheme for solving the flow problem with the presence of shock wave.

In developing future electrical networks, it is crucial to develop new alternatives insulating materials which can improve the performance of the next generation high voltage cables. The high electric field reduces the resistance of solid insulation and causes partial discharge occurs through the impurities in a dielectric where this phenomenon causes ageing to the dielectric and ultimately leads to breakdown. Thus, this paper seeks to analyse the electric field intensity of High Density Polyethylene (HDPE) when added with 10%, 20% and 30% 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 inclusion of bio-filler in HDPE increased the maximum electric field intensity when compared with unfilled HDPE. The electric field intensity also varied with the different percentages loading of biocomposite and their permittivity. As a result, the maximum electric field intensity was much lower for HDPE added with a 10% loading of the oil palm empty fruit bunch. Hence, oil palm empty fruit bunch was the best composition as it tends to improve the dielectric properties since it has a lower electric field intensity at the top sphere electrode as compared to other compositions.

The influence of solid insulation has been investigated by few researchers.The mechanism of solid breakdown is important in insulation studies. In thisresearch, testing on Linear-Low Density Polythylene (LLDPE) with NaturalRubber (NR) and different weight concentration of biofiller are conductedunder High Voltage Direct Voltage (HVDC) by using needle and spheretypes of electrode arrangements. Oil Palm Empty Fruit Bunch (OPEFB) andPineapple Leaf Fiber (PALF) are the biofillers used for the samplesdevelopment. The LLDPE-NR samples consists of different weightpercentages of biofiller which are 0%, 2.5%. 5.0%. 7.5% and 10% with 3mmthickness. The voltage has been increased until the breakdown occurs. Basedon the results obtained, OPEFB and PALF with the highest weightpercentages of 10% showed the highest damage voltages of 59.09kV and59.36kV. It has been proven that both samples with the highest filler contenthave appropriate insulating properties. In conclusion, the addition of biofiberto LLDPE-NR has improved the breakdown properties compared to pureLLDPE.

Pulsed electro-acoustic (PEA) is well known as a non-destructive technique for testing and describing space charge profiles in the insulation. Degradation due to moisture, ageing, external flashover, partial discharge and space charge are considered as insulation defects that is an issue in high voltage insulator. Space charge may distort the internal electric field that may lead to an electrical breakdown. For instance, a method based on an acoustic phenomenon can be used to describe the space charge profiles. This paper compares several earlier researches on different specimen of PEA method and reviews their results to find the space charge distribution profiles. The scope of the review includes types of methods used. The acoustic technique is considered for this study. It has been observed that the PEA technique successfully gives the same result as theoretical that is based on the obtained profile. Linear low-density polyethylene (LLDPE) composite demonstrates about 89 % lower charge density value compared to cross-linked polyethylene (XLPE) and polypropylene (PP) composite. While the electric field value of ethylene-vinyl acetate (EVA) sample is 75 % lower than low-density polyethylene (LDPE) sample. This study found that the time interval, specimen thickness and the electric field sway the space charge profiles.

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.

Polymeric nanocomposites are widely used for high voltage outdoor insulating application due to their good electrical performance. Recently, SiO2, TiO2 and MMT nanofillers are being used as filler because there are listed as main nanofiller commonly used in electrical engineering. Natural rubber (NR) was used because the nature of the interphase is found to affect viscoelasticity and it develops several interphases with the Linear Low-Density Polyethylene (LLDPE) matrix. One of the problems associated with outdoor polymeric insulators is tracking of the surface which can directly influence the reliability of the insulator. This paper presents the outcome of an experimental study to determine the conductivity level of the LLDPE-NR compound, filled with different amount of SiO2, TiO2 and MMT nanofiller using Polarization and Depolarization Current (PDC) measurement technique. LLDPE and NR with the ratio composition of 80:20 were selected as a base polymer. Results show that different compositions as well as the surface physical conditions affect the PDC measurement results.

Almost all research on natural fibre reinforced composite has focused on the mechanical properties of the composite. Drawing on the important factors that effect the end product of composite, this paper reviews electrical properties of hybrid biocomposite when fibre content and surface treatment is varied. The compilation of dielectric constant, dissipation factor, loss factor and moisture absorption reported by researchers has been presented in this paper. The intrinsic characteristic of natural fibre which is hydrophilic is the main drawback that affects the electrical properties of the composite. Alkaline treatment on natural fibre has proven to overcome the hydrophilic characteristic and improves the adhesion between matrix and fibre. Besides that, the percentage of fibre content plays an important role in producing a good natural fibre reinforced hybrid composite. The moisture uptake, dielectric constant, dissipation factor and loss factor of the composite decreases with decreased fibre content.

The Polarization and Depolarization Current (PDC) measurement is an efficient and effective diagnostic technique based on time domain measurement, for evaluating the high voltage insulation condition. This paper presents a review and comparison results from several published papers on the application of the PDC method to finding the conductivity and moisture content of various types of insulators. For solid insulation, the study was focused on cable insulation, electric machine stator insulation, and paper insulator in transformer insulation with different conditions. For liquid insulation, the review and comparison was done on biodegradable and mineral transformer oils, with fresh oil condition, and aged condition. The results from previous researchers tests were complied, analyzed and discussed, to evaluate the application of the PDC method to monitor the conductivity and moisture of HV equipment insulation systems. From the review results, the PDC technique successfully gives an indication of the conductivity and moisture level of high voltage insulation.

Polymer nanocomposites for HV insulation have been extensively being studied in recent years because of its unique properties and ability to enhance electrical performance. Electrical conduction of polymer nanocomposites have been used as one of the tool to monitor its dielectric behaviour. This paper present the experiment result for polarization and depolarization current and conductivity value to find the patterns and trends of DC conductivity. Then this experiment result will be compared with results from previous researches studies on current and conductivity analysis with different method and samples. The analysis result shown that DC conductivity exhibits significant reduction with addition of any types of nanofiller at right amount. However right percentage of nanofiller added is not same for different type of materials. This was due to decreasing of initiation probability of short circuit treeing in the insulation. The conductivity analysis shows that addition of nanofiller into the polymer improved its insulation properties.

The paper investigates the effects of various gas turbine operating and health conditions on its hot section component’s creep life via a simple relative creep life parameter known as Creep Factor. Using the Creep Factor, the correlation between individual gas turbine operating and health parameter and component’s creep life was established and the weight of the impact was measured. Analytical-parametric-based creep life estimation model combined with the Creep Factor approach was developed and integrated with an existing engine performance model to allow the estimation of various hot section component creep lives and the computation of the Creep Factors. The impact analysis was carried out on the high pressure turbine blade of a model turbo-shaft helicopter engine. The results indicate that for a clean engine, the change in engine rotational speed was seen to provide the highest impact on changing the blade’s creep life consumption while for a degraded engine, the presence of compressor fouling has the highest threat in changing the blade’s creep life. The analysis also shows that the Creep Factor is a good indicator of creep life consumption and provides a good technique to rank the influencing factor according to the threat they imposed.

During helicopter forward flight, the retreating blade revolves at high angle of attack compared to advancing blade in order to balance the lift and also to stabilise the helicopter. However, due to the aerodynamics limitations of the retreating blade at forward flight, stall may occur at high angle of attack compared with the advancing blade. This phenomenon is dangerous for pilot when controlling and balancing the helicopter while flying against strong wind. This paper investigates the capabilities of introducing multiple vortex traps on the upper surface of the helicopter airfoil in order to delay the stall angle of retreating helicopter blade. Blade Element Theory (BET) was applied to scrutinize the lift force along the helicopter blade. Computational Fluid Dynamic (CFD) analyses using the Shear-Stress Transport (SST) turbulence model was carried out to investigate the effect of groove on delaying the stall and to predict the separation of flow over the airfoil. Based on the CFD analyses, the optimization of the groove was done by analyzing the numbers and locations of the grooves. Finally, the results from both BET and the CFD analyses were utilised to obtain the lift force achieved by the vortex trap. The study showed that the presence of multiple vortex traps has successfully increased the lift coefficient and most importantly, delaying the stall angle.

The stepper motor movement process produced different frequency and pulses. This research explained about the frequency and pulses for the stepper motor movement by using Programmable Logic Controller (PLC) as research method. The study was done to find the suitable frequency and pulses for stepper motor movement by developing a prototype stepper motor controller system. The pulse frequency used did not affected the distance of moving load in the stepper motor operations. The increasing number of pulse frequency only will affect the time taken for the stepper motor to complete its operations. The result showed that number of pulse frequency at high operation was 5000 Hz. Pulse number reacted as a manipulated variable that affected both factor which is time taken of stepper motor operation and the distance of moving load.

Nowadays, XLPE cable has been widely used because it has better resistance than other cables. XLPE insulation has unique features including a high dielectric strength and high insulation resistance. A lot of researches based on hardware and software have been conducted to prove the effectiveness of XLPE cable such as AC and DC applications and Space Charge Distribution measurement under HVDC at High Temperature. This research focused on analysis of space charge and electric field on XLPE cable with effect of non-uniform contamination layer by using Quickfield Software. Non-uniform contaminations have been applied along XLPE cable using Arsenic Tribromide (AsBr3), Boron Bromide (BBr3), Ethylene Dichloride (CH2C1), Formic Acid (CH1O2), Formamide (CH3NO) and Alcohol element. Presence of these contamination elements represent of underground contamination. The size and layer of the contamination were non-uniform type. From the results, it is shown that lower dielectric constant of contamination will affect more on charge of XLPE insulation. As a conclusion, it can be seen lower dielectric constant value of contamination element greatly affecting the performance of XLPE insulation. Furthermore, size of contamination also influences the content of charge in contamination where the bigger the contamination size, the more charge contained in the contamination.

Oils acts as insulation and cooling agent in the transformer. Petroleum-based oils are widely used in transformers due to their qualified properties as good insulation materials. Unfortunately, the used of petroleum-based oils has adverse effects on environment in the event of any failure to transformers such as tank leakage or explosions. Therefore, researchers have been studied and have found environmentally friendly oil that is suitable as substitutes in transformer. Thus, breakdown voltage tests using direct current and alternating current with the addition of different water content were performed to identify the potential of palm oil and coconut oil in the transformer isolation system. Refined, Bleached and Deodorized oil (RBDPO) and coconut oil samples were selected to be test in this study. The oil samples were test by varies the gap distance of test cell electrode and the level of water content. As a conclusion, RBDPO oil has greater breakdown voltage test under DC breakdown voltage test in term of increment of the gap distance.

The most important aspect influencing the circumstance and characteristics of electrical discharges is the distribution of electric field in the gap of electrodes. The study of discharge performance requires details on the variation of maximum electric field around the electrode. In electrical power system, the insulation of high voltage power system usually subjected with high electric field. The high electric field causes the degradation performance of insulation and electrical breakdown start to occur. Generally, the standard sphere gaps widely used for protective device in electrical power equipment. This project is study about the electric field distribution and current density for different electrode configuration with XLPE barrier. Hence, the different electrode configuration influences the electric field distribution. This project mainly involves the simulation in order to evaluate the maximum electric field for different electrode configuration. Finite Element Method (FEM) software has been used in this project to perform the simulation. This project also discusses the breakdown characteristics of the XLPE. The accurate evaluation of electric field distribution and maximum electric field is an essential for the determination of discharge behavior of high voltage apparatus and components. The degree of uniformity is very low for pointed rod-plane when compared to other two electrode configurations. The non- uniform electric distribution creates electrical stress within the surface of dielectric barrier. As a conclusion, when the gap distance between the electrodes increase the electric field decrease.

The properties of insulation have been improved by many research and the ability of nanocomposite material that composes the characteristic of improving electrical performance due to the addition of nanofiller into the based material gets serious attention. Polarization and Depolarization Current (PDC) measurement that has the ability to assess the condition of HV insulations with the initial periods after a DC step voltage application was favoured compared to other non-destructive monitoring techniques. This paper presents the works on moisture absorption in LLDPE-NR nanocomposite with different amount and percentage of nanofillers. The study of PDC level of the LLDPE-NR compound, filled with different amount of SiO2, TiO2 and MMT nanofiller using Polarization and Depolarization Current (PDC) measurement technique is the main objective of this research. These results show that sample A1 has the lowest polarization current value and sample B5 has the lowest depolarization current value.

Polymeric nanocomposites in which the nanosize fillers are evenly distributed in the polymer material attract attention as an insulating material due to their ability to enhance the materials performance properties of electrical and mechanical. For high voltage (HV) insulation application, one of the targets is to obtain new insulators with improved dielectric properties. This paper presents the outcome of an experimental study to determine the conductivity level of the linear low-density polyethylene- (LLDPE-)natural rubber (NR) compound, filled with different amount of SiO2and TiO2nanofiller by using the polarization and depolarization current (PDC) measurement technique. linear low-density polyethylene (LLDPE) and natural rubber (NR) with the ratio composition of 80 : 20 are selected as a base polymer. The experiment was conducted to find PDC pattern and conductivity variations of each of the LLDPE-NR/SiO2and LLDPE-NR/TiO2samples. The results show that the addition of SiO2filler exhibited less conductivity compared to TiO2filler with certain percentage. From the study, it can be concluded that LLDPE-NR/SiO2is a better insulator compared with LLDPE-NR/TiO2.

The study of electrical insulating materials can never be overemphasized. When these materials are subjected to either electrical or thermal stresses each one respond in a uniquely different way from one another. The response of insulating materials to its stressors is a stochastic process with varying dependent variables. The discovery of newer or composite insulating materials, having better electrical properties, have further deepened this lack of understanding. Researchers and engineers have utilized the dielectric relaxation in the materials as an assessment tool. Polarization and Depolarization Current (PDC) is one of such assessment tools to measure the relaxation current when a sudden stress is applied or removed. This paper presents study of the relaxation current in Kraft paper and how moisture diffusion in it affects the conductivity of the Kraft paper. This assessment technique was done using a multi physics software; COMSOL Multiphysics. COMSOL Multiphysics has been chosen because dielectric relaxation has a multidisciplinary science of physic, chemistry and electrical engineering involved in the process. 100V dc was applied across cellulose molecule and the resulting conductivity, σ and moisture diffusion was measured and presented. The result shows the interesting relationship between conductivity & changes in moisture in the solid insulation.

Electrical tracking is a process of formation of permanent conducting path across the insulating material due to the surface erosion under high voltage application. The existing of leakage current (LC) on the wet contaminated material surface causes the generation of surface discharges that resulted to the material degradation. Electrical tracking test can be indicated as failure when LC exceed 60 mA for more than two seconds or at least 25mm of formation of carbon track or erosion breaks through the thickness of the sample. In this paper, a new formulated thermoplastic elastomer material which composed of Linear Low-Density Polyethylene with Natural Rubber (LLDPE/NR) filled and unfilled with different percentage of silicone oxide (SiO2) or titanium oxide (TiO2) as nanofiller is presented. The compound was tested based on IEC 60587 inclined plane tracking test procedure. The analysis of LC and rate of carbon track development were also conducted. Surface morphology analysis was carried out for investigating the degraded surface structure of the materials. The formulation of pure LLDPE/NR has shown the highest average leakage current whereas the composition of LLDPE/NR-TiO2 with 1 % wt of nanofiller was found to be the best electrical tracking resistance due to the lowest average leakage current and no carbon track appeared. The blends of LLDPE/NR-SiO2 show that low average leakage current and no carbon track in less than 5 % wt nanofiller. The usage of 5% wt or more for both nanofiller had shown the worst in carbon track formation.

Polymer nanocomposites materials have recently emerged as a dielectric and for electrical insulation. Polyethylene has long been used as extruded cable and HV insulation. Currently, this material has received significant attention because of its ability to enhance electrical insulation properties by addition of nano-filler. Polarization and Depolarization Current (PDC) measurement is an efficient and effective diagnostic technique based on time domain measurement for evaluating and condition monitoring of polymer nanocomopsite for HV insulation. Electrical conduction for polymer nanocomposites has been used widely as a tool to monitor the dielectric behaviour. This paper focuses on application of Polarization and Depolarization Current (PDC) testing method to evaluate and determine the performance of LLDPE nanocomposite for high voltage insulating material. The experiment was conducted to find PDC pattern of the material when added with nano-filler (silicon oxide) as well as to find its conductivity values at different percentage of nano- filler. PDC values and DC conductivity exhibits significant reduction with addition of nano-filler at different %wt of concentration. This was due to the decrease of initiation probability of short circuit treeing in the insulation. The PDC result shows that addition with certain percentage of nano-filler into the LLDPE based material could improve HV insulation properties of the material.