The grounding system of a lightning protection scheme is designed basically to avoid arcing and
dangerous step potentials. The grounding impedance of the system varies depending on soil structure and frequency. This paper describes the effect of harmonic impedance (also called frequency dependence of soil) on potential distribution under lightning strike to a metal tower with single grounding path, for different soil types. The results show that the peak value of ground potential rise (GPR) and step voltage (SP) may reach extremely hazardous values even at distances in the order of 90 m from the tower footing, especially when soil resistivity is high. Hence, we emphasise that, in contrast to power grounding, when designing of grounding systems that are meant to handle transient or high frequency currents as well, the frequency dependent soil parameters should be considered to avoid hazardous situations, especially at locations with a high probability of lightning strikes such as metal towers.
Space Vector Pulse Width Modulation (SVPWM) method is widely used as a modulation technique
to drive a three-phase inverter. It is an advanced computational intensive method used in pulse width modulation (PWM) algorithm for the three-phase voltage source inverter. Compared with the other PWM techniques, SVPWM is easier to implement, thus, it is the most preferred technique among others. Mathematical model for SVPWM was developed using MATLAB/ Simulink software. In this paper, the interface between MATLAB Simulink with the three-phase inverter by using Arduino Uno microcontroller is proposed. Arduino Uno generates the SVPWM signals for Permanent Magnet Synchronous Motor (PMSM) and is described in this paper. This work consists of software and hardware implementations. Simulation was done via Matlab/Simulink software to verify the effectiveness of the system and to measure the percentage of Total Harmonic Distortion (THD). The results show that SVPWM technique is able to drive the three-phase inverter with the Arduino UNO.
Shunt active power filter (SAPF) is the most effective solution for current harmonics. In its controller, DC-link capacitor voltage regulation algorithm with either proportional-integral (PI) or fuzzy logic control (FLC) technique has played a significant role in maintaining a constant DC voltage across all the DC-link capacitors. However, PI technique performs poorly with high overshoot and significant time delay under dynamic state conditions, as its parameters are difficult to be tuned without requiring complete knowledge of the designated system. Although FLC technique has been developed to overcome limitations of PI technique, it is mostly developed with high complexity thereby increases computational burden of the designed controller. This paper presents a fuzzy-based DC-link capacitor voltage regulation algorithm with reduced computational efforts to enhance performance of three-phase three-level neutralpoint diode clamped (NPC) inverter-based SAPF in overall DC-link voltage regulation. The proposed method is called effort-reduction FLC technique. The proposed algorithm is developed and evaluated in MATLAB-Simulink. Moreover, conventional algorithm with PI technique is tested for comparison purposes. Simulation results have confirmed improvement achieved by the proposed algorithm in comparison to the conventional algorithm.
Soil plays an important role in ground designing. Engineers normally consider only soil resistivity under normal or steady state condition when designing the grounding system. Under certain circumstances such as lightning, electrical response of the soil will change accordingly and thus, the performance of the grounding system will be affected. The purpose of this study is to investigate the effect of moisture content on the electrical behaviour of sand and clay under high impulse voltage condition. Both soil samples are dried in the oven at 110 ± 5°C to remove the water content until became 0%. The samples are subjected to 30 shots of standard (1.2/50μs) lightning impulse voltage for both positive and negative impulse polarities. This is followed by moistening the samples with 5% amount of water over the volume of the samples. The corresponding V50% for both sand and clay was calculated and the value obtained was converted to standard atmospheric condition. The voltage at breakdown and time to breakdown for each soil sample was analysed a statistical analysis conducted for these two parameters to determine if type of soil and moisture content have an effect on the breakdown voltage. In general, it was found that clay is more efficient in neutralising high impulse voltage than sand likely due to the former’s low resistivity and porosity.
Top-Oil Temperature (TOT) is one of the basic components to estimate the Hot-Spot temperature (HST) of the transformers. This paper presents an alternative TOT model based on the heat transfer theory that utilises Nonlinear Thermal Resistance (NTR) and Lumped Capacitance (LC) approaches. It is applied in a thermal-electrical analogy and the heat transfer equivalent equation is determined. This model is tested on a measured TOT of 250 MVA ONAF and 400 MVA ONAF transformers obtained from IEC 60076-7 and previous research. A comparison of TOT is carried out with the existing models IEC 60076-7 exponential and IEEE Loading Guide clause 7 methods. It is found that the thermal model based on the NTR and LC approach could determine the measured TOT closer than the existing methods available in the standards.
MeSH terms: Biochemical Phenomena; Electricity; Hot Temperature; Research; Temperature; Electric Capacitance
Transformer failures lead to interruption of power supply. Therefore, asset management is important to monitor the efficient functioning of transformers. An important approach in asset management is condition assessment whereby the health status of the transformer is assessed via a health index. There are many methods in determining the final value of a health index. This paper examines how different assessment methods can be used in order to come up with the final health index and output of final health index. The output trend shapes are almost the same for Assessment Model A, B and C except for Assessment Model D. There is no strong correlation between the health index and age of the transformer. Generally, the value of health index of the transformer is reflected by its operation and loading history .This paper hence examines the assessment steps and results that will guide the development of a new approach to determine health index value.
MeSH terms: Health Status; Monitoring, Physiologic; Physiological Phenomena; Electric Power Supplies
Controlled humidity environment is of significance in many scientific researches and experiments. In most laboratory-scale atmospheric chambers, an electrical temperature-based control system is used to adjust humidity. Since these chambers are not affordable in every laboratory, other low cost chambers using nitrogen gas or silica gel are used to adjust humidity. In this paper, a mechanism was developed to control the relative humidity in closed lab-scale chambers. Humidification is done by spraying water through a blower fan while de-humidification is by pumping air through silica gel as well as nitrogen gas injection. A Mamdani type fuzzy controller was designed to control the components and relative humidity. The results show the proposed system and controller can adjust and maintain relative humidity from 41% to 100% with maximum overshoot of 1% and the maximum range of error of steady state of 1.2 %.
A programmable CMOS delay line circuit with microsecond delay range and adjustable duty cycle is proposed. Through circuit simulation, approximately 2μs delay range can be achieved using 10-bit counter operating at a clock frequency of 500MHz. Utilising synchronous counters instead of synchronous latches has significantly reduced the large occupied active silicon area as well as the huge power consumption. The generated coarse time delay has shown excellent linearity and immunity to PVT variations. The proposed CMOS delay line is designed using a standard 0.13μm Silterra CMOS technology. The active layout area is (101 x 142) μm2, and the total power consumption is only 0.1 μW.
This paper presents an auto grasping algorithm of a proposed robotic gripper. The purpose is to enhance the grasping mechanism of the gripper. Earlier studies have introduced various methods to enhance the grasping mechanism, but most of the works have not looked at the weight measurement method. Thus, with this algorithm, the weight of the object is calculated based on modified Wheatstone Bridge Circuit (WBC) which is controlled by programmable interface controller (PIC) method. Having this approach introduces and improves the grasping mechanism through an auto grasping algorithm. Experimental results show that an auto grasping algorithm based on pressure sensor measurements leads to a more precise grasping measurement and consequently enhance the sensitivity measurement as well as accurate movement calibration. Furthermore, several different grasping objects based on the proposed method are examined to demonstrate the performance and robustness of our approach.
One of the concerns in power system preventive control and security assessment is to find the point where the voltage and frequency collapse and when the system forces a severe disturbance. Identifying the weakest bus in a power system is an essential aspect of planning, optimising and post-event analysing procedures. This paper proposes an approach to identify the weakest bus from the frequency security viewpoint. The transient frequency deviation index for the individual buses is used as the weakest bus identification as well as a frequency security indicator. This approach will help to determine the bus with the worst deviation, which helps to analyse the system disturbance, takes proper control action to prevent frequency failure, and most importantly, observes consumer frequency. The approach is applied to the WSCC 9 bus test system to show the feasibility of the method.
MeSH terms: Paper; Motor Vehicles; Physical Phenomena; Mechanical Phenomena
This paper presents a modified design of low power recovery circuit in micro-system implanted device to stimulate the human nerve and muscle. The amplitude shift keying ASK was used to modulate data by using operating frequency 6.78MHz ISM industrial scientific medical band to be less invasive to tissue. The proposed system consists of an external part which has ASK modulator and class-E power amplifier with 94.5% efficiency. The internal part has half wave rectifier and voltage regulator to generate very stable 1.8VDC using 0.35um CMOS technology. The Orcad pspice 16.6 and MULTISIM 11 software were used to simulate the design of power recovery and class-E power amplifier respectively. The regulated voltage utilised to power the sub-electronic device implanted inside human body with very stable voltage even change implanted load resistance. The proposed system has 12.5%modulation index and low power consumption.
MeSH terms: Amplifiers, Electronic; Humans; Industry; Software; Human Body; Prostheses and Implants
Lightning is a natural phenomenon that generates a high electric field during thunderstorm. It has been
reported that lightning strikes amid storms can occur around 100 times per second. The atmospheric
electric field is an imperative parameter during a thunderstorm. Therefore, monitoring the electric field
and its parameters is the best way for local lightning forecast. The electric field monitoring data can
validate the accuracy of weather prediction in a local area from meteorology department or by using
equipment specially designed to measure this electric field that exists when the phenomenon of lightning occurs. In this paper, the relationship between lightning, air humidity and temperature is discussed to understand the post lightning effect on these electric parameters. Additionally, the characteristics of the parameters are observed and analysed.
This paper presents a voltage flicker estimation based on a pair of inter-harmonics analysis method. The proposed algorithm is able to estimate flicker frequency and amplitude changes of a voltage waveform. The correlation of the pair of inter-harmonics, flicker frequency, and amplitude changes are presented and their formulas highlighted. .Experimental results indicate the amplitude of pair of inter-harmonics can detect the voltage flicker. Furthermore, the experimental results are compared with the measurement results obtained by using the Fluke power analyzer (Pst).
Value management explicitly targets to optimize value by providing necessary
functions at the least cost without sacrificing quality and performance. However, the
activities/methods of this technique in emerging economies are here and there
related to informal methodology. Therefore, the occurrence of these activities in an
evolving economy requires investigation. The exploration of the extent to which the
measured variables influenced the latent factors informed the need for this study.
Data was retrieved via self-administered questionnaire from 344 registered and
practicing construction professionals in Nigeria. The data was analyzed using SPSS for
descriptive analysis and Structural Equation Modelling (SEM). Kaiser-Meyer-Olkin
measure of sampling adequacy revealed that the internal consistency of the
developed research instrument was appropriate. Confirmatory factor analysis
indicates satisfactory goodness of fit among acknowledged determinants of the
model. Furthermore, the study revealed three (3) phases of the activities/methods of
value management in the Nigerian construction industry which include: information,
information/function analysis, and creativity/evaluation/development/presentation
phases. This means that value management activities and methods are being
practiced in Nigeria, however not as per the typical methodology or standard. The
need to carry out the practice according to the formal value management
methodology is therefore recommended.
MeSH terms: Creativity; Factor Analysis, Statistical; Humans; Nigeria; Physical Examination; Surveys and Questionnaires; Research; Manipulation, Osteopathic; Construction Industry
The utilization of parallelogram structure in a small-sized humanoid robot consists of two parallel platforms that are linked serially in each leg. The thigh and shank of each leg consists of two servomotors as actuator and linked in parallel platform. By using parallel mechanism in leg structure, foot sole surface is always parallel to the walking surface at any point. Even it looks unnatural to human-like walking motion, the expected result is the robot can maintain it posture while walking and at the point foot sole touch the walking surface, unnecessary vibrates can be modulated at the certain level to remain its balance. The effectiveness and the performance of the proposed parallel platforms are experimented by using zero moment point (ZMP) method by taking various scenario data from pressure sensors attached at the footsole. Planned walking gait is introduced to be identical in terms of foot steps length and width of each leg swing. As the results, in terms of load in each actuator, required torque at servomotors can be reduced because two servomotors are used simultaneously in one parallel system. Stable walking gait can be predicted as the quantity of error falls within the error ranges from the published walking gait patterns.
This paper reports the effect of microbending losses in single mode optical fiber
for pressure sensing system application. Several types of periodical corrugated
plates were fabricated, namely cylindrical-structured surface (Plate A) and
rectangular-structured surface (Plate B) with thicknesses of corrugated parts
were varied at 0.1 cm, 0.2 cm and 0.3 cm. Laser sources with excitation
wavelengths of 1= 1310 nm and 2= 1550 nm were launched at the first end
of the fiber. The values of losses were recorded by using an optical power
meter. It was clearly seen that the microbending losses were polynomially
increased with the increment of applied pressure and the thicknesses of
corrugated parts of Plate A and Plate B. The maximum microbending losses of
1.5185 dBm/kPa was resulted as SMF was coupled with corrugated plates B
with thicknesses of 0.3cm by using excitation wavelength of 1550nm. These
values reduced to 0.7628 dBm/kPa and 0.4014 dBm/kPa as the thicknesses
were decreased to 0.2cm and 0.1cm respectively. In comparison with a plain
plate which acted as a reference indicator, the maximum percentage of
microbending losses was obtained as 74.29 % for Plate A and 95.02 % for Plate
B. In conclusions, we successfully proved the ability of SMF as a pressure sensor
by manipulating the microbending losses experienced by the fiber. The
employment of 1550nm of laser wavelength results better sensitivity sensor
where the system able to detect large losses as the pressure applied on the
corrugated surfaces.
Scholars have opined that the courtyard is a passive architectural design element and
that it can act as a microclimate modifier provided that its design requirements are not
ignored. But despite the assertions, empirical studies on the microclimatic
performance of a fully enclosed courtyard house and the non-courtyard house seems
to be deficient, and the assumption that the Courtyard is a passive architectural design
element needs to be substantiated. Therefore, the purpose of this study is to
investigate the microclimatic performance of a fully enclosed courtyard and noncourtyard
residential buildings. The main objective is to compare their microclimatic
performances in other to draw a conclusion on the best option. Three Hobo Weather
Data Loggers were used to collect climatic data in the buildings, and the third one was
situated in the outdoor area as a benchmark. The climatic variables investigated are;
air temperature and relative humidity. The fully enclosed courtyard residential building
is seen to have a better air temperature difference of 2 oC to 4 oC and the relative
humidity of 2 % to 6 %. In conclusion, the fully enclosed courtyard residential building
has confirmed a more favorable microclimatic performance, and future studies
towards its optimization are recommended.
MeSH terms: Body Temperature; Housing; Humidity; Microclimate; Temperature; Weather; Benchmarking
For the past few years, government-funded universities in Malaysia faced an uphill
battle to strategize their management budget due to significant budget cut by the
Malaysian Government. One portion of the budget will be spent towards achieving the
key performance indicators (KPIs) set by the universities to achieve their annual
targets. Unfortunately, some universities set up their specific strategies to achieve the
KPIs without ample consideration to the limited available resources where less
attention is channeled to the cost of achieving the KPIs. Setting priorities and making
decisions on allocation and reallocation of resources based on the direction of the
strategies must be executed with transparency and accountability and will be of great
importance. In this paper we illustrate how integer programming was applied to
allocate budget based on the KPIs set for one of the government-funded Malaysian
universities’ (U-XYZ’s) research and publication agenda. Two models were developed
and successfully solved. The first model was to determine the total budget needed if
all the KPIs were to be achieved while the second model was to distribute the allocated
budget set by U-XYZ, for all the activities planned for the agenda. The result showed
that in order to achieve the target, U-XYZ has to increase its budget allocation by
RM2.164 million. Otherwise, U-XYZ can only expect to obtain 1.578 out of 1.593 points
that is required to be achieved.
Lightning is among the most deadly natural phenomena to mankind. This phenomenon
is seen to increase globally as well as in Malaysia. Lightning does strike open areas
such as playing fields and playgrounds and these areas are places people gather.
Sensors that can detect the early occurrence of lightning have been developed for
detecting approaching lightning activity in this project. The main objective is to provide
early lightning warning system to the public and hence to reduce the number of
fatalities due to lightning strike. The warning circuit was designed and simulated using
Multism11. Basic operational method of the circuit is based on the comparative
voltage method using LM339N integrated circuit comparator (IC). Light Emitting Diodes
(LEDs) were used as indicators to indicate if the incoming voltage level is higher or
lower than that of the safety level.
In accordance upon conservation efforts, this research emphasizes on prevention of
environmental pollution and considers the elements of sustainable of infrastructure
construction materials, which is interlocking pavement block. The development of this
innovative product apply the concept of 3Rs and waste to wealth by using the
agricultural waste product, coconut shell, where widely available with very minimum
cost worldwide especially in tropical country such as India, Indonesia, Philippines,
Thailand and Malaysia. The main objective of this research is to produce an
environmental friendly product with a good quality, low cost and lightweight known as
Green Interlocking Pavement (GIP Block). The chemical composition of coconut shell
ash and ordinary Portland cement being identified and compared to know whether it
is able to react as a good binder in the mixture or not. The quality of GIP Block
considered is compressive strength, water absorption and bulk density. All the blocks
were curing in seven and 28 days before implementing the entire test. The existing
interlocking pavement used as bench mark and GIP Block 0% of proportion of coconut
shell ash used as control variables. The specimen of the interlocking pavement
prepared in this research is 10%, 20% and 30% proportion of coconut shell ash to
partially replace the quantity of cement. The ratio of the interlocking pavement apply
in this research is 1:2 which stand for one part cement and two part of sand. The
findings withdrawn from this research are: first, the chemical characteristic of the
coconut shell ash and cement. Second, the value of bulk density slightly reduces as the
percentage of coconut shell ash increases. Third, the additional of coconut shell ash to
partially replace the quantity of cement in the product reduce the compressive
strength and increase the percentage of water absorption.