Norazhar Abu Bakar

A review of dissolved gas analysis measurement and interpretation techniques

Dissolved gas analysis (DGA) is used to assess the condition of power transformers. It uses the concentrations of various gases dissolved in the transformer oil due to decomposition of the oil and paper insulation. DGA has gained worldwide acceptance as a method for the detection of incipient faults in transformers.

A novel method of measuring transformer oil interfacial tension using UV-Vis spectroscopy

In this article we propose an alternative method of measuring the IFT of transformer oil, using ultraviolet-to-visible (UV-Vis) the IFT of an oil sample and its spectral response parameters (bandwidth and peak absorbance).

Malaysian vehicle license plate recognition using double edge detection

Vehicle plate number is a unique combination of characters and numbers. Hence, it has been used in various application as personal identification such as for parking system identification, security monitoring system and etc. This paper illustrated the double edge detection technique in order to enhance the vehicle plate image, before character recognition process. Firstly, the vehicle image is captured, and then it will be re-sized and cropped until the resolution of image is 300×300. After the re-sized process, First Edge detection is applied to the image. Threshold of black and white are 59 and 60 respectively used to change the image into black and white colour only. Next, Second Edge detection is used to remove the unwanted image and only remain the plate number in white colour. MATLAB software is used in this experiment.

Dynamic simulation of sit to stand exercise for paraplegia

This paper describes on developing a dynamic humanoid model of sit-to-stand (STS) movement. Visual Nastran software is used to develop a humanoid model, while the humanoid movement is controlled by MATLAB/Simulink to perform sit-to-stand activity. Two control strategies are implemented in this study, which are PID controller and fuzzy logic control (FLC). The results produced by both controllers are compared. The torque applied at each joint during STS movement is investigated. Results show both controller can be used in order to control humanoid model movement, but with FLC, the error between desired trajectory and actual has been reduced.

Horizontal Distance Identification Algorithm for Sit to Stand Joint Angle Determination for Various Chair Height Using NAO Robot

This paper presents the development of an autonomous Sit To Stand (STS) motion using NAO robot. NAO robot hip limitation will emulate the limitation faced by people having STS problem. To perform the motion, three main steps have been developed (1) horizontal distance identification, (2) joint angle determination, and (3) stability control. This step was developed based on Alexander STS technique. Results show that NAO robot is able to achieve halfway stand up from chair height between 9.6 and 12.7 cm automatically. The robot’s best performance is at 12.7 cm height with swinging time of 0.52 s in experiment and 0.2914 in simulation. The developed system will contribute to the development of exoskeleton, rehabilitation and evolution of humanoid robot. This system also enhances NAO’s ability for medical study on STS motion or as tools in searching for the best chair design.

Improvement of DGA interpretation using scoring index method

Dissolved gas analysis (DGA) is the most effective method to detect incipient faults in power transformers. It uses the concentrations of various gases dissolved in the transformer oil due to decomposition of the oil and paper insulation. Gases such as hydrogen, methane, acetylene, ethylene, and ethane are generated as a results of oil decomposition, while carbon monoxide and carbon dioxide are generated due to the paper degradation. In the meantime, faults such as partial discharge, overheating, and arcing produce a range of gases. The concentrations of these gases can be used to identify faults and estimate their severity. Various techniques have been developed to interpret DGA results such the key gas method, Doernenburg, Rogers, IEC ratio-based methods, Duval triangles, and the latest Duval Pentagon methods. However, each of these techniques relies on the accumulated knowledge and experience of experts rather than quantitative scientific models, therefore different diagnoses may be reported for the same oil sample. Hence the accountability of the judgment is questionable if it only relies on one interpretation technique. This paper proposes the use of scoring point method to improve the accountability of DGA interpretation process. In this context, DGA results of several transformer oil samples are analyzed with four existing interpretation techniques; Doernenburg, Rogers, IEC, and Duval triangle methods from which a scoring index is developed for all fault types. Based on this analysis, each technique is assigned with specific weighting factor. The summation of scoring point times weightage represents the scoring index for particular faults. The proposed method is validated through DGA historical data of various transformers of pre-known health condition and life span. Results show that the proposed method can increase the accuracy of the DGA interpretation process.