Chin Leong Wooi

A Comparative Study on the Positive Lightning Return Stroke Electric Fields in Different Meteorological Conditions

Positive cloud-ground lightning is considerably more complex and less studied compared to the negative lightning. This paper aims to measure and characterize the significant parameters of positive return strokes electric field, namely, the zero-to-peak rise time, 10–90% rise time, slow front duration, fast transition rise time (10–90%), zero-crossing time, and opposite polarity overshoot relative to peak. To the best of the authors’ knowledge, this is the first time such detailed characteristics of positive lightning in Malaysia are thoroughly analyzed. A total of 41 positive lightning flashes containing 48 return strokes were analyzed. The average multiplicity is 1.2 strokes per flash. The majority of positive lightning was initiated from the primary positive charge rather than as a byproduct of in-cloud discharges. The cumulative probability distribution of rise time parameters, opposite polarity overshoot relative to peak, and slow front amplitude relative to peak are presented. A comparison between studies in four countries representing tropic, subtropic, and temperate regions was also carried out. Measured parameters in Florida, Sweden, and Japan are generally lower than those in Malaysia. Positive lightning occurrences in tropical regions should be further studied and analyzed to improve our current understanding on positive return strokes.

A Review of Recent Studies on Positive Lightning

Lightning is a natural phenomenon that has much impact on man and man-made systems. Lightning can be generally characterized as either negative return stroke (NRS) or positive return stroke (PRS). PRS have high peak currents and long continuing current that are responsible for more intense damage than negative return strokes. However, PRS are considerably less studied compared to NRS due the complexity and paucity of PRS. This study attempts to provide an overview of the positive lightning characteristic research in recent years. The review is classified into four groups, which are: preliminary breakdown pulse of positive lightning, compact intracloud discharge, positive leader and positive lightning return stroke. In spite of recent progress made in this area, our knowledge on the physics of positive lightning remains considerably poorer than negative lightning. Many questions regarding the characteristic of positive lightning and their properties cannot be answered without further research. It would be of great interest to examine the positive lightning parameters under different meteorological conditions as well.

Characteristic of preliminary breakdown preceding negative return stroke in Malaysia

This paper describes a study on the characteristics of preliminary breakdown pulses (PBPs) preceding negative return strokes. Such characterization is needed due to the lack of available data, especially for negative lightning, in Malaysia. Measurements were carried out in Johor Bahru, Malaysia in October 2014 using broadband antennas and a high resolution Picoscope. It was found that 84% of the negative return strokes (RS) were preceded by PBPs. 70% of the PBPs fit the BIL model and another 30% the BL model. The arithmetic mean of the PBP-RS interval is 13.2ms, which is about four times smaller compared to a similar measurement made during April to June, 2009. The difference may probably be due to a variation in the thundercloud formation which is dependent on the monsoon period in Malaysia. Further studies are required to characterize the PBPs and their relations with the monsoon period and with geographical region.

Modeling of Time of Arrival Method for Lightning Locating Systems

Various methods are used to locate cloud-to-ground lightning flashes. Even though a higher cost is incurred, a network of sensor stations is preferable to a single station due to the improved accuracy. For a single station measuring system, the accuracy of its analyses is mostly based on the chosen mathematical equations which can be solved in either linear or nonlinear mode. The sensitivity of the measuring equipment used is also particularly significant. This paper concentrates on the modelling of time of arrival (TOA) technique for locating a lightning flash by utilizing three broadband antennas. Consequently, by employing the developed model, the influences of geometric parameters on the accuracy of the model are evaluated. Therefore, a Matlab based simulation of the measuring system is developed. In the developed codes, randomly located lightning flash with its corresponding electromagnetic radiation was modelled. Results show that parameters such as lightning path shape, distance of the leader, and leader location can directly affect the accuracy of the TOA technique for extracting the azimuth and elevation.

Wavelet analysis of chaotic pulse trains prior to subsequent return strokes in Malaysia

This paper presents a wavelet transformation of chaotic pulse trains (CPTs) prior to negative subsequent return strokes in Malaysia. A total of 593 recorded waveforms were examined. Even though several hundred waveforms were identified as containing CPTs, only 47 waveforms with CPTs preceding subsequent return stroke were selected for analysis. 19 samples are classified as CPTs associated with dart or dart-stepped leader (Type 1 CPTs) with spectral and spread regions average frequency range of 34.8-154.3 kHz and 56.2-81.4 kHz respectively. 28 samples are classified as chaotic pulse trains alone (Type 2 CPTs) with spectral and spread regions average frequency range of 24.6-121 kHz and 40.3-62 kHz, respectively. The Type 1 CPTs tends to radiate at a higher frequency range compared to Type 2 CPTs. The maximum power radiated by the largest pulse in Type 1 CPTs is more than six times larger than that for the Type 2 CPTs. In addition, the Type 1 CPTs have larger electric field variations, higher frequency, and higher power radiated spectrum compared to Type 2 CPTs. The reported radiated energy can be further compared with other lightning activities to give a better insight on the in-cloud breakdown processes prior to subsequent return strokes.

An Economic Assessment of Hybrid Renewable Energy for a Remote Area Electrification in Iran

The utilization of renewable resources is growing, in part due to the environmental impacts caused by fossil fuels. The largest sources of renewable energy are wind and solar and many predict that these energy sources will be increasingly used for distributed generation. In this paper, the feasibility is examined of a grid-independent system applied for a remote area electrification in Binalood, Iran. Traditional power systems for remote or rural areas are based on fossil fuels. After addition of renewable energy resources, solar energy applications have become popular in remote energy systems. The recent study and research works show that adding other possible renewable energy resources such as wind, hydro and biomass could make a hybrid system more cost-effective and environmentally friendly. Hence, in the present study, an overview of applied hybrid renewable energy system (HRES) for worldwide villages with special attention on Iran has been proposed to help present and future works for better achievement in this field. Furthermore sensitivity analyses are performed to determine the impact on performance of several key parameters: wind speed and fuel costs. HOMER was used to evaluate the feasibility of various hybrid systems. The results of a comprehensive feasibility data analysis along with its economic evaluation indicate that the wind-diesel hybrid system with battery storage is most efficient energy system for supplying this remote areas electrical energy demands.

Assessment of Series Compensator for Ferroresonance Damping in Power System

Nowadays power quality is a critical issue in power system. Moreover the connection of three-phase transformers through underground cables is growing fast in residential, commercial, industrial and rural applications. Due to this increasing situation, the possibilities of having a series connected capacitance and a non-linear inductance, and hence ferroresonance, become more probable. Ferroresonance can also occur in power transformers or reactors by capacitive coupling from neighbouring phases or lines. It is necessary to have a general idea about what would be the best preventive decisions to take in order to avoid unexpected surprises. It is necessary to have an accurate ferroresonance model so that a device that can smoothen the sharp effects of ferroresonance can be found. In this paper, the FACTS device, namely the static synchronous series compensator (SSSC) had been used to mitigate ferroresonance. Results show that using SSSC dramatically decreases and mitigates the ferroresonance shock as well as the instabilities of the network.

Cloud-to-Ground Lightning in Malaysia: A Review Study

Lightning has been the major cause of power interruptions in Malaysia. Malaysia is located near the equator having approximately 200 thunder days per year. It is known to be among the highest lightning activity country worldwide. TNB as the main power supply utility in Malaysia has made an effort to reduce the power interruptions via installation of Lightning Detection Network (LDN) in 1994. This paper presents the history leading to modern LDN that capture lightning radiation fields at multiple remote sensors. The network has undergone a series of improvement between 2004 and 2009 in response to evolving detection technologies and requirements. Recent analyses on actual performance of the current LDN are also summarized. The paper includes short and long term requirements for improving the lightning measurements needed to address some open scientific questions and fill the needs of emerging applications.

A review of modeling ageing behavior and condition monitoring of zinc Oxide Surge Arrester

The gapless Metal Oxide Surge Arresters (MOSA) have been available in the market for many years. Its primary function is to protect the equipment in the system against various electrical over stresses. A reliable condition monitoring of zinc oxide surge arrester is vital to its performance to ensure the continuity and reliability of power supply. It is known that voltage-current characteristics of zinc oxide varistors become degraded due to a series of stresses. Leakage current of the surge arrester can be increased by any increase of ageing level. This paper presents a review and comparison of various techniques for condition monitoring of MOSA. A comparative analysis is carried out in which the advantages and disadvantages for each technique are assessed. Previous review demonstrates some techniques which are simple in setup and measurement but its accuracy depends on the sensitivity and accuracy of the measuring instruments. Furthermore, moreover, some methods are used to simultaneously record the voltage and leakage current waveforms, but these techniques are usually hard to apply in practice.

Implementation of Wireless Thermal Camera Remote Control System

Thermographic inspection is a very safe and non-invasive monitoring technique, widely used in electrical substations and other power plants. A thermal image can be obtained to help in identifying abnormal heating regions in power equipment. Under high voltage circumstances, it is a hazard for personals to capture the image at a close distance from the power equipment. This paper described the development of a remote control monitoring system for a thermal camera. XBEE is a new and popular protocol for wireless communication because of its low power assumption, large network capability and the ability to organize a network automatically. 10 samples data are collected within the 30m and the successful transfer rate reached 98.89%. Remote control of thermal camera helps human keep distance from the high electric field and at the same time convenient for a user to conduct online condition monitoring in order to prevent any accident in power station.