Mohd Zainal Abidin Ab-Kadir

Modelling of lightning current in the case of striking to a tall structure

Lightning current is an important parameter that has to be considered. The different behaviour of lightning current depends on the way the lightning strikes either as a direct or indirect lightning strike. In this paper the modelling of the current as a result of a direct strike of lightning on a tall structure is considered. A few of up-to-date on current models, current functions, reflection factors, the return stroke velocity (RSV), the general equation representation of this case are reviewed. Also, through MATLAB software, the results of a case study are generated. The results show a good agreement with the measured values. In addition, the behaviour of the lightning current is evaluated at different heights of the lightning channel with respect to the top and bottom of a tall structure. Also, the lightning current at the top and bottom of the tall structure are observed for different values of the reflection factor. The results show that the peak of the lightning current along different heights of the channel with respect to the top and bottom of a tall structure decreases with increasing height of the channel. Also there is a time delay during the initial time period. Furthermore, the lightning current at the bottom of a tall structure has a high value of peak current and has an attenuation wave shape of current that compares with the lightning current at the top of the tall structure. As a result, this paper may provide benefit in evaluating the electromagnetic (EM) field since the behaviour of the lightning current on a tall structure is known.

Effect of the grounding system arrangement on the lightning current along tall structures

The behaviour of lightning current along tall structures is an important case to be evaluated. The behaviour is influenced by a few factors of which one is the ground or earth reflection factor. Previous studies have assumed that the ground reflection factor is a constant value and this value is usually used when evaluating the lightning current along a tall tower. This study presents the behaviour of lightning current along a tower, including variation in the value of the ground reflection factor. The simulation work is done by selecting the sum of two Heidler functions as a current channel base and a distributed source representation current is used to simulate the lightning current along the tower and channel. The ground reflection factor is calculated based on the correlation between tower and ground impedances whereby the ground impedance is dependent on a circle grounding system arrangement. The results indicate that by increasing the length of the rods, the value of the ground impedance decreases, but the peak value of the current along the tower is more dependent on the value of the ground reflection factor. It is shown that by increasing the length of the rods, the current peaks increase. Thus, the outcome of this study may be of benefit to Electrical Engineers to set an appropriate scheme of protection for the equipment which is installed along the tower, based on the effect of the grounding system arrangement for different conditions of soil resistivity.

Evaluation of lightning induced over-voltage due to variations of channel angle

Lightning can create lightning induced overvoltage (LIOV) on a power line. However, detailed considerations are needed concerning the evaluation behaviour of LIOV due to changes in channel angle which is referred to as an inclined lightning channel. The aim of this paper is to evaluate the behaviour of LIOV due to variations of channel angle. The LIOV was generated through the execution of an algorithm in MATLAB. Results indicate that the behaviours of LIOV are direct and show a linear relationship with an increasing channel angle which is an inclined angle and observation point angle. On the other hand, the effect on the LIOV of an increasing channel angle due to the return stroke velocity decreases at the highest velocity. As a result, the outcome of this paper could be useful for electrical power designers for the fast estimation of LIOV peak voltages without recalculation of the LIOV and to assist in the appropriate planning of protection schemes.

On the performance of a polycrystalline PV panel under different impulse voltages and temperatures

Lightning events are one of the factors that affect performance of a solar power system either by direct or indirect strikes. When lightning strikes directly to a panel, it can affect function and life cycle of the panel. Therefore, considering the electrical performance characteristics such as open-circuit voltage, short-circuit current, and maximum power of the solar panels under high voltage conditions is an important issue. In this paper, the effect of impulse voltage on the change of electrical behaviour of a polycrystalline solar panel is studied. The experimental platform is tested by a lightning impulse generated over a range of 100 kV to 300 kV. The results revealed that as the lightning impulse voltage is increased, the maximum power output gradually decreases. The performance of percentage difference from normal between 100 kV to 300 kV increased to 10.02 % for the maximum power output and the graph showed an increasing non-linear trend. After testing with lightning impulse voltages, the electrical performance of the solar panel under different thermal conditions (temperature) was evaluated in the range of 25 °C to 70 °C and the results are discussed accordingly. When the different temperatures were applied, efficiency of the polycrystalline panel continuously degraded. The percentage difference of the maximum power between samples of 100 kV to 300 kV at 70 °C increased from 2.09 % to 7.11 %.

On the effect of lightning on a solar photovoltaic system

A solar PV system was modelled and the effect of lightning striking different parts of a solar PV system was studied and the results discussed appropriately. Lightning strikes of different wave shapes and different magnitudes were considered. The purpose of this research is to observe the transient current and voltage that appears in a solar PV system when struck by lightning. The results show that a transient current will appear at the nearest point to the lightning strike and the value of the transient current is same as the lightning current, while the transient voltage will appear at AC side at any point of lightning strike. This could damage the inverter which requires a high cost to repair or replace. The information of this paper can be useful to decide a suitable lightning protection system before installing a solar PV system.

The influence of lightning induced voltage on the distribution power line polymer insulators

Protection of medium voltage (MV) overhead lines against the indirect effects of lightning is an important issue in Malaysia and other tropical countries. Protection of these lines against the indirect effects of lightning is a major concern and can be improved by several ways. The choice of insulator to be used for instance, between the glass, ceramic or polymer, can help to improve the line performance from the perspective of increasing the breakdown strength. In this paper, the electrical performance of a 10 kV polymer insulator under different conditions for impulse, weather and insulator angle with respect to a cross-arm were studied (both experimental and modelling) and the results were discussed accordingly. Results show that the weather and insulator angle (with respect to the cross-arm) are surprisingly influenced the values of breakdown voltage and leakage current for both negative and positive impulses. Therefore, in order to select a proper protection system for MV lines against lightning induced voltage, consideration of the local information concerning the weather and also the insulator angles with respect to the cross-arm are very useful for line stability and performance.

Effects of RTV coating on the electrical performance of polymer insulator under lightning impulse voltage condition

Located near the equator, Malaysia is a country with one of the highest lightning densities in the world. Lightning contributes to 70% of the power outages in Malaysia and affects power equipment, automated network systems, causes data losses and monetary losses in the nation. Therefore, consideration of insulator evaluation under lightning impulses can be crucial to evaluate and attempt to overcome this issue. This paper presents a new approach to increase the electrical performance of polymer insulators using a Room Temperature Vulcanisation (RTV) coating. The evaluation involves three different settings of polymer insulator, namely uncoated, RTV type 1, and RTV type 2 upper surface coatings. All the insulators were tested under three different conditions as dry, clean wet and salty under different impulse polarities using the even-rising test method. The voltage breakdown for each test was recorded. From the experiment, it was found that the effectiveness of the RTV coating application became apparent when tested under salty or polluted conditions. It increased the voltage withstand capabilities of the polymer insulator up to 50% from the basic uncoated insulator. Under dry and clean conditions, the RTV coating provided just a slight increase of the breakdown voltage. The increase in voltage breakdown capability decreased the probability of surface discharge and dry band arcing that could cause degradation of the polymeric material housing. The RTV type 1 coating was found to be more effective when performing under a lightning impulse. The findings might help the utility companies improve the performance of their insulators in order to increase power system reliability.

Effect of soil resistivity on magnetic field in the case of lightning strike to a tall structure

When a tower is struck by lightning, an induced voltage can generate in conducting objects within its vicinity. This phenomenon is due to the interaction between the electromagnetic field of the lightning with the object. The magnetic field is part of this field. Previous studies have shown that the magnetic field is affected by ground reflection coefficient factors that are usually taken as constants. However, the ground reflection coefficient factors have correlation with tower and ground impedance whereby the ground impedance can be determined based on soil resistivity and grounding system. This paper investigates the effect of soil resistivity on the value of magnetic field for a case of lightning strike on tall structures. Lightning current has been modelled accordingly and a set of equations is proposed to evaluate the magnetic field. Also, the effects of soil resistivity on the value of ground reflection coefficient factor consequently of the magnetic peak have been investigated. The results indicate that the magnetic field changes substantially with a variation of the soil resistivity. The magnetic field peak also has a strong correlation with the changes of soil resistivity as well as the fast front time of the channel base current. The outcome of the result of this paper will be beneficial to utility companies in determining the appropriate level of lightning protection since the magnetic field will be a result of induced voltage when have interaction with power lines.

Lightning fatalities and injuries in Malaysia from 2008 to 2015

This study examined the risk of lightning-related deaths and injuries in Malaysia between January of 2008 to July 2015. The majority of lightning-related injuries and fatalities occurred during the months of April and May. Most lightning related casualties reported in the statistics since 2008 occurred in the states of Melaka and Selangor in the western coastal belt. The majority of victims, were engaged in outdoor and sports activities when injured or killed by lightning incidents.

A comparison of lightning human fatalities between Malaysia and United States

This study analyzed and compared the lightning related casualties in Malaysia and United States. United States as a developed country is reported with 0.3 deaths per million per year after 1970 comparing to lesser-developed areas such as Malaysia with an annual lightning fatality rate of 6 deaths per million. The comparison and analysis were made based on the rural-urban setting and the six types of activities locations defined as agriculture, indoors, outdoors, recreation, small structures (i.e. vehicle, open-sided shelter, shed) and sports. The results for the both countries were discussed in terms of their differences and similarities.