Resistive leakage current based condition assessment of metal oxide surge arrester (MOSA) is one of the most extensively employed technique to monitor its degradation. An extraction method is customarily required to extract the resistive component from the total leakage current. The existing methods to extract the resistive current are complex and less accurate. Therefore, this paper describes a simple and accurate circuit-based method to extract the resistive current using equivalent model and measured leakage current of the arrester. The accuracy of the proposed method is validated through experimental results on ABB’s 120 kV surge arrester, EMTP and QuickField software simulations. The performance of the method is also analyzed and verified experimentally on 72, 180 and 240 kV rated ABB’s surge arresters. The obtained results of resistive leakage current have shown the maximum error of 0.001%. Simple and easier computational steps with higher accuracy are the key benefits of the proposed technique.

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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.

as electricity markets are liberalized, consumers become exposed to more volatile electricity prices and may decide to modify the profile of their demand to reduce their electricity costs. Therefore, accurate prediction of consumers' reaction to the electricity price changes can be effective in order to increase the profits of producers and consumers. This paper classifies the variety of consumers' reaction to the electricity price changes. Then, the price elasticity is estimated for a real network in Iran based on collected data from statistical analysis. To achieve this, the consumption period (1 day) is divided into three groups (Peak, Off-peak, Low) and mathematical definition model of elasticity is applied to estimate price elasticity. Results revealed that the highest elasticity in peak period belongs to residential customers due to their highest demand-level in the peak period.

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.