Papers by Mehrdad Mokhtari
This paper describes a study on the characteristics of preliminary breakdown pulses (PBPs) preced... more 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.
International Transactions on Electrical Energy Systems, Oct 9, 2015
Archives of Electrical Engineering, Sep 1, 2016
International Transactions on Electrical Energy Systems, Sep 12, 2016
Applied Mechanics and Materials, 2016
Lightning has been the major cause of power interruptions in Malaysia. Malaysia is located near t... more 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.
International Journal of Electrical and Computer Engineering, Apr 1, 2016
International Journal of Electrical and Computer Engineering, Apr 1, 2016
IEEE Transactions on Electromagnetic Compatibility, 2017
Distributed Generation Systems, 2017
This chapter is assigned to define a distributed generation (DG) resource. The features and the o... more This chapter is assigned to define a distributed generation (DG) resource. The features and the operation of DG are also explained. The technologies used in DG are also explained. The advantages and disadvantages of DG are given.
Archives of Electrical Engineering, 2016
Grounding electrode resistance non-linearly changes under impulse conditions due to soil ionisati... more Grounding electrode resistance non-linearly changes under impulse conditions due to soil ionisation phenomenon. Several models have been proposed to model soil ionisation for grounding electrodes applications. However, to date, there is yet an attempt made to compile all these works into a comprehensive review article. Therefore, this paper is written with the objective of summarizing all related works in this field as a one- stop reference. With reference to the literature, this paper is written to summarize the working principles of the soil ionisation models as well as the accuracy and performance analysis of the models. This paper, particularly highlights the deficiencies of the available models in terms of accuracy and performance. This knowledge will contribute to the development of a new accurate and efficient soil ionisation model.
International Transactions on Electrical Energy Systems, 2016
International Journal of Electrical and Computer Engineering (IJECE), 2016
International Journal of Electrical and Computer Engineering (IJECE), 2016
2015 IEEE Conference on Energy Conversion (CENCON), 2015
This paper describes a study on the characteristics of preliminary breakdown pulses (PBPs) preced... more 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.
Applied Mechanics and Materials, 2016
Lightning has been the major cause of power interruptions in Malaysia. Malaysia is located near t... more 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.
International Transactions on Electrical Energy Systems, 2015
IEEE Transactions on Power Delivery, Feb 1, 2015
The behavior of a grounding system can be predicted by using either the electrical equivalent cir... more The behavior of a grounding system can be predicted by using either the electrical equivalent circuit models or electromagnetic computation. Despite its advantages over the latter, the equivalent circuit model fails to accurately predict the behavior under transient conditions due to the absence of two key factors, namely: 1) the current rate-of-rise and 2) soil ionization. This paper proposes a method to enhance the performance of the equivalent circuit model by taking into consideration of both mentioned factors. It is discovered that by using the proposed method, the estimated values of R and L of the equivalent circuit model are improved. The computed inductance dynamically changes with the change in the lightning current parameters, thus improving its accuracy for all current rate-of-rise conditions. The soil ionization effect is implemented as recommended by CIGRE, and this further improves the accuracy of the model. As a result, the voltage response of the model becomes more accurate and comparable to the electromagnetic computation results. Another important feature of the proposed model is that it can be directly applied or connected to power system equipment. Thus, an accurate grounding system effect on the transient performance of key power equipment, such as surge arresters, can be obtained.
Applied Mechanics and Materials, 2016
International Transactions on Electrical Energy Systems, 2015
Archives of Iranian medicine
Contribution of neuroinflammation and epilepsy in the mature brain has elicited contradictory res... more Contribution of neuroinflammation and epilepsy in the mature brain has elicited contradictory results with either excitatory or inhibitory effects. The amygdala is one of the main parts of the limbic system susceptible to insults that lead to neuroinflammation and epilepsy. This study evaluates the effect of chronic inflammation of the rat amygdala induced by lipopolysaccharide (LPS) on kindling epileptogenesis. LPS (5µg/rat) was infused once daily into the basolateral amygdala (BLA) of adult rats. Daily electrical stimulation (150 - 300 µA, 100 Hz, monophasic square wave stimulus of 1 msec per wave, 2 sec duration) was delivered into BLA 30 min after LPS injections until the animals became fully kindled. LPS had no significant effect on the development of focal and generalized seizures. The type of neural system exposed to LPS and its specific electrophysiological properties seems to ascertain the final excitatory or inhibitory outcome.
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Papers by Mehrdad Mokhtari