Electric field changes generated by the preliminary breakdown for the negative cloud-to-ground lightning flashes in Malaysia and Sweden

We present the study of the electric field changes generated by the preliminary breakdown for negative cloud-to-ground lightning flashes in Malaysia and Sweden concerning the association of slow field changes associated in preliminary breakdown process. We examined the total of 1685 negative cloud-to-ground lightning flashes from the total of 39 thunderstorms by recording the slow electric field, fast electric field and narrowband radiation field at 3 and 30 MHz signals simultaneously. Our results show that there is a pre-starting time, i.e. the duration between the first preliminary breakdown pulse and slow field changes starting point, which is found to be after the first preliminary breakdown pulse. The pre-starting time has the arithmetic mean and geometric mean range from 1.4 – 6.47 and 1 – 3.36 ms, respectively. The mean values of pre-starting time in Malaysia are greater than the values observed in Sweden by more than a factor of 3. From the two data sets show that the slow field changes never start before the preliminary breakdown. Furthermore, the use of single-station electric fields measurement with high resolutions of 12 bits transient recorder with several nanosecond accuracy allow one to distinguish the slow field changes generated by preliminary breakdown, which preceded the negative first return stroke, between tens to hundreds of milliseconds of pre-return stroke duration

Characterizations Of Ground Flashes From Tropic To Northern Region

This thesis portrays new information concerning the cloud-to-ground (CG) lightning flashes or ground flashes produced by thunderclouds. It emphasizes the importance of characterizing lightning studies as the relationship between lightning mechanisms, and of incorporating the influence of geographical location, latitude and storm type. Sweden, Malaysia and USA were chosen as the main locations for field experiments in 2009 to 2011 to gather a significant number of negative and positive CG flashes. This work provided data on a total of 1792 CG lightning flashes (1685 negative and 107 positive ones) from a total of 53 thunderstorms by monitoring both the slow and the fast electric field and the narrowband radiation field at 3 and 30 MHz signals simultaneously. This thesis is comprised of: (i) the relationship of the Low Positive Charge Region (LPCR) and Preliminary Breakdown Pulse (PBP) trains to the occurrence of negative CG, (ii) slow field changes generated by preliminary breakdown processes in positive and negative ground flashes, and (iii) the occurrence of positive and negative ground flashes. It was revealed that the PBP train appeared have a higher strength in the in Sweden. The strength of the PBP train was caused by the LPCR; in contrast, weak PBP trains were characteristic in tropical countries constituting insignificant LPCR and needing little energy to break the “blocking” agent to allow the flash to propagate downward to the ground. The second contribution concerns the characteristics of the PBP train mentioned; this includes novel information for Malaysia. Further, it is stated that there are some different characteristics in the PBP trains in Johor, Malaysia and Florida, USA. The studies of slow field changes generated by preliminary breakdown processes clarifies unclear features concerning the starting position of slow field changes generated by preliminary breakdown processes in positive and negative ground flashes. It was found that the slow field changes did not occur before the initial process of the commencement of preliminary breakdown. Single-station electric field measurements incorporating narrowband radiation field measurement and high resolution transient recording (12 bits) with an accuracy of several nanoseconds, allows one to distinguish between the intracloud activities and the preceding processes of ground flashes. The results for the interstroke intervals, amplitude distribution of subsequent return-stroke (SRS) and the number of strokes per flash in the tropics, subtropics and northern regions were similar. Finally, a significant number of positive return-stroke (RS) electric fields provided statistically significant information on the characteristics of these strokes

Significant Lightning Stroke Count in Negative Ground Flashes Featuring the Relationship of Preliminary Breakdown and The First Return Stroke

The separation duration of Preliminary Breakdown to the first Return Stroke (PB-RS duration) and the ratio between the highest amplitude pulse of Preliminary Breakdown and the first Return Stroke pulse (PB/RS ratio) have become parameters for determining the relationship between lightning ground flashes with physical changes such as the latitude effect, regional and thunderstorm successfully by many researchers. This paper presents a novel finding for determining the occurrences of a lightning strike or stroke count in a negative ground flash with a duration of two seconds by using the primary tool mentioned above. Stroke count information in a lightning ground flash is crucial for power circuit breaker settings for power system protection. In this present study, 83 broadband radiation electric fields (or fast fields) gathered using a 12-bit high-speed transient recorder (HDO 4024) with a resolution of tens of nanoseconds and 12.5 MS/s. Interestingly, the PB/RS ratio with similar latitudes is consistent despite different monsoon measurements. The PB-RS duration, on the other hand, has two factors longer during the Southwest monsoon than during the Northeast monsoon. The weak pulses train (<20) shows a longer duration of PB-RS and produces more stroke count than the strong one (>100). By providing the significant stroke count under different variations of Northeast monsoon, this study allows power engineers to decide the significant parameter set up in the circuit breaker system. However, it would be more remarkable if one could provide bulky data for this specific study

Significant Lightning Stroke Count in Negative Ground Flashes Featuring the Relationship of Preliminary Breakdown and The First Return Stroke

The separation duration of Preliminary Breakdown to the first Return Stroke (PB-RS duration) and the ratio between the highest amplitude pulse of Preliminary Breakdown and the first Return Stroke pulse (PB/RS ratio) have become parameters for determining the relationship between lightning ground flashes with physical changes such as the latitude effect, regional and thunderstorm successfully by many researchers. This paper presents a novel finding for determining the occurrences of a lightning strike or stroke count in a negative ground flash with a duration of two seconds by using the primary tool mentioned above. Stroke count information in a lightning ground flash is crucial for power circuit breaker settings for power system protection. In this present study, 83 broadband radiation electric fields (or fast fields) gathered using a 12-bit high-speed transient recorder (HDO 4024) with a resolution of tens of nanoseconds and 12.5 MS/s. Interestingly, the PB/RS ratio with similar latitudes is consistent despite different monsoon measurements. The PB-RS duration, on the other hand, has two factors longer during the Southwest monsoon than during the Northeast monsoon. The weak pulses train (<20) shows a longer duration of PB-RS and produces more stroke count than the strong one (>100). By providing the significant stroke count under different variations of Northeast monsoon, this study allows power engineers to decide the significant parameter set up in the circuit breaker system. However, it would be more remarkable if one could provide bulky data for this specific study

Investigation of Zero Crossing Detection for First Return Stroke in Negative Cloud-to-Ground Lightning Flash

This paper aims to investigate the minimum threshold for zero crossing detection of the first return stroke in negative cloud-to-ground lightning flashes. The uncertainty for a minimum threshold to be set into a programmed software for an automatic zero crossing detection motivated the author to overcome the problem. The software was built-in MATLAB. The development of the software considered the important parameter of lightning strike from the preliminary breakdown stages until the first return strokes. A single station measurement was setup in Ayer Keroh, Malacca. 41 samples of duration of the zero crossing time were recorded by using Lecoy HDO4024 with 5 MS/s. The results showed that the minimum threshold for zero crossing detection was 40µs with 82.9% accuracy. In conclusion, the minimum threshold of zero crossing detection of the first return stroke in negative cloud-to-ground was determined

Comparative study on preliminary breakdown pulse trains observed in Johor, Malaysia and Florida, USA

In this paper, the preliminary breakdown (PB) pulse train preceding the negative first return stroke (RS) is recorded using a broad band antenna system. These analyses were carried out in Johor Bahru, Malaysia and Florida, United States. This is a novel initiative at examining and identifying the characteristics of the PB pulse trains in the negative cloud-to-ground flashes observed in Malaysia. The arithmetic mean of the total pulse train duration is 12.3 ms and the weighted arithmetic mean of the pulse durations and interpulse intervals are 11 s and 152 s, respectively. The arithmetic mean ratio between the maximum peak amplitude of the PB pulse and the peak RS electric field was 27.8%, and the corresponding value in Florida was 29.4%. The arithmetic mean of the time duration between the most active part of the pulse train, and the RS was 57.6 ms in Malaysia and 22 ms in Florida. A qualitative comparison of our results with those obtained earlier in Sri Lanka, Sweden and Finland supports the hypothesis that the PBP/RS ratio is higher in the northern regions compared to the tropical regions

A Fuzzy- Pi - Based Torque Controller For Dtc Of Induction Motor Drives

lt is well established that the implementation of conventional DTC drive consisting of hysteresis-based torque controller suffers from high torque ripple and variation in switching frequency problems. One of the many approaches to tackle this problem is by introducing a non-hysteresis-based torque controller. This paper presents the simulation and analysis of a proposed fuzzy PI-based torque controller for DTC of induction motor drives. Comparisons and analysis between the proposed controller and the hysteresis- and PI -based controllers are presented. The results show that the proposed controller managed to reduce the torque ripple and produce a constant device switching frequency

Combination of narrow bipolar pulses and attempted leaders in Melaka, Malaysia

This paper presents the characteristic of the positive attempted leaders preceded by positive narrow bipolar pulses (NPBPs). Attempted leaders are the preliminary breakdown process with no subsequent event (return stroke). On the other hand, narrow bipolar pulse is the lightning event commonly isolated and produces a strong electromagnetic field (in a short period). Attempted leaders hardly occurred in the tropics, and the preceding of the NBP (the combination) should be considered unique. In this present study, we found four samples in which the arithmetic means of duration of NPBPs pulse was 32.19 µs, with separation between the positive attempted leader was 1.86 ms apart. For the positive attempted leader, the arithmetic means of the whole pulse train, individual pulse and interval pulse of positive attempted leaders were 3.47 ms, 29.66 µs and 486.53 µs, respectively. The pulse train in this study seems to fade out fast compared to the isolated positive attempted leader pulse train. Next, the NPBP's pulse duration in this study shows well in agreement with the type of isolated NPBPs indicates that the association does not affect its pulse duration characteristic already present in the title

A Low Cost Wireless Data Acquisition System for Distribution Automation System

This paper presents the design and development of a 16F877A microcontroller-based wireless data acquisition system. Besides that, this paper also presents study of the possibility of different existing methodologies that linked to field data acquisition from distribution automation systems. Various existing data transmission technique was studied, especially for wireless systems such as satellite, radio, GSM and paging. The hardware and software implementation are described in this paper. The system will be used for reading, storing and analyzing data that obtained from DAS. The wireless communications are based on the GSM network. The laboratory results are compared with the simulation results to make the final conclusion of the algorithm function properly

Development of a novel fault management in distribution system using distribution automation system in conjunction with GSM communication

The paper develops and implement a novel fault management in distribution automation systems (DAS) at low voltage to enhance reliability of power for the consumers. The proposed fault management system is design based on GSM (global system for mobile) communication. The system has been equipped with current sensor as field data interface devices, microcontroller as remote terminal unit, GSM as communication network, computer as master terminal unit and visual basic as human interface (HMI) software. A fault management strategy is also designed to find out the fault location effectively without human intervention after a fault occurred. The laboratory results are compared with the simulation results to make the final conclusion on the functionality of the algorithm