Characteristics of cloud-to-ground lightning based on electric field measurement and high-speed image observation

• Main Author: Ramlee, Nor Asrina
• Format: Thesis
• Language: English
• Published: 2022
• Subjects: TK Electrical engineering. Electronics Nuclear engineering
• Online Access: http://eprints.utm.my/id/eprint/102777/1/NorAsrinaRamleePSKE2022.pdf.pdf; http://eprints.utm.my/id/eprint/102777/; http://dms.library.utm.my:8080/vital/access/manager/Repository/vital:152229
• Institution: Universiti Teknologi Malaysia

Malaysia is one of the countries with the highest lightning activities in the world. Thus, lightning monitoring and protection system are vital to safeguarding buildings, communication systems, and electronic equipment throughout the country. Nevertheless, research on the characteristics of lightning in Malaysia is relatively limited, with the majority of published studies focusing solely on West Malaysia. The previous lightning studies were confined to electric fields alone but in this study, however, investigation of electric field characteristics from Cloud-to-Ground (CG) lightning in Malaysia are based on in situ electric field measurement together with high-speed image observation. Field studies were carried out in Malacca (West Malaysia) and Sarawak (East Malaysia) to measure various lightning parameters of negative CG lightning, including the temporal characteristics of the lightning strokes, pulse train (PT), and preliminary breakdown pulse (PBP). Based on the image results, 68% of the captured lightning occurrences exhibited tortuosity, indicating that the typical type of lightning channel in Malaysia is tortuous in behaviour. It was also revealed that 70% of lightning was terminated in a new location. Throughout the investigation, single stroke lightning was the most frequently observed event, accounting for 76% of the recorded lightning images. Averagely, vertical lightning had a longer stroke interval and First Return Stroke (FRS) interval compared to that of tortuous lightning. The PT observed in this study was analysed using the time-domain and frequency-domain. It can be inferred that PT occurrences initiate Subsequent Return Strokes (SRS) since 99.8% of them are found to precede SRS. Interestingly, out of 930 PT samples analysed, this study observed twelve different types of PT. In the time-domain, the PT observed in this work could be interpreted as any regular or irregular PT with varying amplitudes that lasted an average of 653 µs and occurred 25 ms before the next SRS. Additionally, the PT was recorded at a frequency range of 7.7–403.2 kHz and generated an average of 184.6 (V/m)2 peak power, which can reach up to 2170 (V/m)2. The field campaign in Sarawak also recorded other crucial lightning parameters, including normal electric field ( ), zero-crossing time ( ), zero-to-peak rise time ( ), and 10–90% rise time ( ) of return strokes (RS), which were 40 V/m, 80.1 µs, 7.6 µs, and 4.1 µs, respectively. This study discovered variations in lightning characteristics when striking over sea and land, and its correlation to propagation distance. Furthermore, 52% of the PBP was detected from the data collected in Sarawak. The PBP lasted an average of 3 ms and was 24 ms apart from the FRS. Remarkably, this study successfully carried out the first lightning measurement in East Malaysia as well as discovering more about the characteristics of lightning across Malaysia.