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The Coupling of Atmospheric Electromagnetic Fields with Biological Systems
Published in Shoogo Ueno, Tsukasa Shigemitsu, Bioelectromagnetism, 2022
Tsukasa Shigemitsu, Shoogo Ueno
Summer thunderclouds occur at a height of 0.5–1 km above the ground and often consist of several parallel cloud masses that are about 10 km wide and 10–13 km high. Thunderclouds go through three stages of development, maturity, and weakening. Each individual cloud mass is called a thundercloud cell, and within each cell, convection occurs. These convection currents create violent updrafts with wind speeds of up to 30 m/s and these currents carry water vapor up to 10–15 km in the air. The water vapor is condensed by the cold air above, but is quickly cooled to super-cooled water droplets. In addition, if there is a nucleus of dust or other particles, it will freeze into ice flakes. The super-cooled water droplets collide with the ice flakes and crystallize, growing into large powdery ice particles. As the ice particles grow and become heavier and cannot be supported by the updraft, they begin to fall, dragging the surrounding air with them and causing downward airflow. This is how violent convection occurs. In this convection storm, water droplets and ice fragments collide with each other, splitting and becoming electrically charged. Thus, positive charges are distributed above the cell and negative charges are distributed below. As a result, a large potential difference of tens of volts to 100 million volts is generated between the cloud base and the ground surface. A lightning strike is when the electric charges accumulated in the thundercloud discharge toward the earth, and the current of a single lightning strike reaches several thousand amperes to several tens of thousands of amperes.
Lightning exposure of oil tanks with changing roof position
Published in Vladimir Litvinenko, Advances in Raw Material Industries for Sustainable Development Goals, 2020
Lightning is a natural phenomenon that is as old as the earth itself. Lightning strikes to structures on earth may be very dangerous to facilities, and equipment depending on the level of risk associated with the structure as a function of the geographic location, nature and dimension of the structure, and adjoining facilities. The geographic location determines the number of lightning flashes that the structure is exposed to annually. Lightning strike can either be direct i.e. when the flash terminates on a structure or indirect, when the flash terminates near the structure and connected services. Out of 102 floating roof tank fires studied in China by Ren et al. (2012), it was discovered that 65% of these were due to direct lightning strikes (Wei et al., 2018). Lightning strike to structures and equipment can result in damage, fire, and even injury to living beings. A lightning flash can either be negative or positive, and fact as shown that about 90% of lightning flashes are of the negative type while positive flashes carry about six times more current than the negative type (Afa, 2012, Akinyemi et al., 2014).
The Earth Station
Published in Jerry D. Gibson, The Communications Handbook, 2018
Reliability of the power is another major concern for the Earth station. Depending on the application, different levels of primary and backup power systems may be required. To increase reliability, some Earth stations use two different sources of commercial power from the utility company that are fed from different grids. The electrical service entrance must be properly sized by calculating the load for all anticipated equipment. The calculated load should include ancillary systems such as antenna deicing and heating, ventilation, and air-conditioning (HVAC) systems. The electric service entrance should also be equipped with surge protectors to help guard against equipment damage from lightning strikes. The Earth station equipment building or shelter should be designed so that sufficient room is provided for the power distribution equipment required. It is sometimes helpful to provide separate distribution for critical and noncritical loads. When backup systems are used, there are sometimes capacity limitations that require noncritical systems to remain off-line during power outages.
Characteristics of a multi-stroke “bolt from the blue” lightning-type that caused a fatal disaster
Published in Geomatics, Natural Hazards and Risk, 2019
Xiangpeng Fan, Yijun Zhang, Qiyuan Yin, Yang Zhang, Dong Zheng
Fuelberg et al. (2014) measured the horizontal development distance of different types of lightning channels that extend from a thunderstorm cloud; three are used for the ground flash process, and three are used for the cloud flash process. There are two ways to measure the horizontal development distance of a lightning channel: the horizontal distance from the edge of the anvil to the lightning strike point (0 dBz) or from the edge of the precipitation area (18 dBz) to the lightning strike point. Ward and Merceret (2004) defined a cloud body as having an edge characterized by a thin stratiform cloud with a radar echo of 0 dBz. Merceret et al. (2005) and Punkka and Bister (2005) proposed that the precipitation area were defined as the area of a cloud with a radar echo that is greater than 18 dBz.
Predicting the Class of Salt Contamination for Wind Turbine Blade under a Lightning Strike Using Fuzzy Inference System and Probabilistic Neural Network
Published in Electric Power Components and Systems, 2023
Shenglu Huang, Jiannfuh Chen, Mingshou Su, Chienyi Chen
Moreover, both the PAV (Q2) and AP (Q2) of the measured lightning current increase with an increase at a rotational speed of blades at same the polluted conditions. As aforementioned, the effect of salt contamination on the wind turbine blade is remarkably significant. Therefore, the article uses a FIS and a PNN to predict the salt contamination class for wind turbine blades that are subject to a lightning strike. These measurement techniques determine the degree of salt contamination on the blades of a WT. The lightning strike measurement system must be reliable.