The paper presents the statistical data of the significant parameters of lightning flash, collected by many researchers over many years around the world. The significant parameters of a lightning flash are: peak current, waveshape and velocity of the return stroke, the total flash charge and /spl int/I/sup 2/dt. Negative first strokes have traditionally been considered to produce the worst stress on the system insulation. The subsequent negative strokes have significantly lower peak current but shorter wavefronts. This may stress the system insulation more. The positive strokes have about the same median current value as the negative first strokes and longer fronts, thus producing less stress. However, their duration is longer than that of the negative strokes. Therefore, the system insulation may be damaged because of the lower volt-time characteristic for long-duration waves. The positive strokes may also cause more thermal damage because of their significantly higher charge and /spl int/I/sup 2/dt. The relationship between the return-stroke velocity and the current peak is a significant parameter in estimating lightning-induced voltages and also in estimating the peak current from the radiated electromagnetic fields of the lightning channel. For better accuracy, the current and the velocity should be measured simultaneously. Better methods to measure the stroke current need to be developed. Correlation coefficient between various lightning parameters is another important parameter which will affect the analysis significantly. Lightning characteristics should be classified according to geographical regions and seasons instead of assuming these characteristics to be globally uniform.

Parameters of lightning strokes: a review

A model of lightning-channel progression towards the Earth is given based on the latest knowledge on the physics of discharge in long air gaps. The physical assessment of the electric field is done with the charge simulation method, which is adopted to input into a computer program all parameters involved in the progression of the negative downward channels towards the Earth and those involved in the inception and propagation of upward positive channels from earthed structures. Starting from the geometrical configuration of the earthed object and taking into account the orographic conditions, the lateral distance may be evaluated as a function of the severity of the lightning stroke in terms of impulse charge and thus of current amplitude. Provided the statistical distribution of the currents is given, the model therefore allows the number of lightning strokes to an object to be estimated, yielding an assumed ground flash density. Reference is made to the critical radius concept acquired with laboratory tests with long front surges. A check of the model with field data relevant to free-standing structures is presented and a reasonable agreement is found. >

Lightning stroke simulation by means of the leader progression model. I. Description of the model and evaluation of exposure of free-standing structures

A simplified method for estimating lightning performance of transmission lines

A methodology is proposed and applied to determine the variation of soil resistivity and permittivity in the typical range of lightning current frequency components. The response of horizontal electrodes buried in high- and low-resistivity soils subjected to currents with lightning waveform patterns was measured and also simulated, taking this variation into account. The waves of the simulated and measured grounding potential rise are nearly the same but are quite different from the simulated waves considering the conventional assumption of constant values for soil resistivity and permittivity.

The Response of Grounding Electrodes to Lightning Currents: The Effect of Frequency-Dependent Soil Resistivity and Permittivity

The study was carried out to assess the determinants of household food security among rural households in Sekyere-Afram Plains District of Ghana Data were collected from 100 randomly selected households through the use of structured questionnaires Analytical techniques employed included descriptive statistics to analyze the characteristics of respondent households, and logistic regression model to examine the determinants of food security among the households surveyed Among the variables considered in the model, household size, farm size, off-farm income, credit access, and marital status were found to significantly influence household food security Consistent with a priori expectation, larger households were found to be food insecure compared with households with smaller sizes, ceteris paribus Also, consistent with findings from previous empirical studies, farm size, off-farm income and credit access were found to have significant positive effect on household food security The study, therefore, recommended improved access to credit for rural households and diversification of household economic activities to include off-farm income generating businesses to improve food security at the household level

Determinants of household food security in the sekyere-afram plains district of ghana

Lightning Parameters for Engineering Applications

CIGRE TB 549 (2013) is an update on previous CIGRE documents on the subject, published in Electra more than three decades ago Lightning parameters needed in different engineering applications are reviewed New experimental data, as well as the old data, are evaluated Additional lightning parameters, previously not considered by CIGRE, are included Possible geographical and seasonal variations in lightning parameters are examined Specific applications are considered and recommendations are made

CIGRE technical brochure on lightning parameters for engineering applications

Lightning Striking Characteristics to Very High Structures

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Lightning Parameters for Engineering Applications

CIGRE technical brochure on lightning parameters for engineering applications

Lightning Striking Characteristics to Very High Structures