Ernesto Perez

Calculation of Lightning-Induced Voltages on Overhead Distribution Lines Including Insulation Breakdown

This paper investigates the influence of considering actual insulation volt-time curves both in the calculation of lightning-induced voltages and in the estimation of the number of flashovers an overhead wire may experience per year due to nearby lightning strokes. The flashover mechanism is modeled according with the integration method, which is used as a reference for comparisons with the simplified 1.5 CFO flashover criterion traditionally used in the estimation of the lightning performance of overhead distribution lines. Sensitivity analysis show the dependence of flashovers on the shape and front time of the assumed channel-base current. The obtained results suggest that the simplified 1.5 CFO flashover criterion is likely to underestimate the number of flashovers an overhead line may experience per year due to nearby lightning strokes. This result is confirmed by statistical analyses considering a Monte Carlo-based approach. It is also shown that more realistic flashover rate estimates can be obtained in the statistical analysis of lightning-induced voltages provided a reduced threshold level (1.2 CFO in the particular case evaluated in this paper) is considered instead of the 1.5 CFO level traditionally used in this type of study.

Optimizing the Surge Arresters Location for Improving Lightning Induced Voltage Performance of Distribution Network

This paper will deal with improvement of lightning induced voltage performance of distribution network by optimizing the surge arrester location on the distribution network. The optimization of the location is made by using a novel formulation based on genetic algorithms. Here is described the implementation of this methodology by using sophisticate software which has been used for lightning induced voltage analysis. It is also described the capabilities and the limitations of this novel formulation. The performance of the network is evaluated by means of a probability distribution curve obtained from a statistical evaluation of the lightning induced voltages on the distribution line.

Contribution to Lightning Parameters Study Based on Some American Tropical Regions Observations

This paper presents a recent characterization review of three cloud-to-ground lightning parameters [lightning peak current, ground flash density, and keraunic level (KL)] used in engineering applications based on available data from studies conducted in some tropical countries of Central and South America (Brazil, Colombia, Costa Rica, and Venezuela), considering seasonal and spatial variation aspects. There are some differences between the behaviors of the analyzed parameters in tropical areas in comparison with those published in the literature for temperate ones. The most significant conclusion is that historical data suggest that the highest ground flash density are located between latitude of 8° and 10° north. This value is much higher than the highest values reported for countries located in temperate regions. It is seen from the KL analysis that this parameter varies depending on the latitude with values up to 200 thunderstorm days (TDs).

Sensitivity analysis of induced voltages on distribution lines

This paper presents a sensitivity analysis of induced voltages on overhead distribution lines due to some lightning and line configuration parameters variations. The sensitivity analysis was made initially varying just one parameter individually and then was varied whole parameters at the same time analyzed by means of nonlinear regression models. This analysis shows the parameters that have more influence on the induced voltages. It was also obtained an approximate equation to calculate the maximum induced voltage along the line. The obtained equation was also compared with other approximate equations such as Rusck and Jankov.

Electromagnetic Field Due to Lightning Striking on Top of a Cone-Shaped Mountain Using the FDTD

This paper presents the calculation of electric and magnetic fields produced by lightning striking over different configurations of nonflat lossy ground. The computation is performed using finite-difference time domain (FDTD) methods in two-dimensional (2-D) with cylindrical coordinate systems and 3-D with Cartesian coordinates. The FDTD method is validated with several previous approximations for lightning electric field computation, such as Uman equations and simulation of lightning striking on the top of a tower. In this study, it is found that lightning striking on the top of a cone-shaped mountain may produce several variations on an electromagnetic field. An enhancement of the perpendicular and parallel to ground electric field components was observed for a cone-shaped configuration only. For configurations that include flat planes, wave reflections due to the transition between the cone-shaped and flat plane were observed.

Thunderstorm warning alarms methodology using electric field mills and lightning location networks in mountainous regions

This paper presents a methodology for thunderstorm warning alarming using electric field measurements and lightning location data under mountainous conditions in Medellín - Colombia. The methodology is used to set warning criteria for preventing human and sensitive systems risks and damages.

Statistical evaluation of transferred voltages through transformers due to lightning induced overvoltages

This paper deals with the evaluation of the transferred voltages to the transformer low voltage side, due to lightning induced voltages on overhead distribution lines. The induced voltages calculations, taking into account the presence of electrical devices connected to the electric networks like transformers and surge arresters, is done by its implementation into the ATP/EMTP program. The frequency of certain voltage to be exceeded is evaluated using the Monte Carlo method in order to generate multiple simulation parameters randomly. As a result, it is shown that in some cases the protection devices used to attenuate the overvoltages are insufficient from the users point of view.

Lightning induced voltages on an distribution network over an inclined terrain

This paper presents the induced voltages produced by a lightning that hits the top of a mountain over a line placed parallel to the inclined surface, compared with the result found when the line is placed over a flat terrain. The electromagnetic fields produced by the lightning channel are calculated by means of the Finite Difference Time Domain Method (FDTD) and the lightning induced voltages are calculated with the Agrawal approach. This work shows that exists important differences in the lightning induced voltages when we take into account the topography.

Methodology for thunderstorm tracking using lightning location systems data in Colombia

This paper presents a methodology for tracking thunderstorm cells using Colombian Lightning Location Systems. It is evaluated two regions in Colombia with different orographic conditions and is observed the possible dependency which may have the orography.

Implementation of an analytical formulation for LEMP to assess the lightning performance of a distribution line

This paper presents the implementation of an analytical formulation to calculate the lightning electromagnetic pulse (LEMP) assuming a current wave-shape linearly rising with flat top and a transmission Line (TL) return-stroke model. It also describes the development of the expressions for the image dipoles required to calculate the vertical electric field, the azimuthal magnetic field and, specially, the horizontal electric field. The expressions to calculate the contribution of source dipoles were detailed in a previous publication by other authors. The complete formulation is used to calculate electromagnetic fields and lightning-induced voltages on a typical overhead distribution line. The results were compared with traditional formulas to calculate the LEMP (such as Rubinstein’s) and to calculate induced voltages (such as Rusck’s) showing errors below 1%. If a more complex wave shape was used (such as Heidler’s), errors below 5% were found. Additionally, the formula was employed to calculate the flashover rate of a distribution line above a ground with infinite and finite conductivity. Errors less than 5% were found compared to the results obtained in the IEEE 1410 Standard. On the other hand, the computation time required to the assessment of an overhead line indirect lightning performance is reduced by half when the analytical formula is used.