Estimation Of Lightning Performance Research Articles

Substation Lightning Performance Estimation Due to Strikes Into Connected Overhead Lines

The generalization of the probabilistic lightning limiting parameter (LLP) method for high-voltage substation lightning performance estimation due to the discharges into connected overhead lines (OHLs) is described. The method improvement is made only for the case of lightning strokes to the shield wire of OHL, causing back-flashover in front of the substation. The improved LLP method is illustrated at the insulation coordination study of the 400-kV line with long connecting cable with direct entry into the gas-insulated substation of the hydroelectric plant. The number of surge arrester sets and sensitivity analyses of the number of connected step-up transformers influence to the mean time between failures of the 400-kV transformer and equipment insulation are investigated.

Some aspects of overhead transmission lines lightning performance estimation in engineering practice

Summary The paper presents some aspects of overhead transmission lines (OHL) modeling for lightning overvoltages estimation in engineering practice. Different models of elements are compared, and sensitivity analysis is performed with the aim to investigate their influence to the OHL insulation stress due to lightning discharges. Elements are modeled according to international technical documents covering this field. Great influence of applied model of air flashover to the lightning current, sufficient to cause back flashover, is noticed. Calculation results obtained with different combinations of element models have been compared and large deviations are noticed. The models of elements for lightning overvoltages estimation should be carefully chosen to achieve reliable estimations. Constant resistance model of tower grounding and voltage-time curve model of air breakdown must be avoided in calculations, despite the fact that they are suggested in many technical documents dealing with lightning overvoltages at OHL. Copyright © 2015 John Wiley & Sons, Ltd.

An Analytical Method for Estimation of Lightning Performance of Transmission Lines Based on a Leader Progression Model

The leader progression model (LPM) is a tool for estimating the lightning performance of transmission lines. However, the large computation time remains a problem for the engineering application of this model. An analytical method is proposed in this paper to mitigate the aforementioned problem. First, nonlinear trajectory equations describing the movement of upward and downward leaders are obtained, starting with differential equations. Based on the trajectory equations, the average electric field between the upward and downward leader tips is represented with a comprehensive nonlinear equation. The final strike point is determined by solving the equations. Results show that the proposed method effectively mitigates the large computation time problem of traditional (numerical) LPM.

Medium voltage distribution systems lightning performance estimation

The estimation method for the statistical approach to the number of distribution system insulation failures caused by direct and indirect lightning strikes based on the lightning limiting parameter method is proposed. The optimal computation parameters like computation time-step, the number of strike locations along and perpendicular to the overhead line, and the number of simulations with different lightning current wave-shapes are determined after sensitivity analyses. The reduction of the overhead line flashover rate due to the direct lightning strikes caused by screening effect of the nearby objects is presented.

An improved method for HV substation lightning performance estimation

The paper presents a statistical approach to high-voltage substation lightning performance estimation. The method involves the monthly distribution of the lightning discharges to the lines, determined according to the line geometry and thunder activity, as well as the monthly probability distribution of the substation configurations. The mean time between failure of the power transformer insulations is estimated for a 400 kV/110 kV transformer substation. The paper provides the analysis of the results obtained for various dispositions, number and place of positioning the surge arresters, as well as the power transformer basic insulation level. The improved procedure of the lightning performance estimation can contribute to a more economical substation design.

High voltage substation equivalent circuits in the lightning performance estimation

The results of the systematic investigation of the influence of the high voltage substation equivalent circuit configuration in lightning performance estimation are presented. The effect of the overvoltage increase in the equivalent circuit with more than one capacitance connected, compared to the case of the single capacitance equivalent circuit, is explained and the procedure for a number of equivalent circuit elements reduction is presented. For five typical substation layouts, the complete sensitivity analysis of the equivalent circuit configuration is completed.

An expert system for high-voltage substations lightning performance estimation

A computer-based expert system approach to the detailed lightning performance evaluation of high-voltage overhead lines and substations is described. All parameters causing the computation result uncertainty are systematized and analyzed. The importance of the optimal equivalent circuit design is emphasized. For a 400 kV substation layout the sensitivity study of the parameters of the equivalent circuit is performed and an optimal circuit is evaluated. The lightning and the computing parameters are studied and the default values for practical application are suggested. Some of the software possibilities using a multilevel menu system are presented. A statistical approach to the substation lightning performance estimation based on the discharge point moving along the span of the connected overhead line in front of the analyzed substation entrance is described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Engineering method for high-voltage substations lightning performance estimation

A computer method for estimating the lightning performance of high-voltage substations has been developed and modified for simple engineering applications in the substation design. The main substation element representation and the equivalent circuit choice are suggested. The method is illustrated by the example of a 110 kV substation with a cable entrance. Both shielding failures and lightning strikes to the towers or the earth wires, causing back-flashovers on the incoming overhead lines, have been analysed and the best variant of the overvoltage protection suggested.

Some aspects of system modelling for the estimation of lightning performance of high voltage substations

The computation of lightning overvoltages in a gas-insulated substation is carried out for different overhead line equivalent circuits. Models of the back-flashover characteristics of the line insulation in front of the substation are analysed, and an investigation is made into the influence of the number of overhead line spans represented in the equivalent circuit. The results show that the inclusion of three overhead line spans in the equivalent circuit is sufficient for the estimation of the substation lightning performance. The influence of the instantaneous value of the power frequency voltage at the moment of lightning strike is also analysed. Direct strikes to a phase conductor and to the tower top with back flashover are simulated. For relatively small values of lightning current, the phase voltage at the moment of strike has a significant influence