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This paper presents experimental results obtained at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida during the summers of 2002 and 2003. Currents induced by triggered and natural lightning events were measured at the terminations of a buried power cable, in the cable shield, and in the inner cable conductor. Measurements of the horizontal component of the magnetic field above the ground surface for both natural and triggered lightning are also presented. For distant natural lightning events, locations of ground strike points were determined using the U.S. National Lightning Detection Network (NLDN). Based on the theoretical developments presented in Part I of this paper [14], the field-to-buried cable coupling equations are solved in both the time domain and in the frequency domain. The obtained experimental results are then used to validate the numerical simulations provided by the relevant developed codes. Index Terms--LEMP-to-buried cables electromagnetic coupling, power cables, power system lightning effects, underground power distribution lines.

In this paper, we present a review of theoretical methods to compute lightning induced currents and voltages on buried cables. The evaluation of such induced disturbances requires the calculation of the electric field produced by lightning along the cable path. We show that the Cooray's simplified formula is capable of predicting accurately the horizontal electric field penetrating the ground, at distances as close as 100 m. Regarding the parameters of the buried cable, a comparison of several approximations of the ground impedance is presented. We show that the Pollaczek expression corresponds to the Sunde general expression, when the displacement current is neglected. The analysis shows also that all the proposed approximations provide very similar results for the considered range of frequencies (up to 30 MHz). Most of the approximate formulas neglect the contribution of the displacement current and, therefore, predict values for the ground impedance which tend to infinity at higher frequencies. This corresponds in the time domain to a singularity of the ground transient resistance at t = 0. By analogy to the Sunde approximation for the ground impedance of overhead lines, we propose a logarithmic approximation for the ground impedance of a buried cable. In addition, unlike most of the considered approximations, the proposed formula has an asymptotic behavior at high frequencies; therefore, the corresponding transient ground resistance in the time domain has no singularity at t = 0. It is also demonstrated that within the frequency range of interest, the wire impedance can be neglected, due to its small contribution to the overall longitudinal impedance of the line. The ground admittance, however, can play an important role at high frequencies (1 MHz or so) especially in the case of poor ground conductivity. The ground admittance needs to be taken into account in the calculation of lightning induced currents and voltages on buried cables. This is in contrast with the case of overhead lines in which its contribution is generally negligible, even in the MHz range. We also investigate the time-domain representation of field-to-transmission line coupling equations. The coupling model includes the effect of ground admittance which appears in terms of an additional convolution integral. An analytical expression for the ground transient resistance in the time domain is also proposed which is shown to be sufficiently accurate and nonsingular. Finally, we present a time domain solution of field-to-buried cable coupling equations using the point-centered finite difference time domain (FDTD) method, and a frequency domain solution using Green's functions. In our companion paper (Part II), we compare both solutions to experimental waveforms obtained using triggered lightning. Index Terms--Buried cables, electromagnetic coupling, lightning-induced voltages, modeling.

This paper presents a new approach to model a transmission tower for lightning performance studies. It consists of representing each part of the tower by equivalent vertical and/or horizontal transmission lines as required. While horizontal line parameters are obtained from standard line formulas, specific expressions are derived for the parameters of vertical lines. Moreover, mutual coupling between any two parallel vertical transmission lines is taken into account. Transient waveforms obtained using the proposed method are compared with experimental data obtained using a reduced-scale model and field experiments. The agreement between simulated results and experimental measurements is satisfactory. Index Terms--Vertical transmission lines, nonuniform transmission lines, transmission tower modeling, transient analysis, mutual impedance, reduced-scale model (RSM).

The calculation of voltages induced by indirect lightning on multiconductor lines has been the subject of several studies. The reported conclusions are not always in agreement with each other. In this paper, using a modeling procedure presented in a previous work, we study the shielding effect due to mutual coupling among the conductors of a three-phase line and between the ground wires and the line conductors. The results are compared with those published by other authors, and explanations of the disagreements are given. Additionally, a simplified method to evaluate lightning-induced voltages on a multiconductor line from the values obtained for the single conductor case is presented, and a simple formula which gives the magnitude reduction of the induced voltages due to the presence of other conductors is derived. It is shown that, for the examined case, the derived simple formula gives practically the same results as those obtained using the rigorous procedure. We have also compared results obtained using the simplified formula proposed by Rusck to evaluate the protective ratio of a ground wire with our results, and we have found that the values predicted by the Rusck formula are about 6% lower than ours.

Appropriate modelling of dynamic loads is of primary importance in voltage stability studies. The paper deals with the modelling of a load consisting of a static load plus an aggregate of induction motors. The behavior of three simplified models for such a load configuration is compared. The three models are A) a generic non-linear dynamic model of the first order as proposed by Karlsson and Hill, B) a static exponential load plus a dynamic first-order model for the induction motors, C) a static exponential load plus a dynamic third-order model for the induction motors. A power system with a longitudinal structure is chosen as the case-study. It is shown that for the same perturbation (tripping of one of two high-voltage parallel lines) the simulation results are quite different from each other and, in certain cases, only the third-order dynamic model correctly predicts the voltage collapse phenomena at the load bus. An interpretation of the different behavior of the various models is given.

Determination of the maximal voltages induced on the overhead power lines by nearby lightning stroke is a complex problem. The scope of this paper is to recognize the parameters that affect the maximal voltages and to present an equation for their estimation. This equation gives an opportunity to calculate the maximal voltage with the reasonable accuracy avoiding complex electromagnetic field calculus. It may be very useful in the estimation of flashover and outage rates due to the nearby strokes. Keywords: Nearby Lightning Stroke, Electromagnetic Field, Maximal Voltage.

The lightning-induced voltage waveform on an overhead wire having a branch is studied based on numerical calculations. The induced voltage is calculated by the method where the tangential component of the electric field to the overhead wire is looked upon as inducing sources. Accuracy of the calculated result is ensured with experimental results obtained by using a reduced-scale model. The induced voltage on an overhead wire turns out to be influenced by its branch, and is found to be dependent not only on the configuration of a branch line but also on the location of the lightning striking point. In most of the cases, the induced voltage increases when a branch is connected to an overhead wire.

Results of the research carried out at the Institute of Industrial Electrical Engineering of the University of Bologna on self-healing metallized polypropylene (MPP) capacitors are presented. Aim of the tests is to characterize the degradation of these capacitors when employed in automatic power factor correction systems or in power electronic applications with special reference to the disconnection of the 'sprayed ends' from the electrode-edges, one of the main reason for failure of MPP capacitors employed in the above systems. The research is carried out also in view of the definition of adequate type-test standards, presently not yet available for this kind of applications.

The two coupling models most frequently used in the power-lightning literature for the calculation of lightning-induced overvoltages, namely the model by Chowdhuri and Gross [1] and the model by Agrawal, Price and Gurbaxani [2], are compared and discussed. It is shown that the Chowdhuri-Gross model is incomplete: the source term due to the contribution of the magnetic induction is missing. It is investigated how much the lack of the source term affects the accuracy of the calculated overvoltages. Experimental tests of the two models using a short line illuminated by a NEMP simulator support the theoretical conclusion.