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Current from nearby rocket-triggered lightning that flowed through the soil and into an unenergized test power distribution line was studied based on experimental data acquired in 2003 at the International Center for Lightning Research and Testing in Florida. The 15-pole, three-phase fine was 812 m long, was equipped with four arrester stations, at poles 2, 6, 10, and 14, and was terminated in its characteristic impedance at poles 1 and 15. The neutral conductor of the fine was grounded at each arrester station and at both line terminations. Measurements suggest that a significant fraction of the lightning current injected into the earth a distance of 11 m from pole 15 entered the line through the grounding system of pole 15. The peak value of the microsecond-scale return stroke current entering the line through the pole 15 fine ground was 7% of the peak value of the return stroke current injected into the earth. The peak value of the millisecond-scale triggered lightning initial stage current and the millisecond-scale return-stroke and initial-stage charge transfer to the line through the pole 15 line ground was between 12% and 19% of the lightning peak current/charge transfer, indicating that the percentage values for the injected peak currents are dependent on the current waveshape: for microsecond-scale return stroke currents, possibly due to electromagnetic coupling effects, a smaller fraction of the current peak enters the line compared to millisecond-scale initial stage currents. In the latter case, any influence of electromagnetic coupling to the line on ground currents is expected to be negligible. Index Terms--Current measurements, electromagnetic coupling, grounding electrodes, grounds, lightning protection, power distribution lines, rocket-triggered lightning.

This paper deals with the calculation of lightning-induced overvoltages on medium-voltage (MV) and low-voltage (LV) distribution networks taking into account the presence of MV-LV distribution transformers and, in particular, the surge transfer through them. The influence of the high-frequency model adopted for the representation of the power transformer on the calculation results is analyzed, with regards to two different models, both identified and validated by means of laboratory measurements: namely, a simple [pi] of capacitances, and the more complex one introduced by Morched, Marti, and Ottevangers in 1993. Accurate simulation results provide information on the adequacy of both models for the calculations of interest. Additional results, useful to evaluate the expected level of power quality and the benefits achievable by a proper installation of protection devices, are presented making reference to a realistic and complex configuration of an overhead distribution system. Index Terms--Electromagnetic transients, high-frequency transformer models, lightning-induced overvoltages, medium-voltage (MV) and low-voltage (LV) insulation coordination, power quality (PQ).

Engineering return stroke models can be categorized either as current generation (traveling current source type) models or current propagation (transmission line type) models. The current generation models are described among other parameters by a corona current distributed along the channel. Recent studies show that there is equivalence between the models of current generation and current propagation types. Due to this equivalence, any engineering return stroke model of current propagation type can be described in terms of an equivalent corona current per unit channel length. The measurements conducted within 10-500 m from triggered lightning flashes show that the electric field of subsequent return strokes at these distances flattens within 15/[micro]s or so. In this paper, the constraints imposed by this feature on the temporal and spatial variation of the equivalent corona current are investigated. The results show that in order for the close fields to flatten within 15 [micro]s or so, the equivalent corona current, should be bipolar and the corona current wave shape at late times should be identical to that of the longitudinal current time derivative. This is in contrast to most of the engineering models of current generation type, in which the corona current is assumed to be unipolar. Index Terms--Equivalent corona current, lightning electric field, return stroke models.

This paper presents an effective numeric method to compute Pollaczek integral. This integral is widely used in transmission-line theory when computing the mutual impedance between an overhead conductor and another overhead or underground conductor and the earth-return impedance of an underground cable. At first, we present mutual expressions proposed by Pollaczek and underline the numerical complexities that often lead to the adoption of alternative simplified methods. Then a brief review of the so called 'quasi-Monte Carlo' integration method along with its advantages is given. Such an approach is then applied to compute numerically Pollaczek expressions. Comparison between our numerical procedure and an algorithm that has already been published proves both the procedure accuracy, one of its main advantages along with its ease of implementation, and its relatively low time consumption, independent of the input parameters. Finally, as an application example, quasi-Monte Carlo method is used to assess the adequacy, for several study cases, of the simplified formula by Lucca, which is a widely used approximate expression of interest. Index Terms--Coupled transmission lines, mutual coupling, power cables, power system transients.

The paper presents a fault location procedure for distribution networks based on the wavelet analysis of the fault-generated traveling waves. In particular, the proposed procedure implements the continuous wavelet analysis applied to the voltage waveforms recorded during the fault in correspondence of a network bus. In order to improve the wavelet analysis, an algorithm is proposed to build specific mother wavelets inferred from the fault-originated transient waveforms. The performance of the proposed algorithm are analyzed for the case of the IEEE 34-bus test distribution network and compared with those achieved by using the more traditional Morlet mother wavelet. Index Terms--Continuous wavelet transform, distribution network, EMTP simulations, fault location, mother wavelet, power quality.