The paper focuses on the day-ahead operational planning of a grid-connected local energy community (LEC) consisting of an internal low-voltage network and several prosumers including generation units, battery storage systems, and local loads. In order to preserve, as much as possible, the confidentiality of the features of prosumers' equipment and the production and load forecasts, the problem is addressed by designing a specific distributed procedure based on the alternating direction method of multipliers (ADMM). The distributed procedure calculates the scheduling of the available energy resources to limit the balancing action of the external grid and allocates the internal network losses to the various power transactions. Results obtained for various case studies are compared with those obtained by a centralized optimization approach. The results confirm that, in the considered LEC framework, each of the prosumers achieves a reduction in costs or increases revenues in case it participates to the LEC with respect to the case in which it can only transact with an external energy provider.

An accurate evaluation of the lightning performance of overhead power distribution lines, that is, the evaluation of the expected number of annual flashovers, can be obtained by the application of the Monte Carlo method. In order to reduce the computational effort, a simplified waveform of the channel base current is generally assumed, for example, a linearly rising current with flat top. This paper proposes a Monte Carlo approach able to take into account the typical functions adopted to represent the waveform of the lightning current at the channel base (i.e., the Heidler function and the CIGRÉ function). Moreover, this paper analyzes the effects of different current waveforms on the lightning performance of distribution lines for both direct and indirect strokes.

In medium-voltage distribution lines, lightning outages associated with indirect strokes are less frequent when surge arresters are installed at close intervals. In this case, the lightning performance is mainly determined by the line response due to direct strikes, usually assessed disregarding the effect of the lightning electromagnetic pulse (LEMP). This paper examines the influence of such an electromagnetic effect on the voltages across the line insulators caused by direct lightnings. The presence of both surge arresters and a shield wire is considered. By means of adequate modeling and numerical calculations, we show that the flashover rate due to the direct strikes is increased by the LEMP. The obtained results indicate that in the statistical assessment of the direct lightning performance of lines equipped by surge arresters and shield wires, the LEMP effect is not negligible and its accurate evaluation is hence required.

This paper proposes the application of a recursive stratified sampling technique for improving the assessment of the lightning performance of power distribution lines through the application of the Monte Carlo method. The accuracy of the results is expressed by means of the confidence interval of the estimated annual number of expected overvoltages. The paper shows the results for a single overhead line, with and without surge arresters, and the case of a feeder with laterals. The adoption of the stratified sampling techniques allows for a computational time reduction up to more than 75% with respect to a standard Monte Carlo procedure. The conceived calculation procedure is applicable to any type of network, regardless of the presence of non-linear devices and avoiding the application of any heuristic rule.

Buildings nearby urban overhead power lines are expected to reduce the number of direct strikes to the line conductors and also to attenuate the lightning electromagnetic pulse (LEMP) radiated by indirect lightning strokes. The statistical method described in IEEE Std. 1410 for the lightning performance assessment, as the other methods available in the literature, includes only the former effect. In order to take into account also the latter effect, in this paper the LEMP attenuation due to the buildings is represented by means of specific weighting functions applied to the LEMP analytical expressions valid for open terrain. For both the cases of ideal and lossy ground, the parameters of the weighting functions are identified through the least square minimization of the differences with the results provided by a finite element method model that is assumed as reference for the configurations analyzed. The weighting functions can be used for lightning return stroke current waveform and distances between the line and the stroke location different from those used for their identification with reasonable accuracy. Finally, the paper compares the lightning performances of a power line evaluated with and without the presence of nearby buildings.