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Abstract:As renewable distributed energy resources (DERs) penetrate the power grid at an accelerating speed, it is essential for operators to have accurate solar photovoltaic (PV) energy forecasting for efficient operations and planning. Generally, observed weather data are applied in the solar PV generation forecasting model while in practice the energy forecasting is based on forecasted weather data. In this paper, a study on the uncertainty in weather forecasting for the most commonly used weather variables is presented. The forecasted weather data for six days ahead is compared with the observed data and the results of analysis are quantified by statistical metrics. In addition, the most influential weather predictors in energy forecasting model are selected. The performance of historical and observed weather data errors is assessed using a solar PV generation forecasting model. Finally, a sensitivity test is performed to identify the influential weather variables whose accurate values can significantly improve the results of energy forecasting.

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Non-pressurised air is extensively used as basic insulation medium in high-voltage equipment. Unfortunately, an inherent property of air-insulated design is that the system tends to become physically large. On the other hand, the application of dielectric barriers can increase the breakdown voltage and therefore decrease the size of the equipment. In this study, the impact of dielectric barriers on breakdown voltage enhancement is investigated under both direct current (dc) and alternating current (ac) applied voltages. For this purpose, three kinds of dielectric barriers in two different high-voltage electrode structures are investigated. In the first structure, several experiments are carried out with four different electrode arrangements, keeping the inter-electrode gap constant while varying the position of the dielectric barrier between the electrodes. In the second structure, the inter-electrode gap is varied while the high-voltage electrode is covered with dielectric materials. The influences of different parameters such as inter-electrode spacing, electric field non-uniformity factor, and dielectric materials on the breakdown voltage are investigated for applied 50 Hz ac and dc voltages. In addition, a simulation model to approximately calculate the breakdown voltage is proposed and validated with the experimental results.