Real-time monitoring allows the determination of the line state and the calculation of the actual rating value. The real-time monitoring systems measure sag, conductor tension, conductor temperature, or weather-related magnitudes. In this paper, a new ampacity monitoring system for overhead lines, based on the conductor tension, the ambient temperature, the solar radiation, and the current intensity is presented. The measurements are transmitted via general-packet radio service to a control center where a software program calculates the ampacity value. The system takes the creep deformation experienced by the conductors during their lifetime into account and calibrates the tension-temperature reference and the maximum-allowable temperature in order to obtain the ampacity. The system includes hardware implementation and remote-control software.

The design of protection systems associated with medium and low voltage networks has traditionally been based on the assumption of unidirectional power flows, making the use of time coordinated overcurrent relays an efficient and reliable way of protecting against network faults. The changes that these systems have undergone over the recent decades regarding distributed generation, along with the fact that many of these sources can be connected to form independent microgrids, have challenged this perspective. A number of alternative solutions have recently appeared in technical literature. Therefore, this paper aims to provide a comprehensive overview of the existing proposals for protection design in microgrids. Apart from describing the most relevant options presented to date and classifying them in specific groups, a comparative analysis is performed in which the most important benefits and drawbacks of each approach are presented. Finally, some conclusions and practical recommendations are derived from the analyzed references.

Weak power grids with DG penetration show poor power quality, protection issues and frequency deviations under severe disturbances, especially in isolated networks. This paper explores the impact of wind power in weak isolated power systems. A small size island power system has been modeled and the impact of wind power on system stability has been studied. Two main aspects have been covered: the impact on frequency stability and on transient stability, as well as fault-ride through capability of the wind turbines.

Predictions of the ampacity of overhead lines can be framed in a general context that aims to make electric grids highly efficient and reliable. In this paper, a methodology is presented that provides ampacity forecasts, which are valid for both the very short term, such as a few minutes or hours, and longer terms, up to 24 hours ahead. The former can be useful for grid operations, while the latter may be valuable in electricity markets. A time series methodology and mesoscale weather forecasts have been combined in machine learning algorithms for producing reliable ampacity forecasts for a span located in complex terrain. In a prior step, the developed algorithms made point forecasts, but finally, a computationally inexpensive algorithm produces probabilistic forecasts. These probabilistic forecasts are nonparametric, as they are not based on predefined probability distributions, and they demonstrate how a low risk in overhead lines is closely related to the reliability of ampacity forecasts.