E. Fernandez

Simulation by MATLAB/Simulink of active filters for reducing THD created by industrial systems

Nowadays, power electronics are widely used in industry for supplying loads with amplitude and frequency controlled voltage. These systems comprise mainly rectifiers and inverters, which, as non-linear loads, produce currents with high harmonic content. In order to fulfill the legislation concerning voltage harmonic distortion it is necessary to put in place corrective actions. Among these corrective actions active filters are one of the most effective. For the design of these filters simulation has been proved to be a very useful tool. In this paper, the simulation by MATLAB/Simulink of an active filter for the reduction of the harmonic distortion is analysed. Two examples are presented: a steel plant and an underground traction system.

Tension and Ampacity Monitoring System for Overhead Lines

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.

Overhead conductor monitoring system for the evaluation of the low sag behavior

The paper describes a monitoring system for the evaluation of the low sag behavior of the overhead conductors in operating lines. The monitoring system measures the conductor tension and temperature and it also measures the wind speed to evaluate the load in the conductor due to wind. This system includes a methodology for the analysis of the measured data and the comparison of these data with the theoretical values obtained by mechanical calculation.

Hardware and software architecture for overhead line rating monitoring

Real time monitoring in both electrical transmission and distribution lines is an interesting option for knowing the electrical load level of these lines. The information about the load level allows alleviating the overloaded lines if the power can be transferred to other lines. 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 GPRS to a control center where a software program calculates the ampacity value. The system takes into account the creep deformation experienced by the conductors during their lifetime and calibrates the tension-temperature reference and the maximum allowable temperature in order to obtain the ampacity.

Dynamic line rating forecasting based on numerical weather prediction

This paper describes the line rating forecasting techniques based on NWP models. Taking the wind power forecasting as a base for the overhead line rating forecasting, the paper identifies the differences between the wind power forecasting and the overhead line rating forecasting. Recent experiences about overhead line rating forecasting are also described. As a result, the requirements for the overhead line rating forecasting are defined. Finally, a pilot project of overhead line rating forecasting is presented and the results are discussed.

Impact of wind power in isolated power systems

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.

Monitoring the tension and the temperature in an overhead line

The paper describes a monitoring system for the evaluation of the low sag behavior of the overhead conductors. The monitoring system measures the conductor tension and temperature. This system includes a methodology for the analysis of the measured data, and obtains the theoretical tension-temperature curve that estimates the conductors behavior.

System for ampacity monitoring and low sag overhead conductor evaluation

Among the different alternatives to achieve the uprating and better use of existing overhead power lines are the use of high temperature low sag conductors and the use of real time monitoring systems for knowing the ampacity of the lines. So far, the uprating of a power line through both alternatives have been considered separately. However, it is possible to combine both solutions and obtain greater benefit in terms of achievable uprating, and a better control of the reliability of the conductor. This paper presents a system for monitoring the ampacity and for the evaluation of the low sag behavior of the overhead power lines. This system allows knowing the power flow of the lines in order to optimize their use and evaluating the conductor monitored in order to validate their behavior in operating condition.

Thermal analysis of medium voltage fuses using the finite element method

The design of the protection system becomes fundamental to guarantee the adequate operation of the electric system under fault conditions, as it makes possible to isolate only faulted devices without affecting to the other ones. Electric fuses are protection devices broadly used in distribution networks, being designed to interrupt the current by means of the melting of one of their components when excessive currents flow through it during a period of time. In this paper the thermal analysis of a medium voltage fuse by means of the finite element method is presented. The fuse model has been designed and simulated under different conditions of ambient temperature with Cosmos software tool. The results obtained from the simulation are compared with those obtained from real tests.

Factors that affect the sag-tension model of an overhead conductor

The sag-tension model of an overhead conductor in operation is analyzed. A monitoring system measures the conductor tension and temperature. With the measured data obtained in a pilot installation and considering the theoretical values obtained by calculation, the factors that affect the sag-tension model of an overhead conductor are analyzed.