I. Albizu

Methods for increasing the rating of overhead lines

At the present time, there is great pressure to increase the power flow in existing right of ways using existing infrastructure as far as possible. In this paper, the diverse options for increasing the rating of overhead lines are presented and analyzed. By means of a comparative study, their advantages and drawbacks are highlighted. In addition, the factors that determine the choice of the method are analyzed.

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.

Flexible Strain-Tension Calculation Method for Gap-Type Overhead Conductors

Commercially available sag-tension programs give good results for most practical applications. However, they have some limitations concerning gap-type conductors. A separate aluminum and core creep calculation is needed due to the special structure of gap-type conductors. For the same reason, different core and aluminum lengths have to be considered. In order to take the creep during the installation process into account, flexibility for the consideration of several stages is needed. A method that considers all of these characteristics has been developed and implemented in a comprehensive, versatile, and flexible sag-tension software tool, called Strain Tension in Overhead Conductors. The program has been designed for the analysis of gap-type conductors. However, the method is a general method that can be used for any type of conductor, especially when flexibility for the calculation of several creep conditions is needed.

Techniques for Online Diagnosis of Stator Shorted Turns in Induction Motors

In low voltage induction motors, the first indication of a stator fault is the appearance of an interturn short circuit. For this reason, several attempts to diagnose reliably these short circuits have been made. Although considerable research has been carried out, the diagnosis of interturn short circuits is not a mature technique yet. This article presents and analyzes the online interturn short circuit diagnostic techniques developed so far for line-connected induction motors. By means of a comparative study, their advantages and drawbacks are highlighted.

On-line stator winding fault diagnosis in induction generators for renewable generation

Renewable generation systems are increasing its presence in electrical power systems. For this reason, it is more important than ever to count with reliable and secure generation systems. In this way, the use of on-line diagnostic techniques in the maintenance schemes can be useful. This paper is about on-line condition monitoring in induction generators for small hydro stations and wind farms. In particular, stator winding fault diagnosis is analyzed. Currently, there are diagnostic techniques that are used in induction motors, but they could be used in generators as well. This paper analyzes the induction generator characteristics and describes the appropriate diagnostic techniques. These techniques depend on the machine voltage. As most of the induction generators are low voltage machines, the diagnosis of stator winding faults will be based on the detection of inter-turn short circuits. Most of the inter-turn short circuit diagnostic techniques are noninvasive as they are based on voltage and line current monitoring.

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.

Application of superimposed voltage in the detection of faults in resonant distribution systems

As a high percentage of the length of overhead lines corresponds to distribution lines, there is a strong probability that faults in overhead distribution lines will occur. When a fault occurs in a resonant grounded system, the short circuit current is below the threshold of the protection system. This means that the sensitivity of the protection system is not good enough to detect the fault and as a consequence the fault cannot be isolated. In this situation, the contact of a high voltage conductor with ground is a hazard to people. This is especially dangerous in the distribution lines as they are close to final customers. For this reason, it is fundamental to have at the power systems disposal devices that permit the detection of that type of faults. This work presents the definition of a new methodology for the detection of fault currents in resonant grounded systems based on superimposed voltage.