A.J. Mazon

Best ANN structures for fault location in single-and double-circuit transmission lines

The great development in computing power has allowed the implementation of artificial neural networks (ANNs) in the most diverse fields of technology. This paper shows how diverse ANN structures can be applied to the processes of fault classification and fault location in overhead two-terminal transmission lines, with single and double circuit. The existence of a large group of valid ANN structures guarantees the applicability of ANNs in the fault classification and location processes. The selection of the best ANN structures for each process has been carried out by means of a software tool called SARENEUR.

New Method for Detecting Low Current Faults in Electrical Distribution Systems

In electrical distribution systems, low current faults may be caused by a high impedance fault or by the fault current limitation caused by the neutral to ground connection. In the former case, an indirect contact or insulation degradation give a high value of the fault impedance. In the latter, the neutral grounding may be either isolated or compensated. Nevertheless, these types of faults do not produce enough current so that the traditional overcurrent relays or fuses are not able to detect the fault. This paper presents a new methodology, based on the superposition of voltage signals of certain frequency, for the detection of low current single phase faults in radial distribution systems. The simulation analysis and laboratory tests carried out have proved the validity of the methodology for any type of grounding method.

High-temperature conductors: a solution in the uprating of overhead transmission lines

The legislation currently in force that affects the construction of overhead electricity transmission or distribution lines establishes an extensive number of conditioning factors as regards licences, public exposition of projects, rights regarding the presentation of allegations, etc. For that reason, the period that can elapse between the time the need for the installation of a new line is detected and its coming into service amply exceeds the time regarded as permissible by the utility. In upgrading the capacity of a line, the possible options include installing a larger conductor on existing structures, increasing the operating voltage, increasing operating temperature, etc. Also, uprating process using high-temperature conductors is another possible solution. This paper presents the most important results of the COALPRET research project, whose dual aim has been to carry out a general study of the characteristics of electrical conductors with high temperature performance and low sag, and apply these studies to the specific overhead transmission line.

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.

Phase Asymmetry: A New Parameter for Detecting Single-Phase Earth Faults in Compensated MV Networks

Traditionally, the detection of high-resistance earth faults has been a difficult task in compensated medium-voltage (MV) distribution networks, mainly due to its very low-current fault. To date, several techniques have been proposed to detect them: using current injection in the neutral, superposing voltage signals, varying the value of the arc suppression coil, etc. These techniques use different detection parameters, such as fault resistance to earth, line asymmetries, or partial residual neutral voltages. In this paper, phase asymmetry is defined as a new parameter that can be used, together with the aforementioned techniques, in order to improve the reliability and efficiency of the detection process in single-phase earth faults, especially for compensated networks. The use of this parameter has been validated through extensive simulations of resistive faults up to 15 kΩ , with the use of RESFAL software, which is based on Matlab/Simulink.