P. Eguia

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.

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.

Dynamic simulation of a SSSC for power flow control during transmission network contingencies

Power flow control in transmission networks requires new approaches to deal with the uncertainties in the power flow patterns caused by the massive integration of renewable energy generators and the difficulties for constructing new transmission corridors, due to environmental restrictions and social opposition. One solution explored nowadays by utilities is the installation of SSSCs in congested transmission corridors to alleviate overloads during network contingencies, delaying investments in new transmission lines. This paper deals with the modeling of a SSSC for dynamic simulation and its application to alleviate overloads during network contingencies. A reduced model of the Spanish Transmission Network has been used in the dynamic simulations and the results confirm the validity of the SSSC to alleviate network overloads. The studies have been carried out using the simulation software PSS/E and the model of the SSSC has been programmed in Python, instead of the traditional approach based on Fortran.

Fault location system on double circuit two-terminal transmission lines based on ANNs

This paper presents a new approach to fault location in double-circuit two-terminal overhead transmission lines, using artificial neural networks (ANNs). The method presented enables the distance to be determined at which the fault occurs in a double-circuit two-terminal transmission line using the fundamental components of 50/60 Hz of the fault and pre-fault voltage and current magnitudes, measured in each phase of the reference end. The accuracy of the method has been checked using properly validated fault simulation software developed with MATLAB. This software allows generation of faults in any location of the line, to obtain the fault and pre-fault voltage and current values. With this value, the fault can be classified and the corresponding ANN activated in order to determine the fault distance.

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.

Islanding detection of synchronous distributed generators

This paper analyses the performance of local passive islanding detection methods for synchronous distributed generators, under different grid and load scenarios. These methods monitor electrical parameters at the interconnection point of a distributed generator and detect island situation whenever these parameters change correspondingly. Lately, islanding detection research has been focused on inverter based systems. But synchronous generators still pose a challenge for study. With this aim, a low voltage distribution network with embedded synchronous generators has been modelled. The performance of frequency and rate-of-change-of-frequency relays have been evaluated, analysing the influence of power mismatch and generator characteristics on the islanding and also avoid false operation.

Development of a methodology for transmission planning in deregulated electric sectors

The deregulation of the electric sector involves a deep change in its structure and operation. With respect to the development of the transmission network, the deregulation introduces more complexity because the free establishment of new generators increases the uncertainty that the planner must face. Moreover, network users will demand more transparency since planning projects can affect their participation in the electric market. This paper presents a methodology to develop the transmission network in deregulated electric systems, providing indications about the creation of base cases for the identification of new investments and the planning criteria to apply for the technical and economical evaluation of the various alternatives for network expansion.

Fault location in combined transmission lines using PMUs for recloser control

In general, there is a growing trend towards the installation of underground cable to replace overhead lines, completely or in certain sections, resulting in combined transmission lines. The present protection practice for faults in the underground section of these lines is based on protecting the cable with a line differential relay, which blocks the reclose order issued by the protections installed in each line end. This paper discusses the replacement of the line differential relay by a fault location algorithm added to the line end relays. The algorithm is based on the measurement of synchrophasors at each end of the line to allow or cancel the reclose order, depending on the faulted section. The new algorithm has been validated by extensive simulations using Matlab and by laboratory tests.

Influence of resonant coil tuning in the fault current magnitude

This paper analyses the behavior of the resonant grounding method in MV electrical distribution systems, and its influence in the fault current magnitude. It is necessary to take into account several aspects as the specific topology of the system. Thus, a comparative analysis of different systems with different characteristics is presented. The fault current magnitude is studied for different resonant coil tuning values, and the obtained results are compared with the solid grounding method. Finally, using a real MV network, the effect of resonant coil tuning is analysed.