Esther Torres

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.

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.

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.

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.

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.

Electric Arc in Low-Voltage Circuit Breakers: Experiments and Simulation

The aim of this paper is to present a further approach for analyzing the air electric arc in low-voltage circuit breakers (LVCBs). In order to achieve that, a new simulation model and experimental tests have been carried out. The simulation model has been designed using ANSYS CFX, a finite-volume method commercial software. This model has been defined as a 3-D geometry, with a high density structured hexahedral mesh, P1 radiation model and hot air characteristics for thermal plasma properties and transport coefficients. The model is applied to simulate the behavior of an LVCB for 50, 100, and 200 A with different numbers of splitter plates in the arc chamber and different locations for the arc ignition. As result, arc elongation and arc voltage increase have been observed when increasing the splitter plates number. Also faster arcs for higher ignition zones and greater expansion and diffusion for higher input currents have been obtained. These simulation results have been verified and validated. The verification process has been accomplished calculating the numerical errors, by means of the grid convergence index and Courant-Friedrichs-Lewis number. Thus, the most accurate mesh densities, time steps, and radiation models have been selected. Finally, the validation process has been achieved performing real experimental tests in the laboratory, proving that the results of the simulation model are close to real scenarios.

Gap-type conductors: influence of high temperature in the compression clamp systems

The unstoppable rise in electricity demand is causing the saturation of the power transmission network to such an extent that supply problems are arising in some areas due to overheated conductors sagging above security distance limits. An approach to solve this problem is the replacement of actual conductors by new conductors with high temperature and low sag characteristics. This type of conductors is able to transmit more power than traditional ACSR conductors, as they can work at higher temperatures while keeping their sag under actual security margins. However, the higher temperature in the conductors can affect the correct performance of the traditional clamps. To develop an analysis on this subject software tools have been used, consisting on CAD programs for the design and modeling of the clamps and FEM programs for the simulation of the models. This work shows the results of the study describing the characteristics of the simulation.

Analysis of spatial discretization for electric arc simulations

The main focus of this work is to give an overview of the mathematical errors introduced by the spatial discretization in case of plasma simulations. Two standard models for the electric arc simulation have been used; a Free Burning Arc (FBA) and a Switching Arc (SA). Three radiation models have been studied for each arc model in order to verify how this factor influences the overall computation stability. For each of the models a variation of the mesh density has been performed. The results are analyzed and discussed by using standard methods developed for the quantification of the numerical error that appears in a simulation model due to the spatial discretization. All the simulations have been performed with the commercial solver Ansys CFX.

Application of parameter estimation methods to the assessment of DFIG;s currents

Proliferation of nonlinear loads and development of renewable energy resources introduces new challenges in power quality monitoring due to the increased level of harmonic distortion of voltage and current signals. In this paper, the quality of harmonic distortion of currents recorded on a laboratory Double Fed Induction Generator drive is investigated. An efficient nonlinear estimation method is applied to evaluate the effects of interharmonic distortion in the estimation process. The results obtained are compared with those provided by the application of the Fast Fourier Technique (FFT).