Antonio F. Otero

Nodal frequency analysis of grounding systems considering the soil ionization effect

Soil ionization takes place when the current leaking into the earth is high enough to produce an electric field intensity greater than a critical value. This phenomenon lowers the ground impedance and it is similar to an apparent increase in the electrode dimensions. Soil ionization has a great influence on the performance of small grounding electrodes fed by currents of high magnitude (i.e., lightning waves). In this paper, a new way of including the nonlinear soil ionization in the grounding system analysis is proposed. The study of the grounding system is performed in the frequency domain by means of an equivalent electric circuit.

Low-frequency magnetic fields from electrical appliances and power lines

The relationship between magnetic fields and the health of people is increasingly being investigated. International organizations have proposed bylaws that put limits on the value of the generated magnetic field. In this work, we measure the magnetic field created by electrical appliances and high voltage lines and we analyze the degree of compliance with recent applicable European regulation. The simulation of the magnetic field generated by electrical lines through a simple model accurately predicts the measured values. The model is used to simulate the behavior of the lines under given conditions. In both cases, an FFT analysis of the magnetic field waveform was performed to study the frequency and amplitude of the possible induced currents.

Theoretical model to calculate steady-state and transient ampacity and temperature in buried cables

The temperature distribution and ampacity in a multilayered soil surrounding a system of three cables is calculated in the steady state in emergency situations. We present the mathematical model that solves the heat diffusion equation in cylindrical coordinates inside the cables and in Cartesian coordinates in the surrounding soil. The finite difference method is used to solve the equations. In order to reduce the number of points studied that are of no interest to the results, a variable step discretization is used. We present the development of the model and the effect of some of the parameters that influence the convergence and accuracy of the method. The application of the model in different configurations and situations is given in the second part of this work. The model is applicable to the study of buried cab in both the steady state and transient states for short circuit and overload situations.

Large-Scale Network Layout Optimization for Radial Distribution Networks by Parallel Computing

This paper presents an algorithm to simultaneously optimize the layout and conductor type in a radial distribution network. The optimization includes the investment cost and losses in the lines, with the maximum current constraints per conductor, maximum voltage drop in any node in the network, and tapering constraints. A branch-exchange algorithm is used for layout optimization; this generates intermediate points to avoid reaching local minimums, and conductor optimization is solved with a dynamic programming algorithm. There is also a variant for use in large-scale areas with several feeding points and a set of geographically distributed loads, which do not require a preassignation of the loads, allowing their connection to the point that offers lower overall cost. To achieve reasonable resolution times, a grid is built to utilize parallel computing.

Massive Jacobi power flow based on SIMD-processor

This paper presents an implementation of the Jacobi power flow algorithm to be run on a single instruction multiple data (SIMD) unit processor. The purpose is to be able to solve a large number of power flows in parallel as quickly as possible. This well-known algorithm was modified taking into account the characteristics of the SIMD architecture. The results show a significant speed-up of the algorithm compared to the time required to solve the algorithm in a conventional CPU, even when a more efficient sequential algorithm, such as the Newton-Raphson, is used. The accuracy of the performance has been validated with the results of the IEEE-118 standard network.

Large-Scale Network Layout Optimization for Radial Distribution Networks by Parallel Computing: Implementation and Numerical Results

This paper describes various practical aspects, in some detail, of inmplementiing an algorithm for the design of large-scale radial distribution networks. This algorithm is one which has been published previously, so this paper should be considered as the second part of that work. This algorithm simultaneously optimizes the line layout and type of conductor used. A branch-exchange algorithm for layout optimization, a dynamic programming algorithm for conductor optimization, and a decomposition algorithm enabling large-scale problem solving are all combined in this algorithm. To demonstrate the benefits of the proposed algorithm, numerical results have been provided from a reference network built for a low-voltage rural zone comprised of 1088 loads and 20 distribution substations. It can be verified that using the decomposition technique enables large-scale problem solving and produces results that are better than those techniques which come from a mere partition of the original problem into smaller parts.

Electrodynamics Simulation of Overhead Power Lines

Electrical overhead power lines are important installations today. They are the main part of electric transmission and distribution systems that are vital to developed societies. A key factor for proper operation is correct clearance between conducting parts and earthed parts. These separations can be altered by the movement in the conductors caused by various phenomena and this can lead to faults and subsequent supply outages. Furthermore, these situations can increase mechanical stress on conductors and cause breakages or structural faults in supports. In this paper, a multiphysic model is presented which includes three types of phenomena together: 1) electromagnetic; 2) thermal; and 3) mechanical. This model is used to study conductor movement and mechanical stress and takes the different types of stationary and transitory disturbances into consideration.

Magnetic-Field Evaluation in the Vicinity of High-Voltage Electric Systems

This paper presents a simulation model of the magnetic field generated by electric energy distribution and transport facilities. The aim of this paper is to assess the models compliance with current international regulations and recommendations. One of the principal advantages of this model is its relative simplicity, since it represents the facilitys elements by using a conductor network. This network is energized by injecting a system of currents that model the load state of the facility. The conductor network is subsequently analyzed as a conventional electrical circuit. This paper applies the model to the specific case of an outdoor substation and the results are later validated when compared with the magnetic-field measurements taken at the facility.

Parallelization of an optimal power flow with a multicore symmetric shared memory computer

The boom of multicore microprocessors seen in recent years has made it so any personal computer (PC) can be used as a small parallel computer. In this new environment a review of the algorithms and the tools used for the analysis of electrical systems is needed in order to take advantage of all the computing power available today on a PC. This paper presents the parallelization of an optimal power flow (OPF) which is solved with a predictor-corrector interior point method (PCIPM). OpenMP, a programming model for symmetric machines with shared memory, will be used for the parallelization.

EMF mitigation in the vicinity of a overhead power line

Recently the interest in a possible relation between electromagnetic fields created by some electric facilities, such as high voltage lines and substations, and health has been increasing. This has motivated many organizations to propose regulations to establish exposure values under electromagnetic fields. This implies the need to evaluate or measure the value of these fields. A way to accomplish this evaluation is by means of software tools. These tools can be developed taking into account different degrees of simplifications, depending on precision requirements. In some cases, the consideration of lines which conductors are perfectly horizontal and infinite can produce unacceptable results. On the other hand, solving exact models, which use Maxwells Equation, are too complex and provide unnecessary accuracies. This work is focused on showing some simulations of EMF generated by an overhead power line under different conditions and the presence of different passive conductor meshes is analyzed.