Araitz Iturregi

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.

DC fault detection in VSC-based HVDC grids used for the integration of renewable energies

Considering the relevance that HVDC systems are expected to have in the future of power networks, this paper aims to provide a wide overview of the protection against DC faults. In particular, the detection and location techniques that have been proposed to date are analyzed, focusing on the approaches that are set to be applied in modern HVDC networks, which comprise VSC-HVDC and MTDC systems. Although these systems present a series of remarkable advantages compared to the traditional LCC-HVDC systems, they require a fast detection and tripping of the fault, which is an important challenge in the design of the protection system.

A Solid-State Fault Current Limiting Device for VSC-HVDC Systems

Abstract Faults in the DC circuit constitute one of the main limitations of voltage source converter VSC-HVDC systems, as the high fault currents can damage seriously the converters. In this article, a new design for a fault current limiter (FCL) is proposed, which is capable of limiting the fault current as well as interrupting it, isolating the DC grid. The operation of the proposed FCL is analysed and verified with the most usual faults that can occur in overhead lines.

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.

Work in progress: Project-based learning for electrical engineering

This paper presents ProElec project, which links all the subjects of the electrical engineering field through the academic itinerary of Civil Engineering and Mining and Energy Engineering students at the University of the Basque Country UPV/EHU. Based on Project-Based Learning (PBL), ProElec aims to lead students from 2nd year up to the Bachelor thesis in a dynamic learning process. In order to build the necessary specific and transversal competencies, students will have to design an electrical installation, from the technical, economical and legislative point of view along different subjects. This way, students build their own knowledge autonomously emphasizing their leading role in the teaching-learning process. The aim of the paper is to describe the background, framework, implementation and objective tasks of ProElec project. As preliminary results surveys from students are presented, where it can be observed that the experience has been so far positive.

Evaluation of dynamic response in isolated power grids: Terceira island

Terceira island has a great potential for geothermal energy, which can contribute to increase the penetration of renewable energies in the generation mix. But as a small size island grid, several technical issues can appear. This paper models the power system in Terceira island before the installation of any new renewable power plant. Thus, the steady-state and dynamic performance of the power system is characterised and most critical scenarios are identified.

Fault Current limiting in VSC-HVDC systems with MMC converters

High Voltage Direct Current (HVDC) transmission systems are playing an important role due to their economical and technical benefits in the countries where the electric grid is expanding fast. However, fault current interruption is still an unsolved challenge in these HVDC grids. In order to interrupt undesirable currents, DC circuit breakers can be used, but their capability is limited. With that scenario, Fault Current Limiters (FCL) arise as a good approach in order to reduce fault currents to a more manageable level allowing to increase the transmission ratings of an electrical system, without changing the equipment. Thus, the existing equipment would be able to handle the new currents and protect properly the system. In this paper, the general characteristics and classification of FCLs are explained. After that, a Solid State FCL is applied on a VSC-HVDC system with MMC converters. A simulation case of its optimal behavior is presented.