1,721,336 research outputs found
Protection of Trees against Lightning Strikes as a Measure to Prevent Fires and Loss of Human Life
Full text linkLighting strikes have been the catalyst of massive uncontrolled fires in areas of combustible vegetation. In some regions, lightning strikes may be a relatively unusual occurrence (e.g., California), but instead they seem to have become a major contributor to the propagation of wildfires, as a byproduct of climate change. Given such unusual weather, wildfires originating from lightning are an increasing threat. In this paper, the authors discuss the withstand capability of trees against lightning and introduce a proactive approach to prevent wildfires by the deployment of tree lighting protection systems (TLPS) to protect forested areas, where deemed necessary by the tree risk assessment
Assessing the electricity consumption of outdoor lighting systems in the presence of automatic control: The OL-BAC factors method
No full textBuilding automation systems are able to influence significantly buildings’ energy performance. The BAC factors method, presented for the first time by the International Standard EN 15232, is the most used and simple instrument for evaluating the impact of such systems in terms of reduction of the electrical and thermal energy consumption of buildings services. Nevertheless, Standard EN 15232 does not take into consideration the automation of lighting systems serving buildings’ external areas like passages, gardens, entrance walkways, etc. In some cases, such areas can be very extended and, as a consequence, responsible for a not negligible percentage of the overall electricity consumption. Taking this last consideration as a basis, in this paper, a method is proposed for the definition and the evaluation of a new BAC factor for outdoor lighting systems, named OL-BAC factor. The method can be considered complementary to the one proposed by the Standard EN 15232 for the indoor lighting energy consumption estimation and proposes some improvements in the implementation of the latter. In particular, in this paper, the OL-BAC factors are calculated showing the importance of two parameters that are not taken into account by the Standard EN 15232: the latitude of the installation site and the energy absorbed by the devices for the luminaires’ automatic control
Analysis and simulations of the primary frequency control during a system split in continental europe power system
Full text linkThe occurrence of system separations in the power system of Continental Europe has been observed in recent decades as a critical event which might cause power imbalances higher than the reference incident specified per system design, representing an actual challenge for the stability and safe operation of the system. This work presents an analysis and simulations of the primary frequency control in the Continental Europe synchronous area in conditions of system separation. The adopted approach is based on fundamental aspects of the frequency-containment reserve process. The analysis takes an actual event into consideration, which determined the separation of the system in January 2021. The main purpose of the work is the development of specific models and simulations able to reproduce the actual split event. Due to specific arrangements discussed in detail, it is possible to obtain a substantial match between the simulations and the frequencies registered after the system split. The work also provides insight into the importance of the temporal sequence of power imbalances and defensive actions in the primary frequency control process. The models developed in the work are finally used to investigate the separation event under different operating conditions, such as missing defensive actions and low inertia scenarios
A Cost-Effective Solution for Clearing High-Impedance Ground Faults in Overhead Low-Voltage Lines
Full text linkDowned distribution conductors in overhead distribution systems may not be a concern for equipment but greatly challenge the safety of persons, as well as the integrity of properties. Standard overcurrent protective devices may not be able to detect the magnitudes of currents resulting from high-impedance ground faults. Sophisticated relays able to detect high-impedance ground faults have been available to electric utilities. However, their implementation is rather uncommon, especially in developing countries, most likely due to their costs. In this paper, the authors formalize the problem, and propose a possible cost-effective solution for low-voltage overhead lines with neutral wire. This solution consists of a metal hook underneath the line conductors, attached to the pole and connected to the neutral wire. In the case of a falling line, the hook would be contacted and a line-to-neutral short circuit would occur; this would positively activate existing standard overcurrent devices, which can therefore disconnect the supply. Costs related to the installation of the device to existing overhead lines are herein analyzed. The effectiveness of the proposed solutions for two different voltage levels (400 V in European countries and 240 V in the USA) is also discussed
On the de-energization of over-head low-voltage lines under high-impedance fault conditions
No full textDowned distribution conductors in overhead distribution systems, may not be a concern for equipment, but greatly challenge the safety of persons, as well as the integrity of properties. Upstream overcurrent protective devices may not be able to detect the magnitudes of fault currents resulting from these high-impedance faults. Even though protective devices capable to detect such faults have been available on the market, not all the utilities have equipped their stations with these products, likely due to the costs. In this paper, the authors formalize the problem, and propose a possible cost-effective solution for the low-voltage over-head lines with neutral wire. Such solution includes a metal hook underneath the line conductors, supported by the pole, and connected to the neutral wire. This arrangement would cause a line-to-neutral short circuit, positively activating existing over-current devices, which can therefore disconnect the supply. Costs and possible safety issues for workers related to the installation of the device to existing overhead lines are herein also delineated
Generalized power-angle control for grid-forming converters: A structural analysis
No full textSeveral control schemes have been recently proposed and studied as grid-forming controls for power converters. In all these schemes, the power-angle control loop is the part which defines the fundamental capabilities of the grid-forming control: that control loop governs in fact the inherent synchronization mechanism of the power converter, the power sharing with the other generation sources in the system and the oscillatory characteristics of the converter-based resource. This article introduces a general formulation for the power-angle control characterizing the grid-forming concept for power converters. The generalized power-angle control is based on a polynomial fraction formulation, and it is arranged according to physical requirements and constraints. The structural analysis provides an insight into the capabilities and the design of the power-angle control loop of a grid-forming scheme. The generalized formulation is eventually applied to some common grid-forming controls like the power-synchronization control and the virtual synchronous machine, showing how the proposed generalized power-angle control can effectively realize different control structures
Grid-Following and Grid-Forming MODELS in ATP-EMTP for Power Systems Simulation
No full textThe paper presents the models of grid-following and grid-forming converters in the software ATP-EMTP for power systems simulation. The models are developed using the MODELS language, they are described in details discussing all issues and aspects related to the implementation, and they are also shared as open source models. The models are validated with a simulation-based approach, comparing the results with the models developed in MATLAB/Simulink and in NEPLAN, considering both the phasor RMS and EMT time domains, and thus performing a comprehensive cross-platform and cross-domain validation. In line with the spirit of the ATP software and community, the models of grid-following and grid-forming converters are developed with the purpose of sharing them, and contributing in this way to the creation of a common basis for the integration of these elements into the analysis and simulation of power systems
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