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Concept

Court-circuit

Un court-circuit est la mise en connexion volontaire ou accidentelle de deux points (ou plus) d’un circuit électrique entre lesquels il y a une différence de potentiel, par un conducteur de faible résistance. Il donne naissance à un courant de court-circuit et, généralement, à une élévation de la température des conducteurs. Électrotechnique Sur un réseau de distribution électrique, les courts-circuits peuvent être classés : ; Selon leur durée :

auto-extincteur, si le défaut disparaît de lui-même en un temps très court, sans provoquer de déclenchement des organes de protection (fusible ou disjoncteur),
fugitif, si le défaut ne disparaît qu'après une ou plusieurs coupures brèves du réseau d'alimentation sans nécessiter d'intervention,
semi-permanent, si le défaut ne disparaît qu'après une ou plusieurs coupures longues du réseau d'alimentation (quelques dizaines de secondes) sans nécessiter d'intervention,
permanent, si le défaut provoque un déclenchement définitif

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Résumé

auto-extincteur, si le défaut disparaît de lui-même en un temps très court, sans provoquer de déclenchement des organes de protection (fusible ou disjoncteur),
fugitif, si le défaut ne disparaît qu'après une ou plusieurs coupures brèves du réseau d'alimentation sans nécessiter d'intervention,
semi-permanent, si le défaut ne disparaît qu'après une ou plusieurs coupures longues du réseau d'alimentation (quelques dizaines de secondes) sans nécessiter d'intervention,
permanent, si le défaut provoque un déclenchement définitif

Source officielle

À propos de ce résultat

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Concepts associés (37)

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Cours associés (53)

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Séances de cours associées (177)

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EE-405: Fundamentals of electrical circuits and systems

This course provides an overview of fundamental concepts of signal processing and electric circuits.

EE-370: Electric power systems

Ce cours décrit les composants d'un réseau électrique. Il explique le fonctionnement des réseaux électriques et leurs limites d'utilisation. Il introduit les outils de base permettant de les piloter.

EE-445: Microwaves, the basics of wireless communications

This course is an introduction to microwaves and microwave passive circuits. A special attention is given to the introduction of the notion of distributed circuits and to the scattering matrix

Development of a system for part quality prediction and process parameters adjustment in wire electrical discharge machining

Olcay Akten

In the past decades, wire electric discharge machining (W-EDM) has undergone a number of techno-logical developments aimed at improving its process performance. Still the current practice of W-EDM is not defect-free and results in a number of surface related defects on the machined parts. The main defects related to surface quality of parts produced by the W-EDM process include the occurrence of surface lines, surface roughness and the occurrence of recast layer on the machined surface. The experimental evidence suggests that surface defects in W-EDM occur mainly due to short-circuiting or abnormal sparks. If the W-EDM process is controlled to minimize the duration of short circuit or abnormal sparks, the occurrence of surface defects can be minimized. Furthermore, online monitoring of the spark quality can help minimize the occurrence of surface lines by first predicting the possible occurrence of surface lines in W-EDM as a function of certain critical process variables, namely, discharge gap and spark frequency, and then proactively implementing the corrective action in the form of adjustment of vital process parameters, like pulse-off time, before the sequence of abnormal sparks could develop into a visible surface line. Two systems are proposed to achieve the objectives mentioned above: an offline multiple-input multiple-output (MIMO) fuzzy-nets prediction system and a multi-objective optimization system for process parameters adjustment and an online prediction and adjustment system based on the short circuit duration. For the offline prediction system, the two part quality characteristics considered in this thesis are surface roughness and recast layer thickness. A fuzzy logic based approach called fuzzy-nets approach for the prediction of these part quality characteristics on the basis of the initial conditions is proposed. A hybrid multi-objective optimization method combining fuzzy-nets prediction technique and genetic algorithm is applied to find best setting of process parameters based on desired surface roughness and minimium recast layer thickness. The online prediction and adjustment system comprises: (i) a procedure for the online prediction of the occurrence of surface lines in W-EDM based on the short circuit duration, and (ii) a procedure for online adjustment pulse-off time (electrical process parameter) to prevent the occurrence of surface lines if and when their occurrence is predicted. Both systems required intensive experiments based on carefully designed experiment plans to collect and assess the training data for the different fuzzy rule bases. A case study from GF Machining Solutions Ltd. illustrating the different issues related to the proposed approaches is described. The experimental results validate the proposed approach for both online and offline systems.

EPFL2015

Chargement

VHDL-AMS Virtual Prototyping of a Generator Circuit Breaker Ablation Monitoring System

Qianqian Ha, Yannick Maret, Juan Sebastian Rodriguez Estupinan, Alain Vachoux

Generator Circuit Breakers (GCBs) are commonly used in electrical power generation systems to protect key equipment such as transformers and generators from damage due to overload or short-circuit. However the interruption and feeding of high currents lead to the ablation of the electrical contact system of the breaker. This deterioration process needs to be monitored in order to guarantee the healthy condition of the breaker. In this paper, we propose a virtual prototype of a GCB fitted with an ablation monitoring system. This is an early model of the complete system, which is highly desired before the physical implementation, since it facilitates the study of detection methods and the exploration of system limitations. The virtual prototype is implemented in VHDL-AMS with certain low-level models described in SPICE. The virtual prototype has been validated by measurements performed on the real system. It is therefore adequate for performing design optimization and to obtain useful observations for further usage of the monitoring system.

IEEE Conference Press2015

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Potential Induced Degradation Mechanism in Rear-Emitter Bifacial Silicon Heterojunction Solar Cells Encapsulated in Different Module Structures

Olatz Arriaga Arruti, Christophe Ballif, Luca Gnocchi, Quentin Thomas Jeangros, Alessandro Francesco Aldo Virtuani

Recent studies showed that silicon heterojunction (SHJ) solar cells can be prone to potential induced degradation (PID) when encapsulated with ethylene vinyl acetate (EVA). Here, to gain understanding in the role of EVA, we perform PID test in humid conditions (85 degrees C/85% RH) under a negative bias (-1000V). We study the effect of moisture ingress and cover materials by using different module structures. We focus on studying both sides of the cell for modules packaged in a glass/glass scheme after 500 hours of test (corresponding to similar to 5 times the duration foreseen by the corresponding IEC standard). The front-side degradation is dominated by a reduction in short-circuit current (J(SC)), whereas the rear-side degradation is driven by a loss in fill factor (FF). EQE measurements show that increased front-surface recombination is largely responsible for the observed degradation of the front-side. From TEM and EDX measurements, it seems that the degradation at the cell level is predominantly caused by diffusion of sodium into the cell, which is triggered by humidity and low encapsulant resistivity. Assuming that the Na is also accumulated at the rear-side of the cell, this would create defects at the p-n junction, leading to the loss of FF observed.

IEEE2021

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Circuit électrique

vignette|Circuit électrique à Calcutta, Inde. Un circuit électrique au sens matériel est un ensemble simple ou complexe de composants électriques ou électroniques, y compris des simples conducteurs,

Electrical resistance and conductance

The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrica

Fusible (électricité)

Le coupe-circuit à fusible (souvent simplifié en fusible) est, en électricité et en électronique, un organe de sécurité dont le rôle est d'ouvrir un circuit électrique lorsque le courant électrique