Name: relay settings for circuit fault protection
Uploaded: 2024-11-21T14:54:34.000Z
Duration: 1 min 26 s
Channel: JoVE

Les relais de surintensité, connectés au courant secondaire d’un transformateur de courant, sont cruciaux pour protéger les circuits.
Il en existe deux types : les relais de surintensité instantanés et les relais de surintensité temporisés.
Les relais de surintensité instantanés réagissent dès que le courant d’entrée dépasse une valeur prédéfinie, le courant de captation. Cette action alimente instantanément la bobine de déclenchement du disjoncteur.
Les relais de surintensité temporisée réagissent également à leur courant d'entrée, mais incluent un retard intentionnel qui dépend de l'amplitude du courant d'entrée.
Prenons l’exemple d’une sous-station électrique. Si un défaut se produit, provoquant une surtension du courant, un relais instantané se déclenchera immédiatement.
En revanche, un relais temporisé permettrait des surtensions mineures sans se déclencher, mais agirait toujours rapidement pour les défauts plus importants.
Ces relais ont deux réglages : la prise de courant et la numérotation de la minuterie.
Le choix du relais et ses paramètres dépendent des sources, des lignes et des charges. Différents relais fonctionnent plus rapidement sur des courants de défaut plus élevés.
Un relais électromécanique de surintensité temporisée fonctionne à l’aide d’un disque conducteur en aluminium, qui tourne sous un champ magnétique induit par le courant d’entrée. Plus le courant d’entrée est important, plus la fermeture du contact est rapide.

relais de surintensité

Overcurrent Relays

Les relais de surintensité, essentiels à la protection des circuits, sont connectés au courant secondaire d'un transformateur de courant. Il existe deux principaux types de relais de surintensité : instantané et temporisé.

Les relais de surintensité instantanés s'activent immédiatement lorsque le courant d'entrée dépasse une valeur prédéterminée, appelée courant de démarrage, alimentant instantanément la bobine de déclenchement du disjoncteur. Cette réponse rapide est essentielle pour traiter rapidement les défauts graves.

Les relais temporisés de surintensité, en revanche, comportent un délai intentionnel dans leur réponse, qui dépend de l'amplitude du courant d'entrée. Par exemple, dans une sous-station électrique, un relais instantané se déclencherait immédiatement lors de la détection d'une surintensité induite par un défaut, supérieure au courant de démarrage. En revanche, un relais temporisé permet le passage de surintensités mineures sans se déclencher, mais réagit rapidement aux défauts importants.

Ces relais sont configurés à l'aide de deux paramètres principaux : la prise de courant et le cadran de temporisation. La sélection appropriée du type de relais et de ses paramètres est influencée par les caractéristiques spécifiques des sources, des lignes et des charges du système. Les relais temporisés, en particulier, sont conçus pour fonctionner plus rapidement à des courants de défaut plus élevés, offrant ainsi une protection sur mesure.

Un relais de surintensité temporisé électromécanique fonctionne grâce à un disque conducteur en aluminium qui tourne dans un champ magnétique généré par le courant d'entrée. La vitesse de rotation du disque est proportionnelle à l'intensité du courant d'entrée, ce qui entraîne une fermeture plus rapide des contacts du relais avec des courants plus importants. Ce mécanisme assure une protection fiable et ajustable pour différentes conditions de défaut dans les systèmes électriques.

Ces relais sont essentiels au bon fonctionnement des dispositifs de protection, garantissant ainsi le fonctionnement sûr et fiable des systèmes électriques. En gérant efficacement les courants de défaut, les relais de surintensité contribuent à maintenir la stabilité du système et à prévenir les dommages matériels.

Relais de surintensité

Les relais de surintensité, connectés au courant secondaire d’un transformateur de courant, sont cruciaux pour protéger les circuits.
Il en existe deux types : Instantané ...

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relay settings for circuit fault protection

Overcurrent relays protect circuits by sensing excess current through the secondary side of a current transformer. They are an important part of circuit protection and help keep power systems stable when a fault occurs.

Two main relay types are used here: instantaneous and time-delay overcurrent relays. An instantaneous relay trips right away when current rises above the pickup current, which is the preset level that starts the relay. It then energizes the circuit breaker trip coil at once, which is useful for severe faults that need very fast action.

A time-delay overcurrent relay works differently. It adds a planned delay, and that delay depends on how large the input current is. In a power substation, it can let small surges pass without tripping, but it still responds quickly to major fault currents.

These relays are adjusted with two main settings: the current tap and the time dial. The best relay type and settings depend on the sources, lines, and loads in the system. Time-delay relays are also designed to act faster when fault current is higher.

An electromechanical time-delay relay uses a conducting aluminum disc that turns in a magnetic field created by the input current. The disc spins faster as the current increases, so the relay contacts close sooner during larger faults. This adjustable action helps protect equipment and supports reliable operation of power systems.

Relay Settings for Circuit Fault Protection

relay-settings-for-circuit-fault-protection

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overcurrent relays

Overcurrent relays protect circuits by sensing excess current through the secondary side of a current transformer. They are an important part of circuit protection and help keep power systems stable when a fault occurs. Two main relay types are used here: instantaneous and time-delay overcurrent relays. An instantaneous relay trips right away when current rises above the pickup current, which is the preset level that starts the relay. It then energizes the circuit breaker trip coil at once,...

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key terms and concepts

Learn how instantaneous and time-delay overcurrent relays protect circuits, use pickup current and time dial settings, and respond to fault currents.

Relay Settings for Circuit Fault Protection | JoVE K12

JoVE Core Electrical Engineering offers easy-to-understand animated videos that cover fundamental concepts of electric circuits along with circuit analysis techniques. It incorporates first-order and second-order circuits using operational amplifiers and circuit transformation concepts. The inclusion of practical design examples and real-world applications through scientist-in-action videos adds significant educational value, making complex concepts accessible.

electrical engineering

Relay Settings for Circuit Fault Protection

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