Name: differential relay protection in power systems
Uploaded: 2024-11-21T14:54:35.000Z
Duration: 1 min 20 s
Channel: JoVE

Os relés diferenciais protegem geradores, barramentos e transformadores.
Em um gerador sem falhas, transformadores de corrente idênticos mantêm o relé inativo, pois nenhuma corrente flui através da bobina de operação do relé.
Uma falha interna, como um curto-circuito fase-terra ou fase-fase, interrompe esse equilíbrio, causando corrente diferencial e potencialmente acionando o relé.
Os relés diferenciais eletromecânicos, como os relés de trave de equilíbrio, operam quando a força de um lado excede a do outro. Como não há dois transformadores de corrente idênticos, correntes diferenciais significativas podem ocorrer durante faltas externas, mesmo com correntes iguais.
Para proteção do barramento, cada fase usa um relé diferencial. Se um for ativado, todos os disjuntores trifásicos conectados ao barramento serão abertos.
Se não houver falha interna entre os transformadores de corrente, a corrente diferencial do relé permanece zero. No entanto, uma falha de barramento gera uma corrente diferencial diferente de zero, acionando o relé.
Transformadores maiores que 10 MVA usam relés diferenciais para proteção.
Existem adaptações especializadas para transformadores multi-enrolamentos e transformadores reguladores de tensão.

relés diferenciais

Differential Relays

Relés diferenciais são usados ​​para proteger geradores, barramentos e transformadores comparando grandezas elétricas em diferentes pontos. Quando ocorre uma falha, a diferença de corrente entre os dois pontos aciona o relé para operar, abrindo o disjuntor. Em condições normais, a corrente que entra (i_1) e sai (i_2) de um gerador são iguais. Quando ocorre uma falha, no entanto, essas correntes se tornam desiguais, e a diferença de corrente flui na bobina de operação do relé, fazendo com que o relé dispare. Um relé diferencial eletromecânico, conhecido como relé de feixe de equilíbrio, opera com base na comparação de forças eletromagnéticas geradas pela corrente diferencial. O relé dispara quando a força na bobina de operação excede a força de restrição. A condição para operação do relé é dada por:

<img alt="Equation1" src="/files/ftp_upload/16167/16167_PT_Equation1.svg" style="height: 30px;">

 A proteção do barramento é obtida usando relés diferenciais para detectar falhas dentro da zona do barramento. O relé opera quando a soma das correntes que entram e saem do barramento não é zero, indicando uma falha.


 A proteção diferencial para transformadores é mais complexa devido à presença de diferentes enrolamentos e relações de espiras. Quando o transformador opera em condições normais sem falha interna, as correntes primária e secundária, ajustadas por suas respectivas relações de transformador de corrente (TC), devem se equilibrar. Mas no caso de uma falha interna, a corrente diferencial flui através da bobina de operação do relé, causando seu disparo.


 Para transformadores trifásicos, os TCs devem ser conectados corretamente para levar em conta as mudanças de fase causadas pelos enrolamentos do transformador. Isso garante que as correntes secundárias estejam em fase, evitando a operação incorreta do relé. Para transformadores Y-Δ, os TCs no lado Y devem ser conectados em Δ, e os TCs no lado Δ devem ser conectados em Y.


 Os métodos de proteção diferencial foram adaptados para várias configurações de transformadores, incluindo transformadores de enrolamento múltiplo, transformadores reguladores de ângulo de fase e transformadores com conexões especiais.

Relés Diferenciais

Os relés diferenciais protegem geradores, barramentos e transformadores.
Em um gerador sem falhas, transformadores de corrente idênticos mantêm o relé inativo como ...

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Electrical Engineering

Engenharia Elétrica

Unit 1

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System Protection

Proteção do Sistema

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

differential relay protection in power systems

Differential relays protect generators, buses, and transformers by comparing currents at different points in a power system. When the currents do not match, the relay detects the difference and opens the circuit breaker. Under normal conditions, the current entering a generator, i1, equals the current leaving it, i2. If a fault occurs, these currents become unequal, and the difference current flows through the relay operating coil to trip the relay.

An electromechanical differential relay is called a balance beam relay. It works by comparing the electromagnetic forces created by the differential current. The relay trips when the force on the operating coil becomes greater than the restraining force. This same basic idea is used to protect bus zones. For bus protection, the relay operates when the total current entering and leaving the bus is not zero, which signals a fault inside the bus area.

Differential protection is more complex for transformers because they have different windings and turn ratios. Under normal operation, with no internal fault, the primary and secondary currents should balance after they are adjusted for their current transformer, or CT, ratios. If an internal fault occurs, differential current flows through the relay operating coil and causes a trip.

Three-phase transformers also require the CTs to be connected correctly to match phase shifts caused by the windings. This keeps the secondary currents in phase and helps prevent unwanted relay operation. For Y-Δ transformers, the CTs on the Y side should be connected in Δ, and the CTs on the Δ side should be connected in Y. These protection methods have also been adapted for multi-winding transformers, phase-angle regulating transformers, and transformers with special connections.

Differential Relay Protection in Power Systems

differential-relay-protection-in-power-systems

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differential relays

Differential relays protect generators, buses, and transformers by comparing currents at different points in a power system. When the currents do not match, the relay detects the difference and opens the circuit breaker. Under normal conditions, the current entering a generator, i1, equals the current leaving it, i2. If a fault occurs, these currents become unequal, and the difference current flows through the relay operating coil to trip the relay. An electromechanical differential relay is...

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key terms and concepts

Learn how differential relays protect generators, buses, and transformers by sensing current imbalance and tripping during faults, with CT connection details.

Differential Relay Protection in Power Systems | 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

Differential Relay Protection in Power Systems

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