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

変流器の2次電流に接続された過電流リレーは、回路を保護するために重要です。
瞬時過電流リレーと時間遅延過電流リレーの2つのタイプがあります。
瞬時過電流リレーは、入力電流が事前に設定された値であるピックアップ電流を超えるとすぐに反応します。この動作により、サーキットブレーカーのトリップコイルが瞬時に通電されます。
時間遅延過電流リレーも入力電流に応答しますが、入力電流の大きさに依存する意図的な遅延が含まれます。
たとえば、変電所について考えてみます。障害が発生して電流が急増すると、瞬時リレーがすぐにトリップします。
対照的に、時間遅延リレーは、トリップせずに小さなサージを許容しますが、大きな障害に対しては迅速に動作します。
これらのリレーには、現在のタップとタイムダイヤルの2つの設定があります。
リレーの選択とその設定は、ソース、ライン、および負荷によって異なります。異なるリレーは、より高い障害電流でより高速に動作します。
電気機械式時間遅延過電流リレーは、入力電流によって誘起される磁場の下で回転する導電性アルミニウムディスクを使用して動作します。入力電流が大きいほど、接点のクローズが速くなります。

過電流リレー

Overcurrent Relays

過電流リレーは回路保護に不可欠で、変流器の二次電流に接続されます。過電流リレーには、瞬時型と時間遅延型の 2 つの主な種類があります。 
瞬時過電流リレーは、入力電流がピックアップ電流と呼ばれる所定の値を超えるとすぐに作動し、回路遮断器のトリップコイルに瞬時に通電します。この迅速な応答は、重大な障害に迅速に対処するために不可欠です。 
一方、時間遅延型過電流リレーには、入力電流の大きさに応じて意図的に応答を遅らせる機能があります。たとえば、変電所では、瞬時リレーは、ピックアップ電流を超える故障誘発電流サージを検出するとすぐに作動します。一方、時間遅延型リレーは、小さなサージは作動せずに通過させますが、重大な故障には迅速に対応します。 
これらのリレーは、電流タップと時間ダイヤルの 2 つの主要な設定を使用して構成されます。リレーの種類とその設定の適切な選択は、システム内の電源、線路、および負荷の特定の特性によって左右されます。特に、時間遅延リレーは、より高い故障電流でより速く作動するように設計されており、カスタマイズされた保護を提供します。 
電気機械式時間遅延過電流リレーは、入力電流によって生成される磁場内で回転する導電性アルミニウムディスクを介して作動します。ディスクの回転速度は入力電流の大きさに比例し、電流が大きいほどリレー接点がより速く閉じます。このメカニズムにより、電力システムのさまざまな障害状態に対して、信頼性が高く調整可能な保護が保証されます。 
これらのリレーは、保護装置の正確な作動に不可欠であり、電力システムの安全で信頼性の高い作動を保証します。過電流リレーは、故障電流を効果的に管理することで、システムの安定性を維持し、機器の損傷を防ぎます。

変流器の2次電流に接続された過電流リレーは、回路を保護するために重要です。
2つのタイプがあります:瞬間的な...

Education

JoVE Core

Electrical Engineering

電気工学

Unit 1

ユニット1

System Protection

システム保護

KEY TERMS AND CONCEPTS

主要用語と概念

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

instrument transformers

Voltage and Current Sensing in Power Grids

Instrument transformers help power substations measure voltage and current safely. They create isolated replicas of electrical signals for measurement and protection. These devices support protective relays and other monitoring equipment that keep power systems stable and reliable. The two main types are voltage transformers, or VTs, and current transformers, or CTs. A voltage transformer reduces the primary voltage to a lower level that relays and measuring devices can use. A current...

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,...

radial system protection

Breaker Coordination in Radial Systems

Breaker coordination in radial systems uses time-delay overcurrent relays to limit load interruption. When a fault happens, the nearest breaker should open first. Upstream breakers stay closed because they are set with longer delays. This lets the fault be isolated while the rest of the system keeps running. If a fault is downstream of the third breaker, only the third breaker should trip. That removes power from the load beyond the fault. The second breaker keeps a longer delay setting, so...

reclosers and fuses

Fault Coordination with Reclosers and Fuses

Fault coordination with reclosers and fuses helps protect radial distribution circuits. A recloser is an automatic switch that interrupts AC power and then closes again on a preset schedule. This brief outage can clear temporary faults on overhead lines, such as those caused by tree limbs or wildlife, and it can improve overall reliability. Reclosers and their ground-level hazards also matter. Contact with a recloser or with a broken energized conductor on the ground can be dangerous. That is...

directional relays

Directional Relays in Power System Protection

Directional relays help protect power systems by telling forward faults from reverse faults. They are used when fault current flows mainly in one direction on a line. This makes the relay useful for safe and efficient fault clearing. On a protected line, a fault downstream, or to the right of the current transformer, usually makes the fault current lag the bus voltage by about 90 degrees. This is called the forward direction. A fault upstream, or to the left, may make the fault current lead...

zones of protection

Power System Protection Zones

Power system protection zones divide the network into sections so faults can be isolated quickly. These zones can include generators, transformers, buses, transmission lines, distribution lines, and motors. Each zone is shown with closed dashed lines and contains one or more components. Circuit breakers are placed at the borders where protection zones meet. If a fault happens in one zone, the related breakers open and disconnect only that section. A fault in one area, such as a kitchen in the...

line protection with impedance relays

Impedance Relays for Fault Detection

Impedance relays help protect power lines by watching the voltage-to-current ratio on a line. They measure the apparent impedance, which is the electrical opposition the relay sees at that point in the system. This makes them useful when time-delay overcurrent relays are hard to coordinate in complex radial systems and when directional overcurrent relays are difficult to use in multi-source transmission loops. These relays respond strongly during a fault. As current rises and voltage falls,...

differential relays

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...

pilot and numeric relaying

Pilot Relays and Digital Protection

Pilot relays and numeric relays help protect power systems. Pilot relaying is a form of differential protection, which compares electrical quantities at equipment terminals through a communication channel instead of a direct relay link. It is especially useful for transmission lines with terminals far apart, often up to 80 km on 69 to 115 kV lines. Pilot relaying can use several communication channels. Pilot wires are separate electrical circuits that operate at DC, 50 to 60 Hz, or audio...

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 電気工学 は、電気回路の基本概念と回路解析テクニックを網羅したアニメーションビデオシリーズです。オペアンプと回路変換および 1 次・ 2 次回路の概念を網羅しています。実験を撮影した実写動画では、設計例や現代社会での応用が含まれており、複雑な概念も分かりやすく学習いただけます。

electrical engineering

Relay Settings for Circuit Fault Protection

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