Name: directional relays in power system protection
Uploaded: 2024-11-21T14:54:35.000Z
Duration: 1 min 25 s
Channel: JoVE

단방향 고장 전류용으로 설계된 방향성 계전기는 전력 시스템의 안전성과 효율성을 향상시킵니다.
방향성 릴레이가 있는 전력선에서 변류기 오른쪽의 오류로 인해 고장 전류가 버스 전압을 거의 90도 지연시키며, 이를 순방향이라고 합니다. 반대로, 왼쪽 결함으로 인해 고장 전류가 버스 전압을 거의 90도 앞서게 되며, 이를 역방향이라고 합니다
방향성 계전기는 레퍼런스 전압 및 전류 입력을 사용하여 전류와 전압 사이의 각도를 기반으로 트립 및 블록 영역을 정의합니다.
과전류 릴레이와 직렬로 연결된 방향 계전기는 변류기의 2차 전류가 과전류 계전기 픽업 값을 초과하고 정방향 트리핑 방향일 때만 차단기 트립 코일에 전원을 공급합니다.
와트시 미터처럼 작동하는 전기 기계 방향 계전기는 전압 및 전류 코일과 회전 디스크 요소를 사용합니다.
순방향 오류는 회전 디스크에서 최대 양의 토크를 생성하여 릴레이 접점을 닫는 반면, 역방향 오류는 기계적 정지에 의해 제한되는 최대 음의 토크를 생성합니다.
2-소스 시스템의 경우, 방향성 릴레이는 조정 문제를 극복할 수 있으며, 고장 발생 시 부하에 대한 중단 없는 서비스를 보장할 수 있습니다.

방향 릴레이

Directional Relays

방향성 릴레이는 단방향 고장 전류를 관리하는 데 필수적이며 전력 시스템의 안전성과 효율성을 향상시킵니다. 방향성 릴레이가 장착된 전력선에서 전류 변압기의 하류(오른쪽) 고장은 일반적으로 고장 전류가 버스 전압보다 약 90도 지연되는 것을 발생시킵니다. 이를 순방향이라고 합니다. 반면 상류(왼쪽) 고장은 고장 전류가 버스 전압보다 거의 90도 앞서는 것을 발생시킬 수 있으며 이를 역방향이라고 합니다. 그러나 실제 위상 변화는 시스템 임피던스와 특정 고장 조건에 따라 달라집니다.

방향성 릴레이는 기준 전압 및 전류 입력을 사용하여 전류와 전압 사이의 각도에 따라 트립 및 차단 영역을 정의합니다. 일반적으로 기준 전압은 버스 또는 선-접지 전압에서 가져오고 전류는 전류 변압기(CT)에서 가져옵니다. 과전류 릴레이와 페어링할 때 방향성 릴레이는 CT의 2차 전류가 과전류 릴레이 픽업 값을 초과하고 전방 트립 방향과 정렬되는 경우에만 차단기 트립 코일을 활성화합니다.

전기 기계식 방향 릴레이는 와트시 미터와 유사하게 기능합니다. 회전 디스크 요소와 함께 전압 및 전류 코일을 통합합니다. 정방향 오류는 회전 디스크에 최대 양의 토크를 생성하여 릴레이 접점을 닫습니다. 반대로 역방향 오류는 최대 음의 토크를 생성하며, 이는 기계적 정지로 제한됩니다.

2소스 시스템에서 방향성 릴레이는 조정 과제를 해결하여 고장 중에 부하에 대한 지속적인 서비스를 보장합니다. 방향성 릴레이는 순방향 및 역방향 고장 조건을 정확하게 구별하여 정확하고 신뢰할 수 있는 고장 분리를 가능하게 하여 시스템 안정성을 유지하고 중단을 최소화합니다. 최신 디지털 방향성 릴레이는 자체 모니터링, 통신 기능, 정확한 타이밍 조정과 같은 고급 기능을 제공하여 전력 시스템 보호의 신뢰성과 효과를 더욱 향상시킵니다.

단방향 고장 전류용으로 설계된 방향성 계전기는 전력 시스템의 안전성과 효율성을 향상시킵니다.
방향성 릴레이가 있는 전력선에서 ...

Education

교육

JoVE Core

Electrical Engineering

전기공학

Unit 1

제1단원

System Protection

시스템 보호

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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 the bus voltage by nearly 90 degrees. That is the reverse direction. The exact phase shift can change with system impedance and fault conditions.

These relays compare a reference voltage and a current input to set trip and block zones. The reference voltage is often taken from the bus or from line-to-ground voltage. The current comes from the current transformer, or CT. When a directional relay works with an overcurrent relay, the breaker trip coil operates only if the CT secondary current passes the pickup value and points in the forward-tripping direction.

Electromechanical directional relays work much like watt-hour meters. They use voltage coils, current coils, and a rotating disc. Forward faults create maximum positive torque, which closes the relay contacts. Reverse faults create maximum negative torque, and mechanical stops restrain the disc.

Directional relays are especially important in two-source systems, where coordination can be difficult. They help keep loads in service during faults by isolating only the faulted section. By separating forward from reverse fault conditions, these relays support stable and reliable power system protection. Modern digital directional relays add self-monitoring, communication features, and precise timing adjustments.

Directional Relays in Power System Protection

directional-relays-in-power-system-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

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,...

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 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 directional relays distinguish forward and reverse faults, coordinate with overcurrent relays, and improve power system protection.

Directional Relays in Power System 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

Directional Relays in Power System Protection

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