Name: voltage and current sensing in power grids
Uploaded: 2024-11-21T14:54:34.000Z
Duration: 1 min 23 s
Channel: JoVE

계기 변압기에는 전압 및 변류기가 포함됩니다.
변류기의 1차 권선에는 일반적으로 단일 회전 또는 전도성 막대가 있으며 그 주위로 2차 권선이 여러 번 감겨 있습니다.
1차 권선을 통해 흐르는 고전류는 2차 권선에서 감소된 전류를 유도합니다. 2차 권선은 일반적으로 최대 전류 흐름을 허용하기 위해 제로 임피던스 측정 장치에 직렬로 연결됩니다. 
변류기의 성능은 오류를 유발하는 포화 없이 1차 전류를 정확하게 복제하는 데 달려 있습니다. 하지만 변류기는 션트 여기 임피던스를 위해 일부 전류를 잃을 수 있습니다.
이제 2차 권선보다 권선 수가 더 많은 1차 권선으로 구성된 전압 변압기를 고려하십시오.
2차 권선은 고임피던스 전압 감지 장치에 병렬로 연결되어 정확한 전압 전달을 보장합니다.
보호를 위해 전압 변압기는 이상적인 것으로 모델링되어 1차 전압의 축소된 동상 표현을 생성합니다. 
그러나 전압 변압기는 작은 전압 강하와 위상 변이를 경험합니다.

계기용 변압기

전압 변압기(VT)와 전류 변압기(CT)로 구성된 계기용 변압기는 측정 및 보호 목적으로 전류 또는 전압의 분리된 복제본을 제공함으로써 변전소에서 중요한 역할을 합니다. 전압 변압기는 1차 전압을 릴레이 작동 및 측정에 적합한 수준으로 낮추는 반면, 전류 변압기는 1차 전류를 줄입니다. 전류 변압기의 1차 권선은 종종 단일 턴으로 구성되며, 전력 시스템의 1차 도체를 코어에 꿰어 넣음으로써 달성되지만, 일부 응용 분야에서는 여러 개의 1차 턴이 필요할 수 있습니다.

보호 목적으로 전압 변압기는 1차 전압의 축소된 동상 표현을 생성하도록 이상적으로 설계됩니다. 전압 변압기의 2차는 고임피던스 전압 감지 장치에 연결하여 전체 2차 전압이 감지 장치에 나타나도록 해야 합니다. 반대로 전류 변압기의 2차는 저임피던스 전류 감지 장치에 연결하여 전체 2차 전류가 감지 장치를 통해 흐르도록 해야 합니다.

실제 응용 분야에서 전압 변압기는 1차 및 2차 측 사이에 전압 강하 및 위상각 차이를 경험할 수 있습니다. 마찬가지로 전류 변압기에서 일부 전류는 저임피던스 감지 장치와 변압기의 션트 여기 임피던스 사이에 분할될 수 있습니다. 전류 변압기의 성능은 상당한 오류나 포화 효과 없이 1차 전류를 정확하게 재현하는 능력에 크게 좌우됩니다.

이러한 변압기는 보호 계전기 및 측정 장치의 정확한 작동에 필수적이며 전력 시스템의 안전하고 안정적인 작동을 보장합니다. 계기 변압기는 고전압 및 전류를 축소하여 관리 가능한 범위 내에서 전기 매개변수를 모니터링하고 제어하여 시스템 안정성과 보호를 유지합니다.

계기 변압기에는 전압 및 변류기가 포함됩니다.
변류기의 1차 권선은 일반적으로 단일 회전 또는 전도성을 갖습니다.

Education

교육

JoVE Core

Electrical Engineering

전기공학

Unit 1

제1단원

System Protection

시스템 보호

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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 transformer scales down the primary current in the same way.

A current transformer often uses a single-turn primary winding. In many cases, the power conductor is simply threaded through the core to act as that turn. Some applications need multiple primary turns instead.

For protection, a voltage transformer should produce a scaled-down secondary voltage that stays in phase with the primary voltage. Its secondary should connect to a high-impedance voltage-sensing device. That setup lets the full secondary voltage appear across the sensing device.

A current transformer works differently. Its secondary should connect to a low-impedance current-sensing device so the full secondary current flows through the device. In practice, some current can split between the sensing device and the transformer’s shunt excitation impedance. VTs can also show voltage drops and phase-angle differences between the primary and secondary sides.

Current transformer performance depends on how well it reproduces the primary current without large errors or saturation. By reducing very high voltages and currents to manageable levels, instrument transformers let engineers monitor electrical values and protect the power system.

Voltage and Current Sensing in Power Grids

voltage-and-current-sensing-in-power-grids

instrument transformers

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 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

Explore how voltage transformers and current transformers scale high power-grid signals for safe measurement, relay operation, and system protection.

Voltage and Current Sensing in Power Grids | 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

Voltage and Current Sensing in Power Grids

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