Name: how transmission lines lose energy
Uploaded: 2024-11-21T14:54:23.000Z
Duration: 1 min 25 s
Channel: JoVE

특정 온도에서 도체의 DC 저항은 저항률, 길이 및 단면적에 따라 달라집니다.
저항률은 도체 금속에 따라 다르며 어닐링 된 구리가 측정 표준입니다.
20ºC에서 경질 알루미늄의 저항률은 구리 전도도의 61%입니다.
나선형, 온도, 주파수 및 전류 크기 충격 저항과 같은 요소. 연선의 나선형은 길이와 DC 저항을 1-2% 증가시킵니다.
저항률은 온도에 따라 선형적으로 변합니다.
AC 저항은 실제 전력 손실과 rms 전류에 의해 결정됩니다.
스킨 효과는 주파수에 따라 증가하여 AC 저항을 증가시키는 반면 자기 도체의 경우 저항은 전류 크기에 따라 달라집니다.
도체 사이 또는 접지에 대한 실제 전력 손실을 설명하는 컨덕턴스는 주로 절연체 누설 전류와 코로나 영향으로 인한 것입니다. 이것들은 도체 손실에 비해 경미하지만.
절연체 누설 전류는 오염 물질과 습기의 영향을 받습니다.
높은 전기장 강도 이온화 공기로 인해 발생하는 코로나는 기상 조건과 도체 표면의 불규칙성에 따라 달라집니다.

저항 및 전도도

Resistance and Conductance

주어진 온도에서 도체의 DC 저항은 저항률, 길이 및 단면적의 영향을 받습니다. 저항률은 도체 재료의 고유한 특성이며, 어닐링 구리는 측정을 위한 국제 표준으로 사용됩니다. 예를 들어, 20도 섭씨에서 경질 알루미늄의 저항률은 어닐링 구리의 표준 전도도의 61%입니다.

다양한 요인이 도체의 저항에 영향을 미칩니다. 꼬인 도체의 나선형은 길이를 늘리고 결과적으로 DC 저항을 1-2% 증가시킵니다. 또한 저항률은 정상 작동 범위에서 온도에 따라 선형적으로 변합니다. 주파수와 전류 크기도 중요한 역할을 합니다. 주파수에 따라 강화되는 스킨 효과는 AC 저항을 증가시킵니다. 자기 도체에서 저항은 전류 크기에 따라 더욱 영향을 받습니다.

AC 또는 유효 저항은 실제 전력 손실과 제곱 평균 루트(rms) 도체 전류에 의해 결정됩니다. 피부 효과는 주파수가 높을수록 현저해져 전류가 도체 표면 근처에 집중되어 AC 저항이 증가합니다. 이 효과는 자기적 특성이 있는 도체에서 더 두드러지는데, 여기서 저항은 전류의 크기에 따라 달라집니다.

도체 간 또는 접지 간 실제 전력 손실과 관련된 전도도는 주로 절연체 누설 전류와 코로나 효과로 인해 발생합니다. 이러한 손실은 도체 손실에 비해 상대적으로 사소하지만 송전선 효율의 전반적인 평가에 중요합니다. 절연체 누설 전류는 누적된 오염 물질과 기상 조건, 특히 습기의 영향을 받습니다.

코로나는 도체 주변의 전기장이 주변 공기를 이온화하여 전도를 일으킬 때 발생합니다. 코로나 손실은 기상 조건과 도체 표면의 불규칙성에 따라 달라지며, 이는 이온화 효과를 악화시킬 수 있습니다. 이러한 요소를 이해하는 것은 송전선 성능을 최적화하고 에너지 손실을 최소화하는 데 필수적입니다.

특정 온도에서 도체의 DC 저항은 저항률, 길이 및 단면적에 따라 달라집니다.
저항률은 도체에 따라 다릅니다 ...

Education

교육

JoVE Core

Electrical Engineering

전기공학

Unit 1

제1단원

Transmission Line Parameters

송전선로 파라미터

KEY TERMS AND CONCEPTS

주요 용어 및 개념

how transmission lines lose energy

Transmission lines lose energy through resistance and conductance. DC resistance depends on a conductor’s resistivity, length, and cross-sectional area. Resistivity is a material property, and annealed copper is the international standard used for measurement.

Material choice and conductor shape both matter. Hard-drawn aluminum at 20 degrees Celsius has a resistivity equal to 61% of the standard conductivity of annealed copper. Stranded conductors also gain a little extra resistance because spiraling makes the path longer. This increase is usually about 1% to 2%.

Temperature changes resistance as well. Over normal operating ranges, resistivity rises or falls in a linear way with temperature. AC resistance, or effective resistance, also depends on frequency and current magnitude. At higher frequencies, the skin effect pushes current toward the outside of the conductor and increases AC resistance.

Magnetic conductors show an added effect. Their resistance can change with the size of the current. AC resistance is found from real power loss and the rms, or root mean square, conductor current. Conductance describes real power loss between conductors or to the ground, and it mainly comes from insulator leakage currents and corona.

These losses are usually small compared with conductor losses, but they still matter for transmission line efficiency. Leakage current increases when dirt and other contaminants build up on insulators, and moisture from weather makes this worse. Corona occurs when the electric field around a conductor ionizes the air. Its loss depends on weather and on surface roughness that can make ionization easier.

How Transmission Lines Lose Energy

transmission line design considerations

Overhead Power Line Materials and Safety

Overhead transmission lines rely on the right materials, insulation, and support hardware to move electricity safely and efficiently. Aluminum is now the preferred conductor material because it is abundant and cost-effective. Copper was used more often in the past, but aluminum has become the common choice for modern lines. The most widely used conductor is aluminum conductor, steel-reinforced, or ACSR. It uses aluminum strands around a steel core for added strength. Other conductor types...

resistance and conductance

Transmission lines lose energy through resistance and conductance. DC resistance depends on a conductor’s resistivity, length, and cross-sectional area. Resistivity is a material property, and annealed copper is the international standard used for measurement. Material choice and conductor shape both matter. Hard-drawn aluminum at 20 degrees Celsius has a resistivity equal to 61% of the standard conductivity of annealed copper. Stranded conductors also gain a little extra resistance because...

inductance: solid cylindrical conductor

Magnetic Flux Linkage in Solid Conductors

Magnetic flux linkage in a solid cylindrical conductor is found by combining the field inside the wire with the field around it. The method uses a 1-meter section of a non-magnetic conductor with radius r. It also assumes the current is spread uniformly and ignores end effects. Inside the conductor, Ampere's law is used to find the magnetic field intensity H. The field is concentric and constant within the conductor. From H, the magnetic flux density B inside the wire is calculated. The...

inductance: single-phase and three-phase line

inductance-single-phase-and-three-phase-line

Transmission Line Inductance in Power Cables

Transmission line inductance helps explain how current-carrying conductors behave in power systems. It is especially important when studying single-phase two-wire lines and three-phase three-wire lines with equal phase spacing. These line types are common models for efficient transmission design and operation. A single-phase line uses two solid cylindrical conductors, labeled x and y. Each conductor carries a phasor current, ix and iy, and the sum of these currents is zero. The total flux...

series impedances: three-phase line

Three-Phase Line Impedance Matrix

Three-phase line impedance matrix calculations describe how resistance and inductive reactance behave in an overhead power line. The model includes three phase conductors and multiple neutral conductors that are grounded at regular intervals. It also accounts for unbalanced phase currents, which can send return current through the neutral wires and the earth along the lowest-impedance path. Kirchhoff’s laws are used to build an integro-differential equation for the conductor network. To make...

capacitance: single-phase and three-phase line

capacitance-single-phase-and-three-phase-line

Transmission Line Capacitance in Power Systems

Transmission line capacitance affects how power lines store charge and behave in electrical power systems. It is an important part of line modeling because it helps describe efficient operation. For a single-phase line, the key idea is the charge on the conductors and the voltage between them. A single-phase transmission line uses two wires with equal spacing. One conductor carries a uniform positive charge, and the other carries an equal negative charge. From the voltage between the...

shunt admittances

Image Method for Line Capacitance

Image conductors help model line capacitance in transmission lines above Earth. A uniformly charged conductor induces an equal and opposite charge on the ground. This creates electric field lines between the conductor and the Earth. The method of images replaces the Earth with a matching conductor placed symmetrically below the line. The image conductor has the same radius and the same charge magnitude as the original conductor. That setup keeps the electric field and voltage above the Earth...

key terms and concepts

Explore how resistance and conductance affect transmission line energy loss, including temperature, skin effect, leakage current, and corona.

How Transmission Lines Lose Energy | 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

How Transmission Lines Lose Energy

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