Name: transmission line inductance in power cables
Uploaded: 2024-11-21T14:54:23.000Z
Duration: 1 min 28 s
Channel: JoVE

Considerare le linee di trasmissione monofase a due fili e trifase a tre fili con spaziatura di fase uguale.
La linea monofase è costituita da due conduttori cilindrici solidi, x e y, ciascuno dei quali trasporta una corrente fasoriale.
Dato che la somma delle correnti è zero, viene calcolato il conduttore di collegamento del flusso totale x, seguito dalla sua induttanza.
Allo stesso modo, viene calcolato il conduttore di collegamento del flusso totale y e viene determinata la sua induttanza.
Viene quindi calcolata l'induttanza del circuito, nota anche come induttanza totale del circuito monofase.
Se i raggi di entrambi i conduttori sono uguali, l'induttanza totale del circuito può essere semplificata.
Ora, la linea trifase è costituita da tre conduttori cilindrici solidi, a, b e c, di uguale raggio e spaziatura di fase.
Assumendo correnti di sequenza positiva bilanciate tali che la somma delle correnti sia uguale a zero, viene calcolata la fase di collegamento del flusso totale di un conduttore.
Da questo, viene determinata la sua induttanza. A causa della simmetria, lo stesso risultato si applica alle fasi b e c.
Tuttavia, per il funzionamento bilanciato di questa linea, è necessario considerare solo una fase poiché i collegamenti di flusso di ciascuna fase hanno grandezze uguali e uno spostamento di 120 gradi.

parametri della linea di trasmissione 

Inductance: Single-Phase And Three-Phase Line

Induttanza: Linee monofase e Trifase

La comprensione dell'induttanza delle linee di trasmissione, è fondamentale per una progettazione e un funzionamento efficienti nei sistemi di energia elettrica. Questa discussione approfondisce le caratteristiche di induttanza delle linee di trasmissione monofase a due fili e trifase a tre fili, con uguale spaziatura di fase.

Linea Monofase a Due Fili:

Una linea monofase è composta da due conduttori cilindrici solidi, indicati come x e y. Ogni conduttore trasporta rispettivamente, correnti di fasore i_x​ e i_y​. Dato che la somma di queste correnti è zero, possiamo calcolare il flusso totale che collega il conduttore x. Questo collegamento di flusso è dato da:

<img alt="Equation1" src="/files/ftp_upload/16142/16142_Equation%201.svg" style="height: 32px;">

Dove r_x^’ è il raggio effettivo del conduttore x, che tiene conto dell’effetto di prossimità.

L'induttanza per conduttore, L_x del conduttore x, è quindi:

<img alt="Equation2" src="/files/ftp_upload/16142/16142_Equation%202.svg" style="height: 32px;">

Analogamente, per il conduttore y, vengono calcolati il ​​collegamento del flusso e l'induttanza. L'induttanza totale del circuito monofase, nota anche come induttanza di loop, è:

<img alt="Equation3" src="/files/ftp_upload/16142/16142_Equation%203.svg" style="height: 46px;">

Linea Trifase a Tre Fili:

Per una linea trifase, ci sono tre conduttori cilindrici solidi, a, b e c, ciascuno con raggio r uguale e spaziatura di fase D uguale. Supponendo correnti di sequenza positiva bilanciate, il flusso totale che collega la fase a, è:

<img alt="Equation4" src="/files/ftp_upload/16142/16142_Equation%204.svg" style="height: 32px;">

Da ciò si ricava l'induttanza della fase a:

<img alt="Equation5" src="/files/ftp_upload/16142/16142_Equation%205.svg" style="height: 32px;">

A causa della simmetria, la stessa induttanza si applica alle fasi b e c. Per un funzionamento trifase bilanciato, è necessario considerare solo una fase, poiché i collegamenti di flusso di ciascuna fase, sono uguali in ampiezza e spostati di 120 gradi.

La comprensione di questi calcoli di induttanza aiuta nella progettazione e nell'analisi delle linee di trasmissione, garantendo perdite minime e prestazioni ottimali.

Parametri della Linea di Trasmissione 

Considerare le linee di trasmissione monofase a due fili e trifase a tre fili con spaziatura di fase uguale.
La linea monofase è composta da due solidi ...

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

Education

Didattica

JoVE Core

Electrical Engineering

Ingegneria elettrica

Unit 1

Unità 1

Transmission Line Parameters

Parametri della linea di trasmissione

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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 linking conductor x can then be found, and the effective radius rx' is used to account for proximity effect. From the flux linkage, the inductance per conductor, Lx, is obtained.

The same process applies to conductor y. Its flux linkage and inductance are calculated in the same way. The inductance of the full single-phase circuit is the loop inductance, which combines the two conductors into one circuit value.

A three-phase line uses three solid cylindrical conductors, a, b, and c. They have equal radius r and equal phase spacing D. For balanced positive-sequence currents, the flux linking phase a can be determined from the current pattern in the line. The inductance of phase a follows from that flux linkage.

Because the system is symmetric, phases b and c have the same inductance as phase a. In balanced three-phase operation, one phase is enough to analyze because all three phases have equal-magnitude flux linkages shifted by 120 degrees. These inductance results are useful for line design and analysis, where reducing losses and improving performance are important.

Transmission Line Inductance in Power Cables

transmission-line-inductance-in-power-cables

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

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...

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

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

Learn how inductance is calculated for single-phase two-wire and three-phase three-wire transmission lines, including flux linkage, loop inductance, and balanced phase behavior.

Transmission Line Inductance in Power Cables | 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

Transmission Line Inductance in Power Cables

Description

Transcript

Tags