Name: overhead power line materials and safety
Uploaded: 2024-11-21T14:54:23.000Z
Duration: 1 min 23 s
Channel: JoVE

L'alluminio, essendo abbondante ed economico, ha ampiamente sostituito il rame nelle linee di trasmissione aeree. Il popolare conduttore in alluminio rinforzato con acciaio è costituito da strati di trefoli di alluminio attorno a un nucleo in acciaio.
Altri tipi includono conduttori interamente in alluminio, interamente in lega di alluminio, conduttori in alluminio rinforzati con leghe e conduttori in acciaio rivestiti di alluminio. I conduttori in alluminio con supporto in acciaio e conduttori in alluminio ZT a fessura possono funzionare a temperature superiori a 150ºC. La progettazione elettrica per le linee di trasmissione considera il tipo di conduttore, le dimensioni, il numero di fasci per fase, la capacità termica, il controllo del gradiente di tensione, i dischi isolanti, il gioco e l'isolamento della linea. I fili di schermatura intercettano i fulmini e riducono la resistenza del basamento della torre.
Le linee di trasmissione che operano al di sopra dei 69 kV utilizzano isolanti del tipo a sospensione, tipicamente realizzati in porcellana, vetro temperato o dischi polimerici.
Le strutture che sostengono queste linee vanno dalle torri in acciaio a traliccio per le alte tensioni ai telai in legno per le tensioni più basse.
Il design meccanico garantisce stabilità, mentre le considerazioni ambientali tengono conto dell'uso del suolo e dell'impatto visivo.

considerazioni sulla progettazione della linea di trasmissione

Transmission Line Design Considerations

L'alluminio è diventato il materiale di scelta per le linee di trasmissione aeree, superando il rame grazie alla sua abbondanza e convenienza. Il tipo più diffuso è il conduttore in alluminio, rinforzato in acciaio (ACSR), che combina fili di alluminio attorno a un nucleo in acciaio. Altre varianti includono conduttori interamente in alluminio (AAC), conduttori interamente in lega di alluminio (AAAC), conduttori in alluminio rinforzati in lega (ACAR) e conduttori in acciaio rivestiti in alluminio. I design avanzati, come i conduttori in alluminio con supporto in acciaio e i conduttori in alluminio ZT di tipo gap, possono funzionare a temperature superiori a 150 gradi Celsius.

La progettazione elettrica delle linee di trasmissione, coinvolge diversi fattori critici. Questi includono il tipo e la dimensione del conduttore, il numero di fasci per fase e la capacità termica dei conduttori. Il controllo del gradiente di tensione, è essenziale per ridurre al minimo le perdite di energia. I dischi isolanti, che sono posizionati tra i conduttori e le strutture di supporto, sono utilizzati per garantire un isolamento adeguato. Una distanza adeguata e un isolamento della linea sono essenziali per la sicurezza e l'efficienza. I fili di schermatura sono posizionati strategicamente, intercettando i fulmini per ridurre la resistenza della base della torre e proteggere le linee di trasmissione.

Le linee di trasmissione che operano sopra i 69 kilovolt (kV), impiegano in genere isolatori di tipo sospeso, che consistono in stringhe di porcellana, vetro temperato o dischi polimerici. Le strutture di supporto variano in base ai livelli di tensione, con torri di acciaio reticolari autoportanti, utilizzate per le linee ad alta tensione e telai in legno per applicazioni a bassa tensione. I fili di schermatura, solitamente realizzati in acciaio ad alta resistenza o Alumoweld, proteggono dai fulmini e sono opportunamente messi a terra per garantire la sicurezza.

La progettazione meccanica assicura la resistenza e la durevolezza di conduttori, stringhe di isolanti e strutture di supporto. Anche le considerazioni ambientali sono cruciali, comprendendo l'uso del territorio e l'impatto visivo. L'obiettivo è di ottenere una progettazione di linea ottimale che soddisfi tutti i criteri tecnici riducendo al minimo i costi, considerando le spese di installazione e le perdite operative.

Considerazioni sulla Progettazione della Linea di Trasmissione

L'alluminio, essendo abbondante ed economico, ha ampiamente sostituito il rame nelle linee di trasmissione aeree. Il popolare conduttore in alluminio rinforzato con acciaio ...

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

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 include all-aluminum conductors, all-aluminum alloy conductors, aluminum conductor alloy-reinforced, and aluminum-clad steel conductors. Some advanced designs, such as aluminum conductors with steel support and gap-type ZT-aluminum conductors, can operate above 150 degrees Celsius.

Transmission line design also depends on electrical limits and line safety. Engineers choose the conductor type and size, the number of bundles per phase, and the thermal capacity of the conductors. Voltage gradient control helps reduce energy loss. Insulator discs sit between the conductors and the support structures. Proper clearance and line insulation are also important for safe and efficient operation.

Shield wires add another layer of protection. They are placed to intercept lightning strikes and reduce tower footing resistance. This helps protect the transmission line from damage. Lines above 69 kilovolts usually use suspension-type insulators made from porcelain, toughened glass, or polymer discs.

The support structure changes with voltage level. High-voltage lines often use self-supporting lattice steel towers, while lower-voltage lines may use wooden frames. Shield wires are usually made from high-strength steel or Alumoweld, and they are grounded for safety. Mechanical design must keep the conductors, insulator strings, and support structures strong and durable. Environmental factors also matter, including land use and visual impact. The best line design meets technical needs while keeping installation costs and operating losses as low as possible.

Overhead Power Line Materials and Safety

transmission line design considerations

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

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

Learn how aluminum conductors, insulators, shield wires, and tower designs keep overhead transmission lines efficient, durable, and safe.

Overhead Power Line Materials and Safety | 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

Overhead Power Line Materials and Safety

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