Name: cutting heat loss in three-phase lines
Uploaded: 2024-07-08T13:19:58.000Z
Duration: 1 min 18 s
Channel: JoVE

Para minimizar las pérdidas de línea en circuitos trifásicos, se agregan dos transformadores: un transformador elevador en la fuente y un transformador reductor en la carga.
Sus relaciones de giro inversas garantizan una tensión y una corriente de carga constantes.
El voltaje secundario del transformador izquierdo es diez veces su voltaje primario, y la impedancia conectada al secundario del transformador derecho, vista desde el primario, se multiplica por un factor de 100.
Ahora, reemplazando el circuito con un circuito de una sola malla, la corriente de malla representa la corriente de línea.
La corriente que ingresa al extremo secundario del transformador izquierdo es igual a la corriente de línea negativa, mientras que en el primario es diez veces la corriente secundaria negativa.
De manera similar, la corriente que ingresa al extremo primario del transformador derecho es igual a la corriente de línea, mientras que en el extremo secundario es diez veces la corriente primaria.
Se determina el voltaje de fase en la carga, seguido del cálculo de la potencia entregada por la fuente y a la carga.
La estimación de la energía perdida en la línea revela que el 99,5 por ciento de la energía suministrada por la fuente llega a la carga, y solo el 0,5 por ciento se pierde en la línea.

reducir la pérdida de línea

En un circuito trifásico, la pérdida de línea es un indicador de la energía disipada en forma de calor debido a la resistencia de las líneas de transmisión. Para abordar esto, incorporar transformadores al sistema (un transformador elevador en la fuente y un transformador reductor en la carga) es una solución estratégica. Para mejorar esto se introducen dos transformadores trifásicos.

Con un transformador elevador en la fuente, el voltaje aumenta, reduciendo así la corriente en las líneas de transmisión, ya que la pérdida de potencia en las líneas de transmisión es proporcional al cuadrado de la corriente, esta reducción de la corriente conduce a una disminución de las pérdidas en la línea.

Cálculo de corriente de línea:

La corriente de línea se calcula dividiendo la carga reflejada por la impedancia (considerando la relación de vueltas del transformador) por el voltaje secundario del transformador.

La corriente de línea es:

<img alt="Equation 1" src="/files/ftp_upload/15136/15136_Equation_1.svg" style="height: 36px;">

<img alt="Equation 2" src="/files/ftp_upload/15136/15136_Equation_2.svg" style="height: 18px;">

Donde n es la relación de vueltas del transformador y Z_load es la impedancia de carga real en el lado secundario

Cálculo del voltaje de fase en la carga:

Si la relación de espiras primario a secundario del transformador se da como N_p:N_s, entonces el voltaje de fase en la carga se puede encontrar mediante:

<img alt="Equation 3" src="/files/ftp_upload/15136/15136_Equation_3.svg" style="height: 34px;">

dónde:

V_phase es el voltaje de fase en la carga,

V_primary es el voltaje de fase en el lado primario del transformador.

En un sistema trifásico Y a Y (estrella a estrella) con transformadores en ambos lados, el voltaje completo línea a línea en la carga se puede encontrar multiplicando el voltaje de fase por la raíz cuadrada de 3, debido a la cambio de fase entre voltajes de línea en una configuración Y:

<img alt="Equation 4" src="/files/ftp_upload/15136/15136_Equation_4.svg" style="height: 20px;">

La potencia real P entregada por la fuente en un sistema trifásico es:

<img alt="Equation 5" src="/files/ftp_upload/15136/15136_Equation_5.svg" style="height: 18px;">

Dónde:

P es la potencia real total entregada por la fuente.

V_L es el voltaje línea a línea.

I_L es la corriente de línea.

cos(θ) es el factor de potencia.

Reducir la pérdida de línea

Para minimizar las pérdidas de línea en circuitos trifásicos, se agregan dos transformadores: un transformador elevador en la fuente y un transformador reductor en la carga.
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Education

Educación

JoVE Core

Electrical Engineering

Ingeniería Eléctrica

Unit 1

Unidad 1

Three-Phase Circuits

Circuitos trifásicos

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

Reducing Line Loss

cutting heat loss in three-phase lines

Three-phase power systems can lose energy as heat in transmission lines because the wires have resistance. This line loss becomes important when electricity travels over a distance. A common solution is to use transformers to change the voltage and current in the system.

The setup uses two three-phase transformers. A step-up transformer is placed at the source, and a step-down transformer is placed at the load. Raising the voltage at the source lowers the current in the transmission lines, and that reduces line loss because power loss in the lines depends on the square of the current.

The line current can be found by dividing the reflected load impedance by the transformer secondary voltage. In this calculation, the turns ratio affects the load as it appears on the transformer side. The actual load impedance on the secondary side is represented as Z load, and n is the transformer's turns ratio.

The load phase voltage is found from the primary-to-secondary turns ratio, written as N p:N s. In a Y-to-Y, or star-to-star, three-phase system, the load line-to-line voltage is the phase voltage multiplied by sqrt 3. This factor comes from the phase shift between line voltages in a Y connection.

The real power delivered by the source is calculated with the three-phase power equation. It uses the line-to-line voltage, the line current, and the power factor, cos(theta). Together, these relationships show how transformer choice can help lower line loss while still delivering power to the load.

Cutting Heat Loss in Three-Phase Lines

three-phase circuits

How Three-Phase Power Delivers Electricity

Three-phase power is a major part of AC power distribution, especially where steady and efficient electricity delivery is needed. AC systems are grouped into single-phase, two-phase, and three-phase systems. These categories help describe how power moves from the source to the load. Single-phase circuits are common in homes. They usually use a two-wire system that connects one AC source to loads. These circuits can supply everyday appliances such as lamps, televisions, and microwaves at 120 V...

generation of three-phase voltage

Three-Phase AC Generator Windings

A three-phase AC generator uses rotating magnet windings and a stationary stator to make three-phase voltage. The rotor carries a magnet that spins inside the stator. The stator holds the three-phase winding, and mutual induction creates the voltage. The stator windings are spread evenly around the inside of the stator. They are placed 120 electrical degrees apart. These windings consist of three separate coils, or groups of coils, called phases. The phases can be connected in a Y, or star,...

three-phase voltages

Three-Phase Power Connections

Three-phase power connections use balanced voltages that are equal in magnitude and separated by 120 degrees. A three-phase generator produces these voltages, and the balance helps reduce power loss while keeping energy delivery steady to connected loads. Three-phase sources can be arranged in either wye or delta form. The loads connected to the system can also use wye or delta. This flexibility gives control over how the system is designed and managed. In a wye connection, one end of each...

the y-to-y circuit

Balanced Wye-to-Wye Neutral Current

A balanced wye-to-wye circuit uses three wye-connected sinusoidal voltage sources and three wye-connected loads. A neutral wire links the neutral node of the source to the neutral node of the load. The load impedance is connected across each phase of the load. The source and load can be connected in either a four-wire or a three-wire arrangement. A three-phase system is balanced when each phase has the same load. In that case, the current flow and phase angle are uniform across the system. If...

the y-to-delta circuit

Wye Source and Delta Load Currents

A balanced wye source and delta load form a common three-phase circuit with no neutral line connection. The source is Y-connected, and the load is delta-connected. To analyze the circuit, the first step is to assume a positive phase sequence. These phase voltages are then used to find the line voltages that appear across the delta load impedances. In the wye source, the phase voltages are V an, V bn, and V cn. In the delta load, the line voltages are V ab, V bc, and V ca. These line voltages...

the delta-to-delta circuit

Balanced Delta-Delta Power Circuit

A balanced delta-delta power circuit uses a delta-connected source and a delta-connected load. The two deltas form a closed loop that creates three separate phases. In this setup, the phase voltages are the same as the line voltages. If the source is in positive sequence, the phase voltages can be written directly, and no neutral wire is needed. The delta-connected load current is found by dividing the phase voltage by the impedance of each phase. For line current, Kirchhoff’s Current Law...

the delta-to-y circuit

Delta-Wye Source and Load Connections

A balanced delta-wye circuit connects a delta-connected source to a wye-connected load. In this setup, the phase voltage of the delta source equals the line voltage of the wye load. The source also sets the line currents that flow into the load. For a balanced system, the phase difference between currents makes it possible to find one line current from the other by using the positive sequence of phases. In the wye-connected load, each phase current equals the line current from the delta source.

power in a three-phase circuit

Balanced Three-Phase Power Calculation

Balanced three-phase power calculation depends on the wye and delta connections used in the circuit. A wye, or star, configuration can use three wires or four wires. A delta configuration connects the components in a closed loop. These connection types change how voltages and currents are arranged, but both are used in three-phase systems. In a balanced three-phase system, instantaneous power is the power at one exact moment. Even though the power in each phase changes over time, the total...

power distribution in three-phase and single phase circuits

power-distribution-in-three-phase-and-single-phase-circuits

Single-Phase vs. Three-Phase Power Loss

Single-phase and three-phase circuits distribute electrical power in different ways. Single-phase power is common in homes, while balanced three-phase power is widely used in industrial settings with heavy machinery. Both systems deliver energy, but their current flow and wire needs are not the same. A single-phase circuit usually uses a two-wire system. The current depends on the power absorbed by the load and the line voltage. Because wire loss from resistance follows the square of the...

line loss

Reducing Power Loss in Three-Phase Lines

Three-phase power lines can lose energy as electricity travels from the source to the load. This line loss affects how efficiently power reaches the load. In balanced three-phase circuits, the symmetry makes the analysis easier because one phase can represent the whole system. The source-load connection can use wye, also called star, or delta configurations. These setups change the relationship between line voltage, phase voltage, line current, and phase current. A per-phase equivalent circuit...

reducing line loss

Three-phase power systems can lose energy as heat in transmission lines because the wires have resistance. This line loss becomes important when electricity travels over a distance. A common solution is to use transformers to change the voltage and current in the system. The setup uses two three-phase transformers. A step-up transformer is placed at the source, and a step-down transformer is placed at the load. Raising the voltage at the source lowers the current in the transmission lines, and...

key terms and concepts

See how step-up and step-down three-phase transformers lower line loss by reducing current, and learn the key voltage, current, and power equations.

Cutting Heat Loss in Three-Phase Lines | 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

Cutting Heat Loss in Three-Phase Lines

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