Name: reducing power loss in three-phase lines
Uploaded: 2024-07-08T13:19:58.000Z
Duration: 1 min 10 s
Channel: JoVE

Рассмотрим сбалансированную трехпроводную цепь Y-to-Y, представленную во временной области, которая может быть преобразована в пофазную эквивалентную цепь.
Сначала определяется ток в сети, а затем фазное напряжение на нагрузке.
Затем мощность, подаваемая источником, определяется с использованием эффективных значений синусоидального фазного напряжения и линейного тока.
Затем мощность, подаваемая на нагрузку, рассчитывается с использованием линейного тока и сопротивления нагрузки.
Мощность, теряемая в линии, получается с помощью линейного тока и сопротивления линии.
Затем определяется общая мощность, выдаваемая трехфазным источником, общая мощность, получаемая трехфазной нагрузкой, и общая мощность, теряемая в линиях.
В линии теряется высокий процент мощности, который можно уменьшить, минимизировав ток в сети.
Однако это снизило бы ток нагрузки, что, в свою очередь, уменьшило бы мощность, подаваемую на нагрузку.
Одним из способов снижения тока в сети без влияния на ток нагрузки является введение трансформаторов в трехфазную цепь.

Потери на линии

Различные конфигурации соединений нагрузки источника включают соединения уай (звезда) и дельта (треугольник). Соотношение между линейными и фазными напряжениями и токами варьируется в зависимости от конфигурации. Когда источник подает мощность, она передается по проводам на нагрузку, и во время этой передачи часть мощности поглощается проводами, что приводит к потерям на линии.
Потери на линии влияют на эффективность подачи электроэнергии в сбалансированной трехфазной цепи. Симметрия такой схемы упрощает анализ, позволяя рассматривать только одну фазу. Пофазная эквивалентная схема помогает рассчитать различные параметры, включая потери на линии.
Расчет потерь мощности:
Мощность, подаваемая на каждую фазу нагрузки, представляет собой произведение квадрата фазного тока и сопротивления фазной нагрузки.
Расчет потерь в линии:
Потери на линии для каждого провода рассчитываются путем взятия квадрата величины тока линии и умножения его на сопротивление линии.
Для сбалансированных трехфазных систем этот расчет умножается на три (по одному на каждую фазу), чтобы получить общую потерю мощности. Сопротивление линии прямо пропорционально удельному сопротивлению материала и длине линии и обратно пропорционально площади поперечного сечения проводника. Это означает, что потери на линии прямо пропорциональны длине проводника и обратно пропорциональны площади поперечного сечения проводника. Энергетические компании используют проводники с большей площадью поперечного сечения, чтобы минимизировать потери на линии и передавать мощность при более высоких напряжениях, что позволяет снизить ток при той же мощности. Это связано с тем, что мощность равна произведению напряжения и тока, и для данного уровня мощности увеличение напряжения позволяет уменьшить ток, уменьшая потери на линии.

Рассмотрим сбалансированную трехпроводную цепь Y-to-Y, представленную во временной области, которая может быть преобразована в пофазную эквивалентную цепь.
Во-первых, ...

Education

JoVE Core

Electrical Engineering

Электротехника

Unit 1

Раздел 1

Three-Phase Circuits

Трехфазные цепи

KEY TERMS AND CONCEPTS

ОСНОВНЫЕ ТЕРМИНЫ И ПОНЯТИЯ

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 helps calculate the power delivered to the load and the power lost in the lines.

For each phase of the load, the delivered power depends on the square of the phase current and the phase load resistance. The power lost in one wire is found from the square of the line current multiplied by the resistance of that line. For a balanced three-phase system, the total line loss is three times the loss in one phase.

Line resistance depends on the material resistivity, the length of the conductor, and its cross-sectional area. As the line gets longer, resistance and line loss increase. A larger cross-sectional area lowers resistance and helps reduce loss. Power companies use larger conductors and higher transmission voltages to keep current lower for the same power level, which reduces line loss.

Reducing Power 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

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

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...

key terms and concepts

Learn how balanced three-phase circuits, wye and delta connections, and conductor size affect line loss, power delivery, and transmission efficiency.

Reducing Power 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

Reducing Power Loss in Three-Phase Lines

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