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

Consider a balanced three-wire Y-to-Y circuit represented in the time domain, which can be transformed into a per-phase equivalent circuit.
First, the line current is determined, followed by the phase voltage at the load.
Then, the power delivered by the source is determined using the effective values of the sinusoidal phase voltage and line current.
Next, the power delivered to the load is calculated using the line current and the load resistance.
The power lost in the line is obtained using the line current and the line resistance.
Then, the total power delivered by the three-phase source, the total power received by the three-phase load, and the total power lost in the lines are determined.
A high percentage of power is lost in the line, which can be reduced by minimizing the line current.
However, this would reduce the load current, which would in turn decrease the power delivered to the load.
One way to reduce the line current without affecting the load current is to introduce transformers in the three-phase circuit.

line loss

The different configurations of source-load connections include wye (star) and delta connections. The relationship between line and phase voltages and currents varies depending on the configuration. When the source is supplying power, it is transmitted through the wires to the load, and during this transmission, some power is absorbed by the wires, leading to line loss.
Line loss impacts power delivery efficiency in a balanced three-phase circuit. The symmetry in such a circuit simplifies the analysis by allowing us to consider just one phase. The per-phase equivalent circuit aids in calculating various parameters, including line loss
Calculating Power Loss:
The power delivered to each phase of the load is the product of the square of the phase current and the phase load resistance.
Line Loss Computation:
Line loss for each wire is calculated by taking the square of the magnitude of the line current and multiplying it by the line&#39;s resistance.
For balanced three-phase systems, this calculation is multiplied by three (one for each phase) to get the total power loss. The resistance of the line is directly proportional to the material&#39;s resistivity and the length of the line, and inversely proportional to the cross-sectional area of the conductor. This means that line loss is directly proportional to the length of the conductor and inversely proportional to the conductor&#39;s cross-sectional area. Power companies use conductors with larger cross-sectional areas to minimize line losses and transmit power at higher voltages, which allows for lower current for the same amount of power. This is due to the power being the product of voltage and current, and for a given power level, increasing voltage allows for a decrease in current, reducing line losses.

Line Loss

Consider a balanced three-wire Y-to-Y circuit represented in the time domain, which can be transformed into a per-phase equivalent circuit.
First, the ...

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JoVE Core

Electrical Engineering

Unit 1

Three-Phase Circuits

KEY TERMS AND CONCEPTS

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

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the y-to-delta circuit

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the delta-to-delta circuit

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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

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

Single-Phase vs. Three-Phase Power Loss

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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...

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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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