8.10:
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 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.
8.10:
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'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'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'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.