A load curve, also known as a chronological curve, is a graphical representation of the amount of power demand (measured in kW or MW) over a specific time period, typically in hours. It displays how the demand for power varies over time for a power station. When the load curve is plotted for a complete day, it’s known as a daily load curve, and when it’s plotted for a full year, it’s referred to as an annual load curve. The load curve is shown below
Information Provided by Load Curve
The information obtained from Load curves are given below
- Load duration curve: This indicates the variation in load at different times of the day.
- Peak load: The point on the curve where the load is at its highest, indicating the maximum demand on the power station.
- Total energy generated: The area under the load curve represents the total energy generated during the period being considered.
- Average load: Dividing the area under the curve by the total number of hours gives the average load.
- Load factor: The ratio of the area under the load curve to the total area of the rectangle in which it is contained gives the load factor. A higher load factor indicates a more uniform load pattern with fewer load variations. Ideally, the load curve would be flat, but in practice, it is often far from flat.
Utility of Load Curve
The load curve has several utilities, including:
- Determining the installed capacity of a power station based on the expected demand for power.
- Assisting in the selection of the most cost-effective sizes for various generating units.
- Estimating the generating costs based on the load curve.
- Deciding the operating schedules of the power station, including the sequence in which different generating units should be run.
Load Duration Curve
The load duration curve can be described as a graphical representation of the relationship between the load and time. It is plotted by arranging the load values in descending order, with the highest load on the left and progressively lower loads towards the right, culminating in the lowest loads at the far right end of the curve. The load duration curve is shown below
Some important points about Load duration curve are mentioned below
- The load duration curve (LDC) presents data in a more comprehensible manner. This graphical representation clearly shows the duration of time that a specific load has been present.
- The area beneath the LDC is equivalent to the area beneath the corresponding load curve. This means that the total energy generated can be determined by calculating the area under the daily load duration curve, measured in kilowatt-hours (kWh).
- The LDC can be extended to cover any time period. By dividing the horizontal axis from 0 to 8760 hours, a single curve can illustrate the variation and distribution of demand throughout an entire year. This particular curve is known as the annual load duration curve.