Load curve & load duration curve

Load Curve

• Load curve is plot of load in kilowatts versus time usually for a day or a year.

Definition

• The curve showing the variation of load on the power station with respect to time. The variation of load on the power station during different hours of the day.

• The area under the curve gives the number of units generated in the day. The maximum and minimum values of the daily load.

• The highest point on the load curve represents the maximum demand on the station on that day.

• The load curve helps in selecting the size and number of generating units.

• Information whether the installation is working efficiently or not. It helps in preparing the operation schedule of the station.

• The area under the load curve divided by the total numbers of hours (24 hours) gives the average load on the station.

Average Load = Area under daily load current/.24 hours

Types of Load Curve

• Daily load curve - Load variations during the whole day

• Monthly load curve - Load curve obtained from the daily load curve

• Yearly load curve - Load curve obtained from the monthly load curve

Daily load curve

• The curve drawn between the variations of load with reference to various time period of day is known as daily load curve.

Monthly load curve

• It is obtained from daily load curve. Average value of the power at a month for a different time periods are calculated and plotted in the graph which is known as monthly load curve.

Yearly load curve

• It is obtained from monthly load curve which is used to find annual load factor.

Base Load:

• The unvarying load which occurs almost the whole day on the station.

Peak Load:

• The various peak demands so load of the station.

Load duration curve:

• Load duration curve is the plot of load in kilowatts versus time duration for which it occurs. When the elements of a load curve are arranged in the order of descending magnitudes.

• The load duration curve gives the data in a more presentable form. The area under the load duration curve is equal to that of the corresponding load curve. The load duration curve can be extended to include any period of time.