Load Factor Calculation with an Example:

Load factor calculation helps to improve the load factor. Load factor plays a key role in determining the overall cost per unit generated. The higher the load factor of the power station, the lesser will be the cost per unit generated.

Load Factor:

The ratio of average load to the maximum load during a given period is known as the load factor.

• Load factor = (Average load)/ (Maximum load)

The load factor is always less than one because the average load is smaller than the maximum load.

Average Load:

The average of loads occurring on the power station in a given period (day or month or year) is known as an average load.

• Daily Average load = (No of units generated per day)/ (24 hours)
• Monthly Average load = (No of units generated in a month)/ (No of hours in a
  month)
• Yearly Average load = (No of units generated in a year)/ (No of hours in a
  year)

Maximum Load/ Demand:

It is the greatest load of load on the power station during a given period.

Determining the Average Load:

1. The area under the load curve gives the total energy consumed in KWhr during the period.
2. The ratio of energy consumed to the total time is the average load on the system.
3. The Load factor can also be defined as the ratio of the energy consumed during a given period, to the energy which would have been consumed if the maximum demand had been maintained throughout that period.
4. Load factor = (Average load)/ (Maximum load)
5. Load factor = (Energy consumed during a period)/ (Maximum demand x time under consideration)

Load Factor Calculation Example-1:

• The connected load of a consumer is 2 KW and his maximum demand is 1.5 KW. The load factor of the consumer is?

Solution:

Load factor = (Average load)/ (Maximum load)

                        = 2/1.5=1.33

Load Factor Calculation Example-2:

• The maximum demand of a consumer is 2 KW and his daily energy consumption is 20 units. His load factor is?

Solution:

Load factor = (Energy consumed during a period)/ (Maximum demand x time under consideration)

= 20kWhr/2kWx24hr=0.416=41.6%

Load Curve:

The curve drawn between the variations of load on the power station with reference to time is known as the load curve.

There are three types of load curves namely the Daily load curve, Monthly load curve, and Yearly load curve.

Load factor calculation using different load curves:

i) Daily Load curve:

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

From the Daily load curve

Daily load factor= Daily Energy consumption / (Maximum demand * 24)

Hours in a day= 24

ii) Monthly Load curve:

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

From the monthly load curve

Monthly load factor= Monthly Energy consumption / (Maximum demand * 720)

Hours in a Month= 30*24=720

iii) Yearly Load curve:

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

From the annual load curve

Annual load factor= Annual Energy consumption / (Maximum demand * 8760)

Hours in a year= 365*24=8760

Load Factor Calculation Example-3:

• A consumer has a connected load of 12 lamps each of 100 W at his/ her premises. His/ her load demand is as follows:
  From midnight to 5 A.M.: 200 W.
  5 A.M. to 6 P.M.: No load.
  6 P.M. to 7 P.M.: 700 W.
  7 P.M. to 9 P.M.: 1,000 W.
  9 P.M. to midnight: 500 W.
  Draw the load curve and calculate the (i) Energy consumption during 24 hours,  (ii) Average load, (iii) Maximum demand, and (iv) Load factor

Solution:

For the given loads the daily load curve is as follows

i) Electrical energy consumption during the day = Area of load curve
= 200 × 5 + 700 × 1 + 1,000 × 2 + 500 × 3
= 5,200 Wh

 ii) Average load = Energy consumed during a Day/ 24 hours

=5200/24=216.7 W

iii) Maximum demand

= 1,000 W

iv) Load factor= (Average load)/ (Maximum load)

=216.7/1000

=0.2167

=21.67%

How to Improve Load Factor?

A consumer is characterized by his maximum demand and the energy consumed in KWhr. To supply the energy requirements of a consumer it is necessary to install a Power-plant, at first equal to his maximum demand.

If the consumer’s maximum demand equals his average load, his load factor is 100% and he makes use of the total installed capacity all the time. Therefore, the cost of energy would be minimum.

However, if the average load of the consumer is less than the maximum demand, the load factor is less than 100% and the cost of energy will be more.

The lower the load factor of the consumer, the higher will be the cost of energy. In actual practice, it is difficult to achieve a 100% load factor, because of the variable load characteristic.

Methods to Improve Load factor:

1. Shifting Energy usage away from peak times:

By controlling the peak demand the load factor can be improved. To lower the peak demand and hence load factor will be improved. Often loads are created by encouraging the consumers to use the electricity during off-peak times so that a load factor of approximately 100% is achieved.

2. Make the load curve flat:

Whenever a number of consumers are connected to a supply system, one tries to adjust the timings of these loads such that the load curve is smoothened and made flat.