Demand Factor Formula in Electrical Engineering

Demand factor is the ratio between maximum demand to the connected load on a power system.

The mathematical formula for Demand factor (DF) is:

DF = Maximum Demand/Connected load


Example: A power station has 5 MW load connected to it. While the maximum demand is 3 MW. Find the D.F.

Solution: DF = 3 MW/5 MW = 0.6

The demand factor is always smaller than 1 because the maximum demand on a station is always smaller than connected load.

Significance of Demand Factor

The demand factor is typically expressed as a percentage or decimal value. It represents the expected reduction in the maximum demand compared to the sum of individual loads operating simultaneously at their maximum capacities.

The concept of demand factor is crucial in determining the capacity requirements for electrical infrastructure, such as transformers, generators, and distribution networks. By considering the diversity and variation in load profiles, the demand factor helps avoid over-sizing equipment and optimizes system efficiency and reliability.

For example, in a residential neighbourhood, the total connected load might include various appliances, lighting, and other electrical devices. However, not all of them operate at their maximum capacity simultaneously. The demand factor accounts for this diversity by estimating the actual peak demand that is likely to occur based on historical data or engineering calculations.

The demand factor can vary depending on factors such as the type of load, time of day, season, and specific industry standards or regulations. It is an important consideration in power system planning, load management, and determining tariff structures for electricity consumption.

5 Example of Practical Applications of Demand Factor

Calculation of Demand Factor

Problem: Calculating demand factor from connected load and maximum demand value.

Statement: Let’s say you have a shop having a total connected load of 100 kW and a maximum demand of 70 kW.

Solution: To calculate the demand factor, you can use the formula: Demand Factor = Maximum Demand / Total Connected Load In this case, the demand factor would be 70 kW / 100 kW = 0.7 or 70%.

Finding Maximum Demand When Demand Factor is known

Scenario: If you know the demand factor and the total connected load, you can calculate the maximum demand.

Statement: If the demand factor is 0.8 and the total connected load is 200 kW

Solution: In this case maximum demand would be: Maximum Demand = Demand Factor * Total Connected Load Maximum Demand = 0.8 * 200 kW = 160 kW

Determining the Total Connected Load from Maximum Demand and Demand Factor

Scenario: In some cases, you may need to calculate the total connected load based on the maximum demand and the demand factor

Statement: If the maximum demand is 50 kW and the demand factor is 0.9, calculate total connected load

Solution: Here you can use the formula: Total Connected Load = Maximum Demand / Demand Factor Total Connected Load = 50 kW / 0.9 = 55.56 kW

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