What is Demand factor?

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Examoogle · Accepted Answer

Ratio of maximum demand to the connected load

Explanation: The Demand Factor is a crucial parameter in electrical power system design, defined as the ratio of the maximum demand of a system or part of a system to the total connected load of the system. It indicates how much of the total installed equipment capacity is utilized at its peak during a specific time interval.

Working Principle: In any installation, not all appliances or loads are switched on simultaneously at their peak ratings. The demand factor accounts for this diversity of use. It helps engineers in sizing transformers, conductors, and protective devices efficiently by preventing over-dimensioning of infrastructure based on the mere sum of individual ratings.

Key Formulas: $DF = \frac{	ext{Maximum Demand}}{	ext{Connected Load}}$ — Definition of Demand Factor

Key Points: The value of the demand factor is always less than 1 (or 100%), as the maximum demand cannot exceed the connected load.; It is a dimensionless quantity often expressed as a decimal or a percentage.; Lower demand factors indicate higher diversity in electrical load usage patterns.

Advantages: Allows for economical sizing of electrical equipment.; Reduces capital expenditure by preventing unnecessary capacity installation.

Disadvantages: Requires accurate load estimation and historical data for effective application.; May lead to voltage drops or overloading if future load expansion is not accounted for.

Applications: Residential and commercial building load calculations.; Transformer and feeder sizing in power distribution networks.

Additional Info: Option A is incorrect as it is the reciprocal of the definition.. Option B represents the Load Factor, not the Demand Factor.. Option D relates to energy consumption characteristics over a specific period.

Answer: C is correct — The Demand Factor is mathematically defined as the ratio of maximum demand to the total connected load.

Exam Tip: Remember that Demand Factor is always $\le 1$, whereas Load Factor is the ratio of average load to peak demand over a duration. Do not confuse these two during competitive examinations!

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