During which time the demand of electrical energy is maximum?

Question

Examoogle · Accepted Answer

7 P.M. to 9 P.M.

Explanation: The maximum demand for electrical energy, commonly referred to as the 'peak load' or 'peak hour,' typically occurs between 7 P.M. and 9 P.M. This period corresponds to the evening when industrial activities often overlap with residential lighting, appliance usage, and commercial requirements, causing a surge in grid demand.

Working Principle: The load curve of a power system represents the variation of load on the station with respect to time. The peak demand occurs when domestic loads (lighting, heating, cooling, and entertainment) are superimposed on the residual industrial and commercial loads that remain active after the standard work shift, forcing the power plant to generate maximum power to maintain voltage stability.

Key Formulas: $Load Factor = \frac{Average Load}{Maximum Demand}$; $Demand Factor = \frac{Maximum Demand}{Connected Load}$

Key Points: Peak demand defines the sizing requirement for the capacity of a power station.; A higher load factor indicates more efficient utilization of the generating equipment.; Diversity factor plays a crucial role in predicting the actual maximum demand on the system.

Advantages: Predicting peak hours helps in effective load shedding management.; Optimizes the use of spinning reserves in thermal power stations.

Disadvantages: Higher peak demand necessitates larger capital investment for peak-load plants.; Increases grid frequency instability risks during the transition to peak hours.

Applications: Grid management and economic dispatch of power plants.; Tariff structuring for consumers (Time-of-Day metering).

Additional Info: The 'Base Load' is the minimum level of demand, whereas the 'Peak Load' is the maximum.. Option A (2 A.M. to 5 A.M.) represents the valley period where demand is at its minimum due to human sleep cycles.

Answer: D is correct — The peak demand occurs from 7 P.M. to 9 P.M. due to the simultaneous usage of lighting, residential appliances, and lingering commercial loads.

Exam Tip: Always remember that Load Factor is always less than 1; if your calculation yields a value > 1, the maximum demand was likely misidentified.

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