What does the area under the load curve represent?

Question

Examoogle · Accepted Answer

Energy consumed

Explanation: The load curve is a graphical representation of the electrical load on a power system plotted against time. The area under this curve represents the total energy supplied by the power station to the consumers over the given time period.

Working Principle: Since power $P$ is the rate of energy consumption and is defined as $P = \frac{dE}{dt}$, integrating the power with respect to time over a specific interval gives the total energy. Mathematically, the area is the integral of the load (kW) versus time (h), resulting in kilowatt-hours (kWh).

Key Formulas: $E = \int_{t_1}^{t_2} P(t) dt$ — represents energy as the integral of power over time; $Load Factor = \frac{Average Load}{Maximum Demand}$ — helps analyze the utilization efficiency of the station

Key Points: The ordinate of the load curve represents the load in kW or MW.; The abscissa represents time in hours.; The area under the load curve provides the total energy generated in kWh or MWh.; Load factor is derived from the load curve to measure the economy of the power plant.

Advantages: Helps in selecting the size and number of generating units.; Assists in calculating the operating cost of the power station.

Disadvantages: Does not explicitly provide information about the momentary peak current without voltage data.; Changes significantly based on daily, seasonal, and environmental conditions.

Applications: Determining the generation schedule of a power plant.; Designing the capacity of utility substations.

Additional Info: The load curve can be plotted on a daily, monthly, or annual basis.. Option A (System voltage) and Option B (Current) are instantaneous electrical parameters, not cumulative energy.. Option D (Maximum demand) is a single peak point on the curve, not the integral area.

Answer: C is correct — The area under the load curve, which plots power versus time, represents the total energy consumed (kWh) during that specific interval.

Exam Tip: Remember that while the load curve gives energy, the 'Load Duration Curve'—derived by arranging loads in descending order—is used specifically for determining the base load and peak load plant capacities.

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