Power System Operation and Control

Power System Operation and Control Load Variations and Load Characteristics, Load Curves, Load Duration Curves, Reserves, Load Forecasting and Unit Commitment

Introduction  Power

Station delivers power to large number of customers  Customer’s need (or load) is never constant  Electric Power cannot be stored and must be consumed upon production  At the same time, alternators give maximum efficiency at their rated capacity  Proper Load prediction and calculations are key to efficient design of power Station

Topics Covered Load

Curve. Daily Load Curve Interpretation. Few important terms and factors. Load Duration Curves. Base Loads, Peak loads. Reserves. Load Forecasting. Unit Commitment.

Variable Load 

Definition: The load on a power station varies from time to time due to uncertain demands of customers. This is known as Variable load on power station

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Effects of Variable Load: Need for additional Equipment  ◦ Eg: Equipment to handle raw materials during varying load conditions in thermal power station. Increase

in Production Cost 

◦ Eg: Alternators of different capacities must be installed to get maximum efficiency by operating at rated capacity.

Load Curves 

Definition: The curve showing variation of load on a power station w. ref. to time  

Daily Load Curve  Variation of load on a day plotted on an hourly basis Monthly Load Curve Variations of load in a month – Plotted using daily load curves  used to fix rates of

energy

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Yearly Load Cur ve  Extrapolated using monthly load curves  used to

determine annual Load Factor

Daily Load Curve Interpretation Shows variation of load on power station on a day 

Units generated in a day = Area (in kWh) under the daily load curve  Highest point on curve  Maximum demand on the station for the day Area (in kWh) under daily curve  Average Load on the station = 24 hrs 

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Load Factor =

Helps in

Average Load Max Demand

◦ Selecting Size and number of generating units ◦ Preparing operating schedule of the station

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Important Terms and Factors Connected Load : 

Sum of continuous rating of all equipments connected to supply system

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Maximum Demand : Greatest demand of Load on the power station

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Demand Factor =

during a given time

Maximum Demand ◦ usually