The basic concept of Load on power system

1. Load on Power System
Introduction:
 The function of power station is to deliver power to a
large number of consumers.
 The load on a power station is never constant; rather it
varies from time to time.
 The power station must produce power as and when
demanded to meet the requirements of the consumers.
 Most of the complexities of modern power plant
operation arise from the inherent variability of the
load demanded by the users.
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY Load on Power System 1

2. EFFECTS OF VARIABLE LOAD
 Need of additional equipment:
- for variable supply of the fuel (water)
 Increase in production cost:
- variable load increases production cost
- efficiency of alternator decreases during light
load and it operates with max. efficiency near rated
speed.
- multiple generator of different capacity is used.
(increase initial cost/kW of plant capacity, floor space
>>> increase in production cost of
energy)
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3. Load Curve
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4. Load Curves
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY Load on Power System
Daily Load Curve:
The load variation during the whole day are recorded hourly
or half hourly and plotted against the time to get daily load
curve.
Monthly load curve :
Obtained by calculating the average value of power at a
particular time of the day from daily load curve.
Annual load curve:
Obtained from monthly load curve of a particular year by
calculating average value of power at a particular time of
the day.
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5. Information supplied by load curve
 It shows variation of load on the power station during different
hours of the day.
 Area under the curve represents the total number of units
generated in a day.
 Peak of the curve represents the maximum demand on the
station on that particular day.
 It helps in selecting the size and the number of generating units
in particular station.
 It helps in preparing the operation schedule of the station.
 The area under the load curve divided by the number of hours
represents the average load on the power station.
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6. Important terms and factors
 Connected load:
 It is the sum of continuous ratings of all the equipment connected
to supply system.
 Maximum demand:
 It is the greatest demand of load on the power station during a
given period.
 Demand factor:
 It is the ratio of maximum demand on the power station to its
connected load
 Average load:
 The average of loads occurring on the power station in a given
period (day or month or year) is known as average load or
average demand.
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AND TECHNOLOGY, TRICHY
Load on Power System 6

7. Important terms and factors
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY Load on Power System
Load factor:
The ratio of average load to the maximum demand during a given period is
known as load factor.
Diversity factor:
The ratio of the sum of individual maximum demands to the maximum
demand on power station is known as diversity factor.
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8. REFERENCES:
 Jeraldin Ahila M., “Power system operation and control”, Lakshmi
Publications, 2015.
 Kundur P., ‘Power System Stability and Control, Tata McGraw Hill
Education Pvt. Ltd., New Delhi,10th reprint, 2010.
 R3. Hadi Saadat, ‘Power System Analysis’, Tata McGraw Hill Education
Pvt. Ltd., New Delhi, 21st reprint, 2010.
 R4. Ramanathan V., “Power System Operation and Control,” Charulatha
Publications, 2015.
 R5. Gross C.A., “Power System Analysis,” Wiley India, 2011.
 Google and Wikipedia.
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