Chapter 7
Fundamental of Electrical
Loads
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The Load Curve
• It gives the following information
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Variation of load during different hours of day
Max. and Min. value s of daily load
Average annual load of the station
Information whether the installations is
working efficiently or not
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‫شكل توضيحى لحمل حكومى‬
‫المحور الرأسى يمثل الحمل بالكيلو وات‬
‫المحور األفقى يمثل الزمن بالساعات‬
‫‪Prof. Magdi5El-Saadawi‬‬
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Difference between load curves of summer and winter
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Load Duration Curve
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Load Duration Curve
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Load Curve and Load Duration Curve
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• Average Demand: the ratio of kWh
delivered by the station in a particular
period divided by the hours in that period
• Load Factor
Monthly L.F. =
kWh supplied in a month
Maximum demand * 24 * 30
Annual L.F. =
kWh supplied in a year
Maximum demand * 8760
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• Diversity of Load
‫يعنى أن األحمال المختلفة ال تعمل فى فترة زمنية واحدة‬
‫أو أن شركات الكهرباء تتبع سياسات تدفع إلى ذلك‬
• Diversity Factor
the ratio of the sum of maximum demands
of the individual category to the maximum
demand of the power station
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Practical Example on Diversity Factor
Solution 1:
Transformer Size
(Assuming Diversity Factor of 1.0)
2,000 + 1,500 + 1,000 = 4,500 kVA
Solution 2:
Transformer Size
(Assume Diversity Factor of 1.2)
Choose 3,750 kVA
(4,500 kVA divided by 1.2 =
3,750 kVA)
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?
Which is better and why
High or Low load factor value
High or Low diversity factor value
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• Plant Factor
Indicates how best the plant capacity has been
utilized
Station output in kWh
kW1*h1 + kW2*h2 + kW3*h3 + …….
• Capacity Factor
is a value used to express the average percentage of full
capacity used over a given period of time.
Average demand on the Station
Maximum Installed Capacity of the Station
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• Connected Load Factor
Average kWh
Connected load * 8760
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Load Duration Curve
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