load curve and related definitions

7/30/2019 Load Curve and Related Definitions

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The power station is constructed, comissioned and operated to supplyrequired power to consumerswith generators running at rated capacity formaximum efficiency.

we saw in lesson one that the fundamental problem in generation,transmission and distribution of electrical energy is the fact that electricalenergy can not be stored. It must be generated, transmitted and distributedas and when needed.

This lesson looks at problems associated with variable loads on powerstations, and discusses the complexities met in deciding the make, size andcapacity of Generators (Generating units) that must be installed in apower plant to successfully meet these varying energy demands on a dayto day basis.


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The load on a power station varies from time to time due to uncertaindemands of consumers. Energy demand of one consumer at any giventime is distinct/differs from the energy demand of another consumer. Thisresults in the total demand on the power station to vary over a given periodof time and may necesitate the following:

Additional equipment/Generating units to meet demand Increase in production cost to recuperate use of more material/equipment

In order to study the pattern and effect of the varying load, stationengineers use load curves.
http://en.wikipedia.org/wiki/Load_curvehttp://en.wikipedia.org/wiki/Load_curve


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Load curve

A load curve is a graph showing the variation of load on the power stationwith respect to time. the following load curves are used in power stations:

-- Load variations captured during the day ( 24Hrs ),recorded either half-hourly or hourly.

-- Load variations captured during the month atdifferent times of the day pltted aginst No. of days.

-- Load variations captured during the Year, this isderived from monthly load curves of a particular year.


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A load curve is a chart showing the amountof electrical energy customers use over the

course of time.


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The greatest demand of load on the power station during a given period.

The highest peak on the power station load curve.


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Ratio of maximum demand to connected load. this is usually less than .


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This is the average of loads occuring on the power station in a given period.


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Average of loads occuring on a power station in 1 day (24Hrs).

= total of units{in KWh}

24 hours


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Average of loads occuring on a power station in 1 month (24Hrs x No. ofdays).

= total of units{in KWh}

24 hours*days


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Average of loads occuring on a power station in 1 year (8760Hrs).= total of units{in KWh}

8760 hours


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The ratio of average load to maximum demand. typical less than 1. Thisis the measure of the effective use of the power station.

High LF = Low MD = Low plant capacity = Low cost per unit generated.


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The ratio of the sum of all individual maximum demands on the powerstation to the Maximum demand on the station. Consumer maximumdemands donot occur at the same time thus maximum demand on powerstation will always be less than the sum of individual demands.

High DF = Low MD = Low plant capacity = Low investment capitalrequired.


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The ratio of actual energy produced to the maximum possible energy thatcould have been produced on a given period.

This indicates the reserve capacity of a plant. From these we can see that:


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Area under load curve = Units generated

Highest point of the curve = MD

(Area under curve) (by total hours) = Average load (Area under load curve) (Area of rectangle containing load curve) = LF

Helps to select size & number of generating units.

Helps to create operating schedule of the power plant.


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The ratio of average load to maximum demand. typical less than 1. Thisis the measure of the effective use of the power station.

L.F = Output {in KWh}

Capacity installed*8760 hrs

High LF = Low MD = Low plant capacity = Low cost per unit generated.


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The ratio of the sum of all individual maximum demands on the powerstation to the Maximum demand on the station. Consumer maximumdemands donot occur at the same time thus maximum demand on powerstation will always be less than the sum of individual demands.

High DF = Low MD = Low plant capacity = Low investment capital

required.

load curve and related definitions

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