Load Prediction in Electrical Engineering: Connected Load, Maximum Demand, and Diversity, Lecture notes of Digital Electronics

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Estimation of Load

for Distribution

Systems

By

Muhammad Faizan Munir

Motivation for Load

Prediction/Estimation

You are in a POWER DISTRIBUTION COMPANY ….

You will have to perfectly estimate/predict the load

so that you must be able to tell those stats to the power generation company.

load requirements of an area depend on

following factors..

Population of the town or village under analysis

Standard of living of the people in that locality. (Rich/Moderate/low earned)

Cost of electricity (Tariff)

Industrial Development in that area

Nature of area (Land Conditions/Atmosphere)

Conditions for Load Estimations…

We can have two conditions when we are estimating the load…

You are predicting load requirements for a town/village/tower/industry which

is planned to be established.

You are estimating load requirements of an already developed sector. {updating

the data after each year}

You are predicting load requirements of an already developed but growing

area/city/sector.

Methods of load prediction

before we will explore in the methods of load prediction, some terms are need

to be clarified first…

I. Connected Load

II. Maximum Demand

III. Demand Factor

IV. Load Factor

V. Diversity Factor

VI. Load Curves (daily/monthly/annual)

Connected Load

“Connected load is the rating (in kilowatts) of the apparatus

installed on a consumer’s premises”

Each and every electrical equipment present in your house, either turned-on or

turned-off is included in connected load.

Demand Factor

“The ratio of maximum demand to the connected load is

called demand factor”

Work Example {A Residential Consumer}

(CASE#1)

A residential consumer has 10 lamps of 40 W each connected at his

premises. His demand is as follows:-

From 12 midnight to 5 a.m. ----- 40 W

From 5 a.m. midnight to 6 p.m. ----- No load

From 6 p.m. midnight to 7 p.m. ----- 320 W

From 7 p.m. midnight to 9 p.m. ----- 360 W

From 9 p.m. midnight to 12 midnight ----- 160 W

Plot the load curve. Find out his connected load , maximum demand,

average load, load factor, electric energy consumption during the day

(Problem to be solved in class)

Work Example {A Residential Consumer}

[V. IMP.]

• A curve showing the load demand of a consumer against time in hours of the day is

known as a load curve. This curve shows how the load varies with time.

• If the load curve is plotted for 24 hours of a single day, it is known as a daily load

curve.

• If it is considered for the whole year and plotted showing load demand of the

consumer against the time in hours of the year, it is known as annual load curve. This

type of curve is useful in predicting the annual requirements for energy, the

occurrence of the loads at different hours and days in a year

(Summer/Winter/Normal Season).

• As the load is variable, it will be at a maximum only for a certain time and will be less

for the remainder of the time, depending on the nature of variation.

• The average load during a period of 24 hours, or some other period (summer season

for example) considered for load curve, will be less than the maximum load.

Work Example {A Residential Consumer}

Load Factor

• (^) The average load during a period of 24 hours, or some other period (summer

season for example) considered for load curve, will be less than the maximum

load.

• (^) The ratio of average load to maximum load is called LOAD FACTOR.
• (^) The area under the load curve represents the energy consumption in kilowatt-

hours during the period. The load factor can also be defined as the ratio of

energy consumed during a given period to the energy which would have been

used if the maximum demand had been maintained throughout that period.

Important Points

• (^) A consumer has two needs

i. his maximum demand

ii. his energy consumption during a day.

we can only predict the time when a consumer will be requiring maximum

demand, but we cannot affix a certain time frame for the maximum demand to

occur.

Important Points

• (^) A consumer has two needs

i. his maximum demand

ii. his energy consumption during a day.

to supply these needs, it is necessary to provide generating capacity at least

equal to the maximum demand.

If the consumer used all this capacity through out the day, his load factor would

be 100% and he would make maximum use of the available energy. In this case,

the cost of electrical energy per kilowatt-hour would be minimum.

Important Points

• (^) A consumer has two needs

i. his maximum demand

ii. his energy consumption during a day.

to supply these needs, it is necessary to provide generating capacity at least

equal to the maximum demand.

If the consumer’s average load is not equal to his maximum load, his load

factor is less than 100% and the cost of electrical energy is higher than in the

last case.

THE IDEAL TO AIM AT therefore is a 100 % load factor, so that the equipment is

used to its full extent. This is, however, not possible in practice owing to variable

load characteristics.

Important Points

• (^) Smoothing out the load curve

when a number of consumers with different load requirements at different times

during the day are to be supplied, an attempt should be made to supply these

loads in such a way as to smooth out the load curve of the system and to obtain

as high a system load factor as practicable.

Lets consider the previous work example; load factor of the consumer is nearly

20 %. This means the energy used by the consumer is only about 20% of the

possible energy that could be supplied during the day by an installed capacity of

360 W if the maximum demand persisted uniformly throughout the day and the

load factor is 100 %.