ميظعلا الله قدص

5/1/2020

ميحرلا نمحرلا الله مسب

ىردص ىل حرشا بر رم ا ىل رسيو ىناسل نم ةدقع للحاو ىلوق اوهقفي

Prof. Dr. Magdi El-Saadawi 1

Electrical Power Systems (1)

Part II

2 nd Grade EE Students

5/1/2020 Prof. Dr. Magdi El-Saadawi 2

5/1/2020

Chapter 7

Fundamentals of Electrical loads

pp. 251-264

Prof. Dr. Magdi El-Saadawi 3

Generation

Power Plant Commercial/ Industrial Customer Urban Customers 500 kV Transmission Extra-High-Voltage Substation (500/230 kV)

Transmission System

Distribution Substation (69/12 kV) 69 kV Sub-transmission 230 kV Transmission

Distribution System (12kV)

Underground Cable Distribution Line Overhead Distribution Transformer Residential Customer 5/1/2020 Underground Distribution Transfomer Residential Customer Fig 1. Electrical Power System Prof. Dr. Magdi El-Saadawi High-Voltage Substation (230/69 kV) To Other High-Voltage Substations 4

Introduction

pp. 251



The function of a power station is to deliver power to a large number of consumers.



The load on a power station is never constant. It varies from time to time.



Electrical power cannot be stored and, therefore, the power station must produce power as and when demanded to meet the requirements of the consumers.



The power station should run at their rated capacity for maximum efficiency and on the other hand the demands of the consumers have wide variations.

This makes the design of a power station highly complex.

5/1/2020 Prof. Dr. Magdi El-Saadawi 5

7.1 Variable Load on Power Station pp. 251



In this chapter, we shall focus our attention on the problems of variable load on power stations. The load varies due to uncertain demands of the consumers.



Effects of variable load.



Need of additional equipment.



Increase in production cost.

5/1/2020 Prof. Dr. Magdi El-Saadawi 6

7.2 Load Curves pp. 253

• A curve showing the variation of load on the power station with w.r.t time.

• These load variations during the whole day (i.e. 24 hours) are recorded half-hourly or hourly and are plotted against time on the graph. • The curve thus obtained is known as

daily load curve

as it shows the variations of load w.r.t time during the day • There is also

monthly

and

yearly

Load Curves 5/1/2020 Prof. Dr. Magdi El-Saadawi 7

5/1/2020

Typical Daily Load curve

Prof. Dr. Magdi El-Saadawi 8

5/1/2020 Prof. Dr. Magdi El-Saadawi 9

5/1/2020 Prof. Dr. Magdi El-Saadawi 10

5/1/2020

Yearly Load Curve

Prof. Dr. Magdi El-Saadawi 11

Information attained from Load curves

– Variation of load during different hours of day – The area under the load curve gives the number of units generated in the day (

kWh

).

– Max. and Min. value s of daily load – Average annual load on the station

Average load = Area (in kWh) under daily load curve

5/1/2020

24 hours

Prof. Dr. Magdi El-Saadawi 12

Information attained from Load curves

•

Load factor = Average Load / Max. load

• The load curve helps in selecting the size number of generating units.

• The load curve helps in preparing the operation schedule of the station.

5/1/2020 Prof. Dr. Magdi El-Saadawi 13

7.3 Important Terms and Factors

pp 256

•

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.

Maximum demand is generally less than the connected load because all the consumers do not switch on their connected load to the system at a time.

5/1/2020 Prof. Dr. Magdi El-Saadawi 14

7.3 Important Terms and Factors

pp 256

•

Demand factor:

It is the ratio of maximum demand on the power station to its connected load

< 1

•

Average load (

Average demand

):

The average of loads occurring on the power station in a given period (day or month or year).

•

Load factor:

The ratio of average load to the maximum demand during a given period 5/1/2020 Prof. Dr. Magdi El-Saadawi 15

•

Load Factor

• Daily L.F.=

Average load / Max. demand

Monthly L.F. =

kWh supplied in a month Maximum demand * 24 * 30

Annual L.F. =

kWh supplied in a year Maximum demand * 8760

5/1/2020 Prof. Dr. Magdi El-Saadawi 16

•

Diversity of Load

ةدحاو ةينمز ةرتف ىف لمعت لا ةفلتخملا لامحلأا نأ ىنعي كلذ ىلإ عفدت تاسايس عبتت ءابرهكلا تاكرش نأ وأ •

Diversity Factor

The ratio of the sum of individual maximum demands to the maximum demand on power station

5/1/2020 Prof. Dr. Magdi El-Saadawi 17

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)

5/1/2020 Prof. Dr. Magdi El-Saadawi 18

•

Capacity Factor

• The ratio of actual energy produced to the maximum possible energy that could have been produced during a given period

.

Average demand on the Station Maximum Energy that could be produced

ةطحملا هجتنت نأ نكميام ىلإ ةطحملا اهتجتنأ ىتلا ةقاطلا نيب ةبسنلا

Average demand Plant Capacity

The capacity factor is an indication of the reserve capacity of the plant.

5/1/2020 Prof. Dr. Magdi El-Saadawi 19

?

What is the difference between load factor and capacity factor Can they have the same value?

5/1/2020 Prof. Dr. Magdi El-Saadawi 20

•

Plant use Factor

It is the ratio of kWh generated to the product of plant capacity and the number of hours for which the plant was in operation

Station output in kWh kW 1 *h 1 + kW 2 *h 2 + kW 3 *h 3 + …….

It Indicates how best the plant capacity has been utilized

مادختسلاا نع ثدحتي لماعملا اذه نأ : قباسلا لماعملا نيبو هنيب قرفلا ةطحملا ليغشت تايناكما نع ثدحتي قباسلاو ةطحملل ىقيقحلا

5/1/2020 Prof. Dr. Magdi El-Saadawi 21

?

What is the difference between Plant use Factor and Capacity factor Can they have the same value?

5/1/2020 Prof. Dr. Magdi El-Saadawi 22

7.4 Units Generated per Annum

pp.261

• •

Plant use Factor

Load factor = Average load Max. demand • • Average load = Max. demand x L. F. Units generated/annum = = Average load (in kW) x Hours in a year = Max. demand (in kW) x L.F. x 8760 5/1/2020 Prof. Dr. Magdi El-Saadawi 23

Load Duration Curve pp. 261

5/1/2020 Prof. Dr. Magdi El-Saadawi 24

Load Duration Curve pp. 261

5/1/2020 Prof. Dr. Magdi El-Saadawi 25

Load Duration Curve

5/1/2020 Prof. Dr. Magdi El-Saadawi 26

Load Curve and Load Duration Curve

5/1/2020 Prof. Dr. Magdi El-Saadawi 27

Points about load duration curve

pp 262

• The load duration curve gives the data in a more presentable form. • Area under daily load duration curve (in kWh) will give the units generated on that day. (same as load curve) • The duration curve can be extended to include any period of time  Daily load duration curve  Monthly load duration curve  Annual load duration curve 5/1/2020 Prof. Dr. Magdi El-Saadawi 28

Thank You Very Much And Any Question?

5/1/2020 Prof. Dr. Magdi El-Saadawi 30

•

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

5/1/2020 Prof. Dr. Magdi El-Saadawi 31

5/1/2020 Prof. Dr. Magdi El-Saadawi 32

5/1/2020 Prof. Dr. Magdi El-Saadawi 33

ىموكح لمحل ىحيضوت لكش

تاو وليكلاب لمحلا لثمي ىسأرلا روحملا

5/1/2020

تاعاسلاب نمزلا لثمي ىقفلأا روحملا

Difference between load curves of summer and winter 5/1/2020 Prof. Dr. Magdi El-Saadawi 35

Load Duration Curve pp. 60

5/1/2020 Prof. Dr. Magdi El-Saadawi 36

• Demand Factor:

the ratio between average load to the maximum connected load

• Power Station Maximum Demand:

decided) is the greatest average load on the station during a given period (15 min, 30 min or 1 hour as

5/1/2020 Prof. Dr. Magdi El-Saadawi 37

•

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

5/1/2020 Prof. Dr. Magdi El-Saadawi 38

?

Which is better and why

High or Low load factor value High or Low diversity factor value

5/1/2020 Prof. Dr. Magdi El-Saadawi 39

•

Plant Factor

Indicates how best the plant capacity has been utilized

Station output in kWh kW 1 *h 1 + kW 2 *h 2 + kW 3 *h 3 + …….

•

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

5/1/2020 Prof. Dr. Magdi El-Saadawi 40

• Connected Load Factor

Average kWh Connected load * 8760

5/1/2020 Prof. Dr. Magdi El-Saadawi 41

Load Duration Curve pp. 60

5/1/2020 Prof. Dr. Magdi El-Saadawi 42

Integrated Load Duration Curve pp. 60

5/1/2020 Prof. Dr. Magdi El-Saadawi 43

Integrated Load Duration Curve pp. 60

5/1/2020 Prof. Dr. Magdi El-Saadawi 44

•

Mass Curve

: pp. 62

represent the total kWh used by the load up to that hour of the day

•

Selection of units

pp.61

5/1/2020 Prof. Dr. Magdi El-Saadawi 45