# Demand Factor-Diversity Factor-Utilization Factor-Load Factor _ EEP

November 27, 2016 | Author: Mahesh Madas | Category: N/A

#### Short Description

Demand Factor-Diversity Factor-Utilization Factor-Load Factor _ EEP...

#### Description

12/31/2014

D em em an and F ac actor -D -D iv iver si si ty ty F ac actor -U -U titi lili za zati on on F ac actor -L -Load Factor | EEP

Home  Tec  Technic hnical al Artic Articles les  Artic  Article le Cate Categorie goriess Contact us Subscribe to articles Subscribe to downloads El. Enginering Guides EE General guides Po wer Subs Substati tations ons Schneider Electric CTs Siemens Basics of EE  ABB Drive Drivess Guid Guides es Industry Automation Relay control/prot control/protection ection  Alternat  Alte rnative ive Ener Energy  gy  Electrical Software MS Excel Spreadsheets Spreadsheets Electrical Design Docs Engineering Resources  Vide o Lec  Video Lecture turess – Elec Electrica tricall Engi Enginee neering  ring  PLC Programming Training  Electric Testing and Maintenance (VIDEO) Network Theorems and Laws -

Demand Factor-Diversity Demand Factor-Diversity Factor-Utilization Factor-Load Factor   Elect ctr  r ical i cal Notes – Articles  Originally  published  publ ished at  Ele

(1) Demand factor  Demand Factor = Maximum demand of a system / Total connected load on the system Demand Demand factor is always less than one. Example: if a residence having 6000W equipment connected has a maximum demand dem and of  300W,Than demand factor = 6000W / 3300W = 55%. The lower the demand factor, the less system capacity required to serve the connected load. Feeder-circuit  conductors should have an ampere sufficient to carry the load; the ampere of the feeder-circuit need not always be equal to the total of all loads on all branch-circuits connected to it. Remember that the demand factor permits a feeder-circuit ampere to be less than 100% of the sum of all branch-circuit loads connected to the feeder.

http://el ec ectr ic ical -e -engi ne neer in ing- po por ta tal .c .com /d /dem an and- fa factor -d -di ve ver si si ty ty- fa factor -u -uti lili za zati on on- fa factor -l -l oa oad- fa factor

1/15

12/31/2014

D em and F actor -D iver si ty F actor -U ti li zati on F actor -Load Factor | EEP

Example: One Machine Shop has Fluorescent fixtures=1 No, 5kw each, Receptacle outlets =1 No, 1500w each. Lathe=1No, 10 Hp, Air Compressor=1 No, 20 Hp, Fire Pump=1 No, 15 Hp.

After questioning the customer about the various loads, the information is further deciphered as follows: 1. The shop lights are on only during the hours of 8 a.m. to 5 p.m. 2. The receptacle outlets are in the office only, and will have computers and other small loads plugged into them. 3. The lathe is fully loaded for 5 minutes periods. The rest of the time is setup time. This procedure repeats every 15 minutes. 4. The air compressor supplies air to air tools and cycles off and on about half the time. 5. The fire pump only runs for 30 minutes when tested which is once a month after hours.

Calculation:

Lighting  Demand Factor = Demand Interval Factor x Diversity Factor. = (15 minute run time/ 15 minutes) x 1.0 = 1.0 Lighting Demand Load = 5 kW x 1.0 = 5 kW Receptacle Outlet Demand Factor = Demand Interval Factor x Diversity Factor = (15 minute run time / 15 minutes) x 0.1 = 0.1 Receptacle Outlet Demand Load = 15 x 1500 watts x 0.1 = 2.25 kW Lathe Demand Factor = Demand Interval Factor x Diversity Factor. = (5 minute run time / 15 minutes) x 1.0 =0 .33 Lathe Demand Load = 10 hp x .746 x .33 = 2.46 kW  Air Compressor Demand Factor = Demand Interval Factor x Diversity Factor. = (7.5 minute run time / 15 minutes) x 1.0 = 0.5  Air Compressor Demand Load = 20 hp x .746 x .5 = 7.46 kW Fire Pump Demand Factor = Demand Interval Factor x Diversity Factor. = (15 minute run time/ 15 minutes) x 0.0 = 0.0 Fire Pump Demand Load = 15 hp x .746 x 0.0 = 0.0 kW Summary of Demand Loads :

http://el ectr ical -engi neer ing- por tal .com /dem and- factor -di ver si ty- factor -uti li zati on- factor -l oad- factor

2/15

12/31/2014

D em and F actor -D iver si ty F actor -U ti li zati on F actor -Load Factor | EEP

Equipment

kW

D.F.

Demand KW

Lighting

5

1

5

Receptacle Outlets

22.5

.1

2.25

Lathe

7.5

.33

2.46

Air Compressor

15

0.5

7.46

Fire Pump

11.25

0.0

0.0

TOTAL

61.25 Kw

17.17 Kw

(2) Diversity factor / simultaneity factor (Ks) Diversity Factor = Sum of Individual Max. Demand. / Max. Demand on Power Station.

3/15

12/31/2014

D em and F actor -D iver si ty F actor -U ti li zati on F actor -Load Factor | EEP

The feeder peak turns out to be 20 kw. The diversity is then 20/25 or 0.8. This results from the timing differences between the individual heating/cooling, appliance usages in the individual customers.  As supply availability decreases, the diversity factor will tend to increase toward 1.00. This can be demonstrated when restoring service after outages (called “cold starts”) as the system initial surge can be much greater than the historical peak loads. Example-II:  A sub-station has three outgoing feeders: 1. 2. 3. 4.

feeder 1 has maximum demand 10 feeder 2 has maximum demand 12 feeder 3 has maximum demand 15 While the maximum demand of all

MW at 10:00 am, MW at 7:00 pm and MW at 9:00 pm, three feeders is 33 MW at 8:00 pm.

Here, the sum of the maximum demand of the individual sub-systems (feeders) is 10 + 12 + 15 = 37 MW, while the system maximum demand is 33 MW. The diversity factor is 37/33 = 1.12.  The diversity factor is usually greater than 1; its value also can be 1 which indicates the maximum  demand of the individual sub-system occurs simultaneously. Diversity is the relationship between the rated full loads of the equipment downstream of a connection point, and the rated load of the connection point. To illustrate: 1. The building at these co-ordinates is fitted with a 100A main supply fuse. 2. The distribution board has 2no. 6A breakers, 1no. 20A breaker and 5no. 32A breakers, a total, potentially, of 192A. Not all these rated loads are turned on at once. If they were, then the 100A supply fuse would rupture, as it cannot pass 192A. So the diversity factor of the distribution board can be said to be 192A/100A, or 1.92, or 52%. Many designers prefer to use unity as the diversity factor in calculations for planning  conservatism because of plant load growth uncertainties. Local experience can justify using a diversity factor larger than unity, and smaller service entrance conductors and transformer requirements chosen accordingly.  The diversity factor for all other installations will be different, and would be based upon a local evaluation of the loads to be applied at different moments in time. Assuming it to be 1.0 may, on some occasions, result in a supply feeder and equipment rating that is rather larger than the local installation warrants, and an over-investment in cable and equipment to handle the rated load current. It is better to evaluate the pattern of usage of the loads and calculate an acceptable diversity factor for each particular case. In the case of the example given above, achieving a diversity of 1.0 or 100% would require well over twice the cross-sectional area of copper cable to be installed in a deep trench underneath a field, the rebuild of a feeder cabinet to larger dimensions, more substantial overhead supply  cables for a distance exceeding 2km northwards and a different tariff, where one pays rather more for a kWh than at present. The investment required to achieve 1.0 simply isn’t justifiable in http://el ectr ical -engi neer ing- por tal .com /dem and- factor -di ver si ty- factor -uti li zati on- factor -l oad- factor

4/15

12/31/2014

D em and F actor -D iver si ty F actor -U ti li zati on F actor -Load Factor | EEP

this particular case. Diversity factor is mostly used for distribution feeder size and transformer as well as to determine the maximum peak load and diversity factor is always based on knowing the process.  You have to understand what will be on or off at a given time for different buildings and this  will size the feeder. Note for typical buildings diversity factor is always one. You have to estimate or have a data records to create 24 hours load graph and you can determine the maximum demand load for node then you can easily determine the feeder and transformer size.  The diversity factor of a feeder would be the sum of the maximum demands of the individual consumers divided by the maximum demand of the feeder. In the same manner, it is possible to compute the diversity factor on a substation, a transmission line or a whole utility system.  The residential load has the highest diversity factor. Industrial loads have low diversity factors usually of 1.4, street light practically unity and other loads vary between these limits.

Diversity Factor in distribution Network

Diversity Factors Elements of System Residential

Commercial

General Power

Large Industrial

Between individual users

2.00

1.46

1.45

Between transformers

1.30

1.30

1.35

1.05

Between feeders

1.15

1.15

1.15

1.05

Between substations

1.10

1.10

1.10

1.10

From users to transformers

2.00

1.46

1.44

From users to feeder

2.60

1.90

1.95

1.15

From users to substation

3.00

2.18

2.24

1.32

From users to generating station

3.29

2.40

2.46

1.45

Diversity Factor for distribution switchboards

http://el ectr ical -engi neer ing- por tal .com /dem and- factor -di ver si ty- factor -uti li zati on- factor -l oad- factor

5/15

12/31/2014

D em and F actor -D iver si ty F actor -U ti li zati on F actor -Load Factor | EEP

Number of circuits

Diversity Factor (ks)

Assemblies entirely tested 2 and 3

0.9

4 and 5

0.8

6 to 9

0.7

10 and more

0.6

Assemblies partially tested in every case choose

1

Diversity Factor for according to circuit function (IEC 60439) Circuits Function

Diversity Factor (ks)

Lighting

0.9

Heating and air conditioning

0.8

Socket-outlets

0.7

Lifts and catering hoist For the most powerful motor

1

For the second most powerful motor

0.75

For all motors

0.8

Diversity Factor for an apartment block

http://el ectr ical -engi neer ing- por tal .com /dem and- factor -di ver si ty- factor -uti li zati on- factor -l oad- factor

6/15

12/31/2014

D em and F actor -D iver si ty F actor -U ti li zati on F actor -Load Factor | EEP

Apartment

Diversity Factor (ks)

2 To 4

1

5To 19

0.78

10To 14

0.63

15To 19

0.53

20To 24

0.49

25To 29

0.46

30 To 34

0.44

35 To 39

0.42

40To 40

0.41

50 To Above

0.40

Example: 5 storey apartment building with 25 consumers, each having 6 kVA of installed load.  The total installed load for the building is: 36 + 24 + 30 + 36 + 24 = 150 kVA  The apparent-power supply required for the building is: 150 x 0.46 = 69 kVA It is a matter of common experience that the simultaneous operation of all installed loads of a given installation never occurs in practice, i.e. there is always some degree of diversity and this fact is taken into account for estimating purposes by the use of a simultaneity factor / Diversity  Factor (ks).  The Diversity factor ks is applied to each group of loads (e.g. being supplied from a distribution or sub-distribution board). The determination of these factors is the responsibility of the designer, since it requires a detailed knowledge of the installation and the conditions in which the individual circuits are to be exploited. For this reason, it is not possible to give precise values for general application.   Designing Size of Electrical Switchgear by use of Demand Factor and Diversity Factor:

Diversity factors are used by utilities for distribution transformer sizing and load predictions. Demand factors are more conservative and are used by NEC for service and feeder sizing. Demand factors and diversity factors are used in design. For example, the sum of the connected loads supplied by a feeder is multiplied by the demand factor to determine the load for which the feeder must be sized. This load is termed the maximum demand of the feeder. The sum of the maximum demand loads for a number of sub feeders divided by the diversity factor for the sub feeders will give the maximum demand load to be supplied by the feeder from which the sub feeders are derived. http://el ectr ical -engi neer ing- por tal .com /dem and- factor -di ver si ty- factor -uti li zati on- factor -l oad- factor

7/15

12/31/2014

D em and F actor -D iver si ty F actor -U ti li zati on F actor -Load Factor | EEP

Example-1:  Suppose We have four individual feeder-circuits with connected loads of 250 kVA, 200 kVA, 150 kVA and 400 kVA and demand factors of 90%, 80%, 75% and 85% respectively.Use a diversity factor of 1.5. Calculating demand for feeder-circuits 250 kVA x 90% = 225 kVA 200 kVA x 80% = 160 kVA 150 kVA x 75% = 112.5 kVA 400 kVA x 85% = 340 kVA 837.5 kVA  The sum of the individual demands is equal to 837.5 kVA. If the main feeder-circuit were sized at unity diversity: kVA = 837.5 kVA ÷ 1.00 = 837.5 kVA.  The main feeder-circuit would have to be supplied by an 850 kVA   transformer. However, using the diversity factor of 1.5, the kVA = 837.5 kVA ÷ 1.5 = 558 kVA for the main feeder. For diversity factor of 1.5, a 600 kVA   transformer could be used. Example-2:  A conveyor belt made up of six sections, each driven by a 2 kW motor. As material is transported along this belt, it is first carried by section 1, and then each section in succession until the final section is reached. In this simple example only one section of  conveyor is carrying material at any point in time. Therefore five motors are only handling  no-load mechanical losses (say .1 kW) keeping the belts moving whilst one motor is handling the load (say 1 kW). The demand presented by each motor when it is carrying its load is 1 kW, the sum of the demand loads is 6 kW but the maximum load presented by  the system at any time is only 1.5 kW. Diversity factor =Sum of Individual Max. Demand / Max. Demand = 6 Kw / 1.5 Kw =4. Demand Factor = Maximum demand / Total connected load = 1.5 Kw / 12 Kw = 0.125.

8/15

12/31/2014

D em and F actor -D iver si ty F actor -U ti li zati on F actor -Load Factor | EEP

A high load factor means power usage is relatively constant. Low load factor shows that occasionally a high demand is set. To service that peak, capacity is sitting idle for long periods, thereby imposing higher costs on the system. Electrical rates are designed so that customers with high load factor are charged less overall per kWh. For Example Customer A – High Load Factor 82% load factor = (3000 kWh per month x 100%) / 5 kW x 730 hours/month. Customer B – Low Load Factor 41% load factor = (3000 kWh per month x 100%) / 10kW x 730 hours/month.  To encourage the efficient use of installed capacity, electricity rates are structured so the price per kWh above a certain load factor is lower. The actual structure of the price blocks varies by rate.

(4) Utilization factor (Ku) In normal operating conditions the power consumption of a load is sometimes less than that indicated as its nominal power rating, a fairly common occurrence that justifies the application of  an utilization factor (ku) in the estimation of realistic values. Utilization Factor = The time that a equipment is in use./ The total time that it could be in use. Example:  The motor may only be used for eight hours a day, 50 weeks a year. The hours of  operation would then be 2000 hours, and the motor Utilization factor for a base of 8760 hours per year would be 2000/8760 = 22.83%. With a base of 2000 hours per year, the motor Utilization factor would be 100%. The bottom line is that the use factor is applied to get the correct number of hours that the motor is in use.  This factor must be applied to each individual load, with particular attention to electric motors,  which are very rarely operated at full load. In an industrial installation this factor may be estimated on an average at 0.75 for motors. For incandescent-lighting loads, the factor always equals 1. For socket-outlet circuits, the factors depend entirely on the type of appliances being supplied from the sockets concerned.

Maximum demand Maximum demand (often referred to as MD) is the largest current normally carried by circuits, switches and protective devices. It does not include the levels of current flowing under overload or short circuit conditions.  Assessment of maximum demand is sometimes straightforward. For example, the maximum demand of a 240 V single-phase 8 kW shower heater can be calculated by dividing the power (8 kW) by the voltage (240 V) to give a current of 33.3 A. This calculation assumes a power factor of unity, which is a reasonable assumption for such a purely resistive load. http://el ectr ical -engi neer ing- por tal .com /dem and- factor -di ver si ty- factor -uti li zati on- factor -l oad- factor

9/15

12/31/2014

D em and F actor -D iver si ty F actor -U ti li zati on F actor -Load Factor | EEP

There are times, however, when assessment of maximum demand is less obvious. For example, if  a ring circuit feeds fifteen 13 A sockets, the maximum demand clearly should not be 15 x 13 = 195 A, if only because the circuit protection will not be rated at more than 32 A. Some 13 A sockets may feed table lamps with 60 W lamps fitted, whilst others may feed 3 kW washing  machines; others again may not be loaded at all. Lighting circuits pose a special problem when determining MD. Each lamp-holder must be assumed to carry the current required by the connected load, subject to a minimum loading of  100 W per lamp holder (a demand of 0.42 A per lamp holder at 240 V). Discharge lamps are particularly difficult to assess, and current cannot be calculated simply by dividing lamp power by  supply voltage. The reasons for this are: 1. Control gear losses result in additional current, 2. the power factor is usually less than unity so current is greater, and 3. Chokes and other control gear usually distort the waveform of the current so that it contains harmonics which are additional to the fundamental supply current. So long as the power factor of a discharge lighting circuit is not less than 0.85, the current demand for the circuit can be calculated from: current (A) = (lamp power (W) x 1.8) / supply voltage (V) For example, the steady state current demand of a 240 V circuit supplying ten 65 W fluorescent lamps would be: I = 10X65X1.8A / 240 = 4.88A Switches for circuits feeding discharge lamps must be rated at twice the current they are required to carry, unless they have been specially constructed to withstand the severe arcing resulting from the switching of such inductive and capacitive loads.

(5) Coincidence factor   The coincidence factor =Max. demand of a system / sum of the individual maximum demands  The coincidence factor is the reciprocal of the diversity factor

Demand Factor & Load Factor according to Type of Industries  Type of Industry

Demand Factor

Utilization Factor (DF x LF)

Arc Furnace

0.55

0.80

0.44

Induction Furnace

0.90

0.80

0.72

Steel Rolling mills

0.80

0.25

0.20

http://el ectr ical -engi neer ing- por tal .com /dem and- factor -di ver si ty- factor -uti li zati on- factor -l oad- factor

10/15

12/31/2014

D em and F actor -D iver si ty F actor -U ti li zati on F actor -Load Factor | EEP

Mechanical/ Electrical a) Single Shift

0.45

0.25

0.11

b) Double Shift

0.45

0.50

0.22

Cycle Industry

0.40

0.40

0.16

Wire products

0.35

0.40

0.14

Auto Parts

0.40

0.50

0.20

Forgings

0.50

0.35

0.17

a) Working Season

0.60

0.65

0.39

b) Non-Working Season

0.25

0.15

0.04

0.70

0.80

0.56

b) Non-Working Season 0.05

0.30

0.01

Cold Storage

Rice Sheller’s a) Working Season

Ice Candy Units a) Working Season

0.50

0.65

0.32

b) Non-Working Season

0.50

0.10

0.05

a) Working Season

0.80

0.65

0.52

b) Non-Working Season

0.80

0.10

0.08

a) Working Season

0.70

0.25

0.17

b) Non-Working Season

0.10

0.10

0.01

Spinning Mills

0.60

0.80

0.48

Textile Industry

0.50

0.80

0.40

Dyeing and Printing

0.40

0.50

0.20

Ghee Mills

0.50

0.50

0.25

Oil Mills

0.70

0.50

0.35

Solvent Extraction Mills

0.45

0.50

0.22

Ice Factories

Cotton Ginning

http://el ectr ical -engi neer ing- por tal .com /dem and- factor -di ver si ty- factor -uti li zati on- factor -l oad- factor

11/15

12/31/2014

D em and F actor -D iver si ty F actor -U ti li zati on F actor -Load Factor | EEP

Plastic

0.60

0.25

0.11

Soap

0.50

0.25

0.12

Rubber (Foot Wear)

0.45

0.35

0.16

Distilleries

0.35

0.50

0.17

Chemical Industry

0.40

0.50

0.20

Gas Plant Industry

0.70

0.50

0.35

Pain and Colour Factory

0.50

0.40

0.20

Sugar

0.30

0.45

0.13

Paper

0.50

0.80

0.40

Flour Mills(Single Shift)

0.80

0.25

0.20

Atta Chakies

0.50

0.25

0.12

Milk Plants

0.40

0.80

0.32

Printing Presses

0.35

0.30

0.10

Repair Workshops

0.40

0.25

0.10

Bottling Plants

0.40

0.35

0.14

0.55

.0.45

0.25

Telephone exchange

0.50

0.90

0.45

Public Water Works

0.75

0.40

0.30

Medical Colleges

0.60

0.25

0.15

Hospitals

0.25

0.90

0.22

Nursing Homes

0.50

0.50

0.25

Colleges and Schools

0.50

0.20

0.10

Hotels and Restaurants

0.75

0.40

0.30

Marriage Palaces

1.00

0.25

0.25

Demand Factor & Load Factor according to Type of Buildings: Individual Facilities

Demand Factor

http://el ectr ical -engi neer ing- por tal .com /dem and- factor -di ver si ty- factor -uti li zati on- factor -l oad- factor

12/15

12/31/2014

D em and F actor -D iver si ty F actor -U ti li zati on F actor -Load Factor | EEP

Communications – buildings

60-65

70-75

Telephone exchange building

55-70

20-25

Air passenger terminal building

65-80

28-32

Aircraft fire and rescue station

25-35

13-17

Aircraft line operations building

65-80

24-28

40-60

22-26

Applied instruction building

35-65

24-28

Chemistry and Toxicology  Laboratory

70-80

22-28

Materials Laboratory

30-35

27-32

Physics Laboratory

70-80

22-28

Electrical and electronics systems laboratory

20-30

3-7

Cold storage warehouse

70-75

20-25

General warehouse

75-80

23-28

Controlled humidity warehouse

60-65

33-38

Hazardous/flammable storehouse

75-80

20-25

Disposal, salvage, scrap building

35-40

25-20

Hospital

38-42

45-50

Laboratory

32-37

20-25

Dental Clinic

35-40

18-23

Medical Clinic

45-50

20-23

50-65

20-35

Single-family residential housing

60-70

10-15

Detached garages

40-50

2-4

Apartments

35-40

38-42

Fire station

25-35

13-17

Police station

48-53

20-25

Bakery

30-35

45-60

http://el ectr ical -engi neer ing- por tal .com /dem and- factor -di ver si ty- factor -uti li zati on- factor -l oad- factor

13/15

12/31/2014

D em and F actor -D iver si ty F actor -U ti li zati on F actor -Load Factor | EEP

Laundry/dry cleaning plant

30-35

20-25

K-6 schools

75-80

10-15

7-12 schools

65-70

12-17

Churches

65-70

5-25

Post Office

75-80

20-25

Retail store

65-70

25-32

Bank

75-80

20-25

Supermarket

55-60

25-30

Restaurant

45-75

15-25

Auto repair shop

40-60

15-20

Hobby shop, art/crafts

30-40

25-30

Bowling alley

70-75

10-15

Gymnasium

70-75

20-45

Skating rink

70-75

10-15

Indoor swimming pool

55-60

25-50

Theater

45-55

8-13

Library

75-80

30-35

Golf clubhouse

75-80

15-20

Museum

75-80

30-35

Recommended EE articles

About Author // ignesh Parmar jiguparmar  -  Jignesh Parmar has completed his B.E(Electrical) from Gujarat University. He is member of Institution of Engineers (MIE),India. Membership No:M-1473586.He has more than 12 years http://el ectr ical -engi neer ing- por tal .com /dem and- factor -di ver si ty- factor -uti li zati on- factor -l oad- factor

14/15

12/31/2014

D em and F actor -D iver si ty F actor -U ti li zati on F actor -Load Factor | EEP

experience in Transmission -Distribution-Electrical Energy theft detectionElectrical Maintenance-Electrical Projects (Planning-Designing-Technical Review-coordination -Execution). He is Presently associate with one of the leading business group as a Assistant Manager at Ahmedabad,India. He has published numbers of Technical Articles in "Electrical Mirror", "Electrical India", "Lighting India", "Industrial Electrix"(Australian Power Publications) Magazines. He is Freelancer Programmer of Advance Excel and design useful Excel base Electrical Programs as per IS, NEC, IEC,IEEE codes. He is  Technical Blogger and Familiar with English, Hindi, Gujarati, French languages. He wants to Share his experience & Knowledge and help technical enthusiasts to find suitable solutions and updating themselves on various Engineering Topics.