calculation of diversity

1. Diversity Vs. Demand
Don’t Be Confused By These Terms
Published: March 2009
By James G. Stallcup
There are two terms that seem to confuse designers. These terms are “diversity factor” and “demand factor.” To
better understand the application of these terms when calculating the load for a service or a feeder supplying a
facility, one must understand their meaning.
Diversity factor is the ratio of the sum of the individual maximum demands of the various subdivisions of a system
(or part of a system) to the maximum demand of the whole system (or part of the system) under consideration.
Diversity is usually more than one.
Demand factor is the ratio of the sum of the maximum demand of a system (or part of a system) to the total
connected load on the system (or part of the system) under consideration. Demand factor is always less than one.
Application of diversity factor
Consider two facilities with the same maximum demand but that occur at different intervals of time. When supplied
by the same feeder, the demand on such is less the sum of the two demands. In electrical design, this condition is
known as diversity.
Diversity factors have been developed for main feeders supplying a number of feeders, and typically, they are 1.10
to 1.50 for lighting loads and 1.50 to 2.00 for power and lighting loads.
Diversity factor and load factor are closely related. For example, consider that a feeder supplies five users with the
following load conditions: On Monday, user one reaches a maximum demand of 100 amps; on Tuesday, two reaches
95 amps; on Wednesday, three reaches 85 amps; on Thursday, four reaches 75 amps; on Friday, five reaches 65
amps. The feeder’s maximum demand is 250 amps.
The diversity factor can be determined as follows:
Diversity factor = Sum of total demands ÷ Maximum demand on feeder = 420 ÷ 250 = 1.68 × 100 = 168%
Given
Calculate the size of a main feeder from substation switchgear that is supplying five feeders with connected loads of
400, 350, 300, 250 and 200 kilovolt-amperes (kVA) with demand factors of 95, 90, 85, 80 and 75 percent
respectively. Use a diversity factor of 1.5.
Solution
Calculate demand for each feeder:
400 kVA × 95% = 380 kVA •
350 kVA × 90% = 315 kVA •

2. 300 kVA × 85% = 255 kVA •
250 kVA × 80% = 200 kVA •
200 kVA × 75% = 150 kVA •
The sum of the individual demands is equal to 1,300 kVA •
If the feeder were sized at unity diversity, then 1,300 kVA ÷ 1.00 = 1,300 kVA
However, using the diversity factor of 1.5, the kVA = 1,300 kVA ÷ 1.5 = 866 kVA for the feeder. Transformer
supplying the main feeder plus wiring methods and equipment can be sized from this kilovolt-ampere rating.
Applying demand factors
Although feeder conductors should have an ampacity sufficient to carry the load, the ampacity needs not always be
equal to the total of all loads on connected branch-circuits.
A study of the National Electrical Code (NEC) will show that a demand factor may be applied to the total load.
Remember, the demand factor permits a feeder ampacity to be less than 100 percent of all the branch-circuit loads
connected to it.
Keep in mind that demand factor is a percentage by which the total connected load on a service or feeder is
multiplied to determine the greatest probable load it may be called on to carry.
When additional loads are connected to existing facilities having services and feeders as originally calculated per
220.87, the maximum kilovolt-ampere calculations in determining the load on existing services and feeders should
be used if these conditions are met:
If the maximum data for the demand in kVA, such as demand meter ratings, is available for a minimum of one year
•
If 125 percent of the demand ratings • for the period of one year added to the new load does not exceed the rating of
the service; where demand factors are used, often the load as calculated will probably be less than the demand meter
indications.
The Ex. to 220.87 contains requirements for where the maximum data for one year is not available. In such, the
calculated load is permitted to be based on the maximum demand (measure of average power demand over a 15-
minute period) continuously recorded over a minimum 30-day period using a recording ammeter connected to the
highest loaded ungrounded (phase) of the feeder or service based on the initial loading at the start of the recording.
By referencing Parts III and IV in the NEC, designers can find other useful demand factors that are applicable to
specific loads.
STALLCUP is the CEO of Grayboy Inc., which develops and authors publications for the electrical industry and
specializes in classroom training on the NEC and OSHA, as well as other standards. Contact him at 817.581.2206.
Diversity Factor in Electrical Wiring Installation
In a building, the whole load of Electrical Wiring installation doesn’t use at the same time. In
other words, we do not use all the loads at once at home i.e., we do not Switch ON all the fans,
light points, Air conditioner, TV, fridge, Water gazer, heater, Electric iron etc at once. Therefore,

3. keep in mind this (diversity factor) factor while selecting the proper and most suitable size of
cable for electrical wiring installation.
Diversity factor may e defined as:
Diversity Factor = Total Connected Load / Actual Maximum Load
Good to know:
 Diversity factor may neglect in case of final sub circuits.
 Instead of Homes and buildings, Diversity factor in electrical wiring installation may
neglect in offices or those places where all connected loads operate at once.
Example:
In a flat, the max demand of load current is follow (about 85 Amp)
Click image to enlarge
But with the help of using diversity factor, we found total load current about 52 A.
So in this case, use 52 A (+ 20% for future load = 62.4A) instead of 90A for calculation and
selection of proper size of cable for wiring.
What is load load factor and diversity factor? What is the significance
and what should be its value?
What is load shedding ? (For Power transmission & Distribution)
Best Answer
 sabyashachi b answered 7 years ago

Load factor (electrical) is the average power divided by the peak power over a period of time.n the
electricity industry, load factor is a measure of the output of a power plant compared to the maximum
output it could produce.
The two commonest definitions are:

4. * the ratio of average load to capacity
* the ratio of average load to peak load in a period.
Assuming the first definition, a higher load factor is better:
* A power plant may be less efficient at low load factors.
* A high load factor means fixed costs are spread over more kWh of output.
* A high load factor means greater total output.
Therefore a higher load factor usually means more output and a lower cost per unit, which means an
electricity generator can sell more electricity at a higher spark spread.
Diversity factor: The ratio of sum of the individual non-coincident maximum demands of various
subdivisions of the system to the maximum demand of the complete system. The diversity factor is
always less than or equal to 1. The (unofficial) term diversity, as distinguished from diversity factor
refers to the percent of time available that a machine, piece of equipment, or facility has its maximum
or nominal load or demand (i.e., a 70% diversity means that the device in question operates at its
nominal or maximum load level 70% of the time that it is connected and turned on).
Diversity factor is commonly used for a number of mathematics related topics. One such instance is
when completing a coordination study for a system. This diversity factor is used to estimate the load of a
particular node in the system.
Diversity Factor = Sum of Individual Max. Demands
———————————————————————————————
Max. Demand on Power Station
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Other Answers (2)
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
Moti answered 7 years ago

5. Load factor is defined as the ratio of Average load to maximum demand during a given period.It
can be calculated for a single day,for a month or for an year.Its value is always less than
one.B'coz maximum demand is always more than avg.demand.It is used for determining the
overall cost per unit generated.Higer the load factor,lesser will be the cost per unit.
Diversity factor-Ratio of sum of individual maximum demands to the maximum demand on
Power station.
Its value is always greater than one.(since the sum of individual max. demands
>Max.Demand)Greater the diversity factor,lesser is the cost of generation of power.
Load shedding means shedding/off of load during high load conditions.That is mainly during
peak hours.At this time almost all consumers are using electrical power.So to reduce the usage
of power,load shedding is done compulsary.
Source(s):
I'm an Electrical Engineer
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g.c. s answered 7 years ago
Load Factor
Actual output of a plant over a period of time
----------------------------------------...
Output which should have been as per the full capacity
of the plant over the same period of time
This is always equal to or less than 1
Diversity Factor
sum of the individual maximum demand of the various
divisions / subdivisions / areas of the system or plant
----------------------------------------...
maximum demand of the complete system
Diversity factor

6. The maximum demands of individual loads do not take place
at the same moment The sum of individual peaks is not used
as a measure of the maximumloaddemand The maximum
installed power is usually less than the sum of individual
maximum demands The diversity factor is greater than or
equal unity The ratio of sum of individual maximum demands
of all customers to the maximum demand for a specific
station is known as the diversity factor
Capacity factor
The capacity factor takes into account the excess of the
installed power of station more than the actual required
demand The excess of power is known as the reserve power,
which takes into account the expected future expansion and
unexpected sudden load increase The capacity factor is
defined as the ratio of the average load supplied by a station
to the rated
(installed) capacity of this station The capacity factor is less
than or equal unityMultiplying the average demand and the

7. rated capacity by time, the capacity factor can be defined as
the ratio between the actual energy produced and that would
be produced if the plant were operated at its full capacity
capacity factor = Annual energy(kWh)/rated capacity*no. of
operating hours
stimation of actual maximum kVA demand
General rules of electrical installation design
 Electrical installation design methodology
 Electrical installation rules, standards
o Definition of voltage ranges
o Electrical regulations and standards
o Quality and safety of an electrical installation
o Environmental directives
 Installed power loads - Characteristics
o Induction motors
o Resistive-type heating appliances and incandescent lamps (conventional or halogen)
o Fluorescent lamps
o Discharge lamps
o LED lamps & fixtures
 Power loading of an installation
o Installed power (kW)
o Installed apparent power (kVA)
o Estimation of actual maximum kVA demand
o Example of application of factors ku and ks
o Choice of transformer rating
o Choice of power-supply sources
Connection to the MV utility distribution network
Connection to the LV utility distribution network
MV and LV architecture selection guide
LV Distribution
Protection against electric shocks

8. Sizing and protection of conductors
LV switchgear: functions and selection
Overvoltage protection
Energy Efficiency in electrical distribution
Power Factor Correction
Power harmonics management
Characteristics of particular sources and loads
PhotoVoltaic (PV) installation
Residential and other special locations
ElectroMagnetic Compatibility (EMC)
Contents
 1- Factor of maximum utilization (ku)
 2- Diversity factor - Coincidence factor (ks)
 3- Diversity factor for an apartment block
 4- Rated Diversity Factor for distribution switchboards
 5- Diversity factor according to circuit function
All individual loads are not necessarily operating at full rated nominal power nor necessarily at
the same time. Factors ku and ks allow the determination of the maximum power and apparent-power
demands actually required to dimension the installation.
Factor of maximum utilization (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.
This factor must be applied to each individual load, with particular attention to electric motors,
which are very rarely operated at full load.

9. 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.
For Electric Vehicle the utilization factor will be systematically estimated to 1, as it takes a long
time to load completely the batteries (several hours) and a dedicated circuit feeding the charging
station or wall box will be required by standards.
Diversity factor - Coincidence factor (ks)
The determination of ks 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.
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 factor (ks).
This factor is defined in IEC60050 - International Electrotechnical Vocabulary,as follows:
 Coincidence factor: the ratio, expressed as a numerical value or as a percentage, of the
simultaneous maximum demand of a group of electrical appliances or consumers within a
specified period, to the sum of their individual maximum demands within the same period. As
per this definition, the value is always 1 and can be expressed as a percentage
 Diversity factor: the reciprocal of the coincidence factor. It means it will always be 1.
Note: In practice, the most commonly used term is the diversity factor, but it is used in
replacement of the coincidence factor, thus will be always <= 1. The term "simultaneity factor"
is another alternative that is sometimes used.
The factor ks is applied to each group of loads (e.g. being supplied from a distribution or sub-distribution
board).
The following tables are coming from local standards or guides, not from international standards.
They should only be used as examples of determination of such factors.

10. Diversity factor for an apartment block
Some typical values for this case are given in Figure A10, and are applicable to domestic
consumers without electrical heating, and supplied at 230/400 V (3-phase 4-wires). In the case of
consumers using electrical heat-storage units for space heating, a factor of 0.8 is recommended,
regardless of the number of consumers.
Number of downstream consumers Diversity factor (ks)
2 to 4 1
5 to 9 0.78
10 to 14 0.63
15 to 19 0.53
20 to 24 0.49
25 to 29 0.46
30 to 34 0.44
35 to 39 0.42
40 to 49 0.41
50 and more 0.38
Fig. A10: Example of diversity factors for an apartment block as defined in French standard
NFC14-100, and applicable for apartments without electrical heating
Example (see Fig. A11):
5 storeys 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
From Figure A10, it is possible to determine the magnitude of currents in different sections of
the common main feeder supplying all floors. For vertical rising mains fed at ground level, the
cross-sectional area of the conductors can evidently be progressively reduced from the lower
floors towards the upper floors.
These changes of conductor size are conventionally spaced by at least 3-floor intervals.
In the example, the current entering the rising main at ground level is:

11. the current entering the third floor is:
Fig. A11: Application of the diversity factor (ks) to an apartment block of 5 storeys

12. Rated Diversity Factor for distribution switchboards
The standards IEC61439-1 and 2 define in a similar way the Rated Diversity Factor for
distribution switchboards (in this case, always 1) IEC61439-2 also states that, in the absence
of an agreement between the assembly manufacturer (panel builder) and user concerning the
actual load currents (diversity factors), the assumed loading of the outgoing circuits of the
assembly or group of outgoing circuits may be based on the values in Fig. A12.
If the circuits are mainly for lighting loads, it is prudent to adopt ks values close to unity.
Type of load Assumed loading factor
Distribution - 2 and 3 circuits 0.9
Distribution - 4 and 5 circuits 0.8
Distribution - 6 to 9 circuits 0.7
Distribution - 10 or more circuits 0.6
Electric actuator 0.2
Motors 100 kW 0.8
Motors > 100 kW 1.0
Fig. A12: Rated diversity factor for distribution boards (cf IEC61439-2 table 101)
Diversity factor according to circuit function
ks factors which may be used for circuits supplying commonly-occurring loads, are shown in
Figure A13. It is provided in French practical guide UTE C 15-105.
Circuit function Diversity factor (ks)
Lighting 1
Heating and air conditioning 1
Socket-outlets 0.1 to 0.2 (1)

13. Lifts and catering hoist (2)
 For the most powerful motor
 For the second most powerful motor
 For all motors
1
0.75
0.60
(1) In certain cases, notably in industrial installations, this factor can be higher.
(2) The current to take into consideration is equal to the nominal current of the motor, increased
by a third of its starting current.
Fig. A13: Diversity factor according to circuit function (see UTE C 15-105 table AC)