A
of-electrical
installation
design
B -- General
General rules
design
Regulations
Installed power
4 Power loading of an installation
B15
B - General design - Regulations Installed power
4 Power loading of an installation
A17
B15
In
In order
order to
to design
design an
an installation,
installation, the
the actual
actual maximum
maximum load
load demand
demand likely
likely to be
to
be imposed
the power-supply
system
be assessed.
imposed
on theonpower-supply
system
must must
be assessed.
To
To base
base the
the design
design simply
simply on
on the
the arithmetic
arithmetic sum
sum of
of all
all the
the loads
loads existing
existing in
in the
the
installation
installation would
would be
be extravagantly
extravagantly uneconomical,
uneconomical, and
and bad
bad engineering
engineering practice.
practice.
In order
to design
an installation,
the actual
maximumtaking
load demand
likely to diversity
be
The
The aim
aim of
of this
this chapter
chapter is
is to
to show
show how
how some
some factors
factors taking into
into account
account the
the diversity
imposed
on the power-supply
must beofassessed.
(non
simultaneous
operation of
ofsystem
all appliances
appliances
given group)
group) and
and utilization
utilization (e.g.
(e.g.
(nonsimultaneous
operation
all
of aa given
an
motor
is
generally
its
capability,
etc.)
To
base the
design
simply
on theoperated
arithmeticat
of all the
loads existing
in all
the
an electric
electric
motor
is not
not
generally
operated
atsum
its full-load
full-load
capability,
etc.) of
of
all existing
and be
projected
can
be assessed.
The
values
given
are
based
installation
extravagantly
uneconomical,
bad
engineering
practice.
existing
andwould
projected
loadsloads
can be
assessed.
Theand
values
given
are based
on
on
experience
records
taken
from
actual
installations.
In account
addition
to providing
experience
andand
on on
records
from
actual
installations.
addition
to providing
The
aim of this
chapter
is totaken
show
how
some
factors
takingIninto
the
diversity
basic
data
circuits,
the
basic installation-design
installation-design
dataofon
on
individual
circuits,
the results
results
will
provide
a global
(nonsimultaneous
operation
allindividual
appliances
of a given
group)will
andprovide
utilization
(e.g.
avalue
for is
the
installation,
from
which
requirements
of asystem
supply
forvalue
the
installation,
from which
the
requirements
of a
supply
anglobal
electric
motor
not
generally
operated
at the
its full-load
capability,
etc.) ofsystem
all
(distribution
or
set)
can
(distribution
network,
HV/LV
transformer,
or generating
generating
set)given
can be
be
specified.
existing
and network,
projectedMV/LV
loads transformer,
can be assessed.
The values
arespecified.
based on
experience and on records taken from actual installations. In addition to providing
basic installation-design data on individual circuits, the results will provide a global
value for the installation, from which the requirements of a supply system
4.1
Installed
(kW) or generating set) can be specified.
(distribution
network, power
HV/LV transformer,
The installed power is the sum of the nominal
powers of all power
consuming devices
devices in the
powerconsuming
in
the installation.
installation.
This is not the power to be actually supplied in
The
installed power is the sum of the nominal
in
practice.
practice.
powers of all powerconsuming devices in the
installation.
This is not the power to be actually supplied in
practice.
Most
Most electrical
electrical appliances
appliances and
and equipments
equipments are
are marked
marked to
to indicate
indicate their
their nominal
nominal
power
power rating
rating (Pn).
(Pn).
4.1
Installed
The
power
the
the
The installed
installed
power is
ispower
the sum
sum of
of(kW)
the nominal
nominal powers
powers of
of all
all power-consuming
power-consuming
devices
devices in
in the
the installation.
installation. This
This is
is not
not the
the power
power to
to be
be actually
actually supplied
supplied in
in practice.
practice.
This
the
for
motors,
where
rating
refers
the
output
This is
iselectrical
the case
caseappliances
for electric
electricand
motors,
where the
the
power
rating
refers to
to
thenominal
output power
Most
equipments
arepower
marked
to indicate
their
at
its driving
shaft.
input
will evidently
be greater.
power
at
its driving
shaft.
Thepower
input consumption
power consumption
will evidently
be greater
rating
(Pn). The
The
installed
power
is
the
sum
of
the
nominal
powers
of
all
power-consuming
Fluorescent
and
discharge
lamps
associated
with
stabilizing
ballasts,
Fluorescent and discharge lamps associated with stabilizing ballasts, are
are other
other
devices
the installation.
is not
the power
to be
actually
practice.
cases
which
the
power
indicated
on
lamp
is
than
cases in
inin
which
the nominal
nominalThis
power
indicated
on the
the
lamp
is less
lesssupplied
than the
theinpower
power
This
is the by
case
electric
where the power rating refers to the output
consumed
lamp
and
its
consumed
by the
thefor
lamp
and motors,
its ballast.
ballast.
power at of
its assessing
driving shaft.
The
input
power consumption
will evidently
be greater
Methods
the
actual
power
Methods of assessing the actual power consumption
consumption of
of motors
motors and
and lighting
lighting
Fluorescent
and
discharge
lamps
associated
with
stabilizing
ballasts,
are other
appliances
are
given
in
Section
3
of
this
Chapter.
appliances are given in Section 3 of this Chapter.
cases
in
which
the
nominal
power
indicated
on
the
lamp
is
less
than
the
power
The
The power
power demand
demand (kW)
(kW) is
is necessary
necessary to
to choose
choose the
the rated
rated power
power of
of aa generating
generating set
set
consumed
by the lampthe
and its ballast. of a prime mover have to be considered.
or
or battery,
battery, and
and where
where the requirements
requirements of a prime mover have to be considered.
Methods
of assessing
the actual
power consumptionor
of motors and
lighting
For
For aa power
power supply
supply from
from a
a LV
LV public-supply
public-supply network,
network, or through
through aa MV/LV
HV/LV transformer,
transformer,
appliances
are
given
in
Section
3
of
this
Chapter.
the
the significant
significant quantity
quantity is
is the
the apparent
apparent power
power in
in kVA.
kVA.
The power demand (kW) is necessary to choose the rated power of a generating set
or battery, and where the requirements of a prime mover have to be considered.
For a power supply from a LV public-supply network, or through a HV/LV transformer,
(kVA)
4.2
Installed
apparent
power
the significant
quantity
is the apparent
power in (kVA)
kVA.
The
The installed
installed apparent
apparent power
power is
is commonly
commonly assumed
assumed to
to be
be the
the arithmetical
arithmetical sum
sum of
of
kVA
individual
loads.
The
maximum
estimated
kVA
suppliedhowever
howeveris
thethe
kVA
of of
individual
loads.
The
maximum
estimated
kVA
totobebesupplied
4.2
Installed
apparent
is
equal
total
installed
kVA.power (kVA)
notnot
equal
to to
thethe
total
installed
kVA.
The
The apparent-power
apparent-power demand
demand of
of aa load
load (which
(which might
might be
be aa single
single appliance)
appliance) is
is
The
installed
power
is commonly
assumed
to be the arithmetical
sum for
of
obtained
from
its
power
rating
ifif necessary,
as
obtained
fromapparent
its nominal
nominal
power
rating (corrected
(corrected
necessary,
as noted
noted above
above
the
kVA etc.)
of individual
loads.
The maximum
estimated
kVA to be supplied however is
for
motors,
etc.)
application
of the
following
coefficients:
motors,
andand
thethe
application
of the
following
coefficients:
not equal to the total installed kVA.
η
η == the
the per-unit
per-unit efficiency
efficiency =
= output
output kW
kW // input
input kW
kW
The apparent-power
demand
of a load (which might be a single appliance) is
cos
cos ϕ
ϕ == the
the power
power factor
factor =
= kW
kW // kVA
kVA
obtained from its nominal power rating (corrected if necessary, as noted above for
The
apparent-power
demand
the
load
The
apparent-power
kVA
demandofof
ofthe
thefollowing
load
motors,
etc.) and the kVA
application
coefficients:
Pa
Pa =
= Pn
Pn /(
/(η
η xx cos
cos ϕ
ϕ))
η = the per-unit efficiency = output kW / input kW
(1)
From
value,
the
full-load
current
From
this
value,
thefactor
full-load
current
(A)(1) taken
taken by
by the
the load
load will
will be:
be:
cos
ϕ this
= the
power
= kW
/ kVA IIaa (A)
The apparent-power
kVA demand of the load
Pa x 103
c Ia =
b
Pa = Pn /(ηVx cos ϕ)
for single
phase-to-neutral
connected
load
From
this phase-to-neutral
value, the full-load
current Iaload
(A)(1) taken by the load will be:
for
single
connected
3
Pa
x
10
3
Pa x 10
c II a
c
a=
= 3xU
b
3xU
three-phase
balanced load
where:
for three-phase
single
phase-to-neutral
connected
for
balanced load
where: load
V = phase-to-neutral
voltage (volts)
3
Pa x 10
V = phase-to-neutral
voltage (volts)
I aphase-to-phase
=
c
U=
voltage (volts)
U = phase-to-phase
voltage (volts)
3xU
It may be noted that, strictly speaking, the total kVA of apparent power is not the
Itformay
be noted balanced
that, strictly
speaking,
the total kVA of apparent power is not the
three-phase
load
where:
arithmetical
sum of the calculated
kVA ratings of individual loads (unless all loads
arithmetical
sum of the
calculated
kVA ratings of individual loads (unless all loads are
V
=
phase-to-neutral
voltage
(volts)
are at the same power factor).
at
the
same power factor).
U
=
phase-to-phase
(volts)
It is
common
practicevoltage
however,
to make a simple arithmetical summation, the result
ItIt is
common
practicestrictly
however,
to makethe
a simple
arithmetical
summation,
thethe
result
bewill
noted
speaking,
total
of apparent
power is not
ofmay
which
givethat,
a kVA value
that exceeds
the kVA
true value
by an acceptable
“design
of
which
will
give
a
kVA
value
that
theof
true
value byloads
an acceptable
arithmetical
sum of the calculated exceeds
kVA ratings
individual
(unless all “design
loads
margin”.
margin”.
are
at the
same
power
When
some
or all
of thefactor).
load characteristics are not known, the values shown in
It is common
practice
however,
to make
a simple
arithmetical summation,
the result
Figure
B9 next
page may
be used
to give
a very approximate
estimate of VA
of
which will
give a kVA
value
exceeds
true
by an acceptable
demands
(individual
loads
are that
generally
toothe
small
tovalue
be expressed
in kVA or“design
kW).
(1) For greater precision, account must be taken of the factor
margin”.
The estimates for lighting loads are based on floor areas of 500 m2.
of
utilization
as account
explained
below
4.3 of the factor
(1)maximum
For greater
precision,
must
be in
taken
When some or all of the load characteristics are not known, the values shown in
of maximum utilization as explained below in 4.3
Figure B9 next page may be used to give a very approximate estimate of VA
Schneider
Electric
installation
guide
2016
Schneiderdemands
Electric -- Electrical
Electrical
installation
guide
2005
(individual
loads
are
generally too small to be expressed in kVA or kW).
2
© Schneider Electric - all rights reserved
The installed apparent power is commonly
assumed to be the arithmetical sum of the kVA
kVA
of individual loads. The maximum estimated
kVA
kVA to
to be
be supplied
supplied however
however is
is not
not equal
equal to the
The
apparent
power is commonly
to
theinstalled
total installed
total
installed
kVA. kVA.
assumed to be the arithmetical sum of the kVA
of individual loads. The maximum estimated
kVA to be supplied however is not equal to the
total installed kVA.
A - General rules of electrical installation design
A18
When some or all of the load characteristics are not known, the values shown in
Figure A9 may be used to give a very approximate estimate of VA demands
(individual loads are generally too small to be expressed in kVA or kW).
The estimates for lighting loads are based on floor areas of 500 m2.
Fluorescent lighting (corrected to cos ϕ = 0.86)
Type of application
Estimated (VA/m2)
Average lighting
fluorescent tube
level (lux = lm/m2)
(1)
with industrial reflector
Roads and highways
7
150
storage areas, intermittent work
Heavy-duty works: fabrication and
14
300
assembly of very large work pieces
Day-to-day work: office work
24
500
Fine work: drawing offices
41
800
high-precision assembly workshops
Power circuits
Type of application
Estimated (VA/m2)
Pumping station compressed air
3 to 6
Ventilation of premises
23
Electrical convection heaters:
private houses
115 to 146
flats and apartments
90
Offices
25
Dispatching workshop
50
Assembly workshop
70
Machine shop
300
Painting workshop
350
Heat-treatment plant
700
(1) example: 65 W tube (ballast not included), flux 5,100 lumens (Im),
luminous efficiency of the tube = 78.5 Im / W.
Fig. A9: Estimation of installed apparent power
4.3 Estimation of actual maximum kVA demand
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.
© Schneider Electric - all rights reserved
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.
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.
Schneider Electric - Electrical installation guide 2016
4 Power loading of an installation
A19
Diversity factor - Coincidence factor (ks)
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:
b 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 y 1 and
can be expressed as a percentage
b Diversity factor: the reciprocal of the coincidence factor. It means it will
always be u 1.
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.
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.
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
Number of downstream
consumers
2 to 4
5 to 9
10 to 14
15 to 19
20 to 24
25 to 29
30 to 34
35 to 39
40 to 49
50 and more
6 consumers
36 kVA
3 rd
floor
4 consumers
24 kVA
2 nd
floor
5 consumers
30 kVA
1st
floor
6 consumers
36 kVA
ground
floor
4 consumers
24 kVA
Fig. A10: Example of diversity factors for an apartment block as defined in French standard
NFC14-100, and applicable for apartments without electrical heating
0.78
heating, a factor of 0.8 is recommended, regardless of the number of consumers.
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 Fig. A11, 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:
0.63
0.53
0.49
150 x 0.46 x 103
0.46
400
3
= 100 A
the current entering the third floor is:
(36 + 24) x 0.63 x 103
Fig. A11: Application of the diversity factor (ks) to an apartment
block of 5 storeys
400
3
= 55 A
Schneider Electric - Electrical installation guide 2016
© Schneider Electric - all rights reserved
4th
floor
Diversity
factor (ks)
1
0.78
0.63
0.53
0.49
0.46
0.44
0.42
0.41
0.38
A - General rules of electrical installation design
A20
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 y 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 y 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)
Lifts and catering hoist (2) b For the most powerful
motor
1
b For the second most
powerful motor
0.75
b For all motors
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.
© Schneider Electric - all rights reserved
Fig. A13: Diversity factor according to circuit function (see UTE C 15-105 table AC)
Schneider Electric - Electrical installation guide 2016
motor
1
c For the second most
powerful motor
0.75
c For all motors
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,
oncreased by a third of its starting current.
4 Power loading of an installation
A21
Fig. B13 : Factor of simultaneity according to circuit function
4.4 Example of application of factors ku and ks
4.4 Example of application of factors ku and ks
An example in the estimation of actual maximum kVA demands at all levels of an
An
examplefrom
in theeach
estimation
of actual
maximum
demands
at all
levels
of an
installation,
load position
to the
point ofkVA
supply
(see Fig.
B14
opposite
installation,
from each load position to the point of supply is given Fig. A14.
page).
In
In this
this example,
example, the
the total
total installed
installed apparent
apparent power
power is
is 126.6
126.6 kVA,
kVA, which
which corresponds
corresponds
to
value at
at the
the LV
LV terminals
transformer
to an
an actual
actual (estimated)
(estimated) maximum
maximum value
terminals of
of the
the MV/LV
HV/LV transformer
of
of 65
65 kVA
kVA only.
only.
Note: in order to select cable sizes for the distribution circuits of an installation, the
Note: in order to select cable sizes for the distribution circuits of an installation, the
current I (in amps) through a circuit is determined from the equation:
current I (in amps) through a circuit is determined from the equation:
kVA x 103
I=
U 3
where kVA
kVA is
is the
the actual
actual maximum
maximum 3-phase
3-phase apparent-power
apparent-power value
value shown
shown on
on the
the
where
diagram for
for the
the circuit
circuit concerned,
concerned, and
and U
U is
is the
the phase
phasetodiagram
to- phase
phase voltage
voltage (in
(in volts).
volts).
4.5 Diversity factor
The term diversity factor, as defined in IEC standards, is identical to the factor of
Level 2in 4.3. In some English-speaking
Level 3
Level
1 guide, as described
simultaneity (ks) used
in this
countries
however
(at
the
time
of
writing)
diversity
factor
is
the
inverse
of ksApparent
i.e. it is
Apparent Utilization
Apparent
Diversity
Apparent Diversity
Apparent Diversity
always
power
factor
power u 1. factor
power
factor
power
factor
power
Utilization
Workshop A Lathe
(Pa)
kVA
max.
demand
demand
Schneider Electric - Electrical installation guide 2005
max. kVA
kVA
no. 1
5
0.8
4
no. 2
5
0.8
4
no. 3
5
0.8
4
14.4
Socketoulets
3.6 Lighting
circuit
0.8
4
2
0.8
1.6
no. 2
2
0.8
1.6
18
1
18
0.2
30 fluorescent
lamps
3
1
3
1
Workshop B Compressor
3 socketoutlets 10/16 A
15
0.8
12
1
10 fluorescent
lamps
1
1
1
Workshop C Ventilation no. 1
2.5
no. 2
2.5
no. 1
no. 2
10.6
0.4
5 socketoutlets 10/16 A
20 fluorescent
lamps
Workshop A
distribution
box
0.9
18.9
3
Main
general
distribution
board
MGDB
Power
circuit
12 Socket- Workshop B
4.3
1
oulets
distribution
box
1
1
2.5
1
2.5
Distribution
box
15
1
15
15
1
15
18
1
18
0.28
5 oulets
Lighting
2
1
2
1
2 circuit
LV / MV
15.6
65
0.9
Lighting
circuit
1
1
Oven
Power
circuit
0.75
5
10.6
demand
kVA
Distribution
box
no. 4
Pedestalno. 1
drill
5 socketoutlets 10/16 A
demand
kVA
0.9
Workshop C
distribution
35
Powver
box
circuit
0.9
37.8
Socket-
© Schneider Electric - all rights reserved
Fig A14: An example in estimating the maximum predicted loading of an installation (the factor values used are for demonstration purposes only)
Schneider Electric - Electrical installation guide 2016
A - General rules of electrical installation design
A22
B20 B - General design - Regulations Installed power
B20 B - General design - Regulations Installed power
4 Power loading of an installation
4.5
Choice of loading
transformerof
rating
4 Power
an installation
When an installation is to be supplied directly from a MV/LV transformer
and the maximum apparent-power loading of the installation has been determined,
a suitable rating for the transformer can be decided, taking into account the following
c Installation constraints
(temperature...) standard transformer ratings
considerations
(see Fig. A15):
b
The
possibility
of improving
the
installation
(see chapter
L) by:
The
nominal
full-load
current In
onpower
the LVfactor
side of
of the
a 3-phase
transformer
is given
b Anticipated3extensions to the installation
Pa x 10 constraints (e.g. temperature)
bI nInstallation
=
b
Standard
U 3transformer
c Installation
constraintsratings.
(temperature...) standard transformer ratings
where
The
nominal
full-load
current IIn
on the
the LV
LV side
side of
of aa 3-phase
3-phase transformer
transformer is
is given
given by:
by:
The nominal full-load current
n on
c Pa P
=akVA
rating
of
the
transformer
3
x 10
cI nU== phase-to-phase voltage at no-load in volts (237 V or 410 V)
U 3
c In is in amperes.
where
where
b Pa = kVA rating of the transformer
c Pa = kVA rating of the transformer
b U = phase-to-phase voltage at no-load in volts (237 V or 410 V)
c IUna=issingle-phase
phase-to-phase
voltage at no-load in volts (237 V or 410 V)
For
b
in amperes. transformer:
c In is in amperes.
For a single-phase transformer:
Pa x 103
In =
For a single-phase
transformer:
V
where
where
cV
terminals at
at no-load
no-load (in
(in volts)
volts)
b
V=
= voltage
voltage between
between LV
LV terminals
Pa x 103
cI nSimplified
equation for 400 V (3-phase load)
=
SimplifiedVequation for 400 V (3-phase load)
c In = kVA x 1.4
b
In = kVA x 1.4
where
The IEC standard for power transformers is IEC 60076.
The
IEC
standard
for power
transformers
is IEC(in
60076.
cV=
voltage
between
LV terminals
at no-load
volts)
c Simplified equation for 400 V (3-phase load)
c In = kVA x 1.4
© Schneider Electric - all rights reserved
4.7
Choice
ofpower
power-supply
sources
The IEC
standard for
transformers is IEC
60076.
The study developed in E1 on the importance of maintaining a continuous supply
Apparent power
In (A)plant. The choice and characteristics
raises the question of the
use of standby-power
kVA
237 V
410 V
of
these
alternative
sources
are
described
in
E1.4.
4.7 Choice of power-supply
sources
100
244
141
For the main source of supply the choice is generally between a connection to the
160
390
225
HV
the LV
network in
of E1
theon
power-supply
utility.
Theorstudy
developed
the importance
of maintaining a continuous supply
250
609
352
raises
the question
of the
use of standby-power
plant. Thewhere
choicethe
and
characteristics
In
practice,
connection
to
be necessary
load
exceeds
315a HV source may 767
444
of
these
alternative
sources
are
described
in
E1.4.
(or is planned eventually
to exceed) a certain
level - generally
of the order of
400
974
563
250
kVA,
or ifsource
the quality
of service
required
is greaterbetween
than
available
For the
main
of 500
supply
the choice
is 1218
generally
connection
to the
704 thatanormally
from
LV LV
network.
HV ora the
network of630
the power-supply utility.
1535
887
Moreover,
the installation
to cause
disturbance
towhere
neighbouring
In practice,ifconnection
to a is
HVlikely
source
may 1949
be
necessary
the load exceeds
800
1127
consumers,
when
connected
to a LVanetwork,
the supply
authorities
(or is planned
eventually
to exceed)
certain
level
- generally
of the may
orderpropose
of
1000
2436
1408
a
HVkVA,
service.
250
or if the quality
of service required3045
is greater than
1250
1760that normally available
from a LVatnetwork.
1600
3898
2253
Supplies
HV can have
certain advantages:
in fact, a HV
consumer:
Moreover,
if the installation
is likely to cause
disturbance
tocase
neighbouring
2000consumers,
4872
2816
c
Is not disturbed
by other
which
could be the
at LV
consumers, when connected
the supply
authorities may propose
2500 to a LV network,
6090
3520
c Is free to choose any type of LV earthing system
a HV service.
3150
7673
4436
c Has a wider choice of economic tariffs
Supplies at HV can have certain advantages: in fact, a HV consumer:
c Can accept very large increases in load
c IsA15:
not disturbed
by otherpowers
consumers, which could be the case at LV
Fig.
Standard
apparent
It should
be noted,
however, that:for MV/LV transformers and related nominal output currents
c Is free to choose any type of LV earthing system
c The consumer is the proprietor of the HV/LV substation and, in some countries,
c Has
a wider
choice
of economic
tariffs
he
must
build and
equip
it at his own
expense. The power utility can, in certain
c
Can
accept
very
large
increases
in load
circumstances, participate in the investment,
at the level of the HV line for example
It A
should
bethe
noted,
however,
that:
c
part of
connection
costs
can, for instance, often be recovered if a second
consumer
is connected
to the HV of
line
a certain
timeand,
following
the countries,
original
c The consumer
is the proprietor
thewithin
HV/LV
substation
in some
consumer’s
own
he must build
andconnection
equip it at his own expense. The power utility can, in certain
circumstances,
in only
the investment,
at the
level
of the HVaccess
line for to
example
c
The consumerparticipate
has access
to the LV part
of the
installation,
the
HV
to the
utility
(meter
reading,
operations,
etc.).
c A part
part being
of thereserved
connection
costs
can,personnel
for instance,
often
be recovered
if a second
However,
countries,
the line
HV protective
circuittime
breaker
(or fused
load-break
consumer in
is certain
connected
to the HV
within a certain
following
the original
switch)
can be
operated
by the consumer
consumer’s
own
connection
c The type
and location
of theonly
substation
are
agreed
the consumer
and
consumer
has access
to the LV
part
of thebetween
installation,
access to the
the
HV utility
part being reserved to the utility personnel (meter reading, operations, etc.).
However, in certain countries, the HV protective circuit breaker (or fused load-break
switch) can be operated by the consumer
c The type and location of the substation are agreed between the consumer and
the utility
Schneider Electric - Electrical installation guide 2016
4 Power loading of an installation
A23
4.6 Choice of power-supply sources
The importance of maintaining a continuous supply raises the question of the use
of standby-power plant. The choice and characteristics of these alternative sources
are part of the architecture selection, as described in chapter D.
For the main source of supply the choice is generally between a connection
to the MV or the LV network of the power-supply utility. In some cases main source
of supply can be rotating generators in the case of remote installations with difficult
access to the local Utility public grid (MV or LV) or where the reliability of the public
grid does not have the minimum level of reliability expected.
In practice, connection to a MV source may be necessary where the load exceeds
(or is planned eventually to exceed) a certain level - generally of the order of
250 kVA, or if the quality of service required is greater than that normally available
from a LV network.
Moreover, if the installation is likely to cause disturbance to neighbouring consumers,
when connected to a LV network, the supply authorities may propose a MV service.
© Schneider Electric - all rights reserved
Supplies at MV can have certain advantages: in fact, a MV consumer:
b Is not disturbed by other consumers, which could be the case at LV
b Is free to choose any type of LV earthing system
b Has a wider choice of economic tariffs
b Can accept very large increases in load
It should be noted, however, that:
b The consumer is the owner of the MV/LV substation and, in some countries,
he must build equip and maintain it at his own expense. The power utility can,
in certain circumstances, participate in the investment, at the level of the MV line
for example
b A part of the connection costs can, for instance, often be recovered if a second
consumer is connected to the MV line within a certain time following the original
consumer’s own connection
b The consumer has access only to the LV part of the installation, access to the
MV part being reserved to the utility personnel (meter reading, operations, etc.).
However, in certain countries, the MV protective circuit breaker (or fused load-break
switch) can be operated by the consumer
b The type and location of the substation are agreed between the consumer
and the utility.
More and more renewable energy sources such as photovoltaic panels are used
to supply low-voltage electrical installations. In some case these PV panels
are connected in parallel to the Utility grid or these PV panels are used in an
autonomous mode without connection to the public grid. Conversion from d.c. to a.c.
is then necessary as rated voltage of these PV panels are higher and higher (few
hundreds volts) and also because PV panels produce d.c. currents.
See also chapter P "Photovoltaic installations"
Schneider Electric - Electrical installation guide 2016