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Technical Series

......................

Electrical
installation guide
According to IEC International Standards

New edition

2005
http://theguide.merlin-gerin.com

This guide has been written for electrical Engineers who have to design,
realize, inspect or maintain electrical installations in compliance with
international Standards of the International Electrotechnical
Commission (IEC).
“Which technical solution will guarantee that all relevant safety rules are
met?” This question has been a permanent guideline for the elaboration of
this document.
An international Standard such as the IEC 60364 “Electrical Installation in
Buldings” specifies extensively the rules to comply with to ensure safety
and predicted operational characteristics for all types of electrical
installations. As the Standard must be extensive, and has to be applicable
to all types of products and the technical solutions in use worldwide, the
text of the IEC rules is complex, and not presented in a ready-to-use
order. The Standard cannot therefore be considered as a working
handbook, but only as a reference document.
The aim of the present guide is to provide a clear, practical and step-bystep explanation for the complete study of an electrical installation,
according to IEC 60364 and other relevant IEC Standards. Therefore, the
first chapter (B) presents the methodology to be used, and each chapter
deals with one out of the eight steps of the study. The two last chapter are
devoted to particular supply sources, loads and locations, and appendix
provides additional information. Special attention must be paid to the
EMC appendix, which is based on the broad and practical experience on
electromagnetic compatibility problems.
We all hope that you, the user, will find this handbook genuinely helpful.
Schneider Electric S.A.

This technical guide is the result of
a collective effort.
Technical advisor:
Serge Volut
Design/Technical content:
Guy Satre-Duplessis
Illustrations and production:
AXESS - Valence -France
Printing:
Les Deux Ponts - F; rance

The Electrical Installation Guide is a single document covering the
techniques, regulations and standards related to electrical installations.
It is intended for electrical professionals in companies, design offices,
inspection organisations, etc.
Electrical equipment should be serviced only by qualified electrical
maintenance personnel, and this document should not be viewed as
sufficient instructions for those who are not otherwise qualified to operate,
service or maintain the equipment discussed. Although reasonable care
has been taken to provide accurate and authoritative information in this
document, no responsibility is assumed by Schneider Electric for any
consequences arising from the use of this material.

Second edition
March 2005

This new edition has been published to take into account changes in
techniques, standards and regulations, in particular electrical installation
standard IEC 60364.

Price: 90 €
ISBN : 2-907314-47-5
N° dépôt légal: 1er semestre 2005
Conseil © Schneider Electric
All rights reserved for all the countries

We thank all the readers of the previous edition of this guide for their
comments that have helped improve the current edition.
We also thank the many people and organisations, to numerous to name
here, who have contributed in one way or another to the preparation of
this guide.

Foreword
Roland Talon, Chairman TC 64 - International Electrotechnical Commission
It is generally agreed that electrical equipment will provide the best
performance (safety, operation and service life) when it is properly
installed, which includes good co-ordination.
The task of Technical Committee 64 of the IEC (International
Electrotechnical Commission) is to develop and keep up-to-date
requirements for electrical installations. TC64 also has a Safety Pilot
Function for installations, equipment, products and systems. Delegates
from many National Committees work in TC 64, drawn from
manufacturers, laboratories, verification bodies, installers, and electrical
power supply companies...
…with the consequence that IEC Standard 60364 is considered as the
definitive document on which to base the design and implementation of an
electrical installation.
Furthermore the electrical environment is increasingly complex, mainly
due to electromagnetic influences and other kinds of disturbances, and
the continuous operation of all equipment supplied by the electrical
installation has become a fundamental requirement.
Consequently designers, installers and consumers need guidance on the
selection and installation of electrical equipment.
With this in mind, Schneider Electric has developed this Electrical
Installation Guide. It has been prepared by engineers from Schneider
Electric who are very experienced in electrical installation technology and
possess excellent knowledge of consumer problems and requirements,
and of IEC Standard 60364 and other relevant IEC standards.
Last but not least, this Electrical Installation Guide has adopted the IEC
Standard 60364 as a basis and as a result facilitates and favours
international trade.
As TC 64 Chairman and formerly the representative of French Electrical
Contractors on TC64, it is my great pleasure and honour to introduce this
guide. I am sure it will prove very useful in the implementation of the
provisions of 60364 and in meeting consumers’ concerns.

Roland Talon has been with the French Electrical
Contractors’ Association (FFIE) for 20 years.
He previously worked for electrical contracting
companies. During that period, he was deeply
involved in many international projects.
Roland Talon has been Chairman of IEC TC 64
since 2002 as well as chairman of CENELEC TC64.

Continuity of supply

Type tested switchboards
by simple assembly

Discrimination
guarantees co-ordination
between the operating
characteristics of serialconnected circuitbreakers. Should a fault
occurs downstream, only
the circuit-breaker
placed immediately
upstream from the fault
will trip.

Knowledge at all times of installation status

Direct connection of
the Canalis KT busbar
trunking on the
Masterpact 3200 A
circuit-breaker

Thanks to the use of standard Web technologies,
you can offer your customers intelligent Merlin Gerin switchboards
allowing easy access to information:
follow-up of currents, voltages, powers,
consumption history, etc.

SM6

Sepam

Masterpact

Compact

Multi 9

Prisma Plus

Medium voltage switchboard
system from 1 to 36 kV

Protection relays

Protection switchgear
from 100 to 6300 A

Protection switchgear system
from 100 to 630 A

Modular protection switchgear
system up to 125 A

Functional system for
electrical distribution
switchboards
up to 3200 A

A consistent design of offers from Medium Voltage to Ultra Terminal

Guiding tools for more efficient design
and implementation of your installations

The technical guides

CAD software and tools

Training

The electrical installation guide,
the switchboard implementation guide,
the technical publications or
“Cahiers Techniques” and coordination
tables all form genuine reference tools
for the design of high-performance electrical
installations. These guides help you
to comply to installation rules and standards

The CAD software and tools enhance
productivity and safety.
They help you create your installations
by simplifying product choice while also
complying with standards and
proper procedures.

Training allows you to acquire the Merlin Gerin
expertise (installation design, work with power on, etc.)
for increased efficiency and a guarantee of improved
customer service.

For more details on Guilding System, please consult www.merlingerin.com
Schneider Electric - Electrical installation guide 2005

Schneider Electric - Electrical installation guide 2005

General contents

A

General design - Regulations Installed power

B

Connection to the HV utility
distribution network

C

Connection to the LV utility
distribution network

D

Distribution in low-voltage
installations

E

Protection against electric
shocks

F

The protection of circuit

G

The switchgear

H

Protection against voltage
surges

J

Power factor correction and
harmonic filtering

K

Detection and filtering of
harmonics

L

Particular sources and loads

M

Domestic and similar premises
and special locations

N

EMC guidelines

Ap

General contents

A

B
C

General design - Regulations - Installed power
1 Methodology

B2

2 Rules and statutory regulations

B4

3 Installed power loads - Characteristics

B10

4 Power loading of an installation

B15

5 Power monitoring and control

B21

Connection to the HV utility distribution network
1 Supply of power at high voltage
2 Procedure for the establishment of a new substation

C14

3 Protection aspect

C16

4 The consumer substation with LV metering

C22

5 The consumer substation with HV metering

C30

6 Constitution of HV/LV distribution substations

C35

D

Connection to the LV utility distribution network

E

Distribution in low-voltage installations

F

G

H

C2

1 Low voltage utility distribution networks

D2

2 Tariffs and metering

D16

1 LV distribution schemes

E2

2 Earthing schemes

E17

3 The installation system

E30

4 External influences (IEC 60364-5-51)

E38

Protection against electric shocks
1 General

F2

2 Protection against direct contact

F4

3 Protection against indirect contact

F6

4 Protection of goods due to insulation fault

F17

5 Implementation of the TT system

F19

6 Implementation of the TN system

F25

7 Implementation of the IT system

F31

8 Residual current differential devices RCDs

F38

The protection of circuits
1 General

G2

2 Practical method for determining the smallest allowable
cross-sectional area of circuit conductors

G11

3 Determination of voltage drop

G23

4 Short-circuit current

G27

5 Particular cases of short-circuit current

G33

6 Protective earthing conductor

G40

7 The neutral conductor

G45

The switchgear
1 The basic functions of LV switchgear

H2

2 The switchgear

H5

3 Choice of switchgear

H10

4 Circuit breaker

H11

Schneider Electric - Electrical installation guide 2005

General contents

J
K

L

M
N

A

Protection against voltage surges
1 General

J2

2 Overvoltage protection devices

J6

3 Standards

J11

4 Choosing a protection device

J14

Power factor correction and harmonic filtering
1 Reactive energy and power factor

K2

2 Why to improve the power factor?

K5

3 How to improve the power factor?

K7

4 Where to install power correction capacitors?

K10

5 How to decide the optimum level of compensation?

K12

6 Compensation at the terminals of a transformer

K15

7 Power factor improvement of induction motors

K18

8 Example of an installation before and after power-factor correction

K20

9 The effects of harmonics

K21

10 Implementation of capacitor banks

K24

Detection and filtering of harmonics
1 The problem:
Why is it necessary to detect and eliminate harmonics?

L2

2 Standards

L3

3 General

L4

4 Main effects of harmonics in installations

L6

5 Essential indicators of harmonic distortion and
measurement principles

L11

6 Measuring the indicators

L14

7 Detection devices

L16

8 Solutions to attenuate harmonics

L17

Particular sources and loads
1 Protection of a LV generator set and the downstream circuits

M2

2 Uninterruptible Power Supply Units (UPS)

M11

3 Protection of LV/LV transformers

M24

4 Lighting circuits

M27

5 Asynchronous motors

M42

Domestic and similar premises and special locations
1 Domestic and similar premises

N2

2 Bathrooms and showers

N8

3 Recommendations applicable to special installations and locations N12

Appendix

EMC guidelines
1 Electrical distribution

Ap2

2 Earthing principles and structures

Ap3

3 Implementation

Ap5

4 Coupling mechanism and counter-measures

Ap14

5 Wiring recommendations

Ap20

Schneider Electric - Electrical installation guide 2005

Chapter B
General design - Regulations Installed power

B1

Contents

1
2

3
4

5

Methodology

B2

Rules and statutory regulations

B4

2.1 Definition of voltage ranges

B4

2.2 Regulations

B5

2.3 Standards

B5

2.4 Quality and safety of an electrical installation

B6

2.5 Initial testing of an installation

B6

2.6 Periodic check-testing of an installation

B7

2.7 Conformity (with standards and specifications) of equipment
used in the installation

B7

2.8 Environment

B8

Installed power loads - Characteristics

B10

3.1 Induction motors

B10

3.2 Resistive-type heating appliances and incandescent lamps
(conventional or halogen)

B12

Power loading of an installation

B15

4.1 Installed power (kW)

B15

4.2 Installed apparent power (kVA)

B15

4.3 Estimation of actual maximum kVA demand

B18

4.4 Example of application of factors ku and ks

B17

4.5 Diversity factor

B18

4.6 Choice of transformer rating

B19

4.7 Choice of power-supply sources

B20

Power monitoring and control

B21

5.1 Main user’s benefits

B21

5.2 From Network Monitoring and Control System to
Intelligent Power Equipment

B23

5.3 Typical services possibly brought by intelligent equipment
compared to other solutions

B25

5.4 Technical inputs on communicating systems

B26

5.5 Main constraints to take into account to design
a communicating or intelligent power equipment

B27

Schneider Electric - Electrical installation guide 2005

B - General design - Regulations Installed power

1 Methodology

B2

The study of an electrical installation using this guide requires the reading of all the
chapters in the order in which they are presented.

Listing of power demands
B – General design - Regulations Installed power

The study of a proposed electrical installation requires an adequate understanding of
all governing rules and regulations.
The total power demand can be calculated from the data relative to the location and
power of each load, together with the knowledge of the operating modes (steady
state demand, starting conditions, non simultaneous operation, etc.)
From these data, the power required from the supply source and (where appropriate)
the number of sources necessary for an adequate supply to the installation are
readily obtained.
Local information regarding tariff structures is also required to allow the best choice
of connection arrangement to the power-supply network, e.g. at high voltage or low
voltage level.

Service connection
This connection can be made at:

C – Connection to the HV utility distribution
network

c High Voltage level
A consumer-type substation will then have to be studied, built and equipped. This
substation may be an outdoor or indoor installation conforming to relevant standards
and regulations (the low-voltage section may be studied separately if necessary).
Metering at high-voltage or low-voltage is possible in this case.

D - Low-voltage service connections

c Low Voltage level
The installation will be connected to the local power network and will (necessarily) be
metered according to LV tariffs.

LV distribution system
E - Distribution within a low-voltage installation

The whole installation distribution network is studied as a complete system.
The number and characteristics of standby emergency-supply sources are defined.
Neutral earthing arrangements are chosen according to local regulations, constraints
related to the power-supply, and to the type of loads
The distribution equipment (panelboards, switchgears, circuit connections, ...) are
determined from building plans and from the location and grouping of loads.
The type of premises and allocation can influence their immunity to external
disturbances.

Protection against electric shock
F - Protection against electric shock

The earthing system (TT, IT or TN) having been previously determined, then the
appropriate protective devices must be implemented in order to achieve protection
against hazards of direct or indirect contact.

Circuits and switchgear
G - The protection of circuits

Each circuit is then studied in detail. From the rated currents of the loads, the level of
short-circuit current, and the type of protective device, the cross-sectional area of
circuit conductors can be determined, taking into account the nature of the
cableways and their influence on the current rating of conductors.
Before adopting the conductor size indicated above, the following requirements must
be satisfied:
c The voltage drop complies with the relevant standard
c Motor starting is satisfactory
c Protection against electric shock is assured
The short-circuit current Isc is then determined, and the thermal and electrodynamic
withstand capability of the circuit is checked.
These calculations may indicate that it is necessary to use a conductor size larger
than the size originally chosen.

H - The switchgear

The performance required by the switchgear will determine its type and
characteristics.
The use of cascading techniques and the discriminative operation of fuses and
tripping of circuit breakers are examined.

Schneider Electric - Electrical installation guide 2005

B - General design - Regulations Installed power

1 Methodology
B3

Protection against overvoltages
J – Protection against overvoltages

Direct or indirect lightning strokes can damage electrical equipment at a distance of
several kilometers. Operating voltage surges and transient industrial frequency
voltage surges can also produce the same consequences.The effects are
examinated and solutions are proposed.

Reactive energy
K - Power factor improvement and harmonic
filtering

The power factor correction within electrical installations is carried out locally,
globally or as a combination of both methods.

Harmonics
L - Harmonics detection and filtering

Harmonics in the network affect the quality of energy and are at the origin of many
pollutions as overloads, vibrations, ageing of equipment, trouble of sensitive
equipment, of local area networks, telephone networks. This chapter deals with the
origins and the effects of harmonics and explain how to measure them and present
the solutions.

Particular supply sources and loads
M - Particular supply sources and loads

Particular items or equipment are studied:
c Specific sources such as alternators or inverters
c Specific loads with special characteristics, such as induction motors, lighting
circuits or LV/LV transformers
c Specific systems, such as direct-current networks

Generic applications
Certain premises and locations are subject to particularly strict regulations: the most
common example being domestic dwellings.

N - Domestic and similar premises and special
locations

Ecodial software
Ecodial software(1) provides a complete design package for LV installations, in
accordance with IEC standards and recommendations.
The following features are included:
c Construction of one-line diagrams
c Calculation of short-circuit currents
c Calculation of voltage drops
c Optimization of cable sizes
c Required ratings of switchgear and fusegear
c Discrimination of protective devices
c Recommendations for cascading schemes
c Verification of the protection of persons
c Comprehensive print-out of the foregoing calculated design data

(1) Ecodial is a Merlin Gerin product and is available in French
and English versions.
Schneider Electric - Electrical installation guide 2005

B - General design - Regulations Installed power

2 Rules and statutory regulations

B4

Low-voltage installations are governed by a number of regulatory and advisory texts,
which may be classified as follows:
c Statutory regulations (decrees, factory acts,etc.)
c Codes of practice, regulations issued by professional institutions, job specifications
c National and international standards for installations
c National and international standards for products

2.1 Definition of voltage ranges
IEC voltage standards and recommendations

Ba

ck

Three-phase four-wire or three-wire systems
Nominal voltage (V)
50 Hz
60 Hz
–
120/208
–
240
230/400(1)
277/480
400/690(1)
480
–
347/600
1000
600

Single-phase three-wire systems
Nominal voltage (V)
60 Hz
120/240
–
–
–
–
–

(1) The nominal voltage of existing 220/380 V and 240/415 V systems shall evolve
toward the recommended value of 230/400 V. The transition period should be as short
as possible and should not exceed the year 2008. During this period, as a first step,
the electricity supply authorities of countries having 220/380 V systems should bring
the voltage within the range 230/400 V +6 %, -10 % and those of countries having
240/415 V systems should bring the voltage within the range 230/400 V +10 %, -6 %.
At the end of this transition period, the tolerance of 230/400 V ± 10 % should have
been achieved; after this the reduction of this range will be considered. All the above
considerations apply also to the present 380/660 V value with respect to the
recommended value 400/690 V.

Fig. B1 : Standard voltages between 100 V and 1000 V (IEC 60038 Edition 6.2 2002-07)

Ba

ck

Series I
Highest voltage
for equipment (kV)
3.6(1)
7.2(1)
12
–
–
–
(17.5)
24
–
36(3)
–
40.5(3)

Nominal system
voltage (kV)
3.3(1)
3(1)
6.6(1)
6(1)
11
10
–
–
–
–
–
–
–
(15)
22
20
–
–
33(3)
–
–
–
–
35(3)

Series II
Highest voltage
for equipment (kV)
4.40(1)
–
–
13.2(2)
13.97(2)
14.52(1)
–
–
26.4(2)
–
36.5
–

Nominal system
voltage (kV)
4.16(1)
–
–
12.47(2)
13.2(2)
13.8(1)
–
–
24.94(2)
–
34.5
–

These systems are generally three-wire systems unless otherwise indicated.
The values indicated are voltages between phases.
The values indicated in parentheses should be considered as non-preferred values.
It is recommended that these values should not be used for new systems to be
constructed in future.
Note 1: It is recommended that in any one country the ratio between two adjacent
nominal voltages should be not less than two.
Note 2: In a normal system of Series I, the highest voltage and the lowest voltage do
not differ by more than approximately ±10 % from the nominal voltage of the system.
In a normal system of Series II, the highest voltage does not differ by more then +5 %
and the lowest voltage by more than -10 % from the nominal voltage of the system.
(1) These values should not be used for public distribution systems.
(2) These systems are generally four-wire systems.
(3) The unification of these values is under consideration.

Fig. B2 : Standard voltages above 1 kV and not exceeding 35 kV
(IEC 60038 Edition 6.2 2002-07)

Schneider Electric - Electrical installation guide 2005

B - General design - Regulations Installed power

2 Rules and statutory regulations
B5

2.2 Regulations
In most countries, electrical installations shall comply with more than one set of
regulations, issued by National Authorities or by recognized private bodies. It is
essential to take into account these local constraints before starting the design.

2.3 Standards
This Guide is based on relevant IEC standards, in particular IEC 60364. IEC 60364
has been established by medical and engineering experts of all countries in the
world comparing their experience at an international level. Currently, the safety
principles of IEC 60364 and 60479-1 are the fundamentals of most electrical
standards in the world (see table below and next page).

IEC 60364-7-708
IEC 60364-7-709
IEC 60364-7-710
IEC 60364-7-711
IEC 60364-7-712
IEC 60364-7-713
IEC 60364-7-714
IEC 60364-7-715
IEC 60364-7-717
IEC 60364-7-740
IEC 60427
IEC 60439-1
IEC 60439-2
IEC 60439-3
IEC 60439-4
IEC 60446
IEC 60439-5
IEC 60479-1
IEC 60479-2
IEC 60479-3

ck

IEC 60364-7-706
IEC 60364-7-707

Standard voltages
Power transformers - Temperature rise
Power transformers - Insulation levels, dielectric tests and external clearances in air
Power transformers - Ability to withstand short circuit
Power transformers - Determination of sound levels
Semiconductor convertors - General requirements and line commutated convertors
Electrical relays
High-voltage switches - High-voltage switches for rated voltages above 1 kV and less than 52 kV
Low-voltage fuses - General requirements
Low-voltage fuses - Supplementary requirements for fuses for use by unskilled persons (fuses mainly for household and similar applications)
High-voltage fuses - Current-limiting fuses
Electric cables - Calculation of the current rating - Current rating equations (100% load factor) and calculation of losses - General
Electrical installations of buildings
Electrical installations of buildings - Fundamental principles
Electrical installations of buildings - Protection for safety - Protection against electric shock
Electrical installations of buildings - Protection for safety - Protection against thermal effects
Electrical installations of buildings - Protection for safety - Protection against overcurrent
Electrical installations of buildings - Protection for safety - Protection against electromagnetic and voltage disrurbance
Electrical installations of buildings - Selection and erection of electrical equipment - Common rules
Electrical installations of buildings - Selection and erection of electrical equipment - Wiring systems
Electrical installations of buildings - Selection and erection of electrical equipment - Isolation, switching and control
Electrical installations of buildings - Selection and erection of electrical equipment - Earthing arrangements
Electrical installations of buildings - Selection and erection of electrical equipment - Other equipments
Electrical installations of buildings - Verification and testing - Initial verification
Electrical installations of buildings - Requirements for special installations or locations - Locations containing a bath tub or shower basin
Electrical installations of buildings - Requirements for special installations or locations - Swimming pools and other basins
Electrical installations of buildings - Requirements for special installations or locations - Locations containing sauna heaters
Electrical installations of buildings - Requirements for special installations or locations - Construction and demolition site installations
Electrical installations of buildings - Requirements for special installations or locations - Electrical installations of agricultural and horticultural
premises
Electrical installations of buildings - Requirements for special installations or locations - Restrictive conducting locations
Electrical installations of buildings - Requirements for special installations or locations - Earthing requirements for the installation of data
processing equipment
Electrical installations of buildings - Requirements for special installations or locations - Electrical installations in caravan parks and caravans
Electrical installations of buildings - Requirements for special installations or locations - Marinas and pleasure craft
Electrical installations of buildings - Requirements for special installations or locations - Medical locations
Electrical installations of buildings - Requirements for special installations or locations - Exhibitions, shows and stands
Electrical installations of buildings - Requirements for special installations or locations - Solar photovoltaic (PV) power supply systems
Electrical installations of buildings - Requirements for special installations or locations - Furniture
Electrical installations of buildings - Requirements for special installations or locations - External lighting installations
Electrical installations of buildings - Requirements for special installations or locations - Extra-low-voltage lighting installations
Electrical installations of buildings - Requirements for special installations or locations - Mobile or transportable units
Electrical installations of buildings - Requirements for special installations or locations - Temporary electrical installations for structures,
amusement devices and booths at fairgrounds, amusement parks and circuses
High-voltage alternating current circuit-breakers
Low-voltage switchgear and controlgear assemblies - Type-tested and partially type-tested assemblies
Low-voltage switchgear and controlgear assemblies - Particular requirements for busbar trunking systems (busways)
Low-voltage switchgear and controlgear assemblies - Particular requirements for low-voltage switchgear and controlgear assemblies intended to
be installed in places where unskilled persons have access for their use - Distribution boards
Low-voltage switchgear and controlgear assemblies - Particular requirements for assemblies for construction sites (ACS)
Basic and safety principles for man-machine interface, marking and identification - Identification of conductors by colours or numerals
Low-voltage switchgear and controlgear assemblies - Particular requirements for assemblies intended to be installed outdoors in public places Cable distribution cabinets (CDCs)
Effects of current on human beings and livestock - General aspects
Effects of current on human beings and livestock - Special aspects
Effects of current on human beings and livestock - Effects of currents passing through the body of livestock
Ba

IEC 60038
IEC 60076-2
IEC 60076-3
IEC 60076-5
IEC 60076-10
IEC 60146
IEC 60255
IEC 60265-1
IEC 60269-1
IEC 60269-2
IEC 60282-1
IEC 60287-1-1
IEC 60364
IEC 60364-1
IEC 60364-4-41
IEC 60364-4-42
IEC 60364-4-43
IEC 60364-4-44
IEC 60364-5-51
IEC 60364-5-52
IEC 60364-5-53
IEC 60364-5-54
IEC 60364-5-55
IEC 60364-6-61
IEC 60364-7-701
IEC 60364-7-702
IEC 60364-7-703
IEC 60364-7-704
IEC 60364-7-705

(Continued on next page)

Schneider Electric - Electrical installation guide 2005

B - General design - Regulations Installed power

2 Rules and statutory regulations

B6

IEC 60947-1
IEC 60947-2
IEC 60947-3
IEC 60947-4-1
IEC 60947-6-1
IEC 61000
IEC 61140
IEC 61557-1
IEC 61557-8
IEC 61557-9
IEC 61558-2-6
IEC 62271-1
IEC 62271-100
IEC 62271-102
IEC 62271-105
IEC 62271-200
IEC 62271-202

ck

IEC 60724
IEC 60755
IEC 60787
IEC 60831

Degrees of protection provided by enclosures (IP code)
Spécification for high-voltage fuse-links for motor circuit applications
Insulation coordination for equipment within low-voltage systems
Dimensions of low-voltage switchgear and controlgear. Standardized mounting on rails for mechanical support of electrical devices in switchgear
and controlgear installations.
Short-circuit temperature limits of electric cables with rated voltages of 1 kV (Um = 1.2 kV) and 3 kV (Um = 3.6 kV)
General requirements for residual current operated protective devices
Application guide for the selection of fuse-links of high-voltage fuses for transformer circuit application
Shunt power capacitors of the self-healing type for AC systems having a rated voltage up to and including 1000 V - General - Performance, testing
and rating - Safety requirements - Guide for installation and operation
Low-voltage switchgear and controlgear - General rules
Low-voltage switchgear and controlgear - Circuit-breakers
Low-voltage switchgear and controlgear - Switches, disconnectors, switch-disconnectors and fuse-combination units
Low-voltage switchgear and controlgear - Contactors and motor-starters - Electromechanical contactors and motor-starters
Low-voltage switchgear and controlgear - Multiple function equipment - Automatic transfer switching equipment
Electromagnetic compatibility (EMC)
Protection against electric shocks - common aspects for installation and equipment
Electrical safety in low-voltage distribution systems up to 1000 V AC and 1500 V DC - Equipment for testing, measuring or monitoring of protective
measures - General requirements
Electrical safety in low-voltage distribution systems up to 1000 V AC and 1500 V DC - Equipment for testing, measuring or monitoring of protective
measures
Electrical safety in low-voltage distribution systems up to 1000 V AC and 1500 V DC - Equipment for insulation fault location in IT systems
Safety of power transformers, power supply units and similar - Particular requirements for safety isolating transformers for general use
Common specifications for high-voltage switchgear and controlgear standards
High-voltage switchgear and controlgear - High-voltage alternating-current circuit-breakers
High-voltage switchgear and controlgear - Alternating current disconnectors and earthing switches
High-voltage switchgear and controlgear - Alternating current switch-fuse combinations
High-voltage switchgear and controlgear - Alternating current metal-enclosed switchgear and controlgear for rated voltages above 1 kV and up to
and including 52 kV
High-voltage/low voltage prefabricated substations
Ba

IEC 60529
IEC 60644
IEC 60664
IEC 60715

(Concluded)

2.4 Quality and safety of an electrical installation
In so far as control procedures are respected, quality and safety will be assured
only if:
c The initial checking of conformity of the electrical installation with the standard and
regulation has been achieved
c The electrical equipment comply with standards
c The periodic checking of the installation recommended by the equipment
manufacturer are respected.

2.5 Initial testing of an installation
Before a utility will connect an installation to its supply network, strict precommissioning electrical tests and visual inspections by the authority, or by its
appointed agent, must be satisfied.
These tests are made according to local (governmental and/or institutional)
regulations, which may differ slightly from one country to another. The principles of
all such regulations however, are common, and are based on the observance of
rigorous safety rules in the design and realization of the installation.
IEC 60364-6-61 and related standards included in this guide are based on an
international consensus for such tests, intended to cover all the safety measures and
approved installation practices normally required for domestic, commercial and (the
majority of) industrial buildings. Many industries however have additional regulations
related to a particular product (petroleum, coal, natural gas, etc.). Such additional
requirements are beyond the scope of this guide.
The pre-commissioning electrical tests and visual-inspection checks for installations
in buildings include, typically, all of the following:
c Insulation tests of all cable and wiring conductors of the fixed installation, between
phases and between phases and earth
c Continuity and conductivity tests of protective, equipotential and earth-bonding
conductors
c Resistance tests of earthing electrodes with respect to remote earth
c Verification of the proper operation of the interlocks, if any
c Allowable number of socket-outlets per circuit check

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2 Rules and statutory regulations
B7

c Cross-sectional-area check of all conductors for adequacy at the short-circuit
levels prevailing, taking account of the associated protective devices, materials and
installation conditions (in air, conduit, etc.)
c Verification that all exposed- and extraneous metallic parts are properly earthed
(where appropriate)
c Check of clearance distances in bathrooms, etc.
These tests and checks are basic (but not exhaustive) to the majority of installations,
while numerous other tests and rules are included in the regulations to cover
particular cases, for example: TN-, TT- or IT-earthed installations, installations based
on class 2 insulation, SELV circuits, and special locations, etc.
The aim of this guide is to draw attention to the particular features of different types
of installation, and to indicate the essential rules to be observed in order to achieve a
satisfactory level of quality, which will ensure safe and trouble-free performance. The
methods recommended in this guide, modified if necessary to comply with any
possible variation imposed by a utility, are intended to satisfy all precommissioning
test and inspection requirements.

2.6 Periodic check-testing of an installation
In many countries, all industrial and commercial-building installations, together with
installations in buildings used for public gatherings, must be re-tested periodically by
authorized agents.
Figure B3 shows the frequency of testing commonly prescribed according to the
kind of installation concerned.

Ba

ck

Type of installation
Installations which
require the protection
of employees

Installations in buildings
used for public gatherings,
where protection against
the risks of fire and panic
are required
Residential

c Locations at which a risk of degradation,
fire or explosion exists
c Temporary installations at worksites
c Locations at which HV installations exist
c Restrictive conducting locations
where mobile equipment is used
Other cases
According to the type of establishment
and its capacity for receiving the public

Testing
frequency
Annually

Every 3 years
From one to
three years

According to local regulations

Fig B3 : Frequency of check-tests commonly recommended for an electrical installation

Conformity of equipment with the relevant
standards can be attested in several ways

2.7 Conformity (with standards and specifications)
of equipment used in the installation
Attestation of conformity
The conformity of equipment with the relevant standards can be attested:
c By an official mark of conformity granted by the certification body concerned, or
c By a certificate of conformity issued by a certification body, or
c By a declaration of conformity from the manufacturer
The first two solutions are generally not available for high voltage equipment.

Declaration of conformity
Where the equipment is to be used by skilled or instructed persons, the
manufacturer’s declaration of conformity (included in the technical documentation), is
generally recognized as a valid attestation. Where the competence of the
manufacturer is in doubt, a certificate of conformity can reinforce the manufacturer’s
declaration.

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2 Rules and statutory regulations

B8

Note: CE marking
In Europe, the European directives require the manufacturer or his authorized
representative to affix the CE marking on his own responsibility. It means that:
c The product meets the legal requirements
c It is presumed to be marketable in Europe
The CE marking is neither a mark of origin nor a mark of conformity.

Mark of conformity
Marks of conformity are affixed on appliances and equipment generally used by
ordinary non instructed persons (e.g in the field of domestic appliances). A mark of
conformity is delivered by certification body if the equipment meet the requirements
from an applicable standard and after verification of the manufacture’s quality
management system.

Certification of Quality
The standards define several methods of quality assurance which correspond to
different situations rather than to different levels of quality.

Assurance
A laboratory for testing samples cannot certify the conformity of an entire production
run:
These tests are called type tests. In some tests for conformity to standards,
the samples are destroyed (tests on fuses, for example).
Only the manufacturer can certify that the fabricated products have, in fact,
the characteristics stated.
Quality assurance certification is intended to complete the initial declaration or
certification of conformity.
As proof that all the necessary measures have been taken for assuring the quality of
production, the manufacturer obtains certification of the quality control system which
monitors the fabrication of the product concerned. These certificates are issued by
organizations specializing in quality control, and are based on the international
standard ISO 9000.
These standards define three model systems of quality assurance control
corresponding to different situations rather than to different levels of quality:
c Model 3 defines assurance of quality by inspection and checking of final products.
c Model 2 includes, in addition to checking of the final product, verification of the
manufacturing process. For example, this method is applied, to the manufacturer of
fuses where performance characteristics cannot be checked without destroying the
fuse.
c Model 1 corresponds to model 2, but with the additional requirement that the
quality of the design process must be rigorously scrutinized; for example, where it is
not intended to fabricate and test a prototype (case of a custom-built product made to
specification).

2.8 Environment
Environmental management systems can be certified by an independent body if they
meet requirements given in ISO 14001. This type of certification mainly concerns
industrial settings but can also be granted to places where products are designed.
A product environmental design sometimes called “eco-design” is an approach of
sustainable development with the objective of designing products/services best
meeting the customers’ requirements while reducing their environmental impact over
their whole life cycle. The methodologies used for this purpose lead to choose
equipment’s architecture together with components and materials taking into account
the influence of a product on the environment along its life cycle (from extraction of
raw materials to grave) i.e. production, transport, distribution, end of life etc.
In Europe two Directives have been published, they are called:
c RoHS Directive (Restriction of Hazardous Substances) coming into force on July
2006 (the coming into force was on February 13th, 2003, and the application date is
July 1st, 2006) aims to eliminate from products six hazardous substances: lead,
mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB) or
polybrominated diphenyl ethers (PBDE).

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B9

c WEEE Directive (Waste of Electrical and Electronic Equipment) coming into force
in August 2005 2006 (the coming into force was on February 13th, 2003, and the
application date is August 13th, 2005) in order to master the end of life and
treatments for household and non household equipment.
In other parts of the world some new legislation will follow the same objectives.
In addition to manufacturers action in favour of products eco-design, the contribution
of the whole electrical installation to sustainable development can be significantly
improved through the design of the installation. Actually, it has been shown that an
optimised design of the installation, taking into account operation conditions, MV/LV
substations location and distribution structure (switchboards, busways, cables), can
reduce substantially environmental impacts (raw material depletion, energy
depletion, end of life)
See chapter E about location of the substation and the main LV switchboard.

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3 Installed power loads Characteristics

B10

The examination of actual values of apparent-power required by each load enables
the establishment of:

An examination of the actual apparent-power
demands of different loads: a necessary
preliminary step in the design of a
LV installation

c A declared power demand which determines the contract for the supply of energy
c The rating of the HV/LV transformer, where applicable (allowing for expected
increased load)
c Levels of load current at each distribution board

The nominal power in kW (Pn) of a motor
indicates its rated equivalent mechanical power
output.
The apparent power in kVA (Pa) supplied to the
motor is a function of the output, the motor
efficiency and the power factor.
Pn
Pa =
ηcosϕ

3.1 Induction motors
Current demand
The full-load current Ia supplied to the motor is given by the following formulae:
c 3-phase motor: Ia = Pn x 1,000 / (√3 x U x η x cos ϕ)
c 1-phase motor: Ia = Pn x 1,000 / (U x η x cos ϕ)
where
Ia: current demand (in amps)
Pn: nominal power (in kW)
U: voltage between phases for 3-phase motors and voltage between the terminals
for single-phase motors (in volts). A single-phase motor may be connected phase-toneutral or phase-to-phase.
η: per-unit efficiency, i.e. output kW / input kW
cos ϕ: power factor, i.e. kW input / kVA input

Subtransient current and protection setting
c Subtransient current peak value can be very high ; typical value is about 12
to 15 times the rms rated value Inm. Sometimes this value can reach 25 times Inm.
c Merlin Gerin circuit breakers, Telemecanique contactors and thermal relays are
designed to withstand motor starts with very high subtransient current (subtransient
peak value can be up to 19 times the rms rated value Inm).
c If unexpected tripping of the overcurrent protection occurs during starting, this
means the starting current exceeds the normal limits. As a result, some maximum
switchgear withstands can be reached, life time can be reduced and even some
devices can be destroyed. In order to avoid such a situation, oversizing of the
switchgear must be considered.
c Merlin Gerin and Telemecanique switchgears are designed to ensure the
protection of motor starters against short circuits. According to the risk, tables show
the combination of circuit breaker, contactor and thermal relay to obtain type 1 or
type 2 coordination (see chapter M).

Motor starting current
Although high efficiency motors can be found on the market, in practice their starting
currents are roughly the same as some of standard motors.
The use of start-delta starter, static soft start unit or variable speed drive allows to
reduce the value of the starting current (Example : 4 Ia instead of 7.5 Ia).

Compensation of reactive-power (kvar) supplied to induction motors
It is generally advantageous for technical and financial reasons to reduce the current
supplied to induction motors. This can be achieved by using capacitors without
affecting the power output of the motors.
The application of this principle to the operation of induction motors is generally
referred to as “power-factor improvement” or “power-factor correction”.
As discussed in chapter K, the apparent power (kVA) supplied to an induction motor
can be significantly reduced by the use of shunt-connected capacitors. Reduction of
input kVA means a corresponding reduction of input current (since the voltage
remains constant).
Compensation of reactive-power is particularly advised for motors that operate for
long periods at reduced power.

kW input
so that a kVA input reduction will increase (i.e.
kVA input
improve) the value of cos ϕ.
As noted above cos ϕ =

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3 Installed power loads Characteristics
B11

The current supplied to the motor, after power-factor correction, is given by:

I = Ia

cos ϕ
cos ϕ'

where cos ϕ is the power factor before compensation and cos ϕ’ is the power factor
after compensation, Ia being the original current.
Figure B4 below shows, in function of motor rated power, standard motor current
values for several voltage supplies.

Ba

ck

kW

hp

230 V

0.18
0.25
0.37
0.55
0.75
1.1
1.5
2.2
3.0
3.7
4
5.5
7.5
11
15
18.5
22
30
37
45
55
75
90
110
132
150
160
185
200
220
250
280
300

1/2
3/4
1
1-1/2
2
3
7-1/2
10
15
20
25
30
40
50
60
75
100
125
150
200
250
300
350
400
-

A
1.0
1.5
1.9
2.6
3.3
4.7
6.3
8.5
11.3
15
20
27
38.0
51
61
72
96
115
140
169
230
278
340
400
487
609
748
-

380 415 V
A
1.3
1.8
2.3
3.3
4.3
6.1
9.7
14.0
18.0
27.0
34.0
44
51
66
83
103
128
165
208
240
320
403
482
560
636
-

400 V
A
0.6
0.85
1.1
1.5
1.9
2.7
3.6
4.9
6.5
8.5
11.5
15.5
22.0
29
35
41
55
66
80
97
132
160
195
230
280
350
430
-

440 480 V
A
1.1
1.6
2.1
3.0
3.4
4.8
7.6
11.0
14.0
21.0
27.0
34
40
52
65
77
96
124
156
180
240
302
361
414
474
-

500 V

690 V

A
0.48
0.68
0.88
1.2
1.5
2.2
2.9
3.9
5.2
6.8
9.2
12.4
17.6
23
28
33
44
53
64
78
106
128
156
184
224
280
344
-

A
0.35
0.49
0.64
0.87
1.1
1.6
2.1
2.8
3.8
4.9
6.7
8.9
12.8
17
21

Fig. B4 : Rated operational power and currents (continued on next page)

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24
32
39
47
57
77
93
113
134
162
203
250
-

B - General design - Regulations Installed power

3 Installed power loads Characteristics

Ba

ck

B12

kW

hp

230 V

315
335
355
375
400
425
450
475
500
530
560
600
630
670
710
750
800
850
900
950
1000

540
500
-

A
940
1061
1200
1478
1652
1844
2070
2340
2640
2910

380 415 V
A
786
-

400 V

440 480 V
A
515
590
-

A
540
610
690
850
950
1060
1190
1346
1518
1673

500 V

690 V

A
432
488
552
680
760
848
952
1076
1214
1339

A
313
354
400
493
551
615
690
780
880
970

Fig. B4 : Rated operational power and currents (concluded)

3.2 Resistive-type heating appliances and
incandescent lamps (conventional or halogen)
The current demand of a heating appliance or an incandescent lamp is easily
obtained from the nominal power Pn quoted by the manufacturer (i.e. cos ϕ = 1)
(see Fig. B5 ).

Ba

ck

Nominal
power
(kW)
0.1
0.2
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
6
7
8
9
10

Current demand (A)
1-phase 1-phase
127 V
230 V
0.79
0.43
1.58
0.87
3.94
2.17
7.9
4.35
11.8
6.52
15.8
8.70
19.7
10.9
23.6
13
27.6
15.2
31.5
17.4
35.4
19.6
39.4
21.7
47.2
26.1
55.1
30.4
63
34.8
71
39.1
79
43.5

3-phase
230 V
0.25
0.50
1.26
2.51
3.77
5.02
6.28
7.53
8.72
10
11.3
12.6
15.1
17.6
20.1
22.6
25.1

3-phase
400 V
0.14
0.29
0.72
1.44
2.17
2.89
3.61
4.33
5.05
5.77
6.5
7.22
8.66
10.1
11.5
13
14.4

Fig. B5 : Current demands of resistive heating and incandescent lighting (conventional or
halogen) appliances

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3 Installed power loads Characteristics
B13

The currents are given by:
c 3-phase case: I a =

Pn

(1)

3U

Pn (1)
c 1-phase case: I a =
U
where U is the voltage between the terminals of the equipment.

For an incandescent lamp, the use of halogen gas allows a more concentrated light
source. The light output is increased and the lifetime of the lamp is doubled.
Note: At the instant of switching on, the cold filament gives rise to a very brief but
intense peak of current.

Fluorescent lamps and related equipment
The power Pn (watts) indicated on the tube of a fluorescent lamp does not include
the power dissipated in the ballast.
The current is given by:

Ia =

Pballast + Pn
U cos ϕ

Where U = the voltage applied to the lamp, complete with its related equipment.
If no power-loss value is indicated for the ballast, a figure of 25% of Pn may be used.

Standard tubular fluorescent lamps
With (unless otherwise indicated):
c cos ϕ = 0.6 with no power factor (PF) correction(2) capacitor
c cos ϕ = 0.86 with PF correction(2) (single or twin tubes)
c cos ϕ = 0.96 for electronic ballast.
If no power-loss value is indicated for the ballast, a figure of 25% of Pn may be used.
Figure B6 gives these values for different arrangements of ballast.

Ba

c k Arrangement

Tube power
of lamps, starters (W) (3)
and ballasts

Single tube

18
36
58
Twin tubes
2 x 18
2 x 36
2 x 58
(3) Power in watts marked on tube

Current (A) at 230 V
Magnetic ballast
Without PF
correction
capacitor
0.20
0.33
0.50

With PF
correction
capacitor
0.14
0.23
0.36
0.28
0.46
0.72

Electronic
ballast

Tube
length
(cm)

0.10
0.18
0.28
0.18
0.35
0.52

60
120
150
60
120
150

Fig. B6 : Current demands and power consumption of commonly-dimensioned fluorescent
lighting tubes (at 230 V-50 Hz)

Compact fluorescent lamps
Compact fluorescent lamps have the same characteristics of economy and long life
as classical tubes. They are commonly used in public places which are permanently
illuminated (for example: corridors, hallways, bars, etc.) and can be mounted in
situations otherwise illuminated by incandescent lamps (see Fig. B7 next page).

(1) Ia in amps; U in volts. Pn is in watts. If Pn is in kW, then
multiply the equation by 1,000
(2) “Power-factor correction” is often referred to as
“compensation” in discharge-lighting-tube terminology.
Cos ϕ is approximately 0.95 (the zero values of V and I are
almost in phase) but the power factor is 0.5 due to the
impulsive form of the current, the peak of which occurs “late”
in each half cycle
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B14

Ba

ck

Type of lamp
Separated
ballast lamp
Integrated
ballast lamp

Lamp power
(W)
10
18
26
8
11
16
21

Current at 230 V
(A)
0.080
0.110
0.150
0.075
0.095
0.125
0.170

Fig. B7 : Current demands and power consumption of compact fluorescent lamps (at 230 V - 50 Hz)

Discharge lamps

The power in watts indicated on the tube of a
discharge lamp does not include the power
dissipated in the ballast.

Figure B8 gives the current taken by a complete unit, including all associated
ancillary equipment.
These lamps depend on the luminous electrical discharge through a gas or vapour of
a metallic compound, which is contained in a hermetically-sealed transparent
envelope at a pre-determined pressure. These lamps have a long start-up time,
during which the current Ia is greater than the nominal current In. Power and current
demands are given for different types of lamp (typical average values which may
differ slightly from one manufacturer to another).

Ba

ck

Power
Current In(A)
demand
PF not
(W) at
corrected
230 V 400 V 230 V 400 V
High-pressure sodium vapour lamps
50
60
0.76
70
80
1
100
115
1.2
150
168
1.8
250
274
3
400
431
4.4
1000
1055
10.45
Low-pressure sodium vapour lamps
26
34.5
0.45
36
46.5
66
80.5
91
105.5
131
154
Type of
lamp (W)

Starting
PF
Ia/In
corrected
230 V 400 V

Period
(mins)

Luminous
efficiency
(lumens
per watt)

Average
timelife of
lamp (h)

Utilization

0.3
0.45
0.65
0.85
1.4
2.2
4.9

1.4 to 1.6 4 to 6

80 to 120

9000

c Lighting of
large halls
c Outdoor spaces
c Public lighting

0.17
0.22
0.39
0.49
0.69

1.1 to 1.3 7 to 15

100 to 200

8000
to 12000

c Lighting of
autoroutes
c Security lighting,
station
c Platform, storage
areas

Mercury vapour + metal halide (also called metal-iodide)
70
80.5
1
0.40
1.7
3 to 5
70 to 90
6000
c Lighting of very
150
172
1.80
0.88
6000
large areas by
250
276
2.10
1.35
6000
projectors (for
400
425
3.40
2.15
6000
example: sports
1000
1046
8.25
5.30
6000
stadiums, etc.)
2000
2092 2052 16.50 8.60 10.50 6
2000
Mercury vapour + fluorescent substance (fluorescent bulb)
50
57
0.6
0.30
1.7 to 2
3 to 6
40 to 60
8000
c Workshops
80
90
0.8
0.45
to 12000
with very high
125
141
1.15
0.70
ceilings (halls,
250
268
2.15
1.35
hangars)
400
421
3.25
2.15
c Outdoor lighting
700
731
5.4
3.85
c Low light output(1)
1000
1046
8.25
5.30
2000
2140 2080 15
11
6.1
(1) Replaced by sodium vapour lamps.
Note: these lamps are sensitive to voltage dips. They extinguish if the voltage falls to less than 50% of their nominal voltage, and will
not re-ignite before cooling for approximately 4 minutes.
Note: Sodium vapour low-pressure lamps have a light-output efficiency which is superior to that of all other sources. However, use of
these lamps is restricted by the fact that the yellow-orange colour emitted makes colour recognition practically impossible.

Fig. B8 : Current demands of discharge lamps

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B - General design - Regulations Installed power

4 Power loading of an installation
B15

In order to design an installation, the actual maximum load demand likely to be
imposed on the power-supply system must be assessed.
To base the design simply on the arithmetic sum of all the loads existing in the
installation would be extravagantly uneconomical, and bad engineering practice.
The aim of this chapter is to show how some factors taking into account the diversity
(non simultaneous operation of all appliances of a given group) and utilization (e.g.
an electric motor is not generally operated at its full-load capability, etc.) of all
existing and projected loads can be assessed. The values given are 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
(distribution network, HV/LV transformer, or generating set) can be specified.

4.1 Installed power (kW)
The installed power is the sum of the nominal
powers of all power consuming devices in the
installation.
This is not the power to be actually supplied in
practice.

Most electrical appliances and equipments are marked to indicate their nominal
power rating (Pn).
The installed power is the sum of the nominal powers of all power-consuming
devices in the installation. This is not the power to be actually supplied in practice.
This is the case for electric motors, where the power rating refers to the output
power at its driving shaft. The input power consumption will evidently be greater
Fluorescent and discharge lamps associated with stabilizing ballasts, are other
cases in which the nominal power indicated on the lamp is less than the power
consumed by the lamp and its ballast.
Methods of assessing the actual power consumption of motors and lighting
appliances are given in Section 3 of this Chapter.
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,
the significant quantity is the apparent power in kVA.

4.2 Installed apparent power (kVA)
The installed apparent power is commonly
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.

The installed apparent power is commonly 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.
The apparent-power demand of a load (which might be a single appliance) is
obtained from its nominal power rating (corrected if necessary, as noted above for
motors, etc.) and the application of the following coefficients:

η = the per-unit efficiency = output kW / input kW
cos ϕ = the power factor = kW / kVA
The apparent-power kVA demand of the load
Pa = Pn /(η x cos ϕ)
From this value, the full-load current Ia (A)(1) taken by the load will be:
Pa x 103
V
for single phase-to-neutral connected load

c Ia =

Pa x 103
3xU
for three-phase balanced load where:
V = phase-to-neutral voltage (volts)
U = phase-to-phase voltage (volts)
It may be noted that, strictly speaking, the total kVA of apparent power is not the
arithmetical sum of the calculated kVA ratings of individual loads (unless all loads
are at the same power factor).
It is common practice however, to make a simple arithmetical summation, the result
of which will give a kVA value that exceeds the true value by an acceptable “design
margin”.
When some or all of the load characteristics are not known, the values shown in
Figure B9 next page 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.

c Ia =

(1) For greater precision, account must be taken of the factor
of maximum utilization as explained below in 4.3
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4 Power loading of an installation

Ba

ck

B16

Fluorescent lighting (corrected to cos ϕ = 0.86)
Type of application
Estimated (VA/m2)
Average lighting
fluorescent tube
level (lux = lm/m2)
with industrial reflector(1)
Roads and highways
7
150
stockage 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:
115 to 146
private houses 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. B9 : 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.

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.

Factor of simultaneity (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 simultaneity factor (ks).
The 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.

Factor of simultaneity for an apartment block
Some typical values for this case are given in Figure B10 opposite page, and are
applicable to domestic consumers 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.

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4 Power loading of an installation

ck

B17

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

Ba

B - General design - Regulations Installed power

Factor of
simultaneity (ks)
1
0.78
0.63
0.53
0.49
0.46
0.44
0.42
0.41
0.40

Fig. B10 : Simultaneity factors in a apartment block

Example (see Fig. B11) :
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 B10, 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:
150 x 0.46 x 103

= 100 A
400 3
the current entering the third floor is:

(36 + 24) x 0.63 x 103
400

Ba

3

= 55 A

ck

4th
floor

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

0.78

0.63

0.53

0.49

0.46

Fig. B11 : Application of the factor of simultaneity (ks) to an apartment block of 5 storeys

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4 Power loading of an installation

B18

Factor of simultaneity for distribution boards
Figure B12 shows hypothetical values of ks for a distribution board supplying a
number of circuits for which there is no indication of the manner in which the total
load divides between them.
If the circuits are mainly for lighting loads, it is prudent to adopt ks values close to
unity.

Ba

ck

Number of
circuits
Assemblies entirely tested
2 and 3
4 and 5
6 to 9
10 and more
Assemblies partially tested
in every case choose

Factor of
simultaneity (ks)
0.9
0.8
0.7
0.6
1.0

Fig. B12 : Factor of simultaneity for distribution boards (IEC 60439)

Factor of simultaneity according to circuit function
ks factors which may be used for circuits supplying commonly-occurring loads, are
shown in Figure B13 .

ck
B a Circuit function

Factor of simultaneity (ks)
Lighting
1
Heating and air conditioning
1
Socket-outlets
0.1 to 0.2 (1)
10 and more
0.6
Lifts and catering hoist (2) c For the most powerful
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,
increased by a third of its starting current.

Fig. B13 : Factor of simultaneity according to circuit function

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
installation, from each load position to the point of supply is given Fig. B14 (opposite
page).
In this example, the total installed apparent power is 126.6 kVA, which corresponds
to an actual (estimated) maximum value at the LV terminals of the HV/LV transformer
of 65 kVA only.
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:

I=

kVA x 103
U

3

where kVA is the actual maximum 3-phase apparent-power value shown on the
diagram for the circuit concerned, and U is the phase to- phase voltage (in volts).

4.5 Diversity factor
The term diversity factor, as defined in IEC standards, is identical to the factor of
simultaneity (ks) used in this guide, as described in 4.3. In some English-speaking
countries however (at the time of writing) diversity factor is the inverse of ks i.e. it is
always u 1.
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4 Power loading of an installation

Ba

ck

B19

Level 2

Level 1
Utilization

Level 3

Apparent Utilization Apparent Simultaneity Apparent Simultaneity Apparent Simultaneity Apparent
power
factor
power
factor
power
factor
power factor
power
(Pa)
max.
demand
demand
demand
demand
kVA
max. kVA
kVA
kVA
kVA

Workshop A Lathe

no. 1

5

0.8

4

no. 2

5

0.8

4

no. 3

5

0.8

4

no. 4

5

0.8

4

2

0.8

1.6

2

0.8

1.6

18

1

18

0.2

3.6

3

1

3

1

3

15

0.8

12

1

12 Socket4.3
1

Pedestalno. 1
drill
no. 2

5 socketoutlets 10/16 A
30 fluorescent
lamps
Workshop B Compressor
3 socketoutlets 10/16 A

Distribution
box

0.75

Power
circuit

14.4

10.6

1

10.6

1

1

1

1

Workshop C Ventilation no. 1

2.5

1

2.5

no. 2

2.5

1

2.5

Distribution
box

no. 1

15

1

15

no. 2
5 socketoutlets 10/16 A

15

1

15

18

1

18

0.28

5

2

1

2

1

2

10 fluorescent
lamps

1
Oven

20 fluorescent
lamps

0.9

Socketoulets
Lighting
circuit

Power
circuit

0.4

Workshop A
distribution
box

oulets

Workshop B
distribution
box

18.9

Main
general
distribution
board
MGDB

LV / HV

15.6

65
0.9

Lighting
circuit

0.9

Workshop C
distribution

35

Powver
box
circuit

0.9

37.8

Socketoulets
Lighting
circuit

Fig B14 : An example in estimating the maximum predicted loading of an installation (the factor values used are for demonstration purposes only)

4.6 Choice of transformer rating
When an installation is to be supplied directly from a HV/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 of the following
considerations (see Fig. B15 ):
c The possibility of improving the power factor of the installation (see chapter K)
c Anticipated extensions to the installation
c Installation constraints (e.g. temperature)
c Standard transformer ratings

Ba

ck

Apparent power
kVA
100
160
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150

In (A)
237 V
244
390
609
767
974
1218
1535
1949
2436
3045
3898
4872
6090
7673

410 V
141
225
352
444
563
704
887
1127
1408
1760
2253
2816
3520
4436

Fig. B15 : Standard apparent powers for HV/LV transformers and related nominal output
currents

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4 Power loading of an installation

B20

The nominal full-load current In on the LV side of a 3-phase transformer is given by:

In =

Pa x 103
U

3

where
c Pa = kVA rating of the transformer
c U = phase-to-phase voltage at no-load in volts (237 V or 410 V)
c In is in amperes.
For a single-phase transformer:
Pa x 103
V
where

In =

c V = voltage between LV terminals at no-load (in volts)
Simplified equation for 400 V (3-phase load)
c In = kVA x 1.4
The IEC standard for power transformers is IEC 60076.

4.7 Choice of power-supply sources
The study developed in E1 on 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 described in E1.4.
For the main source of supply the choice is generally between a connection to the
HV or the LV network of the power-supply utility.
In practice, connection to a HV 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 HV service.
Supplies at HV can have certain advantages: in fact, a HV consumer:
c Is not disturbed by other consumers, which could be the case at LV
c Is free to choose any type of LV earthing system
c Has a wider choice of economic tariffs
c Can accept very large increases in load
It should be noted, however, that:
c The consumer is the owner of the HV/LV substation and, in some countries,
he must build and equip it at his own expense. The power utility can, in certain
circumstances, participate in the investment, at the level of the HV line for example
c A part of the connection costs can, for instance, often be recovered if a second
consumer is connected to the HV line within a certain time following the original
consumer’s own connection
c The consumer has access only to the LV part of the installation, access to the
HV 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

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5 Power monitoring and control
B21

Power monitoring and control system may be of high benefice for the operator or the
owner of an electrical network.
Companies are moving faster and faster, the use of building facilities either.
An electrical network has then to face successive generation of needs, which will
lead to many load evolutions but also certainly to “associated services” evolutions for example, tracking the costs due to higher level of competition.
Even if the decision is to invest later, the design of the network has to take into
account that using a monitoring system will happen eventually, and then it will be a
competitive advantage if the Equipment has anticipated its integration.
Nowadays, entering the “Power monitoring and control” approach doesn’t mean
setting-up a complex and expensive system.
Some simplest features are really affordable with a very good payback because they
can be directly embedded in your Power Equipment.
Such system may simply share the communication medium of the user’s Intranet site.
In addition operation won’t ask specific skills and training. It will only require the use
of license-free software such as Intranet browsers.
Upgradability is also now a reality, based on new technologies that come for the
Office and Communication world (you can now run multiple protocols on the same
medium, the legacy and the new one). Then being in a position of taking advantages
of these new possibilities will be more and more a differentiating behaviour.

5.1 Main user’s benefits
Power Monitoring and control is possibly interesting for four main reasons:
c It can contribute to field staff efficiency increase
c It can contribute to decrease the cost of Energy
c It may help in optimising and increasing the life duration of the assets associated
to the electrical network
c And finally it may be master piece in increasing the productivity of the associated
process (industrial process or even office, building management), by preventing, or
reducing downtime, or insuring higher quality energy to the loads.

Increase field staff efficiency
One of the big challenges of field staff in charge of the electrical network is to make
the right decision and operate in the minimum time.
The first need of such people is then to better know what happens on the network,
and possibly form everywhere on the concerned site.
This site-wise transparency is a key feature that enables a field staff to :
c Understand the electrical energy flows – check that the network is correctly
balanced, what are the main consumers, at what period of the day, the week…
c Understand the network behaviour – a tripping on a feeder is easier to understand
when you have access to information from downstream loads
c Be spontaneously informed on events, even outside the concerned site by using
today’s mobile communication
c Going straight forward to the right location on the site with the right spare part, and
with the understanding of the complete picture of the network status
c Initiate a maintenance action taking into account the real usage of a device, not too
early and not too late

Decrease the cost of Energy
Power invoice may be a significant expense for companies, but in the same way, not
the one managers are looking at, first.
However, providing to the electrician a way to monitor the electrical network can
appear as a powerful mean to optimise and in certain case drastically reduce the
cost of power.

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5 Power monitoring and control

B22

Here are some examples of the main usage of the simplest monitoring systems :
c Benchmark between zones to detect abnormal consumption
c Track unexpected consumption
c Ensure that power consumption is not higher than your competitors
c Choose the right Power delivery contract with the Power Utility
c Set-up simple load-shedding just focusing on optimising manageable loads such
as lights
c Be in a position to ask for damage compensation due to non-quality delivery from
the Power Utilities (“The process has been stopped because of a sag on the
network”).

Optimising the assets
One increasing fact is that electrical network evolves more and more and then a
recurrent question occurs : Will my network support this new evolution?
This is typically where a Monitoring system can help the network owner in making
the right decision.
By its logging activity, it can archive the real use of the assets and then evaluate
quite accurately the spare capacity of a network, a switchboard, a transformer…

Increasing the life duration of assets
A better use of an asset may increase its life duration.
Monitoring systems can provide accurate information of the exact use of an asset
and then the maintenance team can decide the appropriate maintenance operation,
not too late, or not too early.
In some cases also, the monitoring of harmonics can be a positive factor for the life
duration of some assets (such as motors or transformers).

Increasing the productivity by reducing the downtime
Downtime is the nightmare of any people in charge of an electrical network. It may
cause dramatic loss for the company, and the pressure for powering up again in the
minimum time – and the associated stress for the operator – is very high.
A monitoring and control system can help reducing the downtime very efficiently.
Without speaking of a remote control system which is the most sophisticated system
and which may be necessary for the most demanding application, a monitoring
system can already provide relevant information that will highly contribute in
reducing the downtime:
c Making the operator spontaneously informed, even remote, even out of the
concerned site (Using the mobile communication such as GSM/SMS)
c Providing a global view of the whole network status
c Helping the identification of the faulty zone
c Having remotely the detailed information attached to each events caught by the
field devices (reason for tripping for example)
Then remote control of a device is a must but not necessary mandatory. In many
cases, a visit of the faulty zone is necessary where local actions are possible.

Increasing the productivity by improving the Energy Quality
Some loads can be very sensitive to Electricity un-quality, and operators may face
unexpected situations if the Energy quality is not under control.
Monitoring the Energy quality is then an appropriate way to prevent such event and /
or to fix specific issue.

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5 Power monitoring and control
B23

5.2 From Network Monitoring and Control System
to Intelligent Power Equipment
Traditionally and for years, monitoring and control systems have been centralised
and based on SCADA (Supervisory, Control and Data acquisition) automation
systems.
Deciding on investing in such system – noted (3) in Figure B16 hereunder – was
really reserved for high demanding installation, because either they were big power
consumers, or their process was very sensitive to Power non quality.
Based on automation technology, such systems were very often designed,
customised by a system integrator, and then delivered on site. However the initial
cost, the skills needed to correctly operate such system, and the cost of upgrades to
follow the evolutions of the network may have discouraged potential users to invest.
Then based on a dedicated solution for electrician, the other approach noted (2) is
much more fitting the electrical network specific needs and really increases the
payback of such system. However, due to its centralised architecture, the entree
level cost of such solution may still appear high.
On some sites Type (2) and (3) can cohabit, providing the most accurate information
to the electrician when needed.
Nowadays, a new concept of intelligent Power equipment – noted (1) – is available.
Taking the opportunity of the Web technologies, it has become a truly affordable
solution for most of the users. Moreover the site owner can invest gradually into
more sophisticated monitoring systems.
Level 1 can then be considered as an entering step for going to level 2 or 3, due the
ability of these solutions to co-exist on a site.

Ba

ck

Function
levels
General
purpose
monitoring
system

3

General
purpose
site
monitoring

Eqt gateway
Power
Equipment

Specialised
network
monitoring

Other
utilities

Process

Specialised
monitoring
such as
Power Logic
SMS

2
Eqt server
Power
Equipment
Web browser
standard

1
Basic
monitoring

Eqt server
Intelligent
Power
Equipment

Other
utilities

Standard network

Sensitive electrical networks

Fig B16 : Monitoring system positioning

Schneider Electric - Electrical installation guide 2005

High demanding sites

System
complexity

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5 Power monitoring and control

B24

Intelligent equipment based architecture (see Fig. B17 )
This new architecture has appeared recently due to Web technology capabilities,
and can really be positioned as an entry point into monitoring systems.
Based on Web technologies it takes the maximum benefits of standard
communication services and protocols, and license-free software.
The access to electricity information can be done from everywhere in the site, and
electrical staff can gain a lot in efficiency.
Openness to the Internet is also offered for out of the site services.

Ba

ck

Standard remote
Web browser
Standard local
Web browser

Internet

Intranet (Ethernet/IP)

Equipment server
Gateway

Intelligence Power Equipment

Modbus

1

2

3

Meter 1

Meter 2

Meter 3

Circuit breakers

Fig. B17 : Intelligent equipment architecture

Electrician specialized centralised architecture (see Fig. B18 )
Dedicated to electrician, this architecture is based on a specific supervision
centralised mean that fully match the needs for monitoring an electrical network.
Then it offers naturally a lower level of skill to set up and maintain it – all Electrical
Distribution device are already present in a dedicated library. Finally its purchase
cost is really minimised, due the low level of system integrator effort.

Ba

ck

Dedicated supervisor
for electrician

Modbus (SL or Ethernet/IP)

Communicating Power Equipment

Gateway

Modbus

1

2
Circuit breakers

Fig. B18 : ED specialist monitoring system

Schneider Electric - Electrical installation guide 2005

3

Meter 1

Meter 2

Meter 3

B - General design - Regulations Installed power

5 Power monitoring and control
B25

Conventional general purpose centralised architecture (see Fig. B19 )
Here is a typical architecture based on standard automation pieces such as
SCADA systems, and gateways.
Despite its real efficiency, such architecture suffered from some drawbacks such as :
c The level of skills needed to operate it
c The poor upgradability
c And at the end the risky payback of such solutions
They have however no equivalent for high demanding sites, and appears very
relevant for central operation rooms.

Ba

ck

Conventional
supervisor

Modbus (SL or Ethernet/IP)

Communicating Power Equipment

Gateway

Modbus

1

2

3

Meter 1

Meter 2

Meter 3

Circuit breakers

Fig. B19 : Real-time conventional monitoring and control system

5.3 Typical services possibly brought by intelligent
Equipment compared to other solutions
The objective of this comparison is to help the choice of the appropriate system by
understanding pro and cons of each one (see Fig. B20 ).

Ba

ck

“Intelligent” service
Access to electricity real-time information - local
Access to electricity real-time information - remote
Mobile access to information
Site-wise monitoring (ED network)
Multi-process monitoring
Data logging
Trending
Alarming
Remote control – automated functions
Advanced functions to optimise
the electrical network management
Capabilities
Easiness for use / training for electrician
Affordability (based on Initial cost)
Upgradability to follow network evolutions

Intelligent Power
Equipment
++
++
+++
+
+
+
+
+

ED Specialist
monitoring
+
+++
++
+++

+

+++
+++
+++
+
+++

+++
+++
++

++
++
++

Fig. B20 : Typical services compared to other solutions

Schneider Electric - Electrical installation guide 2005

General purpose
site monitoring
++
+++
+++
++
++
++
+++

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5 Power monitoring and control

B26

5.4 Technical inputs on communicating systems
Here is a quick glossary concerning the main terms used associated to
communication technologies

Communication layer – OSI model
Communication layer concept is useful to understand the communication glossary,
and how these terms can be associated or not.
Referring to the OSI model (see Fig. B21 ), there are 7 communication layers, but all
the communication wording not always refers to the 7 layers. In addition a 8th layer is
sometimes added to describe the application specific domain wording and services.

Ethernet
Ethernet is the common word which designates the IEEE 802.3 standard family.
Ethernet refers to OSI layers 1 and 2 of a communication mean. Ethernet use is not
enough at all to specify a communication mean to interoperate between two devices.
Ethernet 802.3 is usually associated to other words to define others aspects of the
network :
Ethernet 802.3 10 Base T ⇒ means Ethernet 10Mb/s using RJ45 connector

IP
IP means “Internet Protocol”.
However, even if the Internet has been its effective success factor, IP is not
exclusive to the Internet.
IP is also widely used for “internal use” such as on the Intranet, but also in closed
“zone”.
IP is an intermediate communication that enables the communication between two
distant devices, even if between them many successive medium types are used.
The switch from one type to another is totally transparent for the “application”.

RS 485
RS 485 is an electrical standard which defines a balanced serial communication
mean.

Modbus
Modbus is originally a communication protocol set up by the Modicon company.
Now Modbus definition is under the management and property of Modbus-IDA.org
association, an independent and open association whose role is to extend and
ensure Modbus interoperability.
Modbus messaging protocol refers to layer 7 of the OSI model.
It can be associated to different medium :
c Serial Line such as RS 485 and RS 232 standard ⇒ the most usual way for
defining Modbus
c Ethernet (in fact over TCP/IP, over Ethernet)
But Modbus is also capable of going through modem, whatever their type (PSTN,
Radio, GSM, …).

et
M
od
TC bu
P s
Et /IP
he
rn
et

Services

7

Application

X

6

Presentation

5

Session

4

Transport

X

X

3

Network

X

X

2

Frame

X

X

X

X

1

Physical

X

X

X

X

Fig. B21 : OSI layers, from 1 to 8

Et
h
IP ern

8

RS bu
s
48
5
Et
he
rn
et

B

Modbus is now recognized as the de-facto standard for electricity application in the
industry and building fields.

k
ac

X

Web technologies
By such wording we include all the technologies usually used through the Web for :
c Visualising information (HTML files over HTTP/HTTPS protocol)
c Sending mails (SMTP/POP protocol)
c Retrieving/ exchanging files (FTP)
c Managing the network (SNMP)
c Synchronising the device attached to the network (NTP/SNTP)
c ….
These protocol are managed by the IETF, an international association.
Using Web technologies is very often licence-free for the user as there are the basis
of common tool such as Web browsers.

Interoperability
In order to ensure interoperability, at least the 7 OSI layers of communication should
be absolutely compatible between themselves. This means for example that having
two Ethernet (OSI layer 1 and 2) devices doesn’t mean that these devices will interoperate.
Schneider Electric - Electrical installation guide 2005

B - General design - Regulations Installed power

5 Power monitoring and control
B27

5.5 Main constraints to take into account to design
a communicating or intelligent power equipment
Equipment bus choice
Here are the main constraints to evaluate when choosing a communication network :
c Openness and maturity
c Proven ability to run in harsh Electrical environment
c Availability of bus compliant Power Devices with interoperability guarantee
c Level of effort at the Power Equipment interface to make it communicating with the
rest of the system (seamless architecture availability)
c Bus communication accessories to ease the wiring inside the cubicle.
Modbus over serial line is today one of the most stable communication mean in the
Electrical Distribution environment, and compatible with most of 3d party devices.
It has also been chosen by most of the manufacturers as their preferred network.
Its easy and seamless openness to Ethernet is a guarantee for easy integration into
the rest of the system. It can also been seen as an easy way for upgrading in the
future, without impact on connected applications.

Equipment bus topology
Equipment bus topology must be flexible enough to be spread on the Equipment
structure.
What is also important is the disconnectability of sections within the power
equipment for transportation.
Usually there are needs of (impedance) termination at the ends of the bus.
The higher the bus speed is, the more sensitive to wiring, terminations and
grounding, the bus is.

Front communication socket
In order to ease the work of operators, introducing a socket on the front door of the
equipment may be of great benefit.
This option will be even more effective if from this switchboard, the operator can not
only have access to information related to the connected power Equipment, but also
to the rest of the site (for exemple downstream or upstream switchboard).

Auxiliary power
In the same way as communication bus, auxiliary power has to be distributed to the
main Power devices. Isolated Auxiliary DC Power is usually required.
Its distribution may be merged with the communication means : the same cable
includes communication and auxiliary power.

Communication accessories
Communication accessories may be necessary to ease the wiring and the
maintenance of the switchboard. It then offers higher ease of reading and
understanding the internal wiring of the switchboard. It may also make possible the
disconnection of a communicating device, on line.

Electrical measurement options
Measurement is one of the foundation of Power monitoring. It may appear in the
future as a systematically required feature.
There are mainly two basic concepts for introducing measurement into a Power
Equipment :
c Implement TCs on cable or busbar. This may take space but this is the only
solution for retrofitting an installation.
c Use multifunction protection relays that possibly embed such feature and which
are upgradable in that sense.
Even if todays’ requirement doesn’t ask for measurement, making some provisions
for introducing it later makes a lot of sense : either choosing power devices that can
evolve to measurement inside devices, or reserve the necessary space for adding
CTs eventually.

Schneider Electric - Electrical installation guide 2005

Chapter C
Connection to the HV utility
distribution network
C1

Contents

1
2
3
4
5
6

Supply of power at high voltage

C2

1.1 Power supply characteristics of high voltage
utility distribution network

C2

1.2 Different HV service connections

C11

1.3 Some operational aspects of HV distribution networks

C12

Procedure for the establishment of a new substation

C14

2.1 Preliminary informations

C14

2.2 Project studies

C15

2.3 Implementation

C15

2.4 Commissioning

C15

Protection aspect

C16

3.1 Protection against electric shocks

C16

3.2 Protection of transformer and circuits

C17

3.3 Interlocks and conditioned operations

C19

The consumer substation with LV metering

C22

4.1 General

C22

4.2 Choice of panels

C22

4.3 Choice of HV switchgear panel for a transformer circuit

C25

4.4 Choice of MV/LV transformer

C25

The consumer substation with HV metering

C30

5.1 General

C30

5.2 Choice of panels

C32

5.3 Parallel operation of transformers

C33

Constitution of HV/LV distribution substations

C35

6.1 Different types of substation

C35

6.2 Indoor substation

C35

6.3 Outdoor substation

C37

Schneider Electric - Electrical installation guide 2005

C - Connection to the HV public
distribution network

1 Supply of power at high voltage

C2

At present there is no international agreement on precise limits to define “High”
voltage.
Voltage levels which are designated as “high” in some countries are referred to as
“medium” in others.
In this chapter, distribution networks which operate at voltages of 1,000 V or less are
referred to as Low-Voltage systems, while systems of power distribution which
require one stage of stepdown voltage transformation, in order to feed into low
voltage networks, will be referred to as High- Voltage systems.
For economic and technical reasons the nominal voltage of high-voltage distribution
systems, as defined above, seldom exceeds 35 kV.

The main features which characterize a powersupply system include:
c The nominal voltage and related insulation
levels
c The short-circuit current
c The rated normal current of items of plant
and equipment
c The earthing system

1.1 Power supply characteristics of high voltage
utility distribution network
Nominal voltage and related insulation levels
The nominal voltage of a system or of an equipment is defined in IEC 60038 as “the
voltage by which a system or equipment is designated and to which certain
operating characteristics are referred”. Closely related to the nominal voltage is the
“highest voltage for equipment” which concerns the level of insulation at normal
working frequency, and to which other characteristics may be referred in relevant
equipment recommendations.
The “highest voltage for equipment” is defined in IEC 60038 as:
“the maximum value of voltage for which equipment may be used, that occurs under
normal operating conditions at any time and at any point on the system. It excludes
voltage transients, such as those due to system switching, and temporary voltage
variations”.
Notes:
1- The highest voltage for equipment is indicated for nominal system voltages higher
than 1,000 V only. It is understood that, particularly for certain nominal system
voltages, normal operation of equipment cannot be ensured up to this highest voltage
for equipment, having regard to voltage sensitive characteristics such as losses of
capacitors, magnetizing current of transformers, etc. In such cases, IEC standards
specify the limit to which the normal operation of this equipment can be ensured.
2- It is understood that the equipment to be used in systems having nominal voltage
not exceeding 1,000 V should be specified with reference to the nominal system
voltage only, both for operation and for insulation.
3- The definition for “highest voltage for equipment” given in IEC 60038 is identical to
the definition given in IEC 60694 for “rated voltage”. IEC 60694 concerns switchgear
for voltages exceeding 1,000 V.
The following values of Figure C1 , taken from IEC 60038, list the most-commonly
used standard levels of high-voltage distribution, and relate the nominal voltages to
corresponding standard values of “Highest Voltage for Equipment”.
These systems are generally three-wire systems unless otherwise indicated. The
values shown are voltages between phases.
The values indicated in parentheses should be considered as non-preferred values.
It is recommended that these values should not be used for new systems to be
constructed in future.

Ba

ck

Series I (for 50 Hz and 60 Hz networks)
Nominal system voltage
Highest voltage for equipement
(kV)
(kV)
3.3 (1)
3 (1)
3.6 (1)
6.6 (1)
6 (1)
7.2 (1)
11
10
12
15
17.5
22
20
24
33 (2)
36 (2)
35 (2)
40.5 (2)
(1) These values should not be used for public distribution systems.
(2) The unification of these values is under consideration.

Fig. C1 : Relation between nominal system voltages and highest voltages for the equipment

Schneider Electric - Electrical installation guide 2005

C - Connection to the HV public
distribution network

1 Supply of power at high voltage

It is recommended that in any one country the ratio between two adjacent nominal
voltages should be not less than two.
In order to ensure adequate protection of equipment against abnormally-high short
term power-frequency overvoltages, and transient overvoltages caused by lightning,
switching, and system fault conditions, etc. all HV equipment must be specified to
have appropriate Rated Insulation Levels.
Switchgear
Figure C2 shown below, is extracted from IEC 60694 and lists standard values of
“withstand” voltage requirements. The choice between List 1 and List 2 values of
table C2 depends on the degree of exposure to lightning and switching
overvoltages(1), the type of neutral earthing, and the type of overvoltage protection
devices, etc. (for further guidance reference should be made to IEC 60071).

Ba

ck

Rated
voltage
U (r.m.s.
value)

Rated lightning impulse withstand voltage
(peak value)

Rated short-duration
power-frequency
withstand voltage
(r.m.s. value)

List 1
List 2
To earth,
Across the To earth,
Across the To earth,
Across the
between
isolating
between
isolating
between
isolating
poles
distance
poles
distance
poles
distance
and across
and across
and across
open
open
open
switching
switching
switching
device
device
device
(kV)
(kV)
(kV)
(kV)
(kV)
(kV)
(kV)
3.6
20
23
40
46
10
12
7.2
40
46
60
70
20
23
12
60
70
75
85
28
32
17.5
75
85
95
110
38
45
24
95
110
125
145
50
60
36
145
165
170
195
70
80
52
250
290
95
110
72.5
325
375
140
160
Note: The withstand voltage values “across the isolating distance” are valid only for the
switching devices where the clearance between open contacts is designed to meet safety
requirements specified for disconnectors (isolators).

Fig. C2 : Switchgear rated insulation levels

It should be noted that, at the voltage levels in question, no switching overvoltage
ratings are mentioned. This is because overvoltages due to switching transients are
less severe at these voltage levels than those due to lightning.
Transformers
Figure C3 shown below have been extracted from IEC 60076-3.
The significance of list 1 and list 2 is the same as that for the switchgear table, i.e.
the choice depends on the degree of exposure to lightning, etc.

Ba

ck

Highest voltage
for equipment
(r.m.s.)
(kV)
i 1.1
3.6
7.2
12
17.5
24
36
52
72.5

(1) This means basically that List 1 generally applies to
switchgear to be used on underground-cable systems while
List 2 is chosen for switchgear to be used on overhead-line
systems.

Rated short duration
power frequency
withstand voltage
(r.m.s.)
(kV)
3
10
20
28
38
50
70
95
140

Fig. C3 : Transformers rated insulation levels

Schneider Electric - Electrical installation guide 2005

Rated lightning impulse
withstand voltage
(peak)
List 1
List 2
(kV)
(kV)
20
40
40
60
60
75
75
95
95
125
145
170
250
325

C3

C - Connection to the HV public
distribution network

1 Supply of power at high voltage

C4

Other components
It is evident that the insulation performance of other HV components associated with
these major items, e.g. porcelain or glass insulators, HV cables, instrument
transformers, etc. must be compatible with that of the switchgear and transformers
noted above. Test schedules for these items are given in appropriate
IEC publications.
The national standards of any particular country are normally rationalized to include
one or two levels only of voltage, current, and fault-levels, etc.

The national standards of any particular country
are normally rationalized to include one or two
levels only of voltage, current, and fault-levels,
etc.

General note:
The IEC standards are intended for worldwide application and consequently
embrace an extensive range of voltage and current levels.
These reflect the diverse practices adopted in countries of different meteorologic,
geographic and economic constraints.

A circuit breaker (or fuse switch, over a limited
voltage range) is the only form of switchgear
capable of safely breaking the very high levels
of current associated with short-circuit faults
occurring on a power system.

Short-circuit current
Standard values of circuit breaker short-circuit current-breaking capability are
normally given in kilo-amps.
These values refer to a 3-phase short-circuit condition, and are expressed as the
average of the r.m.s. values of the AC component of current in each of the three
phases.

Ba

ck

For circuit breakers in the rated voltage ranges being considered in this chapter,
Figure C4 gives standard short-circuit current-breaking ratings.

kV
kA
(rms)

3.6
8
10
16
25
40

7.2
8
12.5
16
25
40

12
8
12.5
16
25
40
50

17.5
8
12.5
16
25
40

24
8
12.5
16
25
40

36
8
12.5
16
25
40

52
8
12.5
20

Fig. C4 : Standard short-circuit current-breaking ratings

Short circuit current calculation
The rules for calculating short-circuit currents in electrical installations are presented
in IEC standard 60909.
The calculation of short-circuit currents at various points in a power system can
quickly turn into an arduous task when the installation is complicated.
The use of specialized software accelerates calculations.
This general standard, applicable for all radial and meshed power systems, 50 or
60 Hz and up to 550 kV, is extremely accurate and conservative.

Ba

It may be used to handle the different types of solid short-circuit (symmetrical or
dissymmetrical) that can occur in an electrical installation:
c Three-phase short-circuit (all three phases), generally the type producing the
highest currents
c Two-phase short-circuit (between two phases), currents lower than three-phase faults
c Two-phase-to-earth short-circuit (between two phases and earth)
c Phase-to-earth short-circuit (between a phase and earth), the most frequent type
(80% of all cases).

ck

Current (I)
2rI''k

When a fault occurs, the transient short-circuit current is a function of time and
comprises two components (see Fig. C5 ).
c An AC component, decreasing to its steady-state value, caused by the various
rotating machines and a function of the combination of their time constants
c A DC component, decreasing to zero, caused by the initiation of the current and a
function of the circuit impedances

2rIb

IDC

2rIk

Ip

Time (t)

tmin

Fig. C5 : Graphic representation of short-circuit quantities as
per IEC 60909

Practically speaking, one must define the short-circuit values that are useful in
selecting system equipment and the protection system:
c I’’k: rms value of the initial symmetrical current
c Ib: rms value of the symmetrical current interrupted by the switching device when
the first pole opens at tmin (minimum delay)
c Ik: rms value of the steady-state symmetrical current
c Ip: maximum instantaneous value of the current at the first peak
c IDC: DC v