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Electrical installation handbook

Volume 2

Electrical devices

3 rd edition

1SDC010001D0203

ABB SACE

Electrical installation handbook

Volume 2

Electrical devices

3 nd edition

June 2005

Index

First edition 2003

Second edition 2004

Third edition 2005

Introduction ............................................................................................................... 2

1 Standards

1.1 General aspects ............................................................................................. 3

1.2 IEC Standards for electrical installation ......................................................... 15

2 Protection of feeders

2.1 Introduction .................................................................................................. 22

2.2 Installation and dimensioning of cables ......................................................... 25

2.2.1 Current carrying capacity and methods of installation ........................ 25

Installation not buried in the ground ................................................... 31

Installation in ground .......................................................................... 44

2.2.2 Voltage drop ........................................................................................ 56

2.2.3 Joule-effect losses .............................................................................. 66

2.3 Protection against overload .......................................................................... 67

2.4 Protection against short-circuit ..................................................................... 70

2.5 Neutral and protective conductors ............................................................... 78

2.6 Busbar trunking systems .............................................................................. 86

3 Protection of electrical equipment

3.1 Protection and switching of lighting circuits ................................................ 101

3.2 Protection and switching of generators ...................................................... 110

3.3 Protection and switching of motors ............................................................ 115

3.4 Protection and switching of transformers ................................................... 135

4 Power factor correction

4.1 General aspects ......................................................................................... 150

4.2 Power factor correction method ................................................................. 156

4.3 Circuit-breakers for the protection and switching of capacitor banks .......... 163

5 Protection of human beings

5.1 General aspects: effects of current on human beings ................................. 166

5.2 Distribution systems ................................................................................... 169

5.3 Protection against both direct and indirect contact ..................................... 172

5.4 TT system .................................................................................................. 175

5.5 TN system .................................................................................................. 178

5.6 IT system ................................................................................................... 181

5.7 Residual current devices ............................................................................ 183

5.8 Maximum protected length for the protection of human beings .................. 186

6 Calculation of short-circuit current

6.1 General aspects ......................................................................................... 204

6.2 Fault typologies .......................................................................................... 204

6.3 Determination of the short-circuit current: “short-circuit

power method” .......................................................................................... 206

6.3.1 Calculation of the short-circuit current ............................................. 206

6.3.2 Calculation of the short-circuit power at the fault point .................... 209

6.3.3 Calculation of the short-circuit current ............................................. 210

6.3.4 Examples ........................................................................................ 212

6.4 Determination of the short-circuit current Ik downstream of a

cable as a function of the upstream one ..................................................... 216

6.5 Algebra of sequences ................................................................................ 218

6.5.1 General aspects .............................................................................. 218

6.5.2 Positive, negative and zero sequence systems ................................ 219

6.5.3 Calculation of short-circuit currents with the algebra

of sequences .................................................................................. 220

6.5.4 Positive, negative and zero sequence short-circuit

impedances of electrical equipment ................................................ 223

6.5.5 Formulas for the calculation of the fault currents as a

function of the electrical parameters of the plant .............................. 226

6.6 Calculation of the peak value of the short-circuit current ............................. 229

6.7 Considerations about UPS contribution to the short-circuit ........................ 230

Annex A: Calculation tools

A.1 Slide rules ......................................................................................... 233

A.2 DOCWin ........................................................................................... 238

Annex B: Calculation of load current I b ............................................................... 242

Annex C: Harmonics ............................................................................................. 246

Annex D: Calculation of the coefficient k for the cables ................................... 254

Annex E: Main physical quantities and electrotechnical formulas .................. 258

Published by ABB SACE

via Baioni, 35 - 24123 Bergamo (Italy)

ABB SACE - Electrical devices

Introduction

1 Standards

Scope and objectives

The scope of this electrical installation handbook is to provide the designer and

user of electrical plants with a quick reference, immediate-use working tool.

This is not intended to be a theoretical document, nor a technical catalogue,

but, in addition to the latter, aims to be of help in the correct definition of

equipment, in numerous practical installation situations.

1.1 General aspects

In each technical field, and in particular in the electrical sector, a condition

sufficient (even if not necessary) for the realization of plants according to the

“status of the art” and a requirement essential to properly meet the demands

of customers and of the community, is the respect of all the relevant laws and

technical standards.

Therefore, a precise knowledge of the standards is the fundamental premise

for a correct approach to the problems of the electrical plants which shall be

designed in order to guarantee that “acceptable safety level” which is never

absolute.

The dimensioning of an electrical plant requires knowledge of different factors

relating to, for example, installation utilities, the electrical conductors and other

components; this knowledge leads the design engineer to consult numerous

documents and technical catalogues. This electrical installation handbook,

however, aims to supply, in a single document, tables for the quick definition of

the main parameters of the components of an electrical plant and for the selection

of the protection devices for a wide range of installations. Some application

examples are included to aid comprehension of the selection tables.

Juridical Standards

These are all the standards from which derive rules of behavior for the juridical

persons who are under the sovereignty of that State.

Electrical installation handbook users

The electrical installation handbook is a tool which is suitable for all those who

are interested in electrical plants: useful for installers and maintenance technicians

through brief yet important electrotechnical references, and for sales engineers

through quick reference selection tables.

Technical Standards

These standards are the whole of the prescriptions on the basis of which

machines, apparatus, materials and the installations should be designed,

manufactured and tested so that efficiency and function safety are ensured.

The technical standards, published by national and international bodies, are

circumstantially drawn up and can have legal force when this is attributed by a

legislative measure.

Validity of the electrical installation handbook

Some tables show approximate values due to the generalization of the selection

process, for example those regarding the constructional characteristics of

electrical machinery. In every case, where possible, correction factors are given

for actual conditions which may differ from the assumed ones. The tables are

always drawn up conservatively, in favour of safety; for more accurate

calculations, the use of DOCWin software is recommended for the dimensioning

of electrical installations.

Application fields

Electrotechnics and

Mechanics, Ergonomics

Telecommunications

Electronics

and Safety

International Body

IEC

ITU

ISO

European Body

CENELEC ETSI CEN

This technical collection takes into consideration only the bodies dealing with electrical and electronic

technologies.

IEC International Electrotechnical Commission

The International Electrotechnical Commission (IEC) was officially founded in

1906, with the aim of securing the international co-operation as regards

standardization and certification in electrical and electronic technologies. This

association is formed by the International Committees of over 40 countries all

over the world.

The IEC publishes international standards, technical guides and reports which

are the bases or, in any case, a reference of utmost importance for any national

and European standardization activity.

IEC Standards are generally issued in two languages: English and French.

In 1991 the IEC has ratified co-operation agreements with CENELEC (European

standardization body), for a common planning of new standardization activities

and for parallel voting on standard drafts.

ABB SACE - Electrical devices

1.1 General aspects

1 Standards

CENELEC European Committee for Electrotechnical Standardization

The European Committee for Electrotechnical Standardization (CENELEC) was

set up in 1973. Presently it comprises 28 countries (Austria, Belgium, Cyprus,

Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary,

Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Portugal, Poland, Slovakia, Slovenia, Spain, Sweden, Switzerland, United

Kingdom) and cooperates with 7 affiliates (Albania, Bosnia and Herzegovina,

Bulgaria, Croatia, Romania, Turkey, Ukraine) which have first maintained the

national documents side by side with the CENELEC ones and then replaced

them with the Harmonized Documents (HD).

There is a difference between EN Standards and Harmonization Documents

(HD): while the first ones have to be accepted at any level and without additions

or modifications in the different countries, the second ones can be amended to

meet particular national requirements.

EN Standards are generally issued in three languages: English, French and

German.

From 1991 CENELEC cooperates with the IEC to accelerate the standards

preparation process of International Standards.

CENELEC deals with specific subjects, for which standardization is urgently

required.

When the study of a specific subject has already been started by the IEC, the

European standardization body (CENELEC) can decide to accept or, whenever

necessary, to amend the works already approved by the International

standardization body.

“Low Voltage” Directive 73/23/CEE – 93/68/CEE

The Low Voltage Directive refers to any electrical equipment designed for use

at a rated voltage from 50 to 1000 V for alternating current and from 75 to 1500 V for

direct current.

In particular, it is applicable to any apparatus used for production, conversion,

transmission, distribution and use of electrical power, such as machines,

transformers, devices, measuring instruments, protection devices and wiring

materials.

The following categories are outside the scope of this Directive:

• electrical equipment for use in an explosive atmosphere;

• electrical equipment for radiology and medical purposes;

• electrical parts for goods and passenger lifts;

• electrical energy meters;

• plugs and socket outlets for domestic use;

• electric fence controllers;

• radio-electrical interference;

• specialized electrical equipment, for use on ships, aircraft or railways, which

complies with the safety provisions drawn up by international bodies in which

the Member States participate.

Directive EMC 89/336/EEC (“Electromagnetic Compatibility”)

The Directive on electromagnetic compatibility regards all the electrical and

electronic apparatus as well as systems and installations containing electrical

and/or electronic components. In particular, the apparatus covered by this

Directive are divided into the following categories according to their

characteristics:

• domestic radio and TV receivers;

• industrial manufacturing equipment;

• mobile radio equipment;

• mobile radio and commercial radio telephone equipment;

• medical and scientific apparatus;

• information technology equipment (ITE);

• domestic appliances and household electronic equipment;

• aeronautical and marine radio apparatus;

• educational electronic equipment;

• telecommunications networks and apparatus;

• radio and television broadcast transmitters;

• lights and fluorescent lamps.

The apparatus shall be so constructed that:

a) the electromagnetic disturbance it generates does not exceed a level allowing

radio and telecommunications equipment and other apparatus to operate

as intended;

b) the apparatus has an adequate level of intrinsic immunity to electromagnetic

disturbance to enable it to operate as intended.

An apparatus is declared in conformity to the provisions at points a) and b)

when the apparatus complies with the harmonized standards relevant to its

product family or, in case there aren’t any, with the general standards.

EC DIRECTIVES FOR ELECTRICAL EQUIPMENT

Among its institutional roles, the European Community has the task of

promulgating directives which must be adopted by the different member states

and then transposed into national law.

Once adopted, these directives come into juridical force and become a reference

for manufacturers, installers, and dealers who must fulfill the duties prescribed

by law.

Directives are based on the following principles:

• harmonization is limited to essential requirements;

• only the products which comply with the essential requirements specified by

the directives can be marketed and put into service;

• the harmonized standards, whose reference numbers are published in the

Official Journal of the European Communities and which are transposed into

the national standards, are considered in compliance with the essential

requirements;

• the applicability of the harmonized standards or of other technical specifications

is facultative and manufacturers are free to choose other technical solutions

which ensure compliance with the essential requirements;

• a manufacturer can choose among the different conformity evaluation proce-

dure provided by the applicable directive.

The scope of each directive is to make manufacturers take all the necessary

steps and measures so that the product does not affect the safety and health

of persons, animals and property.

ABB SACE - Electrical devices

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