electrical installation guideline

7/22/2019 ELECTRICAL INSTALLATION GUIDELINE

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This technical guide is the result oa collective eort.

Technical advisor:Serge Volut - Jacques Schonek

Illustrations and production:AXESS - Valence -France

Printing:

Edition: 2010

Price: 40

ISBN: 978.2.9531643.3.6N dpt lgal: 1er semestre 2008

Schneider ElectricAll rights reserved in all countries

The Electrical Installation Guide is a single document covering thetechniques, regulations and standards related to electrical installations.It is intended or electrical proessionals in companies, design ofces,inspection organisations, etc.

This Technical Guide is aimed at proessional users and is only intendedto provide them guidelines or the defnition o an industrial, tertiary or

domestic electrical installation. Inormation and guidelines contained in thisGuide are provided AS IS. Schneider Electric makes no warranty o anykind, whether express or implied, such as but not limited to the warrantieso merchantability and ftness or a particular purpose, nor assumes anylegal liability or responsibility or the accuracy, completeness, or useulnesso any inormation, apparatus, product, or process disclosed in this Guide,nor represents that its use would not inringe privately owned rights.The purpose o this guide is to acilitate the implementation o Internationalinstallation standards or designers & contractors, but in all cases theoriginal text o International or local standards in orce shall prevail.

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

We thank all the readers o the previous edition o this guide or theircomments that have helped improve the current edition.We also thank the many people and organisations, too numerous to namehere, who have contributed in one way or another to the preparation o thisguide.

This guide has been written or electrical Engineers who have todesign, realize, inspect or maintain electrical installations in compliancewith international Standards o the International ElectrotechnicalCommission (IEC).Which technical solution will guarantee that all relevant saety rules aremet? This question has been a permanent guideline or the elaboration othis document.

An international Standard such as the IEC 60364 Electrical Installationin Buildings specifes extensively the rules to comply with to ensuresaety and predicted operational characteristics or all types o electricalinstallations. As the Standard must be extensive, and has to be applicableto all types o products and the technical solutions in use worldwide, thetext o the IEC rules is complex, and not presented in a ready-to-use order.

The Standard cannot thereore be considered as a working handbook, butonly as a reerence document.

The aim o the present guide is to provide a clear, practical and step-by-step explanation or the complete study o an electrical installation,according to IEC 60364 and other relevant IEC Standards. Thereore, thefrst chapter (B) presents the methodology to be used, and each chapterdeals with one out o the eight steps o the study. The two last chapters aredevoted to particular supply sources, loads and locations, and appendixprovides additional inormation. Special attention must be paid to theEMC appendix, which is based on the broad and practical experience onelectromagnetic compatibility problems.

We all hope that you, the user, will fnd this handbook genuinely helpul.

Schneider Electric S.A.


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4/491Schneider Electric - Electrical installation guide 2010

Guiding tools or more efciency in electrical

distribution design

Technical knowledge Pre-design help or budget

approach

10-30mn eLearning modules or

individual training

Articles giving base skills about

general subjects: Cahiers

Techniques

Selection criterias & method

to ollow in order to pre-defne

project specifcation:

bArchitecture guide

bID-Spec sotware

Solutions and examples with

recommended architectures in

Solution guides:

bairport

bautomativebood

bretail

bofce

bindustrial buildings

bhealthcare

bwater

b...



Design support Specifcation help Help in installation, use &

maintenance

Practical data & methods

through major design guides:

bElectrical Installation Guide

bProtection guide

bIndustrial electrical network

design guide

b...

Product presentation o technical

characteristics in all SchneiderElectric product Catalogues

Design Sotware:

bMy Ecodial

Ecodial sotware provides a

complete design package or

LV installations, in accordance

with IEC standards and

recommendations.

Main eatures:

vCreate diagrams

vOptimise circuit breakers curves

vDetermine source power

vFollow step by step calculation

vPrint the project design fle

bSISPRO building

b ...

Drawing source fles or

connection, dimension, diagram,

mounting & saety: CAD library

Technical specifcation on

products & solutions or tender

request

Product installation data

Product how to use data

Product maintenance data


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Foreword

Etienne TISON, International Electrotechnical Commission (IEC) TC64Chairman.The task o the IEC Technical Committee 64 is to develop and keep up-to-date requirements

- or the protection o persons against electrical shock, and- or the design, verifcation and implementation o low voltage electricalinstallations.

Standard such as IEC 60364 developed by IEC TC64 is considered by theinternational community as the basis o the majority o national low voltagewiring rules.

IEC 60364 is mainly ocussed on saety due the use o electricity by peoplewho may not be aware o risk resulting rom the use o electricity.

But modern electrical installations are increasingly complex, due to externalinput such as- electromagnetic disturbances- energy efciency- ...

Consequently, designers, installers and consumers need guidance on theselection and installation o electrical equipment.

Schneider Electric has developed this Electrical Installation Guidededicated to low voltage electrical installations. It is based on IEC TC64standards such as IEC 60364 and provides additional inormation in orderto help designers, contractors and controllers or implementing correct low-voltage electrical installations.

As TC64 Chairman, it is my great pleasure and honour to introduce thisguide. I am sure it will be used ruitully by all persons involved in theimplementation o all low-voltage electrical installations.

Etienne TISON

Etienne TISON has been working with SchneiderElectric since 1978. He has been always involvedis various activities in low voltage feld.In 2008, Etienne TISON has been appointed

Chairman o IEC TC64 as well as Chairman oCENELEC TC64.

Electrical installation guide 2010


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LVswitchgear:unctions&selection

1 The basic unctions o LV switchgear H2

2 The switchgear H5

3 Choice o switchgear H104 Circuit breaker H11

ProtectionagainstvoltagesurgesinLV

1 Overvoltage characteristics o atmospheric origin J2

2 Principle o lightning protection J7

3 Design o the electrical installation protection system J13

4 Installation o SPDs J24

5 Application J28

6 Technical supplements J29

EnergyEfciencyinelectricaldistribution

1 Introduction K2

2 Energy eciency and electricity K3

3 Diagnosis through electrical measurement K6

4 Energy saving opportunities K8

5 How to evaluate energy savings K24

Poweractorcorrectionandharmonicfltering

1 Reactive energy and power actor L2

2 Why to improve the power actor? L5

3 How to improve the power actor? L7

4 Where to install power correction capacitors? L10

5 How to decide the optimum level o compensation? L12

6 Compensation at the terminals o a transormer L15

7 Power actor correction o induction motors L18

8 Example o an installation beore and ater power actor correction L20

9 The eects o harmonics L21

10 Implementation o capacitor banks L24

Harmonicmanagement

1 The problem: M2Why is it necessary to detect and eliminate harmonics?

2 Standards M3

3 General M4

4 Main eects o harmonics in installations M6

5 Essential indicators o harmonic distortion and M11measurement principles

6 Measuring the indicators M14

7 Detection devices M16

8 Solutions to attenuate harmonics M17

Characteristicsoparticularsourcesandloads

1 Protection o a LV generator set and the downstream circuits N2

2 Uninterruptible Power Supply Units (UPS) N11

3 Protection o LV/LV transormers N24

4 Lighting circuits N27

5 Asynchronous motors N45

Photovoltaicinstallations

1 Benets o photovoltaic energy P2

2 Background and technology P3

3 Special equipment P5

4 Installation requirements P85 Installation P11

6 Monitoring P16

7 Additional inormation P18

Generalcontents

J

K

L

M

N

H

P



Residentialandotherspeciallocations

1 Residential and similar premises Q2

2 Bathrooms and showers Q8

3 Recommendations applicable to special installations and locations Q12

EMCguidelines

1 Electrical distribution R2

2 Earthing principles and structures R3

3 Implementation R5

4 Coupling mechanism and counter-measures R16

5 Wiring recommendations R22

Q

R

Generalcontents



A

SchneiderElectric-allrightsreserved

Chapter A

General rules o electricalinstallation design

Contents

Methodology A2

Rules and statutory regulations A4

2.1 Denition o voltage ranges A4

2.2 Regulations A5

2.3 Standards A5

2.4 Quality and saety o an electrical installation A6

2.5 Initial testing o an installation A6

2.6 Periodic check-testing o an installation A7

2.7 Conormity (with standards and specications) o equipmentused in the installation A7

2.8 Environment A8

Installed power loads - Characteristics A03.1 Induction motors A10

3.2 Resistive-type heating appliances and incandescent lamps(conventional or halogen) A12

Power loading o an installation A5

4.1 Installed power (kW) A15

4.2 Installed apparent power (kVA) A15

4.3 Estimation o actual maximum kVA demand A16

4.4 Example o application o actors ku and ks A17

4.5 Diversity actor A18

4.6 Choice o transormer rating A19

4.7 Choice o power-supply sources A20

2

3

4


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A3


Protection against overvoltages

Direct or indirect lightning strokes can damage electrical equipment at a distanceo several kilometers. Operating voltage surges, transient and industrial requency

over-voltage can also produce the same consequences.The eects are examinedand solutions are proposed.

Energy eciency in electrial distribution

Implementation o measuring devices with an adequate communication systemwithin the electrical installation can produce high benets or the user or owner:reduced power consumption, reduced cost o energy, better use o electricalequipment.

Reactive energy

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

Harmonics

Harmonics in the network aect the quality o energy and are at the origin o manydisturbances as overloads, vibrations, ageing o equipment, trouble o sensitiveequipment, o local area networks, telephone networks. This chapter deals with theorigins and the eects o harmonics and explain how to measure them and presentthe solutions.

Particular supply sources and loads

Particular items or equipment are studied:

b Specic sources such as alternators or inverters

b Specic loads with special characteristics, such as induction motors, lightingcircuits or LV/LV transormers

b Specic systems, such as direct-current networks

A green and economical energy

The solar energy development has to respect specic installation rules.

Generic applications

Certain premises and locations are subject to particularly strict regulations: the mostcommon example being residential dwellings.

EMC Guidelines

Some basic rules must be ollowed in order to ensure Electromagnetic Compatibility.Non observance o these rules may have serious consequences in the operation othe electrical installation: disturbance o communication systems, nuisance trippingo protection devices, and even destruction o sensitive devices.

Ecodial sotware

Ecodial sotware(1) provides a complete design package or LV installations, inaccordance with IEC standards and recommendations.

The ollowing eatures are included:b Construction o one-line diagrams

b Calculation o short-circuit currents

b Calculation o voltage drops

b Optimization o cable sizes

b Required ratings o switchgear and usegear

b Discrimination o protective devices

b Recommendations or cascading schemes

b Verication o the protection o people

b Comprehensive print-out o the oregoing calculated design data

J Protection against voltage surges in LV

L - Power actor correction and harmonic ltering

N - Characteristics o particular sources andloads

P - Photovoltaic Installations

M - Harmonic management

(1) Ecodial is a Merlin Gerin product and is available in French

and English versions.

Methodology

K Energy eciency in electrical distribution

Q - Residential and other special locations

R - EMC guidelines

A companion tool o the Electrical InstallationGuide



A - General rules o electrical installation design

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Low-voltage installations are governed by a number o regulatory and advisory texts,which may be classied as ollows:b Statutory regulations (decrees, actory acts,etc.)

bCodes o practice, regulations issued by proessional institutions, job specications

b National and international standards or installations

b National and international standards or products

2. Denition o voltage ranges

IEC voltage standards and recommendations

2 Rules and statutory regulations

Three-phase our-wire or three-wire systems Single-phase three-wire systemsNominal voltage (V) Nominal voltage (V)

50 Hz 60 Hz 60 Hz

120/208 120/240 240

230/400(1) 277/480

400/690(1) 480

347/600

1000 600

(1) The nominal voltage o existing 220/380 V and 240/415 V systems shall evolve

toward the recommended value o 230/400 V. The transition period should be as short

as possible and should not exceed the year 2003. During this period, as a rst step, theelectricity supply authorities o countries having 220/380 V systems should bring the

voltage within the range 230/400 V +6 %, -10 % and those o countries having

240/415 V systems should bring the voltage within the range 230/400 V +10 %,-6 %. At the end o this transition period, the tolerance o 230/400 V 10 % should

have been achieved; ater this the reduction o this range will be considered. All the

above considerations apply also to the present 380/660 V value with respect to therecommended value 400/690 V.

Fig. A1 : Standard voltages between 100 V and 1000 V (IEC 60038 Edition 6.2 2002-07)

Series I Series II

Highest voltage Nominal system Highest voltage Nominal system

or equipment (kV) voltage (kV) or equipment (kV) voltage (kV)

3.6(1) 3.3(1) 3(1) 4.40(1) 4.16(1)

7.2(1) 6.6(1) 6(1)

12 11 10

13.2(2) 12.47(2)

13.97(2) 13.2(2)

14.52(1) 13.8(1)

(17.5) (15)

24 22 20

26.4(2) 24.94(2)

36(3) 33(3)

36.5 34.5

40.5(3) 35(3)

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-preerred values. It isrecommended that these values should not be used or new systems to be constructed

in uture.

Note : 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 o Series I, the highest voltage and the lowest voltage do

not dier by more than approximately 10 % rom the nominal voltage o the system.

In a normal system o Series II, the highest voltage does not dier by more then +5 %and the lowest voltage by more than -10 % rom the nominal voltage o the system.

(1) These values should not be used or public distribution systems.

(2) These systems are generally our-wire systems.(3) The unication o these values is under consideration.

Fig. A2: Standard voltages above 1 kV and not exceeding 35 kV(IEC 60038 Edition 6.2 2002-07)



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2.2 Regulations

In most countries, electrical installations shall comply with more than one set o

regulations, issued by National Authorities or by recognized private bodies. It isessential to take into account these local constraints beore starting the design.

2.3 Standards

This Guide is based on relevant IEC standards, in particular IEC 60364. IEC 60364has been established by medical and engineering experts o all countries in theworld comparing their experience at an international level. Currently, the saetyprinciples o IEC 60364 and 60479-1 are the undamentals o most electricalstandards in the world (see table below and next page).

IEC 60038 Standard voltagesIEC 60076-2 Power transormers - Temperature rise

IEC 60076-3 Power transormers - Insulation levels, dielectric tests and external clearances in air

IEC 60076-5 Power transormers - Ability to withstand short-circuitIEC 60076-0 Power transormers - Determination o sound levels

IEC 6046 Semiconductor convertors - General requirements and line commutated convertors

IEC 60255 Electrical relaysIEC 60265- High-voltage switches - High-voltage switches or rated voltages above 1 kV and less than 52 kV

IEC 60269- Low-voltage uses - General requirementsIEC 60269-2 Low-voltage uses - Supplementary requirements or uses or use by unskilled persons (uses mainly or household and similar applications)IEC 60282- High-voltage uses - Current-limiting uses

IEC 60287-- Electric cables - Calculation o the current rating - Current rating equations (100% load actor) and calculation o losses - GeneralIEC 60364 Electrical installations o buildings

IEC 60364- Electrical installations o buildings - Fundamental principles

IEC 60364-4-4 Electrical installations o buildings - Protection or saety - Protection against electric shockIEC 60364-4-42 Electrical installations o buildings - Protection or saety - Protection against thermal eects

IEC 60364-4-43 Electrical installations o buildings - Protection or saety - Protection against overcurrent

IEC 60364-4-44 Electrical installations o buildings - Protection or saety - Protection against electromagnetic and voltage disrurbanceIEC 60364-5-5 Electrical installations o buildings - Selection and erection o electrical equipment - Common rules

IEC 60364-5-52 Electrical installations o buildings - Selection and erection o electrical equipment - Wiring systems

IEC 60364-5-53 Electrical installations o buildings - Selection and erection o electrical equipment - Isolation, switching and controlIEC 60364-5-54 Electrical installations o buildings - Selection and erection o electrical equipment - Earthing arrangements

IEC 60364-5-55 Electrical installations o buildings - Selection and erection o electrical equipment - Other equipmentsIEC 60364-6-6 Electrical installations o buildings - Verication and testing - Initial verication

IEC 60364-7-70 Electrical installations o buildings - Requirements or special installations or locations - Locations containing a bath tub or shower basin

IEC 60364-7-702 Electrical installations o buildings - Requirements or special installations or locations - Swimming pools and other basinsIEC 60364-7-703 Electrical installations o buildings - Requirements or special installations or locations - Locations containing sauna heaters

IEC 60364-7-704 Electrical installations o buildings - Requirements or special installations or locations - Construction and demolition site installations

IEC 60364-7-705 Electrical installations o buildings - Requirements or special installations or locations - Electrical installations o agricultural and horticulturalpremises

IEC 60364-7-706 Electrical installations o buildings - Requirements or special installations or locations - Restrictive conducting locations

IEC 60364-7-707 Electrical installations o buildings - Requirements or special installations or locations - Earthing requirements or the installation o dataprocessing equipment

IEC 60364-7-708 Electrical installations o buildings - Requirements or special installations or locations - Electrical installations in caravan parks and caravansIEC 60364-7-709 Electrical installations o buildings - Requirements or special installations or locations - Marinas and pleasure crat

IEC 60364-7-70 Electrical installations o buildings - Requirements or special installations or locations - Medical locationsIEC 60364-7-7 Electrical installations o buildings - Requirements or special installations or locations - Exhibitions, shows and standsIEC 60364-7-72 Electrical installations o buildings - Requirements or special installations or locations - Solar photovoltaic (PV) power supply systems

IEC 60364-7-73 Electrical installations o buildings - Requirements or special installations or locations - Furniture

IEC 60364-7-74 Electrical installations o buildings - Requirements or special installations or locations - External lighting installationsIEC 60364-7-75 Electrical installations o buildings - Requirements or special installations or locations - Extra-low-voltage lighting installations

IEC 60364-7-77 Electrical installations o buildings - Requirements or special installations or locations - Mobile or transportable units

IEC 60364-7-740 Electrical installations o buildings - Requirements or special installations or locations - Temporary electrical installations or structures,amusement devices and booths at airgrounds, amusement parks and circuses

IEC 60427 High-voltage alternating current circuit-breakers

IEC 60439- Low-voltage switchgear and controlgear assemblies - Type-tested and partially type-tested assembliesIEC 60439-2 Low-voltage switchgear and controlgear assemblies - Particular requirements or busbar trunking systems (busways)

IEC 60439-3 Low-voltage switchgear and controlgear assemblies - Particular requirements or low-voltage switchgear and controlgear assemblies intended to

be installed in places where unskilled persons have access or their use - Distribution boardsIEC 60439-4 Low-voltage switchgear and controlgear assemblies - Particular requirements or assemblies or construction sites (ACS)

IEC 60446 Basic and saety principles or man-machine interace, marking and identication - Identication o conductors by colours or numeralsIEC 60439-5 Low-voltage switchgear and controlgear assemblies - Particular requirements or assemblies intended to be installed outdoors in public places

- Cable distribution cabinets (CDCs)

IEC 60479- Eects o current on human beings and livestock - General aspectsIEC 60479-2 Eects o current on human beings and livestock - Special aspects

IEC 60479-3 Eects o current on human beings and livestock - Eects o currents passing through the body o livestock

(Continued on next page)





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IEC 60529 Degrees o protection provided by enclosures (IP code)IEC 60644 Spcication or high-voltage use-links or motor circuit applications

IEC 60664 Insulation coordination or equipment within low-voltage systems

IEC 6075 Dimensions o low-voltage switchgear and controlgear. Standardized mounting on rails or mechanical support o electrical devices in switchgear

and controlgear installations.IEC 60724 Short-circuit temperature limits o electric cables with rated voltages o 1 kV (Um = 1.2 kV) and 3 kV (Um = 3.6 kV)IEC 60755 General requirements or residual current operated protective devicesIEC 60787 Application guide or the selection o use-links o high-voltage uses or transormer circuit application

IEC 6083 Shunt power capacitors o the sel-healing type or AC systems having a rated voltage up to and including 1000 V - General - Perormance, testingand rating - Saety requirements - Guide or installation and operation

IEC 60947- Low-voltage switchgear and controlgear - General rules

IEC 60947-2 Low-voltage switchgear and controlgear - Circuit-breakersIEC 60947-3 Low-voltage switchgear and controlgear - Switches, disconnectors, switch-disconnectors and use-combination units

IEC 60947-4- Low-voltage switchgear and controlgear - Contactors and motor-starters - Electromechanical contactors and motor-starters

IEC 60947-6- Low-voltage switchgear and controlgear - Multiple unction equipment - Automatic transer switching equipmentIEC 6000 Electromagnetic compatibility (EMC)

IEC 640 Protection against electric shocks - common aspects or installation and equipment

IEC 6557- Electrical saety in low-voltage distribution systems up to 1000 V AC and 1500 V DC - Equipment or testing, measuring or monitoring o protectivemeasures - General requirements

IEC 6557-8 Electrical saety in low-voltage distribution systems up to 1000 V AC and 1500 V DC - Equipment or testing, measuring or monitoring o protectivemeasures

IEC 6557-9 Electrical saety in low-voltage distribution systems up to 1000 V AC and 1500 V DC - Equipment or insulation ault location in IT systems

IEC 6557-2 Electrical saety in low-voltage distribution systems up to 1000 V AC and 1500 V DC - Equipment or testing, measuring or monitoring o protectivemeasures. Perormance measuring and monitoring devices (PMD)

IEC 6558-2-6 Saety o power transormers, power supply units and similar - Particular requirements or saety isolating transormers or general use

IEC 6227- Common specications or high-voltage switchgear and controlgear standardsIEC 6227-00 High-voltage switchgear and controlgear - High-voltage alternating-current c ircuit-breakers

IEC 6227-02 High-voltage switchgear and controlgear - Alternating current disconnectors and earthing switches

IEC 6227-05 High-voltage switchgear and controlgear - Alternating current switch-use combinationsIEC 6227-200 High-voltage switchgear and controlgear - Alternating current metal-enclosed switchgear and controlgear or rated voltages above 1 kV and up to

and including 52 kV

IEC 6227-202 High-voltage/low voltage preabricated substations

(Concluded)

2.4 Quality and saety o an electrical installation

In so ar as control procedures are respected, quality and saety will be assuredonly i:

b The initial checking o conormity o the electrical installation with the standard andregulation has been achieved

b The electrical equipment comply with standards

b The periodic checking o the installation recommended by the equipmentmanuacturer is respected.

2.5 Initial testing o an installation

Beore a utility will connect an installation to its supply network, strict pre-

commissioning electrical tests and visual inspections by the authority, or by its

appointed agent, must be satised.

These tests are made according to local (governmental and/or institutional)

regulations, which may dier slightly rom one country to another. The principles o

all such regulations however, are common, and are based on the observance o

rigorous saety rules in the design and realization o the installation.

IEC 60364-6-61 and related standards included in this guide are based on aninternational consensus or such tests, intended to cover all the saety measures andapproved installation practices normally required or residential, commercial and (themajority o) industrial buildings. Many industries however have additional regulationsrelated to a par ticular product (petroleum, coal, natural gas, etc.). Such additionalrequirements are beyond the scope o this guide.

The pre-commissioning electrical tests and visual-inspection checks or installationsin buildings include, typically, all o the ollowing:

b Insulation tests o all cable and wiring conductors o the xed installation, between

phases and between phases and earthb Continuity and conductivity tests o protective, equipotential and earth-bondingconductors

b Resistance tests o earthing electrodes with respect to remote earth

b Verication o the proper operation o the interlocks, i any

b Check o allowable number o socket-outlets per circuit



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b Cross-sectional-area check o all conductors or adequacy at the short-circuitlevels prevailing, taking account o the associated protective devices, materials andinstallation conditions (in air, conduit, etc.)

b Verication that all exposed- and extraneous metallic parts are properly earthed(where appropriate)

b Check o clearance distances in bathrooms, etc.

These tests and checks are basic (but not exhaustive) to the majority o installations,while numerous other tests and rules are included in the regulations to coverparticular cases, or example: TN-, TT- or IT-earthed installations, installations basedon class 2 insulation, SELV circuits, and special locations, etc.

The aim o this guide is to draw attention to the particular eatures o dierent typeso installation, and to indicate the essential rules to be observed in order to achievea satisactory level o quality, which will ensure sae and trouble-ree perormance.The methods recommended in this guide, modied i necessary to comply with anypossible variation imposed by a utility, are intended to satisy all precommissioningtest and inspection requirements.

2.6 Periodic check-testing o an installation

In many countries, all industrial and commercial-building installations, together withinstallations in buildings used or public gatherings, must be re-tested periodically byauthorized agents.Figure A3 shows the requency o testing commonly prescribed according to thekind o installation concerned.

Fig A3: Frequency o check-tests commonly recommended or an electrical installation

2.7 Conormity (with standards and specications)o equipment used in the installation

Attestation o conormity

The conormity o equipment with the relevant standards can be attested:

b By an ocial mark o conormity granted by the certication body concerned, or

b By a certicate o conormity issued by a certication body, or

b By a declaration o conormity rom the manuacturer

The rst two solutions are generally not available or high voltage equipment.

Declaration o conormity

Where the equipment is to be used by skilled or instructed persons, the

manuacturers declaration o conormity (included in the technical documentation),

is generally recognized as a valid attestation. Where the competence o themanuacturer is in doubt, a certifcate o conormity can reinorce the manuacturers

declaration.

Type o installation Testing

requency

Installations which b Locations at which a risk o degradation, Annually

requirethe protection re or explosion exists

o employees b Temporary installations at worksites b Locations at which MV installations exist

b Restrictive conducting locations

where mobile equipment is used

Other cases Every 3 years

Installations in buildings According to the type o establishment From one to

used or public gatherings, and its capacity or receiving the public three years

where protection againstthe risks o re and panic

are required

Residential According to local regulations

Conormity o equipment with the relevantstandards can be attested in several ways




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Note: CE marking

In Europe, the European directives require the manuacturer or his authorizedrepresentative to ax the CE marking on his own responsibility. It means that:

b The product meets the legal requirementsb It is presumed to be marketable in Europe

The CE marking is neither a mark o origin nor a mark o conormity.

Mark o conormity

Marks o conormity are axed on appliances and equipment generally used byordinary non instructed people (e.g in the eld o domestic appliances). A mark oconormity is delivered by certication body i the equipment meet the requirementsrom an applicable standard and ater verication o the manuacturers qualitymanagement system.

Certication o Quality

The standards dene several methods o quality assurance which correspond todierent situations rather than to dierent levels o quality.

AssuranceA laboratory or testing samples cannot certiy the conormity o an entire productionrun: these tests are called type tests. In some tests or conormity to standards,the samples are destroyed (tests on uses, or example).

Only the manuacturer can certiy that the abricated products have, in act,the characteristics stated.

Quality assurance certication is intended to complete the initial declaration orcertication o conormity.

As proo that all the necessary measures have been taken or assuring the quality oproduction, the manuacturer obtains certication o the quality control system whichmonitors the abrication o the product concerned. These certicates are issuedby organizations specializing in quality control, and are based on the internationalstandard ISO 9001: 2000.

These standards dene three model systems o quality assurance control

corresponding to dierent situations rather than to dierent levels o quality:b Model 3 denes assurance o quality by inspection and checking o nal products.

b Model 2 includes, in addition to checking o the nal product, verication o themanuacturing process. For example, this method is applied, to the manuacturer o

uses where perormance characteristics cannot be checked without destroying theuse.

b Model 1 corresponds to model 2, but with the additional requirement that thequality o the design process must be rigorously scrutinized; or example, where it isnot intended to abricate and test a prototype (case o a custom-built product made tospecication).

2.8 Environment

Environmental management systems can be certied by an independent body i theymeet requirements given in ISO 14001. This type o certication mainly concernsindustrial settings but can also be granted to places where products are designed.

A product environmental design sometimes called eco-design is an approach osustainable development with the objective o designing products/services bestmeeting the customers requirements while reducing their environmental impactover their whole lie cycle. The methodologies used or this purpose lead to chooseequipments architecture together with components and materials taking into accountthe infuence o a product on the environment along its lie cycle (rom extraction oraw materials to scrap) i.e. production, transport, distribution, end o lie etc.

In Europe two Directives have been published, they are called:

b RoHS Directive (Restriction o Hazardous Substances) coming into orce onJuly 2006 (the coming into orce was on February 13th, 2003, and the applicationdate is July 1st, 2006) aims to eliminate rom products six hazardous substances:lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB) orpolybrominated diphenyl ethers (PBDE).



A9



b WEEE Directive (Waste o Electrical and Electronic Equipment) coming intoorce in August 2005 (the coming into orce was on February 13 th, 2003, andthe application date is August 13th, 2005) in order to master the end o lie and

treatments or household and non household equipment.In other parts o the world some new legislation will ollow the same objectives.

In addition to manuacturers action in avour o products eco-design, the contributiono the whole electrical installation to sustainable development can be signicantlyimproved through the design o the installation. Actually, it has been shown that anoptimised design o the installation, taking into account operation conditions, MV/LVsubstations location and distribution structure (switchboards, busways, cables),can reduce substantially environmental impacts (raw material depletion, energydepletion, end o lie)

See chapter D about location o the substation and the main LV switchboard.




A0


3 Installed power loads -

Characteristics

The examination o actual values o apparent-power required by each load enablesthe establishment o:

b A declared power demand which determines the contract or the supply o energy

b The rating o the MV/LV transormer, where applicable (allowing or expectedincreased load)

b Levels o load current at each distribution board

3. Induction motors

Current demand

The ull-load current Ia supplied to the motor is given by the ollowing ormulae:

b 3-phase motor: Ia = Pn x 1,000 /(3 x U x x cos )

b 1-phase motor: Ia = Pn x 1,000 / (U x x cos )

where

Ia: current demand (in amps)Pn: nominal power (in kW)

U: voltage between phases or 3-phase motors and voltage between the terminals

or single-phase motors (in volts). A single-phase motor may be connected phase-to-

neutral or phase-to-phase.

: per-unit eciency, i.e. output kW / input kWcos : power actor, i.e. kW input / kVA input

Subtransient current and protection setting

b 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.

b Schneider Electric circuit-breakers, 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).

b I unexpected tripping o 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, lie time can be reduced and even some

devices can be destroyed. In order to avoid such a situation, oversizing o the

switchgear must be considered.

b Schneider Electric switchgears are designed to ensure the protection o motorstarters against short-circuits. According to the risk, tables show the combination ocircuit-breaker, contactor and thermal relay to obtain type 1 or type 2 coordination(see chapter N).

Motor starting current

Although high eciency motors can be ound on the market, in practice their startingcurrents are roughly the same as some o standard motors.

The use o start-delta starter, static sot start unit or variable speed drive allows to

reduce the value o the starting current (Example : 4 Ia instead o 7.5 Ia).

Compensation o reactive-power (kvar) supplied to induction motors

It is generally advantageous or technical and nancial reasons to reduce the currentsupplied to induction motors. This can be achieved by using capacitors withoutaecting the power output o the motors.

The application o this principle to the operation o induction motors is generallyreerred to as power-actor improvement or power-actor correction.

As discussed in chapter L, the apparent power (kVA) supplied to an induction motorcan be signicantly reduced by the use o shunt-connected capacitors. Reductiono input kVA means a corresponding reduction o input current (since the voltageremains constant).

Compensation o reactive-power is particularly advised or motors that operate orlong periods at reduced power.

As noted above cos =kW input

kVA input so that a kVA input reduction will increase

(i.e. improve) the value o cos .

An examination o the actual apparent-power demands o dierent loads: anecessary preliminary step in the design o aLV installation

The nominal power in kW (Pn) o a motorindicates its rated equivalent mechanical poweroutput.The apparent power in kVA (Pa) supplied tothe motor is a unction o the output, the motoreciency and the power actor.

Pa =Pn

cos



A


The current supplied to the motor, ater power-actor correction, is given by:

Icos

cos '=

Ia

where cos is the power actor beore compensation and cos is the power actorater compensation, Ia being the original current.

Figure A4 below shows, in unction o motor rated power, standard motor currentvalues or several voltage supplies.


Characteristics

kW hp 230 V 380 - 400 V 440 - 500 V 690 V

45 V 480 V

A A A A A A

0.18 - 1.0 - 0.6 - 0.48 0.35

0.25 - 1.5 - 0.85 - 0.68 0.490.37 - 1.9 - 1.1 - 0.88 0.64

- 1/2 - 1.3 - 1.1 - -

0.55 - 2.6 - 1.5 - 1.2 0.87- 3/4 - 1.8 - 1.6 - -

- 1 - 2.3 - 2.1 - -

0.75 - 3.3 - 1.9 - 1.5 1.1

1.1 - 4.7 - 2.7 - 2.2 1.6

- 1-1/2 - 3.3 - 3.0 - -

- 2 - 4.3 - 3.4 - -1.5 - 6.3 - 3.6 - 2.9 2.1

2.2 - 8.5 - 4.9 - 3.9 2.8- 3 - 6.1 - 4.8 - -

3.0 - 11.3 - 6.5 - 5.2 3.8

3.7 - - - - - - -

4 - 15 9.7 8.5 7.6 6.8 4.95.5 - 20 - 11.5 - 9.2 6.7

- 7-1/2 - 14.0 - 11.0 - -

- 10 - 18.0 - 14.0 - -7.5 - 27 - 15.5 - 12.4 8.9

11 - 38.0 - 22.0 - 17.6 12.8- 15 - 27.0 - 21.0 - -

- 20 - 34.0 - 27.0 - -

15 - 51 - 29 - 23 17

18.5 - 61 - 35 - 28 21- 25 - 44 - 34 -

22 - 72 - 41 - 33 24- 30 - 51 - 40 - -

- 40 - 66 - 52 - -

30 - 96 - 55 - 44 3237 - 115 - 66 - 53 39

- 50 - 83 - 65 - -

- 60 - 103 - 77 - -

45 - 140 - 80 - 64 4755 - 169 - 97 - 78 57

- 75 - 128 - 96 - -

- 100 - 165 - 124 - -75 - 230 - 132 - 106 77

90 - 278 - 160 - 128 93- 125 - 208 - 156 - -

110 - 340 - 195 156 113

- 150 - 240 - 180 - -

132 - 400 - 230 - 184 134- 200 - 320 - 240 - -

150 - - - - - - -160 - 487 - 280 - 224 162

185 - - - - - - -

- 250 - 403 - 302 - -

200 - 609 - 350 - 280 203

220 - - - - - - -

- 300 - 482 - 361 - -

250 - 748 - 430 - 344 250280 - - - - - - -

- 350 - 560 - 414 - -- 400 - 636 - 474 - -

300 - - - - - - -

Fig. A4: Rated operational power and currents (continued on next page)




A2


kW hp 230 V 380 - 400 V 440 - 500 V 690 V

45 V 480 VA A A A A A

315 - 940 - 540 - 432 313- 540 - - - 515 - -

335 - - - - - - -

355 - 1061 - 610 - 488 354

- 500 - 786 - 590 - -

375 - - - - - - -

400 - 1200 - 690 - 552 400

425 - - - - - - -450 - - - - - - -

475 - - - - - - -500 - 1478 - 850 - 680 493

530 - - - - - - -

560 - 1652 - 950 - 760 551

600 - - - - - - -

630 - 1844 - 1060 - 848 615

670 - - - - - - -

710 - 2070 - 1190 - 952 690750 - - - - - - -

800 - 2340 - 1346 - 1076 780850 - - - - - - -

900 - 2640 - 1518 - 1214 880

950 - - - - - - -

1000 - 2910 - 1673 - 1339 970

Fig. A4: Rated operational power and currents (concluded)

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

The current demand o a heating appliance or an incandescent lamp is easilyobtained rom the nominal power Pn quoted by the manuacturer (i.e. cos = 1)(see Fig. A5).

Fig. A5: Current demands o resistive heating and incandescent lighting (conventional orhalogen) appliances

Nominal Current demand (A)

power -phase -phase 3-phase 3-phase

(kW) 27 V 230 V 230 V 400 V

0.1 0.79 0.43 0.25 0.14

0.2 1.58 0.87 0.50 0.29

0.5 3.94 2.17 1.26 0.72

1 7.9 4.35 2.51 1.44

1.5 11.8 6.52 3.77 2.17

2 15.8 8.70 5.02 2.89

2.5 19.7 10.9 6.28 3.613 23.6 13 7.53 4.33

3.5 27.6 15.2 8.72 5.05

4 31.5 17.4 10 5.77

4.5 35.4 19.6 11.3 6.5

5 39.4 21.7 12.6 7.22

6 47.2 26.1 15.1 8.66

7 55.1 30.4 17.6 10.1

8 63 34.8 20.1 11.5

9 71 39.1 22.6 13

10 79 43.5 25.1 14.4



A3



Characteristics

(2) Power-actor correction is oten reerred to as

compensation in discharge-lighting-tube terminology.Cos is approximately 0.95 (the zero values o V and Iare almost in phase) but the power actor is 0.5 due to the

impulsive orm o the current, the peak o which occurs latein each hal cycle

The currents are given by:

b 3-phase case: Ia =Pn

U3

(1)

b 1-phase case: Ia =Pn

U

(1)

where U is the voltage between the terminals o the equipment.

For an incandescent lamp, the use o halogen gas allows a more concentrated light

source. The light output is increased and the lietime o the lamp is doubled.

Note: At the instant o switching on, the cold lament gives rise to a very brie but

intense peak o current.

Fluorescent lamps and related equipment

The power Pn (watts) indicated on the tube o a fuorescent lamp does not includethe power dissipated in the ballast.

The current is given by:

Iacos

=+P Pn

U

ballast

Where U = the voltage applied to the lamp, complete with its related equipment.I no power-loss value is indicated or the ballast, a gure o 25% o Pn may be used.

Standard tubular fuorescent lamps

With (unless otherwise indicated):

b cos = 0.6 with no power actor (PF) correction(2) capacitorbcos = 0.86 with PF correction(2) (single or twin tubes)b cos = 0.96 or electronic ballast.I no power-loss value is indicated or the ballast, a gure o 25% o Pn may be used.Figure A6 gives these values or dierent arrangements o ballast.

(1) Ia in amps; U in volts. Pn is in watts. I Pn is in kW, thenmultiply the equation by 1,000

Fig. A6: Current demands and power consumption o commonly-dimensioned fuorescent

lighting tubes (at 230 V-50 Hz)

Arrangement Tube power Current (A) at 230 V Tube

o lamps, starters (W) (3) Magnetic ballast Electronic length

and ballasts ballast (cm)

Without PF With PFcorrection correction

capacitor capacitor

Single tube 18 0.20 0.14 0.10 60

36 0.33 0.23 0.18 120

58 0.50 0.36 0.28 150

Twin tubes 2 x 18 0.28 0.18 60

2 x 36 0.46 0.35 120

2 x 58 0.72 0.52 150

(3) Power in watts marked on tube

Compact fuorescent lamps

Compact fuorescent lamps have the same characteristics o economy and long lieas classical tubes. They are commonly used in public places which are permanentlyilluminated (or example: corridors, hallways, bars, etc.) and can be mounted insituations otherwise illuminated by incandescent lamps (see Fig. A7next page).




A4



Characteristics

The power in watts indicated on the tube oa discharge lamp does not include the powerdissipated in the ballast.

Fig. A7: Current demands and power consumption o compact fuorescent lamps (at 230 V - 50 Hz)

Type o lamp Lamp power Current at 230 V

(W) (A)

Separated 10 0.080

ballast lamp 18 0.110

26 0.150

Integrated 8 0.075

ballast lamp 11 0.095

16 0.125

21 0.170

Fig. A8: Current demands o discharge lamps

Type o Power Current In(A) Starting Luminous Average Utilization

lamp (W) demand PF not PF Ia/In Period eciency timelie o(W) at corrected corrected (mins) (lumens lamp (h)

230 V 400 V 230 V 400 V 230 V 400 V per watt)

High-pressure sodium vapour lamps

50 60 0.76 0.3 1.4 to 1.6 4 to 6 80 to 120 9000 b Lighting o

70 80 1 0.45 large halls

100 115 1.2 0.65 b Outdoor spaces150 168 1.8 0.85 b Public lighting

250 274 3 1.4

400 431 4.4 2.2

1000 1055 10.45 4.9

Low-pressure sodium vapour lamps

26 34.5 0.45 0.17 1.1 to 1.3 7 to 15 100 to 200 8000 b Lighting o

36 46.5 0.22 to 12000 autoroutes

66 80.5 0.39 b Security lighting,

91 105.5 0.49 station

131 154 0.69 b Platorm, storageareas

Mercury vapour + metal halide (also called metal-iodide)

70 80.5 1 0.40 1.7 3 to 5 70 to 90 6000 b Lighting o very

150 172 1.80 0.88 6000 large areas by

250 276 2.10 1.35 6000 projectors (or400 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 + fuorescent substance (fuorescent bulb)

50 57 0.6 0.30 1.7 to 2 3 to 6 40 to 60 8000 b 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 b Outdoor lighting

700 731 5.4 3.85 bLow 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 i the voltage alls to less than 50% o their nominal voltage, and willnot re-ignite beore cooling or approximately 4 minutes.

Note: Sodium vapour low-pressure lamps have a light-output eciency which is superior to that o all other sources. However, use othese lamps is restricted by the act that the yellow-orange colour emitted makes colour recognition practically impossible.

Discharge lamps

Figure A8 gives the current taken by a complete unit, including all associatedancillary equipment.

These lamps depend on the luminous electrical discharge through a gas or vapour

o a metallic compound, which is contained in a hermetically-sealed transparentenvelope 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 currentdemands are given or dierent types o lamp (typical average values which maydier slightly rom one manuacturer to another).


25/491




A6


Fig. A9: Estimation o installed apparent power

4.3 Estimation o actual maximum kVA demand

All individual loads are not necessarily operating at ull rated nominal power nornecessarily at the same time. Factors ku and ks allow the determination o themaximum power and apparent-power demands actually required to dimension theinstallation.

Factor o maximum utilization (ku)

In normal operating conditions the power consumption o a load is sometimes lessthan that indicated as its nominal power rating, a airly common occurrence thatjusties the application o an utilization actor (ku) in the estimation o realistic values.

This actor must be applied to each individual load, with particular attention toelectric motors, which are very rarely operated at ull load.

In an industrial installation this actor may be estimated on an average at 0.75 ormotors.

For incandescent-lighting loads, the actor always equals 1.

For socket-outlet circuits, the actors depend entirely on the type o appliances being

supplied rom the sockets concerned.

Factor o simultaneity (ks)

It is a matter o common experience that the simultaneous operation o all installedloads o a given installation never occurs in practice, i.e. there is always some degreeo diversity and this act is taken into account or estimating purposes by the use o asimultaneity actor (ks).

The actor ks is applied to each group o loads (e.g. being supplied rom a distributionor sub-distribution board). The determination o these actors is the responsibilityo the designer, since it requires a detailed knowledge o the installation and theconditions in which the individual circuits are to be exploited. For this reason, it is notpossible to give precise values or general application.

Factor o simultaneity or an apartment block

Some typical values or this case are given in Figure A0 opposite page, and areapplicable to domestic consumers supplied at 230/400 V (3-phase 4-wires). In thecase o consumers using electrical heat-storage units or space heating, a actor o0.8 is recommended, regardless o the number o consumers.

Fluorescent lighting (corrected to cos = 0.86)Type o application Estimated (VA/m2) Average lighting

fuorescent tube level (lux = lm/m2)with industrial refector()

Roads and highways 7 150storage areas, intermittent work

Heavy-duty works: abrication and 14 300assembly o very large work pieces

Day-to-day work: oce work 24 500

Fine work: drawing oces 41 800

high-precision assembly workshops

Power circuits

Type o application Estimated (VA/m2)

Pumping station compressed air 3 to 6

Ventilation o premises 23

Electrical convection heaters:

private houses 115 to 146fats and apartments 90

Oces 25Dispatching workshop 50

Assembly workshop 70

Machine shop 300

Painting workshop 350

Heat-treatment plant 700

(1) example: 65 W tube (ballast not included), fux 5,100 lumens (Im),luminous eciency o the tube = 78.5 Im / W.



A7


Example (see Fig. A):

5 storeys apartment building with 25 consumers, each having 6 kVA o installed load.

The total installed load or the building is: 36 + 24 + 30 + 36 + 24 = 150 kVA

The apparent-power supply required or the building is: 150 x 0.46 = 69 kVA

From Figure A10, it is possible to determine the magnitude o currents in dierentsections o the common main eeder supplying all foors. For vertical rising mainsed at ground level, the cross-sectional area o the conductors can evidently beprogressively reduced rom the lower foors towards the upper foors.

These changes o conductor size are conventionally spaced by at least 3-foorintervals.

In the example, the current entering the rising main at ground level is:

150 x 0.46 x 10

400 3

3

=100 A

the current entering the third foor is:

(36+ 24) x 0.63 x 10

400 3

3= 55 A

4th

floor6 consumers36 kVA

3rd

floor

2nd

floor

1st

floor

groundfloor

4 consumers24 kVA

6 consumers36 kVA

5 consumers30 kVA

4 consumers24 kVA

0.78

0.63

0.53

0.49

0.46

Fig. A11: Application o the actor o simultaneity (ks) to an apartment block o 5 storeys

4 Power loading o an installation

Fig. A10: Simultaneity actors in an apartment block

Number o downstream Factor o

consumers simultaneity (ks)

2 to 4 1

5 to 9 0.78

10 to 14 0.63

15 to 19 0.53

20 to 24 0.49

25 to 29 0.46

30 to 34 0.44

35 to 39 0.42

40 to 49 0.41

50 and more 0.40




A8


4.4 Example o application o actors ku and ks

An example in the estimation o actual maximum kVA demands at all levels o aninstallation, rom each load position to the point o supply is given Fig. A4 (opposite

page).

In this example, the total installed apparent power is 126.6 kVA, which correspondsto an actual (estimated) maximum value at the LV terminals o the MV/LV transormero 65 kVA only.

Note: in order to select cable sizes or the distribution circuits o an installation, the

current I (in amps) through a circuit is determined rom the equation:

I =kVA

U

x 103

3

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

4.5 Diversity actorThe term diversity actor, as dened in IEC standards, is identical to the actor osimultaneity (ks) used in this guide, as described in 4.3. In some English-speakingcountries however (at the time o writing) diversity actor is the inverse o ks i.e. it isalways u 1.

Factor o simultaneity or distribution switchboards

Figure A2 shows hypothetical values o ks or a distribution board supplying anumber o circuits or which there is no indication o the manner in which the total

load divides between them.

I the circuits are mainly or lighting loads, it is prudent to adopt ks values close tounity.

Fig. A12: Factor o simultaneity or distribution boards (IEC 60439)

Circuit unction Factor o simultaneity (ks)

Lighting 1

Heating and air conditioning 1

Socket-outlets 0.1 to 0.2 (1)

Lits and catering hoist (2) b For the most powerul

motor 1 b For the second most

powerul motor 0.75

b For all motors 0.60

(1) In certain cases, notably in industrial installations, this actor can be higher.

(2) The current to take into consideration is equal to the nominal current o the motor,increased by a third o its starting current.

Fig. A13: Factor o simultaneity according to circuit unction

Number o Factor ocircuits simultaneity (ks)

Assemblies entirely tested 0.92 and 3

4 and 5 0.8

6 to 9 0.7

10 and more 0.6

Assemblies partially tested 1.0in every case choose

Factor o simultaneity according to circuit unction

ks actors which may be used or circuits supplying commonly-occurring loads, areshown inFigure A3.



A9



Fig A14: An example in estimating the maximum predicted loading o an installation (the actor values used are or demonstration purposes only)

1

Distributionbox

Workshop A 5 0.8

0.8

0.8

0.8

0.8

0.8

5

5

5

2

2

Lathe

18

3 11

10.80.41

15

10.6

2.5

2.5

15

15

Ventilation

0.28118

112

1Oven

30 fluorescent

lamps

Pedestal-

drill

Workshop B Compressor

Workshop C

no. 1

no. 2

no. 3

no. 4

no. 1

no. 2

no. 1

no. 2

no. 1

no. 2

4

4

4

4

1.6

1.6

18

3

14.4

12

1

1

1

1

2.5

2

18

15

15

2.5

Workshop A

distributionbox

0.75

Powercircuit

Power

circuit

Powver

circuit

Workshop Bdistribution

box

Workshop Cdistribution

box

Maingeneral

distributionboard

MGDB

Socket-

oulets

Socket-oulets

Socket-oulets

Lightingcircuit

Lightingcircuit

Lighting

circuit

0.9

0.9

0.9

0.9

10.6

3.6

3

12

4.3

1

15.6

18.9

37.8

35

5

2

65

LV / MV

Distribution

box

111

0.21

10/16 A

5 socket-

outlets

20 fluorescent

lamps

5 socket-

outlets

10 fluorescentlamps

3 socket-

outlets

10/16 A10/16 A

Utilization Apparent Utilization Apparent SimultaneityApparent SimultaneityApparent Simultaneity Apparentpower actor power actor power actor power actor power(Pa) max. demand demand demand demandkVA max. kVA kVA kVA kVA

Level Level 2 Level 3

4.6 Choice o transormer rating

When an installation is to be supplied directly rom a MV/LV transormer andthe maximum apparent-power loading o the installation has been determined, asuitable rating or the transormer can be decided, taking into account the ollowingconsiderations (see Fig. A5):

b The possibility o improving the power actor o the installation (see chapter L)

b Anticipated extensions to the installation

b Installation constraints (e.g. temperature)

b Standard transormer ratings

Fig. A15: Standard apparent powers or MV/LV transormers and related nominal output currents

Apparent power In (A)

kVA 237 V 40 V

100 244 141

160 390 225

250 609 352

315 767 444

400 974 563

500 1218 704

630 1535 887

800 1949 1127

1000 2436 1408

1250 3045 1760

1600 3898 2253

2000 4872 28162500 6090 3520

3150 7673 4436




A20


The nominal ull-load current In on the LV side o a 3-phase transormer is given by:

Ina x 10

3

=

P

U 3

where

b Pa = kVA rating o the transormer

b U = phase-to-phase voltage at no-load in volts (237 V or 410 V)

bIn is in amperes.

For a single-phase transormer:

Ina x 10

3

=

P

V

where

b V = voltage between LV terminals at no-load (in volts)

Simplied equation or 400 V (3-phase load)

bIn = kVA x 1.4

The IEC standard or power transormers is IEC 60076.

4.7 Choice o power-supply sources

The importance o maintaining a continuous supply raises the question o the use ostandby-power plant. The choice and characteristics o these alternative sources arepart o the architecture selection, as described in chapter D.

For the main source o supply the choice is generally between a connection to theMV or the LV network o the power-supply utility.

In practice, connection to a MV source may be necessary where the load exceeds(or is planned eventually to exceed) a certain level - generally o the order o250 kVA, or i the quality o service required is greater than that normally availablerom a LV network.

Moreover, i the installation is likely to cause disturbance to neighbouring consumers,when connected to a LV network, the supply authorities may propose a MV service.

Supplies at MV can have certain advantages: in act, a MV consumer:

b Is not disturbed by other consumers, which could be the case at LV

b Is ree to choose any type o LV earthing system

b Has a wider choice o economic taris

b Can accept very large increases in load

It should be noted, however, that:

b The consumer is the owner o the MV/LV substation and, in some countries,he must build and equip it at his own expense. The power utility can, in certaincircumstances, participate in the investment, at the level o the MV line or example

b A part o the connection costs can, or instance, oten be recovered i a secondconsumer is connected to the MV line within a certain time ollowing the originalconsumers own connection

b The consumer has access only to the LV part o the installation, access to theMV part being reserved to the utility personnel (meter reading, operations, etc.).However, in certain countries, the MV protective circuit-breaker (or used load-breakswitch) can be operated by the consumer

b The type and location o the substation are agreed between the consumer andthe utility



31/491



B - Connection to the MV publicdistribution network

B2


The term medium voltage is commonly used or distribution systems with voltagesabove 1 kV and generally applied up to and including 52 kV(1). For technical andeconomic reasons, the nominal voltage o medium-voltage distribution networks

rarely exceeds 35 kV.In this chapter, networks which operate at 1000 V or less are reerred to as low-voltage (LV) networks, whereas networks requiring a step-down transormer to eedLV networks are reerred to as medium voltage (MV) networks.

. Power supply characteristics o medium-voltagenetworks

The characteristics o the MV network determine which switchgear is used in the MVor MV/LV substation and are specifc to individual countries. Familiarity with thesecharacteristics is essential when defning and implementing connections.

.2 Dierent types o MV power supply

The ollowing power supply methods may be used as appropriate or the type omedium-voltage network.

Connection to an MV radial network: Single-line service

The substation is supplied by a tee-o rom the MV radial network (overhead orcable), also known as a spur network. This type o network supports a single supplyor loads (see Fig. B).

The substation usually consists o an incoming panel, and overall protection isprovided by a load-break switch and uses with earthing switches as shown inFigure B1.

In some countries, the substation comprises a pole-mounted transormer withouta load-break switch or uses (installed on the pole). This type o distribution is verycommon in rural areas. Protection and switching devices are located remotely romthe transormer. These usually control a main overhead line to which secondaryoverhead lines are connected.

The main characteristics o an MV powersupply are:b The nominal voltageb The short-circuit currentb The rated current used

b The earthing system

(1) According to the IEC there is no clear boundary between

low and medium voltage; local and historical actors play a

part, and limits are usually between 30 and 100 kV(see IEC 601-01-28).

Overhead line

Fig. B1 : Single-line service (single supply)

Power supply at medium voltage


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B5



Large consumers o electricity are invariably supplied at MV.

On LV systems operating at 120/208 V (3-phase 4-wires), a load o 50 kVA might beconsidered to be large, while on a 240/415 V 3-phase system a large consumer

could have a load in excess o 100 kVA. Both systems o LV distribution are commonin many parts o the world.As a matter o interest, the IEC recommends a world standard o 230/400 V or3-phase 4-wire systems. This is a compromise level and will allow existing systemswhich operate at 220/380 V and at 240/415 V, or close to these values, to complywith the proposed standard simply by adjusting the o-circuit tapping switches ostandard distribution transormers.

The distance over which the energy has to be transmitted is a urther actor inconsidering an MV or LV service. Services to small but isolated rural consumers areobvious examples.

The decision o a MV or LV supply will depend on local circumstances andconsiderations such as those mentioned above, and will generally be imposed by theutility or the district concerned.

When a decision to supply power at MV has been made, there are two widely-ollowed methods o proceeding:

- The power-supplier constructs a standard substation close to the consumerspremises, but the MV/LV transormer(s) is (are) located in transormer chamber(s)inside the premises, close to the load centre

2 - The consumer constructs and equips his own substation on his own premises, towhich the power supplier makes the MV connection

In method no. the power supplier owns the substation, the cable(s) to thetransormer(s), the transormer(s) and the transormer chamber(s), to which he hasunrestricted access.

The transormer chamber(s) is (are) constructed by the consumer (to plans andregulations provided by the supplier) and include plinths, oil drains, re walls andceilings, ventilation, lighting, and earthing systems, all to be approved by the supplyauthority.The tari structure will cover an agreed part o the expenditure required to providethe service.

Whichever procedure is ollowed, the same principles apply in the conception andrealization o the project. The ollowing notes reer to procedure no. 2.

2. Preliminary inormation

Beore any negotiations or discussions can be initiated with the supply authorities,the ollowing basic elements must be established:

Maximum anticipated power (kVA) demand

Determination o this parameter is described in Chapter A, and must take intoaccount the possibility o uture additional load requirements. Factors to evaluate atthis stage are:

b The utilization actor (ku)

b The simultaneity actor (ks)

Layout plans and elevations showing location o proposed substation

Plans should indicate clearly the means o access to the proposed substation, withdimensions o possible restrictions, e.g. entrances corridors and ceiling height,together with possible load (weight) bearing limits, and so on, keeping in mind that:

b The power-supply personnel must have ree and unrestricted access to theMV equipment in the substation at all times

b Only qualied and authorized consumers personnel are allowed access to thesubstation

bSome supply authorities or regulations require that the part o the installation operatedby the authority is located in a separated room rom the part operated by the customer.

Degree o supply continuity required

The consumer must estimate the consequences o a supply ailure in terms o itsduration:

b Loss o production

b Saety o personnel and equipment

2 Procedure or the establishment

o a new substation

The consumer must provide certain data to theutility at the earliest stage o the project.




B6


2.2 Project studies

From the inormation provided by the consumer, the power-supplier must indicate:

The type o power supply proposed, and dene:

b The kind o power-supply system: overheadline or underground-cable network

b Service connection details: single-line service, ring-main installation, or paralleleeders, etc.

b Power (kVA) limit and ault current level

The nominal voltage and rated voltage (Highest voltage or equipment)

Existing or uture, depending on the development o the system.

Metering details which dene:

b The cost o connection to the power networkb Tari details (consumption and standing charges)

2.3 Implementation

Beore any installation work is started, the ocial agreement o the power-suppliermust be obtained. The request or approval must include the ollowing inormation,largely based on the preliminary exchanges noted above:

b Location o the proposed substation

b Single-line diagram o power circuits and connections, together with earthing-circuit proposals

b Full details o electrical equipment to be installed, including perormancecharacteristics

b Layout o equipment and provision or metering components

b Arrangements or power-actor improvement i required

bArrangements provided or emergency standby power plant (MV or LV) i eventuallyrequired

2.4 Commissioning

When required by the authority, commissioning tests must be successully completed beore authority is given to energize the installation rom the power supply system.Even i no test is required by the authority it is better to do the ollowing verifcation tests:

b Measurement o ear th-electrode resistances

b Continuity o all equipotential earth-and saety bonding conductors

b Inspection and unctional testing o all MV components

b Insulation checks o MV equipment

b Dielectric strength test o transormer oil (and switchgear oil i appropriate), iapplicable

b Inspection and testing o the LV installation in the substation

b Checks on all interlocks (mechanical key and electrical) and on all automatic

sequencesb Checks on correct protective-relay operation and settings

It is also imperative to check that all equipment is provided, such that any properlyexecuted operation can be carried out in complete saety. On receipt o the certicateo conormity (i required):

b Personnel o the power-supply authority will energize the MV equipment and checkor correct operation o the metering

b The installation contractor is responsible or testing and connection o theLV installation

When nally the substation is operational:

b The substation and all equipment belongs to the consumer

b The power-supply authority has operational control over all MV switchgear in thesubstation, e.g. the two incoming load-break switches and the transormer MV switch(or CB) in the case o a RingMainUnit, together with all associated MV earthing switches

b The power-supply personnel has unrestricted access to the MV equipment

bThe consumer has independent control o the MV switch (or CB) o the transormer(s)only, the consumer is responsible or the maintenance o all substation equipment,and must request the power-supply authority to isolate and earth the switchgear toallow maintenance work to proceed. The power supplier must issue a signed permit-to-work to the consumers maintenance personnel, together with keys o locked-oisolators, etc. at which the isolation has been carried out.

2 Procedure or the establishment

o a new substation

The utility must give specic inormation to theprospective consumer.

The utility must give ocial approval o theequipment to be installed in the substation,and o proposed methods o installation.

Ater testing and checking o the installation byan independent test authority, a certicate isgranted which permits the substation to be putinto service.


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B


The protection against overloading o a transormer is now provided by a digital relaywhich acts to trip the circuit-breaker on the secondary side o the transormer. Suchrelay, generally called thermal overload relay, articially simulates the temperature,

taking into account the time constant o the transormer. Some o them are able totake into account the eect o harmonic currents due to non linear loads (rectiers,computer equipment, variable speed drives).This type o relay is also able topredict the time beore overload tripping and the waiting time ater tripping. So, thisinormation is very helpul to control load shedding operation.

In addition, larger oil-immersed transormers requently have thermostats with twosettings, one or alarm purposes and the other or tripping.

Dry-type transormers use heat sensors embedded in the hottest part o the windingsinsulation or alarm and tripping.

Internal aults

The protection o transormers by transormer-mounted devices, against the eectso internal aults, is provided on transormers which are tted with airbreathingconservator tanks by the classical Buchholz mechanical relay (see Fig. B4). Theserelays can detect a slow accumulation o gases which results rom the arcing oincipient aults in the winding insulation or rom the ingress o air due to an oil leak.This rst level o detection generally gives an alarm, but i the condition deterioratesurther, a second level o detection will trip the upstream circuit-breaker.

An oil-surge detection eature o the Buchholz relay will trip the upstream circuit-breaker instantaneously i a surge o oil occurs in the pipe connecting the main tankwith the conservator tank.

Such a surge can only occur due to the displacement o oil caused by a rapidlyormed bubble o gas, generated by an arc o short-circuit current in the oil.

By specially designing the cooling-oil radiator elements to perorm a concerting action,totally lled types o transormer as large as 10 MVA are now currently available.

Expansion o the oil is accommodated without an excessive rise in pressure by thebellows eect o the radiator elements. A ull description o these transormers isgiven in Sub-clause 4.4 (see Fig. B5).

Evidently the Buchholz devices mentioned above cannot be applied to this design; amodern counterpart has been developed however, which measures:b The accumulation o gas

b Overpressure

b Overtemperature

The rst two conditions trip the upstream circuit-breaker, and the third condition tripsthe downstream circuit-breaker o the transormer.

Internal phase-to-phase short-circuit

Internal phase-to-phase short-circuit must be detected and cleared by:

b 3 uses on the primary side o the tranormer or

b An overcurrent relay that trips a circuit-breaker upstream o the transormer

Internal phase-to-earth short-circuit

This is the most common type o internal ault. It must be detected by an earth aultrelay. Earth ault current can be calculated with the sum o the 3 primary phasecurrents (i 3 current transormers are used) or by a specic core current transormer.

I a great sensitivity is needed, specic core current transormer will be preered. Insuch a case, a two current transormers set is sucient (see Fig. B6).

Protection o circuits

The protection o the circuits downstream o the transormer must comply with theIEC 60364 requirements.

Discrimination between the protective devices upstream anddownstream o the transormer

The consumer-type substation with LV metering requires discriminative operationbetween the MV uses or MV circuit-breaker and the LV circuit-breaker or uses.The rating o the MV uses will be chosen according to the characteristics o thetransormer.

The tripping characteristics o the LV circuit-breaker must be such that, or anoverload or short-circuit condition downstream o its location, the breaker will trip

suciently quickly to ensure that the MV uses or the MV circuit-breaker will not beadversely aected by the passage o overcurrent through them.

The tripping perormance curves or MV uses or MV circuit-breaker and LV circuit-breakers are given by graphs o time-to-operate against current passing throughthem. Both curves have the general inverse-time/current orm (with an abruptdiscontinuity in the CB curve at the current value above which instantaneoustripping occurs).

Fig. B5: Totally lled transormer

Fig. B4: Transormer with conservator tank

Fig. B6:Protection against earth ault on the MV winding

N

3

2

1

HV LV

3

2

1

E/F relayOvercurrent relay

3 Protection aspect




B0


These curves are shown typically in Figure B7.

b In order to achieve discrimination (see Fig. B):All parts o the use or MV circuit-breaker curve must be above and to the right o the

CB curve.

b In order to leave the uses unaected (i.e. undamaged):

All parts o the minimum pre-arcing use curve must be located to the right o the CBcurve by a actor o 1.35 or more (e.g. where, at time T, the CB curve passes througha point corresponding to 100 A, the use curve at the same time T must pass througha point corresponding to 135 A, or more, and so on...) and, all parts o the use curvemust be above the CB curve by a actor o 2 or more (e.g. where, at a current level Ithe CB curve passes through a point corresponding to 1.5 seconds, the use curveat the same current level I must pass through a point corresponding to 3 seconds, ormore, etc.).

The actors 1.35 and 2 are based on standard maximum manuacturing tolerancesor MV uses and LV circuit-breakers.

In order to compare the two curves, the MV currents must be converted to theequivalent LV currents, or vice-versa.

Where a LV use-switch is used, similar separation o the characteristic curves o theMV and LV uses must be respected.

b In order to leave the MV circuit-breaker protection untripped:

All parts o the minimum pre-arcing use curve must be located to the right o theCB curve by a actor o 1.35 or more (e.g. where, at time T, the LV CB curve passesthrough a point corresponding to 100 A, the MV CB curve at the same time T mustpass through a point corresponding to 135 A, or more, and so on...) and, all parts othe MV CB curve must be above the LV CB curve (time o LV CB curve must be lessor equal than MV CB curves minus 0.3 s)

The actors 1.35 and 0.3 s are based on standard maximum manuacturingtolerances or MV current transormers, MV protection relay and LV circuit-breakers.

In order to compare the two curves, the MV currents must be converted to theequivalent LV currents, or vice-versa.

Choice o protective device on the primary side o the

transormerAs explained beore, or low reerence current, the protection may be by uses or bycircuit-breaker.

When the reerence current is high, the protection will be achieved by circuit-breaker.

Protection by circuit-breaker provides a more sensitive transormer protectioncompared with uses. The implementation o additional protections (earth aultprotection, thermal overload protection) is easier with circuit-breakers.

3.3 Interlocks and conditioned operations

Mechanical and electrical interlocks are included on mechanisms and in the controlcircuits o apparatus installed in substations, as a measure o protection against anincorrect sequence o manuvres by operating personnel.

Mechanical protection between unctions located on separate equipment(e.g. switchboard and transormer) is provided by key-transer interlocking.

An interlocking scheme is intended to prevent any abnormal operational manuvre.Some o such operations would expose operating personnel to danger, some otherswould only lead to an electrical incident.

Basic interlocking

Basic interlocking unctions can be introduced in one given unctionnal unit; someo these unctions are made mandatory by the IEC 62271-200, or metal-enclosedMV switchgear, but some others are the result o a choice rom the user.

Considering access to a MV panel, it requires a certain number o operationswhich shall be carried out in a pre-determined order. It is necessary to carry outoperations in the reverse order to restore the system to its ormer condition. Eitherproper procedures, or dedicated interlocks, can ensure that the required operations

are perormed in the right sequence. Then such accessible compartment will beclassied as accessible and interlocked or accessible by procedure. Even orusers with proper rigorous procedures, use o interlocks can provide a urther helpor saety o the operators.

Fig. B7: Discrimination between MV use operation and LVcircuit-breaker tripping, or transormer protection

Fig. B8: MV use and LV circuit-breaker conguration

U1 MV LV U2

D

C

Time

A

B

Current

Minimum pre-arcing

time of MV fuse

Circuit breakertripping

characteristic

B/A u 1.35 at any

moment in timeD/C u 2 at any

current value



B


Key interlocking

Beyond the interlocks available within a given unctionnal unit (see also 4.2), themost widely-used orm o locking/interlocking depends on the principle o key transer.

The principle is based on the possibility o reeing or trapping one or several keys,according to whether or not the required conditions are satised.

These conditions can be combined in unique and obligatory sequences, therebyguaranteeing the saety o personnel and installation by the avoidance o an incorrectoperational procedure.

Non-observance o the correct sequence o operations in either case may haveextremely serious consequences or the operating personnel, as well as or theequipment concerned.

Note: It is important to provide or a scheme o interlocking in the basic design stageo planning a MV/LV substation. In this way, the apparatuses concerned will b

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