DOC 9157-AN/901 Part 5

AERODROME DESIGN

MANUAL

PART 5 ELECTRICAL SYSTEMS

FIRST EDITION - 1983

Approved by the Secretary General and published under his authority

INTERNATIONAL CIVIL AVIATION ORGANIZATION

I C A O 9357 P A R T 8 5 ** = 484343b 0039920 630 W

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Aerodrome Design Manual

(DOC 9157-AN/901)

Part 5

Electrical Systems

First Edition - 1983

I C A O 9357 PART*5 ** W 4B4L4Lh 0019922 403 W

AMENDMENTS

The issue of amendments is announced in the ICAO Bulletin and in the monthly supplements to the Catalogue of ICAO Publications, which holders of this publication should consult. These amendments are available free upon request.

ICAO 9157 PART*5 ** m 4B4L4Lb 0019923 3 4 T m

FOREWORD

Proper design, installation and maintenance of electrical systems fo r nav i - ga t ion a ids , bo th v i sua l and non-visual, are p re requ i s i t e s fo r t he s a fe ty , r egu la r i ty , and ef f ic iency of c iv i l av ia t ion . To t h i s e n d , t h i s manual provides guidance on the design and i n s t a l l a t i o n of electrical systems f o r aerodrome l i g h t i n g and radio naviga- t i o n a i d s .

The electrical systems f o r aerodrome l i g h t i n g and rad io naviga t ion a ids inc lude fea tures which are not usual ly involved in other electrical in s t a l l a t ions . This manual therefore discusses not only the general features of electrical p rac t i ces and instal la t ions but a lso those features which are of spec ia l s ign i f i cance fo r aerodrome i n s t a l l a t i o n s . It is assumed tha t r eade r s of t h e manual w i l l be famil iar with elec- t r ica l c i r c u i t s and general design concepts, but may not be knowledgeable of c e r t a i n f ea tu res of aerodrome i n s t a l l a t i o n s which are less f requent ly encountered in o ther i n s t a l l a t ions . It is impor t an t t o no te t ha t t he material presented in t h i s manual is in tended to complement na t iona l s a fe ty codes r e l a t ed t o electrical i n s t a l l a t i o n s .

The nranual does not discuss electrical systems for bu i ld ings loca ted on a n a i rpo r t o the r t han t he e f f ec t of such buildings on t o t a l power requirements for primary and secondary power suppl ies . Similar ly , the manual does not deal with the maintenance of electrical systems. For guidance on t h i s latter i s sue t he r eade r i s - adv i sed t o r e f e r t o t he A i rpo r t Servgces Manual, (Doc 9137), Part 9, Airport Maintenance Pract ices .

Future ed i t ions o f th i s manual will be improved on the bas i s of experience gained and of comments and suggestions received from users of t h i s manual. Readers of t h i s manual are invi ted to g ive the i r v iews , comments and suggest ions to the Secretary General of ICAO.

iCA0 9357 PART*5 ** - 4B4L4Lb 0039924 286 m

TABLEOFCONTENTS

Paee

Chapter 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-l

1.1 Purpose ............................................................ 5-l 1.2 Organization of the manual ......................................... 5-l

Chapter 2. Electricity Supplies a..........................................* 5-2

2.1 Sources of power ................................................... 5-2 2.1.1 General .......................... ..~.......*.o*- ............. 2.1.2 Primary power sources ....................................... 25; 2.1.3 Secondary power sources ..................................... 5-2 2.1.4 Distribution of intermediate power .......................... 5-3

2.2 Power transfer characteristics ..................................... 5-3 2.2.1 Transfer (switch-over) time requirements ................... .5-3 2.2.2 Continuous power sources .................................... 5-3 2.2.3 Methods of transfer ......................................... 5-5

2.3 Secondary power equipment .......................................... 5-7 2.3.1 Components '5-7 .................................................. 2.3.2 Engine-generator sets ....................................... 5-9 2.3.3 Power transfer switching .................................... 5-10 2.3.4 Uninterruptible power supplies .............................. 5-10 2,3.5 Special secondary power devices ............................. 5-11

2.4 Vaults and shelters for electrical equipment ..................... ..5-11 2.4.1 Shelters .................................................... 5-11 2.4.2 Iocation .................................................... 5-13 2.4.3 Special provisions .......................................... 5-13

2.5 Distribution of power .............................................. 5-14 2.5,1 General ..................................................... 5-14 2.5.2 Primary power feeder circuits ............................... 5-15 2.5.3 Above-ground (overhead) primary distribution systems ..... ,.*5-l 5 205.4 Line-voltage regulators ..................................... 5-15 2.5.5 Power lines ................................................. 5-16 2.5.6 Conductors ................................................... 5-16 2.5.7 Insulators .................................................. 5-17 2.5.8 Iocknuts .................................................... 5-18 2.5.9 Transformers ................................................ 5-18 2.5.10 Capacitors .................................................. 5-19 2.5.11 Circuit interruption devices ................................ 5-19 2.5.12 Lightning protection ........................................ 5-20 2.5.13 Clearances .................................................. 5-20 2.5.14 Grounding ................................................... 5-20 2.5.15 Underground distribution systems ............................ 5-21

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(vi ) Aerodrome Design Manual

Page

Chapter 3 . Elec t r i ca l C i r cu i t s fo r Aerodrome Lighting and Radio Navigation Aids ........................................................... 5-23 3.1

3.2

3.3

3.4

3.5

3.6

3.7

3.8

3.9

Types of e l e c t r i c a l c i r c u i t s ....................................... 5-23 3.1.1 Elec t r i ca l cha rac t e r i s t i c s .................................. 5-23 3.1.2 Series c i r c u i t s ............................................. .- 23 3.1.3 P a r a l l e l c i r c u i t s ........................................... 5-24 3.1.4 Comparison of series and p a r a l l e l l i g h t i n g c i r c u i t s ......... 5-25 Series c i r c u i t r y f o r aerodrome l igh t ing ............................ 5-25 3.2.1 Factors to be considered .................................... 5-25 Para l le l (mul t ip le ) c i rcu i t ry ...................................... 5-41 3.3.1 Use of para l l e l (mu l t ip l e ) c i r cu i t ry in aerodrome l igh t ing .. 5-41 Control of aerodrome l igh t ing systems .............................. 5-42 3.4.2 Control panels .............................................. 5-43 3.4.3 &e of re lays ............................................... 5-44 3.4.4 Interconnection of controls ................................. 5-45 3.4.5 Automatic controls .......................................... 5-45 3.4.6 Radio remote controls ....................................... 5-46 3.5.1 Character is t ics of incandescent lamps ....................... 5-46 3.5.2 Character is t ics sf gaseousdischarge lamps .................. 5-48 Methods of ob ta in ing in tegr i ty and r e l i a b i l i t y f o r aerodrome

l igh t ing ......................................................... 5-49 3.6.1 Definit ion of term ......................................... 5-49 3.6.2 Summary of means of improving e l e c t r i c a l i n t e g r i t y

and r e l i a b i l i t y ........................................... 5-50 Monitoring of aerodrome l i g h t i n g c i r c u i t s .......................... 5-51 3.7.1 Methods of monitoring ....................................... 5-51 307.3 Classes: of monitors .......................................... 5-51 3-7.4 Monitor overr ide controls ................................... 5-52 Elec t r i ca l c i r cu i t s fo r r ad io nav iga t ion a ids ...................... 5-52 3.8.1 Types of radio navigat ion a ids .............................. 5-52 3.8.2 Elec t r i ca l cha rac t e r i s t i c s .................................. 5-52 3.8.3 Control c i rcui ts for radio navigat ion a ids .................. 5-53 3-8.4 Rel i ab i l i t y and i n t e g r i t y of radio navigat ion a ids .......... 5-54 3.8.5 Monitoring of radio navigation aids ......................... 5-54 Acceptance t e s t i n g of aerodrome e l e c t r i c a l c i r c u i t s ................ 5-54 3.9.2 Guarantee period ............................................ 5-55 3.9.3 Inspection procedures ....................................... 5-55 3.9.4 Elec t r i ca l test of ser ies -c i rcu i t equipment ................. 5-57 3.9.5 Elec t r i ca l tests of other cables ............................ 5-59 3.9.6 E l e c t r i c a l t e s t s of regulators .............................. 5-60

3.4.1 Control c i r c u i t r y .......................................... ~5-42

Lamps .............................................................. 5-46

3.7.2 Design of monitoring devices ................................ 5-51

3.9.1 Application ................................................. 5-54

3.9.7 Troubleshooting tests ................................ ......*5-61 3.9.8 E l e c t r i c a l t e s t s of o ther equipment ......................... .- 62 3.9.9 Tests of monitors ........................................... 5-62

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Table of Contents (vii >

* Page

Chapter 4. Underground Electrical Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-63

8

4.1

4.2

4.3

4.4

4.5

Chapter

5.1

5.2

General requirements ............................................... 5-63 4.1.1 Initial considerations ...................................... 5-63 4.1.2 Preconstruction arrangements ................................ 5-63 4.1.3 Methods of installation ..................................... 5-63 Direct burial of cable ............................................. 5-63 4.2.1 Steps of installing ......................................... 5-63 4.2.2 Trenching ................................................... 5-63 4.2.3 Separation between cables ................................... 5-64 4.2.4 Installation of direct-burial cables ...................... ..5-6 5 Installation of ducts (conduit) .................................... 5-66 4.3.1 Installation techniques and procedures ............=.........5-6 6 Manholes and handholes ............................................. 5-67 4.4.1 Selection ................................................... 5-67 4.4.2 Location .................................................... 5-69 4.4.3 Stubs ....................................................... 5-69 4.4.4 hardware .................................................... 5-69 4.4.5 Two-section manholes ........................................ 5-69 Installation of underground cables ................................. 5-69 4.5.1 Preparation of ducts ........................................ 5-69 4.5.2 Cable pulling in ducts ...................................... 5-69 4.5.3 Installation of cable in manholes and handholes ........... ..5-7 1 4.5.4 Pressurized type coaxial cables ............................. 5-72 4.5.5 Cable installation in saw cuts ............................. 5-73 4.5.6 Cable marking ............................................... 5-74 4.5.7 Enclosures for connections .................................. 5-75

5. Cables for Underground Service at Aerodromes . . . . . . . . . . . . . . . . . ...5-77

Features of the cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-77 5.1.1 Characteristics of cables for underground service ......... ..5-7 7 5.1.2 Classes of service .......................................... 5-79 5.1.3 Causes of cable damage ...................................... 5-80 Cable connections .................................................. 5-82 5.2.1 Cable splices ............................................... 5-82 5.2.2 Taped splices ............................................... 5-83 5.2.3 Connector kits for aerodrome lighting ..................... ..5-8 5 5.2.4 Coaxial cables .............................................. 5-85 5.2.5 Connection of conductors .................................... 5-88

ICAO 9357 PART*5 ** = 4 8 4 3 4 L b 0039927 T95 W

1.1 PURPOSE

1.1.1 To ensure the regular i ty and safe ty of av ia t ion , i t i s necessary that aero- drome l igh t ing and radio navigational aids have h igh in tegr i ty and r e l i a b i l i t y . It is considered that the probabi l i ty of f a i l u r e of well designed and maintained l i g h t i n g and radio a ids a t a c r i t i c a l moment i s extremely low.

1.1.2 The following material i s intended as a guide t o t h e recommended electrical engineer ing pract ices for design and i n s t a l l a t i o n of new systems and the modification of existing systems of aerodrome f ixed l i gh t ing and of d i s t r ibu t ion of power t o r a d i o navigation aids. It does not imply t h a t e x i s t i n g i n s t a l l a t i o n s , i f d i f f e r e n t , are wrong and should be changed automatically. It does mean t h a t some of the earlier designs adopted are not recommended for repe t i t ion s ince they have been superseded by later thinking. Because of the differences i n engineer ing s tyle and equipment i n d i f f e r e n t count r ies , th i s material es tabl ishes only basic design pr inciples . It i s not intended t o i l lustrate de ta i led des ign or par t icu lar p ieces of equipment o r systems unique t o any one State.

1.1 .3 The electrical systems f o r aerodrome v i s u a l a i d s and navigation systems require good q u a l i t y i n s t a l l a t i o n s and considerat ion for features which are not usually involved i n o t h e r e l e c t r i c a l i n s t a l l a t i o n s . This manual d i scusses the genera l fea tures of e l e c t r i c a l p r a c t i c e s and in s t a l l a t ions w i th emphasis on those features which are less commonly involved or have special s ign i f icance for aerodrome operations. It is assumed tha t those us ing th i s manual w i l l be famil iar with electrical circuits and general pract ices but may not be knowledgeable of cer ta in fea tures of aerodrome i n s t a l l a t i o n s which are less f requent ly encountered in other electrical sys t em. Some of these f e a t u r e s a r e t h a t mast e I e c t r i c a 1 c i r c u i t s are i n s t a l l e d underground, s e r i e s c i r c u i t s a r e used fo r most l ight ing systems, higher re l iabi l i ty i s required of the input power sources, and rapid, automatic transfer to secondary power i n case of power f a i lu re s . Each aerodrome i s unique, and i t s e l ec t r i ca l i n s t a l l a t ion shou ld be designed t o provide economically power and cont ro l which i s sa fe , r e l i ab le , and easily maintained.

1.2 ORGANIZATION OF THE MANUAL

1.2.1 This manual provides information on the E lec t r ic i ty Suppl ies in Chapter 2, Elec t r i ca l C i r cu i t s fo r Aerodrome Lighting and Navigation Aids i n Chapter 3, Underground Electrical Systems i n Chapter 4 , and Cables f o r Underground Service a t Aerodromes i n Chapter 5.

5- 1

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cBlLpTEB2

ELECTRICITY SUPPLIES

2.1 SOURCES OF POWER

2.101 General

2.1.1.1 The primary sources of power f o r aerodromes should be determined before the designs of the aerodrome l igh t ing ins ta l la t ions and the rad io naviga t ion a ids are i n i t i a t e d . The electrical power f o r these i n s t a l l a t i o n s i s usua l ly on ly a small p a r t o f t h e electrical power used by the aerodrome. . Whether the visual and radio navigat ion a i d s b e i n g i n s t a l l e d are f o r a new aerodrome or for modernizat ion and expansion of a n exis t ing aerodrome, the sources of power should be a n a l y z e d f o r a v a i l a b i l i t y , c a p a c i t y , r e l i a b i l i t y , p r a c t i c a l i t y f o r t h e p r o p o s e d i n s t a l l a t i o n , and for fu ture expans ion . This analysis should include both the pr imary power source and the secondary power sou rce required by Annex 10, Volume I, 2.9 and Annex 14, 8.1 f o r u s e i n cases o f f a i l u r e o r malfunction of the primary power source.

2.1.2 Primary power sources

2.1.2.1 The primary sources of power f o r most aerodromes are feeders f rom a widely in te rconnec ted e lec t r ic i ty ne twork ou ts ide the aerodrome, usua l ly f rom e i ther a commer- c ia l o r a public mains supply. In some cases t h e power may come from a l o c a l g e n e r a t i n g p l an t o r f rom a l imi t ed d i s t r ibu t ion sys t em. Two independent incoming power sources are des i rab le for major aerodromes , ins tead of a s ingle p r imary power source. They should come from widely separated sections of the e l e c t r i c i t y n e t w o r k beyond the aerodrome with each supp ly ing s epa ra t e c i r cu i t s that would p r o v i d e i n t e g r i t y of f a c i l i t i e s i f one fa i led . Preferab ly , these sources w i l l have separa te feeders f rom separa te subs ta t ions and w i l l a lso be f rom different generators . Other supply arrangements may be used depending on the s e c u r i t y , r e l i a b i l i t y , statistics, or economics appl icable to a p a r t i c u l a r s i t u a t i o n .

2.1.2.2 This power i s usua l ly supp l i ed a t h igher vo l tage (over 5 000 v o l t s ) t o t h e aerodrome main power substat ion.

2.1.3 Secondary power sources

2.1.3.1 Most aerodromes with aerodrome l ight ing and radio navigat ion a ids should be provided with secondary electrical power f o r t h e a i d s r e q u i r e d as a minimum for opera- t ions . The circuits a n d f a c i l i t i e s t o be provided with secondary power va ry w i th t he most c r i t i ca l class o r ca t egory of f l i g h t o p e r a t i o n s . The aerodrome f a c i l i t i e s f o r which a secondary power supply i s recommended are i n d i c a t e d i n Annex 14, Chapter 8 f o r v i s u a l a i d s and i n Annex 10, Volume I, P a r t I, Chapter 2 f o r r a d i o n a v i g a t i o n a i d s . Those f a c i l i t i e s f o r which secondary power i s requi red should be a r ranged to au tomat ica l ly connec t to the secondary power supply on f a i l u r e of the pr imary source power . 2.1.3.2 Sources of secondary power. As recommended i n Annex 14 , Chapter 8, sou rces of secondary power may be independent public power sources or stand-by power u n i t s .

5- 2

I C A O 9357 PARTS5 t t 48434Lb 0039929 868

P a r t 5.- Electrical Systems 5-3

2.1.3.3 Inde endent commercial o r u b l i c main ower source. For aerodromes with the primary SUPPLY o! e l e c t r i c i t y t r o m a s!ngle source: separate independent electrical transmission power l i n e s may be used to provide secondary power. These independent power sources are not usua l ly connec ted to the aerodrome l i g h t i n g and radio navigat ion a ids loads bu t can be au tomat ica l ly connec ted to these loads in case of f a i l u r e of t h e primary power source. These independent power sources may be i n a r e se rve s t a tus on ly o r may be supp ly ing e l ec t r i ca l power t o o t h e r f a c i l i t i e s o n the aerodrome. An independent source supplying power t o o t h e r f a c i l i t i e s s h o u l d have adequate capacity to provide the power f o r t h e more e s s e n t i a l aerodrome l igh t ing and r ad io nav iga t ion a ids i n addi t ion to the usual load or switching arrangements should be provided to disconnect from i t s usual load as i t i s connec ted to the l igh t ing and rad io a ids load . The improvement i n i n t e g r i t y of operations provided by independent power sources depends on the s epa ra t ion and independence of th i s source f rom the p r imary source . I f the two sources come from interconnected distribution networks, a f a i l u r e i n t h e n e t w o r k may cause bo th sources to fa i l . An independent power source may be used as a secondary power s o u r c e i f i t has the capac i ty to supply i ts own load. p lus the aerodrome l i g h t i n g and r ad io a ids l oad and is s o separa ted tha t any s ing le cause of power f a i l u r e of t h e primary source w i l l n o t i n t e r f e r e w i t h power from the other source. Unless the independent source is completely isolated from the primary source and will not be overloaded upon f a i l u r e of the primary source, local secondary power should be provided f o r t h e v i s u a l and r ad io nav iga t ion a ids e s sen t i a l t o t he ope ra t ions o f t he ae rodrome .

2.1.3.4 Independent local power source. Some aerodromes may h a v e t u r b o a l t e r n a t o r motor u n i t s which are used to supply power t o n o n - c r i t i c a l f a c i l i t i e s . These l o c a l power sources may be used as the secondary source of power f o r cr i t ical aerodrome l i g h t - i n g and rad io naviga t iona l a ids . If the primary power f a i l s , t h e c r i t i ca l l i g h t i n g and r ad io a ids are t r a n s f e r r e d a u t o m a t i c a l l y t o t h e l o c a l power source. If the l o c a l power source has adequate capacity, the l i g h t i n g and rad io a ids load may be i n a d d i t i o n t o t h e

source may need to d i sconnec t some of t he non-c r i t i ca l l oad be fo re connec t ing t o t he c r i t i ca l l i gh t ing and r ad io a ids l oad .

e usual load . I f the capac i ty of t h e l o c a l power source i s l i m i t e d , t h e l o c a l power 2.1.3.5 Local power to primary source. Another arrangement is t o s u p p l y t h e power f o r t h e aerodrome l i g h t i n g and rad io naviga t iona l a ids f rom turbo-a l te rna tor motor u n i t s which may also be supplying power t o o t h e r f a c i l i t i e s . I f t h i s s o u r c e of power f a i l s , t h e cr i t ical l i g h t i n g and r ad io a ids l oad may be t r ans fe r r ed au tomat i ca l ly t o t he primary power s o u r c e f o r t h e aerodrome.

2.1.3.6 Stand-by power sources. Secondary power sources may be engine-generator sets, or turbine generators from which electrical power can be obtained and which can be automatical ly connected to the f a c i l i t i e s r e q u i r i n g s e c o n d a r y power. The maximum load which can be connected should be within the capacity of the s tand-by uni ts . Stand-by uni ts with capaci t ies ranging f rom 50 t o more than 1 000 kilovolt-amperes are used as secondary power s o u r c e s f o r a i r p o r t s . The secondary power source should be capable of supplying power f o r a time per iod tha t exceeds the maximum time needed t o r e s t o r e power from the primary source. Engine-generator sets are o f t en expec ted t o ope ra t e fo r 2: t o 72 hours without refuel l ing. Other secondary power sou rces , u sua l ly fo r small loads , may be b a t t e r y u n i t s , f u e l cells , etc.

2.1.4 Dis t r ibu t ion of intermediate power

2.1.4.1 The vol tage from the primary power source i s usual ly reduced a t the aero- drome subs ta t ion to an in te rmedia te vo l tage (2 000 t o 5 500 v o l t s ) f o r d i s t r i b u t i o n

ICAO 7357 P A R T 8 5 t t 484343b 0037730 5 8 T

5-4 Aerodrome Design Manual

Table 2-1. secadary P a m Supply &q&xem3 for Visual +s Radio Aide (From h x 14 and Amex 10)

IhaJay C l a s s i f i c a t i o n

Non-iImtnment

precisian approach category I1

SRe MR NB m facility

ICAO 9157 P A R T * 5 ** 4841416 0039933 416 =

P a r t 5.- E l e c t r i c a l Systems 5-5

within the aerodrome. This power i s usua l ly d i s t r ibu ted by a "para l le l" sys tem to the var ious t ransformer s ta t ions for fur ther step-down of v o l t a g e t o match the input vol tage of the equipment. Two independent incoming electrical supplies taken from widely separated sect ions of t h e e l e c t r i c i t y network beyond the aerodrome are recommended. Wi th in the aerodrome, re l iab i l i ty in the supply of power t o the ind iv idua l s ta t ions can be improved by using a closed r ing high vol tage input c i rcui t wi th balanced vol tage pro tec t ion on the d i s t r ibu t ion t ransformers o r by using a double loop system from independent primary sources operating as open r ings feeding two transformers a t each s ta t ion. This l a t te r system i s i l l u s t r a t e d i n F i g u r e 2-1. If a centralized monitoring system of the loop switches a t each s t a t ion and of f a u l t c u r r e n t s l i k e l y t o o c c u r i n each sect ion are used practically complete el imination of power f a i l u r e s t o t h e t ransformer s ta t fons can be achieved. Simpler arrangements providing lesser r e l i a b i l i t y may be used a t smaller a i rpo r t s .

2.2 POWER TRANSFER CHARACTERISTICS

2.2.1 Transfer (switch-over) time requirements

2.2.1.1 When the primary power supply to the more cr i t ical v i s u a l a i d s , f a c i l i t i e s , and r ad io nav iga t ion a ids f a i l s , t he l oad must be t ransferred to the secondary power source. The secondary power source must be s t a r t e d and speed and voltage stabilized before the load i s t ransferred.

2.2.1.2 The t ransfer , o r swi tch-over , times permitted depend on the most cri t ical instrument classification of the aerodromes operation. Annex 14, Chapter 8, and Annex 10, Volume I, Part I, Attachment C l i s t t h e maximum permiss ib le t ransfer times f o r t h e components of aerodrome lighting systems and radio aids associated with non-instrument, non-precision, and precision approach runway categories I, 11, and 111. (See Table 2-1. )

2.2.2 Continuous Dower sources

2.2.2.1 Certain types of lamps cannot be res tar ted for several minutes i f there i s a break in the cur ren t th rough the lamp of more than a few t en ths of a second. Some types of radio navigation and computer devices allow no in t e r rup t ion of power. It i s neces- sary to provide an uninterrupt ible or near cont inuous source of power when the primary power s o u r c e f a i l s t o cater to such equipment. Some devices, such as some computers, are capable of accomodat ing on ly very l imi ted f luc tua t ions of frequency or voltage and requi re a t ru ly un in t e r rup t ib l e power supply.

2.2.3 Methods of t r a n s f e r

2.2.3.1 The following methods are suggested as poss ib le ways t o r e s t o r e t h e power Supply within the specified maximm t r ans fe r times. It i s advantageous t o group loads with similar l i m i t i n g t r a n s f e r times s o tha t they may be cont ro l led a t the t ransformer supply or a t the feeder dis t r ibut ion connect ions f rom the same secondary source.

a ) Z-minute t r a n s f e r time. Where a 21ninute t r a n s f e r time is permissible , local gasol ine or diesel engine-generator or gas turbine-generator sets with automatic or remote s tar t ing and switching are sa t i s f ac to ry . In th i s 2=inute per iod the engine o r tu rb ine can be s ta r ted and the speed and vol tage regula t ion can be s tab i l ized .

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15-second t r a n s f e r time. Where a 15-second t r a n s f e r time is required, s tandby d iese l and gasoline engine-generator sets with rapid-s tar t c a p a b i l i t y and fast-acting automatic switching or an independent source with automatic t ransfer switching can be used.

10-second t r a n s f e r time. Where a 10-second t r a n s f e r time is required, secondary power u n i t s w i t h s u i t a b l e s t a r t i n g and switch-over capabili ty can be used.

One-second t r a n s f e r t i m e . Where a one second switch-over time is required, one of the fol lowing two methods are usua l ly used for th i s r ap id t r ans fe r of power. One method is t o start the s tand-by diesel engine or gas turbine-generator set as soon as the RVR is of the order of 600 m and operate the more c r i t i c a l l i g h t i n g and rad io a ids f rom th i s generator set with automatic t ransfer to the pr imary power source in case the secondary power fails. The cr i t ical load power should continue t o be furnished by the secondary power s o u r c e u n t i l an RVR of 800 m is reached on a f i rm t rend of improvements. The second method is t o automatically switch-over to a sa t i s fac tory independent power supply.

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Near ze ro t r ans fe r time. Very f a s t - ac t ing ( swi t ch ing i n 0.3 second o r less) automatic t ransfer devices which can switch the load from the operating stand-by generator to the primary source are r equ i r ed fo r l i g h t s u s i n g some types of discharge lamps in order to maintain the discharge. Another method of obtaining a near-zero t ransfer time is t o use an inertfa f lywheel-driven generator which is capable of maintainfng the power supply during the start-up of the secondary power source.

Zero t r a n s f e r time. For t hose f ac i l i t i e s r equ i r fng un in t e r rup t ib l e power and accept ing on ly l imi ted var ia t ions of voltage or frequency, battery-driven s ta t ic inve r t e r ( s ) o r gene ra to r ( s ) ( s ee F igu re 2-2) may be used. Although the secondary power t ransfer should usua l ly be accomplished in on ly severa l seconds , the b a t t e r y s e t ( s ) s h o u l d be capable of operat ing the f a c i l i t i e s f o r a minimum of 15 minutes wlthout recharging.

2.3 SECONDARY POWER EQUIPMENT

2.3.1 Components

2.3.1.1 Secondary electrical power should be of such qua l i t y t ha t i t w i l l provide t h e r e l i a b i l i t y , a v a i l a b i l i t y , and voltages and frequencies needed by the f a c i l i t y . The major items of secondary power equipment commonly used f o r aerodrome l ighting and rad io naviga t ion a ids are engine-generator sets, power-transfer switching devices, batteries, and ba t t e ry cha rge r s t o fu rn i sh power fo r s t a r t i ng t he eng ine gene ra to r s , and v a u l t s o r s h e l t e r s f o r t h i s equipment. Less o f t en u sed , u sua l ly fo r spec ia l f ac i l i t i e s , are u n i n t e r r u p t i b l e power (UPS) systems, standby battery-power systems, solar or wind

' generators with bat tery system, independent generat ing devices such as thermoelectr ic , n u c l e a r , o r f u e l c e l l s . The secondary power equipment should be located as close as is p r a c t i c a l t o t h e i n p u t of t h e f a c i l i t i e s s e r v e d .

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a 2.3.2 Engine-generator sets 2.3.2.1 The basic secondary power engine-generator set cons is t s of a prime mover, a genera tor o r a l te rna tor , a s t a r t i ng dev ice , s t a r t i ng con t ro l s , and a fue l t ank o r supply. Engine-generator sets for secondary power u n i t s are u s u a l l y i n 100 t o 500 kilovalt-amperes capacities but may range from 50 t o 1 000 k i lovol tamperes i n capacity.

a ) Prime movers. The prime movers f o r most secondary power u n i t s are - gasoline, diesel , or gas engines or turbines, the choice being based on cos t and a v a i l a b i l i t y of fue ls . These prime movers are usua l ly ava i lab le i n standardized s i z e s with adequate power to handle the ki lovol tampere ra t ing of the generator . The prime m v e r s f o r most major aerodromes are rapid-start types which can start automatically, s t ab i l i ze t he speed , and be connected to t he l oad w i th in 10 seconds.

Generators. The generator , usual ly an a l ternator , i s mechanically coupled t o the prime mover and provides secondary electrical power at the frequency, voltage, and power r a t i n g of t he un i t . These generators may be e i ther s ing le phase o r th ree phase. They should have high e f f ic iency in conver t ing mechanica l energy to electrical energy.

Star t ing devices . Most secondary power engine-generator sets use ba t t e ry packs t o s t o r e energy f o r s t a r t i n g . Because of the in f requent use , shor t opera t ing per iods , h igh s ta r t ing cur ren t demands, and cos t , lead-acid type bat ter ies are used most f r equen t ly fo r s t a r t i ng t hese uni t s . The b a t t e r y pack (of ten a set of ba t t e r i e s connec ted i n series and/or parallel) must be capable of providing the voltage and current needed to s t a r t t he eng ine w i th in t he r equ i r ed time limits and under the most severe conditions (usually a low temperature of -7C) a t which the secondary power u n i t i s expected to operate. A battery charger with over-current and over-charge cont ro l i s permanently connected t o t h e e l c t r i c a l power to main ta in the s tored energy in the ba t te r ies . The ba t te ry pack should be well ventilated to prevent accumulation of hydrogen gas and should be protected from arcs, sparks, or flames which could cause an explosion of any accumulated gas. Nickel-cadmium b a t t e r i e s may be used where special conditions warrant their high init ial cost . Flywheels, pneumatic-pressure vessels, other-than-battery stored-energy devices are used infrequent ly for engine s tar t ing because of un re l i ab i l i t y o r cos t .

S ta r t ing cont ro ls . The cont ro ls for the engine-genera tor set are usually automatic start with the sensor for primary power f a i l u r e as par t of the t ranfer switching device. Manual o r remote controls are sometimes u s e d f o r f a c i l i t i e s w i t h low cri t ical requirements. Once i t i s s t a r t e d , speed and power are automatical ly regulated by the engine and the electrical load is connected by the t ransfer swi tch . The engine generator should operate automatically without adjustment or other a t tent ion. Transfer of power back t o the primary source and stopping the engine may be automatic or by remote control.

Fuel supply. Hquid fuel for secondary power is usua l ly s to red i n t anks near the engine generator location. The capaci ty of the fue l t anks should be adequate for the maximum operating time expected of t h e

5-1 0 Aerodrome Design Manual

engine-generator. Some a u t h o r i t i e s r e q u i r e a minimum of 72 hours supply. Others design for a lesser time per iod , bu t the time period usual ly should be a t least twice t h e maximum durat ion expected of condi t ions that could require the use of secondary power. Fuel tanks and connections should meet a l l safety requirements and should provide convenient access fo r r e fue l l i ng . These t anks shou ld a l so p rov ide arrangements f o r t e s t i n g f o r c o n t a m i n a t i o n o f t h e f u e l , e s p e c i a l i y the accumulation of water i n t h e t a n k .

2.3.3 Power t ransfer swi tch ing

2.3.3.1 A s u i t a b l e t r a n s f e r d e v i c e is needed f o r t r a n s f e r r i n g power frcim the pr imary source to the secondary source . For manual s t a r t i n g a n d c o n t r o l t h i s may be a s i m p l e swi t ch o r r e l ay t ha t d i sconnec t s t he l oad f rom one power source and connects i t t o t h e o ther . Addi t iona l cont ro ls are needed fo r au tomat i c t r ans fe r . These a r e u sua l ly combined i n t o a s ing le con t ro l un i t o r cub ic l e . Such a u n i t should be capable of sens ing the fa i lure o f p r imary power, i n i t i a t i n g t h e s t a r t i n g of t h e pr ime mover of the secondary generator set, determining that the vol tage and f requency of the generator have s tab i l ized adequate ly , and connec t ing the load to the genera tor . This un i t may a l so d i sconnec t non-es sen t i a l l oads and f ac i l i t i e s wh ich are n o t t o be energized by t h e secondary source and t ransfer these loads back t o t h e p r i m a r y s o u r c e a f t e r t h a t power has been restored. The swi tches o r re lays for d i sconnec t ing and connec t ing the load should have the capaci ty to handle the r a t ed l oad of the generator . The func t ioning of t hese swi t ches o r r e l ays i s similar f o r e i t h e r 2 d n u t e , 15-second, or l s e c o n d t r a n s f e r times, although more rap id-ac t ing re lays may be needed f o r t h e s h o r t e s t t r a n s f e r time. For a 2-minute t r a n s f e r , t h e power f a i l u r e s e n s o r s may delay a few seconds i n d e t e r - mining i f t h e p r i m a r y power h a s f a i l e d o r i s o n l y f l u c t u a t i n g and a l s o t o d e t e r m i n e 22 the secondary power has s t ab i l i zed . Fo r a lfi-second t r a n s f e r , t h e s e n s o r s must respond i n less than 3 seconds each because the quick s tar t ing engines need 10 seconds to start and t o s t a b i l i z e . F o r t r a n s f e r times of 1 second or less, time i s t o o s h o r t t o start the engine , bu t the load can be switched from one power sou rce t o ano the r ope ra t ing source w i th in t h i s time limit; however, the power f a i l u r e s e n s o r must respond within a few cycles.

2.3.4 Uninterrupt ible power s u p p l i e s (UPS) systems

2.3.4.1 An u n i n t e r r u p t i b l e electric power supply i s n e c e s s a r y f o r e l e c t r o n i c o r other equipment that performs a cr i t ica l func t ion and requires cont inuous, d is turbance- f r e e electric power to ope ra t e p rope r ly .

2.3.4.2 UPS equipment. The u n i n t e r r u p t i b l e power supply (UPS) sys tem cons is t s o f one or more UPS modules, an energy-storage battery, and accesso r i e s as r e q u i r e d t o provide a r e l i a b l e a n d h i g h q u a l i t y power supply. The UPS sys t em i so l a t e s t he l oad f rom the pr imary and secondary sources and i n t h e e v e n t of a power in t e r rup t ion p rov ides regulated power t o t h e c r i t i ca l l o a d f o r a spec i f i ed pe r iod . (The b a t t e r y t y p i c a l l y h a s a 151ninute capaci ty when operat ing a t fu l l load . ) (See F igure 2-2.)

a ) UPS module. A UPS module is t h e s ta t ic power convers ion por t ion of t h e UPS system and consis ts of a r e c t i f i e r , an inver te r , and assoc ia ted cont ro ls a long w i t h synchroniz ing , p ro tec t ive , and auxi l ia ry devices . UPS modules may be designed t o o p e r a t e either i n d i v i d u a l l y o r i n parallel.

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P a r t 5.- E l e c t r i c a l Systems 5-1 1 - b) Redundancy. A nonredundant UPS system is s u i t a b l e f o r most operat ions.

However, i f t h e e x p e n s e i s j u s t i f i e d , a redundant UPS conf igura t ion (see Figure 2-3) may be used t o p r o t e c t a g a i n s t module f a i l u r e o r v e r y frequent primary power f a i l u r e s .

c) UPS ba t te ry . The bat tery should be a heavy-du ty i ndus t r i a l un i t of t h e lead-cadmium type having an ampere-hour r a t i n g s u f f i c i e n t t o s u p p l y d i r e c t c u r r e n t t o t h e i n v e r t e r as required by t h e UPS system manufac tu re r ' s i n s t a l l a t ion i n s t ruc t i0ns . r The b a t t e r y i s usua l ly furnished with two-t ier racks; however, where space is l imi t ed t h ree - tier racks may be necessary.

d ) Remote alarms. The UPS equipment should be supplied with a remote-alarm p a n e l t o be i n s t a l l e d i n the opera t ing space se rved by t h e UPS u n i t o r in another cont inuously occupied room, such as a guard off ice . Since UPS equipment rooms are usua l ly una t tended; addi t iona l remote ind ica t ing devices should be provided to monitor the environmental control and f i re alarm system of UPS module and b a t t e r y rooms.

e) UPS and b a t t e r y room requirements. The UPS modules and t h e i r a s s o c i a t e d b a t t e r y set s h o u l d b e i n s t a l l e d i n s e p a r a t e rooms. Construct ion should be of a permanent type. The wa l l s epa ra t ing t he UPS module room from t h e b a t t e r y room should be f ireproof (1-hour r a t i n g ) . When f e a s i b l e , space should be provided i n t h e UPS module and ba t t e ry rooms f o r t h e add i t ion o f fu tu re UPS equipment.

f ) Environmental control. Both t h e UPS module and ba t te ry rooms should be provided wi th an envi ronmenta l cont ro l sys tem to main ta in the p rescr ibed room condi t ions. Each environmental control system should 'consis t of a primary system with a secondary system capabi l i ty . Upon f a i l u r e of the pr imary environmental control system, automatic t ransfer to the second- ary system should occur and should sound an alarm ind ica t ing t he need for maintenance.

2.3.5 Special secondary power devices

203.5.1 Other secondary power devices which may b e u s e d f o r s p e c i a l f a c i l i t i e s are' s tandby ba t te ry power sys tems, wi th o r wi thout dc to ac inve r t e r s ; pho tovo l t a i c or wind generators with battery systems and with or without dc t o ac inver te rs ; independent generat ing devices , such as thermoelec t r ic , nuc lear , o r chemica l fue l cells; and iner t ia-f lywheel generators . The manufacturer 's information should explain the func t ion ing and i n s t a l l a t ions fo r u s ing t hese dev ices .

2.4 VAULTS AND SHELTERS FOR ELECTRICAL EQUIPMENT

2.4.1 S h e l t e r s

2.4.1.1 Most electrical e q u i p m e n t o r a i r p o r t l i g h t i n g a n d o t h e r f a c i l i t i e s i s loca ted i n vau l t s o r spec ia l she l t e r s fo r p ro t ec t ion f rom the wea the r and fo r be t t e r s ecu r i ty . Subs t a t ions fo r h igh vo l t age are usual ly outdoors , and medium v o l t a g e d i s t r ibu t ion t r ans fo rmers are o f t e n p o l e mounted or placed on fenced transformer pads. Most e l e c t r i c a l v a u l t s are above ground and made of f i reproof materials. Reinforced

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Part 5.- Electrical Systems 5-1 3

conc re t e fo r t he f l oo r s and concrete , concrete or c inder block, and/or br ick for the walls are materials commonly used i n t h e s e v a u l t s . The use of such materials reduce the hazard of electric shock, shorting of e l e c t r i c a l c i r c u i t s , a n d f i r e h a z a r d s Prefabri- cated metal s t ructures are occasional ly used as she l t e r s fo r t r ans fo rmers and engine- generator sets. These vau l t s are used t o house t h e power d i s t r i b u t i o n and control equipment, secondary power equipment, and the various devices used to provide power and con t ro l fo r t he a i rpo r t l i gh t ing sys t ems . These vaults should be of adequa te s i ze t o contain the necessary equipment without crowding. These vau l t s may be divided into moms f o r b e t t e r s e g r e g a t i o n of equipment and a c t i v i t i e s .

2.4.2 Loestion

2.4.2.1 Elec t r i ca l vau l t s shou ld no t be located where they would in f r inge on obsta- cle l imi ta t ion sur faces . The dis tances f rom the control tower to the vaul ts should be sho r t enough to avoid excess ive vo l tage d rop in the cont ro l cab les . The permissible length of these cables varies w i t h t h e s i z e of the cab le , the cont ro l vo l tage , and the types of control relays used, but some of the longer control systems limit the l ength of cont ro l cab les to about 2 250 metres. Vehicular access to the vaul t s in a l l types of weather conditions i s necessary and minimum c o n f l i c t w i t h a i r c r a f t t r a f f i c is desirable . The location should be convenient for connect ing to the appropriate l ight ing c i rcui ts and f a c i l i t i e s t o keep feeder cable lengths as shor t as i s p rac t i ca l . The vaul ts should be i so la ted f rom o ther bu i ld ings and faci l i t ies to prevent the spread of f i r e s o r explosions, except the shel ters for secondary engine-generator sets may be near the e l e c t r i c a l v a u l t t o r e d u c e c a b l e l e n g t h and s i z e and t o s impl i fy the power t r ans fe r system. Aerodsoaes with approach lighting systems may need separate approach l ighting vaul t s for each approach l igh t ing system. For major aerodromes, some au thor i t i e s u se a vault near each end of t h e runway or approach l ight ing system to more eas i ly a r r ange fo r i n t e r l eav ing o f t he l i gh t ing c i r cu i t s and t o improve i n t e g r i t y of the systems.

2.4.3 Special provisions

2.4.3.1 As spec ia l pu rpose bu i ld ings , e l ec t r i ca l vau l t s may r equ i r e spec ia l f ea tu re s t o provide safety and re l iable performance of t he equipment. Some of these features are as follows:

a) Vent i la t ion. Provide adequate vent i la t ion to prevent t ransformer temperatures exceeding the values prescribed by the manufacture. Most of the electrical hea t losses must be removed by vent i la t ion ; on ly a minor par t can be d i s s ipa t ed by the vaul t walls. Some electrical codes recommend 20 square centimetres of clear g ra t ing area p e r k i lovol t - ampere of transformer capacity. In l o c a l i t i e s w i t h above-average temperatures, such as t rop ica l o r sub t rop ica l a r eas , t he g ra t ing area should be increased or supplemented by forced vent i la t ion .

Access. Adequate access should be provided for repairs , maintenance, i n s t a l l a t i o n , and removal of equipment.

Drainage. All vauxts should be provided with drainage. When normal drainage is not possible, provide a sump p i t t o p e r m i t t h e u s e of a por tab le pump.

Security. Each e lec t r ica l vaul t should be equipped to de te r inadver ten t o r premeditated access by unauthorized persons. This secur i ty i s necessary to prevent interference with equipment operation and to protect those persons from possible electric shock. Some methods used

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- 5-1 4 Aerodrome Design Manual are barred and screened windows, heavy-duty metal doors with padlocks, and securi ty fencing.

Vaul t l ight ing. Electrical vaul t s should be well i l l u m i n a t e d f o r u s e e i t h e r day o r n i g h t . T h i s l i g h t i n g i s usual ly provided by i n t e r i o r l i g h t s of a s i ze , t ype , and l oca t ion t o p rov ide good v i s i b i l i t y i n a l l areas. Poor v i s i b i l i t y c a n i n c r e a s e t h e p o t e n t i a l f o r a c c i d e n t s r e s u l t i n g i n electrical shock or improper control and adjustments-

Local communications. Most e lectr ical vaul ts should be provided with convenient and re l iable comrmnicat ions to the control tower , o ther vau l t s , and pe rhaps o the r f ac i l i t i e s o r o f f i ces . Spec ia l t e l ephone o r i n t e r c o m n i c a t i o n s y s t e m s may avo id ou t s ide i n t e r f e rence w i th t hese c i rcu i t s , bu t o ther dependable a r rangements can be used .

Electrical conduits. Electrical vaul t s should be provided with a s u f f i c i e n t number of conduits and cable entrance accesses t o a v o i d later m o d i f i c a t i o n o f t h e s t r u c t u r e t o p e r m i t t h e i n s t a l l a t i o n o f a d d i t i o n a l i n p u t o r o u t p u t c i r c u i t s . These cables en t rances are usual ly through underground conduits which may be connected t o e x i s t i n g c a b l e d u c t s , d i rec t -bur ia l cab les , o r unused condui t s ava i lab le for fu ture expans ion . Unused conduits should be plugged, and conduits with cables should be sealed.

I n s t a l l a t i o n s of equipment . Arrange the equipment , especial ly the l a r g e r items such as r e g u l a t o r s , d i s t r i b u t i o n t r a n s f o r m e r s , c o n t r o l panels, and c i r cu i t s e l e c t o r o r c o n t r o l d e v i c e s , t o p r o v i d e a s imple , unc lu t t e red , uncrowded plan. This arrangement should consider safety, e spec ia l ly p ro t ec t ion f rom h igh vo l t age electrical connections, as w e l l as access t o t h e equipment and controls. The electrical c i r c u i t s s h o u l d a l s o be arranged i n a s imple pat tern wherever possible . Fol low the app l i cab le electric s a f e t y c o d e s f o r i n s t a l l i n g a l l electrical c i r c u i t s and controls.

2.5 DISTRIBUTION OF POWER

2.5.1 General

2.5.1.1 The equipment discussed i n t h i s s e c t i o n relates o n l y t o t h a t u s e d i n t r ansmi t t i ng electrical power f o r t h e aerodrome l igh t ing and r ad io nav iga t ion a ids between t h e main aerodrome subs t a t ion ( s ) and t he l i gh t ing vau l t s o r t he l oca l s i t e dis t r ibut ion t ransformers . Descr ipt ions of equipment are i n g e n e r a l terms of character- ist ics and needs and usually are n o t r e l a t e d t o s p e c i f i c t y p e s o r items of equipments. Types of equipment and number of devices w i l l vary great ly with the s ize and complexi ty of the aerodrome. Economics i s an impor t an t pa r t o f i n s t a l l a t ions , and only equipment w h i c h c o n t r i b u t e s t o p e r f o r m a n c e , s a f e t y , r e l i a b i l i t y , a n d i n t e g r i t y s h o u l d b e u s e d . The circui ts and equipment used should provide for a reasonable expansion of f a c i l i t i e s . E f f i c i e n t u s e of electrical power i s always a des i r ab le goa l , bu t t he power c o s t f o r aerodrome l ighting and r ad io nav iga t ion a ids i s u s u a l l y a r a t h e r small p a r t of t h e t o t a l aerodrome energy cost and should not be emphasized to the point of overly increasing in s t a l l a t ion cos t s o r o f d imin i sh ing pe r fo rmance , s a fe ty , o r r e l i ab i l i t y . Fo l low the l o c a l electrical safety codes.

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ICAO 9357 PART*5 ** 4 8 4 3 4 3 6 0039943 3b5 W

P a r t 5.- Electrical Systems 5-1 5 -

2.5.2 Primary power f eede r c i r cu i t s

2.5.2.1 Primary power is usually reduced i n v o l t a g e a t the main aerodrome subs ta t ion f o r d i s t r i b u t i o n on t h e aerodrome. For major aerodromes, t h i s power a t t h e f i r s t s t a g e may be a t an intermediate voltage (usually 5 000 t o 20 000 vo l t s ) , bu t fo r smaller, less complex aerodromes, t h i s power may be d i s t r ibu ted at a medium voltage (usually 1 000 t o 5 000 vo l t s ) . The d is tance and t o t a l l o a d on t h e c i r c u i t are impor t an t f ac to r s i n determining the vol tage level of t ransmission. For an intermediatevol tage dis t r ibut ion system, power i s o f t en run t o subs t a t ions nea r l a rge power usage areas where i t is reduced t o medium v o l t a g e f o r l o c a l d i s t r i b u t i o n . A combination of these voltage dis t r ibut ion systems may be used. Primary power is t ransmit ted f rom the main subs ta t ion t o t h e l o c a l s u b s t a t i o n o r d i s t r i b u t i o n sites usual ly as mult i -phase c i rcui ts by above ground (overhead) circuits, underground circuits, or a combination of t hese c i r cu i t s . Above ground c i r c u i t s are less e x p e n s i v e t o i n s t a l l and are usually used i f f e a s i b l e , bu t these c i rcu i t s may be more exposed t o damage and i n some areas are a hazard t o a i r c r a f t and create electromagnet ic interference for other 'equipment . Underground feeder cables are usua l ly i n s t a l l ed i n duc t s , bu t sometimes d i r e c t b u r i a l i s used. Each type of c i r c u i t , whether overhead o r underground, involves specific types of equipment and design.

2.5.3 Above-ground (overhead) primary distribution systems

2.5.3.1 The following factors should be considered in the design of an overhead power d i s t r i b u t i o n system:

2.5.4

a) Application. Use overhead d i s t r i b u t i o n i n l i e u of underground d i s t r ibu - t i o n wherever feasible.

b) Capaci ty . Provide for spare capaci ty in each port ion of t h e c i r c u i t . Peak loads do not relate d i r ec t ly t o spa re capac i ty .

c) Wire s ize . Select the wire s i z e i n accordance with the current-carrying capaci ty required and, where appl icable , the vol tage-drop l imitat ion.

Linevol tage regula tors

2.5.4.1 Regulators are used for cor rec t ion of l i n e v o l t a g e v a r i a t i o n s r e s u l t i n g f r o m changing loads o r u t i l i ty company input vol tage changes. Do not use these regulators to correct for excessive voltage drops. Booster transformers .which co r rec t fo r vo l t age drop should be used only i n rare instances as, i n most cases, correct design e l iminates excessive voltage drop.

a) Rating. Choose t h e r a t i n g of the regulat ing devices in accordance with t h e amount of regulation required.

b) Selection. Choose the type of regulators f rom f ixed capaci tors , switched capacitors, multistep (motor-driven tap changing) regulators, and induction (stepless voltage change) regulators.

c) Multistep or induction regulators. Provide l ine-drop compensation for automatic operation when these regulators are used on more than one source or when more than one regulator is used on a s i n g l e c i r c u i t .

I C A O 9157 PARTU5 t t m 4 8 4 3 4 3 6 0019942 2TL

5-1 6 - Aerodrome Design Manual 2.5.5 Power lines

2.5.5.1 Select the type of power l i nes i n acco rdance w i th the type o f c i r cu i t involved and the conditions to which i t is subjected from the following:

a) Open wire (bare or weatherproof) on i n s u l a t o r s .

b) Aerial cable , se l f -supported or supported by a h i g h s t r e n g t h steel (messenger) cable, consisting of insulated, bundled, single-conductor cable or multiple-conductor cable.

2.5.5.2 Line support materials:

a) Poles. Wood, concre te ( re inforced wi th p res t ress ing or pos t tensioning) , or metal (steel o r aluminum) may be used. Concrete or metal poles should be used only where they are more economical o r special considerat ions warrant their use .

b) Footings. Provide footings, or reinforcements of the pole but t -end, as required by foundation conditions.

c) Configuration. Armless cons t ruc t ion fo r aerial l i n e s is usua l ly less costly than crossarm construction and i t s use is preferred, as i s multi- conductor secondary cable with a la rge neut ra l conductor as the support- i n g member over individual supported conductors. Use crossarms mainly f o r equipment support .

d ) Guys and anchors. Provide guys and anchors t o support poles o r l i n e towers against horizontal unbalanced loads caused by angles , corners , and terminations of l ines and where required because of extreme wind loadings. Consul t manufacturers ' catalogues for types of ear th anchors and design data. Select equ ipmen t su i t ab le fo r t he pa r t i cu la r so i l conditions and the cons t ruc t ion method t o be used.

2.5.6 Conductors

2.5.6.1 Size l imitat ions. Limit the use of pole-line conductors in accordance with Table 2-2 for an economical system from the installation, operational, and maintenance points of view. Special ins tances may requi re l a rger conductors . In a l l instances be s u r e t h a t t h e t y p e and s i z e of conductors used provides adequate s t rength for the span lengths and loading conditions.

Table 2-2

Size

Not la rger than Not smaller than Conductor type

Copper . . . . . . 13.0 mm2 170 m2 Aluminum . . . . . . .

8.3 m 2 110 mm2

ICAO 9157 PARTb5 bt m 4 B 4 1 4 1 b 0019943 138 m

Part 5.- E l e c t r i c a l Systems 5-1 7 -

2.5.6.2 Composition. Base wire s i z e on the ranges shown i n Table 2-2. Primary wire sizes usually should not be less than 13.0 nun2 copper o r 33.0 mm2 aluminum. For primary conductors, select from the following:

a ) Bare copper conductor, stranded or solid copper.

b) Bare aluminum-alloy conductor, stranded or solid aluminum-alloy.

c ) Bare aluminum conductor, steel reinforced.

d ) Bare high-strength all-aluminum alloy conductor.

2.5.6.3 Special conductors. In special instances, use of the following conductors may be appropriate for primary conductors:

a) Insulated conductor, copper or aluminum, preassembled non-metallic- sheathed or metallic-sheathed, steel-cable-supported (messenger- supported) aerial cable is used where necessary to avoid exposure to open wire hazards, for example, h i g h r e l i a b i l i t y service i n heavy storm areas.

b) Compound conductor materials such as copper-clad steel, aluminum-clad steel, galvanized stee1, o r bronze are used to provide high s t rength and corrosion resistance.

2.5.6.4 Dissimilar conductors. Where i t i s necessary to connect aluminum conductors t o copper conductors, appropriate connectors specifically designed for such use should be i n s t a l l e d i n accordance with the instructions of the manufacturer.

2.5.7 Insu la tors

2.5.7.1 Types of insu la tors . Select from the following list the type of i n su la to r to support bare o r weatherproof insulated conductors.

Suspension type, single or multiple.

Spool type.

Une-post type (one-piece porcelain on a b o l t f o r mounting on crossarms o r on a saddle on t h e s i d e of a pole).

Strain type (suspension uni ts wi th s t rength equal or exceeding tensi le s t rength of the conductor usually having one to three extra disk sec t ions and arcing horns or r ings) .

Pin type (porcelain, usually two o r more sepa ra t e she l l s cemented together, with an internal thread for screwing onto a wood or metal pin).

Combinations. Various t y p e s of i n su la to r s may be combined; f o r example, s t ra in type for anchor po les o r t e rmina t ions wi th e i ther p in o r l ine- pos t types for l ine insu la t ion . Une-pos t t y p e s are considered to be both less expensive and superior to pin types.

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5-1 a - Aerodrome Design Manual

2.5.7.2 If overhead lines are used in location sensitive to electromagnetic inter- ference, the insulators should be of a static-free type.

2.5.8 Lo cknu t s

2.5.8.1 Hardware components should be provided with locknuts to avoid loose connect- ions which could cause static. Locknuts mst be threaded and of a type which will prevent loosening of the connection when wood members shrink.

2.5.9 Transformers

2.5.9.1 Mounting of transformers. Mount transformers on poles or at ground level. When sheet metal enclosures are not tamperproof. ground mounted units should be provided with a fenced enclosure. A concrete or-brick structure should be used where adverse weather conditions make such an installation advisable.

a) Single-pole mounting. For single-pole mounting, limit the size of single-phase or three-phase units in accordance with approved practices.

b) Pole-platform mounting. Pole-platform mounting (two-pole structures) should not be used, except in instances where other methods are not satisfactory. For installations of 225 or 500 kilovolt-ampers, pad-mounted compartmental-type transformers become an attractive economic alternative to pole-mounted units.

c) Ground mounting. For ground mounting on a concrete base, there is no kilovoltampere limit. Usually tamperproof transformers (classified as pad-mounted compartmental-type units) should not be specified for ratings of over 500 kilovolt-amperes.

2.5.9.2 Ratings. Select transformers with standard kilovoltampere ratings and input and output voltage as single-phase or three-phase units. Transformers with input voltage taps for selecting the most suitable input voltage level may be desirable for some installations.

2.5.9.3 Indoor installations. Oil-immersed (flammable) transformers should not be installed indoors except in vaults conforming to the requirements of the applicable electric code. Such vaults should be provided only when other types of transformers are less economical or are prohibited by special considerations. Where such a vault is not provided, select transformers for indoor installation from the following:

a) high-fire-point , liquid-immersed; b) dry-type, ventilated;

c) dry-type, sealed tank; and

d) nonhazardous gas-insulated.

2.5.9.4 Toxic insulation fluids. The transformers should not use poly-chlorinated biphenyl (PCB) or other highly toxic insulation fluids. Leakage or mishandling of these chemicals during maintenance testing can be hazardous to personnel.

I Part 5.- Electrical Systems 5.-19 - I a 2.5.10 Capacitors

2.5.10.1 Types of capacitors. U s e shunt capac i tors to improve the power f a c t o r of the load carried by t h e c i r c u i t . In applying capacitors, consider the following:

a) Fixed capacitance. Fixed capacitance is t h e amount of capac i tance tha t can be applied continuously without excessive voltage rise a t reduced load.

b) Switched capacitance. Switched capacitance is an addi t iona l amount of capacitance that can be applied, i f p rov i s ion is made to swi t ch o f f t h i s addi t iona l amount a t reduced demand.

c) Capacitor switching. Select a type of capacitor switching that i s su i t ab le fo r t he cond i t ion a t hand. Possible choices include remote cont ro l of the capacitor-switching device, t ime-clock control, power- f ac to r r e l ay con t ro l o r vo l t age - sens i t i ve r e l ay con t ro l .

2*5.10.2 Location of capac i to r s . I n s t a l l c apac i to r s i n banks on poles, at ground l e v e l , o r i n a subs ta t ion as near ly as poss ib l e t o t he cen t ro id of the area where correct ion is required.

2.5.11 Ci rcu i t in te r rupt ion devices

2.5.11.1 Fuses. After consideration of the necessary current-carrying capaci t ies , in te r rupt ing du t ies , and time-current melting and c lear ing characteristics, select fuses from the following types: a

a) open f u s i b l e l i n k ;

b) expulsion type;

I c) boric-acid type; and d) current-l imiting type 2.5.11.2 Ci rcu i t b reakers . Coard ina te the c i rcu i t b reaker ra t ing wi th the load ' in te r rupt ing du ty and wi th c i r cu i t b reake r s and fuses ahead of o r after t h e c i r c u i t breaker.

2.5.11.3 Automatic c i r c u i t r e c l o s e r s . U s e of au tomat ic rec losers for o ther than overhead l i n e l o a d s may cause problems from high-resistance ground faults. If an auto- matic c i r c u i t r e c l o s e r i s used , cons ide r t he r e l i ab i l i t y and continuity requirements of the service. Reclosers may cons i s t of a circuit-breaker or multiple switching devices. Reclosers operate s o t h a t a f a u l t e d c i r c u i t may be opened and then, e i ther instantane- ously or with del iberate time delay, reclosed. Up t o three reclosures with varying time in t e rva l s may be used. Co-ordinate automatic c i rcui t reclosers with fuses or c i rcui t breakers on t he same c i r c u i t .

2.5.11.4 Switches. Use swi tches to loca l ize defec t ive por t ions of aerial and under- ground c i r c u i t s and t o accomplish dead-circuit work. Select from one of the following pr incipal types:

ICAO 9157 P A R T 8 5 X * 4 8 4 1 4 1 b 001994b 947

5-2 0 Aerodrome Design Manual

a) Nonload-break switches. Use nonload-b ' reak switches only for the inter- rup t ion o t c i r c u i t s tha t c a r r y no apprec iab le load . Select the t ype appl icable , depending on c i r cu i t impor t ance , l oad , vo l t age , and f au l t c i r c u i t d u t y . The types ava i lab le are porce l a in d i sconnec t fu se c u t o u t s , p l a i n o r f u s e d s i n g l e - p o l e a i r disconnect. switches, and disconnect fuse cutouts of var ious types. Msconmect ing and horn-gap switches may a l so be used as nonload-break switches.

b) Load-break switches. had-break switches are provided wi th an in te r - rupt ing device capable of disconnect ing c i rcui ts under load. Fuse cutouts, which are des igned to be load-break and load- in te r rupter switches, are ava i l ab le . Vacuum switches also provide load-break capab i l i t y .

2.5.12 , Lightn ing pro tec t ion

2.5.12.1 To determine the requirements for l i gh tn ing p ro t ec t ion , cons ide r .ove rhead ground wire, open or expuls ion gaps , and d i s t r ibu t ion- type surge ( l igh tn ing) arresters. The weather should a lso be considered. Protect ion for l ightning-induced surges may be unnecessary in areas where annual l ightning storms are few. Adminis t ra t ive po l icy or l o c a l electric power company prac t ice should usua l ly be fo l lowed. Select the p rope r a r r e s t e r in accordance wi th the chosen bas ic impulse insu la t ion leve l for which the c i r c u i t must be b u i l t .

2.5.13 Clearances

2.5.13.1 Provide the necessary hor izonta l and ver t ica l c learances f rom ad jacent phys i ca l ob jec t s , such as bu i ld ings , s t ruc tu res , and o the r electric l i n e s , as requ i r ed by t h e a p p l i c a b l e electrical safety code. Provide against cont ingency interferences, such as broken poles , broken crossarm, and.broken c i rcui t conductors . Provide for c learance condi t ions a r i s ing f rom mul t ipurpose jo in t use of poles. See t h e a p p l i c a b l e electrical sa fe ty code fo r c l imb ing space c l ea rances , j o in t u se , and supply conductor protect ion.

2.5.1.4 Grounding

2.5.14.1 For information on grounding of overhead dis t r ibut ion systems, use the app l i cab le electrical safe ty code or Adminis t ra t ive po l icy . For sa fe ty p rovide g round- i n g o r a l l equipment and s t ructures associated with electrical systems to prevent shock from s ta t ic o r dynamic vol tages . Maximum ground resistance should not exceed values s p e c i f i e d i n t h e a p p l i c a b l e electrical safety code. Consider the source of electric power, capac i ty , magni tude o f fau l t cur ren t , and method of system grounding, as they affect t h i s r e s i s t a n c e .

2.5.14.2 Ground rods. Ground rods may b e u s e d e i t h e r s i n g l y o r i n c l u s t e r s . D r i v e the ground rods to ground water l e v e l f o r a n e f f e c t i v e a n d permanent i n s t a l l a t i o n . Provide or corrosion prevention by a proper choice of metals o r by ca thod ic p ro t ec t ion . Where ground water cannot be reached, chemtcals such as magnesium su lpha te (MgS04,) o r copper sulphate (CuS04) may be used t o improve s o i l c o n d u c t i v i t y where necessary. Manu- facturers of ground rods can provide data on such treatment. Provide for easy mainte- nance and periodic testing. Although driving ground rods deeper (sectional type) may be more e f f ec t ive t han mu l t ip l e rods , in many cases, s o i l v a r i a t i o n s a n d p o s s i b l e b e d r o c k may make provis ion of add i t iona l rods less expensive.

ICAO 9357 PART85 $8 = 484143b 0039947 883 W

Part 5.- Electrical Systems 5.-2 1 -

2.5.14.3 Grounding network. A buried network of ground conductors w i l l assure an e f f ec t ive s a fe ty ground i n poor s o i l and w i l l e l iminate large vol tage gradients a t s u b s t a t i o n s f o r u t i l i t y aerodrome interconnections. Mesh spacings of 3 t o 3.5 metres are commonly used and usually such spacings can control surface voltage gradients even though the ground resistance may be re la t ive ly h igh .

2.5.14.4 Water pipe connections. The electrical system may be grounded t o a water Supply system except where nonmetallic pipes, cathodically protected metallic pipes , or insulat ing coupl ings are inco rpora t ed i n t he water pipe system. The water pipe connec- t ion should be supplemented by other grounding electrodes where required by the appl icable electrical sa fe ty code.

2.5.14.5 Combination of grounding methods. Where t h e ground resistance i n a n existing system i s high, two or more of the aforementioned methods may be combined t o e f f e c t improvement.

2.5.14.6 Ground connections. Wires running from protective devices (for example, gaps, grading rings, expulsion or protection tubes, and surge arresters) t o ground should be kept as straight: and shor t as possible. Where bends are necessary they should be of l a r g e r a d i i t o keep the surge impedance as low as possible.

2.5.14.7 Overhead ground w i r e s . Where overhead ground wires are used for p ro tec t ion o f e l e c t r i c l i n e s , a ground connection should be provided a t the base of each pole from the overhead ground wire t o a wire loop or a ground p l a t e o r t o a driven rod, depending on the ex i s t ing so i l cond i t ions . Use of wire wraps o r po le bu t t p l a t e s i s allowed only i n areas of very low s o i l r e s i s t i v i t y .

2.5.14.8 Measurement of ground resis tance. Two methods of measuring ground res i s tance are:

a) Three-electrode method. In the th ree-e lec t rode method, two test elec- t rodes are used t o measure res i s tance of the th i rd e lec t rode , the ground point. A self-contained source of a l t e rna t ing cu r ren t and a ba t t e ry operated vibrator source equipment providing d i rec t read ings are avail- able.

b) Fall-of-potential method. The f a l l a f - p o t e n t i a l method involves an ' ungrounded a l te rna t ing cur ren t source which c i r c u l a t e s a measured c u r r e n t t o ground. Voltage readings taken, of the connection to auxiliary grounds, al low use of Ohm's l a w to determine the ground resis tance.

2.5.15 Underground dis t r ibut ion systems

2.5.15.1 Primary power d i s t r i b u t i o n c i r c u i t s i n c e r t a i n a r e a s on and near aerodromes must be i n s t a l l e d underground. Although underground ins t a l l a t ions cos t more than over- head systems, radio interference problem6 o r t h e p r o x i m i t y o f t h e l i g h t i n g f a c i l i t i e s t o a reas of aircraft operat ions of ten ' requires the use of underground dis t r ibut ion systems. Underground c i r c u i t s may be i n s t a l l e d by d i r e c t b u r i a l o r by the pull-in method (pul l ing the cables through conduits) . Direct bu r i a l of d i s t r i b u t i o n c i r c u i t s i s usual ly less cos t ly than ins ta l la t ion in duc ts (pu l l - in method), but because of the poorer protec- t i on , d i r ec t bu r i a l is usually used only for small loads where re l iab i l i ty requi rements

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are low. Medium-voltage direct burial cable should be provided with a metal armor covering or shield for protection against mechanical injury. Where corrosion resistance i s important, armored cables may require a plastic or syntheticrubber jacket over the armor. The underground distribution circuits used for aerodrome lighting and radio navigation facilities are pull-in circuits.

2.5.15.2 Details of the installation of underground distribution systems are given in Chapter 4 , and characteristics of cable suitable or underground service are given in Chapter 5.

3.1.1

ICAO 7157 PART*5 ** - 4B4L~Lb 0039949 656 -

CHAPTER3

EIzclRIcAL CIRCUITS FOB& liEwDMw LIGHTIHG'd#DRADI0rWIGATIoI!IAIDS

3.1 TYPES QF ELECTRICAL CIRCUITS

Electrical characteristics - --

3.1.1.1 Electrical power for aerodrome lighting aids is almost entirely alternating current (ac). (Some control circuits are direct current (dc) and energy for starting secondary power engines or for some uninterruptible power systems is stored in batter- ies.) This alternating current is usually 50 to 60 hertz. Both series and parallel circuits are used in these lighting installations. Most of the aerodrome lights are energized by series circuits, but the incoming power is distributed by parallel cir- cuits, and some single units or shorter circuits of lights may'be energized by parallel circuits. Sequence-flashing lights of approach lighting systems, some floodlights, and some obstacle lights are the more important lighting systems using parallel circuits.

3.1.2 Series circuits

3.1.2,1 The circuit elements of serFes circuits are connected in a string with the same current flowing in each element. The circuit is one continuous loop starting and ending at the input power source. If a fixed input voltage were connected to the load, the current in the circuit would vary with the connected load; however, constant-current regulators will maintain a constant current independent of the load on the circuit. Thus the same current will flow in a long circuit as in a shorter circuit and will remain the same even if some of the lamps fail. This constant current means that a short-circuit across the output of a constant-current regulator is a no-load condition and an open-circuit is an overload. In a simple direct-connected series circuit, a lamp failure causes an open-ciruit; hence, it it necessary to provide a by-pass device, such as a fused film cutout or an isolating transformer , as part of each lighting fixture. Isolating transformers are preferred for aerodrome lighting circuits.

3.1.2.2 Advantages of series lighting circuits. Some of the advantages of series circuits for aerodrome lighting are:

a) all lamps are operating at the same current and thus at the same inten- sity. This uniform intensity and appearance of the lamps are helpful;

. . b) a single-conductor cable of one conductor size and insulation voltage

rating can be used throughout the circuit;

c) intensity control of the lights can be obtained over a wide range;

d) the circuit may have a single ground fault at any point along the circuit without affecting the operation of the lights; and

e) ground faults are easy to locate.

3.1.2.3 Disadvantages of series lighting circuits. The major disadvantages of series circuits when used for lighting are:

5-23

I C A O 9357 P A R T M S ** m 484343b 0039950 378 m

5-2 4 - Aerodrome Design Manual a) i n s t a l l a t i o n c o s t s are h igh - the cons tan t -cur ren t regula tor and the

i so l a t ing t r ans fo rmers o r by -pass dev ices add apprec i ab ly t o t h i s cos t ;

b ) poor e f f ic iency , p r imar i ly of the moving-coi l type constant-current r e g u l a t o r , i n u s e of electrical power;

c) a l l components - cable , i so la t ing t ransformers and lamp socke t s - must be i n s u l a t e d f o r f u l l v o l t a g e i f i s o l a t i n g t r a n s f o r m e r s are not used;

d) an open-c i rcu i t fau l t anywhere i n t h e c i r c u i t makes t h e e n t i r e c i r c u i t inoperat ive and possibly may damage the c a b l e i n s u l a t i o n o r t h e constant-current regulator ; and

e ) l o c a t i o n of f a u l t s , e s p e c i a l l y o p e n - c i r c u i t f a u l t s , may b e d i f f i c u l t

3.1.3 P a r a l l e l c i r c u i t s

3.1.3.1 The c i r c u i t e l e m e n t s o f p a r a l l e l ( m u l t i p l e ) c i r c u i t s are connected in para l l e l ac ross t he conduc to r s t o wh ich t he i npu t vo l t age is applied. In theo ry t he same vo l t age i s a p p l i e d t o e a c h l i g h t ; however, the cur ren t th rough the conductors causes a d e c r e a s e i n v o l t a g e ( l i n e d r o p ) w h i c h f o r l o n g e r c i r c u i t s may reduce appreci- ab ly t he vo l t age t o , and consequen t ly t he i n t ens i ty of, t h e l i g h t s a t t h e f a r end of the c i r c u i t . In d i s t r i b u t i o n c i r c u i t s where t h e v o l t a g e may be high and the current low, t h e v o l t a g e d r o p i n t h e l i n e s is less impor tan t , and para l le l circuits are o f t en u sed f o r s u c h c i r c u i t s . If i n t e n s i t y c o n t r o l o f t h e l i g h t s i s required, tapped transformers of i n d u c t i o n v o l t a g e r e g u l a t o r s may be u sed , bu t t hese i nc rease t he cos t o f t he i n s t a l l - a t i o n and reduce the e f f ic iency of t h e c i r c u i t .

3.1.3.2 Advantages of p a r a l l e l l i g h t i n g circuits. Some of the advantages of p a r a l l e l c i r c u i t s f o r aerodrome l i g h t i n g are:

a j lower c o s t of t h e i n s t a k l a t i o n , e s p e c i a l l y i f v o l t a g e r e g u l a t i o n a n d . i n t e n s i t y c o n t r o l are not requi red ;

b) more e f f i c i e n t u t i l i z a t i o n of electrical power;

c) e a s y t o a d d t o o r r e d u c e a n e x i s t i n g c i r c u i t ;

d ) t h e c i r c u i t s are more f a m i l i a r t o most people;

e) c a b l e f a u l t s , e s p e c i a l l y o p e n - c i r c u i t f a u l t s , may be easier t o l o c a t e ;

f) an open-circui t may n o t d i s a b l e the e n t i r e c i r c u i t ; a n d

g) these c i rcu i t s do no t need by-pass devices and may n o t n e e d i s o l a t i n g transformers .

3.1 .3 .3 Disadvantages of p a r a l l e l l i g h t i n g c i r c u i t s . Some of the major disadvant- a