design&const.22kvohl kenya

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KENYA STANDARD KS 1877:2010 ICS 29.260.20

© KEBS 2010 First Edition 2010

Electrical power transmission and distribution — Guidelines for the application design, planning and construction of medium voltage overhead power lines up to and including 22 kV, using wooden pole structures and bare conductors

BALLOT DRAFT, MAY 2010

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KS 1877:2010

ii © KEBS 2010 — All rights reserved

TECHNICAL COMMITTEE REPRESENTATION The following organizations were represented on the Technical Committee: Nairobi City Council, City Engineer’s Department. Jomo Kenyatta University of Agriculture and Technology Kenya Polytechnic Kenya Power & Lighting Company Fluid & Power Systems Ltd Ministry of Public Works and Housing Ministry of Energy Kenafric Industries Ltd Power Technics Ltd Rural Electrification Authority The Energy Regulatory Commission Consumer Information Network Kenya Association of Manufacturers Institute of Engineers of Kenya Kenya Electricity Generating Company Ltd ABB LTD Switchgear & Controls Ltd Power Controls Ltd Communications Communication of Kenya Instrument Ltd Kenya Pipeline Company Ltd Telkom Kenya Ltd Meteorological Department Kenya Bureau of Standards — Secretariat

REVISION OF KENYA STANDARDS In order to keep abreast of progress in industry, Kenya standards shall be regularly reviewed. Suggestions for improvement to published standards, addressed to the Managing Director, Kenya Bureau of Standards, are welcome.

© Kenya Bureau of Standards, 2010 Copyright. Users are reminded that by virtue of Section 25 of the Copyright Act, Cap. 12 of 2001 of the Laws of Kenya, copyright subsists in all Kenya Standards and except as provided under Section 26 of this Act, no Kenya Standard produced by Kenya Bureau of Standards may be reproduced, stored in a retrieval system in any form or transmitted by any means without prior permission in writing from the Managing Director.

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KENYA STANDARD KS 1877:2010 ICS 29.260.20

© KEBS 2010 — All rights reserved iii

Electrical power transmission and distribution — Guidelines for the application design, planning and construction of medium voltage overhead power lines up to and including 22 kV, using wooden pole structures and bare conductors

KENYA BUREAU OF STANDARDS (KEBS)

Head Office: P.O. Box 54974, Nairobi-00200, Tel.: (+254 020) 605490, 69028000, 602350, Mobile: 0722202137/8, 0734600471/2;

Fax: (+254 020) 604031 E-Mail: [email protected], Web:http://www.kebs.org

KEBS Coast Region P.O. Box 99376, Mombasa 80100 Tel: (+254 041) 229563, 230939/40 Fax: (+254 041) 229448 E-mail: [email protected]

KEBS Lake Region P.O. Box 2949, Kisumu 40100 Tel: (+254 057) 23549,22396 Fax: (+254 057) 21814 E-mail: [email protected]

KEBS North Rift Region P.O. Box 2138, Nakuru 20100 Tel: (+254 051) 210553, 210555

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KS 1877:2010

iv © KEBS 2010 — All rights reserved

F O R E W O R D

This Kenya standard was prepared by the Switchgear and Distribution Equipment in accordance with the procedures of the Bureau and is in compliance with Annex 3 of the WTO/TB Agreement. The planning and construction of medium voltage overhead lines are regularly undertaken by electricity suppliers. These guidelines have been developed in order to facilitate the electricity distribution process, and to promote the standardization of structures and materials used. Although these guidelines are based on wooden pole structures, concrete poles may be used. However, when concrete poles are used, it is important that insulators of higher lightning impulse withstand voltage also be used, the object being to ensure that an overall basic insulation level (BIL) of 300 kV per structure is maintained. These guidelines include an example project, complete with tabulated information, standardized structure designs and explanatory comments. In the development of this standard, SANS NRS 33:1996, Electricity distribution — Guidelines for the application design, planning and construction of medium voltage overhead power lines up to and including 22 kV, using wooded pole structures and bare conductors, was extensively consulted. Assistance derived from this source is hereby acknowledged. Normative and informative annexes A 'normative' annex is an integral part of a standard, whereas an 'informative' annex is only for information and guidance. Summary of development

This Kenya Standard, having been prepared by the Switchgear and Distribution Equipment Technical Committee was first approved by the National Standards Council in June 2010

Amendments issued since publication

Amd. No. Date Text affected

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KS 1877:2010

© KEBS 2010 — All rights reserved v

Contents

1 Scope .................................................................................................................................................... 1

2 Normative references............................................................................................................................ 1

3 Definitions ............................................................................................................................................. 1

4 Application design guidelines ............................................................................................................... 3

4.1 Preferred structures, conductors and components ............................................................................... 3

4.2 Wind loading and loading levels ........................................................................................................... 4

4.3 Minimum factors of safety ..................................................................................................................... 4

4.4 Use of vibration dampers ...................................................................................................................... 5

4.5 Minimum clearances ............................................................................................................................. 5

4.6 Basic insulation level, earthing and surge protection ........................................................................... 5

4.7 Recommended crossing practice ......................................................................................................... 6

4.8 Support structure function ..................................................................................................................... 6

5 Planning guidelines ............................................................................................................................... 9

5.1 The power distribution system planning phase .................................................................................... 9

5.2 The pre-construction planning phase ................................................................................................... 9

6 Construction guidelines....................................................................................................................... 11

6.1 Delivery and handling ......................................................................................................................... 11

6.2 Assembly and dressing ....................................................................................................................... 12

6.3 Excavation .......................................................................................................................................... 12

6.4 Erection, backfilling, and stay installation ........................................................................................... 13

6.5 Conductor erection .............................................................................................................................. 14

6.6 Transformer and switchgear erection ................................................................................................. 16

6.7 Route reinstatement and clearing ....................................................................................................... 16

6.8 Labelling of structures ......................................................................................................................... 16

6.9 Inspection ............................................................................................................................................ 17

Annex A (normative) Design of power line crossings of proclaimed roads, railway lines, tramways and important communication lines ........................................................................................................................ 18

Annex B (normative) Procedure for positioning of structures on a surveyed route plan ................................ 23

Annex C (normative) Description and illustrations of overhead power line support standards and related features ............................................................................................................................................................ 34

Annex D (informative) Project example .......................................................................................................... 62

Annex E (informative) Bibliography ................................................................................................................ 69

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KENYA STANDARD KS 1877:2010

© KEBS 2010 — All rights reserved 1

Electrical power transmission and distribution — Gu idelines for the application design, planning and construction of me dium voltage overhead power lines up to and including 22 kV, usi ng wooden pole structures and bare conductors 1 Scope These guidelines are intended for use by an experienced person for the application design and construction of medium voltage overhead power lines up to and including 22 kV, using wooden pole structures. Should higher voltage, alternative or more comprehensive designs be required, these should be carried out in accordance with KS 1859. These guidelines are not intended as a text book for the design of overhead power lines but do provide an example of overhead line design that complies with professionally accepted practices. 2 Normative references The following referenced documents are indispensable for the application of this Kenya Standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. BS 3242:1970, Specification for aluminium alloy stranded conductors for overhead power transmission IEC 60433:1980, Characteristics of string insulator units of the long rod type IEC 61089:1991, Round wire concentric lay overhead electrical stranded conductors NRS 039:1995, Guide for the application of gapless metal-oxide surge arresters in distribution systems SABS 182-3:1975, Conductors for overhead electrical transmission lines — Part 3: Aluminium conductors, steel reinforced SABS 753:1994, Pine poles, cross-arms and spacers for power distribution, telephone systems and street lighting KS 02-516:1994, Eucalyptus poles, cross-arms and spacers for power distribution and telephone systems IEC 60305: 1978, Characteristics of string insulator units of the cap and pin type IEC 60383-1:1993, Insulators for overhead lines with a nominal voltage above 1000 V — Part 1: Ceramic or glass insulator units for a. c. systems — Definitions, test methods and acceptance criteria IEC 60720:1981, Characteristics of line post insulators 3 Definitions For the purposes of these guidelines, the following definitions apply: 3.1 basic insulation level (BIL) The test voltage, under specified conditions, that the insulation of a device is designed to withstand. 3.2 completely self-protected (CSP) transformer A transformer that is designed to be self-protected against overloads, short-circuits and overheating. 3.3

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KS 1877:2010

2 © KEBS 2010 — All rights reserved

dressing of poles The attachment of hardware and accessories to poles. 3.4 experienced person A full-time employee, designated (in writing) by the employer, charged with the duty of supervising the construction of overhead lines, and who has had at least two years' experience in the type of construction to be supervised. NOTE An experienced person should be:

a) familiar with the Electric Power Act, 1997, and its implications; b) trained in the construction of overhead lines; and c) aware of the dangers associated with the construction of overhead lines.

3.5 formed tie A custom-designed wire strand, set of wire strands or plastic strand that has been factory formed to suit a particular insulator neck size, or conductor or stay wire type (or both). 3.6 ground span That horizontal distance between supporting structures, that on level ground with the conductor at maximum sag, enables the statutory clearance of the conductor above the ground to be achieved. NOTE The ground span is dependent on the structure height, the type of conductor, the temperature, and the tension limits within which the conductor is designed to operate. 3.7 lightning impulse withstand voltage The lightning impulse voltage that an insulator, under prescribed conditions of test, will withstand when the insulator is dry. 3.8 mass span Those portions of the span lengths on either side of the structure that impose a vertical load on the structure. NOTE The maximum mass span that can be supported by the structure is dependent on the strength of the structure and the strength of the supporting hardware, including insulators. The mass span is calculated using the mass per unit length of the conductor supported by the structure. 3.9 overturn span The maximum span length capability of the structure foundation under maximum wind load conditions, with the statutory foundation factor of safety (currently 2). 3.10 pole pike A device that is used to assist the manual erection of poles. The top end usually consists of an aluminium tube of diameter approximately 75 mm, with the lower end being flat with a pair of handles. NOTE For wooden pole erection, a single pike or a pair of pikes secures the pole during erection and backfill operations. 3.11 skid board Panels that have a smooth, clean upper surface that is placed between the butt of the pole and the face of the excavation, to facilitate the erection of the pole. 3.12 structure A dressed and erected single pole or multipole assembly, including cross-arms and hardware. 3.13 templating

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The activity of placing or positioning the structure on the ground profile, drawing or map. 3.14 wind span The sum of those portions of span lengths on either side of the structure that, when subjected to wind, impose a horizontal load on the structure. NOTE The maximum wind span is dependent upon the ability of the structure and its foundation to resist the overturning moment caused by the action of the wind. 4 Application design guidelines 4.1 Preferred structures, conductors and components 4.1.1 General The structures, conductor and components referred to in these guidelines are among those most commonly used. In the interests of standardization, users of these guidelines are encouraged to select the required components from these preferred items, whenever practicable. Where it is vital to use conductor sizes other than those listed in Tables B.3, B.4, B.5, B.6, B.7 and B.8 of Annex B, the conductor manufacturers should be consulted for the relevant sag/tension data. Except where allowed for in the scope of this guide, the structures included in Annex C should be used for all lines up to and including 22 kV. The insulation levels should correspond to the highest system phase-to-phase and phase-to-earth voltages. Where it is foreseen that a higher voltage level will be used in the future, it is good practice: to insulate the strain structures to at least the proposed higher voltage level, and to allow adequate ground clearance for the proposed higher voltage level. In particular, it is recommended that 11 kV insulation be used for 6.6 kV lines. Single-phase two-wire lines should use the three-phase structures, minus the bottom insulator on staggered vertical configuration structures, and minus the centre insulator on horizontal and delta configuration structures. 4.1.2 Recommended insulator characteristics Insulators should comply with the relevant of the following standards: a) IEC 60433 for long rod insulators; b) IEC 305 for disc (cap and pin) insulators; c) IEC 60383-1 for ceramic or glass insulators; and d) IEC 60720 for line post insulators. The essential mechanical and electrical characteristics of insulators are given in Tables 1, 2 and 3. NOTE Where adverse environmental conditions exist, the use of composite insulators that comply with IEC 61109 should be considered.

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Table 1 — Mechanical characteristics of insulators

1 2 3 4

Insulator type and application Pin or pos t, intermediate

Pin or post road crossing, small deviation

Long rod or disc, intermediate

Long rod or disc, strain

Minimum mechanical falling load (see 4.1.2) kN

4 (cantilever

10 (cantilever

40 (tensile)

401)

(tensile) * or to suit conductor tension.

Table 2 — Electrical characteristics of insulators

Values in kilovolts 1 2 3

Nominal r.m.s. system voltage

Rated peak lightning impulse withstand

voltage

Rated wet power frequency r.m.s.

withstand voltage

11 95 28 22 150 min. 50

The standard atmospheric pollution level should be taken as medium, and the minimum specific creepage distance between phase and earth should be 20 mm per kilovolt of the highest system phase-to-phase voltage, Um. Where other conditions prevail, the creepage distance should be as specified in table 3.

Table 3 — Creepage distances between phase and eart h

1 2 Pollution level Minimum specific creepage

distance between phase and earth

mm per kV of Um

Light 16 Medium 20 Heavy 25

Very heavy 31 4.2 Wind loading and loading levels Structures, conductors and components described in these guidelines have been designed to withstand the loads imposed when they are subjected simultaneously to a wind pressure of 700 Pa and an ambient temperature of -5 °C. These figures should be used unless a Professional Engineer has access to local data that indicate designs not covered by this guideline. 4.3 Minimum factors of safety The minimum factors of safety that should be used are:

Wooden poles not continuously loaded:

2.7 based on ultimate fibre stress (bending loads)

Wooden poles and cross-arms continuously loaded:

4.5 based on ultimate fibre stress (bending loads) and modules of elasticity (axial loads)

Conductors, insulators and conductor fittings:

2.5 based on type-tested breaking strength

Stay assemblies:

2.5 based on type-tested breaking strength

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4.4 Use of vibration dampers As a general rule, in the case of spans of less than 150 m, vibration dampers will not normally be necessary, provided that at 15 °C, the conductor tension does not exceed 15 % of the ultimate tensile strength (UTS). However, in the case of spans that cross mountainous country, wide valleys or wide rivers, the use of vibration dampers should be considered. 4.5 Minimum clearances The minimum clearances for the range of voltages covered by these guidelines are shown in Table 4.

Table 4 — Minimum clearances for bare conductors

1 2 3 4 5 6 7 Maximum

rm.s. phase-to-phase

voltage for which

insulation is designed

Minimum safety

clearance

Above ground outside

townships

Above ground in

townships

Above roads in

townships, proclaimed

roads outside

townships, railways

and tramways

To communication lines,

other power

lines or between power

lines and cradles

To buildings, poles and structures

not forming part of power lines

kV m m m m m m 1.1 or less - 4.9 5.5 6.1 0.6 3.0

7.2 0.15 5.0 5.5 6.2 0.7 3.0 12 0.20 5.1 5.5 6.3 0.8 3.0 24 0.32 5.2 5.5 6.4 0.9 3.0 36 0.43 5.3 5.5 6.5 1.0 3.0 48 0.54 5.4 5.5 6.6 1.1 3.0 72 0.77 5.7 5.7 6.9 1.4 3.2

100 1.00 5.9 5.9 7.1 1.6 3.4 145 1.45 6.3 6.3 7.5 2.0 3.8 245 1.85 6.7 6.7 7.9 2.4 4.2 300 2.35 7.2 7.2 8.4 2.9 4.7 362 2.90 7.8 7.8 9.0 3.5 5.3 420 3.20 8.1 8.1 9.3 3.8 5.6 800 5.50 10.4 10.4 11.6 6.1 8.5

NOTE The minimum safety clearance is equal to the minimum safe approach clearance.

4.6 Basic insulation level, earthing and surge prot ection 4.6.1 The designs in these guidelines are based on a 300 kV lightning impulse withstand voltage of a wooden pole structure, except for a structure fitted with equipment protected by surge arresters (see 4.6.4). The insulation level of 300 kV was chosen to obtain the optimum balance between reliability, system performance and damage to wooden poles in areas of medium to high lightning activity (> 4 flashes/km2/year). 4.6.2 Where earth wires are required on a structure, these are shown in the relevant figures in Annex C. 4.6.3 Where an earth wire is used on a pole to maintain a BIL of 300 kV at a structure, it is important that it be terminated 500 mm below: a) the hardware that is attached to the mounting point of the lowest insulator in the case of unbonded

structures, b) the lowest bonded hardware in the case of bonded structures, c) stay attachment points, and d) equipment not protected by surge arresters, such as line links.

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The top of the earth wire should be secured to the pole with a band of metal or similar durable material around the pole, so that a measure of electrical stress relief is provided.

4.6.4 Surge arresters should be provided to protect equipment and structures which have a BIL of less than 300 kV and they should be selected and installed in accordance with NRS 039. In areas subject to marine or high industrial pollution, the insulator mounting hardware and other metal work should be bonded to prevent pole-top fires. 4.6.5 All stays should have stay insulators. The stay insulators should be fitted approximately 1500 mm from the stay attachment point on the pole. 4.6.6 In order to maintain a BIL of 300 kV on all stayed structures, especially those where stays are attached to steel cross-arms or insulator anchor points, fibreglass rod stay insulators have been used in the designs throughout these guidelines. These insulators should have an ultraviolet resistant fibreglass rod that has a BIL of approximately 300 kV and an ultimate breaking strength (UBS) that exceeds that of the stay wires used, i.e. the UBS of the insulators should be 70 kN for a 7/3.35, 1100 MPa stay wire and 100 kN for a 7/4.0, 1100 MPa stay wire. NOTE Higher values of UBS have been specified for the stay insulators than for the stay wires, so that the stay wires act as a mechanical weak link if an abnormal strain is applied. 4.6.7 On structures where the 300 kV BIL cannot be maintained, a single conventional porcelain stay insulator should be used in each stay assembly. An example of such a structure is one located in a coastal area, where the metal hardware is bonded, and where surge arresters are installed or earthed equipment is located. Conventional porcelain stay insulators can also be used where it is particularly important that the mechanical integrity of a stay assembly be retained.

NOTE See NRS 022 for the mechanical and electrical requirements of stay assembly components.

4.7 Recommended crossing practice The design of power line crossings of proclaimed roads, railway lines, tramways and important communication lines is covered in Annex A. 4.8 Support structure function The recommended structure designs are given in annex C. Wooden poles and cross-arms should conform to the requirements of KS 02-516. The type of configuration (horizontal, delta or vertical) and the type of structure (intermediate, suspension or strain) for the structures that have pole-mounted equipment is only typical. The line design engineer or experienced person should choose the required configuration and the type of structure depending on the local circumstances, for example the availability of pole sizes and the positioning of pole-mounted equipment. The functions of the typical structures are as given in 4.8.1 to 4.8.27. 4.8.1 Intermediate wooden pole structure, vertical, no deviation (see Figure C.1) This intermediate structure should be used where the line extends in a straight line, and where the conductors are continuous. The span data of these structures are obtainable from Tables B.1 and B.2 of Annex B. 4.8.2 Intermediate wooden pole structure, vertical, small angle deviation (see Figure C.2) This intermediate structure should be used where the line deviates by a small angle. This angle is dependent on the type of conductor used, since different types of conductor will impose different loads on the structure. 4.8.3 Road crossing intermediate wooden pole struct ure, vertical, no deviation (see Figure C.3) This intermediate structure should be used where the line crosses a road without the line's changing direction. 4.8.4 Suspension wooden pole structure, vertical, m edium angle deviation (see Figure C.4)

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This structure should be used for line deviations where the structure shown in Figure C.2 cannot accommodate the extent of the angle. The reason for the minimum deviation is that the insulators need to be kept away from the pole. If the deviation angle is too small, the conductors could be too close to the pole to satisfy the insulation requirements. The maximum angles are determined by the loads applied to the structure by the conductors. 4.8.5 Strain wooden pole structure, vertical, 30 0 to 900 deviation (see Figure C.5) This structure should be used where the angle of deviation is too great for any of the preceding structures. The conductors from each span are separately terminated and strained-off, and interconnecting jumpers are fitted as shown in the diagram. 4.8.6 Strain wooden pole structure, delta, up to 30 0 deviation (see figure C.6) This structure should be used for all strain positions where the line deviation does not exceed 300. These structures should also be used on all rail crossings. 4.8.7 H-pole strain wooden pole structure, horizont al, 600 to 900 deviation (see figure C.7) This structure should be used where a line that uses HARE or OAK conductors (see table B.1 and table B.2), is required to be angled in the range 600 to 900. 4.8.8 Long span H-pole suspension wooden pole struc ture, delta, no deviation (see figure C.8) This structure should be used on spans from 180 m up to 470 m, for conductors in a delta formation, with no deviation. 4.8.9 Long span H-pole strain wooden pole structure , delta, no deviation (see figure C.9) This structure should be used on spans from 180 m up to 470 m. It is designed to prevent the conductors from touching and causing interruptions in the supply. 4.8.10 Long span triple-pole strain wooden pole str ucture, delta, no deviation (see figure C.10) This structure illustrates the use of a triple-pole strain structure, which can be used to support long spans of conductor in a delta formation, with no deviation, up to a span of 700 m. 4.8.11 Terminal wooden pole structure, vertical (seefigureC.11) The structure illustrates the termination of conductors in a vertical configuration. 4.8.12 Terminal wooden pole structure, delta (see figure C.12) This structure illustrates the termination of conductors in a delta configuration. 4.8.13 Tee-off wooden pole structure, vertical inte rmediate to vertical tee-off, no deviation (see figure C.13) This structure should be used where it is necessary to provide a vertical tee-off from an existing intermediate vertical structure where an isolating point is not required for maintenance or for operational purposes. 4.8.14 Tee-off wooden pole structure, vertical inte rmediate to delta tee-off, no deviation (see figure C.14) This structure should be used where it is necessary to provide a delta tee-off from an existing intermediate vertical structure where an isolating point is not required for maintenance or for operational purposes. 4.8.15 Recloser or sectionalizer strain wooden pole structure, horizontal, deviation (see figure C.15) This structure should be used to support a recloser or sectionalizer. The structure has bypass facilities, so that the supply can be maintained whilst the recloser or sectionalizer is out of service. 4.8.16 In-line isolating strain wooden pole structu re, delta, no deviation (see figure C.16)

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This structure should be used when it is necessary to break the line for maintenance or for operational purposes. A "switch" or link is then placed in the line to provide an isolating point. 4.8.17 Pole-mounted CSP transformer, mass < 760 kg, terminal wooden pole structure, delta (see figure C.17) This structure should be used for the support and connection of the CSP type of transformer that contains internal fuses. If this structure is used to support non-CSP transformers, the transformers should be individually protected. The maximum transformer mass that may be used on this structure is 760 kg. 4.8.18 Pole-mounted transformer, mass <760 kg, inte rmediate wooden pole structure, vertical, no deviation (see figure C.18) This structure is the same as illustrated in figure C.17, but is for use in the in-line position. The maximum transformer mass that may be used on this structure is 760 kg. 4.8.19 Platform-mounted transformer, 760 kg < mass < 2000 kg, terminal wooden pole structure, horizontal (see figure C.19) This structure should be used to support a transformer of mass exceeding 760 kg but not exceeding 2000 kg. The structure can either be a terminal structure or an in-line strain structure. 4.8.20 Platform-mounted transformer, 760 kg < mass < 2000 kg, intermediate wooden pole structure, vertical (see figure C.20) This structure should be used to support a transformer and associated equipment of mass exceeding 760 kg but not exceeding 2000 kg, where the line is in the vertical configuration. 4.8.21 Delta to vertical phase configuration interm ediate wooden pole structures (see figure C.21) These structures illustrate the correct phase configuration arrangement of phase conductors where a change is required from a delta configuration to a vertical configuration. 4.8.22 Pole foundation detail (see figure C.22) The overturning moment of the structures has been designed in accordance with these diagrams. The steel base plate or precast concrete slab, where indicated, is necessary to prevent the pole from punching into the soil, and should be used on all stayed and transformer structures. 4.8.23 Stay anchor assembly installation detail (see figure C.23) The stay loadings are designed in strict accordance with this installation diagram. It is imperative that this drawing be adhered to. 4.8.24 Rock anchor assembly installation detail (see figure C.24) This illustrates the application of a double-eyed stay rod and a rock anchor for anchoring a stay wire assembly. 4.8.25 Stay assembly detail (see figure C.25) This stay assembly should be used with the appropriate stay wire of the stay loading tables B.9 and B.10. Stay insulators should be used on all stays. 4.8.26 Overhead (flying) stay arrangement detail (see figure C.26) This illustrates the arrangement of an overhead stay which is used where clearance above a road is required. 4.8.27 Conductor tie installation for pin and post insulators (see figure C.27) This illustrates conductor tie installation details for pin and post insulators.

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5 Planning guidelines 5.1 The power distribution system planning phase To select the correct system operating voltage and conductor size, it is necessary to make an estimate of the load to be served, its type, and the growth in the load likely to be encountered over a period of 10 to 15 years, and to establish the expected distribution distances. A combination of conductor sizes and system operating voltages can be analysed to calculate voltage drops and power losses from which a suitable design can be formulated to comply with the voltage drop requirements and to yield the lower capitalized costs. In this way, the following can be defined: a) the nominal system operating voltage; b) the type of conductor; c) the type of construction; d) the type of system electrical protection;

NOTE The determination of the capacity of the fuses and surge arresters, and also the auto-recloser protection settings, are beyond the scope of this guideline and are deemed to have been determined.

e) requirements of any affected authorities with regard to, for example, road and rail crossings, civil

aviation and telephone cable routes, etc.; f) whether these guidelines are appropriate for the type of line under consideration; and g) whether construction will be executed "in house", or by contractors.

NOTE The "in-house" mode of construction is adopted in the example in Annex D. 5.2 The pre-construction planning phase 5.2.1 Survey 5.2.1.1 The services of a power line surveyor should be used for all lines, except for short lines along simple routes. The surveyor should be provided with the proposed line route marked out on a survey map, showing start, finish, and approximate length of the line. Terrain features, crossings, environmental factors and isolation points should also be indicated. NOTE 1 In these guidelines, a surveyor means a surveyor experienced in the survey of power lines. NOTE 2 The services of a surveyor are assumed in the power line project example described in Annex D. NOTE 3 The surveyor should also be advised of the type of structures intended to be used (see 4.8 and Annex C). 5.2.1.2 Route planning The survey usually has two purposes: a) to produce a plan showing prominent features in relation to the proposed route; and b) to place planned features on the ground so that they are in the correct position. The line route between the start and end points should be planned, taking into account physical features, existing and planned infrastructure (such as roads, railway lines and townships), natural areas and land-owner requirements. No part of the pole structure or stay assembly may be erected within the road reserve without the permission of the relevant provincial or local authority. In areas sensitive to environmental degradation, it is advisable that the services of an environmental consultant be used. 5.2.1.3 Route acquisition

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If the power line crosses properties not owned by the electricity supplier, it is necessary to negotiate an agreement of occupation or wayleave for the power line. It is advisable to use a legal document that specifies the rights of the electricity supplier, and the restrictions placed upon the land-owner by the presence of the power line. The document should specify, for example, the building restriction, access along the power line route, compensation for the rights (if any), limits of the electricity supplier and damage compensation due to construction activities. The document should also include any special conditions negotiated with the land owner. The services of an attorney or registrar of deeds should be secured. It is important that the contract be signed before any work is carried out on a property. 5.2.1.4 Approval from holders of other rights If the power line crosses other services such as telecommunication lines, roads, railway lines, water pipes or any servitudes and mining rights, it is necessary to obtain approval for such a crossing from the holders of these rights. The approval will specify under what conditions the particular service may be crossed, what supervision will be required during construction activities, and how payment, if any, will be effected. Whenever practicable, joint planning with the providers of other services and other relevant authorities is recommended. 5.2.1.5 Route survey In any route survey, two processes are required. First of all, the bend points are placed in the positions as planned in 5.2.1.2. The surveyor ensures that no encroachments, other than those approved under 5.2.1.3 or agreed to by the land owner, occur. Secondly, measurements are then taken along the line between bend points, and the chainage position of topographical features (roads, railway lines, structures, cultivation, streams, high ground, etc.) is recorded. The angles at the bends are also measured. If the ground is undulating, or if there are steep slopes, it is necessary to take vertical measurements so that a ground profile can be produced. As a general rule, it is advisable to produce a ground profile or cross-section for slopes that exceed 50. The ground profile or cross-section will be required to ensure that specified conductor-to-ground clearances are achieved at the optimal structure spacings. This process is called templating, and requires the specialized knowledge of a competent person. It is now possible to determine the support structure positions, taking into account the topographical features, specified distances from other services and structures, land-owner requirements and span lengths. The type of structures (angle and support) can also be determined. This process can be done by the surveyor in the field, provided that he has been supplied with all the relevant information. The surveyor is now in a position to produce a spanning plan, showing all the topographical features, structure positions and structure types, including those for transformers and isolators (see annex B). This plan is then checked and approved by the experienced person who has been appointed as the construction supervisor (see 5.2.4), for use during the construction process. The next step is to peg all the support structure positions on the ground. At the same time, any stay positions are also pegged. 5.2.2 Span length and structure positioning A procedure to select appropriate span lengths and to determine suitable positions for the location 0 the structures is given in annex B. The ground profile is provided by the power line surveyor. After the type of structures and their positions have been selected, a structure schedule can be compiled (see the examples in tables D.1 and D.2 of annex D). 5.2.3 Bill of materials The bill of materials is compiled from the structure schedules. The materials required for the construction project can be obtained by any one of the following: a) ordering individual items from recognized suppliers of such items; b) including the supply of materials in the project construction responsibilities; or c) appointing an agent familiar with the market.

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At the time of ordering, a decision regarding the delivery destination should have been made, i.e. to a peg, to a store or to a site near the project. 5.2.4 Appointment and duties of the construction su pervisor 5.2.4.1 The person responsible for the construction of the project should appoint, in writing, an experienced person as a construction supervisor. 6.2.4.2 The construction supervisors duties will include the following: a) allocation of suitably trained labour to carry out the work; b) ensuring that all safety aspects are addressed; c) inspection of the route to ascertain:

1) the type of terrain, and access to structure positions, 2) any special foundation requirements, 3) the type of ground to be excavated and equipment required, and 4) environmental aspects that could affect construction;

d) assigning of equipment and transport (such as cranes for off-loading, 4-wheel drive vehicles),

dependent on construction techniques and field conditions; e) optimum use of resources to achieve a quality product; and f) scheduling of all activities, including preparation of a programming sequence, typically using a bar chart

or an activity schedule as shown in the project example in Figure D.3 of Annex D. 5.2.4.3 Scheduling of activities When the activities for the construction phase are being scheduled, at least the following activities need to be considered: a) pegging of all pole and stay positions; b) notification to land-owners of the intended date of construction: c) programmed delivery of materials; d) assembly (see 6.2); e) excavation (see 6.3); f) structure erection (see 6.4); g) conductor erection/regulating (see 6.5); h) transformer and switchgear erection (see 6.6); i) route reinstatement (see 6.7); j) clearing up; and k) commissioning of apparatus. 6 Construction guidelines 6.1 Delivery and handling

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6.1.1 The way of laying poles upon delivery is dependent on the methods of excavation, dressing and erection. 6.1.2 Care should be exercised in the loading and off-loading of poles. Poles should not be thrown off the vehicle because this can cause hidden damage to a pole which could lead to its early failure. Cranes or off-loading ramps should be used. 6.1.3 Poles of the correct length and diameter should be delivered to each peg. 6.1.4 If holes are to be excavated manually and the poles erected manually, the pole should be laid out in line with the longitudinal axis of the excavation, with the butt ready to enter the lead into the hole (see figure C.22 of annex C). 6.1.5 If holes are to be excavated mechanically and poles erected by crane, the pole should be laid out sufficiently clear of the peg to allow for machine access but no further from the peg than necessary. 6.1.6 Insulators, stay assemblies and other components required to dress the structures should be loaded onto a separate vehicle or trailer, for delivery at the same time as the poles, provided that there is no risk of theft. 6.2 Assembly and dressing NOTE The equipment required for this activity is relatively simple, consisting of a trestle to support the pole top above ground at a sufficient height to enable drilling and dressing, an auger for drilling poles, pliers, spanners, a hacksaw and a hammer. 6.2.1 Dressing of poles should precede their erection. Any holes drilled into poles on site should be properly treated by impregnating the holes with the same type of preservative that was used for the pole (for example, creosote). The preservative should be applied under pressure. 6.2.2 When a pole is being dressed, care should be taken to ensure that the dressed structure presents a good appearance. Aspects such as the earth-wire downlead's being stapled frequently an in a straight vertical line, holes being drilled perpendicularly to the pole axis where required an insulator alignment and separation should be carried out with care. 6.2.3 The stay assembly should be assembled in accordance with figure C.25 of annex C. Stay wire lengths are determined on site. Allowance for sloping ground is made on site, but wastage should b avoided. Where stay wires cannot be made off immediately, the stay wires should be tied to the pole at a position above normal reach, to prevent injury to persons and livestock. 6.2.4 Road-crossing intermediate structures should be dressed with 10 kN post insulators. All other intermediate structures should be dressed with 4 kN post insulators. Strain structures should b dressed with 40 kN strain insulators. NOTE The provision of anti-climbing guards is not normally considered necessary for the structures described in these guidelines. However, where there is the possibility of a structure being climbed unaided, the provision of anti-climbing devices is a statutory requirement. 6.3 Excavation 6.3.1 Excavation should preferably be carried out after the dressed structures are in position and ready for erection, since excavations present a hazard to persons and livestock. 6.3.2 The holes for the poles and stays should be excavated in accordance with figures C.22 and C.23 of annex C. 6.3.3 Cognizance should be taken of regulation 13 of the General Safety Regulations of the OHS Act, 1993, in respect of the depth of excavation in which a man may work without shoring. The step method of excavation shown in figure C.22 of Annex C complies with the OHS Act, 1993. 6.3.4 If for some reason the excavation is to be left open and exposed for a period of time, it should be adequately barricaded to prevent injury to persons and livestock.

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6.3.5 It is essential that the excavated soil be separated into top soil and other soil, in order to allow for the reinstatement of the excavation with the top soil in place at ground level. 6.4 Erection, backfilling, and stay installation CAUTION ! Unless excavations are barricaded, this a ctivity should take place immediately after

the excavation activity. 6.4.1 Mechanical erection Erection by crane requires the observance of all safety aspects relating to equipment ratings, equipment stability, and the positioning of workmen. 6.4.2 Manual erection The equipment needed for the manual erection of poles includes pole pikes (see figure 1), or ladders with reinforced top rungs, or similarly adapted equipment with a special attachment to engage and support the pole during the raising operation. CAUTION ! Under no circumstances should a normal la dder be subjected to the loads imposed

by the lifting of poles. The supervisor should ensure that no support will be released until the load has been taken by another pike or reinforced ladder. Stayed poles should be so erected that, upon completion of the backfill operation, the pole leans away from the stay position by at least half a pole diameter at the top. This will ensure correct alignment when the stay is made off correctly. 6.4.3 Backfilling of excavations for poles and stay s An extremely important part of structure erection is the backfilling, and it is essential that this be carried out properly. The backfill material should be introduced into the excavation in small quantities and thoroughly tamped or rammed to ensure maximum compaction and maximum bearing pressure. A layer of backfill of depth not exceeding 200 mm at a time should be rammed as solidly as possible before the next layer is added. To achieve this objective, typically there should be twice as many workmen ramming as shovelling. Where the backfill material is such that it will not consolidate (i.e. is non-cohesive), it is necessary to add cement in the ratio of 1 unit of cement to 8 units of soil (a unit could be a shovel full). The soil and cement should be thoroughly mixed before they are returned to the excavation as backfill. It is preferable that the soil/cement mix be slightly moistened by the addition of a little water to the mixture. Do not add too much water because the mix will be weakened and will not consolidate when rammed. The moistened mix should be returned to the excavation in small quantities and thoroughly rammed. 6.4.4 Stay installation The stay should be installed in accordance with figure C.23 of annex C, and carefully backfired. When the stay is installed, the stay wire should be made off in accordance with figure C.25 of annex C. Stayed poles should be so erected that they lean away from the stay (see 6.4.2). When the stay wire is tensioned using the correct tensioning equipment such as a pull-lift and come-along clamps, the stay is tensioned until the pole leans towards the stay by at least half a pole diameter at the top. Experience will indicate the exact amount of lean required. No off-cuts of stay wire should be left on site, since these are dangerous to livestock.

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All dimensions in millimetres

Figure 1 — Pole pike 6.5 Conductor erection There are three basic activities involved in conductor erection. These are: a) delivery of conductors; b) running out and stringing of conductors; and c) tensioning and regulating of conductors. 6.5.1 Delivery of conductors

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As considerable activity occurs around a drum site, care should be taken in the selection of the site position, to prevent unnecessary damage to valuable land. The area to which conductors are delivered is most important in the case of longer lines. In the case of short lines, delivery may be combined with the running out of the conductor 6.5.2 Running out of conductors CAUTION ! Care should be exercised to prevent condu ctor damage during the running out operation. 6.5.2.1 Continuous stringing of conductors is preferable, but where crossings are necessary, stringing will not be continuous. Road crossings can be included in the normal stringing, since scaffolding can be in place and the local traffic authority can be represented at the time of crossing. Rail crossings will probably be carried out as a separate activity, in order to satisfy Spoornet requirements. Valley crossings will involve manually run-out conductors, and will also be separate activities. The structures in both rail and valley crossings will support terminal loading if correctly installed. 6.5.2.2 Where road vehicles cannot travel along the full extent of the line route, the conductor will have to be pulled through by other means, such as a tractor or manpower. 6.5.2.3 To prevent unnecessary land damage, all conductors should be run out together. 6.5.2.4 In the case of road crossings, all goalpost scaffolding should be correctly installed beforehand. 6.5.2.5 All fences should be guarded or protected in order to prevent conductor or fence damage. 6.5.2.6 Specialized equipment is available for conductor stringing, but it is not needed on short lines. 6.5.2.7 It is preferable to use commercially available insulator mounted rollers. 6.5.2.8 Structures that have line deviations and continuous conductors should be equipped with stringing blocks of the correct rating. 6.5.2.9 Ensure that: a) all necessary stays, including temporary stays, are correctly installed; b) all conductor rollers or blocks are on site and are running free; c) the necessary pull-lifts, come-along clamps (at least six of each) and slings are on site and have been

examined for safe working condition; and d) vehicle access has been arranged. 6.5.2.10 The preferred method of conductor run-out is achieved by mounting the drum on a vehicle. This prevents damage to the conductor, caused by dragging it along the ground. 6.5.2.11 The end of the conductor is fastened or made off on the strain or terminal structure at the start of the line. 6.5.2.12 A braking system should be used to prevent the drums from over-running. This system can involve a strong wooden plank applied manually to the rim of the drum, to control the running speed of the drum. 6.5.2.13 The conductor should be pulled off from the top of the drum. The arrows on the drum indicate the rolling direction. When the drum is mounted on a truck or trailer, the vehicle travels until approximately 20 m beyond the first structure. After the conductor has been made off on this structure, the vehicle then reverses to allow conductor slack to be pulled back towards the pole. The conductors are placed on conductor rollers and attached to the pole top or to the insulators. 6.5.2.14 When the drum cannot be mounted on a vehicle and if no suitable drum jacks or cradles are available, it is acceptable to dig drum pits for mounting the drums. A drum pit is an excavation of sufficient

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size to allow a drum to rotate on a spindle that is at ground level. In this method, holes are excavated to suit the size of the drum. Solid planks are placed on the sides of the excavation to support a spindle through the drum. Additional pieces of timber are nailed onto the planks on each side of the spindle, to prevent the spindle from sliding along the planks. The same method of drum braking as with vehicle mounted drums is used. 6.5.2.15 Extreme care should be taken to protect the conductor from rocky ground and other objects that could scrape, or otherwise damage, the conductor surface. This protection can be achieved by the use of timber slats that are lain on the ground over which the conductor is to be pulled. 6.5.2.16 When the tensioning position is reached, the conductor can be placed in stringing blocks of correct rating, ready for sagging or tensioning. 6.5.2.17 When the conductor reaches the point where it is to be tensioned or made off, it should be pulled well clear of the ground and temporarily made off into a come-along. If any crossings are involved in the section, it is essential that a back-up come-along also be installed as a precaution against the conductor's slipping and dropping onto the service or road being crossed. 6.5.3 Regulating/tensioning Before attempting any regulating or tensioning, first ensure that the tension structures are correctly stayed against the tension. Where necessary, temporary stays will already have been installed. The conductor temperature should then be taken by means of a thermometer inserted into the end of a length of conductor from which the centre strand has been removed to allow the insertion of the thermometer. The conductor supplier will provide sag or tension tables to suit the particular line, provided that they are in possession of the structure schedule. If this is not the case, advice should be sought from a qualified person. The conductor should be regulated to the relevant tables, using a dynamometer. When the conductor is correctly regulated, the termination fittings (thimble clevis and formed tie dead-ends) can be made off. 6.5.4 Tying of conductor 6.5.4.1 When the conductors have been regulated, it is necessary to attach them firmly to the insulators by means of formed conductor ties (see figure C.3 and figure C.13 of annex C). The conductor should be marked at the centre of the stringing block, and transferred and correctly positioned to the attachment point. 6.5.4.2 Care should be taken to install ties in accordance with the manufacturer's instructions. 6.5.4.3 The crossing span over a road or over other services should be protected by the use of road crossing twin ties for vertically mounted pin or post insulators, and arcing horns for horizontally mounted strain insulators. 6.5.4.4 All temporary stays should be removed during the tying of conductors. 6.6 Transformer and switchgear erection To avoid possible damage to equipment by falling objects, in particular damage to bushings, the erection of transformers and switchgear should only commence after all overhead work has been completed. The transformers and switchgear should be erected strictly in accordance with drawings and other relevant standards. 6.7 Route reinstatement and clearing Route reinstatement and clearing are important activities, and should be treated as such. The route should be environmentally intact when these activities have been completed. All vehicle tracks and damaged fences, culverts and pipes should be repaired, and no refuse or waste left on site. If any trees have been felled or lopped, the timber should be stacked neatly, or removed in accordance with the land-owner’s instructions. 6.8 Labelling of structures

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Each individual structure should be uniquely identified. All labels should be permanent and indelible, and of a size that can be read at ground level. Danger labels are not mandatory, but these should be fitted on structures where equipment is mounted below the MV conductors. 6.9 Inspection Prior to being commissioned, the line should be thoroughly inspected, to ensure that: a) all structures have been correctly erected; b) all clearances are correct; c) all insulators have been correctly installed; d) conductors are undamaged; e) stays have been correctly installed; f) pole and anti-climbing guards, if needed, are in place; and g) pole and equipment earths are correct.

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Annex A (normative)

Design of power line crossings of proclaimed roads, railway lines, tramways and

important communication lines A.1 Scope This annex covers overhead power line crossings of proclaimed roads, railway lines, tramways and important communication lines, and should be read in conjunction with the regulations mentioned below. A.2 Regulations and figures A.2.1 Regulations The following regulations are applicable: Regulations 14, 15, 16, 17, 18, 20 and 22 of the Electrical Machinery Regulations of the Occupational Health and Safety Act, 1993 (Act 85 of 1993). A.2.2 Figures The following figures show the most common crossing configurations: a) Figure A.1 — Formed armoured road crossing twin tie for vertically mounted pin or post insulator b) Figure A.2 — Formed arcing horn for horizontally mounted long rod insulator c) Figure A.3 — Formed arcing horn for horizontally mounted disc insulator d) Figure A.4 — Crossing with strain structures on both sides e) Figure A.5 — Crossing with an intermediate structure on one side and a strain structure on the other

side f) Figure A.6 — Crossing with intermediate structures on both sides A.3 Purpose Should configurations other than those indicated in A.2.2 be used, it should be borne in mind that the main purpose of applying the above-mentioned precautions at crossings, is to ensure that flashovers to overhead line conductors and hardware adjacent to the crossing will not jeopardize the integrity of the crossing span. The crossing span conductors should not be lower than 4.5 m above ground in the case of a broken phase conductor in a span other than the crossing span as stipulated in the Occupational Health and Safety Act, 1993. These precautionary requirements, and the regulations detailed in A.2.1, should be taken into account in the design of every crossing.

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A.4 Arcing horns

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A.4.1 Formed arcing horns, as shown in figures A.2 and A.3, are to be fitted to strain insulators in a crossing span where the conductor is terminated with a formed dead-end on a thimble clevis fitting. The reason for fitting arcing horns at such terminations is that, should a flashover occur, it is very likely that there will be arcing to the thimble groove, causing damage to one or more strands of the formed tie. Damage of this nature could result in the immediate burn down of the crossing span conductor, or could give rise to a potentially dangerous situation because of the weakened formed tie (see A.5.4, alternative 2). A.4.2 Alternatively, bolted or compression type dead-ends can be used without the fitting of arcing horns, because a flashover with these fittings will result in arcing to the body of the clamp, with little or no damage to the conductor (see A.5.4, alternative 1). A.5 Structures A.5.1 Where there are strain structures on either side of the crossing, intermediate structures without any special precautions can be erected beyond the crossing (see A.5.4). A.5.2 Where there is one strain structure at the crossing, special precautions should be taken on the first three intermediate structures on the opposite side of the crossing (see A.5.5). A.5.3 Where there are no strain structures at the crossing, special precautions should be taken on the first three intermediate structures on both sides of the crossing (see A.5.6).

Figure A.4 — Crossing with strain structures on bot h sides.

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A.5.4 Requirements for strain structures marked B i n figures A.4 and A.5 Alternative 1: With bolted type conductor strain clamps or compression dead-end fittings: a) single conductor per phase: b) single strain insulator string or long rod per phase; and c) no arcing horns. or Alternative 2: With formed conductor dead-ends on thimble clevis fitting: a) single conductor per phase; b) single strain insulator string or long rod per phase; and c) fit arcing horns to live end of insulators. A.5.5 Requirements for intermediate structures mark ed C in figures A.4, A.5 and A.6

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Alternative 1: With rigid post or pin insulators: a) use 4 kN (minimum) insulators; and b) use standard formed twin tie. or Alternative 2: With suspension insulators, fit either armour rods or arcing horns to live end of insulator. A.5.6 Requirements for intermediate structures mark ed A in figures A.5 and A.6 Alternative 1: With rigid post or pin insulators: a) use 10 kN (minimum) insulators; and b) use special formed road crossing twin tie as per figure A.1. or Alternative 2: With suspension insulators, fit either armour rods or arcing horns to live end of insulators.

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Annex B (normative)

Procedure for positioning of structures on a survey ed route plan

B.1 A "spanning plan" is produced from the route plan (see 5.2.1.2). Initially, the only points indicated are the "tee-offs", "terminals" and "angles" and the approximate transformer and switchgear positions. B.2 The designer should use the following procedure to plot the structure positions on the plan. In the case of a small project, such as in the project example, it is advisable to walk the route and to take note of all obstructions. a) Select the type of structures to be used, taking account of the loading limits given in the pole span data

tables (tables B.1 and B.2), and the stay loading data tables (tables B.9 and B.10). b) Select the primary fixed points, such as a tee-off point, angle position, road, rail or other crossing,

transformer position, terminal position and valley crossing. c) Divide the distances between the fixed points by the span capability of the structure selected, using the

following tables, which give the appropriate data:

TableB.1 specifies wooden pole span data for preferred ACSR conductor sizes. TableB.2 specifies wooden pole span data for preferred AAAC conductor sizes. Table B.3 specifies conductor sag and tension for FOX conductor. Table B.4 specifies conductor sag and tension for MINK conductor. Table B. 5 specifies conductor sag and tension for HARE conductor. Table B.6 specifies conductor sag and tension for FIR conductor. Table B.7 specifies conductor sag and tension for PINE conductor. Table B.8 specifies conductor sag and tension for OAK conductor. Table B.9 provides data for pole loading with stays at 450. Table B.10 provides data for pole loading with stays at 300.

d) So adjust the positions selected in clause B.3 that comparable span lengths result, and take cognizance

of ground level variances and conductor-to-ground clearances (see 5.2.1.5). e) Peg according to the selection, and adjust the positions to obtain the best foundation and access

options. f) Each time a reselection or change is necessary, redivide the remaining lengths and pinpoint structure

positions again.

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Table B.1 — Wooden pole span data for preferred siz es of hard-drawn aluminium steelreinforced (ACSR) conductors

1 2 3 4 5 6 7 8 9

Wooden pole

length

Pole top

diam.

Planting

depth

Lowest conductor attachmen

t

Available

for sag

Conductor

code name

Wind span

Over-

turn span

Ground level

clearance

span at 50 OC

m mm m m m m m m 9 140 1.5 6.15 0.65 FOX 132 94 50 9 140 1.5 6.15 0.65 MINK 100 71 50 9 140 1.5 6.15 0.65 HARE 78 55 50

10 140 1.5 7.15 1.65 FOX 120 79 110 10 140 1.5 7.15 1.65 MINK 92 61 110 10 140 1.5 7.15 1.65 HARE 71 47 110 10 140 1.6 7.05 1.55 FOX 121 95 100 10 140 1.6 7.05 1.55 MINK 92 73 100 10 140 1.6 7.05 1.55 HARE 72 56 100 11 140 1.8 7.85 2.35 FOX 113 114 150 11 140 1.8 7.85 2.35 MINK 86 87 150 11 140 1.8 7.85 2.35 HARE 67 67 150 11 160 1.8 7.85 2.35 FOX 161 125 150 11 160 1.8 7.85 2.35 MINK 123 95 150 11 160 1.8 7.85 2.35 HARE 95 74 150 11 160 2.0 7.65 2.15 FOX 164 165 135 11 160 2.0 7.65 2.15 MINK 125 125 135 11 160 2.0 7.65 2.15 HARE 97 97 135

NOTE 1 The selected span length is determined by the limiting factors and is the least of the spans given in columns 7, 8 and 9. NOTE 2 The conductor code names FOX, MINK and HARE are the code names for the preferred sizes of hard-drawn aluminium steel-reinforced overhead conductors specified in SABS 182-3:1975.

The data in the table has been calculated on the basis of the following assumptions:

span capabilities on single wooden poles of minimum fibre strength of 55 MPa;

configuration: staggered vertical with phase spacing of 600 mm;

centre of gravity of wind load on three conductors is 750 mm from pole top;

overturn span calculated from soil bearing pressure of 345 kPa;

ground clearance span based on a minimum clearance of 5.5 m at 50 0C; and

wind pressure taken as 700 Pa.

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Table B.2 — Wooden pole span data for preferred siz es of all aluminium alloy (AAAC) conductors sizes

1 2 3 4 5 6 7 9

Wooden pole

length

Pole top

diam

Planting

depth

Lowest conducto

r attachme

nt

Available

for sag

Conductor

code name

Wind span

Over-

turn span

Ground level

clearance

span at 50 0C

m mm m m m m m m 9 140 5 6.15 0.65 FIR 125 89 50 9 140 1.5 6.15 0.65 PINE 102 72 50 9 140 1.5 6.15 0.65 OAK 79 56 50 10 140 1.6 7.15 1.65 FIR 114 75 110 10 140 1.6 7.15 1.65 PINE 93 61 110 10 140 1.6 7.15 1.65 OAK 72 48 110 10 140 1.6 7.05 1.55 FIR 115 90 100 10 140 1.6 7.05 1.55 PINE 94 74 100 10 140 1.6 7.05 1.55 OAK 73 57 100 11 140 1.8 7.85 2.35 FIR 107 108 140 11 140 1.8 7.85 2.35 PINE 88 88 140 11 140 1.8 7.85 2.35 OAK 68 68 140 11 160 1.8 7.85 2.35 FIR 152 118 140 11 160 1.8 7.85 2.35 PINE 125 96 140 11 160 1.8 7.85 2.35 OAK 97 75 140 11 160 2.0 7.65 2.15 FIR 155 156 130 11 160 2.0 7.65 2.15 PINE 127 127 130 11 160 2.0 17.6: 2.15 OAK 98 99 130

NOTE 1 The selected span length is determined by the limiting factors and is the least of the spans given in columns 7, 8 and 9. NOTE 2 The conductor code names FIR, PINE and OAK are the code names for the preferred sizes of all aluminium alloy conductors specified in BS 3242. The equivalent descriptors for these conductors, using the convention used in IEC 61089, are: FIR 47,84 - A3 – 7/2,95 PINE 71,65 - A3 – 7/3,61 OAK 118,90 - A3 – 7/4,65

The data in the table has been calculated on the basis of the following assumptions:

span capabilities on single wooden poles of minimum fibre strength of 55 MPa;

configuration: staggered vertical with phase spacing of 600 mm;

centre of gravity of wind load on three conductors is 750 mm from pole top;

overturn span calculated from soil bearing pressure of 345 kPa;

ground clearance span based on a minimum clearance of 5.5 m at 50 0C; and,

wind pressure taken as 700 Pa.

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Table B.3 — Tension and sag for ACSR, code name FOX

1 2 3 4 5 6 7 18 9 10 11 12 13

Temp Equivalent span length (m)

80 100 120 Initial

tension Initial sag

Final sag

Initial tension Initial sag

Final sag


Final sag

0C kg N m m kg N m m kg N m m 0 395 3870 0,30 0,33 393 3853 0,47 0,53 391 3833 0,69 0,78 5 374 3670 0,32 0,37 373 3658 0,50 0,58 372 3644 0,72 0,85

10 354 3471 0,34 0,40 353 3465 0,53 0,64 352 3457 0,76 0,92 15 334 3275 0,36 0,45 334 3275 0,56 0,70 334 3275 0,80 1,00 20 314 3080 0,38 0,50 315 3088 0,59 0,77 316 3096 0,85 1,09 25 294 2888 0,40 0,55 296 2904 0,63 0,84 298 2922 0,90 1,19 30 275 2700 0,43 0,62 278 2726 0,67 0,93 281 2753 0,96 1,29 35 257 2516 0,46 0,69 260 2553 0,72 1,02 264 2591 1,02 1,39 40 238 2338 0,50 0,77 243 2386 0,77 1,11 248 2436 1,08 1,50 45 221 2166 0,54 0,85 227 2227 0,82 1,21 233 2289 1,15 1,61 50 204 2001 0,58 0,93 212 2076 0,88 1,30 219 2150 1,22 1,72

1 14 15 16 17 18 19 20 21 22 23 24 25

Temp Equivalent span length (m) 140 160 180

Initial tension

Initial sag

Final sag


Final sag


Final sag

0C kg N m m kg N m m kg N m m 0 389 3811 0,94 1,09 386 3787 1,24 1,45 384 3762 1,57 1,87 5 370 3628 0,99 1,17 368 3612 1.29 1,55 366 3594 1,65 2,00

10 352 3449 1,04 1,27 351 3441 1,36 1,67 350 3432 1,72 2,13 15 334 3275 1,09 1,37 334 3275 1,43 1,79 334 3275 1,81 2,26 20 317 3105 1,15 1,47 317 3114 1,50 1,91 328 3123 1,90 2,40 25 300 2940 1,22 1,59 302 2959 1,58 2,04 304 2978 1,99 2,54 30 284 2782 1,29 1,70 287 2811 1,66 2,16 289 2839 2,08 2,68 35 268 2630 1,36 1,82 272 2669 1,75 2,30 276 2707 2,19 2,82 40 253 2486 1,44 1,94 258 2535 1,84 2,43 263 2582 2,29 2,96 45 240 2350 1,52 2,06 246 2409 1,94 2,56 251 2464 2,40 3,10 50 227 2222 1,61 2,18 233 2290 2,04 2,69 240 2354 2,51 3,24

NOTE: The sag S for any actual span of length L in a strain section of equivalent span length Le is given by S = Se(L/Le)2, where Se is the sag in the equivalent span.

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Table B.4 — Tension and sag for ACSR, code name MIN K

1 2 3 4 5 6 7 18 9 10 11 12 13 Temp Equivalent span length (m)

80 100 120 Initial

tension Initial sag

Final sag


Final sag


Final sag


10 591 5801 0,35 0,42 590 5790 0,54 0,65 589 5777 0,79 0,95 15 558 5475 0,37 0,46 558 5475 0,58 0,72 558 5474 0,83 1,04 20 525 5152 0,39 0,51 527 5165 0,61 0,79 528 5179 0,88 1,13 25 493 4834 0,42 0,57 496 4862 0,65 0,87 499 4892 0,93 1,22 30 461 4522 0,45 0,64 466 4567 0,69 0,96 470 4615 0,98 1,33 35 430 4218 0,48 0,71 436 4281 0,74 1,05 443 4347 1,04 1,43 40 400 3923 0,51 0,79 408 4006 0,79 1,14 417 4092 1,11 1,54 45 371 3638 0,55 0,87 382 3743 0,84 1,24 393 3850 1,18 1,65 50 343 3367 0,60 0,96 356 3495 0,90 1,33 369 3622 1,25 1,76

1 14 15 16 17 18 19 20 21 22 23 24 25


140 160 180 Initial

tension Initial sag

Final sag


Final sag


Final sag


10 588 5763 1,07 1,31 586 5748 1,40 1,72 584 5733 1,78 2,20 15 558 5475 1,13 1,41 558 5475 1,47 1,84 558 5475 1,86 2,33 20 530 5195 1,19 1,52 531 5210 1,55 1,97 533 5226 1,95 2,47 25 502 4924 1,25 1,63 505 4956 1,63 2,09 509 4988 2,05 2,61 30 475 4664 1,32 1,75 480 4713 1,71 2,23 485 4761 2,14 2,75 35 450 4415 1,40 1,87 457 4481 1,80 2,36 463 4545 2,25 2,89 40 426 4178 1,48 1,99 434 4261 1,89 2,49 442 4340 2,35 3,04 45 403 3954 1,56 2,11 413 4054 1,99 2,62 423 4148 2,46 3,18 50 382 3743 1,65 2,23 393 3859 2,09 2,75 404 3967 2,57 3,31


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Table B.5 — Tension and sag for ACSR, code name HAR E


80 100 120 Initial

tension Initial sag

Final sag

Initial tension

Initial sag

Final sag

Initial tension

Initial sag

Final sag


10 972 9536 0,35 0,42 970 9516 0,55 0,66 968 9495 0,79 0,96 15 917 9000 0,37 0,47 917 9000 0,58 0,73 917 9000 0,84 1,05 20 863 8470 0,40 0,52 867 8492 0,62 0,80 868 8516 0,89 1,14 25 810 7949 0,42 0,58 815 7996 0,65 0,88 820 8046 0,94 1,24 30 758 7438 0,45 0,65 766 7512 0,70 0,97 774 7592 0,99 1,34 35 707 6939 0,48 0,72 718 7044 0,74 1,06 729 7155 1,05 1,45 40 658 6456 0,52 0,80 672 6594 0,79 1,15 687 6737 1,12 1,55 45 611 5990 0,56 0,88 628 6165 0,85 1,25 646 6341 1,19 1,66 50 565 5545 0,60 0,96 585 5738 0,91 1,34 557 15468 1,26 77

1 14 15 16 17 18 19 20 21 22 23 24 25


140 160 180 Initial

tension Initial sag

Final sag

Initial tension

Initial sag

Final sag

Initial tension

Initial sag

Final sag

0C kg N m m kg N m m kg N m m 0 1065 1449 0,98 1,13 1058 10379 1,29 1,51 1050 10307 1,65 1,96 5 1015 9955 1,03 1,22 1010 9907 1,35 1,62 1005 9857 1,72 2,09 10 965 9471 1,08 1,32 963 9446 1,42 1,74 960 9421 1,80 2,22 15 917 9000 1,14 1,43 917 9000 1,49 1,86 917 9000 1,88 2,36 20 862 8452 1,20 1,54 873 8568 1,56 1,99 876 8594 1,97 2,50 25 826 8099 1,27 1,65 831 8153 1,64 2,12 836 8205 2,07 2,64 30 782 7674 1,34 1,77 791 7755 1,73 2,25 799 7834 2,17 2,78 35 741 7266 1,41 1,89 752 7376 1,82 2,38 763 7482 2,27 2,92 40 701 6879 1,49 2,01 715 7017 1,91 2,51 729 7148 2,37 3,06 45 664 6514 1,58 2,13 681 6678 2,01 2,64 697 6834 2,48 3,20 50 629 170 1,66 2,24 648 6360 2,11 2,77 667 6539 2,59 3,34 NOTE: The sag S for any actual span of length L in a strain section of equivalent span length Le is given by S = Se(L/Le)2, where Se is the sag in the equivalent span.

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Table B.6 - Tension and sag for AAAC, code name FIR


80 100 120 Initial

tension Initial sag

Final sag

Initial tension

Initial sag

Final sag

Initial tension

Initial sag

Final sag


10 370 3631 0,28 0,34 369 3624 0,44 0,54 379 3715 0,64 0,78 15 342 3357 0,31 0,38 342 3357 0,48 0,60 342 3357 0,69 0,86 20 315 3087 0,33 0,43 316 3096 0,52 0,66 317 3106 0,74 0,95 25 288 2821 0,36 0,48 290 2841 0,57 0,74 292 2863 0,81 1,05 30 261 2562 0,40 0,55 265 2595 0,62 0,83 268 2631 0,88 1,16 35 236 2312 0,44 0,63 241 2360 0,68 0,93 246 2411 0,96 1,27 40 211 2074 0,50 0,71 218 2139 0,75 1,03 225 2206 1,05 1,39 45 189 1851 0,56 0,80 197 1935 0,83 1,14 206 2017 115 1,52 50 168 1648 0,62 0,90 178 1749 0,92 1,25 188 1847 1:25 1,65

1 14 15 16 17 18 19 20 21 22 23 24 25


140 160 180 Initial

tension Initial sag

Final sag

Initial tension

Initial sag

Final sag

Initial tension

Initial sag

Final sag


10 368 3605 0,87 1,07 367 3595 1,14 1,41 365 3584 1,45 1,80 15 342 3357 0,94 1,17 342 3357 1,22 1,53 342 3357 1,55 1,94 20 317 3117 1,01 1,28 319 3128 1,31 1,66 320 3140 1,66 2,09 25 294 2886 1,09 1,40 297 2910 1,41 1,80 299 2934 1,77 2,24 30 272 2667 1,18 1,53 276 2704 1,52 1,94 279 2740 1,90 2,40 35 251 2462 1,28 1,66 256 2512 1,64 2,09 261 2560 2,03 2,57 40 232 2271 1,39 1,80 238 2334 1,76 2,25 244 2394 2,17 2,74 45 214 2096 1,50 1,94 221 2172 1,89 2,40 229 2243 2,30 2,90 50 198 1938 1,62 2,08 206 2024 2,03 2,56 215 2105 2,47 3,07


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Table B.7 - Tension and sag for AAAC, code name PIN E


80 100 120 Initial

tension Initial sag

Final sag

Initial tension

Initial sag

Final sag

Initial tension

Initial sag

Final sag


10 557 5460 0,28 0,34 556 5449 0,44 0,54 554 5436 0,64 0,78 15 515 5050 0,30 0,38 515 5050 0,49 0,59 515 5050 0,69 0,86 20 473 4644 0,33 0,43 475 4658 0,52 0,66 476 4673 0,74 0,94 25 433 4246 0,36 0,48 436 4276 0,56 0,74 439 4308 0,80 1,04 30 393 3858 0,40 0,55 398 3906 0,62 0,83 404 3959 0,87 1,15 35 355 3482 0,44 0,62 362 3554 0,68 0,92 370 3628 0,95 1,27 40 320 3135 0,49 0,71 328 3221 0,75 1,03 338 3320 1,04 1,39 45 284 2789 0,55 0,80 297 2913 0,82 1,14 312 3063 1,14 1,51 50 253 2482 0,62 0,90 269 2634 0,91 1,25 283 2779 1,25 1,64

1 14 15 16 17 18 19 20 21 22 23 24 25

Temp Equivalent span length (m) 140 160 180

Initial tension

Initial sag

Final sag

Initial tension

Initial sag

Final sag

Initial tension

Initial sag

Final sag


10 553 5422 0,87 1,07 551 5407 1,14 1,40 550 5391 1,44 1,79 15 515 5050 0,93 1,17 515 5050 1,22 1,52 515 5050 1,54 1,93 20 478 4689 1,00 1,27 480 4706 1,31 1,65 481 4723 1,65 2,08 25 443 4343 1,08 1,39 446 4378 1,41 1,79 450 4413 1,76 2,23 30 409 4013 1,17 1,52 415 4068 1,51 1,93 420 4122 1,89 2,39 35 378 3704 1,27 1,65 385 3779 1,63 2,08 393 3851 2,02 2,56 40 348 3417 1,38 1,79 358 3511 1,75 2,24 367 3601 2,16 2,72 45 322 3154 1,49 1,93 333 3266 1,94 2,39 344 3372 2,31 2,89 50 297 2916 1,62 2,07 310 3044 2,02 2,55 323 3164 2,46 3,06


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Table B.8 - Tension and sag for AAAC, code name OAK


80 100 120 Initial

tension Initial sag

Final sag

Initial tension

Initial sag

Final sag

Initial tension

Initial sag

Final sag

0C kg N m m kg N m m kg N m m 0 106 10395 0,25 0,28 1055 10348 0,39 0,45 1050 10293 0,56 0,66 5 0 9701 0,26 0,31 985 9667 0,41 0,49 981 9628 0,60 0,72 10 989 9013 0,28 0,34 917 8995 0,44 0,54 915 8973 0,64 0,78 15 919 8332 0,31 0,38 849 8332 0,49 0,60 849 8332 0,69 0,86 20 849 7660 0,33 0,43 783 7683 0,52 0,66 786 7708 0,74 0,95 25 781 7000 0,36 0,48 719 7050 0,57 0,74 724 7105 0,81 1,05 30 714 6357 0,40 0,55 656 6439 0,62 0,83 665 6527 0,88 1,16 35 648 5736 0,44 0,63 597 5856 0,68 0,93 610 5981 0,96 1,27 40 585 5144 0,50 0,71 541 5306 0,75 1,03 558 5471 1,05 1,40 45 524 4591 0,56 0,80 489 4799 0,83 1,14 510 5003 1,15 1,52 50 468 4085 0,62 0,90 442 4338 0,92 1,25 467 4580 1,25 1,65 416


140 160 180 Initial

tension Initial sag

Final sag

Initial tension

Initial sag

Final sag

Initial tension

Initial sag

Final sag


10 912 8949 0,87 1,07 910 8924 1,14 1,41 907 8897 1,45 1,80 15 849 8332 0,94 1,17 849 8332 1,22 1,53 849 8332 1,55 1,94 20 789 7735 1,01 1,28 791 7763 1,31 1,66 794 7792 1,66 2,09 25 730 7162 1,09 1,40 736 7221 1,41 1,80 742 7280 1,77 2,24 30 675 6618 1,18 1,53 684 6710 1,52 1,94 693 6800 1,90 2,40 35 623 6108 1,28 1,66 635 6232 1,64 2,09 648 6353 2,03 2,57 40 574 5634 1,39 1,80 590 5791 1,76 2,25 606 5941 2,17 2,74 45 530 5200 1,50 1,94 549 5387 1,89 2,40 567 5563 2,32 2,90 50 490 4808 1,62 2,08 512 5022 2,03 2,56 532 5221 2,47 3,07


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Table B.9 — Pole loadings with stays at 45 0

1 2 3 4 5 6 7 8 9 10 11

Pole type

Length Top diam.

Planting depth

Ultimate buckling

load

Maximum deviation angles for conductor of type: deg rees FOX MINK HARE FIR PINE OAK 13.2 21.8 36.0 13.43 20.2 33.3

m mm m kN Pole loading with stays at 45 0 (kN) Gum

9 140 1,5 88 76 44 26 74 47 28 9 160 1,5 140 157 73 42 149 80 46 10 140 1,6 74 62 37 22 61 40 24 10 160 1,6 117 111 60 35 108 65 38 11 140 1,8 64 53 32 19 52 34 21 11 160 1,8 101 90 51 30 88 55 33 11 180 1,8 152 180 80 46 180 88 50 12 140 2,0 57 47 28 17 46 30 18 12 160 2,0 89 77 44 26 75 48 29 12 180 2,0 133 137 69 40 133 75 43

Pine

9 140 1,5 52 42 25 15 42 27 16 9 160 1,5 82 70 41 24 69 44 26 10 140 1,6 44 36 21 13 35 23 14 10 160 1,6 69 58 34 20 57 37 22 11 140 1,8 38 31 18 11 30 20 12 11 160 1,8 60 49 29 18 48 32 19 11 180 1,8 90 78 45 27 76 48 29 12 140 2,0 33 27 16 10 27 18 11 12 160 2,0 52 43 26 15 42 28 17 12 180 2,0 78 66 39 23 65 42 25 NOTE - Conductor tension has been taken as 40 % of ultimate tensile strength. Stay data in respect of poles in this cable Ult. load Max. load

kN kN 20 mm grade 300 W stay rod 94,2 38 24 mm grade 300 W stay rod 135 54 7/3,35 1100 MPa stay wire 67,9 27 7/4,00 1100 MPa stay wire 96,8 39 19/2,65 1100 M Pa stay wire 115 46 Anchor combination Deviation angle capability factor of safety = 2.5 Stay rod Stay wire FOX MINK HARE FIR PINE OAK One 20 mm 7/3,35 1100 M Pa 74 43 25 73 46 28 Two 20 mm 7/3,35 1100 M Pa 148 86 50 146 92 56 One 20 mm 7/4,00 1100 MPa 114 61 36 112 66 39 Two 20 mm 7/4,00 1100 MPa All 122 72 224 132 78 One 24 mm 19/2,65 1100 M Pa All 77 44 All 84 48 Two 24 mm , 19/2,65 1100 MPa All 154 88 All 168 96 NOTE - 'All" signifies angles of deviation up to 1800. Terminal stays Stay rod Stay wire FOX MINK HARE FIR PINE OAK One 20 mm 7/3,35 1100 M Pa Yes No No Yes No No Two 20 mm 7/3,35 1100 MPa Yes Yes Yes Yes Yes Yes One 20 mm 7/4,00 1100 MPa Yes Yes No Yes Yes No Two 20 mm 7/4,00 1100 MPa Yes Yes Yes Yes Yes Yes One 24 mm 19/2,65 1100 MPa Yes Yes No Yes Yes No TWO 24 mm 19/2,65 1100 MPa Yes Yes Yes Yes Yes Yes

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Table E3.10 — Pole loadings with stays at 30 0

1 2 3 4 5 6 7 8 9 10 11 Pole type

Length Top diam.

Planting depth

Ultimate buckling

load

Maximum deviation angles for conductor of type: deg rees FOX MINK HARE FIR PINE OAK 13.2 21.8 36.0 13.43 20.2 33.3

m mm m kN Pole loading with stays at 45 0 (kN) Gum

9 140 1,5 88 5 15 41 27 16 9 160 1,5 140 69 40 24 68 43 26 10 140 1,6 74 35 21 13 34 23 14 10 160 1,6 117 57 33 20 56 36 22 11 140 1,8 64 30 18 11 30 20 12 11 160 1,8 101 48 29 17 47 31 19 11 180 1,8 152 76 44 26 75 47 28 12 140 2,0 57 27 16 10 26 17 10 12 160 2,0 89 42 25 15 41 27 16 12 180 2,0 133 65 38 23 64 41 25

Pine 9 140 1,5 52 24 15 9 24 16 9 9 160 1,5 82 39 23 14 38 25 15 10 140 1,6 44 20 12 7 20 13 8 10 160 1,6 69 32 19 12 32 21 13 11 140 1,8 38 18 11 6 17 11 7 11 160 1,8 60 28 17 10 27 18 11 11 180 1,8 90 42 25 15 42 27 17 12 140 2,0 33 16 9 6 15 10 6 12 160 2,0 52 24 15 9 24 16 10 801 2.0 78 37 22 13 36 24 14

Stay data in respect of poles in this table Ult.

load Max. load

kN kN 20 mm grade 300 W stay rod 94,2 38 24 mm grade 300 W stay rod 135 54 7/3,35 1100 MPa stay wire 67,9 27 7/4,00 1100 MPa stay wire 96,8 39 19/2,65 1100 MPa stay wire 115 46 Anchor combination Deviation angle capability factor of safety = 2 Stay rod Stay wire FOX MINK HARE FIR PINE OAK One 0 mm 7/3,35 1100 MPa 51 30 18 50 32 19 TWO 20 mm 7/3,35 1100 MPa 102 60 36 100 84 38 One 20 mm 7/4,00 1100 MPa 73 42 25 71 45 27 TWO 20 mm 7/4,00 1100 MPa 146 84 50 142 90 54 One 24mm 19/2,65 1100 MPa 93 52 31 91 56 33 Two 24 mm 19/2,65 1100 MPa All 104 62 All 112 66 NOTE - "All" signifies angles of deviation up to 1800. Terminals Stay rod Stay wire FOX MINK HARE FIR NE OAK One 20 mm 7/3,35 1100 MPa No No No No No NO TWO 20 mm 7/3,35 1100 MPa Yes Yes No Yes Yes No One 20 mm 7/4,00 1100 MPa Yes No No Yes No No TWO 20 mm 7/4,00 1100 MPa Yes Yes No Yes Yes Yes One 24mm 19/2,65 1100 MPa Yes No No Yes No No Two 24 mm 19/2,65 1100 MPa Yes Yes Yes Yes Yes Yes

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Annex C (normative)

Description and illustrations of overhead power lin e support standards and related

features Figure C.1 — Intermediate wooden pole structure, vertical, no deviation. Figure C.2 — Intermediate wooden pole structure, vertical, small angle deviation. Figure C.3 — Road crossing intermediate wooden pole structure, vertical, no deviation. Figure C.4 — Suspension wooden pole structure, vertical, medium angle deviation. Figure C.5 — Strain wooden pole structure, vertical, 300 to 900 deviation. Figure C.6 — Strain wooden pole structure, delta, up to 300 deviation. Figure C.7 — H-pole strain wooden pole structure, horizontal, 600 to 900 deviation. Figure C.8 — Long span H-pole suspension wooden pole structure, delta, no deviation. Figure C.9 — Long span H-pole strain wooden pole structure, delta, no deviation. Figure C.10 — Long span triple-pole strain wooden pole structure, delta, no deviation. Figure C. 11 — Terminal wooden pole structure, vertical. Figure C.12 — Terminal wooden pole structure, delta. Figure C.13 — Tee-off wooden pole structure, vertical intermediate to vertical tee-off, no deviation. Figure C.14 — Tee-off wooden pole structure, vertical intermediate to delta tee-off, no deviation. Figure C.15 — Recloser or sectionalizer strain wooden pole structure, horizontal, no deviation. Figure C.16 — In-line isolating strain wooden pole structure, delta, no deviation. Figure C.17 — Pole-mounted CSP transformer, mass < 760 kg, terminal wooden pole structure, delta. Figure C.18 — Pole-mounted transformer, mass < 760 kg, intermediate wooden pole structure, vertical, no deviation. Figure C.19 — Platform-mounted transformer, 760 kg < mass < 2000 kg, terminal wooden pole structure, horizontal. Figure C.20 — Platform-mounted transformer, 760 kg < mass < 2000 kg, terminal wooden pole structure, vertical. Figure C.21 — Delta to vertical phase configuration intermediate wooden pole structures. Figure C.22 — Pole foundation detail. Figure C.23 — Stay anchor assembly installation detail. Figure C.24 — Rock anchor assembly installation detail. Figure C.25 — Stay assembly detail. Figure C.26 — Overhead (flying) stay arrangement detail. Figure C.27 — Conductor tie installation for pin and post insulators.

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Annex D (informative)

Project example

D.1 General The construction of a medium voltage overhead line in terms of the guidelines is illustrated, using the following example: A supplier of electricity has to provide a power supply to a pump station and sewerage works, and exploits the opportunity to supply electricity to a farm en route. A road crossing, rail crossing and valley crossing are encountered. It is presupposed that the electricity supplier determines the desired power supply parameters for the project as outlined in 5.1, and has finalized the issues raised in 5.1 and 5.2.

D.2 The power distribution system planning phase (s ee 5.1) D.2.1 The supply voltage is determined: 22 kV. D.2.2 The type of conductor is selected: FOX. D.2.3 The type of construction is chosen: Wooden poles. D.2.4 The system electrical protection comprises: a) an auto-recloser/switchgear or circuit-breaker with isolating and bypass links at the tee-off from the main

line; b) solid isolating links at subsequent tee-offs; and c) fuses and surge arresters at transformers. D.2.5 A schematic layout of the overhead line is prepared and is as shown in Figure D.1. D.3 Spanning plan D.3.1 Figure D.2 shows the result of the application of the procedure (described in annex B of this guideline) to the power fine project. D.3.2 The railway crossed in the example is an electrified line and as such, the time allowed to effect the crossing is restricted since the electrical supply to the railway line has to be disconnected. An outage will have to be arranged. Two strain pole structures are selected for either side of the railway line, to enable the construction of the line to proceed unhampered, whilst the crossing can be completed at a convenient time. D.3.3 The power line should be at least 1.8 m above the Telkom line. D.3.4 In this example, the fixed points are: a) tee-off from existing line; b) auto-recloser; c) first angle; d) road crossing (NB: In this case, the road will be crossed with intermediate structures.); e) rail crossing (NB: Strain structures are selected to facilitate construction arrangements with Spoornet.); f) tee-off to village pump;

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g) valley; h) angle near sewerage works: i) terminal at sewerage works; j) links on village pump tee; k) chicken farm transformer; 1) angle approaching village pump; and m) village pump transformer.

D.4 Distances The distances shown between structures on the spanning plan in Figure D.2 are selected by application of the procedures outlined in B.2 (c) to (f). As an example, consider the portion of the route between fixed point 1 (auto-recloser) and 4 (first angle). The distance is 305 m. Taking the span capabilities of the appropriate structures into account, it is determined that three span lengths of approximately 100 m each, are required. Furthermore taking local site conditions into account, span lengths of 110 m, 95 m and 100 m are chosen. D.5 Survey The next step in the process depends on whether or not a surveyor is to peg the structure positions. In this example, the services of a surveyor are used and the structure pegs will be placed by him in the best position possible whilst keeping within the limitations of the selected structures. Examples of a case where the surveyor would adjust a structure position could be: a) where ground water exists; or b) where there are rock outcrops or where rocks are known to be present. Once the spanning plan is complete, it is advisable to prepare a structure schedule, as shown for this example in Tables D.1 and D.2, to facilitate preparation of a bill of materials and to assist the construction supervisor.

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Table D.1 — Structure schedule Wye village electrification extension sewerage work s tee-off from existing

Exe/Wye 22 kV line Voltage: 22 kV Conductor: FOX 6/1/2, 9 mm ACSR Route length: 1844 m Conductor length: 4736 m = (route length times 3) + 2.5 %

1 2 3 4 5 6

Structure type number on figure D.2

Type Drawing number

Span length

mm

Section length

m

Remarks/ ins tructions

EIW 63 Existing Figure C. 14 0 Tee/arrangement only/FOX to MINK auto-recloser with bypass

1 Strain Figure C.15 50 50 2 Intermediate Figure C.1 110 3 Intermediate Figure C.1 95 4 Light angle Figure C.2 100 80 deviation left 5 Intermediate Figure C.3 110 Road crossing Span 5-6 6 Intermediate Figure C.3 65 7 Strain Figure C.12 80 560 Rail crossing Span 7-8

8 Strain Figure C.12 40 40 9 Inter. tee Figure C. 14 50 Tee to village pump/spur 10 Intermediate Figure C.1 115 11 Strain Figure C.9 100 265 Long span Vlei crossing 12 Strain Figure C.9 420 420 13 Angle strain Figure C.5 115 115 650 deviation right 14 Terminal

transformer Figure C. 17 90 90 100 kVA CSP transformer(mass < 760

kg) TOTAL ROUTE LENGTH 15540

Structure summary: 11 m × 160 mm top diameter. 55 MPa. Wooden poles. 16 required. NOTE Auto-recloser to be graded to suit protection on EXEANYE feeder.

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Table D.2 — Structure schedule

Wye village pump 22 kV tee-off from sewerage works feeder Voltage: 22 kV Conductor: FOX 6/1/2.79 mm ACSR Route length: 1843 m Conductor length: 3330 m = (route length times 3) + 2.5 %

1 2 3 4 5 6 Structure type

number on figure D.2

Type Drawing number

Span length mm

Section length

m

Remarks/ instructions

EIW VPT 9 Existing Figure C.14 0 Tee/arrangement only/FOX to FOX section links

T1 Strain Figure C.1 6 50 50 T2 Intermediate Figure C.1 120 T3 Intermediate Figure C.1 115 T4 Transformer Figure C.18 100 Chicken farm100 kVA transformer T5 Intermediate Figure C.1 108 T6 Angle susp. Figure C.4 115 T7 Intermediate Figure C.1 120 T8 Intermediate Figure C.1 115 T9 Intermediate Figure C.1 120 T10 Terminal

transformer Figure C.17 120 1033

TOTAL ROUTE LENGTH 1083

Structure summary: 11 m × 160 mm top diameter. 55 MPa. Wooden poles. 10 required.

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Annex E (informative)

Bibliography

IEC 61109:1992, Composite insulators for a.c. overhead lines with a nominal voltage greater than 1000 V — Definitions, test methods and acceptance criteria NRS 022:1993, Electricity distribution — Stays and associated components NRS 027:1994, Distribution transformer — Completely self-protecting type for rated voltages up to and including 33 kV NRS 041:1995, Electricity transmission and distribution — Code of practice for overhead lines for conditions prevailing in South Africa

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