UDC 621.315.668.1
ICS 29.240
ISBN 0-626-10996-5
NRS 033:1996
First Edition

NRS 033:1996 1
Page
Foreword................................................................................................................................2
Introduction ............................................................................................................................4
2
3
Key words .............................................................................................................................4
1 Scope...........................................................................................................................
5
4
Normative references...................................................................................................5
Definitions ....................................................................................................................6
Application design guides.............................................................................................7
4.1
Preferred structures, conductors and components.................................................7
4.2
Wind loading and loading levels ...........................................................................8
4.3
Minimum factors of safety ....................................................................................8
4.4
Use of vibration dampers .....................................................................................9
4.5
Minimum clearances ............................................................................................9
4.6
Basic insulation level, earthing and surge protection ............................................9
4.7
Recommended crossing practice ..........................................................................10
4.8
Support structure function .....................................................................................10
5
6
Planning guidelines .....................................................................................................14
5.1
The power distribution system planning phase .....................................................14
5.2
The pre-construction planning phase ....................................................................14
Construction guidelines ...............................................................................................17
6.1
Delivery and handling ..........................................................................................17
6.2
Assembly or dressing ...........................................................................................17
6.3
Excavation ...........................................................................................................18
6.4
Erection, backfilling and stay installation ...............................................................18
6.5
Conductor erection ...............................................................................................21
6.6
Transformer and switchgear erection ...................................................................23
6.7
Route reinstatement and clearing .........................................................................23
6.8
Labelling of structures ..........................................................................................23
6.9
Inspection ............................................................................................................23
Figures
1 Pole pike .....................................................................................................................20
A.1
Formed armoured road crossing twin tie for vertically mounted pin or post insulator ....25
A.2
Formed arcing horn for horizontally mounted long rod insulator ...................................25
A.3
Formed arcing horn for horizontally mounted disc insulator .........................................25
A.4
Crossing with strain structures on both sides ...............................................................26
A.5
Crossing with an intermediate structure on one side and a strain structure on the other side ..............................................................................................................27
A.6
Crossing with intermediate structure on both sides ......................................................27

2 NRS 033:1996
(continued)
Page
A
B
C
D
C.1
Intermediate wood pole structure, vertical no deviation ...............................................42
C.2
Intermediate wood pole structure, vertical, small angle deviation ................................43
C.3
Road crossing intermediate wood pole structure, vertical, no deviation .......................44
C.4
Suspension wooden pole structure, vertical, medium angle deviation ..........................45
C.5
Strain wooden pole structure, vertical 30° to 90° deviation ..........................................46
C.6
Strain wooden pole structure, delta, up to 30° deviation ...............................................48
C.7
H-pole strain wooden pole structure, horizontal, 60° to 90° deviation ...........................48
C.8
Long span H-pole suspension wooden pole structure, delta, no deviation ....................49
C.9
Long span H-pole strain wooden pole structure, delta, no deviation .............................50
C.10
Long span triple-pole strain wooden pole structure, delta, no deviation ........................51
C.11
Terminal wooden pole structure, vertical .....................................................................52
C.12
Terminal wooden pole structure, delta .........................................................................53
C.13
Tee-off wooden pole structure, vertical intermediate to vertical tee-off, no deviation ...54
C.14
Tee-off wooden pole structure, vertical intermediate to delta tee-off, no deviation .......55
C.15
Recloser or sectionalizer strain wooden pole structure, horizontal, no deviation ..........56
C.16
In-line isolating strain wooden pole structure, delta, no deviation .................................57
C.17
Pole mounted CSP transformer, mass <760 kg, terminal wooden pole structure, delta 58
C.18
Pole mounted transformer, mass <760 kg, intermediate wooden pole structure, vertical, no deviation ...................................................................................................59
C.19
Platform mounted transformer, 760 kg <mass <2000 kg, terminal wooden pole structure, horizontal .....................................................................................................60
C.20
Platform mounted transformer, 760 kg <mass <2 000 kg, terminal wood pole structure, vertical ........................................................................................................................
61
C.21
Delta to vertical phase configuration intermediate wooden pole structures ..................62
C.22
Pole foundation detail ..................................................................................................63
C.23
Stay anchor assembly installation detail ......................................................................64
C.24
Rock anchor assembly installation detail .....................................................................65
C.25
Stay assembly detail ....................................................................................................66
C.26
Overhead (flying) stay arrangement detail ...................................................................67
C.27
Conductor tie installation detail on pin or post insulator ...............................................68
D.1
Schematic lay-out Wye electrification extension ..........................................................71
D.2
Wye village electrification extension spanning plan .....................................................72
D.3
Wye village electrification extension construction programme .....................................75
Annexes
Design of crossings of proclaimed roads, railway lines, tramways and important communication lines with a power lines .......................................................24
Procedure for positioning of structures on a surveyed route plan .................................29
Description and illustrations of overhead power line support standards and related features ............................................................................................................40
Project example ..........................................................................................................69
ISBN 0-626-10996-5

NRS 033:1996 3
Foreword
These guidelines have been prepared on behalf of the Electricity Suppliers Liaison Committee (ESLC) and approved by it for use by supply authorities and other interested parties.
These guidelines have been prepared by a Working Group comprising the following members:
A J Poulton (Chairman)
J W J Dixon
R Dhrochand
A D du Plessis
J C Fivaz
G R Marshall
M D McIntosh
P A Johnson
D M Michie
C N Ravera
R G Stephen
L J Verster
Technology Consultancy Services (Pty) Ltd.
Technology Consultancy Services (Pty) Ltd.
Durban Electricity
Department of Manpower
Bloemfontein Electricity Department
Merz & McLellan (South Africa)
Johannesburg Electricity Department
NRS Project (Project Leader)
Port Elizabeth Electricity Department
Eskom (Transmission Engineering)
Eskom (Transmission Engineering)
Pretoria Electricity Department
The Working Group was appointed by the ESLC which, at the time of approval, comprised the following members:
F H D Conradie
B F Berwyn-Taylor
A J Claasen
P Crowdy
R W Curtis
J A Ehrich
A H L Fortmann
R B Gwilt
D F Hunt
I P Kruger
J G Malan
J Maroga
A Lock
A J van der Merwe
H R Whitehead
National PTM&C Manager, Eskom
City Electrical Engineer, Cape Town, AMEU
Manager, Electrical Engineering Standards, SABS
Distribution Planning Manager, Eskom
JCI, for Chamber of Mines of South Africa
City Electrical Engineer, Pretoria, AMEU
City Electrical Engineer, Boksburg, AMEU
City Electrical Engineer, Port Elizabeth, AMEU
Corporate Technology Standardization Manager, Eskom
Director, Department of Electrical Engineering, SABS
City Electrical Engineer, Kempton Park, AMEU
Distribution Technology Manager, Eskom
Director, Electrical Engineering, Johannesburg Electricity
City Electrical Engineer, Bloemfontein, AMEU
Executive Director, Durban Electricity, AMEU
Annexes A, B and C form an integral part of this guide.
Annexes D and E are for information only.
Recommendations for corrections, additions or deletions should be addressed to the NRS Project
Manager, c/o SABS, Private Bag X191, Pretoria, 001.
Introduction

4 NRS 033:1996
The planning and construction of medium voltage overhead lines are regularly undertaken by electricity suppliers. The ESLC commissioned the compilation of these guidelines 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.
The techniques proposed, and the designs given, are in accordance with the Occupational Health and
Safety Act, 1993 (Act 85 of 1993).
Key words
Guidelines; Overhead power lines ; Electricity distribution.

NRS 033:1996
5
These guidelines are intended for use by an experienced person as defined in the Occupational Health and Safety Act, 1993 (Act 85 of 1993), of Regulation 11 of the General Safety Regulations, 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 NRS 041.
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 and the OHS
Act 1993, as amended.
The following standards contain provisions which, through reference in the text, constitute provisions of these guidelines. At the time of publication, the editions indicated were valid. All standards are subject to revision and parties to purchase agreements base on these guidelines are encouraged to investigate the possibility of applying the most recent edition of the standards listed below. Information on currently valid national and international standards can be obtained from the South African Bureau of Standards.
BS 3242:1970, Specification for aluminium alloy stranded conductors for overhead power transmission.
IEC 433:1980, Characteristics of string insulator units of the long rod type.
IEC 1089:1991, Round wire concentric lay overhead electrical stranded conductors.
NRS 039:1995, Guideline for the application of gapless metal oxide surge arresters in distribution systems .
SABS 182-3:1975, Aluminium Conductors, steel reinforced.
SABS 753, Pine poles, cross arms and spacers for power distribution, telephone systems and street lighting.
SABS 754:1994, Eucalyptus poles, cross arms and spacers for power distribution and telephone systems.
SABS IEC 305:1978, Characteristics of string insulator units of the cap and pin type.
SABS IEC 383-1:1993, 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.
SABS IEC 720:1981, Characteristics of line post insulators.

6
For the purposes of these guidelines, the following definitions apply:
NRS 033:1996
The test voltage, under specified conditions, that the insulation of a device is designed to withstand.
completely self-protected (CSP) transformer: A transformer that is designed to be self-protected against overloads, short-circuits and overheating.
dressing of poles: The attachment of hardware and accessories to poles.
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 OHS Act, 1993, and its implications; b) trained in the construction of overhead lines; and c) aware of the dangers associated with the construction of overhead lines.
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).
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.
lightning impulse withstand voltage: The lightning impulse voltage that an insulator, under prescribed conditions of test, will withstand when the insulator is dry.
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.
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).
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.
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.

NRS 033:1996 7
structure: A dressed and erected single pole or multipole assembly, including cross-arms and hardware.
templating: The activity of placing or positioning the structure on the ground profile, drawing or map.
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.
4.1 Preferred structures, conductors and components
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 phaseto-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.
Insulators should comply with the relevant of the following standards: a) SABS IEC 305 for disc insulators; b) SABS IEC 383-1 for ceramic or glass insulators; c) SABS IEC 433 for long rod insulators; and d) SABS IEC 720 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 1109 should be considered.

8
Table 1 — Mechanical characteristics of insulators
NRS 033:1996
1 2 3
Insulator type and application
4
Pin or post, intermediate
Pin or post road crossing, small deviation
Long rod or disc, intermediate
Minimum mechanical failing load, kN (see 4.1.2)
Long rod or disc, strain
4
(cantilever)
10
(cantilever)
1
or to suit conductor tension.
40
(tensile)
40
1
(tensile)
Table 2 — Electrical characteristics of insulators
1
Nominal r.m.s. system voltage
11
22
2
Rated peak lightning impulse withstand voltage
95
150 min.
3
Rated wet power frequency r.m.s.
withstand voltage
28
50
The standard atmospheric pollution level in South Africa 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, U m
. Where other conditions prevail, the creepage distance should be as specified in table 3.
Table 3  Creepage distances between phase and earth
1
Pollution level
Light
Medium
Heavy
Very heavy
2
Minimum specific creepage distance between phase and earth mm per kV of U m
16
20
25
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 do safety that should be used are:
— Wooden poles not continuously loaded : 2,7 based on ultimate fibre stress (bending loads)

NRS 033:1996 9
— 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
— Stay assemblies :
: 2,5 based on type-tested breaking strength
2,5 based on type-tested breaking strength
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, long valleys or long rivers the use of vibration dampers should be considered.
4.5 Minimum clearances
The minimum clearances, as required by the OHS Act, 1993, for the range of voltages covered by these guidelines are shown in table 4.
Table 4 — Minimum clearances for bare conductors in accordance with regulation 15 of the Electrical Machinery Regulations
1 2 3 4 5 6
Maximum r.m.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 kV
1,1 or less
7,2
12
24
36
48
72
100
145
245
300
362
420
800 m
1,00
1,45
1,85
2,35
2,90
3,20
5,50
−
0,15
0,20
0,32
0,43
0,54
0,77 m
4,9
5,0
5,1
5,2
5,3
5,4
5,7
5,9
6,3
6,7
7,2
7,8
8,1
10,4 m
5,5
5,5
5,5
5,5
5,5
5,5
5,7
5,9
6,3
6,7
7,2
7,8
8,1
10,4 m
6,1
6,2
6,3
6,4
6,5
6,6
6,9
7,1
7,5
7,9
8,4
9,0
9,3
11,6
NOTE — The minimum safety clearance is equal to the minimum safe approach clearance.
1,6
2,0
2,4
2,9
3,5
3,8
6,1
0,6
0,7
0,8
0,9
1,0
1,1
1,4
To communication lines, other power lines or between power lines and cradles m
7
To buildings, poles and structures not forming part of power lines m
3,4
3,8
4,2
4,7
5,3
5,6
8,5
3,0
3,0
3,0
3,0
3,0
3,0
3,2
4.6 Basic insulation level, earthing and surge protection
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,

10 NRS 033:1996 system performance and damage to wooden poles in areas of medium to high lightning activity
(> 4 flashes/km
2
/year).
Where earth wires are required on a structure, these are shown in the relevant figures in annex C.
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.
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.
Surge arresters should be provided to protect equipment and structures that 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.
All stays should have stay insulators. The stay insulators should be fitted approximately 1 500 mm from the stay attachment point on the pole.
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, 1 100 MPa stay wire and
100 kN for a 7/4,0, 1 100 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.
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 retaomed.
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 SABS 753 or SABS 754 (as relevant). 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.

NRS 033:1996 11
The functions of the typical structures are as given in 4.8.1 to 4.8.7.2.
(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 capabilities of these structures are obtainable from tables B.1 and B.2 in annex B.
(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.
(see figure
C.3)
This intermediate structure should be used where the line crosses a road without the line’s changing direction.
(see figure C.4)
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.
(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.
(see figure C.6)
This structure should be used for all strain positions where the line deviation does not exceed 30
. These structures should also be used on all rail crossings.
(see figure C.7)
This structure should be used where a line using hare or oak conductor (see table B.1 and table B.2), is required to be angled in the range 60° to 90°.
(see figure
C.8)
This structure should be used on spans from 180 m up to 470 m, for conductors in a delta formation, without any deviation.
(see figure C.9)

12 NRS 033:1996
This structure should be used on spans from 180 m up to 470 m. It is designed to prevent the conductors from touching, causing interruptions in the supply.
(see figure
C.10)
This structure illustrates the use of a triple-pole strain structure, which may be used to support long spans of conductor in a delta formation, with no deviation, up to a span of 700 m.
(see figure C.11)
The structure illustrates the termination of conductors in a vertical configuration.
(see figure C.12)
This structure illustrates the termination of conductors in a delta configuration.
(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.
(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.
(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.
(see figure C.16)
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.
(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.

NRS 033:1996 13
(see figure C.18)
This structure is the same as illustrated in figure C.17, but for use in the in-line position. The maximum transformer mass that may be used on this structure is 760 kg.
(see figure C.19)
This structure should be used to support a transformer of mass exceeding 760 kg but not exceeding
2 000 kg. The structure can either be a terminal structure or an in-line strain structure.
(see figure C.20)
This structure should be used to support a transformer and associated equipment of mass exceeding
760 kg but not exceeding 2 000 kg, where the line is in the vertical configuration.
(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.
(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.
(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.
(see figure C.24)
This illustrates the application of a double-eyed stay rod and a rock anchor for anchoring a stay wire assembly.
(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.
(see figure C.26)
This illustrates the arrangement of an overhead stay which is used where clearance above a road is required.
(see figure C.27)
This illustrates conductor tie installation details for pin and post insulators.

14 NRS 033:1996
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
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.
NOTES
1 In these guidelines, a surveyor means a surveyor experienced in the survey of power lines.
2 The services of a surveyor are assumed in the power line project example described in annex D.
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.

NRS 033:1996 15
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 landowner 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
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 to that signature of the contract be finalized 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. 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 crosssection for slopes that exceed 5°. 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, distances specified 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.

16 NRS 033:1996
The next step is to peg all the support structure positions on the ground. At the same time, any stay positions are also pegged.
A procedure to select appropriate span lengths and to determine suitable positions for the location of 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).
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;
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.
5.2.4.1
The person responsible for the construction of the project should appoint, in writing, an experienced person as a construction supervisor in terms of regulation 11 of the General Safety
Regulations of the OHS Act., 1993.
5.2.4.2
The construction supervisor's 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

NRS 033:1996 17
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.
6.1 Delivery and handling
The way of laying poles upon delivery is dependent on the methods of excavation, dressing and erection.
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.
Poles of the correct length and diameter should be delivered to each peg.
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.
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.
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.
Dressing of poles should preceed 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.

18 NRS 033:1996
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 and in a straight vertical line, holes being drilled perpendicularly to the pole axis where required and insulator alignment and separation should be carried out with care.
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 be 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.
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 be 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. Refer to Regulation 16 of the Electrical Machinery Regulations of the OHS Act, 1993 (Act 85 of 1993).
6.3 Excavation
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.
The holes for the poles and stays should be excavated in accordance with figures C.22 and C.23
of annex C.
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.
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.
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 activity should take place immediately after the excavation activity.
Erection by crane requires the observance of all safety aspects relating to equipment ratings, equipment stability, and the positioning of workmen.
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 ladder 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.

NRS 033:1996 19
Stayed poles should be so erected that, upon completion of the backfill operation, the pole leans away from the stay position by at least a half a pole diameter at the top. This will ensure correct alignment when the stay is made-off correctly.
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.
The stay should be installed in accordance with figure C.23 of annex C, and carefully backfilled.
When the stay is installed, the stay wire should be made off in accordance with figure C.25 of annex C.

20
75
All dimensions in millimetres
NRS 033:1996
300 300
Handle
Tension stay
There are three basic activities involved in conductor erection. These are:

NRS 033:1996 a) delivery of conductors; b) running out and stringing of conductors; and
21 c) tensioning and regulating of conductors.
As considerable activity occurs around a drum site, care should be taken in the selection of the site position, to prevents 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.
CAUTION — Care should be exercised to prevent conductor damage during the running out operation.
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.
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.
To prevent unnecessary land damage, all conductors should be run out together.
In the case of road crossings, all goalpost scaffolding should be correctly installed beforehand.
All fences should be guarded or protected in order to prevent conductor or fence damage.
Specialized equipment is available for conductor stringing, but it is not needed on short lines.
It is preferable to use commercially available insulator mounted rollers.
Structures that have line deviations and continuous conductors should be equipped with stringing blocks of the correct rating.
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.
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.

22 NRS 033:1996
The end of the conductor is fastened or made-off on the strain or terminal structure at the start of the line.
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 drum’s running speed.
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.
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 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.
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.
When the tensioning position is reached, the conductor can be placed in stringing blocks of correct rating, ready for sagging or tensioning.
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.
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 deadends) can be made-off.
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

NRS 033:1996 23 marked at the centre of the stringing block, and transferred and correctly positioned to the attachment point.
Care should be taken to install ties in accordance with the manufacturer’s instructions.
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.
All temporary stays should be removed during the tying of conductors.
To avoid possible damage to equipment from falling objects, in particular damage to bushings, 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.
Route reinstatement and clearing are important activities, and should be treated as such. The route should be environmentally intact when these activities are 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.
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.
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.

24
Annex A
(normative)
NRS 033:1996
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
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).
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
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.

NRS 033:1996 25
Annex A
Fully armoured conductor
Ties
10 kN insulator
Figure A.1 — Formed armoured road crossing twin tie for vertically mounted pin or post insulator
Thimble clevis
Formed dead-end
Formed arcing horn
Figure A.2 — Formed arcing horn for horizontally mounted long rod insulator
Thimble clevis
Formed dead-end
Formed arcing horn
Figure A.3 — Formed arcing horn for horizontally mounted disc insulator

26
Annex A
(continued)
NRS 033:1996
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 deadends can be used without the fitting as 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.5.1
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).
C C
Telecommunication lines
B B
Road
C C
Stays, if required

NRS 033:1996 27
Annex A
(continued)
C A
Telecommunication lines
A A B
Road
C C
C A
Telecommunication lines
A A A
Road
A A C

28
Annex A
(continued)
NRS 033:1996
A.5.4
Requirements for strain structures marked B in 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 marked C in figures A.4, A.5 and A.6
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 marked 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.

NRS 033:1996 29
Annex B
(normative)
Procedure for positioning of structures on a surveyed route plan
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.
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 itt 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:
— Table B.1
specifies wooden pole span data for preferred ACSR conductor sizes.
— Table B.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 45°.
— Table B.10 provides data for pole loading with stays at 30°.
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.

30
Annex B
(continued)
NRS 033:1996
Table B.1 : Wooden pole span data for preferred sizes of hard-drawn aluminium steel-reinforced
(ACSR) conductors
1
Wooden pole length
2
Pole top diam.
3
Planting depth
4
Lowest conductor attachment
5
Available for sag
6
Conductor code name
7
Wind span
8
Overturn span
9
Ground level clearance span at
50 ºC m
10
10
10
10
10
9
9
9
10
11
11
11
11
11
11
11
11
11 mm
140
140
140
140
140
140
140
140
140
140
140
140
160
160
160
160
160
160 m
1,5
1,5
1,5
1,5
1,5
1,5
1,6
1,6
1,6
1,8
1,8
1,8
1,8
1,8
1,8
2,0
2,0
2,0 m
6,15
6,15
6,15
7,15
7,15
7,15
7,05
7,05
7,05
7,85
7,85
7,85
7,85
7,85
7,85
7,65
7,65
7,65 m
0,65
0,65
0,65
1,65
1,65
1,65
1,55
1,55
1,55
2,35
2,35
2,35
2,35
2,35
2,35
2,15
2,15
2,15
FOX
MINK
HARE
FOX
MINK
HARE
FOX
MINK
HARE
FOX
MINK
HARE
FOX
MINK
HARE
FOX
MINK
HARE m
132
100
78
120
92
71
121
92
72
113
86
67
161
123
95
164
125
97 m
61
47
95
73
56
94
71
55
79
114
87
67
125
95
74
165
125
97 m
50
50
50
110
110
110
100
100
100
150
150
150
150
150
150
135
135
135
NOTES
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.
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 based on 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 °C.
— wind pressure taken as 700 Pa.

NRS 033:1996 31
Annex B
(continued)
Table B.2 — Wooden pole span data for preferred sizes of all aluminium alloy (AAAC) conductors sizes
1
Wooden pole length
2
Pole top diam
3
Planting depth
4
Lowest conductor attachment
5
Avail able for sag
6
Conductor code name
7
Wind span
8
Overturn span
9
Ground level clearance span at
50 ºC m
11
11
11
11
11
11
11
NOTES
10
10
10
11
11
9
9
9
10
10
10 mm
140
140
140
140
140
140
140
140
140
140
140
140
160
160
160
160
160
160 m
1,5
1,5
1,5
1,6
1,6
1,6
1,6
1,6
1,6
1,8
1,8
1,8
1,8
1,8
1,8
2,0
2,0
2,0 m
6,15
615
6,15
7,15
7,15
7,15
7,05
7,05
7,05
7,85
7,85
7,85
7,85
7,85
7,85
7,65
7,65
7,65 m
0,65
0,65
0,65
1,65
1,65
1,65
1,55
1,55
1,55
2,35
2,35
2,35
2,35
2,35
2,35
2,15
2,15
2,15
FIR
PINE
OAK
FIR
PINE
OAK
FIR
PINE
OAK
FIR
PINE
OAK
FIR
PINE
OAK
FIR
PINE
OAK m
125
102
79
114
93
72
115
94
73
107
88
68
152
125
97
155
127
98 m
89
72
56
75
61
48
90
74
57
108
88
68
118
96
75
156
127
99 m
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.
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 1089, are
FIR 47,84 — A3 — 7/2,95
PINE
OAK
71,65 — A3 — 7/3,61
118,90 — A3 — 7/4,65
100
100
100
140
140
50
50
50
110
110
110
140
140
140
140
130
130
130
The data in the table has been calculated based on 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 °C
— wind pressure taken as 700 Pa.

32
Annex B
(continued)
NRS 033:1996

NRS 033:1996 33
Annex B
(continued)

34
Annex B
(continued)
NRS 033:1996

NRS 033:1996 35
Annex B
(continued)

36
Annex B
(continued)
NRS 033:1996

NRS 033:1996 37
Annex B
(continued)

38 NRS 033:1996
Annex B
(continued)
Table B.9 — Pole loadings with stays at 45°
CONDUCTOR TENSION = 40 % OF UTS (see note)
1 2 3 4 5 6 7 8 9 10 11
Pole type
Length m
.
Top dia.
mm
Planting depth m
Ultimate buckling load kN
Maximum deviation angles for conductor of type: degrees
FOX MINK HARE FIR PINE OAK
13,2 33,3 21,8 36,0 13,43 20,2
Pole loading with stays at 45° kN
Gum
11
11
11
12
12
12
10
10
9
9
140
160
140
160
140
160
180
140
160
180
1,5
1,5
1,6
1,6
1,8
1,8
1,8
2,0
2,0
2,0
88
140
74
117
64
101
152
57
89
133
76
157
62
111
53
90
180
47
77
137
Pine
11
12
12
12
10
10
11
11
9
9
140
160
140
160
140
160
180
140
160
180
1,5
1,5
1,6
1,6
1,8
1,8
1,8
2,0
2,0
2,0
52
82
44
69
38
60
90
33
52
78
42
70
36
58
31
49
78
27
43
66
NOTE — Conductor tension has been taken as 40 % of ultimate tensile strength.
45
16
26
39
25
41
21
34
18
29
32
51
80
28
44
69
44
73
37
60
26
42
22
35
19
30
46
17
26
40
15
24
13
20
11
18
27
10
15
23
74
149
61
108
52
88
180
46
75
133
42
69
35
57
30
48
76
27
42
65
47
80
40
65
34
55
88
30
48
75
27
44
23
37
20
32
48
18
28
42
21
33
50
18
29
43
28
46
24
38
29
11
17
25
16
26
14
22
12
19
Stay data in respect of poles in this cable
20 mm grade 300 W stay rod
24 mm grade 300 W stay rod
7/3,35 1100 MPa stay wire
7/4,00 1100 MPa stay wire
19/2,65 1100 MPa stay wire
Ult. load kN
94,2
135
67,9
96,8
115
Max. load kN
38
54
27
39
46
Anchor combination
Stay rod Stay wire FOX
One
Two
One
20 mm
20 mm
20 mm
7/3,35 1100 MPa
7/3,35 1100 MPa
7/4,00 1100 MPa
74
148
114
Two
One
20 mm
24 mm
7/4,00 1100 MPa
19/2,65 1100 MPa
All
All
Two 24 mm 19/2,65 1100 MPa All
NOTE — “All” signifies angles of deviation up to 180°.
Terminal stays
Stay rod
One
Two
One
Two
One
Two
20 mm
20 mm
20 mm
20 mm
24 mm
24 mm
Stay wire
7/3,35 1100 MPa
7/3,35 1100 MPa
7/4,00 1100 MPa
7/4,00 1100 MPa
19/2,65 1100 MPa
19/2,65 1100 MPa
FOX
Yes
Yes
Yes
Yes
Yes
Yes
Deviation angle capability factor of safety = 2,5
MINK
43
86
61
122
77
154
HARE
25
50
36
72
44
88
FIR
73
146
112
224
All
All
PINE
46
92
66
132
84
168
MINK
No
Yes
Yes
Yes
Yes
Yes
Annex B
HARE
No
Yes
No
Yes
No
Yes
FIR
Yes
Yes
Yes
Yes
Yes
Yes
PINE
No
Yes
Yes
Yes
Yes
Yes
OAK
No
Yes
No
Yes
No
Yes
OAK
28
56
39
78
48
96

NRS 033:1996
1
Pole type
Gum
Pine
2
Length m
10
10
11
9
9
11
11
12
12
12
11
11
11
12
12
12
10
10
9
9
.
3
Top dia.
1,5
1,5
1,6
1,6
1,8
1,8
1,8
2,0
2,0
2,0
1,5
1,5
1,6
1,6
1,8
1,8
1,8
2,0
2,0
2,0 mm
140
160
140
160
140
160
180
140
160
180
140
160
140
160
140
160
180
140
160
180
52
82
44
69
38
60
90
33
52
78
88
140
74
117
64
101
152
57
89
133
39
4
Planting depth m
(concluded)
Table B.10 — Stay load at 30°
5
Ultimate buckling load kN
6 7 8 9 10 11
Maximum deviation angles for conductor of type: degrees
FOX
13,2
MINK
21,8
HARE
36,0
FIR
13,43
PINE
20,2
OAK
33,3
Pole loading with stays at 45° kN
42
69
35
57
30
48
76
27
42
65
24
39
20
32
18
28
42
16
24
37
25
40
21
33
18
29
44
16
25
38
15
23
12
19
11
17
25
9
15
22
15
24
13
20
11
17
26
10
15
23
9
14
7
12
6
10
15
6
9
13
41
68
34
56
30
47
75
26
41
64
24
38
20
32
17
27
42
15
24
36
Stay data in respect of poles in this table
20 mm grade 300 W stay rod
24 mm grade 300 W stay rod
7/3,35 1100 MPa stay wire
7/4,00 1100 MPa stay wire
19/2,65 1100 MPa stay wire
Ult. load kN
94,2
135
67,9
96,8
115
Max. load kN
38
54
27
39
46
Anchor combination
Stay rod
One
Two
One
Two
One
Two
20 mm
20 mm
20 mm
20 mm
24 mm
24 mm
Stay wire
7/3,35 1100 MPa
7/3,35 1100 MPa
7/4,00 1100 MPa
7/4,00 1100 MPa
19/2,65 1100 MPa
19/2,65 1100 MPa
FOX
51
102
73
146
93
All
NOTE — “All” signifies angles of deviation up to 180°.
Terminal stays
Stay rod
One
Two
One
Two
One
Two
20 mm
20 mm
20 mm
20 mm
24 mm
24 mm
Stay wire
7/3,35 1100 MPa
7/3,35 1100 MPa
7/4,00 1100 MPa
7/4,00 1100 MPa
19/2,65 1100 MPa
19/2,65 1100 MPa
FOX
No
Yes
Yes
Yes
Yes
Yes
MINK
No
Yes
No
Yes
No
Yes
Deviation angle capability factor of safety = 2
MINK
30
60
42
84
52
104
HARE
18
36
25
50
31
62
FIR
50
100
71
142
91
All
PINE
32
84
45
90
56
112
HARE
No
No
No
No
No
Yes
FIR
No
Yes
Yes
Yes
Yes
Yes
PINE
No
Yes
No
Yes
No
Yes
OAK
No
No
No
Yes
No
Yes
OAK
19
38
27
54
33
66
16
25
13
21
11
18
27
10
16
24
20
31
47
17
27
41
27
43
23
36
9
15
8
13
7
11
17
6
10
14
12
19
28
10
16
25
16
26
14
22
ANNEX C

40
(normative)
NRS 033:1996
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, 30° to 90° deviation.
Figure C.6 - Wooden pole structure, delta, up to 30° deviation.
Figure C.7 - H-pole strain wooden pole structure, horizontal, 60° to 90° 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 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 < 2 000 kg, terminal wooden pole structure, horizontal.
Figure C.20 - Platform-mounted transformer, 760 kg < mass < 2 000 kg, terminal wooden pole structure, vertical.
Figure C.21 - Delta to vertical phase configuration intermediate wooden pole structures.
Figure C.22 - Pole foundation detail.
ANNEX C

NRS 033:1996 41
(continued)
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.
ANNEX C
(continued)

42 NRS 033:1996

NRS 033:1996 43
ANNEX C
(continued)

44
ANNEX C
(continued)
NRS 033:1996

NRS 033:1996 45
ANNEX C
(continued)

46
ANNEX C
(continued)
NRS 033:1996

NRS 033:1996 47
ANNEX C
(continued)

48
ANNEX C
(continued)
NRS 033:1996

NRS 033:1996 49
ANNEX C
(continued)

50
ANNEX C
(continued)
NRS 033:1996

NRS 033:1996 51
ANNEX C
(continued)

52
ANNEX C
(continued)
NRS 033:1996

NRS 033:1996 53
ANNEX C
(continued)

54
ANNEX C
(continued)
NRS 033:1996

NRS 033:1996 55
ANNEX C
(continued)

56
ANNEX C
(continued)
NRS 033:1996

NRS 033:1996 57
ANNEX C
(continued)

58
ANNEX C
(continued)
NRS 033:1996

NRS 033:1996 59
ANNEX C
(continued)

60
ANNEX C
(continued)
NRS 033:1996

NRS 033:1996 61
ANNEX C
(continued)

62
ANNEX C
(continued)
NRS 033:1996

NRS 033:1996 63
ANNEX C
(continued)

64
ANNEX C
(continued)
NRS 033:1996

NRS 033:1996 65
ANNEX C
(continued)

66
ANNEX C
(continued)
NRS 033:1996

NRS 033:1996 67
ANNEX C
(continued)

68
ANNEX C
(concluded)
NRS 033:1996

NRS 033:1996 69
ANNEX D
(informative)
Project example
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 enroute. 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.
(see 5.1)
The supply voltage is determined: 22 kV
The type of conductor is selected: FOX
The type of construction is chosen: Wooden poles
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;
A schematic layout of the overhead line is prepared and is as shown in figure D.1.
Figure D.2 shows the result of the application of the procedure (described in annex B of this guideline) to the power line project.
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.
The power line should be at least 1,8 m above the Telkom line.
In this example, the fixed points are: a) tee-off from existing line; b) auto-recloser; c) first angle; d) road crossing (N.B. In this case, the road will be crossed with intermediate structures);

70 NRS 033:1996
ANNEX D
(continued) e) rail crossing (N.B. Strain structures are selected to facilitate construction arrangements with
Spoornet); f) tee off to village pump; g) valley; h) angle near sewerage works; i) terminal at sewerage works; j) links on village pump tee; k) chicken farm transformer; l) angle approaching village pump; and m) village pump transformer.
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.
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.

NRS 033:1996 71
ANNEX D
(continued)

72 NRS 033:1996
ANNEX D
(continued)
Figure C.14
50 m
1
Exe to Wye 22 kV line
Figure C.15
Figure C.1
110 m
2
95 m
Auto-recloser
Figure C.1
3
100 m
Figure C.2
4
110 m
1 Pr Telkom
8º
5
Figure C.3
Figure C.3
7
65 m
Exe to Wye gravel road
6
80 m
Figure C.6
40 m
Railway single line
8
Figure C.6
50 m
Figure C.14
115 m
9
50 m
T1
Figur e
C.16
12
0 m
T2
Links
T3
10
0 m
Fi gu re
C.
11
5 m
Fi gu re
C.
T4
Fi gu re
C.
18
Figure C.1
10
100 m
11
Chicken farm
100 kVA Transformer
10
8 m
T5
Fi gu re
C.
11
5 m
Fi gu re
C.
T6 12
Wye village pumps
150 kVA Transformer
0 m
T7
11
5 m
Fi gu re
C.
T8
12
0 m
Fi gu re
C.
T9
Figure C.9
T1
0
Fi gu
C.
0 m
Fi gu re
C.
19
420 m
Route length = 1 083 m
Valley
Sewerage works
100 kVA Transformer
Figure C.17
14
Figure C.9
12
13
115 m
Figure C.5
65º
Route length = 1 580 m

NRS 033:1996 73
ANNEX D
(continued)
1
Structure type number on figure D.2
E/W 63
1
2
3
4
5
8
9
6
7
10
11
12
13
14
2
Type
3
Drawing number
4
Span length
5
Section length
Existing
Strain
Intermediate
Intermediate
Light angle
Intermediate
Figure C.14
Figure C.15
Figure C.1
Figure C.1
Figure C.2
Figure C.3
0
50
110
95
100
110
50
6
Remarks instructions
Tee/arrangement only/FOX to MINK auto recloser with bypass
8° deviation left
Road crossing
Span 5-6
Intermediate
Strain
Figure C.3
Figure C.12
65
80 560 Rail crossing
Span 7-8
Strain
Inter. tee
Figure C.12
Figure C.14
40
50
40
Tee to village pump/spur
Intermediate
Strain
Figure C.1
Figure C.9
115
100 265 Long span.
Vlei crossing
Strain
Angle Strain
Terminal transformer
TOTAL ROUTE LENGTH
Figure C.9
Figure C.5
Figure C.17
420
115
90
420
115
90
1 540
65° deviation right
100 kVA CSP transformer (mass as elsewhere 760 kg)
Structure summary: 11 m x 160 mm top diameter. 55 MPa. Wooden poles. 16 required.
NOTE — Auto-recloser to be graded to suit protection on EXE/WYE feeder.

74
ANNEX D
(continued)
NRS 033:1996
T5
E/W VPT 9
T1
T2
T3
T4
Existing
Strain
Intermediate
Intermediate
Transformer
Intermediate
Figure C.14
Figure
Figure
C.16
Figure C.1
Figure C.1
C.18
Figure C.1
0
50
120
115
100
108
50
Tee/arrangement only/FOX to FOX section links
Chicken farm
100 kVA transformer
T6
T7
T8
T9
T10
Angle susp
Intermediate
Intermediate
Intermediate
Terminal transformer
Figure
Figure
Figure
Figure
C.4
C.1
C.1
C.1
Figure C.17
115
120
115
120
120 1 033
TOTAL ROUTE LENGTH 1 083
Structure summary: 11 m x 160 mm top diameter. 55 MPa. Wooden poles. 10 required.

NRS 033:1996 75
ANNEX D
(concluded)

76
ANNEX E
(informative)
NRS 033:1996
IEC 1109:1992,
NRS 022:1993,
(under revision).
NRS 027:1994
NRS 041:1995,
sabs pta