Overhead transmission lines€¦ · SS-EN 1993-3-1 Eurocode 3: Design of steel structures – Part 3-1: Towers and masts SS-EN 1993-1-10 Design of steel structures – Part 1:10:

SVK

4005

E. v5

.0, 2

016-

03-0

1

SVENSKÅKRAFTNÄTSWEDISH NATIONALGRID

UNIT, BUSINESS AREANTL, Overhead Transmission Lines, Grid Technology TR05-03-1E

OUR REFERENCE

DATE28 May 2020 NLP, NLB, NAL

CONSULTATIONS

TECHNICAL GUIDELINE

%REVISION2

APPROVED

Overhead transmission linesDesign of supports

IntroductionThese guidelines describe the requirements for design of supports for overhead transmission lines and cover material and design. The guidelines intend to guarantee satisfactory performance of supports during the lifetime of the overhead line and shall be used at purchasing of supports

This English text is to be regarded as a translation of the Swedish guideline. The Swedish text and the interpretation thereof shall govern the contract and the legal relations between parties.

TECHNICAL GUIDELINE 28 May 2020 TR05-03-1E rev 2

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Revision Notes Change notes Date

1 TR05-03 har delats upp i två delar och ersatts av TR05-03-1 Konstruktion och TR05-03-2 Tillverkning

2017 / 07 / 04

2 Translated to English. Revised clause: 4, 7.2.2, 7.3.2, 7.6 och 8. 2020 / 05 / 28

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Content

1 References ........................................................................................................... 5

2 Scope .................................................................................................................... 7

3 Definitions ........................................................................................................... 7

4 Design requirements .......................................................................................... 8

5 Loads ................................................................................................................... 8

5.1 Wind load 8

5.2 Loss of tensile force 9

5.3 Cascade rupture case 9

5.4 Support erection and conductor stringing forces 9

6 Dimensioning .................................................................................................... 10

6.1 Material 10

6.1.1 Steel 10

6.1.2 Guy wire 11

6.1.3 Wood 11

6.2 Steel support 11

6.2.1 Lattice supports of steel 12

6.2.2 Tubular steel support 16

6.2.3 Wooden poles 16

7 Requirement during design and drawing execution ....................................... 17

7.1 General rules for execution of steel support parts 17

7.1.1 Internal corners 17

7.1.2 Stress relieving anneal 17

7.1.3 Welded structures to be hot-dip galvanized 17

7.1.4 Attachment of articulated support leg 17

7.2 Bolted joints 17

7.2.1 Sheared joints 18

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7.2.2 Drawn joints 20

7.2.3 Edge distance 22

7.2.4 Bolt placement in bars 22

7.2.5 Hole diameter 22

7.3 Parts for lattice supports of steel 22

7.3.1 Bars 22

7.3.2 Bar joints 22

7.3.3 Intersections 23

7.4 Distance from phase conductor to support 24

7.5 Climbing arrangement 24

7.6 Insulator set and earth wire set attachment 26

7.7 Guys 27

7.8 Control schedules 27

7.9 Plates and warning signs 27

7.9.1 General information 27

7.9.2 Warning signs 27

7.9.3 Support number plate 28

7.9.4 Aircraft number plate 28

7.9.5 Aircraft warning sign 28

7.9.6 Crossarm plates (line designation plates) 28

7.9.7 Navigable water crossing signs 28

7.9.8 Signs prohibiting climbing 28

7.9.9 Optical fibre installation sign 28

8 Documentation ................................................................................................. 28

8.1 Drawings 28

8.1.1 Manufacturing drawings 29

8.2 Calculations 29

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1 References SS-EN 50341-1 Overhead electrical lines exceeding AC 1 kV

Part 1: General requirements-Common specifications SS-EN 50341-2-18 Overhead electrical lines exceeding AC 1 kV (AC)

Part 2-18: National Normative Aspects, Sweden SS-EN 1090-1 Execution of steel structures and aluminium structures

– Part 1: Requirements for conformity assessment of structural components

SS-EN 1090-2 Execution of steel structures and aluminium structures

— Part 2: technical requirement for steel structures ISO 273 Fasteners – Clearance holes for bolts and screws

Metric ISO threads SS-EN ISO 1461 Hot-dip galvanised coatings on fabricated iron and

steel articles — Specifications and test methods SS-EN 1993-1-1 Eurocode 3: Design of steel structures – Part 1-1:

General rules and rules for buildings SS-EN 1993-1-8 Eurocode 3: Design of steel structures – Part 1-8:

Design of joints SS-EN 1993-3-1 Eurocode 3: Design of steel structures – Part 3-1:

Towers and masts SS-EN 1993-1-10 Design of steel structures – Part 1:10: Material

toughness and through-thickness properties EN ISO 4014 Fasteners – Hexagon head bolts – Product grades A

and B EN ISO 4017 Fasteners – Hexagon head bolts – Product grades A

and B EN 10025-2 Hot rolled products of structural steels – Part 2:

Technical delivery conditions for non-alloy structural steels

EN 10025-3 Hot rolled products of structural steels – Part 3:

Technical delivery conditions for normalised/normalised rolled fine grain structural steels

EN 10025-4 Hot rolled products of structural steels – Part 4:

Technical delivery conditions for thermomechanically rolled fine grain structural steels

EN 10149-2 Hot rolled flat products made of high yield strength

steels for cold forming – Part 2: Technical delivery conditions for thermomechanically rolled steels

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EN 10210-1 Hot finished structural hollow sections of non-alloy

and fine grain steels – Part 1: Technical delivery conditions

EN 10219-1 Cold formed welded structural hollow sections of

non-alloy and fine grain steels – Part 1: Technical delivery conditions

EN 10164 Steel products with improved deformation properties

perpendicular to the surface of the product – Technical delivery conditions

EN ISO 10684 Fasteners – Hot-dip galvanised coatings EN 12951 Prefabricated accessories for roofing – Permanently

fixed roof ladders-product specification and test methods

EN 14399-3 Fasteners – High strength structural bolting

assemblies for preloading – Part 3: System HR – Hexagon bolt and nut assemblies

EN ISO 14713-2 Zinc coatings – Guidelines and recommendations for

the protection against corrosion of iron and steel in structures – Part 2: Hot-dip galvanising

EN 15048-1 Fasteners – Non-preloaded structural bolting

assemblies – Part 1: General requirements EN 15048-2 Fasteners – Non-preloaded structural bolting

assemblies – Part 2: Suitability test SS 424 08 06 Hard zinc-coated steel wire strands for overhead lines

– Fe 140 lines EBR handbok "UNDERHÅLL LEDNINGAR 0,4 - 420 kV

TR05-01 Svenska kraftnät Tekniska riktlinjer-Luftledningar

Anläggningsdokumentation TR05-03-2E Svenska kraftnät Technical guidelines-

Manufacturing of supports TR05-12E Svenska kraftnät Technical guidelines-Fittings for

insulator and earth wire set TR08-02E Svenska kraftnät-Detailed requirements for drawings

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2 Scope

These technical guidelines comprise the design of supports made of steel and wood

for overhead transmission lines.

3 Definitions

Technical terms and definitions used in these guidelines.

Support/tower

Structure above foundation intended to support an overhead line.

Steel support/tower

Support made mainly of steel.

Lattice tower

A tower made up of bars of steel arranged so that they are almost solely loaded by

axial forces (compressive and tensile forces) when loaded. Towers with bars of

angle sections joined together with bolted joints are most common, but towers with

bars made of round bars or tubes that are mainly joined together with welded joints

also occur.

Tubular steel tower

Tower made mainly of steel tubing. The tubing is usually conical, with a large

diameter, and its cross-section is polygonal.

Wooden pole

Support where the legs, and in some cases other parts, are made of wood. The

support legs are made out of a whole trunk that is simply cut and debarked.

Crossarm

A horizontally oriented part of the tower that carries lines. A crossarm can be

designed as a bracket or be located between two or more tower legs.

Main bar

A primary part of a framework, usually placed in the outer corners. A framework

bar absorbs global axial forces and bending moments that stress the framework.

Diagonal

A secondary part of a framework, situated between the framework bars that absorb

global transverse forces and turning moments that stress the framework. They also

support the framework bars.

Redundant

A secondary part of a framework, situated between framework bars and diagonals,

or between diagonals. Redundants support framework bars and diagonals, thereby

increasing their tensile force capacity.

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Step bolt

A rod designed to be stepped on when moving on a tower. The step bolt is normally

threaded at the end and is then screwed directly into the steel tower.

4 Design requirements

The calculation of mechanical loads and design of power line supports in this

technical guideline shall be performed in accordance with European standard

SS-EN 50341-1 together with the Swedish national annex SS-EN 50341-2-18. These

two documents are referred to below as SS-EN 50341. References to sections relate

to both the European standard and the Swedish national annex, which must be

read together.

Svenska kraftnät’s lines are executed as unbreakable lines according to

SS-EN 50341, section 3.2.2 (Reinforced lines type 1).

See Svk TR05-03-02E “Manufacturing of supports” for execution of manufacture.

5 Loads

5.1 Wind load The wind load on supports and conductors is calculated according to SS-EN 50341,

sections 4.3 and 4.4.

When designing a support, wind directions according to Table 5A must be checked

if it is not possible to demonstrate that one or more of the wind directions does not

dimension any part of the support or associated foundation.

Table 5A Wind angles

Wind angle Ø towards support

Wind angle Ø towards conductor

0° 20° 45° 60° 90°

0° 0° 45° 45° 90°

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Figure 5A Wind direction

5.2 Loss of tensile force Loss of tensile force (security loads) is calculated according to SS-EN 50341,

section 4.8.

5.3 Cascade rupture case If particularly high security is preferred for this type of load, the calculation

according to section 4.8 is supplemented with a cascade rupture load case in which

all line attachment points are loaded simultaneously with a horizontal force in the

direction of the line equivalent to 50% of the tensioning force at 0 °C and no wind

for suspension sets and 100% of the tensioning force for tension sets or overhead

earth wires.

In this load case, the value of the load factors γG and γQ can be set to 1.0.

5.4 Support erection and conductor stringing forces Support erection and conductor stringing loads (safety loads) are calculated

according to SS-EN 50341, clause 4.9.

Supports must be inspected for the loads occurring during support erection. The

partial coefficient for the dead weight of the support is selected as γG = 1.8

according to SS-EN 50341, Table 4.7/SE.1.

Supports must also be inspected for the loads occurring during conductor

stringing. The conductor tension can be assumed as the initial tension of the

conductor at a temperature of -20 °C. The partial coefficient for forces from

conductors during stringing and sagging, which are connected to the stringing

equipment, is selected as γG = 1.8. γG = 1.43 can be used for dead end conductors,

which are permanently attached to a support. The partial coefficient for the dead

weight of the support can be set to γG = 1.0 in this load case.

Ø

Line direction

Wind

direction

Support leg

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6 Dimensioning

6.1 Material

6.1.1 Steel

Steel plates and bars must be selected on the basis of the standards specified in

Table 6A. The steel material for a support type should be limited to no more than

two with a tensile yield limit ReH (fy) within the 220-420 MPa range.

Table 6A Steel types

Standard Type of steel

EN 10025-2 EN 10025-3 EN 10025-4 EN 10210-1 EN 10219-1 EN 10149-2

Non-alloy steel Normalised fine grain structural steels Thermomechanically rolled fine grain structural steel Non-alloy steel and fine grain structural steel for heat-treated pipes Non-alloy steel and fine grain structural steel for cold-treated pipes High strength steels for cold forming

A toughness grade for steel is selected according to Table 6B, with minimum

requirements stating that steel with a tensile yield limit ReH (fy) from 300 MPa and

upwards must be tested for impact strength at -20 ºC with at least 27 J of impact

energy, and steel with a tensile yield limit under 300 MPa must be tested for

impact strength at 0 ºC with at least 27 J of impact energy.

Table 6B Maximum material thickness for various steels

Strength grade Maximum material thickness (mm)

S275J0 S275J2 S355J2 S355N S355ML

45 65 50 65 90

If so required, plates with improved properties in the thickness direction according

to EN 10164 must be selected if so required for plates loaded with tensile force in

the thickness direction, such as footplates. A quality grade according to EN 10164 is

selected in accordance with SS-EN 1993-1-10, clause 3 and SS-EN 50341-2-18,

7.2.1/SE.1. Calculation of ZEd according to SS-EN 1993-1-10 must be described in

the documentation. When dimensioning footplate size, it is also necessary to

ensure that there is sufficient space for washers and for tightening nuts.

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6.1.2 Guy wire

Fe 140 line according to Swedish standard SS 424 08 06 is selected by preference

as guy wire. See TR 05-4E. The guy wire standard dimensions that shall be selected

in the first case are 89, 142 and 185 mm2. Other dimensions can appear.

6.1.3 Wood

See TR 05-03-2E, clause 4 for requirements and dimensions relating to wooden

poles.

6.2 Steel support Minimum material thickness (mm) must be:

Table 6C Minimum material thickness

Open profile

Closed profile

Main bars in support legs and crossarm

6 4

Main bars in overhead earth wire top

5 4

Main bars of UPE beams 4 -

Other bars 4 3

Redundant bars 3 2.5

Gusset plate 6 or minimum thickness for connecting parts.

Underground bars 7 7

Bars must not exceed a maximum length of twelve (12) metres, for transportation

reasons.

The following rust addition must be applied to steel parts in the ground:

Table 6D Zinc thicknesses

Zinc coating

( m)

Zinc coating (g/m2)

Designation acc. to SS-EN ISO 1461

Rust addition (mm)

215 1550 Fe/Zn 215 1.5

140 1 000 Fe/Zn 165 3.0

Bolts 3.0

This means that the calculated material thickness is increased by the rust addition

value when determining sufficient material thickness. See also instructions on

silicon levels in SS-EN ISO 1461, Annex NA when selecting steel for structures in

the ground.

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6.2.1 Lattice supports of steel

Lattice supports of steel are designed according to SS-EN 50341, section 7.3 and

Annex J.

Lattice support made up of angle bars must be joined together with bolted joints.

Calculation model

In most cases, cantilever framework supports can be calculated using a first-order

theory. However, slender supports may need to be calculated using a second-order

theory. The method in SS-EN 1993-1-1, section 5.2.1, can be used to determine

whether a first or second-order theory should be selected in these cases. Guyed

supports with fastenings articulated at the support must be calculated using a

second-order theory.

Modelling the entire support in a three-dimensional program with the connections

between diagonal bars and framework bars executed as joints is recommended. The

line of the centre of gravity must be used as a system line for angle bars joined

together with bolts at both flanges, and the bolt lines for bars joined together with

bolts in a flange. The bar length between the intersections must be used when

calculating buckling length.

The dimensioning method is based on the fact that only the axial load of the bars is

taken into account. This is why supports can be modelled in software with elements

that merely consider tensile and compressive forces. In an actual support, the bars

are also stressed with bending moments of various sizes, and both support

geometry and detailed design must be executed so that these additional moments

are kept to a minimum.

Additional moments can be divided into two different types: those that occur due to

nodal displacements, i.e. where the intersections of the support are displaced in

relation to one another when the support is deformed under load and those that

occur due to eccentricities at the intersections.

If the support is modelled with elements that absorb moment, such as main

member bars, the additional moments due to the nodal displacements can be

analysed in the calculation model. If the total stress of axial force and bending

moment is well below the tensile yield limit value fy for the material in question, it

is usually possible to omit the additional moments caused by the nodal

displacements.

If the support is modelled with elements that merely absorb tensile and

compressive forces, it is necessary instead to observe that the deformation of the

support model at a load where large angle changes for elements that in reality

consist of a continuous bar indicates that large additional moments will occur in

the actual structure.

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As regards additional moments caused by intersection eccentricity, the calculation

model is usually modelled without eccentricities. For supports made up of angle

bars that are joined together with bolt joints, it is more or less impossible to form

the intersections without eccentricity. Therefore, the intersections must be formed

carefully so as to keep the eccentricities to a minimum.

The following is recommended for supports with main bars made up of angle bars:

Bolt lines for the diagonal bars must intersect one another in the area between the

centre line of the main bar and the line of the centre of gravity of the main bar.

Figure 6A shows an intersection with little eccentricity where the above condition is

fulfilled, and an intersection with great eccentricity where the condition is not

fulfilled.

For diagonal bars and redundant bars attached in one flange, the rules described

below under Dimensioning of bars take into account the eccentricity of the

attachment, and if the bolt line in the bar is oriented according to the rules in

TR05-03-1E clause 7.3.3, the eccentricity of the bar can be considered to have been

taken into account to a sufficient extent.

Intersection with little eccentricity Intersection with great

eccentricity

Figure 6A Intersections with different eccentricities

Dimensioning of bars

The load bearing capacity for bars in lattice supports is calculated according to

SS-EN 50341-2-18, section 7.3. The calculation method for bars in lattice supports

is primarily based on SS-EN 1993-3-1. Table G2 in the standard referred to above,

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which indicates how the effective slenderness factor k is to be calculated, contains

illustrations that cannot be interpreted entirely without ambiguity. The following

figures supplement the illustrations in Table G2. It also specifies the value of the

factor η from section G.1(3) in SS-EN 1993-3-1.

Table 6E Slenderness factors for bar attachments

Attachmen

t type

(Table G2)

Reduction

factor η

(G.1(3))

Example

Not

continuous

at both ends

0.8

Continuous

at one end 0.9

Continuous

at both ends 1.0

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Slenderness ratio

The limits for slenderness ratio λ = L/i specified in SS-EN 50341, Annex J and

SS-EN 1993-3-1, Annex H apply, along with the fact that the slenderness ratio for

the entire length for intersecting diagonals (Ld in SS-EN 1993-3-1, Figure H.1 (II

and IIA)) must not exceed 250. The distance between bolts in the finished structure

must be used to determine slenderness limits.

Dimensioning of redundants

To calculate p according to SS-EN 1993-3-1, H.4(2), using the alternative formula

in SS-EN 50341, Annex J.4.4 is permitted.

Dimensioning of joints

Bolted joints in framework supports are calculated according to SS-EN 50341,

section 7.3.8 and Annex J.5 with reduction factors η according to J.5/SE.1. (Note

that these η factors must not be mixed up with those in SS-EN 1993-3-1, Annex G.)

Dimensioning articulated lattice support legs

Articulated support legs of framework design must be dimensioned according to

SS-EN 50341, section 7.7 and SS-EN 1993-1-1, section 6.4. The initial curvature is

selected according to SS EN 1993-1-1, section 6.4.1.

The slenderness ratio (ratio between the length and the radius of inertia λ = L/i) for

an articulated leg must not exceed 80.

The main bars forces in a four-sided leg with four identical main bars can be

calculated using the formula 6.69 from SS-EN 1993-1-1. However, the original

formula has to be modified as it is based on an element with two main bars.

For four main bars, the formula is

zeff

chyEdz

yeff

chzEdy

EdEdchI

AhM

I

AhMN,N

,

,0,

,

,0,

,22

250

where

yv

Ed

ycr

Ed

I

EdyzEd

Edy

S

N

N

N

MeNM

,,

,,0

,

1

zv

Ed

zcr

Ed

I

EdzyEd

Edz

S

N

N

N

MeNM

,,

,,0

,

1

.

16 (30)


The diagonal forces in the element are calculated from the maximum transverse

force in the leg. The transverse force can be calculated using a modified variant of

formula 6.70 from SS-EN 1993-1-1. (The results from the original formula is on the

uncertain side.) As the formula also takes into account the transverse force caused

by the initial curvature, it is possible to disregard the transverse force supplement

referred to in SS-EN 50341, section 7.7.4.2.

L

MMMV

I

Ed

I

EdEdEd

4

An explanation and, where applicable, formulae for the variables in the formulae

above can be found in SS-EN 1993-1-1, section 6.4.

Dimensioning of guys

According to SS-EN 50341-2-18, section 7.7.4.1, the dimensioning value for a guy is

2

,

,

M

gke

gd

FF

gkegke FKF ,,

where

Fke,g reduced guy capacity

γM2 partial coefficient for a guy. 1.4 for tangent supports and 1.55 for

angle supports and end supports (guys under permanent load).

Fk,g breaking load for guys according to SS 424 08 06

Ke loss factor that can be set to 0.9 for wedged guy anchor clamps that

meet the requirements specified in SS-EN 50341-2-18, section

7.7.4.1.

6.2.2 Tubular steel support

Tubular steel supports are calculated according to SS-EN 50341, section 7.4 and

Annex K.

Tubular steel supports must be calculated using a second-order theory.

6.2.3 Wooden poles

Wooden poles are dimensioned according to SS-EN 50341, section 7.5.

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7 Requirement during design and drawing execution

7.1 General rules for execution of steel support parts

7.1.1 Internal corners

Internal corners in steel parts must be rounded with a radius of at least 5 mm.

7.1.2 Stress relieving anneal

Welded parts of a complicated shape and thicker plates with thermally cut surfaces

must undergo stress relieving anneal treatment. Requirements for stress relieving

anneal treatment shall be specified in drawings in each individual case.

7.1.3 Welded structures to be hot-dip galvanized

Structures must be designed to facilitate hot-dip galvanising. Cavities and pockets

must be drained properly so that the zinc can run off properly and not form thick

accumulations. See also EN ISO 14713-2. Pockets and gaps, which can constitute

acid pores in connection with hot-dip galvanising, must be sealed with stringer

beads. The area of a welded surface should be no larger than 7000 mm².

7.1.4 Attachment of articulated support leg

Supports with articulated attachment between support legs and crossarm (hinge

joints) must be designed with a joint made up of an intermediate plate and two

plates on the outside, with a single bolt as a hinge. The hinge bolt must be secured

with two centre punch marks and a split pin through the bolt outside the nut.

7.2 Bolted joints Bolts for supports must be hexagon bolts with a metric coarse thread, minimum

size M12. Bolt joints must be provided with washers beneath nuts. Bolts, nuts and

washers must be hot-dip galvanised according to EN ISO 10684.

When setting up equipment designed for bolts smaller than M12, bolts with smaller

dimensions and of types other than hexagonal bolts are permitted. It is not always

necessary to have washers under nuts in these cases.

Bolts joints in supports can be divided into two joint types: joints where the force is

mainly absorbed by shear in the bolt, and joints where the force is mainly absorbed

by tension in the bolt.

Sheared bolt joints are designed as non-pre-stressed joints according to

SS-EN 1090-2. However, for sheared bolt joints there are exceptions to the rule

that there has to be a full thread between the contact face of the nut and the

unthreaded part of the stem, as this makes it more difficult to meet the

requirement below for the thread outlet to end outside the material.

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Drawn bolt joints may be designed as both non-pre-stressed joints and pre-stressed

joints according to SS-EN 1090-2.

For both joint types, the strength grade must be 8.8 for bolts and 8 for nuts.

7.2.1 Sheared joints

In a sheared joint, the resultant for external forces acts on the bolt at an angle of

90° to the longitudinal axis of the bolt, and only shear force is brought to bear on

the bolt.

Intersections and joints in lattice support made up of angle bars as shown in Figure

6A, 7A, 7D and the left and centre pictures in Figure 7C are examples of sheared

joints.

Sheared joints must meet the requirements in EN 15048-1 and 2. Sheared joints

must be designed so that the thread outlet ends outside the material. This shall be

achieved by selecting bolts of “Svenska Kraftnät bolt SK” type according to TR05-

03-2E, 5.10. See Table 7A for extraction of type SK bolts with SKRB washers for

sheared joints. Note that this table is applicable only to sheared joints.

Alternatively, bolts according to EN ISO 4014 can be selected where the clamp

length is too long for SK bolts.

Figure 7A Sheared bolt joint

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Table 7A Clamp lengths for SK bolts in SHEARED joints

L (mm) Clamp length t (mm)

M12 M16 M20 M22 M24

30 -7

35 7-12

40 12-17 7-12

45 17-22 12-17 8-13

50 22-27 17-22 13-18 10-15

55 27-32 22-27 18-23 15-20

60 32-37 27-32 23-28 20-25 18-23

65 37-42 32-37 28-33 25-30 23-28

70 42-47 37-42 33-38 30-35 28-33

75 47-52 42-47 38-43 35-40 33-38

80 52-57 47-52 43-48 40-45 38-43

85

52-57 48-53 45-50 43-48

90

57-62 53-58 50-55 48-53

95

62-67 58-63 55-60 53-58

100

67-72 63-68 60-65 58-63

X (mm) 5-10 6-11 7-12 9-14 9-14

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Edge distances for bolt joints subject to shear must initially be selected in the range

between 1.5 times the bolt diameter and 2.0 times the bolt diameter. A shorter edge

distance can be selected for bolts that bear a small load in relation to their capacity.

In the case of bolts subject to shear with an edge distance longer than 2.0 times the

screw diameter, longer edge distances must generally not be used in the bolt

calculation.

7.2.2 Drawn joints

The definition of a drawn joint is that the force resultant against the longitudinal

axis of the bolt with less than 90°. A drawn bolt joint is thus usually loaded with

shear force as well.

One example of drawn joints are end plate joints in welded supports, which are

shown in the picture on the right in Figure 7C and the examples shown in Figure

7B.

Bolts for drawn joints must either be designed as non-pre-stressed joints according

to EN 15048-1, or as pre-stressed joints according to EN 14399-3. Pre-stressed

joints can be selected in designs which are not lattice framework.

Partially threaded bolts of type “Svenska Kraftnät bolt SK”, partially threaded bolts

according to EN ISO 4014 or fully threaded bolts according to EN ISO 4017 can be

selected for non-pre-stressed joints.

Clamp lengths according to Table 7B are applicable to Svenska Kraftnät type SK

bolts with SKRB washers for drawn joints. Note that these are approximately one

thread pitch longer than the ones in Table 7A in order to meet the requirement in

SS-EN 1090-2, section 8.2.2.

Figure 7B Drawn bolt joints

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Table 7B Clamp lengths for SK screws in DRAWN joints

L (mm) Clamp length t (mm)

M12 M16 M20 M22 M24

30 4-9

35 9-14

40 14-19 9-14

45 19-24 11-16 11-16

50 24-29 19-24 16-21 13-18

55 29-34 24-29 21-26 18-23

60 34-39 29-34 26-31 23-28 22-27

65 39-44 34-39 31-36 28-33 27-32

70 44-49 39-44 36-41 33-38 32-37

75 49-54 44-49 41-46 38-43 37-42

80 54-59 49-54 46-51 43-48 42-47

85

54-59 51-56 48-53 47-52

90

59-64 56-61 53-58 52-57

95

64-69 61-66 58-63 57-62

100

69-74 66-71 63-68 62-67

X (mm) 3-8 4-9 4-9 6-11 5-10

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7.2.3 Edge distance

The edge distance for drawn screw joints should generally not be selected to be less

than 1.5 times the bolts diameter, but the distance in the case of thick plates can be

reduced to 1.25 times the bolt diameter.

7.2.4 Bolt placement in bars

In the case of angle bars with a bolt in just one flange, the bolt should be positioned

between the raised flange and the centre line of the horizontal flange. The distance

to the raised flange should permit use of a socket wrench during installation.

7.2.5 Hole diameter

The bolt hole diameter must be equal to the bolt diameter plus 1.5 mm for bolts of

sizes M12 to M24. For other bolt sizes, the diameter of the hole can be selected in

accordance with ISO 273, series medium.

7.3 Parts for lattice supports of steel

7.3.1 Bars

It is desirable for as many bars as possible in a support to be the same (equal

length, size and end cutting). Bars that are different but so similar that there is a

considerable risk of mixing them up must be avoided.

Support legs that are articulated at both ends must be provided with horizontal

joints at the ends and at framework bar joints. A horizontal joint can consist of a

rigid frame or be made up of horizontals with inner horizontal diagonals.

Intersecting diagonals must be connected at the intersection point by means of at

least one bolt.

Composite bars must have two bars at each interconnecting point if the adjoining

flange is wider than 100 mm.

The end sections for a support leg that is articulated at both ends must have

diagonals to the end plate to prevent bending in main bars due to eccentric load.

7.3.2 Bar joints

Joints in angle bars must be of joint plate type or overlap type. Joints with end

plates must be avoided for angle bars. Angle bars of different sizes (thickness) can

be joined with overlap joints, the smaller section being placed on the inside in order

to minimise eccentricity in the joint.

Joints with joint plates are preferable in the case of small differences in dimensions

or when the dimensions are the same. In the case of double shear joints, an angle

bar should be used as an inner joint plate.

The number of bolts in a joint must be the same in both flanges.

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Joint with overlaps Joint with joint plates End plate joint (round

bar)

Figure 7C Examples of various types of bar joints

7.3.3 Intersections

Intersections must be designed with as little eccentricity as possible according to

the instructions in TR05-03-1E clause 6.2.1. Furthermore, it is necessary to try to

avoid using gusset plates as far as possible, and to use as few bolts as possible.

Of the three intersections in Figure 7D, the one on the left is preferable. If a gusset

plate is required, the intersection can be designed as shown in the picture in the

middle. However, note that the bolt joint with a shim has lower capacity than the

others. The reduction in shear capacity can be determined in accordance with

SS-EN 1993-1-8, section 3.6.1, formula 3.3. The value of βp must be multiplied by

the shear capacity Fv, Rd according to SS-EN 50341, Table J.3. The shim washer

must be square, with a minimum width of three times the bolt diameter.

The intersection on the right has little eccentricity and full capacity for the bolt

joints. However, it requires more material and takes longer to install than the other

two. Moreover, the gusset plate is required to be of the same thickness as the

framework bar so that it can be considered to be “continuous” according to

SS-EN 1993-3-1. Table G2.

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Intersection without

gusset plate

Intersection with gusset

plate and shim

Intersection with gusset

plate without shim

Figure 7D Different intersection designs

7.4 Distance from phase conductor to support The minimum distance between phase and the earth part of the support must be as

stated in SS-EN 50341, Table 5.8/SE.4.

The distance between phase and guys when there is a risk of guy burnoff and

support collapse must be as stated in SS-EN 50341, Table 5.8/SE.5.

Deflection of the support and insulator set must be taken into account. The sag

angle from the horizontal plane for conductors, and for angle supports to the

conductor’s deviation angle as well, must be taken into account.

7.5 Climbing arrangement Climbing arrangements must be designed so that it is possible to step on crossarm,

earth wire peaks, etc.

The climbing arrangement must begin approximately 2.5 m above ground level.

Table 7C Distance to vicinity area

System voltage

(kV)

Distance in air to the outer boundary of the vicinity area

(m)

220 3.0

400 4.3

Climbing arrangements must be positioned so that there is no risk of entering the

vicinity area according to Table 7C when climbing. If it is not possible to maintain

the distance to the vicinity area when climbing externally, it must be possible for

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climbing to take place inside the support leg. Entries and exits must be marked

with signs according to 7.9.8.

Supports with multiple support legs in which moving between the support legs via

the crossarm is permitted are provided with foot steps in one leg up to the

crossarm, and at all earth wire peaks from the crossarm.

Supports with multiple support legs in which moving between the support legs via

the crossarm is not permitted are provided with foot steps in all legs.

The foot steps should be 250-400 mm high, and they must be constant in each

support section as far as possible.

Foot steps must be able to withstand a load of 1.5 kN without permanent

deformation and 2.6 kN without breakage occurring during testing. The steel grade

and manufacturing method must be selected so that the breakage is ductile. Foot

steps with attachment device for fall arrest system(“grisknorr”) must meet the

requirements in EN 12951, section 7.3 with regard to dynamic strength.

Long support legs where internal climbing takes place must be provided with a

horizontal resting platform every 12 m.

Climbing arrangements in supports must take into account the fact that the

overhead earth wire may be in two different positions, in the traveller or in the

earth wire peak bracket.

Supports where climbing on foot steps is not appropriate must be provided with

ladders, resting platforms and anti-climbing guards. Resting platforms must be

located at the lower end of every ladder, and moving sideways must take place in

order to continue to climb. For long ladders, resting platforms must be provided at

least every 12 m.

In the case of the ladder nearest to the ground, the lower end of the ladder must be

provided with a resting platform and a lockable anti-climbing guard. The anti-

climbing guard must be a pivoting metal door, 2 m high that is in close contact with

the rungs of the ladder when locked.

The ladder must be 400-450 mm wide. The distance between rungs must be 250-

300 mm, and the minimum rung diameter must be 20 mm.

Ladders are designed for a load of 1.5 kN without permanent deformation and a sag

of no more than 10 mm for the entire ladder and no more than 5 mm for the rungs.

During testing, the ladder must be able to withstand a load of 2.6 kN without

breaking.

Ladders more than 3 m long must be able to withstand the above load every 3 m.

26 (30)


The attack width for ladder load is 100 mm.

Ladders must meet the requirements in EN 12951, 7.3 with regard to dynamic

strength.

Ladder attachments on supports must be able to withstand the same load as the

ladders. During testing, the ladders are fitted with the minimum number of

brackets permitted and then loaded with the above loads at a point immediately

adjacent to the ladder bracket.

Any other climbing arrangement must be submitted to the client for approval.

In some cases, a horizontal working foot step 1.6 m long may be needed at the earth

wire peak of the support. A working foot step of this type must be designed with

slide stops at the ends. Working foot steps must be able to withstand the same load

as foot step for climbing.

Angle supports with suspension sets that swing out by more than eight degrees

when the conductors are tensioned must be designed so that a ladder can be

suspended directly above the conductor clamps of the inner phase.

Supports must be designed with permanent anchor points along the climbing

arrangement and locations where linesman can stand during installation and

maintenance. These anchor points must be designed to fit climbing hooks used as

fall arrest equipment.

7.6 Insulator set and earth wire set attachment The bracket for the supported earth wire must be replaceable. The height of this

bracket must take into account the maximum sag angle of the line from the

horizontal plane, normally approximately 20 degrees.

It must be possible to attach a lifting davit for working with the earth wire.

Suspension set attachment to the crossarm must be designed so that the top centre

of deflection is as close as possible to the lower edge of the crossarm and permits

deflection perpendicular to the direction of the line.

V-set attachment to the crossarm must be designed so that the top centre of

deflection is as close as possible to the lower edge of the crossarm and permits

deflection along the direction of the line.

Tension set attachment to the crossarm must be designed so that the innermost

centre of deflection permits rotation around the vertical axis. If the bracket has only

one rotation point (e.g. a horizontal panel), the bracket must be designed so that

27 (30)


the angle to the horizontal plane corresponds to the angle of the tension set at the

attachment to the support.

Attachment to the support must be designed with a link and fork coupling as

described in Svk TR05-12E. Shackle connection is not permitted.

Adjacent to the attachment of insulator sets and earth wire sets it shall be

attachments for the working moments that requires during construction, for

example hoisting, stringing, clamping in and tension.

7.7 Guys Hazard marking consisting of yellow and black guy sleeves must be mounted on

guys above guy anchor terminal.

In the case of double guys, the minimum permitted radius of bearing for guy wires

must be as shown in Table 7D below.

Table 7D

Area of guy wire

(mm2)

Bearing radius (mm)

142 80

185 90

284 155

7.8 Control schedules A control schedule must be produced for every design. This control schedule must

be based on execution according to TR05-03-2E, the manufacturing drawings, the

detailed calculations and SS-EN 1090-2.

7.9 Plates and warning signs

7.9.1 General information

Plates and signs must be executed according to EBR manual “UNDERHÅLL

LEDNINGAR 0.4 – 420 kV”, chapter 301 K and according to the supplementary

requirements specified in this clause.

7.9.2 Warning signs

All supports must be provided with warning signs with the words “SVENSKA

KRAFTNÄT, LIVSFARLIG LEDNING, VISTAS EJ NÄRA STOLPE OCH STAG VID

ÅSKVÄDER” [SVENSKA KRAFTNÄT] in accordance with ELSÄK-FS 2008:2.

28 (30)


7.9.3 Support number plate

Each support is provided with a plate indicating the support number and line

designation and the text “SVENSKA KRAFTNÄT”.

This sign is placed on the left support leg so that it can be read looking towards the

higher support number.

7.9.4 Aircraft number plate

Aircraft number plates next to both lower and higher support numbers must be

fitted to every fifth support.

7.9.5 Aircraft warning sign

Aircraft warning signs are put up on lines that cross beneath other lines, or lines

that run parallel to higher lines located in the vicinity zone, or lines with tall

obstacles inside the vicinity zone.

7.9.6 Crossarm plates (line designation plates)

Crossarm plates shall be mounted on the three supports nearest to a substation

gantry or a junction in the line.

If the junction is located no more than five supports from the substation, crossarm

plates are set up on each support up to the junction.

7.9.7 Navigable water crossing signs

In areas where overhead lines cross shipping areas, it is necessary to get in touch

with the Swedish Maritime Administration in order to put up signs in accordance

with ELSÄK-FS 2008:2, where applicable.

7.9.8 Signs prohibiting climbing

Signs must be fitted on the support legs where there is a risk of crossing the

boundary to the electrical vicinity area when climbing.

7.9.9 Optical fibre installation sign

Supports with joint points for optical fibre must have signs with the text as stated

in Svk instructions.

8 Documentation

8.1 Drawings Drawings must meet the requirements in TR05-01 and TR08-02.

29 (30)


8.1.1 Manufacturing drawings

Manufacturing drawings must include all the information necessary for

manufacture. Designs with incomplete dimensions that require patterning in the

workshop are not permitted for new designs.

Manufacturing drawings must include reference to manufacturing instructions,

normally TR05-03-2E and information on the type of surface treatment. The zinc

thickness will also be specified if a zinc thickness other than Fe/Zn 95 is used.

If no tolerances are specified in the manufacturing drawing, general tolerances

according to TR05-03-2E, section 5.5 will apply. If tolerances are specified in a

drawing, these take precedence over general tolerances.

The manufacture drawings shall include the following information:

Provisions

Standards and Svenska kraftnät technical guideline TR.

Materials

Explanations of designations in parts lists, with reference to standards and

specifications for materials and fasteners.

Execution

Reference to the execution grade, tolerances, surface treatment, marking and

tightening, and securing for fasteners.

Inspection

Reference to the control plan

8.2 Calculations The calculation must be documented in a report that must include the following:

> The standard or standards on which the calculation is based. The name,

number and version of the standard must be specified.

> Which load assumptions have been made, e.g. conductor types, deviation

angle, initial tension, vertical and horizontal loaded length.

> An outline drawing of the designed object, with main dimensions laid out. It

must be possible to read dimensions of component parts and the main

dimensions of bolted joints from the report.

> All load cases with all loads reported, and the points/surfaces affected by the

loads.

> Reports of reaction loads at support feet for all load cases must be compiled

separately as “Loads on foundations”. The point of attack of the reaction load

under the foot plate must be described clearly.

30 (30)


> List of parts included in the design, reporting the load, dimensioning method

and degree of utilisation. For designs with a number of identical parts,

reporting on the part with the greatest load will suffice.

For calculation performed on a computer with the help of programs of finite

element type or similar, the name of the program, a general description of the

function of the program and the elements used, e.g. bar element that merely

absorbs tensile and compressive forces are reported.

For computer calculation that can be characterised as “computerised manual

calculation”, input and output data and the formulae used provide a sufficient

description.

Swedish or English must be used as the language in the calculation report.

Documents

Overhead transmission lines€¦ · SS-EN 1993-3-1 Eurocode 3: Design of steel structures – Part 3-1: Towers and masts SS-EN 1993-1-10 Design of steel structures – Part 1:10: