476

Cable Accessory Workmanship on

Extruded High Voltage Cables

Working Group

B1.22

October 2011
CABLE ACCESSORY WORKMANSHIP
ON EXTRUDED HIGH VOLTAGE
CABLES

Working Group
B1.22

Members

Kieron Leeburn (ZA) – (Convener), Laurent Bénard (FR), Eugene Bergin (IE), Bruno Fainaru (IL),
Henk Geene (NL), Ray Awad* (CA), Seung-Ik Jeon (KR), Jorgen Svahn (SE), Dario Quaggia (IT),
Gero Schroder (DE)

* The original member of the working group was Raphael Gignac.

Corresponding Members
Robert Rosevear (GB), Shoshi Katakai (JP)

Copyright © 2011
“Ownership of a CIGRE publication, whether in paper form or on electronic support only infers right of use for
personal purposes. Are prohibited, except if explicitly agreed by CIGRE, total or partial reproduction of the
publication for use other than personal and transfer to a third party; hence circulation on any intranet or other
company network is forbidden”.

Disclaimer notice
“CIGRE gives no warranty or assurance about the contents of this publication, nor does it accept any
responsibility, as to the accuracy or exhaustiveness of the information. All implied warranties and conditions
are excluded to the maximum extent permitted by law”.

ISBN: 978-2-85873-167-1

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 TABLE OF CONTENTS

1 Summary ......................................................................................................... 4
2 Introduction ...................................................................................................... 4
3 Scope .............................................................................................................. 6
3.1 Inclusions................................................................................................... 6
3.2 Exclusions ................................................................................................. 6
4 Related Literature and Terminology ................................................................ 6
5 General risks and skills .................................................................................... 8
6 Technical risks and required specific skills .................................................... 10
6.1 Conductors .............................................................................................. 10
6.1.1 Conductor preparation .......................................................................... 10
6.1.2 Compression ......................................................................................... 11
6.1.3 MIG/TIG Welding .................................................................................. 12
6.1.4 Thermit Weld ......................................................................................... 12
6.1.5 Mechanical Connection ......................................................................... 13
6.2 Insulation Preparation .............................................................................. 15
6.2.1 Straightening ......................................................................................... 15
6.2.2 Stripping of insulation screen ................................................................ 16
6.2.3 Preparing the end of the insulation screen ............................................ 18
6.2.4 Smoothening the insulation surface ...................................................... 19
6.2.5 Cleaning of insulation ............................................................................ 20
6.2.6 Shrinkage .............................................................................................. 21
6.2.7 Lubrication ............................................................................................ 21
6.3 Metallic sheath......................................................................................... 22
6.3.1 Welded Aluminium Sheath (WAS) ........................................................ 22
6.3.2 Corrugated Sheaths: Aluminium (CAS); Copper (CCS); Stainless Steel
(CSS)............................................................................................................. 25
6.3.3 Lead Sheath .......................................................................................... 28
6.3.4 Laminated sheaths: Aluminium Polyethylene Laminate (APL); Copper
Polyethylene Laminate (CPL) ........................................................................ 30
6.4 Oversheath .............................................................................................. 32
6.4.1 Case of graphite coating ....................................................................... 32
6.4.2 Case of extruded and bonded semi-conducting layer ........................... 32
6.4.3 Low Smoke, Zero Halogen, Enhanced Flame Performance Sheaths ... 32
6.5 Installation of joint electric field control components ................................ 33
6.5.1 Slip on prefabricated joint...................................................................... 34
6.5.2 Expansion joints .................................................................................... 37
6.5.3 Field Taped Joints ................................................................................. 40
6.5.4 Field Moulded Joints (Extruded or taped) ............................................. 41
6.5.5 Heatshrink sleeve joint .......................................................................... 41
6.5.6 Prefabricated composite type joint ........................................................ 42
6.5.7 Plug-in joint ........................................................................................... 43
6.5.8 Pre-moulded three piece joint ............................................................... 44
6.6 Installation of termination electric field control components ..................... 45
6.6.1 Slip-on prefabricated field control components ..................................... 45
6.6.2 Plug-in terminations .............................................................................. 45
6.6.3 Taped Terminations .............................................................................. 47
6.6.4 Heatshrink sleeve insulated terminations .............................................. 48
6.6.5 Prefabricated composite dry terminations ............................................. 48
6.7 Outer Protection of Joints ........................................................................ 49
6.7.1 Polymeric outer protection by taping and/or heatshrink tubes............... 49

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 6.7.2 Outer Protection Assembly ................................................................... 50
6.7.3 Filling compounds for joint protections (joint boxes) ............................. 51
6.8 Filling of Terminations.............................................................................. 52
6.9 Handling of Accessories .......................................................................... 53
6.9.1 Supporting of accessory........................................................................ 53
6.9.2 Lifting of accessories............................................................................. 54
6.9.3 Special bonding configurations and link box installation ....................... 56
6.9.4 Sensor connections............................................................................... 56
6.9.5 Fibre optics ........................................................................................... 57
7 Skills Assessment.......................................................................................... 58
7.1 Aspects to be tested ................................................................................ 58
7.2 Methods of qualification ........................................................................... 58
7.2.1 Theoretical ............................................................................................ 58
7.2.2 Training on the job and observation ...................................................... 58
7.2.3 Testing – Electrical & Mechanical ......................................................... 59
7.3 Certification.............................................................................................. 59
7.4 Duration of certification ............................................................................ 60
7.5 Upskilling ................................................................................................. 60
7.6 New Accessory type ................................................................................ 60
8 Set Up ........................................................................................................... 61
8.1 Organisation of jointing location............................................................... 61
8.2 Positioning of Joint .................................................................................. 61
8.3 Environmental Conditions ........................................................................ 61
8.4 Cable End Inspection .............................................................................. 61
8.5 Verification of Each Step ......................................................................... 62
8.6 Measuring of Diameters, Ovality, Concentricity, Position ........................ 62
8.7 Safety and Health .................................................................................... 62
8.8 Environmental Aspects ........................................................................... 62
8.9 Quality Insurance ..................................................................................... 62
9 Bibliography ................................................................................................... 63

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1 Summary

This brochure covers workmanship associated with the jointing and terminating of
AC land cables incorporating extruded dielectrics for the voltage range above
30kV (Um=36kV) up to 500kV (Um=550kV). This brochure is a complement of TB
177, the recommendations of which are not questioned in the document. A short
chapter covers general risks and skills, but the bulk of the document focuses on
the specific Technical Risks and the associated skills needed to mitigate these
risks. This is done for each installation phase. This Technical Brochure is not an
Instruction Manual, but rather gives guidance to the reader on which aspects
needs to be carefully considered in evaluating the execution of the work at hand.
The supplier’s Instruction Manual is considered the primary source of technical
information. A chapter on skills assessment helps the qualification of jointers.
Finally, attached appendices give samples of a certificate and QA documentation.

The brochure is intended for a broad range of readers. It is risk mitigation

focussed so the reader can develop his personal use for the document.

2 Introduction

High Voltage cable accessories are manufactured using high quality materials and
very sophisticated production equipment. Recent technical and technological
developments in the field in their design, manufacturing and testing have made it
possible to have pre moulded joints and stress cones for terminations up to 500
kV as well as cold shrink joints for up to 400 kV. One conclusion of TB 379 -
Update of service experience of Underground and Submarine cables - is that
internal failure rates of accessories, particularly on XLPE cable are higher than
other components and are of great concern. Focus on quality control during
jointing operations must be maintained.

Many utilities have adopted the “system approach” by purchasing the cables as
well as the major accessories from same supplier. Some of these utilities would
also request that the link should be installed by the supplier or by a contractor
under the supplier’s supervision in a “turn Key” fashion. The main advantage of
this approach is that the entire responsibility for the materials and workmanship is
clearly the supplier’s.

Some customers have adopted the component approach by purchasing the

cables and the accessories from different suppliers and to entrust the installation
to a third party.

In all cases, it is imperative that, the installation be carried out by qualified jointers
who follow the jointing instructions provided by the supplier.

International standards such as IEC and IEEE provide the necessary guidelines
concerning the interface between cables and accessories. However, it is highly
recommended that the responsible engineer should satisfactorily verify the
compatibility of the different components of the link.

It is of vital importance to manage the interface between the cables and the
accessories in order to reduce the potential technical risk.

4
One of the trends that have been developing in the international cable technology
is the reduction of the cable insulation thickness and the corresponding increase
of electrical stresses. This tendency is based on a better knowledge and an
improved quality of the insulating material and the extrusion process. The cables
and accessories are made under well-defined factory conditions. Their quality and
reliability are assured by adherence to well defined specifications. The
accessories, however, are mounted on site, and notwithstanding that this job is
done by skilled and trained jointers, it is often performed in more delicate and
undefined conditions than in the factory.

It is noted that most of the new HV links will be built using XLPE insulated cables.
With the imminent retirement of experienced jointers, a major shortage in this field
has been identified. There are few well structured training programmes and
accreditation processes in place in order to meet demand. Jointer skills are vital in
ensuring the reliability of the new links.

This Technical Brochure captures the state of the art of Jointing. It is considered
the Best Practice by the members of the SC B1 Study Committee as of 2009. It is
acknowledged that other practices which are not explicitly covered in this
brochure are not necessarily bad practices. Great care should be exercised and
the approach agreed where a departure from this TB is envisaged. Where
alternative techniques are detailed, no preference is intended nor implied unless
specifically mentioned.

Diagrams are provided to illustrate the concept described and should not be
interpreted literally.

Working under induced voltages or currents is not considered in this Technical

Brochure. As mentioned in section 8.7, in this case precautions have to be taken
to eliminate or minimize the risk.

Note:

For the range above 36kV, the risks associated with jointing are considered significant due to the
risk of a Medium Voltage (MV) jointing philosophy being applied to High Voltage (HV) cables.
CIGRE TB 303 indicates the qualification procedures for HV and EHV AC extruded underground
cable systems.

5
3 Scope

3.1 Inclusions

The Scope is limited to all accessories of:

• Extruded dielectric cables;

• AC cables;
• Land cables;
• HV Cables covered by IEC 60840;
• EHV Cables covered by IEC 62067;

Note:

Asymmetric joints (eg different conductor material; conductor size; insulation

thickness; …etc…) are not specifically covered as the permutations are too
numerous. Where these are encountered, each of the components should be
evaluated in terms of the Technical Risks and the required General and Specific
Skills needed.

3.2 Exclusions

The scope specifically excludes:

• After installation tests;

• Cable pulling and Laying;
• Direct Current Cables;
• Fault finding;
• Fluid Filled Cables;
• Maintenance;
• Submarine Cables;
• Superconducting Cables;
• Transition joints between Fluid Filled and Polymeric cables.

4 Related Literature and Terminology

4. 1 Related Literature

• IEC 60050 Chapter 461: electric cables.

The defined vocabulary can be assumed valid throughout this brochure except
where specific note to the contrary is made.

• CIGRE TB 177 –Accessories for HV cables with extruded insulation.

This brochure is still a valid guide to the selection of accessories.

Section 2 concerns the terminology (update of TB 89). It is adopted in its entirety
except where specific note to the contrary is made.

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• CIGRE TB 194 - Construction, La ying a nd i nstallation t echniques f or
extruded and self contained fluid filled cable systems.

• CIGRE TB 210 JTF 21/15 – Interfaces in high voltage accessories.

• AEIC CG 4-97 G uide f or i nstallation of e xtruded di electric i nsulated po wer

cable system rated 69 kV through 138 kV (2nd ed.)

• TB 379 Update of service e xperience of H V Underground and Submarine

Cable Systems (2004-2008)

4. 2 Additional terminology

• Jointing - A process referring generically to all types of assembly / mounting of

both joints and terminations. The term splicing is used in North America.

• Jointer – A person skilled in the art of Jointing. The term splicer is used in North
America.

• Due Ca re - This refers to familiarity with the specific activity, tool or material
being handled. It is intended to stress the importance of understanding and
precisely executing the work to be carried out.

• Technical Risk – An aspect, which, if not mitigated, could lead to the premature
failure of the cable and/or accessory.

• Good practices – Recommendation, based on practical experience, which can

mitigate Technical Risks.

• Work phases - Installation steps during cable workmanship of cable

accessories.

• General skills – Skills normally acquired by jointers through training / exposure

to common HV cable accessories.

• Specific skills – Skills not commonly acquired. Requires specific training.

In this brochure tables conclude the general and specific skills and technical risks
related to a work phase.

7
5 General risks and skills

The quality and performance of any new link or replaced joints and terminations
are highly dependent on the skills and competence of the jointers who need to
ensure the proper installation of these accessories under less than ideal field
conditions.

Systematic and compulsory training is required by all High Voltage jointers.

However, other basic and general skills are also important. These include:

• Sense of observation and organisation;

• Environmental and safety awareness;
• Problem solving, sometimes called "common sense";
• Ability to read and interpret drawings and instructions in the relevant
language;
• Good knowledge of materials and their physical and mechanical properties;
• Good familiarity and handling of different electric and hydraulic tools;
• Good understanding of electricity;
• Precision in taking physical measurements.

Other essential basic attributes include:

• Patience;
• Dexterity;
• Discipline;
• Sense of engagement;
• Responsibility;
• Physical fitness;
• Mental fitness.

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Table 1: General risks and required skills

Work Phase Risks General skills

Preparing the • Accidents leading to • Sense of organisation
jointing area cable or accessories and selection of proper
damage tools and equipment
• Electric shocks • Knowledge of electricity
• Traffic accidents (voltage induction,
• Collapse of joint bay or absence of voltage,
trench phasing etc.)
• Proper grounding
connections
• Familiarity with safety
and security measures
• Proper bracing
Cable • Underside cable is blind • Due care
preparation
Cable • Over heating of • Use of electric heaters
straightening insulation • Use of hydraulic
• Mechanically damaging equipment
the cable
Cable outer • Incomplete removal of • Due care
sheath graphite or
cleaning semiconductive coating
Cutting the • Cutting cable too short • Proper measurements
cable • Use of an electric saw
Preparing • Rough insulation • Proper use of sanders
cable surface leading to bad • Meticulous sanding
insulation interface between cable
and accessory
Plumbing • Local fire • Mastering the use of an
• Burns and loss of life or open flame (torch)
materials • Mastering the use of fire
extinguisher
Installing • Falling, injury • Working on scaffolding
terminations and at heights
All phases • Personal injuries • First aid help and
reanimation
Access to site • Personal injuries • Training to have the
with authorisation to work on
installation site with installation
under voltage under voltage

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6 Technical risks and required specific skills

The primary source of technical information is the instruction manual supplied by

the accessory manufacturer. The required skills listed here are generally ordered
from the conductor outwards. It should be emphasised that this is not the order of
assembly of the accessory (some components need to be “pre-parked” before the
conductor is joined as these components cannot be added later).

It is essential that the jointer be well trained in the necessary skills.

Each element below first describes the procedure and then the associated known
risks as well as the essential skill set needed.

In addition it is emphasised that adherence to the instruction manual is essential.

6.1 Conductors

6.1.1 Conductor preparation

The preparation phase includes:

• Cutting conductors according to the relevant instruction manual;
• Removing insulation using an approved tool;
• Protecting the cable from damage and metallic particles, while cutting the
conductor;
• Cleaning the insulation surface with an approved solvent, if it has been
contaminated;
• Removing tapes and powders;
• Cleaning conductor wires of fillers or coating compounds before jointing.

Figure 1 : Cable end prepared for top connector application

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6.1.2 Compression

Deep indentation, hexagonal and other techniques of crimping are considered

here.

These techniques include:

• Cleaning any enamel coating e.g. by applying heat or abrasion if applicable,
otherwise MIG/TIG welding must be adopted;
• Deforming the ferrule and conductor by deep indentation or compression. It is
suitable for both copper and aluminium conductors;
• Using an hydraulic press;
• Carefully choosing the correct dies or punch and ensuring their compatibility
with the press jaws;
• Checking the number, position and sequence of compression as it may vary
depending on the conductor size and the compression tool capability.
Aluminium conductors usually require longer ferrules and more compression
positions than copper conductors;
• Removing, any sharp edges or marks from the ferrule, after compression,
unless it is screened by a metallic shield.

Good practice includes:

• Performing a trial compression on a spare sample of the actual conductor
using a spare ferrule and the actual tools and dies available.

Figure 2 : Copper ferrule suitable

for compression

Figure 3 : Examples of presses for compression

Figure 4 : Hexagonal compression

11
 Figure 5 : Deep indentation

6.1.3 MIG/TIG Welding

This technique includes:

• Using arc welding in gas with a feed wire of copper or aluminium;
• Ensuring that the wire is appropriate to the welding machine / method;
• Cutting the conductor ends diagonally to form a V shape when placed in the
welding jig;
• Avoiding overheating of insulation during welding. Heat sinks or forced coolers
are generally applied on both sides of the exposed conductor and temperature
monitored with thermocouples;
• Removing enamel where enamelled copper wires are MIG/TIG welded, prior to
welding;
• Removing any sharp edges or marks from the connector, after welding.

Good practice includes:

• Performing trial MIG/TIG Welds on a spare sample of the actual conductor
using the actual jigs and welding equipment.

Figure 6 : MIG welding

6.1.4 Thermit Weld

Sometimes called exothermic welding or Cadweld. It uses chemical reagents in a

reusable crucible, placed above a mould specifically designed for the conductors
being welded.

This technique includes:

• Placing the correct quantity of reactants in a crucible;
• Taking care to avoid porosity and cavities in the welding mass due to any
presence of moisture or filler in the conductor;
• Carefully setting the gap between the conductors;
• Setting the crucible and mould assembly;

12
• Firing the reactants so they drop into the mould, melting the ends of the
conductors together;
• Dressing the weld. During this process, the presence of any porosity should be
noticeable.

Note: A safety and health risk is the high explosive reaction and formation of
gases that prevent this technique being used in confined areas.

Good practice includes:

• Preheating the mould to remove moisture;
• Performing a trial thermit weld on a spare sample of the actual conductor (or
connector) and the actual weld metals and moulds available.

Figure 7 : Thermit Weld

6.1.5 Mechanical Connection

This technique uses bolts to apply pressure to the underlying conductor. It can be
used on both copper and aluminium conductors. Either bolts are tightened until
they shear ensuring the correct connection force or they are tightened by a torque
wrench to a specified torque. One connector may cover multiple conductor sizes.
These connectors do not require special tools.

This technique includes:

• Tightening the bolts in sequence as prescribed by the instruction manual;
• Removing any sharp edges or marks from the connector after breaking the
head of bolts by torque;
• Filling any holes if applicable.

Good practice includes:

• Restraining the connector while applying tightening torque for small conductor
sizes.

Figure 8 & Figure 9 : Mechanical connectors with shear bolts

13
Figure 10 & Figure 11: Mechanical connectors tightened with torque wrench

Table 2: Technical risks and specific skills for conductor connection

techniques covered in section 6.1

Work phase Technical Risks Specific Skills

Conductor • Contamination of • Cleaning of conductor and
preparation insulation filler removal
Compression • Wrong dies or punch • Due care
and • Wrong press
indentation
MIG/TIG • Overheating of the cable • Cleaning of conductor and
welding filler removal
• Specific MIG/TIG
WeldingTechniques
Thermit weld • Moisture • Cleaning of conductor and
• Porosity filler removal
• Overheating of the cable • Thermit Welding
insulation
• Incorrect gap
Mechanical • Bolt too deep • Due care
connection
Finishing of • Sharp edges • Due care
connectors • Depressions

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6.2 Insulation Preparation

The preparation of the cable insulation is considered to be the most critical step in
the installation of accessories on extruded cables.

6.2.1 Straightening

In general, accessories require straightness of the cable during preparation. This

can be achieved by either cold straightening or hot straightening techniques.
Cable has the tendency to bend again as a result of the elastic memory of the
insulation.

6.2.1.1 Cold Straightening

This technique includes:

• Straightening cable by bending if it has a solid Aluminium conductor. After
mechanical straightening, the cable will remain in its corrected position;
• Straightening of cables with stranded conductors by bending the cable
beyond its straight position and letting it return to a straight neutral position.

6.2.1.2 Hot straightening

This technique includes:

• Heating the insulation to the specified temperature for the specified duration;
• Cooling it down while the cable is fixed in a straight position. The temperature
and duration can vary depending on conductor size as well as, insulation
material and thickness.

Figure 12 : Hot straightening of cable while fixed in straight position

15
Table 3: Technical risks and specific skills for cable straightening
techniques covered in section 6.2.1

Work phase Technical risks Specific skills

Cold • Excessive bending • Due care
straightening

Hot • Overheating due to • Operation of heating

straightening inadequate temperature equipment
control
• Hot core is more prone
to mechanical damage

6.2.2 Stripping of insulation screen

During this step, it is essential to follow the instruction manual requirements

especially with regard to:
• prepared core diameter;
• required roundness of the cable insulation.

Methods used for removing the screen are peeling, scraping and hot stripping or a
combination of these.

6.2.2.1 Peeling

This common technique includes:

• Carefully setting the tool to minimise the loss of insulation;
• Moving the peeling tool which contains a specially shaped knife in a circular
direction to remove the screen. It is inevitable that during peeling some core
insulation will be removed too.

Good practice includes:

• Performing a peeling trial on an off-cut of the actual cable to be jointed to
check the setting of the tool.

Figure 13: Examples of peeling

tools

16
 6.2.2.2 Scraping

In most cases this technique uses glass and includes:

• Moving a fragmented, sharp piece of glass at a shallow angle over the
insulation screen, thereby removing the semiconducting layer until the cable
insulation becomes visible;
• Repeating around the circumference ensuring even removal while avoiding
flat spots, cuts and dents. The scraping method results in a minimum loss of
cable insulation, but requires great skill.

Scraping can be combined with peeling in order to reduce the installation time.

Figure 14 : Scraping by glass

6.2.2.3 Hot stripping

This can only be performed on cables with strippable screens. This technique
includes:
• Heating the insulation screen with a torch or hot air gun;
• Cutting the screen longitudinally;
• Stripping the pieces like a banana. Hot stripping is a common method for
cables with EPR insulation.

The amount of heat applied should be carefully controlled.

Table 4: Technical risks an d specific s kills for r emoving t he i nsulation

screen techniques covered in section 6.2.2

Work phase Technical risks Specific skills

Peeling • Uneven travel of the • Appropriate to insulation
peeling tool type
• Blunt tool
• Removing too much
insulation if the cable is
not completely round
Scraping • Flat spots on the • Glassing
insulation surface
• Cuts/dents in the
insulation surface
Hot stripping • Burning of cable surface • Handling the torch on
semiconducting layer

17
6.2.3 Preparing the end of the insulation screen

It is essential that the transition from the insulation screen to the cable insulation
surface is:
• Correctly tapered without depression particularly in the insulation;
• Smoothly prepared without any step;
• Within the specified dimensional tolerances.

Irregularities in this area can lead to a mismatch between field control body and
the cable insulation causing field enhancement and reduction of the interface
pressure.
The end of the insulation screen can be chamfered by means of peeling or
scraping. Peeling tools used for this purpose contain a specially angled knife. The
chamfer can also be achieved by carefully scraping with glass.

Sometimes semi-conducting paint is used to achieve a fine tapered transition.

Good practice includes:

• Checking the peeling tool settings by performing a trial on a spare piece of
cable.

Figure 15 : Chamfering of the end of the insulation screen

Table 5: Technical risks and specific sk ills for preparing the end of the
insulation screen covered in section 6.2.3

Work phase Technical risks Specific skills

Peeling • Uneven travel of the • Handling peeling tools
peeling tool
• Blunt tool
• Removing too much
insulation if the cable is
not completely round
Scraping • Cuts/dents in the • Glassing
insulation surface
Painting • Thick edge (untapered) • Due care

18
6.2.4 Smoothening the insulation surface

The quality of the interface between the cable insulation and field control body
significantly affects the reliability of the joint [ref TB 210 Cigre JTF 21/15
Interfaces in high voltage accessories].

Installation instructions should clearly indicate the cable preparation details,

including:
• The smoothing technique
• The required degree of smoothness
• Dimensional tolerances

The methods of smoothing the insulation surface include polishing, melting and a
combination of polishing and melting.

6.2.4.1 Polishing

This common technique involves circumferential sanding of the insulation to

remove grooves remaining from the peeling or scraping process. Generally
emery cloth is used with grain sizes ranging from 150 to 400 grit. For EHV
accessories, a grain size finer than 400 grit may be needed to achieve sufficient
smoothness.

Figure 16 : Polishing of the insulation

6.2.4.2 Melting

This phase achieves a smooth insulation surface by melting and deforming the
cable insulation surface.

Melting techniques include:

• Applying a heat shrinkable tube made from fluorine or silicone rubber over the
cable insulation and shrinks it to fit on the insulation surface. The temperature
of the insulation surface is then controlled to above the melting point of the
cable insulation. The smoothness of the inner surface of the tube is
transferred to the insulation surface during the application of heat;
• Applying heat directly to the surface of the insulation. This is usually done
with a hot air gun rather than a flame which could scorch the surface of the
insulation.

Flat spots in the cable surface should be avoided, as these could result in areas
of low interfacial pressure.

19
Table 6: Technical risks and specific skills for smoothening the insulation
surface covered in section 6.2.4

Work phase Technical risks Specific skills

Polishing • Surface roughness • Due care
(sanding) • Incorrect diameter
• Excessive ovality
• Eccentric core
preparation
• Flat spots on the
insulation surface
Melting • Overheating, burning • Heating technique
and deformation of cable
surface • Due care
• Damage during removal
of heat shrink tube

6.2.5 Cleaning of insulation

The cable insulation surface has to be thoroughly cleaned in order to remove any
residue left during the insulation preparation.

This is best achieved by using a lint free cloth or tissue wetted with an appropriate
cleaning fluid. Only solvents supplied with the jointing kit, or specifically defined
(full chemical name), should be used due to the risk of incompatibility.

Where semi-conducting paint has been used, be aware that the solvent can
remove the paint.

Water based cleaning fluids are strongly discouraged as they might leave
moisture or residues like soap on the surface.

Good practice includes

• Cleaning from the conductor end towards the semiconducting screen cut and
disposing of the cloth thereby preventing contamination.

Table 7: Technical risks and specific skills for cleaning the cable insulation
surface as covered in section 6.2.5

Work phase Technical risk Specific skills

Cleaning with • Wrong solvent • Due care
solvent • Too long exposure
• Dissolving of semi-
conducting paint
• Cross contamination

20
6.2.6 Shrinkage

Some insulation has stretch memory introduced into its molecular structure during
the extrusion process. When heated (during load) the insulation may revert to its
relaxed state. This shrinkage can cause a mismatch of the field control
components.

Three known methods of mitigating this risk are:

• Locking the insulation e.g. by applying a clamp over the joint connector which
grips into specially peeled grooves in the insulation;
• Pre-shrinking the insulation to ensure all potential shrinkage in the joint has
already taken place;
• Tolerating the anticipated shrinkage in the design of the joint.

Table 8 : Technical and specific skills for l imitation of t he cable i nsulation

shrinkage as covered in section 6.2.6

Work phase Technical risk Specific skills

Insulation groove • Wrong dimensions • Due care
Pre-shrinking • Overheat the insulation • Handling of equipment

6.2.7 Lubrication

Lubricants are used to relieve the friction between different surfaces (cable and
accessories) during installation. Lubricants can fill possible gaps and increase the
initial breakdown strength. It is recommended that jointers do not take advantage
of this feature, as lubricants will eventually be absorbed by the insulating
materials, resulting in reduced breakdown strength.

Lubricants used are commonly based on silicone oil or silicone grease.

The lubricant should be supplied in the jointing kit, or specified by the accessory
manufacturer to ensure compatibility with cable and accessory components.

Care should be taken to avoid contamination by pollutants sticking to the

lubricant.

Table 9: Technical risks and specific skills for lubrication phase as covered
in section 6.2.7

Work phase Technical risk Technical skill

Lubrication • Polluting of lubricated • Due care
surface

21
 6.3 Metallic sheath

The metallic sheath on cables is usually applied as a moisture barrier and

mechanical protection and/or to conduct sheath currents (inductive and capacitive)
and fault currents.

The connection between metallic sheath and accessory casing (joint shell or wiping
bell of the termination) should maintain these characteristics.

6.3.1 Welded Aluminium Sheath (WAS)

6.3.1.1 Preparation of cable sheath

This preparation phase includes:

• Cutting the welded aluminium sheath and the outer sheath perpendicular to
the cable axis;
• Taking great care to avoid damaging the underlying cable core;
• Using specifically designed tools for these operations;;
• Making longitudinal cuts to remove the sheath and facilitate the mechanical
and electrical connections to other metallic components and allowing more
room for subsequent steps.

6.3.1.2 Metallic sheath continuity

Two methods can be used to maintain the earth screen continuity:

6.3.1.2.1 Connection on outside of the aluminium sheath

.

Figure 17 : Connection on top of the aluminium sheath

This connection phase includes:

• Peeling of the non-metallic outer sheath. This is usually done by applying
heat to the outer sheath;
• Cleaning of the aluminium surface to eliminate, amongst other things, the
factory applied glue and the aluminium oxide;
• Tinning of the accessory casing which is generally in copper or aluminium;
• Connecting the WAS to the accessory casing by using the plumbing
technique (for more details see 6.3.2.2.1).

22
 6.3.1.2.2 Connection under the aluminium sheath.

Figure 18 : Connection under the aluminium sheath

This connection phase includes:

• Making longitudinal cuts of the aluminium sheath and the outer sheath;
• Opening out the aluminium sheath bonded to the outer sheath;
• Inserting a connecting piece under the aluminium sheath;
• ensure an electrical and mechanical contact between the connecting piece
and the aluminium;
• Tinning the accessory casing which is generally in copper or aluminium;
• Joining the connecting piece to the accessory casing by using the plumbing
technique (for more details see 6.3.2.2.1) or by mechanical assembly.

6.3.1.3 Additional copper wire insulation screen

Where a copper wire screen is applied in combination with the WAS, the
connection can include the following:
• Plumbing the wires into the tin wipe;
• Connecting the copper wires with the accessory casing using mechanical
means (eg lug);
• Connecting the copper wire screen of both cable ends (for joints) using
mechanical means (eg ferrule);
• Connecting the copper wires directly with the bonding cables. (This can only
be applied if the copper wire screen is rated to handle the sheath currents).

6.3.1.4 Reinforcement

Glass fibre reinforced epoxy resin may be required over the tin wipes to improve
their mechanical strength.

23
Table 10 : Technical risks and specific skills for WAS connection covered in
section 6.3.1

Work phase Technical Risks Specific Skills

Preparation of • Cutting into the • Handling of specific
cable sheath underlying layers tools for this work
Metallic • Overheating underlying • Removing the glued
screen layers outer sheath
continuity
• Weak metallic screen • Removing glue
Connection on continuity due to an
top of WAS incomplete cleaning or • Tinning and Plumbing
preparation of the Techniques
aluminium sheath
or/and the metallic • Controlling the heat of
connection before the torch
plumbing
Metallic • Faulty earth screen • Due care
screen continuity due to an
continuity improper mechanical
connection
Connection
under WAS • Damage to underlying
layers
Plumbing • Overheating the cable • Plumbing Techniques
core
• Melting of the • Controlling the heat of
aluminium sheath the torch
• Enclosing voids in the
tin wipe, which could
lead to a weak
connection
Copper wire • Poor plumbing • Plumbing technique
screen connection of the wire • Crimping techniques
screen
• Poor mechanical
connection due to
wrong dies or press
Reinforcement • Uncured resin • Resin mixing and glass-
• Faulty glass-fibre tape fibre application
application techniques

24
6.3.2 Corrugated Sheaths: Aluminium ( CAS); Copper ( CCS); Stainless
Steel (CSS)

The techniques described apply to all three types unless specifically indicated
otherwise. The corrugation can be helical or discrete ring shape.

6.3.2.1 Preparation of cable sheath

The preparation phase includes:

• Removing of the outer sheath perpendicularly to the cable axis;
• Cleaning of bitumen and other coatings;
• Removing of the oxide layer (CAS) by brushing vigorously;
• Applying tin coating to a section of the corrugated sheath using the
appropriate flux;
• Removing of the corrugated sheath at the tinned section and rounding the
remaining edge.

Note: On CSS, longitudinal cutting is not recommended due to the hardness of

the stainless steel. One method of preparation is to drill a hole on a crest of the
corrugation and insert a special cutter in the hole. The sheath is cut along the
helical crest. After completion of one revolution, the trough is cut by special
scissors.

Good practice includes:

• Cutting the metallic sheath on the crest of the corrugations.

Figure 19: Preparation of cable sheath

6.3.2.2 Metallic screen continuity

Two common methods used to make electrical connection onto corrugated

sheaths are Plumbing and Soldering.

6.3.2.2.1 Plumbing

This technique includes:

• Applying a special tin alloy under heat to the surface of CAS;

25
 • Applying plumbing grease as a soldering flux, while heat is applied with a
torch;
• Deforming, compacting and smoothening the tin alloy by means of wiping;
• Building up the valleys to provide a flat surface (platform) for making
earthing connections easier;
• Joining the connecting piece using similar plumbing techniques. These
connection pieces can be solid or flexible.

Good practice includes:

• Leaving as much metallic sheath on the cable as possible to act as a heat
sink during the plumbing process as well as protecting the underlying layers
from splatter during the wiping process;
• Moving the torch circumferentially to ensure even heat distribution;
• Applying generous amount of tallow will keep the area of the wipe cool.

Note: Making a good, solid and smooth tin wipe, requires specific skills from the
jointers. Jointers that have been used to work with fluid filled accessories should
have the required specific skills.

6.3.2.2.2 Soldering

Where the connecting piece is braided tinned copper, this technique includes:
• Tinning the surface of the sheath using the appropriate flux;
• Fastening the braid to the tinned sheath using tinned copper binding wire;
• Soldering the braid and binding wire to the tinned aluminium (copper)
sheath;
• Repeating the above on the joint or termination casing as appropriate.

6.3.2.3 Additional copper wire insulation screen

Where a copper wire screen is applied (specifically for CSS), the connection can
include the following:
• Plumbing the wires into the tin wipe;
• Connecting the copper wires with the accessory casing using mechanical
means (eg lug);
• Connecting the copper wire screen of both cable ends (for joints) using
mechanical means (eg ferrule);
• Connecting the copper wires directly with the bonding cables. (This can only
be applied if the copper wire screen is rated to handle the sheath currents).

Good practice includes:

• Leaving as much metallic sheath on the cable as possible to act as a heat
sink during the plumbing process as well as protecting the underlying layers
from splatter during the wiping process;
• Moving the torch circumferentially to ensure even heat distribution;
• Applying generous amount of tallow will keep the area of the wipe cool;
• Cutting the metallic sheath on the crest of the corrugations.

6.3.2.4 Reinforcement

Glass fibre reinforced epoxy resin may be required over the tin wipes to improve
their mechanical strength.

26
Table 11: Technical risks and specific skills for Corrugated Sheath
connections covered in section 6.3.2

Work phase Technical Risks Specific skills

General • Connecting cable • Know risks and function
screens where not of screen connections
intended
Cable • Overheating the cable • Controlling the heat of
Preparation core during oversheath the torch
removal
• Cutting into underlying • Handling of specific
layers tools for this work
Tinning • Use of wrong metal • Tinning Techniques
• Lack of brushing into
valleys • Controlling the heat of
• Uneven circumferential the torch
heat (dry joint)
• Excessive heat
damaging underlying
layers
• Accidental oxidization of
surface by touching or
other material
contamination
• Use of wrong gas
Platform Wipe • Use of wrong metal • Due care
(CAS) • Excessive heat • Plumbing Techniques
damaging underlying
layers
• Wipe exceeds tinned
area
• Use of wrong gas
Copper wire • Poor plumbing • Plumbing techniques
screen (CSS) connection of the wire • Crimping techniques
screen.
• Poor mechanical
connection due to
wrong dies or press
• Weak metallic screen • Tinning and Plumbing
Connection continuity due to a bad Techniques
cleaning or preparation
of the aluminium sheath
or/and the metallic
connection before
plumbing
Cutting of • Cutting into underlying • Handling of specific
metallic layers tools for this work
sheath
Braided tinned • Wrong flux • Soldering Techniques
copper • Overheating underlying
soldering layers • Due care
• Insufficient braided
copper pieces

27
 Work phase Technical Risks Specific skills
Reinforcement • Uncured resin • Resin mixing and glass-
• Faulty glass-fibre tape fibre application
application techniques

6.3.3 Lead Sheath

6.3.3.1 Preparation of cable sheath

This preparation phase includes:

• Cutting the lead sheath taking great care to avoid damaging the underlying
cable core. A safe method is to make one shallow (partial) circumferential cut
and two shallow longitudinal cuts toward the end. A tool specifically designed
for this operation should be used;
• Tearing the lead strip between the longitudinal cuts;
• Tearing the sheath along the circumferential cut.

6.3.3.2 Metallic screen continuity

Plumbing (see 6.3.2.2.1) is the most common method for connecting the lead
sheath with the accessory casing.

6.3.3.3 Additional copper wire insulation screen

Where a copper wire screen is applied in combination with the lead, the
connection can include the following:
• Plumbing the wires in the tin wipe;
• Connecting the copper wires with the accessory casing using mechanical
means (e.g. lug);
• Connecting the copper wire screen of both cable ends (for joints) using
mechanical means (e.g. ferrule);
• Connecting the copper wires directly with the bonding cables. (This can only
be applied if the copper wire screen is rated to handle the sheath currents).

6.3.3.4 Reinforcement

Glass fibre reinforced epoxy resin may be required over the tin wipes to improve
their mechanical strength.

28
Table 12 : Technical risks and specific skills for lead sheath connection
covered in section 6.3.3

Work phase Technical Risks Specific skills

Cable • Overheating the cable • Controlling the heat of
Preparation core during oversheath the torch
removal
• Handling of specific
tools for this work
Cutting of lead • Cutting into the cable • Handling of specific
sheath core tools for this work
Plumbing • Overheating the cable • Plumbing Techniques
core
• Melting of the lead • Controlling the heat of
sheath the torch
• Enclosing voids in the tin
wipe, which could lead
to a weak connection
Copper wire • Poor plumbing • Plumbing techniques
screen connection of the wire • Crimping techniques
screen.
• Poor mechanical
connection due to wrong
dies or press
Reinforcement • Uncured resin • Resin mixing and glass-
• Faulty glass-fibre tape fibre application
application techniques

29
6.3.4 Laminated sheaths: Aluminium Polyethylene Laminate (APL); Copper
Polyethylene Laminate (CPL)

6.3.4.1 Preparation of cable sheath

This preparation phase includes:

• Carefully applying heat;
• Scraping until a clean surface is achieved.

6.3.4.2 Metallic screen continuity

This connection phase can include:

• Connecting the APL/CPL layer directly to the accessories with a roll spring, or
• Folding the aluminium (APL) or copper (CPL) back over the spring and
applying an additional external connection. Sometimes an additional copper
fabric tape is used under the contact spring on either side. Folding back
requires multiple longitudinal cuts before bending outwards to ensure there is
a clean aluminium surface facing outwards. Where a semiconducting coating
is bonded to the inside of the APL this will need to be removed as well to
ensure a good contact.

CPL also allows for:

• Plumbing, which makes it possible to establish a metal enclosed, moisture
proof connection between the cable sheath and the accessory casing. Great
care has to be taken when applying the heat for plumbing;
• Soldering with a soldering iron which is usually preferred. However this can
be achieved only if an additional tinned copper foil is used to cross the gap
between the cable sheath and the accessory casing.

Figure 20: Arranging metallic sheath continuity with a contact spring

30
 6.3.4.3 Additional copper wire insulation screen

If a copper wire screen is applied in combination with APL/CPL, it is essential to

establish an electrical contact between the copper wire screen of the cable and
the laminated aluminium/copper sheath.

This can be achieved by:

• Bending the copper wires back and clamping using a roll spring, or
• Collecting the wires together and crimping in a lug or ferrule.

Table 13: Technical risks and specific skills for laminated sheath
connections as covered in section 6.3.4

Work phase Technical risks Specific skills

Cutting the • Damaging the cable • Handling of specific
cable sheath core (cutting) tools for this work
Removing the • Overheating the cable • Controlling the heat of
PE cable core the torch
sheath by • Poor contact due to bad
heating cleaning
• Damage to thin
Aluminium / Copper
layer
Opening the • Damaging the cable • Handling of specific
Aluminium / core (cutting) tools for this work
Copper foil
Plumbing / • Excessive heat • Plumbing and soldering
soldering damaging underlying techniques
layers

31
 6.4 Oversheath

Prior to work, jointer should be aware about the cable design e.g. extruded
semiconductive layer or graphite applied on the PVC or Polyethylene oversheath.

6.4.1 Case of graphite coating

This phase includes:

• Cleaning the graphite for a specified distance from its end;
• Removing all traces of graphite using a clean cloth moistened with a suitable
solvent;
• Abrading the previously washed area using aluminium oxide tape or coarse
glass paper to ensures that the embossed lettering is completely removed. It is
essential that the serving is abraded and any graphite that may be embedded
in the extruded sheath is removed;
• Performing an appropriate resistance measurement to confirm effective
removal of any conductive layers.
.
6.4.2 Case of extruded and bonded semi-conducting layer

Removal by shaving with a spoke shave or glass slides.

• Cleaning the semi-conducting layer for a specified distance from its end;
• Performing an appropriate resistance measurement to confirm effective
removal of any conducting layer.

6.4.3 Low Smoke, Zero Halogen, Enhanced Flame Performance Sheaths

In the case of "special sheath materials", advice should be sought from the cable
manufacturer.

Table 14: T echnical risks an d sp ecific sk ills f or o versheath p reparation as

covered in section 6.4

Work phase Technical Risks Specific Skills

Cleaning or • Local overheating and • Due care
removing of the fire risk due to
conductive or incomplete cleaning
semiconducting which can lead to surface
layer currents
Removing of • Graphite concentration • Due care
the embossed
lettering

32
6.5 Installation of joint electric field control components

Check that the body is in good condition and that all surfaces (inside and outside)
are completely clean and free from defects. On joints, the accessory body is
temporarily parked on one cable core before connecting the conductor. Special
tools are generally required to guide the movement of the accessory body into the
final position and subsequently to align it correctly. The tools may include:
• Movable supports;
• Chain hoists;
• Special clamps;
• Special seals;
• Dry nitrogen;
• Lubricating grease which reduces the friction between cable core and the
accessory body. Only use the lubrication specified in the instruction manual.

Table 15: Common Technical risks and specific skills for joint field c ontrol
components as covered in section 6.5

Work phase Technical risk Specific skill

Core • Dimension/tolerance • Due care
preparation

Joint parking • Cutting or damaging the • Handling of sensitive

joint body components
• Damage to conductive
varnishes
• Selection of wrong tools
• Use of wrong tools
• Use of wrong grease

33
6.5.1 Slip on prefabricated joint

The slip on technique represents the most common way of installing field control
components. These field control components are usually made from silicon
rubber, (e.g. RTV, LSR and HTV) or EPDM and have an integrated conductive
deflector. This deflector takes over the field control at the end of the semi-
conductive insulation screen of the prepared cable core. The joint body should be
checked to ensure that it is in good condition and that all surfaces (inside and
outside) are completely clean prior to installation.

The installation phase includes:

• Lubricating the inner surface of the joint body and the cable core with grease
or other liquids specified by the manufacturer;

Figure 21: Lubrication of the joint

Figure 22: Lubrication of the cable

• Slipping the joint body on the cable core into a parking position in order to
prepare the conductor connection. It is advisable to temporarily cover the
conductor during the positioning phase;
• Checking for smoothness and cleanliness before the joint body is slipped on to
the prepared cable core;

34
 Figure 23: Joint body slipping on the cable core

• Slipping the joint body into the final position after making the conductor
connection;

Figure 24: Final position of the joint body

• Using chain hoists or other auxiliary tools to help move the joint body.

Good practice includes:

• Special movable supports are used in order to guide the movement of the
accessory body;
• Chain hoists with suitably auxiliary slip-on rings might be used in order to pull
the accessory body;
• The use of reference marks on the cable core to ensure correct positioning of
the joint body;
• Check the correct position of the accessory body which should be in
accordance with the instruction manuals.During positioning the accessory
body, any slight bulging of the body caused by the pulling process may in
some cases be smoothed out by slightly turning the body on the cable;
• Temporary cover on cable conductor to ensure that the joint body is not
damaged during parking;
• Ensuring that instructions are followed where a specific installation tool is to be
used for locating the accessory body.

35
Table 16: Technical risks and specific sk ills f or t he “ slip-on” prefabricated
joint installation as covered in section 6.5.1

Work phase Technical risk Specific skills

Accessory • Any damage or cutting • Due care
pulling into the body
Preparation • Wrong joint body • Due care
• Mis-alignment of the • Cleaning with specified
cable solvents and the correct
• Contamination of use of grease
components prior to
slide on
• Incorrect application of
lubrication
• Wrong preparation
dimensions
Parking • Damage while • Due care
positioning in parking
position due to sharp
edges of the conductor
Slipping on • Incorrect positioning of • Due care
joint body • Awareness of the
• Damage by use of chain behaviour of accessory
hoists bodies with different
• Damage of joint body sizes during movement
and/or cable core due to on the cable core
use of wrong tools • Application of formulas
• Damage due to or graphs for calculating
improper fixation of the the premoulded body
accessory body position respect to
• Damage to semi- reference marks made
conductive paint on the cable
• Handling of specific
tools

36
6.5.2 Expansion joints

Cold-shrink pre-moulded bodies are expanded either in the factory or on site.

In the case of factory expanded joints, no expansion is required on site. All that
has to be checked is that the joint has not exceeded its expiry date.

Site expanded joints have to be expanded onto a carrier tube in the field, just
before fitting them on the cable. Particular skills and tools are required for making
a field expanded joint or termination. The tools vary with each manufacturer and
the jointer must be trained in their use.

The jointer should ensure that the expanded body is positioned correctly as
specified by the manufacturer.

Field expansion steps:

a) Environmental aspects include :

• Checking to ensure that accessory components and expansion tools are in
good conditions, perfectly clean and free of defects;
• Carrying out expansion in a protected (dust-free environment in order to avoid
having impurities trapped between the carrier tube and the pre-moulded body);
• Ensuring that ambient temperature and humidity are in accordance with
manufacturer instructions.

Figure 25: Joint body expansion onto a smooth carrier tube

37
b) Lubrication:
• Applying the specified quantity and type of lubricating oil/grease on the carrier
tube and/or inside the body before starting the field expansion operation;
• Applying lubrication, if specified, to the surface of cable insulation where the
body will be positioned.

Figure 26: Example of lubrication and fitting of a smooth carrier tube for a
stress cone and a joint body

For both factory and field expanded joints:

a) Positioning on the cable.

The expanded body must be initially parked over the cable during the
conductor jointing operations. The body can remain expanded only for the
time specified by the manufacturer according to the material characteristics
and the expansion rate. Then it will be moved and positioned to the final
position and the carrier tube removed.

b) Shrinking on the cable.

According to the different design of carrier tubes (i.e. helical tube or smooth
one- the tube can be removed by hand or by a specific tool).

Figure 27: Removal of helical carrier tube from the joint body

38
 Figure 28 a : Removal of smooth carrier tube from joint

Figure 29 b : Cutting of tube from cable core

Table 17: Technical risks and specific skills for field expansion of
premoulded body as covered in section 6.5.2

Work phase Technical risks Specific skills

General • The risks listed under • The skills listed under

table 6.5.1 apply here table 6.5.1 apply here
Expansion of • Presence of defects on • Due care
the body the carrier tube (e.g.
sharp edges or cracks)
• Presence of defects on
the expansion tooling
(e.g. damaged nose)

Carrier tube • Breaking of the carrier • Ability to correctly

removal tube during removal remove the carrier tube.
• Damage to the cable Knowledge about
insulation handling the special
tools required for the
removal of the smooth
carrier tube
• Handling of special tools
and equipment

39
6.5.3 Field Taped Joints

These cable accessories are formed by applying an insulating tape on suitably

prepared cable ends in the field (installation site). Fusing is only effective if the
tapes are stretched by the correct amount. The taping can be done manually or
with the help of a machine. Taping by the machine achieves a higher quality
and/or performance of the joint.

Field taped joints include:

• Self-fusing (or self-amalgamating) rubber tape, which is usually made of EPR;
• Semi-conductive self-fusing rubber tape;
• Lead tape or copper braid;
• PVC tape;
• Waterproofing rubber tape;
• High permittivity field grading tape (if required), etc...

Some tapes are impregnated with silicon oil to fill overlap gaps.
The taped profile and geometry forms the electrical stress control of the joint.

The taping phase includes:

• Applying the tapes at the right pace, stretch, tension;
• Ensuring that the correct profile is achieved and that air gaps and voids are
managed. Frequent measurement is required;
• Ensuring that the transition point between the taped insulation and the cable
core semi-conducting layer is correctly applied;
• When a tapping machine is used, setting the parameters as per operating and
jointing instruction manuals. These settings include tension, pitch and return
limits;
• Continuing the semiconducting layer over the joint with a semiconducting tape;
• Depending on the instruction, lead tape may be applied over the semi-
conducting tape to ensure continuity.

Figure 29 : Taped profile and geometry

40
Table 18: Technical risks and specific skills for field taped joints covered in
section 6.5.3

Work phase Technical risk Specific skills

Preparation • Contamination • Due care
• Mis-alignment of the
cable
Taping • Wrong tension during • High skill in hand taping
taping • Knowledge of setting
• Wrong stress control and operating taping
profile (diameter and machines
length) • Reading technical
• Wrong settings of taping drawings and
machine measuring

6.5.4 Field Moulded Joints (Extruded or taped)

Tape Moulded and Extrusion Moulded joints are highly specialised. These
proprietary joints are usually installed by the manufacturer and are thus not
covered here.

6.5.5 Heatshrink sleeve joint

Heatshrink insulation is commonly used in Medium Voltage cable joints and has
recently been available for some High Voltage applications.

Heatshrink preparation phase includes:

• Careful positioning of the insulation in the heat shrinkable tube;
• Taking into account dimensional changes of the tube with the application of
heat;
• Uniformly applying the heat and controlling the temperature in order to ensure
thetubes are shrunk uniformly.

Table 19: Technical risks and specific skills for heatshrink joint as covered
in section 6.5.5

Work phase Technical risk Specific skills

Shrinking • Wrong order of tube • Shrinking of thick wall
insertion tubes
• Change in positioning
during shrinking
• Uneven shrinking
• Folds in tube

41
6.5.6 Prefabricated composite type joint

This joint consists of an epoxy insulation unit in which an electrode for shielding
the electric field of the connector is embedded and the premoulded stress cones
are made of rubber. Pressure is applied at the interfaces by a compression device
which is usually comprised of metallic springs.

These joints can also be used to connect cables having different conductor cross
sections and/or different insulation thicknesses.

Assembly phase includes:

• Ensuring the straightness of the cable is within the prescribed limits given in
the instruction manual;
• Parking the joint shells, epoxy and rubber insulators;
• Lubricating the appropriate surfaces with the specified lubricant;
• Connecting the conductors with compression type connector.;
• Fixing the Epoxy insulation unit and Connector completely by fitting the HV
electrode embedded in the Epoxy insulation unit to connector;
• Fitting and compressing with the springs the premoulded stress cones against
the epoxy insulation unit
• Wiping the joint shells to the cable sheaths if applicable.

Figure 30 : Prefabricated composite joint

Table 20: Technical risks and specific skills for prefabricated composite
joint as covered in section 6.5.6

Work phase Technical risk Specific skills

Insert parts • Wrong order of inserting • Due care
parts
Setting the • Setting in wrong place • Handling of specific tools
epoxy unit • Wrong centering of the for this work
and Slide of cable to epoxy
premoulded insulation unit
stress cone • Damage to cable • Due care
insulation
Assemble the • Lack of the designed • Due care
spring unit pressure

42
6.5.7 Plug-in joint

Plug-in type joints are based on a premolded joint body, with integrated metal ring
for locking the cable ends in the joint.
The cable end preparation, i.e. installing the plugs, peeling and smoothening of
the cable insulation, require equivalent skills and tools as other premolded or
prefabricated joints. This applies also to the installation of the joint covering.

These joints can also be used to connect cables having different conductor cross
sections and/or different insulation thicknesses.

Specific tools and skills are needed to plug in the prepared cable ends. The tool
can be based on hand driven chain hoists or a hydraulically driven plug-in frame.

Figure 31 Cable plug-in tool

Table 21: Technical risks and specific skills for plug-in type joints as
covered in section 6.5.7

Work phase Technical risk Specific skills

Inspection of • Damaged plugs • Check plug and cable
cable end ends

Inserting • Mis-alignment of the • Due care

cable ends cable in case of hand
driven chain hoists

Locking of the • Not locking • Pull back check of cable

plugs

43
 6.5.8 Pre-moulded three piece joint

This joint consists of three pre-moulded parts. Two cable adapters containing the
stress control profiles and the main joint sleeve.

Assembly phase includes:

• Ensuring the straightness of the cable is within the prescribed limits;
• Parking the joint main sleeve and other outer components;
• Lubricating the appropriate surfaces with the specified lubricant
• Pushing on the cable adapters;
• Connecting the conductors including installation of corona shield;
• Pushing over the joint main sleeve.

joint main sleeve corona shield HV electrode cable adapter

stress profile

cable screen connection conductor shrinkable sleeves

connection with moisture barrier

Figure 32: Three piece joint

Table 22 : Technical risks and specific skills for pre-moulded three piece
joint as covered in section 6.5.7

Work phase Technical risk Specific skills

Parking • Wrong placing • Due care
Core • Wrong measures • Handling of specific tools
preparation • Bad surface for this work
Pushing on of • Wrong position • Due care
elastomeric
parts

See also Table 16

44
6.6 Installation of termination electric field control components

In order to successfully install terminations, the jointer must possess certain skills
and abilities. These depend on the following aspects: the technology of the
terminations, the voltage levels and the manufacturer of the cable and accessories.
The procedures and skills as detailed in section 6.5 above apply.

Installation of HV cable terminations present an additional set of challenges. As

most terminations are installed in a vertical position at a few meters from the
ground, special preparation of the work area is needed. Usually, a scaffolding
system is built around each cable (or the three cables) to facilitate access to cable
and reduce strain on the jointers. Some environmental protection against dust,
wind, rain and snow is also advisable.
Particular situations such as installation on poles, high voltage pylons and in
underground power generating station transformer vaults may require special work
area arrangement to ensure safety and ease of access.

6.6.1 Slip-on prefabricated field control components

The risks and skills as detailed in section 6.5.1 above apply

6.6.2 Plug-in terminations

Plug-in type terminations consist of a field control component usually made from
silicon rubber (e.g RTV, LSR and HTV) or EPDM, and an insulator made from
epoxy resin. This insulator represents the interface to switchgears, transformers
or bushings.

Two designs are commonly available:

• Inner Epoxy Cone - based on a rubber stress cone pushed into the epoxy
insulator, achieving the required interface pressure by means of metal springs;
• Outer Epoxy Cone - based on a rubber mould, pushed onto a conical bushing
of the epoxy insulator, achieving the interface pressure by stretching the
rubber mould.

. The cable related part is based on slip-on or plug-in technology.

In this chapter only the plug-in technology is considered.

Installation skills and risks for field control components and insulators can be
taken from 6.5.1.

In addition, the handling of the insulator has to be considered representing an

additional interface to be cleaned and prepared according to given instructions
specified by the manufacturer.

45
Table 23: Technical risks and specific skills for cone plug-in terminations as
covered in section 6.6.2

Work phase Technical risk Specific skills

Installing the • Damaging the insulator • Due care
epoxy • Unequal tightening of
insulator the bolts • Check torques

Inserting • Mis-alignment of the • Due care

cable ends cable
(with or • Damaging the cable and
without stress or stress cone
cone)
Locking of the • Not locking • Check locking
plugs (if
applicable)

Figure 33: Plug-in terminations based on inner cone and outer cone model

46
6.6.3 Taped Terminations

This kind of cable accessory is formed by taping (paper) a field control element
(taped cone) in the field (installation site). This technique includes:

• Applying impregnated papers (conductive and insulating) specified by the

manufacturer, according to the given measurements and instructions.
Alternating layers of conductive and non-conductive tapes establish a field
control element to be embedded finally in an insulator with a fluid insulation
(insulating oil e.g. silicone oil or polyisobutylene). The papers (width, length
and thickness), number of layers and profile of the taped cone are specified by
the manufacturer;
• Checking the profile several times during taping. At each time, the jointer
should estimate the final diameter and length of slope based on the diameter
of remaining tape. Usually the profile angle is smaller at the start of the slope
and increases further up;
• Applying vacuum treatment to ensure that voids included in the paper wrapped
cone will disappear;
• Heating and degassing the filling compound using special equipment in order
to remove any water and gas content. During this procedure the termination
has to be evacuated according to the given instructions. This procedure can
last several hours. During this time all values have to be controlled and
monitored;
• Avoiding contamination of the vessels and other equipment with water. The
environmental conditions (temperature, humidity, dust) should be considered
here.

Table 24: Technical risks and specific skills for taped terminations as
covered in section 6.6.3

Work phase Technical risk Specific skills

Taped • Wrong order of material • High skill in taping.
Accessories • Wrong positioning and • Operation of taping
(terminations) diameter of the equipment
specified layers as • Dealing with measuring
specified by the tools such as vernier-
manufacturer callipers
• Wrong positioning of • Read technical
conductive layers drawings well
• Lack of cleanliness and
dryness of all
components during
taping
• Inclusion of particles or
voids during taping
must be avoided
Vacuum • Improper degassing • Handling of the
treatment equipment and basic
knowledge about the
behavior of fluids and
vacuum treatment

47
6.6.4 Heatshrink sleeve insulated terminations

The risks and skills, as detailed in section 6.5.5, Heatshrink sleeve joint apply
here.

6.6.5 Prefabricated composite dry terminations

The risks and skills, as detailed in section 6.5.6, Prefabricated composite type
joint apply here.

Figure 34 : Dry type termination

48
6.7 Outer Protection of Joints

6.7.1 Polymeric outer protection by taping and/or heatshrink tubes

Heat shrink tubes allow the installation of a watertight joint without the application
of a compound filled outer protection. The heat shrink tubes are often equipped
with an internal hot-melt glue layer.

The application of tubes includes:

• Parking heat shrink tubes on one or both cable ends, prior to joint installation;
• Moving heat shrink tubes into place after inner joint components have been
applied;
• Shrinking the tubes in position;
• Avoiding excessive heat as it will lead to melting or even burning of the
material;
• Ensuring sufficient heat is applied to enable the shrinking process and melting
of the glue;
• Installing an under lying tape layer if the heat shrink is not adequate to
withstand the sheath voltage requirements. A self fusing polymeric tape is
often used for this purpose.

Alternatively, a fully taped outer sheath is possible. A special tape is needed to

establish a water tight barrier, an insulating sheath and mechanical protection at
the same time.

Table 25: T echnical risks and sp ecific sk ills f or p olymeric o uter p rotection
(taping and/or heatshrink tubes) as covered in section 6.7.1

Work phase Technical risks Specific skills

Shrinking • Burning the polymeric • Heat control
material in case of too • Taping
much heat
• Insufficient melting
of the hot-melt glue in
case of too little heat
• Folds in the tubes
• Gaps between
overlapping layers,
resulting in leaks
• Wrong amount of
tension during taping

49
6.7.2 Outer Protection Assembly

Outer protection housings (including metal protectors, coffin boxes, etc) represent
a cover for joints to be filled with compounds. They can be made from e.g. PVC,
PE, GRP (glass reinforced polyester) or ABS (acrylonitrile butadiene styrene).
They may consist of a tube (to be positioned in the correct parking position) or two
half pipes (installed after positioning of joint body). The function of the outer
protection housing is to act as a container for the filling compounds referred to in
6.7.3 below.

This assembly phase includes:

• Parking of the outer protection if applicable;
• Positioning the components according to the instruction manual;
• Sealing all interfaces and openings to the environment by means of
recommended methods and materials like silicone, putty or self amalgamating
silicone tapes;
• Filling as soon as possible to ensure no build up of moisture in the outer
protector due to humidity.

In the case where a joint is to be fixed to a support structure this should be done
before the outer protector is filled with compound.

Table 26: T echnical risks an d sp ecific sk ills f or outer pr otection a ssembly

covered in 6.7.2

Work phase Technical risks Specific skills

Outer • Poor sealing of • Due care
protection interfaces leading to loss
assembly of compound, poor
filling, etc and leading to
water penetration
• Over tightening of bolts
leading to cracking of
outer protection
• Incorrect horizontal
positioning of outer
protector leading to poor
filling

50
6.7.3 Filling compounds for joint protections (joint boxes)

The function of the filling compound is to establish a corrosion protection of the

joint body (joint shell) and cable, to improve the thermal conductivity, to avoid the
penetration of water into the joint (waterproof compound) and to ensure that the
screen interruption design is maintained. Products used for the filling include:
• Cold pouring RTV (Room Temperature Vulcanization);
• Mixed (Two component resin);
• Heated (bitumen);
• Insulating fluid or gas.

The filling phase includes:

• Preparing the work taking account of the environmental conditions such as
temperature, humidity, dust and dirt;
• Heating of the compound (if applicable);
• Mixing of the filling compound. Taking care to ensure the correct amounts of
additives are added, the mixing creates a chemical reaction and can be easily
influenced. Too little catalyst / hardener can result in under-curing. Too high
temperature can cause pre-curing in the mixing pot;
• Filling by using a pump or pouring the compound.

Good practice includes (when applicable):

• Taking a sample from each batch or joint in order to ensure that it has cured
properly;
• Considering the physical position of the joint in order to avoid air pockets;
• Not moving the joint before the compound is vulcanized or stable;
• Preventing contamination to ground and waterways.

Table 27: T echnical risks an d specific skills f or f illing c ompounds c overed

in 6.7.3

Work phase Technical risks Specific skills

• Preparation • Contamination • Due care in cleanliness
of equipment and
components
• Heating filling • Overheating of • General skills and
compound compound knowledge in handling
• Underheating of the equipment
compound
• Filling of • Insufficient hardeners or• The use of special
compounds accelerators equipment (e.g. mixer)
(joints) • Premature curing due to under clean conditions
heat • Able to check and verify
• Enclosed air pockets the correct position
• Able to check the status
of the vulcanization.
• Check of outer • Wrong order of materials • General skills and
protection • May be impossible to knowledge in handling
condition visually check the the equipment
vulcanization status
afterwards

51
6.8 Filling of Terminations

There are types of terminations that are to be filled with insulating compound,
typically they are metal enclosed GIS terminations and outdoor terminations. They
can be filled with insulating liquid or gas. For taped terminations the process is
covered in 6.6.3. In the case where the termination is to be filled with compound the
manufacturers filling instruction is to be followed; filling compound may include such
items as polybutene, silicon oil or other dielectric fluid, gas or mixed two component
resins.

The different filling compounds involves different steps, the main steps in
preparation phase includes:
• Preparing the work taking account of the environmental conditions such as
temperature, humidity, dust and dirt;
• Heating of filling compound to the correct temperature in order to facilitate filling
(if applicable);
• Evacuating the chamber (if specified);
• Mixing of components (if applicable);
• Filling by using a pump (compound or gas) or pouring the compound.

Good practice includes (when applicable):

• Taking a sample from each batch or termination in order to ensure that it has
cured properly (when applicable);
• Considering the physical position of the termination and be aware about the risk
of including air bubbles inside the chamber;
• Preventing contamination to ground and waterways.

Figure 35 : Wet type termination

52
 Table 28 : Technical risks and specific skills for filling of terminations as
covered in section 6.8

Work phase Technical risk Specific skills

Preparation • Contamination • Due care in cleanliness
of equipment and
components
Heating filling • Overheating of oil • Handling the equipment
compound • Underheating of oil
Evacuating • Not evacuated enough • Handling of equipment
chamber
Mixing of • Incorrect curing of • Mixing and handling
components compounds with A and compounds and tools
B mixing components
Filling • Water or humidity • Handling the specific
presence during filling tool or method required
• Underfilling or overfilling
• Air bubbles if the
compound is filled or
mixed improperly

6.9 Handling of Accessories

6.9.1 Supporting of accessory

The support structure design for cable and accessories should be part of the civil
engineering. This should be done prior to cable installation and should not be
improvised on site.
Jointers need to ensure that the supporting structure is installed according to
prepared drawings and/or instructions.

This assembly phase includes:

• Applying the right amount of torque to the closing screws. Too much torque
can result in deformation of the polymeric jacket, while too little torque will
reduce the friction between cable (and/or joint) with the support structure and
give inadequate support and constraint.

Flame treating the extruded polythene sheath and applying a resin impregnated
tape system, in order to mechanically reinforce the cable/accessory interface
where thermo-mechanical forces and movement might be experienced.

53
Table 29: Technical risks and specific skills for installation of supporting of
accessory covered in section 6.9.1

Work phase Technical risks Specific skills

Closing the • Applying the wrong • General skills and
clamps on the torque on the closing knowledge in handling
cable (and screws with equipment
joint)
Erecting • Steelwork modification • General skills
steelwork or the adjustment on site
may weaken the support
or cause steelwork
corrosion at a later date
Mechanical • Burning of the PE • Heating techniques
reinforcement oversheath
of accessories • Wrong resin and/or
deficient application

6.9.2 Lifting of accessories

It is sometimes necessary to lift accessories. It is necessary to lift all or part of the

terminations when fitting to the structure.

The lifting phase includes:

• Setting up the lifting equipment
• Adopting appropriate safety techniques and adherence to sling load ratings
• Securing the lifting device to the accessory taking care not to damage any
components. Supplier guidance should be adopted
• Lifting the accessory ensuring that the cable is not restrained as this may
dislodge some internal components.

54
 a) b)

Figure 36: Example of lifting of cable terminations by fixing the lifting device
in a) the cable respectively b) the upper metalwork of the termination

Table 30 : Technical risks and specific skills for lifting/moving accessory as

covered in section 6.9.2

Work phase Technical risks Specific skills

Lifting/moving • Cable damage and • General skills and
displacing the internal knowledge in handling
parts due to bending or with equipment
twisting of the cable • Operator to be trained in
• Broken insulator relevant aspect of
• Cracked Porcelain lifting/moving for
• Scratched polymeric accessory
sheds • Rigging skills

55
6.9.3 Special bonding configurations and link box installation

The jointer must have the skill to install the bonding leads (single and concentric),
the link boxes, SVLs, etc associated with the particular bonding scheme adopted
for the cable circuit. Particular attention is drawn to the removal of the conducting
layer, if supplied, on the bonding leads in order to ensure integrity of the bonding
design.

Table 31 : Technical risks and specific skills for special bonding

configurations as covered in section 6.9.3

Work phase Technical risks Specific skills

Connecting • Sheath bonding • Knowledge of bonding
bonding lead connection error design
• Disturbed seal on
bonding lead may lead • Due care
to water ingress
Filling link box • Similar risks as in 6.7.3 • General skills and as
with 6.7.3
compound
e.g. bitumen

6.9.4 Sensor connections

Many types of sensors can be installed on the cable accessories. These include:
• Temperature;
• Distributed temperate sensing;
• Pressure (leak);
• Partial discharge;
• Gas density, etc.

The kind of sensors used depends on the accessories and the requirements of
the manufacturer or the user. It should not be assumed that the HV cable jointer
automatically has the required sensor connection skills. The specific sensor
supplier should provide input on the suitable skill set needed.

Special care should be taken where insulated sheath systems are employed as
the sensors must not compromise the earth isolation.

Note, these activities can be done by a third party.

Table 32 : Technical risks and specific skills f or sensor connections as

covered in section 6.9.4

Work phase Technical risks Specific skills

Connecting • Sheath bonding • Due Care
sensors connection error
• Disturbed seal on
bonding lead may lead
to water ingress

56
6.9.5 Fibre optics

In some specific installations, cables may be installed with optical fibres, mainly
used for temperature sensing.

Fibre optic cables can be:

• Integrated in the cable ;
• Attached to the cable sheath from outside;
• Blown/pulled into a separate tube.

Usually the fibre optics have to be connected in splice boxes. Additional and very
different skills are necessary in order to make fibre optic connections. The general
handling of fibre optics has to be done very carefully.

For fibre optics integrated in the cable, the splice box is usually attached to the
cable close to the joint. It is common practice to integrate the splice box into the
coffin box or protection housing of the joint.
In order to connect the fibre optics to the splice box, one side of the cable must be
cut with an over length, taking the position of the splice box beyond the joint into
account.

When sheath interruption joints are installed (eg cross bonding), it is common to
use two splice boxes (one on each side of the joint) with an additional
intermediate fibre optic splice box made from non conductive material without any
outer metallic protection.

Table 33: Technical risks and specific skills for installation of fibre optics as
covered in section 6.9.5

Work phase Technical risks Specific skills

Handling the • Breaking the optical • Fibre splicing
optical fibre fibre • Knowledge in handling
optical fibre
Removing the • Damaging the cable • Due care
stainless steel core with the steel tube
fibre • Short circuiting of the
protection sheath interruption of
tube the joint with the steel
tube

57
7 Skills Assessment
Since education and training differs for each country, it is not appropriate to dictate
the method of assessment and certification. It is recommended that the certifying
authority, normally the accessory manufacturer, keeps an up to date record of the
jointing competencies tested and certified. The methodology of assessment should
also be stated. Where no formally structured assessment and certification is
available, the methodology described in section 7.1 to 7.6 should be used.

7.1 Aspects to be tested

Modern high voltage accessories often seem fairly simple in design e.g. pre-molded
joints. This may lead to the incorrect assumption that a jointer with a skill-set
suitable for assembling low voltage accessories can be easily up skilled to high
voltage accessories. However, very careful assembly is needed for high voltage
accessories, as these accessories will operate at very high voltage stresses and, as
a result, the margin for error in assembly is very low. Further, the impact of a
system outage is very high.

It is essential that the jointer has the skill-set appropriate to the accessory being
assembled or, if a team is assembling the accessory, then the team should have
the full skill-set between them. Of course in the latter case each jointer should be
limited to working only in his area of competency.

In order to determine the jointer’s skill-set he should be tested for relevant

competencies, as outlined in section 6 above.

There may be three levels of competence

• Apprentice (not allowed to do jointing on their own);
• Jointer (allowed to do jointing on their own);
• Supervisor (highly experienced and could train others).

7.2 Methods of qualification

It is advisable that qualification involve three elements:

• Theoretical understanding of WHY a particular aspect is important;
• Observation that a jointer has understood and executed the instructions
correctly;
• Electrical and mechanical testing of the final accessory assembly.

7.2.1 Theoretical

This test should demonstrate the jointer's basic understanding of the theoretical
aspects of the assembly processes e.g. importance of smooth surfaces,
cleanliness, avoiding nicks, etc.

7.2.2 Training on the job and observation

In this case the jointer has to demonstrate his skill-set under the supervision of a
jointing supervisor, experienced in the type of accessory being assembled and in
the skill-set required.

58
 Quality assurance checklists provide a useful tool for on the job training
verification.

The full assembly of the accessory should be developed into a check list, starting
at materials checking, jointing tent conditions, tools checking, etc – a typical
overview check list is contained in Appendix A The jointer must complete the
checklist, as he/she assembles the accessory and the jointing supervisor certifies
it is done correctly.

It is recommended that each jointer keeps a logbook of all the accessories

assembled (type and voltage class).

7.2.3 Testing – Electrical & Mechanical

Extensive testing is not always possible, because of practical reasons or is not

financially feasible. Higher voltage systems generally have higher stresses. They
also have higher consequence of failures. As the stress increases, the risk of
failure also increases. It is thus prudent to conduct as many of the following tests
as is financially or technically practical. Following the tests the accessory should
be disassembled to see if there are any problems and, if noted, the jointer should
be further trained in this area until his competency is established.

The tests proposed must considered the particular skills that jointers will use.
Some tests which can be done are HV tests, PD tests or impulse tests at specified
IEC levels.

7.3 Certification

A Jointing Supervisor or an Installation Engineer, who has suitable experience and

authority, should certify the jointer, following their completion of 7.2 above. The
Certificate should indicate:
• Voltage class applicable;
• Accessory cover;
• List of skill-sets covered;
• Mechanism used for Certification (7.2.1- 7.2.3) - if 7.2.3, give test details.

59
 7.4 Duration of certification

While it is preferable that a jointer keeps his skills up to date by having a continuous
programme of work, it is recognised that this rarely happens. Very often there can
be long breaks between periods of jointing activity and there may be a possibility
that there would be a reduction in skills. It is for this reason that the concept of a
duration attached to certification is introduced. If the jointer is regularly using his
skill-set then there is no need for re-certification. In the event that there is a
significant gap in the jointer's work programme, then the jointer may need to be re-
certified. The re-certification should take place in accordance with the relevant parts
of 7.2 and 7.3 above. The log book described in 7.2.2 above will help in the
evaluation of the need for re-certification.

7.5 Upskilling

A case may arise where a jointer has a fairly good skill-set, but needs to gain some
more skills for a new accessory to be installed that is not too different from
accessories he has previously installed. In this case it may be sufficient for the
jointer to be tested and certified for the additional skills required. We would advise
to err on the side of caution.

7.6 New Accessory type

If the jointer is required to install an accessory, with which he is not familiar, then he
should be fully trained in all of the necessary skills outlined in 6 above, tested as per
7.2 and certified as per 7.3, as appropriate, before he commences installation.

60
8 Set Up
While, not part of the accessory, set up is complimentary to the accessory, and is
thus covered here. It is recommended the steps outlined below are followed:

8.1 Organisation of jointing location

Joints are installed in different locations such as , joint bays, manholes, vaults,
tunnels, etc.

The installation crew should ensure that:

• the jointing kits are verified for contents and expiry dates where appropriate;
• the layout of the jointing space is compatible with the required dimensions to
carry out the jointing activities;
• there is adequate space available for tools and equipment as well as the joint
components;
• there is adequate electric power supply, lighting, ventilation and other necessary
services;
• safety of the personnel is assured through careful planning.

8.2 Positioning of Joint

The jointer should ensure that:

• the joint is positioned and supported in accordance with designs;
• the design instruction is followed to ensure the joint does not overheat during
operation due to incorrect depth or backfill;
• the joint should be positioned in the joint bay in such a manner that in the event
of a failure that replacement is possible without serious disruption.

Allowance should also be made for those designs that incorporate rigid joint
designs.

8.3 Environmental Conditions

The jointer should ensure that the conditions are suitable with for jointing with
respect to:
• Temperature;
• Humidity;
• Dust;
• Pollution;
• Salt.

Depending on the jointing instruction, the joint bay environmental control may vary
from a simple single skinned jointing tent with no temperature or humidity control to
a double skinned tent or jointing container with careful temperature and humidity
control.

In addition the possibility of the jointer perspiring too much must be considered.

8.4 Cable End Inspection

At the commencement of jointing, great care should be exercised to inspect the

cable pulling head and tail. They should be very carefully removed and inspected
for moisture penetration, as should the remaining cable – this can be done visually,

61
but it is best done by immersing a small sample of conductor in hot oil; if there is
moisture present then the oil will crackle. Cable should not be jointed if there is
moisture in the conductor. This should be the subject of discussions between the
Installation Company and the Client

8.5 Verification of Each Step

This should be covered in the Instruction Manual Quality Assurance checklists.

8.6 Measuring of Diameters, Ovality, Concentricity, Position

This should be covered in the Instruction Manual Quality Assurance checklists.

8.7 Safety and Health

In any jointing operation it is vital that considerable attention is paid to the safety
and health of the jointing operatives and their assistants. Amongst the items that
should be considered and precautions taken to eliminate or minimise the risk are:
• Tripping;
• Sunburn / sunstroke;
• Falling from ladder or into joint bay or other;
• Ground Subsidence;
• Electrocution/ Earthing;
• Induced voltages from parallel circuits;
• Water, drowning;
• Gas;
• Traffic;
• Attack by animals;
• Attack by people;
• Lifting/handling;
• Noise;
• Handling hazardous substances;
• EMF exposure;
• Explosion/Fire;
• Failure of parallel power circuits;
• Equipment failure;
• Inadequately trained staff and supervision;
• Compliance with local safety laws and Regulations

All of the above should be the subject of a detailed documented risk

assessment.

8.8 Environmental Aspects

In completing installation operations it is necessary to comply with all relevant local

environmental laws and regulations. In any case, the environmental impact shall be
kept as low, as is reasonably possible.

8.9 Quality Insurance

The quality insurance is treated in chapter 6 of TB 177.

62
9 Bibliography
• International Electrotechnical Commission I EC 60050 C hapter 46 1:
electric cables.
• CIGRE Technical Brochure 89 – Accessories for HV Extruded Cables

• CIGRE T echnical Brochure 177 – Accessories for HV cables with extruded

insulation.

• CIGRE Technical Brochure 194 - Construction, Laying and installation

techniques for extruded and self contained fluid filled cable systems.

• CIGRE Technical Brochure 210 JT F 21 /15 – Interfaces in high voltage

accessories.

• Association of Edison Illuminating Companies AEIC CG 4-97 Guide for

installation of extruded dielectric insulated power cable system rated 69 kV
through 138 kV (2nd ed.)

• CIGRE Technical Brochure 272 – Large Cross Sections and Composite

Screen Design

• CIGRE Technical Brochure 379 – Update of service experience of HV

Underground and Submarine Cable Systems

• CIGRE Technical Brochue 446 – Advanced Design of Metal Laminated

Coverings: Recommendations for Tests. Guide for Use Operational Feed-
Back

Appendix A Model Certificate

Appendix B QA Document

63
 APPENDIX A
MODEL CERTIFICATE

64
 CERTIFICATE
Tick off skill required from list
Basic Operational Supervisory
Has theoretical knowledge- Fully qualified jointer - Fully qualified jointer with
sufficient to help capable to make joint 5-10 years experience
Accessory; Type. voltage class/

Jointing Instruction number/date/revision no:

List below to be reorganised so that it complements specific jointing instruction
with respect to the sequence in which each operation carried out

Set Up
Organisation of jointing location
Positioning of Joint
Environmental Conditions
Cable End Inspection
Safety and Health
Check cable placed in position with correct bending radius
Check cable serving, sheath, semi-conducting layer and insulation removed in accordance with
dimensions specified in jointing instruction drawing
Check that end bell, etc are passed down the cable, before jointing commences, so that they are
available in the right position for use later in the jointing installation
Organisation of jointing location

Conductors
Construction and Procedure description
Conductor preparation
Round and Hexagonal Compression
MIG/TIG Welding
Deep indentation
Thermit Weld
Mechanical Connection

Insulation Preparation
Straightening
Stripping of semi conductive insulation screen
Preparing the end of the semi conducting insulation screen
Smoothing the insulation surface
Cleaning of insulation
Shrinkage
Lubrication

65
 CERTIFICATE
Tick off skill required from list
Basic Operational Supervisory
Has theoretical knowledge- Fully qualified jointer - Fully qualified jointer with
sufficient to help capable to make joint 5-10 years experience
Metallic sheath
Welded Aluminium Sheath
Construction and procedure description
Preparation of cable sheath
Metallic screen continuity
Copper wire screen
Corrugated Seamless Aluminium (CSA), Copper (CCS), Stainless Steel (CSS)
Plumbing
Tig Welding
Lead Sheath {highlight risks and care for cutting}
Aluminium Polyethylene Laminate (APL)
Copper Polyethylene Laminate (CPL)
Corrugated Cu
Stainless steel

Oversheath
Preparation of oversheaths
Extruded PVC
Extruded Polyethylene
Low Smoke, Zero Halogen, Enhanced Flame Performance Sheaths
Mechanical Reinforcement of Accessories

Installation of joint field control components

Slip-on of prefabricated joint field control components
Field expansion
Taped Accessories (Joints)
Field moulding Extrusion or taped
Heatshrink tube insulation.
Coldshrink tube insulation.
Prefabricated composite type joint
Prefabricated composite type termination
Polymeric outer protection by taping and/or heatshrink tubes

Outer Protection of Joints

Filling compounds (joints)
Coffin Box Assembly

Installation of termination field control components

Slip-on of prefabricated field control components and spring loading, if necessary, to ensure
pressure is maintained
Installation of plug-in types

66
 CERTIFICATE
Tick off skill required from list
Basic Operational Supervisory
Has theoretical knowledge- Fully qualified jointer - Fully qualified jointer with
sufficient to help capable to make joint 5-10 years experience
Taped Accessories (Terminations)
Heatshrink tube insulation
Fitting OD porcelain/cast resin insulator and top metal
Vacuum treatment and filling of fluid or SF 6 filled terminations

Common parts about accessory installation (joints and terminations)

Supporting of accessory
Lifting of accessories
Special bonding configurations and link box installation

Special features
Sensor connections
For terminations fitting of SF6 or fluid leak detection system
Fibre optics

Safety

Environmental Aspects

Signed By

Certifying Authority

Expiry Date

67
 CERTIFICATE FILLED IN SAMPLE
Tick off skill required from list
Basic Operational Supervisory
Has theoretical knowledge- Fully qualified jointer - Fully qualified jointer with
sufficient to help capable to make joint 5-10 years experience
Accessory; Type.voltage class/ 400kV (SF6 filled) OD sealing end (with internal
stress cone) with cu condr, lead sheath and PE serving with PD test facility

Jointing Instruction number/date/revision no: YYYYY

List below to be reorganised so that it complements specific jointing instruction
with respect to the sequence in which each operation carried out

Set Up
Organisation of jointing location required required required
Positioning of Joint required required required
Environmental Conditions required required required
Cable End Inspection required required required
Safety and Health required required required
Check cable placed in position with correct bending radius required required required
Check cable serving, sheath, semi-conducting layer and insulation removed in accordance with
dimensions specified in jointing instruction drawing required required required
Check that end bell, etc are passed down the cable, before jointing commences, so that they are
available in the right position for use later in the jointing installation required required required
Organisation of jointing location required required required

Conductors
Construction and Procedure description required required required
Conductor preparation required required required
Round and Hexagonal Compression required required required
MIG Welding
Deep indentation
Thermit Weld
Mechanical Connection

Insulation Preparation
Straightening required required
Stripping of semi conductive insulation screen required required
Preparing the end of the semi conducting insulation screen required required
Smoothing the insulation surface required required
Cleaning of insulation required required
Shrinkage required required
Lubrication required required

68
 CERTIFICATE FILLED IN SAMPLE
Tick off skill required from list
Basic Operational Supervisory
Has theoretical knowledge- Fully qualified jointer - Fully qualified jointer with
sufficient to help capable to make joint 5-10 years experience
Metallic sheath
Welded Aluminium Sheath
Construction and procedure description required required
Preparation of cable sheath required required
Metallic screen continuity
Copper wire screen
Corrugated Seamless Aluminium (CSA)
Plumbing required required
Tig Welding
Lead Sheath {highlight risks and care for cutting} required required
Aluminium Polyethylene Laminate (APL)
Copper Polyethylene Laminate (CPL)
Corrugated Cu
Stainless steel

Oversheath
Preparation of oversheaths required required required
Extruded PVC
Extruded Polyethylene required required
Low Smoke, Zero Halogen, Enhanced Flame Performance Sheaths
Mechanical Reinforcement of Accessories required required

Installation of joint field control components

Slip-on of prefabricated joint field control components
Field expansion
Taped Accessories (Joints)
Field moulding Extrusion or taped
Heatshrink tube insulation.
Coldshrink tube insulation.
Prefabricated composite type joint
Prefabricated composite type termination
Polymeric outer protection by taping and/or heatshrink tubes

Outer Protection of Joints

Filling compounds (joints)
Coffin Box Assembly

Installation of termination field control components

Slip-on of prefabricated field control components and spring loading, if necessary, to ensure
pressure is maintained required required
Installation of plug types

69
 CERTIFICATE FILLED IN SAMPLE
Tick off skill required from list
Basic Operational Supervisory
Has theoretical knowledge- Fully qualified jointer - Fully qualified jointer with
sufficient to help capable to make joint 5-10 years experience
Taped Accessories (Terminations)
Heatshrink tube insulation
Fitting OD porcelain/cast resin insulator and top metal
Vacuum treatment and filling of fluid or SF 6 filled terminations required required

Common parts about accessory installation (joints and terminations)

Supporting of accessory required required
Lifting of accessories required required
Special bonding configurations and link box installation required required

Special features
Sensor connections required to know about PD required to know about PD
For terminations fitting of SF6 or fluid leak detection system required required
Fibre optics

Safety required required required

Environmental Aspects required required required

Signed By

Certifying Authority

Expiry Date

70
 APPENDIX B
QA DOCUMENT

71
 QA DOCUMENT
Tick off skill- sets QA Requirement Value QA checked by Signed Date Any
required from list value/description jointer and ok by comments
Accessory Type/voltage class/number :
Jointing Instruction number/date/revision no:
Joint/Accessory Drawing number:
Items below to be filled in as they occur
Set Up
Organisation of jointing location
Checking that all jointing materials and consumables are on site
Checking that all jointing tools and other required equipment are on site
Positioning of Joint
Environmental Conditions
Cable End Inspection for no damage /water
Safety and Health - ensuring all risks are identified and managed
Check fully detailed jointing instruction supplied covering all items listed above and below
Check cable placed in position with correct bending radius
Check cable serving, sheath, semi-conducting layer and insulation removed in accordance
with dimensions specified in jointing instruction drawing
Check that end bell, etc are passed down the cable, before jointing commences, so that they
are available in the right position for use later in the jointing installation

Conductors
Construction and Procedure description
Conductor preparation
Round and Hexagonal Compression
MIG Welding
Deep indentation
Thermit Weld
Mechanical Connection

Insulation Preparation
Straightening
Stripping of semi conductive insulation screen
Preparing the end of the semi conducting insulation screen
Smoothing the insulation surface
Cleaning of insulation
Shrinkage
Lubrication
Metallic sheath
Welded Aluminium Sheath
Construction and procedure description
Preparation of cable sheath
Metallic screen continuity
Copper wire screen

72
 QA DOCUMENT
Tick off skill- sets QA Requirement Value QA checked by Signed Date Any
required from list value/description jointer and ok by comments
Corrugated Seamless Aluminium (CSA)
Plumbing
Tig Welding
Lead Sheath
Aluminium Polyethylene Laminate (APL)
Copper Polyethylene Laminate (CPL)
Corrugated Cu
Stainless steel

Oversheath
Preparation of oversheaths
Extruded PVC
Extruded Polyethylene
Low Smoke, Zero Halogen, Enhanced Flame Performance Sheaths
Mechanical Reinforcement of Accessories

Installation of joint field control components

Slip-on of prefabricated joint field control components
Field expansion
Taped Accessories (Joints)
High Voltage tape
High Voltage Heat-resistant tape
Field moulding Extrusion or taped
Heatshrink tube insulation.
Coldshrink tube insulation.
Prefabricated composite type joint
preparation
insert parts
sleeve compression
setting the epoxy unit and slide of premoulded insulator
assemble the spring unit
Prefabricated composite type termination
Polymeric outer protection by taping and/or heatshrink tubes
Filling compounds (joints)
Coffin Box Assembly

Installation of termination field control components

Slip-on of prefabricated field control components and spring loading, if necessary, to ensure
pressure is maintained
Installation of plug-in types
Taped Accessories (Terminations)
Heatshrink tube insulation
Fitting OD porcelain/cast resin insulator and top metal
Vacuum treatment and filling of fluid or SF6 filled terminations

Common parts about accessory installation (joints and terminations)

73
 QA DOCUMENT
Tick off skill- sets QA Requirement Value QA checked by Signed Date Any
required from list value/description jointer and ok by comments
Supporting of accessory
Lifting of accessories
Special bonding configurations and link box installation
Cleaning of final assembly

Special features
Sensor connections
For terminations fitting of SF6 or fluid leak detection system
Fibre optics

Safety
Environmental Aspects

Signature of Jointer
Signature of Supervisory Jointer

74
 QA DOCUMENT FILLED IN SAMPLE
Tick off skill- sets QA Requirement Value QA checked by Signed Date Any
required from list value/description jointer and ok by comments
Accessory; Type. voltage class/ 400kV (SF6 filled) OD sealing
end (with internal stress cone) with cu cond, lead sheath and
PE serving with PD test facility
Jointing Instruction number/date/revision no:
XXXXXX
Joint/Accessory Drawing number:
YYYYYY
Items below to be filled in as they occur
Set Up
Organisation of jointing location required description to be achieved yes yes xxxx
Checking that all jointing materials and consumables are on site required list to be achieved yes yes xxxx
Checking that all jointing tools and other required equipment are on site required list to be achieved yes yes xxxx
Positioning of Joint required dwg to be achieved yes yes xxxx
Environmental Conditions required values specified to be achieved yes yes xxxx
Cable End Inspection for no damage /water required description to be achieved yes yes xxxx
Safety and Health - ensuring all risks are identified and managed required list to be achieved yes yes xxxx
Check fully detailed jointing instruction supplied covering all items listed required description to be achieved yes yes xxxx
above and below
Check cable placed in position with correct bending radius required value to be achieved yes yes xxxx
Check cable serving, sheath, semi-conducting layer and insulation removed required values to be achieved yes yes xxxx
in accordance with dimensions specified in jointing instruction drawing
Check that end bell, etc are passed down the cable, before jointing required description to be achieved yes yes xxxx
commences, so that they are available in the right position for use later in
the jointing installation

Conductors
Construction and Procedure description required per J.I to be achieved yes yes xxxxx
Conductor preparation required per J.I to be achieved and dimensions checked yes yes xxxxx
Round and Hexagonal Compression required per J.I dimensional value to be achieved yes yes xxxxx
MIG Welding
Deep indentation
Thermit Weld
Mechanical Connection

Insulation Preparation
Straightening required per JI description of process and value to be yes yes xxxxx
achieved
Stripping of semi conductive insulation screen required per JI description of process and value to be yes yes xxxxx
achieved
Preparing the end of the semi conducting insulation screen required per JI description of process and value to be yes yes xxxxx
achieved
Smoothing the insulation surface required per JI description of process and value to be yes yes xxxxx
achieved

75
 QA DOCUMENT FILLED IN SAMPLE
Tick off skill- sets QA Requirement Value QA checked by Signed Date Any
required from list value/description jointer and ok by comments
Cleaning of insulation required per JI description of process and value to be yes yes xxxxx
achieved
Shrinkage reqiuired per JI description yes yes xxxxx
Lubrication required per JI description yes yes xxxxx
Metallic sheath
Welded Aluminium Sheath
Construction and procedure description required per JI description yes yes xxxxx
Preparation of cable sheath required per JI description of process and value to be yes yes xxxxx
achieved
Metallic screen continuity
Copper wire screen
Corrugated Seamless Aluminium (CSA)
Plumbing required per JI description yes yes xxxxx
Tig Welding
Lead Sheath required per JI description of process and value to be yes yes xxxxx
achieved
Aluminium Polyethylene Laminate (APL)
Copper Polyethylene Laminate (CPL)
Corrugated Cu
Stainless steel

Oversheath
Preparation of oversheaths required per JI description of process and value to be yes yes xxxxx
achieved
Extruded PVC
Extruded Polyethylene required per JI description of process and value to be yes yes xxxxx
achieved
Low Smoke, Zero Halogen, Enhanced Flame Performance Sheaths
Mechanical Reinforcement of Accessories

Installation of joint field control components

Slide on of prefabricated joint field control components
Field expansion
Taped Accessories (Joints)
High Voltage tape
High Voltage Heat-resistant tape
Field moulding Extrusion or taped
Heatshrink tube insulation.
Coldshrink tube insulation.
Prefabricated composite type joint
preparation
insert parts
sleeve compression
setting the epoxy unit and slide of premoulded insulator
assemble the spring unit
Prefabricated composite type termination
Polymeric outer protection by taping and/or heatshrink tubes

76
 QA DOCUMENT FILLED IN SAMPLE
Tick off skill- sets QA Requirement Value QA checked by Signed Date Any
required from list value/description jointer and ok by comments
Filling compounds (joints)
Coffin Box Assembly

Installation of termination field control components

Slide on of prefabricated field control components and spring loading, if required per JI description of process and values to be yes yes xxxxx
necessary, to ensure pressure is maintained achieved
Installation of plug types
Taped Accessories (Terminations)
Heatshrink tube insulation
Fitting OD porcelain/cast resin insulator and top metal required per JI description of process and value to be yes yes xxxxx
achieved
Vacuum treatment and filling of fluid or SF6 filled terminations required per JI description of process and value to be yes yes xxxxx
achieved

Common parts about accessory installation (joints and

terminations)
Supporting of accessory required per JI description yes yes xxxxx
Lifting of accessories required per JI description yes yes xxxxx
Special bonding configurations and link box installation required per JI description yes yes xxxxx
Cleaning of final assembly required per JI description yes yes xxxxx

Special features
Sensor connections required for PD per JI description yes yes xxxxx
detection
For terminations fitting of SF6 or fluid leak detection system required per JI description of process and value to be yes yes xxxxx
achieved
Fibre optics

Safety required general general yes yes xxxxx

Environmental Aspects required general general yes yes xxxxx

Signature of Jointer
Signature of Supervisoy Jointer

77