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560
Guidelines for Maintaining the Integrity of
XLPE Cable Accessories
Working Group
B1.29
December 2013

Guidelines for maintaining the integrity of XLPE cable accessories
1
Guidelines for Maintaining
the Integrity of XLPE
Cable Accessories
WG B1.29

2
Members
Eugene Bergin IE Convener, Caroline Bradley UK Secretary, Bart Mampaey BE, Jos Van Rossum NL,
Sverre Hvidsten NO, Maria Dolores Lopez ES, Colin Peacock AU, Patrik Wicht CH, Walter Zenger
US, Yoshitsugu Sudoh JP, Ray Awad (Martin Choquette) CA, Nirmal Singh US, Xialong Luo CN, Doc
Shun Shin KR, Frederico Adamini IT, Jonathan Beneteau FR, Eric Dorison FR, Detlef Jegust DE
Copyright © 2013
“Ownership of a CIGRÉ publication, whether in paper form or on electronic support only
infers right of use for personal purposes. Unless explicitly agreed by CIGRÉ in writing, total
or partial reproduction of the publication and/or transfer to a third party is prohibited other
than for personal use by CIGRÉ Individual Members or for use within CIGRÉ Collective
Member organisations. Circulation on any intranet or other company network is forbidden
for all persons. As an exception, CIGRÉ Collective Members are allowed to reproduce the
publication only.
Disclaimer notice
“CIGRÉ 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 : 978-2-85873-255-5

4
Guidelines for Maintaining the
Integrity of XLPE Cable
Accessories
Table of Contents Page
Executive Summary 8
1 Review Recent Experience with Failures of Outdoor and Oil Filled Terminations and Non-buried
Joints 11
1.1 Review of Literature 11
1.1.1 CIGRÉ/Jicable 11
1.1.2 Statistics 11
1.1.3 Workmanship 13
1.2. Review the Consequences of Termination Failures for Cables within Substations and
Outside. 14
1.2.1 CIGRÉ/Jicable 14
1.2.2 Statistics 14
1.2.3 Workmanship 15
1.3. Survey by B1-29 15
1.3.1 Survey on Terminations 15
1.3.2 Survey on Non- buried Joints 18
2. The Role of Improved Materials, Design, Assembly and Quality Control in Mitigating the
Effects of Termination and Non-buried Joint Failures 21

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2.1 Survey Results 21
2.1.1 Terminations
2.1.1.1 Design 21
2.1.1.2 Manufacture 22
2.1.1.3 Workmanship 22
2.1.1.4 Overvoltage 23
2.1.1.5 Weather Effects 23
2.1.1.6 Bonding Problems 23
2.1.1.7 Fluid/Gas Problems 24
2.1.1.8 Others 24
2.1.2 Non-buried Joints 24
2.1.2.1 Design 24
2.1.2.2 Manufacture 25
2.1.2.3 Workmanship 25
2.1.2.4 Overvoltage 26
2.1.2.5 Weather Effects 26
2.2 Design and Materials 26
2.2.1 Air Insulated Terminations 26
2.2.1.1 Porcelain Insulators 26
2.2.1.2 Composite or Polymeric Insulators 27
2.2.1.3 Latest Developments 29
2.2.2 GIS and Oil Immersed Terminations 31
2.2.3 Insulation Medium 31
2.2.4 Connectors 31
2.2.4.1 Compression Connector 32
2.2.4.2 Cad Welding 32
2.2.4.3 Soldered or Brazed Connector 33
2.2.4.4 MIG or TIG welded connection 33
2.2.4.5 Plug-in Connector 34
2.2.4.6 Mechanical bolted connector (shear bolts) 34
2.2.4.7 Mechanical bolted connector 34
2.2.5 Non–buried Joints 35

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2.3 Assembly 35
2.4 Quality Control 35
3. The Role of Testing (development, type, sample, routine & after-laying) and Condition
Monitoring in Minimising the Incidence or Severity of Termination and Non-buried Joint Failures 37
3.1. Testing 37
3.1.1. General 37
3.1.2. Development Testing 37
3.1.2.1 Insulators 38
3.1.2.2 Connectors 38
3.1.2.3 Filling Fluids 39
3.1.3. Prequalification Test 39
3.1.4. Type Test 39
3.1.5 Short Circuit Tests 40
3.1.6. Sample Tests 40
3.1.7. Routine Tests 40
3.1.8. Test on Filling Materials 41
3.1.9. Commissioning Tests 41
3.2. Condition Monitoring 42
4 Recommendations 44
5 Conclusions 45
Appendix 1 Terms of Reference 47
Appendix 2 Bibliography/References 49
Appendix 3 TB 476 ‘Jointer Workmanship Technical Brochure’ - Contents Pages 52
Appendix 4 Short Circuit Tests 56
Appendix 5 Condition Monitoring for Terminations and Non-buried Joints 60
Table 1 Terminations installed on XLPE cables (including PE and EPR) in the period 2001-2005 12
Table 2 Failure rates of terminations over the period 2000 to 2005 12

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Table 3 Failure rates by type of termination over the period 2000 to 2005 13
Table 4 Average repair time for cables in days 15
Table 5 Comparison of Porcelain and Composite Insulators 28
Figure 1 Failure due to poor workmanship 15
Figure 2 50kV porcelain outdoor cable termination, 17
Figure 3 Composite insulator filled with synthetic oil 27
Figure 4 Example of a 170kV composite cable termination 29
Figure 5 Example of a Self Supporting Fluidless Cable Termination 30
Figure 6 Example of a Dry Type Supported Termination 30
Figure 7 Compression connector 32
Figure 8 Examples of Cad Welding 32
F figure 9 Example of a MIG Weld 33
Figure 10 Welding of an aluminium conductor 33
Figure 11 Plug-in connector (male contact) on prepared cable end. 34
Figure 12 Example of a bolted connector 34
Figure 13 Example of non-buried joints: 145kV single core cable joints installed in a cable jointing
chamber/manhole 35
Figure 14 Salt-fog test on insulator 38
Figure 15 Tests on connectors 39
Figure 16 Type Test loop of 400kV system 40
Figure 17 On site Commissioning Test (in this set up three mobile tests sets needed simultaneously,
because of cable length) 41
Figure 18 Discharge tracks on cable PE outer serving due to a defect 42.
Figure 19 Example of condition monitoring technique: 43

8
EXECUTIVE SUMMARY
This work was motivated by the occurrence of disruptive failures of cable terminations and the
consequential risks. The original scope of the Working Group (WG) was limited to land XLPE cable
systems 110 kV and above. Although priority was given to outdoor and oil-immersed terminations, joints
that are not directly buried were also included.
The Terms of Reference are attached as Appendix 1. Following discussions within the Working Group on
the terms of reference, it was agreed that:
Bonding and earthing, including SVL failures, were, in the main, not to be included.
Any relevant learning points from PE cable accessories were to be included, although
polyethylene (PE) cables are no longer installed.
There should be no time restriction on assets covered by the survey, as the relative newness of
XLPE cable technology would naturally limit the scope.
The scope was extended to cover voltage ranges from 60kV and above, as relevant failures at
these voltage levels have also occurred and designs are similar to those being used at higher
voltages.
Priority was given to outdoor, oil-immersed and GIS terminations, but joints that are not directly
buried were also to be considered.
Those items that needed to be considered and complied with to minimise the failure rate for terminations
and non-buried joints are listed below, following detailed analysis by WG B1-29.
Development, Prequalification and Type Tests
The nature and scope of tests to be carried out when developing (new) cables and/or accessories have not
been formally standardised and it has been left up to the individual producers /manufacturers to use their
knowledge and philosophy to design such tests. However, in the early 1990’s the CIGRÉ Task Force
21.03 published comprehensive recommendations for development tests on extra high-voltage cables with
extruded dielectric, including the associated accessories.
It was recommended that development tests for accessories focus on the following aspects:
Analysis of chemical, electrical and mechanical behaviour of materials
Long-term voltage test under thermal load cycles
Impulse and/or AC step voltage tests, where appropriate, with maximum conductor temperature.
Short circuit/disruptive discharge tests
Type tests in IEC62067 and IEC 60840 focus mainly on the withstand levels of cables and accessories with
respect to a.c. or impulse stresses. They do not supply much information on the long-term behaviour of
components, as the longest voltage test in these standards is limited to 20 days or 20 cycles of heating and
cooling. The issue of long term tests (typically 1 year) is dealt with in Prequalification Tests in IEC 60840
and is to be carried out if the electrical stresses at the design voltage Uo exceed 8.0 kV/mm at the
conductor screen and 4.0 kV/mm at the insulation screen. Fluid leakage is a significant cause of
termination breakdown and this concern has to be addressed e.g. through final examination, as in IEC
62067 and 60840 standards, which states:

9
“Examination of the cable system with cable and accessories with unaided vision shall reveal no
signs of deterioration (e.g. electrical degradation, moisture ingress, leakage, corrosion or harmful
shrinkage) which could affect the system in service operation.”
Factory Quality Control (QC)
It is essential that full quality control is exercised in the manufacture and supply of terminations and joints.
This applies to all the sub-components of each accessory e.g. stress cones, jointing material,
compounds,etc. A full set of suitable tests e.g. dimensional checks, electrical tests, as appropriate, should
be established and implemented. The different components of an accessory should be packaged in such a
way as to avoid damage and moisture ingress during transport. Delicate components, such as stress
cones, should be shipped in sealed plastic containers. A detailed list of these components should be
included in each box together with a complete set of assembly instructions. Recommended handling,
storage conditions and expiry dates for any components should also be provided.
On Site Quality Control
It is essential that full quality control is exercised on site with respect to the jointing area set-up, including
the control of dust, humidity and temperature andthe use of the correct jointing tools in good condition. In
addition it is essential that suitable jointing instructions and drawings are supplied and that checks are
carried out to ensure that the proper jointing material is supplied to site, in good condition and not past it’s
expiry date. Finally a proper check-off list (inspection /test plan) should be used to make sure the jointing is
done properly and in accordance with instructions.
Jointer Certification
As the quality of cable preparation and accessory installation plays a significant part in the reliability of
XLPE accessories, it is critical that cable jointers have sufficient knowledge and training to carry out the
task. It is therefore important that jointers are continually assessed to ensure competence and to maintain a
high standard of workmanship. These training records and an up-to-date CV of previous works can be
requested for review. Jointers should have valid up-to-date certification, as contained in TB476, for the
accessory they intend to assemble.
Tools
The minimum required tools are:-
those found in a standard tool box, such as knives, screwdrivers, wrenches, spanners, etc.
specific tools for conductor jointing, insulation and semi-conducting screen preparation, installing pre-
molded stress cones, metallic sheath, screen and armour connecting, inner and oversheath finishing.
Specific tools and consumables shall be specified by the cable and accessory supplier/s.
Jointing Instructions and Drawings
Jointing instructions and drawings should be part of the quality assurance system. This is particularly
crucial where accessories and cables are supplied by different providers. It is essential that the correct and
suitable jointing instructions and drawings are used and that they are delivered with the accessory.
Site Testing
It is strongly recommended that an AC voltage test should be carried out on the insulation of the cable
system in accordance with IEC Standards.
Maintenance and Condition Monitoring
In order to reduce the likelihood of failure of a termination or a non-buried joint, an inspection and test
regime is recommended to monitor the condition of accessories. Many techniques are available to assess
the condition of XLPE cable accessories. However, these techniques vary significantly with regards to
practicality, availability of test equipment and the level of expertise required. The condition monitoring
techniques employed should generally be assessed on a case by case basis and assessed against the

10
requirements and cost of monitoring compared to the consequence of a failure. A list of the currently
available techniques is contained in Appendix 4.
In the event of oil or compound leakage or other incipient failure mechanism, a risk assessment should be
carried out and corrective action taken if necessary.
Risk Assessment
The continued use of any accessory should be based on:
Public and employee safety
The criticality of the circuit
The history of the circuit and its accessories
The potential repair time
The potential cost of an outage to complete the repair
The potential cost of an outage, if a failure occurs
Potential damage from the failure
Potential cost of the damage
Effect on reputation, licence compliance and potential for prosecution
Effectiveness of any monitoring system adopted
Availability of monitoring tools and trained personnel
The cost of monitoring
Potential for damage of the accessory due to external factors
In case of a failure in service the first step is to verify if the cable systems (cable and accessories) has
been subjected to the tests (development, prequalification, type, sample, routine), as requested by the
relevant IEC standards or CIGRE recommendations.Following that one should investgate manufacture,
delivery, installation and operation to determine the source of the fault.
In the case of new cable systems, utilities should try to adopt designs that either do not experience
disruptive discharge and/or have been tested to ensure the impact is kept to a minimum.

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Chapter 1 Review of Recent Experience with Failures of Outdoor
and Filled Terminations and Non-buried Joints
The Working Group carried out a review of published literature on the subject and also carried out a
survey of the experience of the Working Group members’ and Study Committee B1 members’.
1.1. Review of Literature
The first step taken was to review existing literature and determine what was relevant to the study of
accessory failures. It was agreed reviews should be short and take the following format:
Cause of defect
Consequence of the defect
Corrective steps taken
1.1.1, CIGRÉ, Jicable and Other Technical Literature
Nothing of particular relevance was found in the published CIGRÉ literature.
A recent paper for Jicable 2011 (A.5.4) described a failure in an XLPE cable termination installed in a
400kV GIS substation and the remedial actions taken. Another Jicable 2011 paper (A.3.7) summarised
the experiences of three European TSO's. It showed that only a small part of the total cable circuit outage
time is due to the actual repair time. More time was spent on other aspects, such as approvals to enter
the premises, arranging the proper permissions to start repair works, cleaning the area and getting the
necessary parts to site. The relevant literature is listed in Appendix 2.
1.1.2 Statistics
TB 379 ‘Update of Service Experience of HV Underground and Submarine Cable Systems’ supplied the
statistics in Table 1 below regarding XLPE terminations. There is no information in TB 379 for non-buried
joints. The table below gives an overview of the number of terminations installed on XLPE cables
(including PE and EPR) in the period 2001-2005. Later statistics are not available in a TB, but the WG
addressed this in Section 1.3 below by gathering up-to-date experience from those 14 countries that
responded to the WG survey enquiry.

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VOLTAGE
RANGE
YEAR OF
INSTALL
ATION
kV
Outdoor
Terminati
on - Fluid
filled -
Porcelain
Outdoor
Terminati
on - Fluid
filled -
Composit
e
insulator
Outdoor
Terminati
on - Dry -
Porcelain
Outdoor
Terminati
on - Dry -
Composit
e
insulator
GIS or
Transfor
mer
Terminati
on - Fluid
filled
GIS or
Transfor
mer
Terminati
on - Dry
60 to 109 2001 531 27 12 75 0 311
2002 753 15 27 69 6 296
2003 513 21 15 96 5 225
2004 483 24 24 186 2 190
2005 600 21 51 138 3 225
110 to 219 2001 267 131 159 32 116 394
2002 282 128 216 35 77 565
2003 546 163 51 83 130 447
2004 226 190 63 32 98 366
2005 187 285 162 41 106 389
220 to 314 2001 135 0 0 0 54 135
2002 63 0 0 0 30 12
2003 102 6 0 0 0 42
2004 66 9 0 0 3 27
2005 60 3 0 12 3 42
315 to 500 2001 12 0 0 0 0 0
2002 0 0 0 0 0 0
2003 0 0 0 0 0 12
2004 0 0 0 36 0 0
2005 28 12 0 0 12 0
> 500 2001 0 0 0 0 0 0
2002 0 0 0 0 0 0
2003 0 0 0 0 0 0
2004 0 0 0 0 0 0
2005 0 0 0 0 0 0
ac Accessories installed 2000 to 2005
AC ACCESSORIES
Extruded cables (EPR, PE or XLPE)
Table 1 Terminations installed on XLPE cables (including PE and EPR) in the period 2001-2005
The table below indicates the failure rates over the same time period (2000 to 2005):
60-219kV 220-500kV ALL VOLTAGES
Failure rate
[fail./yr 100 comp.]
Failure rate
Failure rate
Termination 0,0070,0320,006
0,005 0,018 0,006
FAILURE RATES BASED ON ALL REPLIES
XLPE CABLES (AC)
A. Failure Rate - Internal Origin Failures
B. Failure Rate - External Origin Failures
C. Failure Rate - All Failures
Termination
Termination 0,011 0,050 0,013
Table 2 Failure rates of terminations over the period 2000 to 2005

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Internal External Unknown
Outdoor Termination - Fluid filled - Porcelain 46226 15 0,007 0,003 0,003 0,001
Outdoor Termination - Fluid filled - Composite insulator 2619 2 0,019 0,019 0,000 0,000
Outdoor Termination - Dry - Porcelain 1954 2 0,024 0,024 0,000 0,000
Outdoor Termination - Dry - Composite insulator 1353 1 0,020 0,000 0,020 0,000
Outdoor Termination - Type not specified 0 17
Outdoor Terminations - Total 52152 37 0,015 0,007 0,006 0,002
GIS or Transformer Termination - Fluid filled 4222 0 0,000 0,000 0,000 0,000
GIS or Transformer Termination - Dry 20771 19 0,019 0,015 0,002 0,002
Outdoor Termination - Fluid filled - Porcelain 1493 5 0,075 0,030 0,045 0,000
Outdoor Termination - Fluid filled - Composite insulator 61 0 0,000 0,000 0,000 0,000
Outdoor Termination - Dry - Porcelain 0 0 0,000 0,000 0,000 0,000
Outdoor Termination - Dry - Composite insulator 53 0 0,000 0,000 0,000 0,000
Outdoor Termination - Type not specified 0 18
Outdoor Terminations - Total 1607 23 0,330 0,215 0,086 0,029
GIS or Transformer Termination - Fluid filled 2447 2 0,016 0,016 0,000 0,000
GIS or Transformer Termination - Dry 637 2 0,071 0,071 0,000 0,000
220 to 500
Extruded (XLPE,
PE or EPR)
60 to 219
Extruded (XLPE,
PE or EPR)
Total number of
faults
Failure rates
Total
failure
rate
Cause of failureVoltage range
kV
Cable type Accessory tyoe
Total number of
accessories in
2005
Table 3 Failure rates by type of termination over the period 2000 to 2005
In Table 1, for the period 2001-2005, we can see that for the HV cable systems (60 to 219kV) the use of
outdoor composite insulators is already a commonly used technology. For EHV (above 219kV) this
technology is only starting. The same findings are made with regard to the use of dry type GIS
terminations.
From Table 2 we can see that the failure rate on terminations for EHV cable systems (above 219kV) is
around 5 times higher than that for the HV cable systems (60-219kV).
Table 3 gives indicates the failure rate per type of termination and is grouped for the voltage levels 60-219
and 220-600kV. For a relatively high number of failures on terminations, the type of the terminations was
not specified. As a result, the reader must be careful when comparing the different types of terminations.
The information as shown in Tables 1 to 3 is based upon replies received by WG B1-10 to their
questionnaire. For further information regarding these statistics we refer to CIGRÉ Technical Brochure
379.
1.1.3 Workmanship
CIGRÉ Technical Brochure 476 ‘Cable Accessory Workmanship on Extruded High Voltage Cables’ was
published in October 2011. This section 1.1.3 is substantially reproduced from that Technical Brochure.
TB 476 covers workmanship associated with the jointing and terminating of AC land cables, incorporating
extruded dielectrics for the voltage range above 30kV (Um=36kV) and up to 500kV (Um=550kV). This
brochure is a complement of TB177. A short chapter covers general risks and skills, but the bulk of the
document focusses on the specific technical risks and the associated skills needed to mitigate these risks.
This is done for each phase of the installation. This Technical Brochure is not an Instruction Manual, but
rather gives guidance to the reader on which aspects need to be carefully considered in evaluating the
execution of the work at hand. High voltage cable accessories are manufactured using high quality
materials and very sophisticated production equipment. Recent technical and technological developments
in the field of their design, manufacturing and testing have made it possible to have pre-molded joints and
stress cones for terminations up to 500kV, as well as cold shrink joints up to 400 kV. One of the
conclusions of TB 476 is that internal failure rates of accessories, particularly on XLPE cable, are higher
than other components and are of great concern due the larger impact of a failure. Therefore the 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 the same supplier. Some utilities also request that the link should be installed by the
supplier or by a contractor under the supplier’s supervision in a “turnkey” 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 cables and taccessories from
different suppliers and entrusting the installation to a third party. In all cases, it is imperative that the

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installation be carried out by qualified jointers, who follow the jointing instructions provided by the
accessory supplier.
International standards such as IEC and IEEE provide the necessary guidelines concerning the interface
between cables and accessories. However, it is strongly recommended that the responsible engineer
should 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, e.g. cables
and pre-molded accessories having non-compatible diameters or other non-compatible dimensions or
characteristics.
One of the international trends in cable technology has been the reduction of the cable insulation thickness
and the corresponding increase in electrical stress. This tendency is based on better knowledge, increased
quality of the insulating material and improvements in the extrusion process. Cables and accessory
components are made under well-defined factory conditions and their quality and reliability are assured by
adherence to well defined specifications. However, the accessories are assembled on site and,
notwithstanding that this job is carried out by skilled and trained jointers, it is often performed in more
delicate and less controlled conditions than in the factory. This means that correct assembly is even more
important, because, with the increased stress level due to the reduced insulation thickness, bad
workmanship will, sooner or later, lead to a breakdown of the accessory.
It is noted that the majority of the new HV cable links being considered will use XLPE insulated cables.
TB 476 captured the state of the art of jointing and is considered the best practice internationally. 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 when departing from practices
recommended in TB 476.
While TB476 does not directly refer to failures or the consequences of failures, it is a comprehensive
document on the assembly of cable accessories. If used properly it can provide vital advice on the
avoidance of failures due to bad workmanship.
1.2. Review the Consequences of Termination Failures for Cables within
Substations and Outside.
1.2.1 CIGRÉ, Jicable and Other Technical Literature
In the case of CIGRÉ the only consequences are the repair times that are covered in 1.2.2 below.
1.2.2 Statistics
From TB 379, average repair times in days for XLPE systems are set out in the Table 4 below. This
average repair time was calculated for all the reported failures on extruded cables for the corresponding
voltage levels. No separate values were calculated for specific types of accessory.
The definition of repair time as used in the questionnaire by B1-10 is the following:
Repair time is the cumulative period of time required to mobilize resources, locate and repair the failure.
The repair time associated with a failure is of fundamental importance since the summation of repair times
is required to obtain a measure of non-availability, which from a reliability viewpoint is of greater
significance than fault rate.

15
60 to 219kV 15 days
220 to 500kV 25 days
Table 4 Average repair time for cables in days
-
1.2.3 Workmanship
TB 476 does not specifically refer to the consequences of failures, except to indicate the potential damage
in the area, the very serious transmission system consequences with potential safety implications, loss of
load, loss of customers, poor public relations and potential loss of revenue and additional costs.
Fig 1 Failure due to poor workmanship
(surface scratch due to bad workmanship)
1.3 Survey by B1-29
The Working Group compiled a survey to be completed by all members of the WG and SC B1 members,
whose country were not represented on the Working Group. The survey was split into the voltage ranges
recommended by CIGRÉ below:
50-109kV
110-219kV
220-314kV
315-500kV
Replies were received from 14 countries. Terminations and non-buried joints were dealt with separately.
The survey results may be summarised as follows:-
1.3.1 Survey on Terminations
a) A total of 61 failures were reported
b) Most of the installations were inside substations with only 6 being in a public area

16
c) The voltage range was from 51 to 400kV, with the main installations being in the 50-150kV range
d) The installation year varied from 1972 to 2010
e) The year of failure varied from 1988 to 2010
f) Most installations had commissioning tests and, in most cases, voltage tests were carried out as
part of commissioning
g) Most installations were outdoor (37)
h) The outdoor housings were generally filled with silicon oil or polybutene and the GIS (Gas
Insulated Substation) housings were mainly unfilled
i) Most AIS (Air Insulated Substations) installations had composite or polymeric outer housings – 18
had porcelain housings. However it should be noted that failures in porcelain housings are likely to
be more serious in view of the shards that are created during the fault
j) The terminations were mainly installed by a manufacturer, with only 15 being installed by a utility
or contractor
k) The conductor sizes varied from 100 to 2500 sq mm and were both copper and aluminium
l) The metallic shield varied from lead to aluminium foil to copper wires
m) In nearly all cases the cable and termination were from the same manufacturer
n) In most cases prequalification test had not been completed
o) Nearly all termination designs had undergone type tests
p) In only a few cases were maintenance test carried out – varying from a serving test, DC test and
thermovision tests
q) The pollution design ranged varied from normal to serious
r) The causes of failure were listed as:
1) Termination Design
Moisture ingress due to inadequate sealing.
Pre-molded component breakdown.
Breakdown of insulating material.
2) Manufacture
Poor adherence of pre-molded components within stress cone
Rough surface of metallic parts leading to Partial Discharge
In one case manufacture was identified, but a reason was not given.
Poor fluid quality leading to internal discharges.
3) Workmanship
Damage to primary insulation during jointing.
Poor fluid treatment prior to filling.
Poor XLPE surface preparation.

17
Poor preparation of the outer semi-conducting layer.
Copper particles between cable and stress cone.
XLPE shavings left in position between cable and stress cone.
Incorrect application of stress cone.
Cable not sufficiently straightened prior to jointing.
4) Overload
No cases reported in the returned survey results.
5) Overvoltage
Four cases due to switching/lightning surge.
6) Animals
7) Weather Effects
8) Cable Insulation Inadequacies
Two cases, no details supplied.
9) Bonding Problems
Thermal runaway due to a metal sheath being solidly bonded during installation.
This was not in accordance with the specified bonding design, which was based on
single point bonding.
Poor earth connection due to mechanical movement causing flash-over.
10) Fluid/Gas Problems
Partial discharge caused by solidifying silicon oil.
Multiple failures due to leaks of insulating oil.
Fig 2 50kV porcelain outdoor cable termination,
leaking high viscous insulating oil at bottom flange
11) External Damage /Sabotage

18
12) Others
Failure of pressure relief system, leading to loss of insulating fluid.
s) Consequences of Failure – fire, outage time, collateral damage, reputation
Most cases resulted in a disruptive failure and some collateral damage that required a
lengthy repair outage.
t) Actions Taken
1) New Design
Method for earthing of sheath improved
Change in specifications for pre-molded parts
2) New Tests
No new tests were specified in the returned surveys.
3) New Installation Specification
Improved termination fluid filling and treatment processes
Changes made to compounds used during jointing and methods for handling compounds
Suitable hold and witness points introduced during jointing
New XLPE shaping techniques implemented
Improvements made to Jointing Instructions
4) Risk Management
On-Line PD tests introduced.
Exclusion zones set up around termination, including screening walls.
5) Repair/Corrective Action
i. Changed whole joint/ termination.
ii. Changed stress cone only. All faults required some form of repair or corrective
action to be taken.
6) Preventative Action
In many cases sealing ends that were leaking insulating fluid were replaced or repaired
before an electrical failure occurred.
1.3.2 Survey on Non-buried Joints
a) 27 failures were reported: 12 of the failures in premolded joints and 11 in taped joints. The
remaining four failures being EMJ (extruded molded) or transition joints.
b) The location of the joints was generally not stated.
c) The voltage range was 50 to 314kV, but the taped joints were in the lower voltage range.
d) Core sizes varied from 400 to 2000 sq mm with both copper and aluminium conductors.
e) Most joint casings were unfilled.
f) The installations were mainly carried out by the manufacturer.

19
g) It was not clear if the joints and cables were from the same manufacturer
h) In general the joints were type tested.
i) Most joints were commissioned with DC voltage tests (both insulation and serving).
j) There was no maintenance testing before failure.
k) Many joints failed within 1-2 years of commissioning.
l) The causes of failure were attributed as follows:-
1) Joint Design
Incorrect stress cone internal diameter.
Incorrectly shaped embedded electrode.
Poor tape design.
2) Manufacture
Defective manufacture of stress cone that contained voids.
Poor quality stress cone material.
Water penetration via a crack, due to a manufacturing defect within the metallic
casing.
3) Installation
Damaged insulation during jointing.
Poor shaping of XLPE.
Voids created, due to poor shaping of insulating tapes.
Incorrect positioning of stress cones.
Cable inadequately plugged into joint body.
Metallic particle contamination.
Loss of earthing connection to screen wires, due to poor soldering.
Racking or tray system that permitted joint movement.
4) Overload
No cases of failure were attributed to overload.
5) Overvoltage
One reported case was attributed to a possible lightning strike.
6) Animals
There were no failures attributed to animals.
7) Weather Effects
In only two cases failures were attributed to weather effects, namely water
penetration. The water penetration in joints may be a design/material/workmanship
issue
8) Unknown
One case was listed as unknown.
m) Consequences of Failure

20
No consequences were provided in the survey replies.
n) Actions Taken
1) New Design
In most cases where joint design was identified as the cause of failure, the joint was
redesigned.
2) New Tests
Post-installation PD testing of joints was introduced in many cases.
3) New Installation Specification
Hold and witness points were introduced including photographic records.
New guidance on joint protection and waterproofing was introduced.
Clean room conditions introduced to joint bays.
Improvements were made to jointing instructions.
4) Risk Management
Joints identified as potential failure candidates were replaced with either joints of a
different design from the same manufacturer or joints from a different manufacturer.
Inspection, partial discharge testing and X-Raying of all joints installed from the same
manufacturer were carried out.
5) Repair/Corrective Action
In most cases the affected joints were removed, which required the insertion of a new
piece of cable and 2 joints and the joint bay was extended to fit the new joints
6) Other
A new reinforced racking design was introduced

21
Chapter 2 The Role of Improved Materials, Design, Assembly and
Quality Control in Mitigating the Effects of Termination and Non-
buried Joint Failures
This section examines how matters may be improved with respect to materials, design, assembly and
quality control in preventing termination and non-buried joint failures and mitigating their effects. As part
of this process, the results of the survey are reviewed to identify the causes of faults and steps identified
that could be taken to ensure these faults did not occur. It should be noted that some of the measures
identified in the Survey Results Section 2.1 below may be repeated to some extent in the Sections 2.2 to
2.4 dealing with Materials, Design, etc. This was done to ensure the Technical Brochure is as complete as
possible.
2.1 Survey Results
It is of considerable importance that the results of the survey in section 1.3 are taken into account and
that, where causes were identified, these are acknowledged and steps are taken to avoid these causes in
the future. The causes and recommended mitigations are listed below:-
2.1.1 Terminations
2.1.1.1 Design
Cause Mitigation
Unsuitable top O ring seal used leading to moisture
ingress
Use appropriate O ring and fit
properly
Powder separation of chemical mixture. Ensure correct compounds are used
and installed correctly
Earthing conductors slipping off metal sheath in
termination by sliding over PE sheath.
Ensure correct installation. Use
checklist for installation.
Circulating current flowing through insulator screen
causing overheating and damage.
Ensure the correct bonding design is
installed
Pre-molded insulation degradation at extremely low
temperatures
Ensure design suitable for operating
temperatures high and low
Damage due to thermal cycling. Design and test for heat conditions.
(Snaking cable before terminating to
minimise conductor expansion into
the termination )
Interface design.
Degradation of components in stress cone.
Change components or design
Use appropriate materials and
enhance the interface design
Consider extended Prequalification
Tests.

22
Cause Mitigation
GIS copper corona shield with thin layer having
whiskers, leading to PD and breakdown.
Design corona shield materials for
use in GIS cable termination box.
Inspect all components prior to fitting.
Stress cone interface contaminants Jointer trained on fitting accessory, as
recommended in Appendix 3
Ensure clean conditions when jointing
2.1.1.2 Manufacture
One case was identified but no details were supplied – no additional mitigation proposed.
2.1.1.3 Workmanship
Cause Mitigation
Jointer damaged insulation Follow Appendix 3
Consider use of inspection test plans
(ITP’s)
Poor XLPE surface shaping - copper contaminants
between cable and stress cone-contaminants invasion of
oil
Follow Appendix3
(ITP’s)
Shavings of copper contamination during the insertion of
pre-molded insulation
Follow Appendix 3
(ITP’s)
Poor surface of outer semi conducting layer-defective
position of compression device
Follow Appendix 3
(ITP’s)
Void generation between epoxy and stress cone Follow Appendix 3
(ITP’s)
Plastic wrap is used for protection during construction.
Void generation at cable/stress cone interface by
overbending of cable and shaving cable insulation too
much.
Generation of crack in epoxy insulator by stressing it
more than it was designed.
Overbending of cable.
Follow Appendix 3
(ITP’s)

23
Cause Mitigation
Void generation at cable/stress cone interface by
conductor centering error, when conductor sleeves were
compressed
Wrong insert position
Follow Appendix 3
(ITP’s)
2.1.1.4 Overvoltage
Cause Mitigation
One case due to switching/lightning surge Ensure appropriate design and
installation of lightning protection, when
required.
2.1.1.5 Weather Effects
Cause Mitigation
Lightning Ensure lightning protection used, when
needed
Water entry Follow Appendix 3 and use proper O
ring and fit it properly (it could be a
design/material problem)
Connection broken, due to mechanical overload Ensure that not overbend
Jointing with high relative humidity Use of an enclosed air conditioned work
environment
Follow Appendix 3
2.1.1.6 Bonding Problems
Cause Mitigation
Metal sheath incorrectly bonded on a single core cable,
resulting in a sheath circulating current that overheated and
damaged the termination
Ensure bonding design is followed
Carry out checks during commissioning
Bad connections; poor design of wiping gland leading to
mechanical movement, sparking and failure
Ensure design suitable for operating
temperatures high and low and installed
properly.

24
2.1.1.7 Fluid/Gas Problems
Cause Mitigation
Partial discharge in fluid Ensure correct fluid is used and that
fluid is properly treated and tested and
that it is at the right level.
Leaking fluid or gas Check where fluid or gas is leaking
from, repair if necessary, and top up.
Replace termination or component
causing the leak.
2.1.1.8 Others
Cause Mitigation
Unknown - breakdown just above stress cone Ensure design is suitable for high and
low operating temperatures
Contaminants noticed at the cable stress cone interface Remove
Follow Appendix 3
Moving cables after installation Ensure cables do not exceed their
thermomechanical design limits, are
properly clamped and are not
physically disturbed
2.1.2 Non-buried Joints
2.1.2.1 Design
Cause Mitigation
Stress cone with incorrect inner diameter Ensure joint is suitable for use on
specified cable after cable is prepared
Shape of embedded electrode not right Ensure design is compatible
Ensure adequate Prequalification and
Type Tests are carried out
Poor tape design Ensure material used has the right
properties and installation instructions.
Consider Prequalification Testing

25
2.1.2.2 Manufacture
Cause Mitigation
Defective manufacture of stress cone (voids) Ensure manufacturer’s QC system is
adequate
Consider Prequalification testing
Poor material quality Ensure manufacturer’s QC system for
materials is adequate
Consider Prequalification testing
Water penetration from a crack, because of manufacture
problem with metallic sheath
Ensure manufacturer’s QC system is
adequate
2.1.2.3 Workmanship
Cause Mitigation
Jointer mistakes causing damage to insulation and poor
insulation shield shaping.
Water penetration, metallic contaminants, wrong inset
position.
Follow Appendix 3
(ITP’s)
Poor adhesion of stress cone Follow Appendix3
(ITP’s)
Metallic contaminants in the insulation tape.
Void generation with poor tape shaping.
Contaminants.
External damage by jointing tool, when connection box
was assembled.
Follow Appendix3
(ITP’s)
Fibrous contaminant in extruded insulation.
Clamping of screen wires caused damage of outer semi-
conducting layer
Follow Appendix3
(ITP’s)
Loose flakes of applied semiconducting coatings in joint
assembly.
Follow Appendix 3
Ensure proper procedures followed,
adequate drying time and care in
positioning of the joint body.

26
2.1.2.4 Overvoltage
Cause Mitigation
In only one case was joint damage attributed to possible
lightning strike
Ensure appropriate lightning
protection is used.
2.1.1.5 Weather Effects
Cause Mitigation
In only two cases was failure attributed to weather
effects, namely water penetration.
Follow Appendix 3
(ITP’s).
Adequately designed casing (coffin)
filled with waterproof compound.
2.2. Design and Materials
In considering the design of terminations and joints it is necessary to consider the materials to be used, the
pressures in different parts of the accessory assembly, the different electrical characteristics, etc
2.2.1 Air Insulated Terminations
Air Insulated Terminations are generally used outdoor to terminate cables in air insulated substations. They
may have porcelain or composite insulators and may be filled or unfilled. The design adopted may depend
on the local environment with respect to the required basic impulse level voltage (BIL), maintenance
requirements, pollution (industrial and ocean), reliability and altitude. Surface creepage distances may
need to be increased in areas of high pollution, excessive sea spray or at high altitudes.
2.2.1.1 Porcelain Insulators
Glazed electrical grade porcelain is the most common and widely installed insulator. It has high reliability in
terms of electrical and mechanical performance. It requires periodic maintenance (cleaning) to remove
pollution deposits from the insulator surface (sheds). It has high resistance to surface tracking. Porcelain
production is a mature technology and can be provided for MV to EHV cable terminations and for both AC
and DC application.
However, porcelain can be susceptible to external mechanical damage and to electrical failure (internal or
external). It can shatter on termination failure with pieces of glazed porcelain and other debris projected
over the surrounding area by the force of the failure. The potential for injury or damage to adjacent
equipment in the surrounding area is high.

27
2.2.1.2 Composite or Polymeric Insulators.
Fig 3 Composite insulator filled with synthetic oil
There are many types of composite insulators available on the market. The most common design consists
of a fibreglass tube covered by elastomeric sheds (silicone). This solution is much lighter than a porcelain
insulator and is normally much easier to handle during installation. However, the bond between silicon
rubber and the epoxy glass fibre pipe must be certified as this can be a weak point.
Composite insulators are available up to EHV applications, even though at this stage there is no long term
operational experience at EHV levels.
Composite insulators have many advantages. In particular they have proven to be reliable even under
exceptional events such as earthquakes, system faults and vandalism. They also provide good insulation
performance due to their silicone housing and the intrinsic hydrophobic characteristic of this material. Well
designed composite insulators have limited ageing. They give satisfactory performance in heavily polluted
areas, where no cleaning or special maintenance is necessary and this can provide important economic
savings.
Their technical and economic advantages are of particular significance in the EHV and UHV range of
accessories. This is because of their design flexibility (single pieces of 10 m or more may be manufactured),
relative low weight (10-30% of a corresponding porcelain insulator), ease of handling for manufacturing and
installation and their ability to withstand stresses, such as seismic events and high levels of pollution.
From the point of view of end-users, a very important feature of composite insulators is safety. They reduce
the potential for manual handling injury during delivery and installation. Since they are not brittle, the risk
following an internal fault, with the associated projection of material, is greatly reduced compared with
porcelain.
The satisfactory long term performance of composite insulators is directly related to electrical and
mechanical design, good selection of the material, good manufacturing processes and quality control.
Environmental constraints of the installation site such as the required BIL, temperature, barometric
pressure (for high altitude), presence of aggressive gases, pollution, and humidity should be taken into
account in the design. Qualification procedures can help to qualify the technology and the materials and
assure the performance during the required life time of the insulator and these are dealt with in detail in
TB455 ‘Aspects for the Application of Composite Insulators to High Voltage (≥72kV) Apparatus’.
A range of biological growths have been reported on composite insulators leading to a reduction of the
hydrophobicity. However, the overall performance of the composite insulator design generally remains
satisfactory. Bird attacks have also been reported, but this appears to be a problem related to insulators in
some countries and usually only happens when de-energised or before the insulators are put into service

28
Another consideration is whether vapour could permeate directly through the sheds and walls of the
housing (polymeric materials are generally slightly permeable for vapour) or through the bonding area
between flanges and fibre-reinforced plastic (FRP) tube. Investigations and service experience indicate that
the amount of moisture ingress due to these mechanisms is below the quantities which can pass through a
good sealing system. Quantities can easily be controlled by internal desiccants as is usual practice for
much of the HV apparatus in the electric power system. In the case of terminations/sealing ends this is
often accomplished by using filling compounds. Nevertheless research continues in an attempt to better
understand these mechanisms and to derive minimum design requirements on composite hollow core
insulators used for HV apparatus applications.
Most damage in composite insulators can be attribute to errors during transport, un-packing, re-packing,
manipulation and storage of the insulators. These aspects are dealt in detail in TB 455 ‘Aspects for the
application of Composite Insulators to High Voltage (>=72 kV) Apparatus’, Chapter 9 ‘Handling and
Maintenance’. In this chapter, procedures and rules are given for: unpacking, repacking, storage, handling
and cleaning.
A composite termination has the advantages of a simple structure. Its anti-pollution capacity depends
mainly on the number of sheds and their size and orientation.The terminal must be installed upright. - it
cannot be installed inclined or curved.
Porcelain and composite terminations are compared in the Table 5 below
Element Porcelain Insulators Composite Insulators
Environmental Can shatter
Periodic cleaning required
Poor pollution performance
It’s earthquake performance is
not so good
Impermeable to animal attack
even when unenergised
Safe/ Inert
Limited cleaning required
High performance in polluted
areas
Good earthquake performance
Possible attack by animals during
storage and while unenergised
Chemical Not hydrophobic
Compatibility with SF6 by-
products and oil
Hydrophobic
Compatibility of filling material to
be checked
Mechanical Can shatter under fault conditions
High weight
Vulnerable to vandalism
No moisture ingress through the
insulator from outside.
1
1
Note for both types of insulators there
may still be some moisture ingress
through the top and bottom metal
components or gaskets
Will not shatter but may split
Low weight
Less susceptible to vandalism
Possible moisture ingress through
the insulator from outside.
1
Rating Performance No practical temperature limit
(temperature limits exceed those
of other components)
Temperature limits of
-55 to +110
o
C
Other Properties Lot of experience, but relatively
long manufacturing time
Because of its weight it’s not so
Limited service experience
Because of its weight its relatively

29
Element Porcelain Insulators Composite Insulators
easy to handle and install. Heavy
manual handling or mechanical
assistance required
Can be damaged (cracked or
chipped) by handling and
installation. Small damage can
be repaired in-situ.
easy to handle and install
Not so likely to be damaged
Table 5 Comparison of Porcelain and Composite Insulators
It can be seen that each outer housing material has its advantages and disadvantages. The selection of the
appropriate termination body depends on the particular installation conditions.
The satisfactory performance of composite terminations is dependent on the inner electrodes and the
electric field distribution within and along the termination. This, in turn, depends on the top electrodes, the
insulator material, the inner electrodes, non-linear coatings, cable make-up; etc All of these components
must be designed, manufactured and installed to control the operating electrical stresses.
Fig 4 Example of a 170kV composite
cable termination
2.2.1.3 Latest Developments
The latest developments on the market provide two alternative solutions:-
1) Self Supporting Terminations
a) A termination filled with silicon based leak-proof gel that replaces the traditional liquid
fluids. This solution has been tested up to EHV, but service experience is available
only up to 132kV. The filling procedure has to be strictly controlled to ensure proper
filling.
b) A fully dry termination, where no liquid or filling is used

30
Fig 5 Example of a Self Supporting Fluidless
Cable Termination
2) Supported or Flexible Type A Prefabricated Outdoor Termination
This type of termination has elastomeric sheds and an external stress cone. The stress
cone and the sheds form one single factory-tested premolded component and they are
widely used in the voltage class up to 150kV. With this termination type a completely “dry”
design is obtained. Note this termination is not self supporting and must be connected to
an overhead conductor or to another component e.g. a surge arrester, able to support the
termination.
Fig 6 Example of a Dry Type
Supported Termination
3) Disruptive–proof Outdoor Terminations i.e. terminations that are designed to limit the
consequence of an internal power arc, etc.
One must also bear in mind the effect of insulation retraction on the termination. Retraction is a result of
the mechanical stress formed in the insulation during the manufacturing process. When the cable is cut, in
order to install the accessory, the insulation may retract on the accessory and lead to a failure. This must
be taken into account in the accessory design.

31
2.2.2 GIS and Oil Immersed Terminations
EHV and HV cables may also be directly terminated in SF6 insulated switchgear (GIS) and transformers to
eliminate air-insulated interfaces. This solution has the significant advantage of markedly reducing
substation area requirements and costs in urban, suburban and industrial plant locations. It also eliminates
insulation contamination from pollutant deposits and reduces exposure to lightning and vandalism.
GIS and oil immersed terminations have similar construction, except for the use of a larger top corona
shield on the termination in order to reduce the top-end stress.
The electrical stress control for GIS and oil immersed terminations follows the same approach usually
employed for outdoor terminations i.e. it uses a premolded stress relief cone, which is fitted over the cable
insulation. The cable is then accommodated inside a cast epoxy resin bushing which separates the cable
from the pressurised SF6 or the oil in the termination end box.
The space inside the epoxy bushing can be filled with insulating fluid or SF6 gas. In order to eliminate any
risk of leakage of this fluid or gas from inside the epoxy bushing, a new generation of dry type SF6 and oil
immersed terminations have been developed. In these dry terminations there is no insulating fluid or gas
between the epoxy insulator and the stress cone, because the latter is in intimate contact with the inner
surface of the bushing; the pressure of the stress-cone at the cable core interface as well as at the inner
epoxy insulator surface can be obtained by means of compression devices such as springs or by special
design of the polymeric part.
It should be noted that currently there is a Joint Working Group B1/B3.33 examining the ‘Feasibility of a
common, dry type interface for GIS and Power cables of 52 kV and above’ (2009 – 2012) and a Technical
Brochure is expected to issued by this WG by the end of 2013.
2.2.3 Insulation Medium
Terminations are generally filled with a dielectric fluid, usually a synthetic (polybutene or silicone based)
insulating liquid, at or slightly above atmospheric pressure. The type and quantity of the fluid depends on
the specific design of the termination. Poor quality of the liquid or contamination, due to external factors
(humidity, water ingress, metallic or other polluting particles, etc), can reduce the electrical performance of
the fluid and result in termination failure.One of the most common issues with the use of fluid is the risk of
leakage through the sealing point areas, typically the weld/plumbing between the cable metallic screen and
the bottom part of the termination or the mechanical seal onto the stress cone. A well-made seal depends
mostly on the skill of the jointers.
There are also designs that use SF6 gas as the insulation medium, but this solution has to bear in mind the
environmental concerns of using SF6 gas.
2.2.4 Connectors
The connector electrically and mechanically joins the conductors of two cables or the cable and the top
connector of a termination. Thus the connector must exhibit good electrical conductivity to avoid
temperatures higher than that of the conductor in any operating condition and also present sufficiently high
mechanical pull-out (tensile) strength to withstand thermo mechanical stresses during operation. It should
be noted that TFB1.46 is currently working on Conductor Connectors (Mechanical and Electrical Testing).
The following types of connectors are used for extruded cable connections:-

32
2.2.4.1 Compression Connector
This connector includes a tube of the same material as the cable conductor into which the conductors to be
joined are inserted. The tube is then compressed by a hydraulic press. The compression connector is the
most commonly used type, because it is easy to install and does not require heat.
The cross section of the connector is at least equal to the cross section of the conductors to be joined.
When the connector is exposed to an electric field, as in taped joints, it is necessary to provide suitable
chamfers at both ends to minimize the effects of longitudinal electrical stresses.
Fig 7 Compression connector
A special bimetallic connector is used when it is necessary to join a copper conductor to an aluminium
conductor. These connectors are half copper and half aluminium. The two connector halves are joined in
the factory by friction welding.
Some companies use a copper alloy connector for both copper and aluminium conductors.
2.2.4.2 Cad Welding
Another way is to make a connection of copper and aluminium conductors by Cad-welding on site, though
Cad welding is not used that often for aluminium. This is an exothermic welding process in which metal and
metal oxide powders are placed in a special crucible mold around the parts to be welded. This mixture is
ignited resulting in a short high temperature reaction,causing the flow of molten metals to form a localised
solid connection.
Fig 8 Examples of Cad Welding

33
2.2.4.3 Soldered or Brazed Connector
Soldered connectors are used with small conductor cross sections (below 630mm
2
) and with cables having
a short circuit current temperature below 160 °C, b ecause the solder can become soft during the cable
system operation. Brazed connectors do not present this problem, but are more difficult to make.
2.2.4.4 MIG or TIG welded connection
The two conductors are fused together by the application of molten metal. A Metal Inert Gas (MIG) or
Tungsten Inert Gas (TIG) welding process is applied in this case. Due to the high temperature developed
during the process, air or water cooling clamps are required on both sides of the weld, in order not to
damage the cable insulation The welding process is used for large aluminium conductors and for insulated
wire copper conductors; in the latter the burning of the wire insulation, if necessary, ensures a good contact
between strands. This technology requires an operator with a very high skill level and is time consuming.
This weld provides a connection with an electrical conductivity, which is equivalent to that of the conductor
itself. The connection is not subject to instability due to decrease of contact pressure as a result of load
cycling. However the tensile strength of the welded connector is significantly (50 to 60 %) lower than the
ultimate tensile strength of the conductor, due to the annealing of the conductor near the weld. If
necessary, for submarine cables, the tensile strength can be improved by round compressing the
conductor and the weld (hardening process).
Fig 9 Example of a MIG Weld
Fig 10 Welding of an aluminium conductor

34
2.2.4.5 Plug-in Connector
Two metal connectors, that terminate the conductor, are jointed through elastic or multi contact spring
loaded contacts that are able to carry the current. Locking pins can be used to anchor the two parts
together. Plug-in connectors can easily join conductors of different materials and cross section.
Fig 11 Plug-in connector (male contact) on prepared cable end.
One of the advantages of a plug-in connection is the shorter length of the joint.
2.2.4.6 Mechanical bolted connector (shear bolts)
With these connectors compression of the conductors inside a ferrule is made by tightening threaded bolts.
The bolts shear off at a predetermined torque and are then finished flush with the surface of the connector.
These connectors are extensively used in MV accessories, and may also be used in HV joints or
terminations, subject to checking their short circuit current and current loading capacity. The compatibility of
these connectors with the termination or joint design must be checked. These connectors have a diameter
larger than the compressed connectors and care must be taken to ensure there are no bits of bolt
protruding above the connector surface. Before using shear connectors consideration must be given to
tensile strength during load cycling and pull out.
2.2.4.7 Mechanical bolted connector
With these connectors compression of the conductors inside a ferrule is made by tightening threaded bolts.
These connectors are extensively used in MV accessories, and may also be used in HV joints or
terminations, subject to checking their short circuit current and current loading capacity. The compatibility of
these connectors with the termination or joint design must be checked. These connectors have a diameter
larger than the compressed connectors and care must be taken to ensure there are no bits of bolt
protruding above the connector surface
Fig 12 Example of a bolted connector

35
2.2.5 Non-buried Joints
Non-buried joints locations may be in tunnels, on bridges, in underground chambers or similar enclosures.
Non-buried joints for XLPE cables usually have premolded joint bodies with additional covering for
protection against moisture and mechanical damage. The additional covering could be heat shrink tubes or
metal housings with additional insulating housings/coffins.
Transition joints for XLPE to oil filled cable are often installed as non-buried joints in underground
chambers. They use metal-tubes combined with epoxy insulators as a barrier between the different
insulating materials - XLPE and fluid impregnated paper. In the case of transition joints full quality control
must take into account electrical and mechanical stresses for both sides of the joint and any interface
locations.
Water can seep into a non buried joint, if any earth or bonding wire connections to the joint are not sealed
properly.
Fig 13 Example of non-buried joints : 145kV single core
cable joints installed in a cable jointing chamber/manhole
2.3 Assembly
TB 476 is a comprehensive document on assembly and quality control of XLPE accessories and the
contents pages are attached as Appendix 3. It gives guidance on aspects of cable accessory
workmanship that need to be carefully considered in evaluating the execution of the work, including the
specific technical risks and the associated skills needed to mitigate them.
Where a termination is to be filled with compound, the manufacturers filling instruction should be followed.
Filling compounds may be such items as polybutene, silicon oil or other dielectric fluid or gas.
2.4 Quality Control
Joints and terminations are delivered to site as kits, which in turn are made up of many components It is
vital to have quality control on all components. The main insulation is either the premolded joint body or
premolded stress-cone, and the testing requirements for these are as defined in IEC60840 and IEC62067.
The manufacturer shall demonstrate or guarantee that the components forming the accessory are the
same as those tested to IEC standards.

36
Each component has a specific function, whether it is secondary insulation, oil, gas or air tightness,
mechanical protection, conductor or sheath connection, etc. It is essential that the manufacturer has in
place quality control plans that define the tests to be carried out and their frequency and these should be
related to the function of the component. The inspection or testing may include visual, dimensional,
mechanical, dielectric, pressure, whether as an incoming control from sub-suppliers or as final control as
semi-finished products (insulators for example). Components must be inspected according to drawings and
specifications with given tolerances, and there must be no deviations outside the given tolerances.
Final checking must be done on delivery to site to ensure the right quantity and quality of materials has
been delivered.
Of course the QC aspects with respect to jointing, as set out in TB 479, must also be followed. This applies
in particular to the certification/approval for the jointers and the site conditions.

37
Chapter 3 The Role of Testing and Condition Monitoring in
Minimising the Incidence or Severity of Termination and Non-buried
Joint Failures
3.1. Testing
3.1.1 General
In order to prove that a cable system meets the expectations of the customer the role of testing at all
stages of design, supply and in-service is clearly important for both the supplier and end-user. In addition,
once a cable system is in service, it may be beneficial to carry out in-service testing to assess the condition
of the system and its components. This section will examine the types of testing and condition monitoring
that may be carried out, when assessing a cable system. This is not intended to be exhaustive, but to
provide guidance on the areas that should be considered. The level of testing required for a cable system
should be decided on by the customer, based on risk and performance requirements.
International standards for underground cable systems generally provide design rules and testing
procedures to assess a cable system and to ensure it meets the requirements for reliable operation during
its design life. These generally focus on prevention of failure, rather than actions that can be taken to
mitigate the consequences of a fault. Some National Standards or individual utility specifications have
introduced fault simulation testing and specify requirements for the performance of the system under these
conditions e.g. an internal arc test is carried out by some utilities to evaluate the consequence of an internal
fault - there is a requirement for this within IEC 62271 requirements for switchgear testing.
It should be noted that a cable system incorporates the cable, terminations, joints, internal terminations and
joint components, filling media, connectors, screen connections, bonding etc, and great care must be
exercised in testing to ensure that all of the components are properly represented and identified in testing
regimes.
3.1.2. Development Testing
Development testing is carried out by the cable accessory supplier during the design of a new accessory.
The results of these tests may indicate to the manufacturer and, where required, the customer, any
changes and improvements that can be made to a cable accessory. An example of development tests are
the environmental tests including salt/fog, rain and pollution tests, carried out on composite insulators,
which are not covered by cable international standards. These tests are carried out by manufacturers to
demonstrate the long term performance of their products and are carried out to in-house test specifications.
IEC61462 ed 1.0 covers the test procedures for Composite Insulators for AC Overhead Line with Nominal
Voltage greater than 1000 volts.
Results of development testing are generally not specified by customers, but may help to inform a decision
on the suitability of a cable termination or joint for use for a particular application or in a particular location,
for example the suitability of terminations for use in areas of high pollution.
Development tests are performed by the manufacturer during the development of a new accessory and are
intended to ensure the accessories long term performance and to assess safety margins. The tests include:
Analysis of electrical, mechanical and material compatibility
Electrical tests up to breakdown and mechanical and thermal tests on prototypes
Wet and pollution test on outdoor terminations

38
Electrical and thermal tests of connectors
Mechanical tests on premolded components (on the insulators and connectors)
Fire and disruptive failure performance, including Internal Power Arc test on terminations in
accordance with Appendix 4
3.1.2.1 Insulators
IEC 61462 ‘Composite hollow insulators –pressurised and unpressurised insulators for use in electrical
equipment with rated voltage greater than 1000 V’ specifies both design and type test requirements for self
supporting composite insulators. The tests in this IEC standard are designed to provide information on
material selection, manufacturing processes, material thickness and adhesion and end fitting material
selection an attachment.
To complete the project of developing a new accessory, construction drawings shall be prepared of all
components and a full size prototype shall be manufactured and subjected to tests. If the prototype
includes specific components such as premolded parts, composite and epoxy resin insulators, it is
necessary to develop the technology to produce these components
The tests should show the limit in the performance of the accessory and guarantee a proper safety margin
with respect to test values stated in the relevant IEC standard.
Tests carried out must ensure that the entire family of accessories is able to withstand the stresses, which
they may be subjected to in their operational life.
Fig 14 Salt-fog test on insulator
The termination may be exposed to a saline solution of a different concentration depending on the level of
pollution it will experience. In this condition it is then subjected to an AC voltage test. For composite
insulators with a polymeric coating, which are subject to aging of the surface, the pollution test is
performed after an aging of 1000 hours in saline fog or an electrical cycle-environmental of 5000 hours
(see IEC 62 217)
3.1.2.2 Connectors
Development testing may also be done for connectors. Thermal cycles are performed on connectors and
contacts used in the accessories following the standards of IEC 61238-1, currently restricted to medium
voltage. During the test, measurements of temperature and electric resistance as a function of time are
taken. Short circuit current tests are also performed on the connectors.

39
Fig 15 Tests on connectors
3.1.2.3 Filling Fluids
Before using any type of oil or fluid within a specific housing material, equipment manufacturers should
have verified its full compatibility with materials and assembly processes, including health and safety. This
is especially of interest where new types of fluids or other fillers are considered. Some manufacturers have
developed their own qualification procedures, specifying test conditions in terms of temperature, duration,
safety and final acceptance criteria. This forms part of the development tests.
3.1.3. Prequalification Test
Prequalification testing, as in IEC 62067 & 60840, is only specified for cable systems above 150kV or
where the conductor screen stress is designed to be greater than 8kV/mm or the insulation screen stress is
designed to be greater than 4kV/mm,
Prequalification tests are long term tests that are carried to assess the performance of a cable system and
attempt to replicate in-service duty. The test arrangement should be representative of installed conditions,
e.g. fixed and flexible sections and contain both joints and terminations to give a true replication of the
cable system. These tests are intended to verify the thermo-mechanical and electrical behaviour of the
cable and accessories. In some local standards it is also a requirement to monitor and record the pressure
of any insulating mediums used in order to assess the robustness of any sealing arrangements.
After testing, all accessories are to be examined to check for any changes or deterioration that might affect
the performance.
3.1.4. Type Test
Type tests are carried out on the complete cable system and are required for all voltages and design
stresses. These tests provide a minimum requirement to show specific cables and accessories are fit for a
specific purpose. Type tests, as specified in IEC 60840 & IEC 62067, focus mainly on the cable system
short-term voltage withstand performance. They include AC, over-voltage and lightning transients
combined with material aging effects. Following completion of these tests, the cable system must be shown
to be partial discharge free or to have a level of discharge below a certain requirement. If any partial
discharge is present, even below the level specified, it may be prudent to identify the cause of this
discharge. Once tests are completed it is important to disassemble all accessories and closely inspect
them for any signs of electrical activity or physical changes, which may not have caused an electrical
discharge, but may cause mechanical or operational problems. The interpretation shall be based on the
previous experience with development, prequalification and other type tests.

40
Fig 16 Type Test loop of 400kV system
3.1.5 Short Circuit Tests
The WG identified that short-circuit behaviour was not addressed by any IEC standard relating to HV cable
systems. Several utilities have independently taken the step of specifying an additional type test to check
the behaviour of terminations (especially those containing insulating fluid) when they are subjected to short
circuits. Two cases need to be considered
1) A low energy external fault. In this case the fault current passes though the conductor. The
fault is external to the accessory.
2) A high energy internal fault. In this case the fault is the result of component failure or arcing
inside the accessory.
Consideration, depending on the design and installation, should be given to whether it is necessary to do
one or both of the above tests to cover the worst case condition.
These tests are detailed in Appendix 4.
3.1.6. Sample Tests
Sample test requirements are outlined in IEC 60840 and 62067. These tests are to be carried out on a
specified number of components and complete accessories during a production run. For accessories,
where the main insulation cannot be routine tested, IEC 60840 states that a partial discharge and an AC
voltage test shall be carried out on a fully assembled accessory. For individual components the
characteristics of each component shall be verified in accordance with the specifications of the accessories’
manufacturer, either through test reports from the supplier of a given component or through internal tests.
Also the components shall be inspected against their drawings and there shall be no deviation outside the
declared tolerances.
3.1.7. Routine Tests
Routine tests are carried out on some accessory components to be supplied. These tests should form part
of a robust quality control regime and provide confidence in accessories’ quality. As part of these tests, the
main insulation of prefabricated accessory designs is required to undergo AC voltage and partial discharge
tests. Finally each component should be visually inspected for defects.
Insulators filled with oil, gas, or other material should also undergo a pressure test before delivery.

41
3.1.8 Tests on Filling Materials
Filling materials, like polybutene or synthetic oil, are selected based on the material parameters and
characteristics and they are approved during the development, prequalification and type tests. –
specification IEC 60836 covers silicon oil.
It is recommended that a ‘finger print’ of the filling material be determined after delivery, as this ‘finger print’
might be useful during condition assessment programs or failure analysis.
Well established material ‘finger print’ techniques are
AC electrical strength
Dielectric dissipation factor
Fourier transform infrared spectroscopy (FTIR)
Thermal gravimetric analysis (TGA)
3.1.9 Commissioning Tests
Commissioning tests are carried out on the assembled cables, joints terminations, bonding and earthing
once the installation is completed. They are the final tests performed on the cable system prior to
energising and provide the final check that the system has been correctly designed and installed. The
requirements for commissioning tests will vary depending on the type of circuit installed and the
consequences of failure.
There are very few tests that can be carried out that will prove the long term life of cable, joints and
terminations. However, it is recommended that an AC insulation test is carried out with partial discharge
monitoring, if possible, of all joints and terminations. Ideally this is carried out using a resonant test voltage
generator. This allows the cable system to be energised off-line and at low energy and so there is a
minimised risk of a disruptive accessory failure during the test. The tests may give an early warning of
potential failure points, before a later breakdown of the complete cable system in service leads to bigger
problems. The commissioning tests should be performed according to the relevant IEC standard.
It is possible to carry out an AC test by energising the termination with system voltage (soak test) and using
on-line partial discharge monitoring. This is not ideal, as noise from the system can mask discharge activity
occurring within the accessory. In addition, if a breakdown does occur this will lead to a disruptive failure of
the joint or termination (as the full system short circuit current is available to flow through the failed
accessory) and may lead to an outage and power disruption. Such a failure presents both a safety risk on
site and introduces a significant delay to commissioning of the circuit while the affected components are
replaced.
Fig 17 On site Commissioning Test (in this set up three mobile tests sets needed simultaneously, because
of cable length)
A DC oversheath test should also be carried out to ensure the cable system and its accessories are
insulated from earth

42
.
Fig 18 Discharge tracks on cable PE outer serving due to a defect. The discharge tracks are a
consequence of fault localisation pulses
3.2. Condition Monitoring
As indicated in TB420 Generic Guidelines for Life Time Condition Assessment of HV Assets and Related
Knowledge Rules, it is recommended that a good database of information is established for each piece of
equipment as it ages. Useful information on the aging process during the full service life includes loading,
maintenance test results, fault history, general ambient and environmental conditions and details of any site
incidents.
To effectively manage the aging of HV cable accessories, a structured methodology to analyse and prevent
in-service failures is recommended. A suggestion for such methodology is given in Cigré TB420, clause
4.2. The final step in this methodology is to gather the outputs from this process into a management
strategy which can be used for:
(a) preventative maintenance,
(b) decisions on equipment change-out
(c) improvement in the specification, design or manufacture of new equipment.
Regarding (a) preventative maintenance, there are many possible approaches to monitoring the condition
of terminations and non-buried joints. These vary from visual inspection to on-line monitoring or regular
testing while out of service, etc.
The monitoring to be carried out depends on:-
i. The importance of the circuit
ii. The history of the circuit and its accessories
iii. The potential repair time
iv. The potential cost of the outage
v. Potential cost of the damage
vi. Effect on reputation
vii. Potential damage from the failure
viii. Effectiveness of the monitoring system adopted
ix. Availability of monitoring tools and trained personnel
x. Cost of monitoring

43
Fig 19 Example of condition monitoring technique:
The X-ray photo of cable outdoor termination used
to check any internal displacement of the top-connector
A list of current Condition Monitoring Tools is detailed in Appendix 5. To assist in the selection of a
monitoring tool, each tool is described under a number of headings including:-
• experience - the level of working experience of each condition monitoring tool is categorized as
either well established (‘W’) or under development (‘D’).
• effectiveness - one diagnostic monitoring tool may be considered (based on costs, time and
results) as more effective than another in finding damages or degradations that will lead
eventually to system failure ; categorized here as useful (‘U’) and less useful (‘L’).
• level of expertise required - whether high or low level expertise is required i.e. a
technician/engineer trained in the particular tool being used or is a general operative sufficient to
operate the tool.
• cost

44
Chapter 4 Recommendations
The aim of the WG has been to produce a Technical Brochure that could be used by designers,
manufacturers, contractors and utilities to increase the integrity of terminations and non-buried joints.
Many approaches to this subject are possible, depending on the factors outlined in Section 3.2 above.
Two cases need to be considered:-
a) where the accessories are on an existing cable circuit
b) where the accessories are to be installed on a new cable circuit
4.1 Existing Circuits
For existing circuits the following considerations apply:-
i. The importance of the circuit
ii. The history of the circuit and its accessories
iii. The potential repair time
iv. The potential cost of the outage
v. Potential damage from the failure
vi. Potential cost of the damage
vii. Effect on reputation
viii. Effectiveness of the monitoring system adopted
ix. Availability of monitoring tools and trained personnel
x. Cost of monitoring
4.2 New Circuits
If a new circuit is being installed then it seems appropriate to use proven composite terminations (unfilled,
if possible) and proven joints. The designs should comply with IEC 60840 and 62067 as far as PQ and
Type testing, Routine and Site Test are concerned. There should be a full QC system in the factory for
both cables and accessories. Of course both joints and terminations should be installed fully in
accordance with the manufacturer’s instructions, and in accordance with TB 476.
When new accessories are being installed a decision will have to be made on what condition monitoring,
if any, is necessary. Refer to recommendations of Section 3.2.

45
Chapter 5 Conclusions
The following conclusions resulted from the work carried out by this working group:
1. The survey completed by this WG has shown that disruptive discharge has been experienced in
terminations and non-buried joints.
2. Utilities are concerned about these discharges.
3. In the case of installing new cable systems, utilities should try to adopt designs that either do not
experience disruptive discharge and/or that have been tested to ensure the impact is kept to a
minimum.
4. Full quality control procedures should be employed during the manufacture, delivery, storage and
the installation process.
5. Jointers should be fully certified, have experience of the accessory to be installed and their work
should be checked/monitored/inspected.
6. All materials and jointing tools used should be appropriate for the work, be in good condition,
have been correctly stored and be within their expiry dates.
7. The site conditions should be suitable with respect to space, safety, dust, pollution, humidity and
temperature.
8. On-site testing at an elevated voltage level, as prescribed in the IEC standards, is strongly
recommended during commissioning.
9. A risk analysis should be done to determine the corrective actions required for existing
accessories, which have experienced disruptive discharge or it is suspected they may do so in the
future. This can vary from leaving the accessory in service to partial or full replacement. Whether
it is decided to go for full or partial replacement, steps 3 to 8 above should be followed.
10. If it is decided to do condition monitoring on existing or new circuits, then the following items need
to be considered
a) The importance of the circuit
b) The history of the circuit and its accessories
c) The potential repair time

46
d) The potential cost of the outage
e) Potential cost of the damage
f) Effect on reputation
g) Potential damage from the failure
h) Effectiveness of the monitoring system adopted
i) Availability of monitoring tools and trained personnel
j) Cost of monitoring

47
Appendix 1
Terms of Reference
Study Committee No: B1
WORKING BODY FORM
Group No : WG B1.29 Name of Convener : Eugene Bergin (Irl)
TITLE of the Working Group : Guidelines for maintaining the integrity of XLPE transmission cable
accessories
Background:
The work is motivated by the occurrence of disruptive failures of cable end terminations, with consequent
risks for personal and material loss and damage.
Terms of Reference:
The scope shall be limited to land XLPE cable systems at 110 kV and above. Priority shall be given to
outdoor and oil-immersed terminations, but also joints (that are not directly buried) shall be considered.
The work shall concentrate on recent incidents, but near misses shall also be included in the analysis.
The WG shall:
• Review recent experience with failures of outdoor and oil-filled terminations
• Review the consequences of termination failures for cables within substations and outside.
• Examine the role of design, assembly and quality control in mitigating the effects of termination failures
• Examine the role of testing (development, type, routine & after-laying) and condition monitoring in
minimising the incidence or severity of termination failures
• At the SC B1 meeting in 2010, the WG shall provide recommendations on possible extensions of work
into joints (not directly buried), and accessories for oil-filled cable.
• The full report shall be made available for final review at the B1 annual meeting in 2011.
Deliverables:
• An Executive Summary article for Electra
• A full report to be published as a Technical Brochure
• A Tutorial

48
Created: 2008 Duration: 3 years
Convener e-mail: bergin_eugene@yahoo.co.uk
WG members from: AU, BE, BR, CA, FR, DE, IN, IT, JP, KR, NL, NO, ES, CH, UK, US
Other stakeholding SC’s: B2, B3, C3
Approval by TC Chairman : Date : 2008

49
Appendix 2
Bibliography/References
IEC Standards
1) IEC 60840 Ed 3 Power cables with extruded insulation and their accessories for rated voltages
above 30 kV (Um = 36 kV) up to 150 kV (Um = 170 kV) –Test methods and requirements
2) IEC 62067 Ed 2 Power cables with extruded insulation and their accessories for rated voltages
above 150 kV (Um = 170 kV) up to 500 kV (Um = 550 kV) – Test methods and requirements
3) IEC 62217 Ed. 1: Polymeric insulators for indoor and outdoor use with a nominal voltage greater
than 1 000 V —General definitions, test methods and acceptance criteria.
4) IEC 61462 Ed. 1.0: Composite insulators - Hollow pressurized and unpressurized insulators for use
in electrical equipment with rated voltage greater than 1000V - Definitions, test methods,
acceptance criteria and design recommendations
5) IEC 62271:High voltage switchgear and control gear – Part 209: Cable connections for gas-
insulated metal-enclosed switchgear for rated voltages above 52kV – Fluid-filled and extruded
insulation cables – Fluid-filled and dry-type cable-terminations
6) IEC 61039: General Classification of insulating liquids
7) IEC 60815-1 TS Ed. 1.0: Selection and dimensioning of high-voltage insulators for polluted
conditions - Part 1: Definitions, information and general principles
8) IEC 60836 Ed 2.0 b 2005 Specification for unused silicon insulating liquids for electrotechnical
purposes.
9) IEC 61109 Ed 2 Insulators for overhead lines - Composite suspension and tension insulators for
AC. systems with a nominal voltage greater than 1 000 V - Definitions, test methods and
acceptance criteria

50
CIGRE
Electra no Title of Electra Paper
10) 243 Update of Service experience of HV underground and submarine cable systems
11) 235 Statistics on AC underground cables in power networks
12) 210
Current cable practises in Power Utilities (A report on the recent AORC Panel
Regional Workshop in Malaysia)
13) 204 General overview on experience feedback methods
14) 141.1 Service experience of cables with laminated protective covering.
15) 137 Survey of the service performance on HV AC cables.
16) 212 Thermal ratings of HV cable accessories
17) 203 Interfaces between HV extruded cables and accessories
TB no Title of Technical Brochure
18) 502
19) 476
High Voltage On Site Testing with Partial Discharge Measurement
Cable Accessory Workmanship on Extruded High Voltage Cables
20) 455 Aspects for the Application of Composite Insulators
21) 420
Generic Guidelines for Life Time Condition Assessment of HV Assets and Related
Knowledge Rules
22) 379 Update of Service experience of HV underground and submarine cable systems
23) 338 Statistics on AC underground cables in power networks
24) 303
25) 279
Revision of Qualification Procedures for HV and EHV AC Extruded Underground
Cable Systems
Maintenance of HV Cables and Accessories
26) 211 Preparation of guidelines for collection and handling of reliability data
27) 210 Interfaces between HV extruded cables and accessories
28) 177 Accessories for HV cables with extruded insulation
Accessories for HV extruded cable. Types of accessories and terminology

51
Session Paper
No. Title of Session Paper
29) 21-01 Studies of Impurities and Voids in Cross-linked Polyethylene Insulated Cables. Pre-
fabricated Terminations.
30) 21-02 Plastic insulated cable with voltage dependent core screen.
Jicable
31) Jicable 2011 paper A.3.7 “Return of Experience of 380 kV Power Cable Failures” from Sander
MEIJER (TenneT TSO), Johan SMIT, Xiaolin CHEN (Delft University of Technology), Wilfried
FISCHER (50 Hertz Transmission GmbH), Luigi COLLA (Terna S.p.A.)
32) Jicable 2011 paper A.5.4 “Remedial action and further quality assuring measures after a failure in
a 400 kV GIS cable termination” from Frank JAKOB, Frank KOWALOWSKI, Claus KUHN, Wilfried
FISCHER (50 Hertz Transmission GmbH), Sigurdur A. HANSEN (Südkabel GmbH)
33) Jicable 2011 paper A.5.3 “Dry terminations for high voltage cable systems” from Pascal STREIT
(NEXANS)
34) Jicable 2003 paper A.6.2 “Anti-explosion protection for HV porcelain and composite terminations”
from Gahungu, Cardinaels, Streit, Rollier (Nexans)
35) Jicable 2003 paper A.6.4 “New dry outdoor terminations for HV extruded cables” from DEJEAN
(PIRELLI France), QUAGGIA, PARMIGIANI (PIRELLI Italy), GOEHLICH (Technical University of
Berlin);.
36) Jicable 1999 paper A.5.4 “Development of synthetic and composite terminations for HV and EHV
extruded cables” (LE PURIANS from EDF R&D and JUNG from EDF CNIR – RTE
37) Jicable 1995 paper A.3.2 “Composite EHV terminations for extruded cables” (ARGAUT, LUTON
from SILEC and JOULIE, PARRAUD from SEDIVER.

52
Appendix 3
TB 476 Cable Accessory Workmanship on Extruded High Voltage Cables Oct 2011
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

53
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 Molded 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-molded 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
6.7.2 Outer Protection Assembly ................................................................... 50

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