IEC TR 63463:2024

IEC TR 63463 ®
Edition 1.0 2024-01
TECHNICAL
REPORT
colour
inside
Life extension guidelines for HVDC converter stations

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IEC TR 63463 ®
Edition 1.0 2024-01
TECHNICAL
REPORT
colour
inside
Life extension guidelines for HVDC converter stations

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.020; 29.240.10 ISBN 978-2-8322-8064-5

– 2 – IEC TR 63463:2024 © IEC 2024
CONTENTS
FOREWORD . 7
INTRODUCTION . 9
1 Scope . 12
2 Normative references . 12
3 Terms and definitions . 12
4 General procedure for performing a life assessment . 14
4.1 General . 14
4.2 Preparation . 15
4.3 Team . 15
4.4 Assessment process . 16
4.5 Deliverable . 17
4.6 Life assessment timetable . 17
5 Thyristor based HVDC systems performance issues . 20
5.1 General . 20
5.2 Survey of availability and reliability of HVDC systems in the world . 20
5.2.1 General . 20
5.2.2 AC and auxiliary equipment . 20
5.3 Operating history . 21
5.4 Major equipment/system/sub-system failure/refurbishment summary . 21
5.5 Life assessment and various options for a refurbishment project . 22
5.6 Methods for assessing reliability, availability and maintainability of existing
components . 24
5.7 Basis for replacement/refurbishment of equipment . 25
5.8 Performance after replacement and refurbishment . 27
6 Life assessment and life extension measures of equipment . 27
6.1 General . 27
6.2 Spares . 28
6.3 Converter transformers . 28
6.3.1 General . 28
6.3.2 Life assessment . 29
6.3.3 Refurbishment/Replacement . 29
6.4 HVDC control and protection . 30
6.4.1 General . 30
6.4.2 HVDC converter controls . 30
6.4.3 Valve base electronics (VBE). 31
6.5 Thyristor valves . 32
6.5.1 General . 32
6.5.2 Life assessment . 32
6.5.3 Refurbishment/Replacement . 33
6.6 Valve cooling system . 34
6.6.1 General . 34
6.6.2 Life assessment . 34
6.6.3 Refurbishment/Replacement . 34
6.7 DC equipment . 35
6.7.1 General . 35
6.7.2 Oil-filled smoothing reactors . 35

6.7.3 Air-core smoothing reactors . 36
6.7.4 DC voltage dividers . 36
6.7.5 DC current transducers . 37
6.7.6 DC surge arresters . 37
6.7.7 DC support insulators and bus work. 38
6.7.8 DC switches . 39
6.7.9 Station auxiliary supplies . 39
6.7.10 Earth electrodes and electrode lines . 40
6.8 Cyber security . 40
6.9 AC filters . 41
6.9.1 General . 41
6.9.2 AC filter capacitors . 42
6.9.3 AC filter reactors . 42
6.9.4 AC filter resistors . 43
6.10 DC filters . 43
7 Guideline for assessing techno-economic life of major equipment: Operational
issues – Maintenance cost/management and availability of spares . 43
7.1 Types of components used within HVDC systems . 43
7.1.1 General . 43
7.1.2 Commercial off-the-shelf (COTS) components . 44
7.1.3 Configured products . 44
7.1.4 Bespoke (customized) products . 44
7.2 Management of obsolescence . 44
7.2.1 General . 44
7.2.2 COTS, configured COTS components and bespoke components . 45
7.2.3 Components designed to meet a specific specification. 45
8 Recommendation for specification of refurbishing HVDC system . 46
8.1 General . 46
8.2 Main components of a converter station: guideline for the specification . 47
8.2.1 Thyristor valves . 47
8.2.2 Cooling of the valves . 48
8.2.3 Converter transformers . 49
8.2.4 Smoothing reactor . 50
8.2.5 Control system . 51
8.3 Interfaces . 53
8.3.1 General . 53
8.3.2 Electrical interfaces . 53
8.3.3 Mechanical interfaces . 53
8.3.4 Environmental interfaces . 53
8.3.5 Space interface . 53
8.3.6 Auxiliaries interface . 54
8.3.7 I/O interfaces . 54
8.3.8 Example: valve and control system refurbishment . 54
8.4 Maintainability including spares requirement . 55
8.5 Cost minimization . 55
8.6 Replacement time minimization . 56
8.7 Operation outage minimization . 56
8.7.1 Outage due to refurbishment works: brownfield and greenfield . 56
8.7.2 Outage due to a forced maintenance . 57

– 4 – IEC TR 63463:2024 © IEC 2024
8.7.3 Outage for scheduled maintenance . 57
8.8 Guarantees, performance and warranties . 57
9 Testing of refurbished/replacement equipment. 58
10 Environmental issues. 58
10.1 General . 58
10.2 Insulating oil . 59
10.3 Polychlorinated biphenyl . 60
10.4 Sulphur hexafluoride gas . 60
10.5 Halon gas . 61
10.6 Refrigerants . 62
10.7 Asbestos . 62
10.8 Audible noise . 62
10.9 Electromagnetic effects . 63
10.10 Mitigation of environmental issues . 63
11 Interfaces and employer inputs . 64
11.1 General – Interface issues . 64
11.2 System studies . 65
11.2.1 General . 65
11.2.2 Refurbishment of HVDC projects . 67
11.3 Control and protection . 70
11.3.1 General . 70
11.3.2 Mechanical interface control and protection system . 71
11.4 Thyristor / Valves . 71
11.5 Transformer . 72
11.6 Equipment AC/DC yard . 73
11.6.1 General . 73
11.6.2 Measuring devices . 73
11.7 Auxiliaries . 74
12 Outage planning . 74
12.1 General . 74
12.2 Stage 1: Activities before outage. 75
12.3 Stage 2: Outage . 76
12.4 Stage 3: System test, performance and trial operation . 76
12.4.1 General . 76
12.4.2 System tests . 76
12.4.3 Performance tests . 77
13 Regulatory issues . 77
13.1 General . 77
13.2 Renovation and modernization . 79
13.3 Recommendation . 79
14 Techno-economics – Financial analysis of refurbishment options . 79
14.1 Objective of financial analysis . 79
14.2 Preliminary designs . 79
14.3 Reliability and availability models . 80
14.4 Financial models . 80
14.5 Impact of discrete events on financial models . 81
14.6 Cost-benefit analysis . 81
14.6.1 General . 81

14.6.2 Background . 81
14.6.3 Alternatives . 81
Annex A (informative) Refurbishment experience . 83
A.1 Long distance HVDC . 83
A.1.1 Pacific Intertie . 83
A.1.2 New Zealand 1&2 . 84
A.1.3 CU . 84
A.1.4 Square Butte . 84
A.1.5 Skagerrak1&2 . 84
A.1.6 Cahora Bassa . 85
A.1.7 Intermountain Power Project . 85
A.1.8 Cross Channel . 86
A.1.9 FennoSkan1 . 86
A.1.10 Inga Kolwezi . 86
A.1.11 Kontek . 86
A.1.12 Gotland 2&3 . 86
A.1.13 KontiSkan 2 . 86
A.1.14 KontiSkan 1 . 86
A.1.15 Baltic Cable . 87
A.1.16 Directlink 1, 2 & 3 . 87
A.1.17 Murraylink . 87
A.1.18 Nelson River Bipole 1 – Pole 1 Valves, valve cooling and valve controls. 87
A.1.19 Nelson River Bipole 1 – Pole 2 Valves and valve cooling . 87
A.1.20 Nelson River Bipole 1 and 2 – Smoothing reactors . 88
A.1.21 Basslink . 88
A.1.22 Trans Bay Cable . 88
A.1.23 East South Interconnector II (Upgrade – Power capability enhancement
2 000 MW to 2 500 MW) – in 2006 . 88
A.1.24 Rihand Dadri HVDC refurbishment . 88
A.1.25 Gezhouba-Shanghai ±500 kV HVDC project . 89
A.1.26 Tian-Guang ±500 kV HVDC project . 89
A.1.27 Ormoc-Naga 344 kV HVDC project . 89
A.1.28 Luchaogang-Shengsi ±50 kV HVDC project . 89
A.2 Back-to-back HVDC . 90
A.2.1 Blackwater . 90
A.2.2 Châteauguay . 90
A.2.3 Highgate . 90
A.2.4 Eel river . 90
A.2.5 Madawaska . 90
A.2.6 Rapid city . 91
A.2.7 Vindhyachal HVDC refurbishment . 91
A.2.8 Welsh HVDC converter station . 91
A.3 Multiterminal – Quebec New England multiterminal DC (MTDC) . 91
Annex B (informative) Replacement of LCC station with VSC station . 92
B.1 General . 92
B.1.1 Overview . 92
B.1.2 Line commutated converter . 92
B.1.3 Voltage sourced converters . 92
B.1.4 Comparison between LCC and VSC HVDC converters . 92

– 6 – IEC TR 63463:2024 © IEC 2024
B.1.5 Replacement of LCC station with VSC station . 93
B.1.6 Converter transformers . 94
B.1.7 Smoothing reactors. 95
B.1.8 DC switchgear . 95
B.1.9 Control and protection . 95
B.1.10 AC filters . 95
B.1.11 DC filters . 96
B.1.12 DC measuring equipment . 96
B.1.13 Auxiliary supplies . 96
B.1.14 Valve cooling . 96
Bibliography . 97

Figure 1 – Typical lifetime of systems/equipment in HVDC stations . 18
Figure 2 – Typical equipment performance curve . 26
Figure 3 – Example of valve and control system refurbishment . 54
Figure 4 – Interfaces between HVDC C&P, VBE and thyristor valves . 71
Figure 5 – Typical refurbishment sequence and outage time . 75

Table 1 – HVDC equipment lifetimes (typical) . 19
Table 2 – Environmental issues associated with various HVDC equipment and
mitigation techniques . 64
Table 3 – List of possible system studies to be conducted in case of HVDC
refurbishment . 66
Table 4 – List of various typical studies/design carried out for refurbishment of HVDC . 68
Table B.1 – Comparison between LCC and VSC converters . 92

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LIFE EXTENSION GUIDELINES FOR HVDC CONVERTER STATIONS

FOREWORD
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IEC TR 63463 has been prepared by technical committee 115: High Voltage Direct Current
(HVDC) transmission for DC voltages above 100 kV. It is a Technical Report.
The text of this Technical Report is based on the following documents:
Draft Report on voting
115/339/DTR 115/353/RVDTR
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Report is English.

– 8 – IEC TR 63463:2024 © IEC 2024
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INTRODUCTION
In today's complex environment, energy players face growing demands to improve energy
efficiency while reducing costs. Energy shortages and increased ecological awareness have
resulted in great expectations for grid stability and reliability. Utilities and industries are
supposed to find eco-efficient solutions to maintain secure, safe and uninterrupted operations.
A number of regulatory changes in the electricity market have led to increased efforts by utilities
and grid operators for optimized utilization of their existing networks with respect to technical
and economic aspects. As the electric power transmission system ages, the topics of life
assessment and life extension have become predominant concerns. At the same time, cost
pressures have increased the desire to minimize maintenance. The goals of minimum
maintenance and extended life are often diametrically opposed.
The concept of simple replacement of power equipment in the system, considering it as weak
or a potential source of trouble, is no longer valid in the present scenario of financial constraints.
Today the paradigm has changed and efforts are being directed to explore new approaches and
techniques of monitoring, diagnosis, life assessment and condition evaluation, and possibility
of extending the life of existing assets.
A major challenge for grid operators worldwide is to ensure sufficient power with quality and
reliability. In this regard high voltage direct current (HVDC) systems play a major role in bulk
power transmission, system stability, integrating remote renewables and ride through of
disturbances. Therefore, HVDC systems represent an indispensable part of the electricity grid
in the countries where they are installed.
HVDC has been in commercial use since 1954, and most of the systems are still in operation.
However, the early mercury arc valve systems have been phased out and replaced by thyristor
valves. This has extended the life of many of the early systems, but the thyristor based systems
are also approaching an age where the thyristor valves are likely to require replacement or
refurbishment. Operation and maintenance issues of these ageing systems have become a
challenge. The situation is further complicated by the fact that all of the HVDC systems are
custom built by a relatively small number of original equipment manufacturers (OEM). The
HVDC manufacturers have supplied several different generations of equipment and these
differences are considered in any life extension assessment.
One major challenge in any refurbishment project is proprietary equipment. Most of the HVDC
equipment is composed of unique devices for which replacement/refurbishment by other
manufacturers is very difficult. For example, when planning to replace components of a thyristor
valve, it is more likely to be only supplied by the original manufacturer which will drive the cost
up for such replacement. However, this is still preferred if other component life is much longer,
as the alternative would be to replace the entire thyristor valves which will be costlier.
Proprietary equipment also causes difficulties in sharing details of equipment to other
prospective suppliers for the refurbishment projects.
It is assumed that regular maintenance of HVDC system/component/equipment is being done
by the owner as per the OEM recommendation as well as their maintenance practices. Further
it is assumed that they are familiar with equipment details and records of equipment failure.
They have knowledge of equipment behaviour, its characteristics and its impact on system
performance based on international standards. This document deals with life extension of the
HVDC converter station.
With the ageing of the equipment, measures to extend the equipment's life is considered by
utilities and grid operators. Renovation, modernization and life extension of HVDC stations is
usually one of the most cost-effective options for maintaining continuity and reliability of the
power supply to the consumers. Implementation of these life extension measures is
implemented with minimum impact on the HVDC system and the associated networks whilst
maintaining an acceptable level of reliability and availability. If life extension is not economical,
the systems are disposed of in an environmentally acceptable way. Also, consideration of
environmental issues is made prior to a life extension project to avoid any inadvertent
environmental damage.
– 10 – IEC TR 63463:2024 © IEC 2024
The cost of outages to carry out a refurbishment is considered as part of the overall cost. This
then dictates a greenfield option where a new converter station can be built and only short
switch overtime is required. An example of this is the Oklaunion Converter Station (CS) in the
USA, where the outage costs tipped the scale towards a greenfield versus a brownfield option
for refurbishment. The definition of the interfaces in the case of a brownfield project is critical
and more complicated than in a greenfield project.
Most utilities are interested in better understanding and projecting service life of HVDC
equipment to help manage risk; however, generic reliability data is inadequate for current
decision support needs. It is important to establish industry-wide equipment performance
databases to establish a broad-based repository of equipment performance data. With proper
care and analysis, this data can provide information about the past performance of equipment
groups and subgroups, and the factors that influence that performance. With enough data,
projections can be made about future performance. Both past and future performance
information can be useful for operations, maintenance, and asset management decisions.
However, for some components it is more difficult than most to determine the useful life and the
actual end of life failure modes. The thyristors themselves are an example, as they have been
around for some 35 or more years and yet are showing little sign of reaching end of life, except
where some design or quality issues have been uncovered.
Life-extension involves any of the following actions:
– Refurbishing the systems or subsystems,
– Selectively replacing ageing components,
– Combination of the above.
In some cases where life extension is not economically feasible, a greenfield replacement can
be considered.
The following steps can be taken to arrive at a decision:
– Review the past performance of the major HVDC equipment and systems.
– Identify the future performance issues associated with the ageing of special components
of the HVDC systems. The equipment that has not shown performance issues in the past
but is still required during life extension, is also considered.
– Determine economic life of various components in the converter station and for making
replacement versus life extension decisions. The consideration of economic life will
include capital cost, reliability and availability, cost of maintenance and the cost of
outages and power losses.
– The usable life of a refurbishment is likely in the average of 15 to 20 year range whereas
a greenfield option is likely 30 to 40 years and this can be factored into the evaluation
but it is recognized that some components can have a different year range.
One way of going about this activity could be to develop criteria, weightings and methodology
for determining near-term action and forecasting the technical and financial effect due to system
ageing. This follows an approach based on condition replacement cost and importance of the
equipment and components. Assessment of condition parameters could be in terms of
equipment age, technology, service experience (e.g. after sales service quality, maintenance
costs) and future performance, individual failure rates, and so on. A viable duration for the life
extension is determined and usually 15 to 20 years is achievable. Longer durations are more
difficult to assess with any degree of accuracy.
Evaluation of the possibility of extending the service life of electrical equipment is a techno-
economic compromise which can lead to "run-refurbish-replace" decisions. Once the expected
service life period has expired, refurbishment of such equipment falls within the life extension
program.
The investment at initial stage is very capital intensive to the utility concerned, as the devices
to be installed in the system for residual life assessment (RLA) and condition evaluation purpose,
are very costly. However, the decision to refurbish or to replace are generally done based on
the study of comparable costs and benefits over the same potential life time of the asset.
Therefore, it can be concluded that the need for life extension and replacement of equipment
in HVDC system arises due to:
– Arresting the deterioration in performance,
– Improving the availability, reliability, maintainability, efficiency and safety of the
equipment,
– Regaining lost capacity,
– Extending the useful life beyond originally designed life of 30 to 40 years,
– Saving investment on new equipment,
– Not having availability of new spares due to obsolescence.
These objectives help utilities as follows:
– design refurbishment strategies for their existing HVDC systems to extend equipment
life,
– evaluate O&M and reliability performance improvement strategies for their existing
HVDC systems,
– provide a guideline for determining economic life of various components in the converter
station and for making replacement versus life extension decisions. The consideration
of economic life are generally capital cost, reliability and availability, cost of maintenance
and the cost of power losses.
In order to achieve above objectives this document covers primarily following aspects:
– Key factors/reasons driving need for replacement work e.g.: system concerns such as
relevance of link. Technical and commercial feasibility efficiency of the refurbishment
planned.
– Failure or life degradation of equipment in the HVDC station.
– Critical equipment or critical interface points in the HVDC station.
– Planning of replacement work: Procurement – utility approach for procurement
(OEM/multiple vendor) and reasons for adoption based on type of equipment.
– Plan of execution – scope definition, preparation of technical specification, existing
system dat
...