IEC TS 63042-201:2018

IEC TS 63042-201 ®
Edition 1.0 2018-12
TECHNICAL
SPECIFICATION
colour
inside
UHV AC transmission systems –
Part 201: UHV AC substation design
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IEC TS 63042-201 ®
Edition 1.0 2018-12
TECHNICAL
SPECIFICATION
colour
inside
UHV AC transmission systems –
Part 201: UHV AC substation design

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.240.01; 29.240.10 ISBN 978-2-8322-6330-3

– 2 – IEC TS 63042-201:2018 © IEC 2018
CONTENTS
FOREWORD . 6
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 UHV AC substation requirement . 10
4.1 General requirement . 10
4.2 System demands . 10
4.3 Operation and maintenance requirements . 11
4.4 Construction requirements . 11
4.5 Site condition . 11
4.6 Environmental impact. 12
4.7 Economy . 12
5 Bus scheme and feeder connection . 12
5.1 General . 12
5.2 Scheme at high-voltage side of main transformer . 13
5.3 Scheme at intermedium-voltage side of main transformer . 14
5.4 Scheme at low-voltage side of main transformer . 14
5.5 System neutral earthing mode of a UHV AC substation . 15
6 Selection of equipment and conductors . 16
6.1 General . 16
6.1.1 Voltage . 16
6.1.2 Rated current . 16
6.1.3 Rated frequency . 16
6.2 Basic requirements . 16
6.2.1 Electrical requirements . 16
6.2.2 Mechanical requirements . 17
6.2.3 Environmental conditions . 17
6.3 Transformer . 18
6.4 UHV shunt reactor and neutral-earthing reactor . 19
6.5 UHV switchgear . 19
6.6 UHV circuit breaker . 20
6.7 UHV disconnector . 20
6.8 UHV earthing switch for maintenance . 21
6.9 High-speed earthing switch . 22
6.10 UHV current transformer . 22
6.11 UHV voltage transformer . 22
6.12 UHV surge arrester . 23
6.13 Reactive power compensation device for low voltage side of UHV
transformer . 23
6.14 UHV bushing . 23
6.15 UHV insulator . 24
6.16 UHV conductor. 24
6.16.1 General . 24
6.16.2 Conductor type . 24
6.16.3 Selection of current-carrying capacity (cross-section) . 25
6.16.4 Corona and radio interference . 25
6.16.5 Mechanical strength. 26

7 Equipment layout . 26
7.1 General requirement of equipment layout . 26
7.1.1 General . 26
7.1.2 Optimization of substation layout . 26
7.1.3 Seismic performance . 26
7.1.4 Construction, serviceability and reliability and failure response ability. 26
7.2 Minimum clearances . 27
7.2.1 Normal environmental conditions . 27
7.2.2 Minimum clearances in air-voltage range . 27
7.3 Electromagnetic environment . 27
7.3.1 Electrostatic induction mitigation design . 27
7.3.2 Magnetic induction mitigation design . 28
7.3.3 Audible noise mitigation design . 28
7.4 Selection of switchgear equipment . 29
7.5 Switchgear Installations layout . 29
7.5.1 General . 29
7.5.2 Location arrangement of switchgear . 29
7.5.3 Basic arrangement of surge arresters . 30
7.5.4 Optimal gas-insulated busbar (GIB) layout and length . 30
7.5.5 Utilization of working space for substations . 30
7.6 Protection against direct lightning strike . 31
7.7 Earthing systems . 31
7.7.1 General considerations . 31
7.7.2 Multiple point earthing method for GIS . 32
7.8 Seismic design . 33
7.8.1 General . 33
7.8.2 Basic seismic design . 33
7.8.3 Special seismic performance for UHV AC substation equipment . 34
8 Control, protection and communication . 35
8.1 General . 35
8.2 Control system . 35
8.3 Relay protection . 36
8.3.1 General . 36
8.3.2 Duplicated configuration of UHV AC equipment relay protection . 36
8.3.3 UHV transformer protection . 36
8.4 Communication . 37
8.5 Electromagnetic compatibility requirements for control and protection

equipment . 37
9 DC and AC auxiliary power supply system . 38
9.1 General . 38
9.2 DC power supply system . 38
9.3 AC auxiliary power supply system . 38
9.4 AC uninterruptible power supply (UPS) system . 39
10 UHV gantry, support and foundation design . 39
10.1 UHV gantry and support design . 39
10.1.1 General . 39
10.1.2 Load and combination of loads . 39
10.1.3 Detailing requirements . 40
10.2 GIS or MTS foundation design . 41

– 4 – IEC TS 63042-201:2018 © IEC 2018
Annex A (informative) Load combination of UHV AC equipment . 43
Annex B (informative) Specification of UHV AC equipment and conductor . 44
Annex C (informative) 1 000 kV outdoor overhead flexible conductor for UHV AC
substations in China . 46
C.1 General . 46
C.2 Environmental conditions . 46
C.3 Current-carrying capacity and thermal stability check . 46
C.3.1 Current-carrying capacity check . 46
C.3.2 Thermal stability check . 47
C.4 Determination of bundle spacing . 48
C.4.1 General . 48
C.4.2 Calculation of maximum electric field strength around conductor . 48
C.5 Corona inception voltage . 49
C.6 Electric field strength on ground caused by electrostatic induction . 50
Annex D (informative) Corona noise reduction measures of a UHV AC substation
conductor under the rainy condition in Japan . 52
D.1 Basic concept of corona noise reduction . 52
D.2 Structure design of UHV AC substation conductor . 52
D.3 Design criteria of partial discharge on UHV AC substation conductor . 54
D.4 Corona noise measurement of the entrance in UHV AC test station . 54
Annex E (informative) Typical examples of items to be considered to select switchgear

type . 56
Annex F (informative) Standards related to seismic design . 58
F.1 Typical seismic guide and standards . 58
F.2 Comparison of main items among the seismic standards . 58
Bibliography . 59

Figure 1 – Birds eye view of a typical UHV AC substation . 10
Figure 2 – Double busbar (DB) with or without bus section connection . 13
Figure 3 – One-and-a-half circuit breaker (OHCB) . 14
Figure 4 – Two-circuit breaker (2CB) . 14
Figure 5 – Example diagram of a bus scheme and feeder connection . 15
Figure 6 – Typical configuration of UHV gas-insulated switchgear and crane location . 31
Figure 7 – Earthing methods . 33
Figure 8 – Flow chart for seismic qualification . 34
Figure 9 – Example of continuous UHV gantry and independent gantry . 41
Figure 10 – GIS foundation forms . 42
Figure C.1 – Relationship between maximum electric field strength and bundle spacing . 49
Figure C.1 – Layout plan of main transformer incoming lines . 51
Figure D.1 – Conductor design of UHV AC substation . 53

Table 1 – Comparison of a four-legged reactor and HSES . 22
Table 2 – Comparison of conductors . 25
Table A.1 – Example of load combination for UHV AC equipment . 43
Table B.1 – UHV voltage specification . 44
Table B.2 – Specification of UHV short-circuit current . 44

Table B.3 – Noise specification . 44
Table B.4 – Surge arrester specification applied in different countries . 45
Table C.1 – Current-carrying capacity of bundle conductor . 47
Table C.2 – Corona inception voltage of conductor . 50
Table D.1 – Estimated values of corona noise of UHV AC transmission line . 53
Table D.2 – Design criteria of partial discharge on UHV AC substation conductor . 54
Table D.3 – Results of corona noise measurements and average value of corona noise . 55
Table E.1 – The principal technology designs for substations (CIGRE TB 570) . 56
Table E.2 – Typical examples of items to be considered to select switchgear type . 57
Table F.1 – Typical seismic guide and standards . 58
Table F.2 – Comparison of main items among seismic standards . 58

– 6 – IEC TS 63042-201:2018 © IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
UHV AC TRANSMISSION SYSTEMS –
Part 201: UHV AC substation design

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
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The main task of IEC technical committees is to prepare International Standards. In
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specification when
• the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts, or
• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC TS 63042-201, which is a technical specification, has been prepared by IEC technical
committee 122: UHV AC transmission systems.

The text of this Technical Specification is based on the following documents:
Enquiry draft Report on voting
122/64/DTS 122/71A/RVDTS
Full information on the voting for the approval of this technical specification can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 63042 series, published under the general title UHV AC
transmission systems, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
 reconfirmed,
 withdrawn,
 replaced by a revised edition, or
 amended.
A bilingual version of this publication may be issued at a later date.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 8 – IEC TS 63042-201:2018 © IEC 2018
UHV AC TRANSMISSION SYSTEMS –
Part 201: UHV AC substation design

1 Scope
This part of 63042, which is a Technical Specification, provides common rules for the design
of substations with the highest voltages of AC transmission systems exceeding 800 kV, so as
to provide safety and proper functioning for the intended use.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60038:2009, IEC standard voltages
IEC 60044 (all parts), Instrument transformers
IEC 60059:1999, IEC standard current ratings
IEC 60059:1999/AMD1:2009
IEC 60071-1:2006, Insulation co-ordination – Part 1: Definitions, principles and rules
IEC 60071-1:2006/AMD1:2010
IEC 60071-2, Insulation co-ordination – Part 2: Application guide
IEC 60076 (all parts), Power transformers
IEC 60068-3-3, Environmental testing – Part 3: Guidance – Seismic test methods for
equipments
IEC 60137, Insulated bushings for alternating voltages above 1000 V
IEC 60168, Tests on indoor and outdoor post insulators of ceramic material or glass for
systems with nominal voltages greater than 1000 V
IEC 60196:2009, IEC standard frequencies
IEC 60255-26, Measuring relays and protection equipment – Part 26: Electromagnetic
compatibility requirements
IEC TS 60479-1, Effects of current on human beings and livestock – Part 1: General aspects
IEC 60721-2-4, Classification of environmental conditions – Part 2-4: Environmental
conditions appearing in nature – Solar radiation and temperature
IEC TS 60815 (all parts), Selection and dimensioning of high-voltage insulators intended for
use in polluted conditions
IEC 60865 (all parts), Short-circuit currents

IEC 60871 (all parts), Shunt capacitors for a.c. power systems having a rated voltage
above 1 000 V
IEC 60909 (all parts), Short-circuit currents in three-phase a.c. systems
IEC TS 61463, Bushings – Seismic qualification
IEC 61850 (all parts), Communication networks and systems for power utility automation
IEC 61936-1:2010, Power installations exceeding 1 kV a.c. – Part 1: Common rules
IEC 61936-1:2010/AMD1:2014
IEC 62231, Composite station post insulators for substations with AC voltages greater
than 1 000 V up to 245 kV – Definitions, test methods and acceptance criteria
IEC 62271-100, High-voltage switchgear and controlgear – Part 100: Alternating current
circuit-breakers
IEC 62271-102, High-voltage switchgear and controlgear – Part 102: Alternating current
disconnectors and earthing switches
IEC 62271-207, High-voltage switchgear and controlgear – Part 207: Seismic qualification for
gas-insulated switchgear assemblies for rated voltages above 52 kV
IEC TR 62271-300, High-voltage switchgear and controlgear – Part 300: Seismic qualification
of alternating current circuit-breakers
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
UHV AC
highest voltage of AC transmission system exceeding 800 kV
Note 1 to entry: UHV stands for "ultra high voltage".
3.2
high-voltage side of transformer
highest voltage among two or three voltages on each side of the main transformer
3.3
intermedium voltage side of transformer
second highest voltage among three voltages on each side of the main transformer
3.4
low-voltage side of transformer
lowest voltage among two or three voltages in the apparatus or installation
Note 1 to entry: In this document, the definition is modified as the lowest voltage among two or more voltages on
each side of main transformer.

– 10 – IEC TS 63042-201:2018 © IEC 2018
4 UHV AC substation requirement
4.1 General requirement
The UHV AC substation should withstand the electrical, mechanical, climatic and
environmental influences anticipated on site.
In the design of the UHV AC substation, several factors should be taken into account: system
demands, operation and maintenance requirements, construction requirements, site condition,
environmental impact and economy.
To meet the requirements above, the design should also be performed in consideration of the
following characteristics of the UHV AC substation:
• high importance of the UHV AC substation;
• high transmission capacity;
• high overvoltage;
• high secondary arc current;
• high electric and magnetic field strength;
• large dimension and weight of the UHV AC equipment;
• large dimension of the UHV AC substation.
A typical design of a UHV AC substation is shown in Figure 1.

Figure 1 – Bird's-eye view of a typical UHV AC substation
4.2 System demands
The design of the UHV AC substation should meet the AC transmission system demands,
including the following items:

a) reliability: the bus scheme and feeder connection, equipment and control protection
system of the UHV AC substation should be adopted to meet the requirements of reliability,
considering the importance of the UHV AC substation in the AC transmission systems.
b) availability: the selection of the bus scheme and feeder connection, the type and
parameters of equipment, equipment layout, control protection and communication system
should meet the demands of AC transmission system scale and parameters in the steady-
state and transient-state and the possibility of extension (if required). Especially, the
demands of the AC transmission system access should be taken into consideration in the
design of equipment layout.
c) flexibility: the convenience of switching feeders such as a bank of transformers or a
transmission line, switching devices such as circuit breakers, busbars and their relay
protection devices in case of maintenance, and the transition from the initial bus scheme
and feeder connection to the final bus scheme and feeder connection, should be taken
into consideration in the design of bus scheme and feeder connection as well as
equipment layout.
4.3 Operation and maintenance requirements
The UHV AC substation with high applied voltage and large dimension plays a significant role
in AC transmission systems, which makes the operation and maintenance of these
substations very severe. The design of the UHV AC substation should meet the requirements
of operation and maintenance, including the following items:
a) The type of bus scheme and feeder connection and equipment should meet the
requirements of operation and maintenance as much as possible on premise of meeting
the system demands.
b) The design of the UHV AC substation should limit the safety distance and electric field
strength to a permissible value in order to ensure the operator safety and to meet the
requirements of a daily operation and maintenance, even though the applied voltage of the
UHV AC substation is high.
c) The design of the earthing system should meet the requirements of a daily operation and
maintenance. Especially, the step potential and touch potential of the earthing system
should be limited to permissible value.
d) Control, protection and communication system should meet the requirements of the
system architecture and operation mode of AC transmission systems.
4.4 Construction requirements
Large and heavy equipment complicates the construction of the UHV AC substation. The
design of the UHV AC substation should meet the requirements of construction, including the
following items:
a) The equipment layout and the distance between equipment should meet the requirements
of transportation, lifting and installation of the equipment.
b) When selecting the UHV conductors, the effort involved in the structural design shall be
taken into account, too, besides the electrical properties such as current-carrying capacity,
thermal stability, corona effect, etc.
c) The transportation condition should meet the requirements for large equipment transport.
d) The construction measures should be adopted to meet the requirements of the UHV AC
equipment's foundation. Structure construction should be used in order to avoid the
temperature cracks generated by the hydration heat impact in mass concrete construction.
4.5 Site condition
The design of the UHV AC substation should meet the requirements of the site condition,
including the following items:

– 12 – IEC TS 63042-201:2018 © IEC 2018
a) Hydrological and geological condition. The UHV AC substation should be located in a
stable geological region, and the hydrological and geological influence should be
considered.
b) Meteorological condition. The type, parameters, and configuration of the UHV AC
equipment and conductor should adapt to the meteorological condition such as
temperature, humidity, atmospheric pressure, wind velocity, etc.
c) Seismic conditions. The UHV AC substation should avoid being located in a seismically
unfavourable site, and electrical facilities should meet the anti-seismic requirements.
d) Altitude. The safety distance, current-carrying capacity of the conductor, and external
insulation of the equipment should be corrected according to the altitude on site.
4.6 Environmental impact
The design of the UHV AC substation should reduce the environmental impact, including the
following items:
a) Audible noise. The type, parameters, and configuration of the UHV AC equipment and
conductor should limit the audible noise strength on the substation boundary that is
specified by local regulations to a permissible value.
b) Electric and magnetic field. The type, parameters, and configuration of the UHV AC
equipment and conductor should limit the electric and magnetic field strength to a
permissible value.
c) Radio Interference. The type, parameters, and configuration of the UHV AC equipment
and conductor should limit the radio interference strength to a permissible value.
d) The influence of the potential rising of the earthing system on the outside of the UHV AC
substation. The potential rising of the earthing system should avoid being transferred to
the outside of the UHV AC substation through metal pipes or cables in the design of the
earthing system.
e) Carbon footprint. The design should limit the carbon footprint of the substation (e.g.
reduce leakage of total volume of SF ).
4.7 Economy
The design of the UHV AC substation should strike a balance between performance and cost
based on the life-cycle cost analysis, on the premise of meeting functional requirements.
5 Bus scheme and feeder connection
5.1 General
The basic purpose of a chosen bus scheme and feeder connection is to facilitate the
operational functions of a substation inside an electrical network. In the past, maintainability
and accessibility of high-voltage equipment was very important due to the requirements for
frequent maintenance. Different types of circuit breaker design and also the different types of
operating mechanisms required regular maintenance with short intervals. These requirements
meant that various configurations and arrangements of substations were developed to isolate
the circuit breaker and current transformer in a complete bay for maintenance while ensuring
availability of supply on adjacent equipment. Disconnectors were required to deal with safety
requirements and provide physical isolation during long-term maintenance activities.
Because the latest development in switchgear is aimed at ever longer maintenance intervals,
the importance of maintainability in the design of switchgear has changed. At the same time,
today’s society is getting more and more dependent on electric power supply for all its
functions. This results in less tolerance towards quality of power supply issues and black-outs,
which will require designers to put more emphasis on high security (i.e. fault tolerance) and
availability requirements for substations, especially for UHV AC transmission systems as
backbone system.
Summarizing, bus scheme and feeder connection of high voltage substations are strongly
influenced by many factors such as operational requirements, security standards, availability,
and maintainability, the need for sectionalizing, control and protection systems and
regulations. The bus scheme and feeder connection of a UHV AC substation should be
determined after comparison of technology and economy according to the importance of the
substation in transmission system considering the factors mentioned above.
The configuration for a particular substation depends on its position within a network and also
its relative importance.
Because of the generally high importance of UHV AC substations, the following configurations
are preferred:
• double busbar (DB);
• one-and-a-half circuit breaker (OHCB);
• two-circuit breaker (2CB).
5.2 Scheme at high-voltage side of main transformer
The DB with a coupler bay as shown in Figure 2 is a substation in which the lines and
transformers are connected to either of the two busbars by means of selector disconnectors.
The DB is particularly suitable for highly interconnected power networks in which switching
flexibility is important and multiple supply routes are available. The coupler circuit breaker
allows the possibility of keeping half of the station in service following a fault on the busbar, a
busbar disconnector or any feeder circuit breaker. The configuration provides flexibility by
allowing each circuit to be connected to either of the two busbars. It is also possible to move
circuits from one busbar to the other while they are energized. Additional flexibility can be
provided by adding sectionalised disconnectors into each busbar.
Using a bus section connection arrangement, a higher reliability is provided. This
arrangement has the same characteristics and functionality of DB but it is recommended for
use when there is a requirement to keep a high number of circuits in service during
maintenance or repair of the circuit breaker or the busbar disconnectors.

NOTE The single line diagram only shows circuit breaker and busbar.
Figure 2 – Double busbar (DB) with or without bus section connection
The OHCB as shown in Figure 3 is a double busbar substation where, for two circuits, three
circuit-breakers are connected in series between the two busbars, the circuits being
connected on each side of the central circuit-breaker. The OHCB is particularly suitable for
substations handling large amounts of power, such as those associated with generating
stations, and for networks which comprise mainly radial circuits with few mesh connections.
The OHCB does not have any separate bus-coupler circuits. Each circuit breaker connecting
is acting as a bus-coupler. The design of the bus zone and circuit breaker failure protection
systems is simpler than the multiple busbar configurations with selector disconnectors as the
systems do not need to select which circuit breakers to trip in response to a busbar fault or a
circuit breaker fail situation.

– 14 – IEC TS 63042-201:2018 © IEC 2018

NOTE The single line diagram only shows circuit breaker and busbar.
Figure 3 – One-and-a-half circuit breaker (OHCB)
The 2CB as shown in Figure 4 is a double busbar substation where the selectors are circuit-
breakers. The 2CB is recommended for substations where the security of supply is particularly
important. In addition, bus section connection in 2CB may strengthen the reliability of the
substation. The 2CB is also more flexible than the OHCB. The configuration provides
flexibility by allowing each circuit to be connected to either of the two busbars. It is also
possible to move circuits from one busbar to the other while they are energized.

NOTE The single line diagram only shows circuit breaker and busbar.
Figure 4 – Two-circuit breaker (2CB)
5.3 Scheme at intermedium-voltage side of main transformer
The following configurations are preferred at the intermedium voltage side of main transformer:
• double busbar (DB);
• one-and-a-half circuit breaker (OHCB);
• two circuit breaker (2CB).
5.4 Scheme at low-voltage side of main transformer
The low-voltage side of main transformer and its rated voltage should be determined
according to the following:
• system needs;
• transformer design and manufacturing;
• load configuration (including reactive compensation, feeders, etc.) at the low-voltage side
of the main transformer.
If the low-voltage side of the main transformer will be connected to one or more feeders,
single busbar layout with bus section connection may be employed. If the low-voltage side of
the main transformer is connected to reactive compensation equipment only, the main
transformer together with the busbar and connected equipment may be laid out as separate
units.
According to load allocation at low voltage side of the main transformer and application of
switchgear, a set or more of busbars can be installed at the low voltage side of each bank of
transformers. To improve the power transmission reliability of the high-voltage and
intermedium-voltage sides of the main transformer and reduce the influe
...