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About this book

This CIGRE Green book on accessories for HV and EHV extruded cables covers relevant issues in cable system design, cable design, submarine cables including off shore generation connection. It provides comprehensive and unbiased information, essential recommendations and guidelines for design, installation, testing and maintenance of accessories to professionals through the exceptional expertise of the authors.

This publication is divided in two Volumes covering land and submarine applications, HVAC and HVDC systems, transitions from lapped cable systems to extruded cable systems, from OHL to UG cables and from cables to substations. It equips the reader with recommendations for testing, installation, maintenance, remaining life management. This Volume is dedicated to Components while Volume 2 deals with Land and Submarine AC/DC Applications.

The book compiles the results of the work achieved by several Working Groups and Task Forces of CIGRE Study Committee 21/B1, and Joint Working Groups and Joint Task Forces with other Study Committees. Many experts from Study Committees 21/B1 (Insulated Cables), 15/D1 (Materials and Emerging Test Techniques), 33/B3 (Substations), C3 (System Environmental Performance) and C4 (System Technical Performance) have participated in this work in the last 30 years in order to offer comprehensive, continuous and consistent outputs.

Table of Contents

Frontmatter

1. Compendium of Accessory Types Used for AC HV Extruded Cables

Abstract
Chapter 1 categorises the types of accessory designs available for use on HV cables with extruded insulation for ac transmission voltages of 60 kV (75.5 kV) and above. The typical types of extruded cable insulation being low density polyethylene (LDPE), high density polyethylene (HDPE), cross-linked polyethylene (XLPE) and ethylene propylene rubber (EPR).
Zensuke Iwata

2. A Guide to the Selection of Accessories

Abstract
The reliability and performance of a cable circuit is dependent in equal measures on the designs of the cable and accessory and on the skill and experience of the person who is assembling the accessory. The cable insulation is extruded in the factory under controlled process conditions using selected materials of high quality. It is equally important that the same quality measures are employed for the manufacture of the accessories in the factory and for their assembly on site onto the specially prepared cable.
Zensuke Iwata

3. Interfaces in Accessories for Extruded HV and EHV Cables

Abstract
Interfaces in joints and terminations of extruded HV cables have been identified as crucial parts. Some of the mechanisms related to ageing are not well understood. For this reason, a task force has been established to study the behaviour of interfaces in accessories for HV and EHV extruded cables. The scope was limited to non-bonded interfaces between solid insulating materials, but included the applied lubricants.
Henk Geene

4. Qualification Procedures for HV and EHV AC Extruded Underground Cable Systems

Abstract
IEC test requirements have evolved over the years from the component-based approach in IEC 840 to the system based approach. Accessories are considered together with the cable, in IEC 62067 Ed.1 and in the most recent edition of IEC 60840 Ed.3.
Jean Becker

5. Cable Accessory Workmanship on Extruded High Voltage Cables

Abstract
This Chapter 5 (Published as Cigré TB 476) covers workmanship associated with the jointing and terminating of AC land cables incorporating extruded dielectrics for the voltage range above 30 kV (Um = 36 kV) up to 500 kV (Um = 550 kV). Cigré TB 476 is a complement of Cigré TB 177 (See Chaps. 1 and 2), the recommendations of which are not questioned in this chapter. A short section covers general risks and skills, but the bulk of the chapter focuses on the specific Technical Risks and the associated skills needed to mitigate these risks. This is done for each installation phase. This Chapter is not an Instruction Manual, but rather gives guidance to the reader on which aspects needs to be carefully considered in evaluating the execution of the work at hand. The supplier’s Instruction Manual is considered the primary source of technical information. A section on skills assessment helps the qualification of jointers. Finally, attached appendices give samples of a certificate and QA documentation.
Kieron Leeburn

6. Guidelines for Maintaining the Integrity of Extruded Cable Accessories

Abstract
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.
Eugene Bergin

7. Feasibility of a Common, Dry Type Plug-in Interface for GIS and Power Cables above 52 kV

Abstract
Since 1986 the connection between GIS substations and cables has been managed by a dimensional standard establishing electrical and mechanical interchangeability between cable terminations and gas insulated metal enclosed switchgear.
Within this framework termination suppliers design their own components: insulator, stress cone (for the two available options inner cone and outer cone) and the connection inside the termination.
The responsibility limit between the switchgear manufacturer and the cable termination manufacturer is at the interface SF6/insulator.
Considering the large number of substations and planning difficulties due to the fact that the cable system is not usually defined at the time of switchgear manufacture, a joint working group has been set up by Cigré within committees B1 and B3. The group has to investigate the possibility of a standardised common interface insulator for the dry type and plug-in cable termination, which could be supplied independently from the remaining termination components.
Starting from review of GIS cable termination designs and actual installation practices for all voltage levels, the joint working group has studied:
  • Operational experience in common interface design, for medium voltage and for a specific utility
  • Constraints in terms of civil works, space, weight of cables and terminations
  • Compliance with standards
  • Implications of the common interface insulator for the market
  • Qualification requirements
  • Applicable range (voltage and size)
  • Estimated cost for testing and qualitative advantages of the common interface (financial benefit versus development and qualification costs was not evaluated)
  • New limits of responsibility (insulator/stress cone and insulator/SF6)
  • Market trend.
Taking into account all the above, as per the TOR of the group, WG B1-B3.33 advises Study Committees B1 and B3 to set up a new working group with the following Terms of Reference.
The Working group should recommend a functional design of an insulator with a common interface with the following scope of work:
  • Voltage is ≤ 145 kV AC
  • Current is ≤ 1000A, short circuit ≤ 40 kA 1 sec
  • Cross sections are ≤ 1000 mm2 Cu or 1600 mm2 Al
  • Technology has to be defined (inner or outer cone), with a detailed evaluation of technical advantages/disadvantages of the two technologies.
  • The number of sizes has to be defined; the short circuit current can be altered for the smallest sizes.
  • Dimensions of insulator components have to be defined (current connection, electrical design and properties, mechanical design and properties).
  • The type and dimension of the main current connection has to be defined
  • Consider the consequence of a termination failure.
  • Consider upgrading of the cable link for higher current loads.
  • Consider installation constraints, with a special focus on the basement dimensions.
  • The design has to meet the requirements of IEC 62271-209 and IEC 60840
  • The initial and cross qualification processes.
The stress cone design and material, the lubricant and the design of the compression device should be left to the discretion of the accessory manufacturer within the limits of the standardised cable terminations properties.
Cigré TB 303 and the work of WG B1.44 and WG B1.46 should be taken into account.
Pierre Mirebeau

8. Test Procedures for HV Transition Joints for Rated Voltages 30 kV up to 500 kV

Abstract
This chapter is the editorial and graphical revision of the Cigré TB 415, prepared by the WG B1.24 and published in June 2010.
Marco Marelli

9. Thermal Ratings of HV Cable Accessories

Abstract
On request of IEC TC 20 a Task Force TF 21(B1)-10 was launched by SC 21 in 2001 with the scope to review whether or not existing HV cable test specifications would appropriately specify and verify the crucial thermal and thermo-mechanical characteristics of accessories. TF B1-10 finished its work on schedule in 2003 with the following conclusions:
Henk Geene, Reinhard Schroth

10. Test Regimes for HV and EHV Cable Connectors

Abstract
The current IEC 61238-1-3 [1] standard applies to connectors for medium voltage (MV) cables up to 30 kV (Um = 36 kV). There is no IEC standard for connectors for cables for high voltage (HV) and extra high voltage (EHV) networks. The IEC standards for testing HV/EHV cable systems/accessories (IEC 60840 and IEC 62067 correspondingly) do not specify separate tests for qualifying only connectors. The task of CIGRE WG B1.46 was to propose test regimes for connectors for cables above 30 kV, with focus on larger conductor sizes typically used in HV/EHV cable systems.
Milan Uzelac

11. Standard Design of a Common, Dry Type Plug-in Interface for GIS and Power Cables up to 145 kV

Abstract
In many countries, the market trends are towards a commoditization of the high voltage cables lower or equal to 145 kV. IEC TC 17, in charge of the maintenance of IEC 62271-209 for “Cable connections for gas-insulated metal-enclosed switchgear for rated voltages above 52 kV” asked CIGRE to evaluate technically the feasibility of a common interface. A first joint Working Group B1–B3 was set up in 2010 and concluded that it is feasible to have a common interface for voltages up to 145 kV and a rated current ≤1000 A. See TB 605.
Pierre Mirebeau
Additional information