IEC TR 61788-20:2014

IEC TR 61788-20 ®
Edition 1.0 2014-07
TECHNICAL
REPORT
Superconductivity –
Part 20: Superconducting wires – Categories of practical superconducting
wires – General characteristics and guidance

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IEC TR 61788-20 ®
Edition 1.0 2014-07
TECHNICAL
REPORT
Superconductivity –
Part 20: Superconducting wires – Categories of practical superconducting

wires – General characteristics and guidance

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
R
ICS 29.050 ISBN 978-2-8322-1779-5

– 2 – IEC TR 61788-20:2014 © IEC 2014
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Categories of practical SC wires . 7
5 Technical sheet assisting in the specification and the use of practical SC wires. 8
6 Class of practical SC wires . 8
7 Product parameters . 8
8 Joints . 8
9 Appearance . 8
10 Quality assurance . 8
11 Test methods . 8
12 Inspection . 9
13 Shipping label . 9
Annex A (informative) Structural characteristics of practical SC wires . 10
A.1 General . 10
A.2 Overview of SC materials . 10
A.3 Overview of functional components . 10
A.3.1 Matrix materials . 10
A.3.2 Stabilizer . 11
A.3.3 Reinforcing component . 11
A.3.4 Insulation . 11
Annex B (informative) Classes of practical SC wires . 13
B.1 Nb-Ti group . 13
B.2 Nb Sn group . 13
B.3 MgB . 14
B.4 BSCCO group . 15
B.5 REBCO group . 15
Annex C (informative) Technical information assisting in the specification and use of
practical SC wires . 17
C.1 General . 17
C.2 Product parameters . 17
C.3 Appearance . 17
C.4 Quality assurance . 17
C.5 Test methods . 17
C.6 Technical record . 18
Bibliography . 19

Table B.1 – Constituents composing the Nb-Ti group SC wires . 13
Table B.2 – Constituents composing the Nb Sn group SC wires . 14
Table B.3 – Constituents composing the MgB SC wires . 14
Table B.4 – Constituents composing the BSCCO SC wires . 15
Table B.5 – Constituents composing REBCO SC wires . 16

– 4 – IEC TR 61788-20:2014 © IEC 2014
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SUPERCONDUCTIVITY –
Part 20: Superconducting wires –
Categories of practical superconducting wires –
General characteristics and guidance

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
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
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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
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC 61788-20, which is a technical report, has been prepared by IEC technical committee
90: Superconductivity.
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
90/335/DTR 90/344/RVC
Full information on the voting for the approval of this technical report can be found in the
report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 61788-20 series, published under the general title
Superconductivity, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

– 6 – IEC TR 61788-20:2014 © IEC 2014
INTRODUCTION
Superconducting (SC) wires are a central and often enabling technology of many important
industrial products. Consensus-based standards for SC wires greatly facilitate the creation of
procurement specifications, design and engineering of components, certification of quality,
description of operating devices, and generalization of use in industrial technologies.
The present technical report (TR IEC61788-20) provides a description of the general features
of practical SC wires. The practical low temperature superconducting (LTS) wires have been
used extensively in a variety of applications since the late 1960s. These applications include
magnetic resonance imaging magnets, research and accelerator magnets, and systems for
cutting-edge scientific research. High temperature superconductors (HTS), discovered in 1986,
allow operation of superconductor-based technologies with less expensive and more efficient
refrigeration systems. These new materials will provide wires that will enable new applications,
some of which may not be possible with LTS wires. Many fabrication routes and conductor
architectures are well established for superconducting wires, and these engineering routes
have a number of general characteristics that are fundamental to enabling industrial products.
Practical superconducting wires are those forms of SC wires that are nearly identical to other
common electrical conductors such as those made from copper or aluminium. The
appearance of low temperature superconductive wires is, for instance, very similar to
commercial electrical copper wires or tin-plated copper wires, because they are covered with
stabilization or reinforcing components consisting of metallic elements. Often practical SC
wires are supplied in long lengths on wire spools. As such, practical SC wires can be used in
products and applications almost interchangeably with common wires. The technical aspects
of superconductivity impose, however, certain considerations that might be taken into account
in specifications for procurement, design and engineering, testing and certification, quality
control, and other commerce. These aspects can be complicated, making practical SC wires
less accessible to the non-technical user despite the best efforts of SC wire suppliers to
market their products. This document intends to provide descriptions of the technical aspects
of practical SC wires in terms of simple general characteristics to assist in the specification
and use of superconducting wire products. It might be noted that this document gives some
general characteristics of practical SC wires at the present state, but not any type of
specifications for the wires or for the processing of the wire.
Thus the present technical report that provides general characteristics and guidance with
respect to practical SC wires is recommended as a first priority for both producers and users
of superconducting technology.

SUPERCONDUCTIVITY –
Part 20: Superconducting wires –
Categories of practical superconducting wires –
General characteristics and guidance

1 Scope
This part of IEC 61788, which is a technical report, provides general characteristics and
guidance on practical SC wires. Particular focus is given to the characteristics that are
different from those of ordinary copper and aluminium wires, since practical SC wires have
appearance nearly identical to common electrical wires and can be used interchangeably with
them. On the other hand, the practical SC wires are typically composite materials consisting
of several functional materials as described in Annex A.
Many forms of SC wires are described in Section 4 of IEC 60050-815, including single core
wires, multi-filamentary superconducting wires, composite superconductors and coated
conductors. These wires as well as others that might be described as monolithic composite
superconducting wires will be the focus in this technical report. A wire is considered as being
practical if it can be procured in sufficiently continuous lengths under ordinary commercial
transactions to build devices.
Conductors made of multiple wires, such as cables, for example, are not included in this
scope.
Since this report only addresses the characteristics of practical wires, other wires such as
prototype, test sample and developmental wires are not included in the scope of this technical
report.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60050 (all parts), International Electrotechnical Vocabulary (available at:
)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-815 apply.
4 Categories of practical SC wires
Industrially available SC materials are classified into two categories by IEC 60050-815. The
low temperature superconductors have a critical temperature less than 25 K. They are
typically in the Nb-Ti group and Nb Sn group, which is an intermetallic compound. The other
category consists of high temperature superconductors such as BSCCO and REBCO and the
intermetallic compound MgB . In the present document, the five types of SC wire based on
the aforementioned five superconductor materials may be prescribed as practical SC wires, of
which the additional details are mentioned in Annexes A and B. When a new superconducting

– 8 – IEC TR 61788-20:2014 © IEC 2014
material is industrialized into wire form in the future, the current general requirements should
be modified by introducing it as a new practical SC wire.
5 Technical sheet assisting in the specification and the use of practical SC
wires
General items to agree between the supplier and the customer at the time of contract or
purchase order are listed as follows. Except the recommended items mentioned here,
additional items providing for the specification are described in Annex C. The technical sheet
may be executed.
6 Class of practical SC wires
One of the practical SC wires described in Clause 4 may be specified.
Additional informative items are mentioned in Annex B.
7 Product parameters
– Dimension may be settled in terms of the diameter of the round wire or the width /
thickness of the rectangular wire together with the tolerance.
– Length and/or weight may be definitely settled.
– The necessity of insulation may be designated.
– The type of spooling may be designated.
– The shipping label designated in Clause 13 may be attached on the shipped product.
Additional informative items are mentioned in Annex C.
8 Joints
Unless otherwise agreed upon by a customer and a supplier, no joints may be made in the
completed wire. If joints are permitted within the wire, the customer and supplier are required
to agree on the quantity and properties of the joints.
9 Appearance
The appearance of the wire should be free from any imperfection not consistent with
commercial practice.
Additional informative items are mentioned in Annex C.
10 Quality assurance
A representative critical current value may be designated together with tolerance.
Additional informative items are mentioned in Annex C.
11 Test methods
Tests to determine conformance to requirements on product parameter and quality may be
performed according to the instruction of the document (see Bibliography).

12 Inspection
Unless otherwise specified in the contract or purchase order, the supplier may be responsible
for the performance of all inspection and test requirements specified.
Unless otherwise
...