IEC TR 60493-3:2017

Guidelines for the statistical analysis of ageing test data - Part 3: Minimum specimen numbers at different test conditions with given experimental data

IEC TR 60493-3:2017(E) clarifies how a statistical analysis can be done with a small number of samples. This document will be useful when the accelerated test method is difficult to carry out, for example in cases where the dimensions of test specimens (including test devices) are very large in scale or the cost of test specimens is high. Testing is facilitated by enabling users to reduce the number of test specimens.

General Information

• Status: Published
• Publication Date: 10-May-2017
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 29.035.01 - Insulating materials in general
• Technical Committee: TC 112 - Evaluation and qualification of electrical insulating materials and systems
• Drafting Committee: WG 7 - TC 112/WG 7
• Current Stage: PPUB - Publication issued
• Start Date: 22-May-2017
• Completion Date: 11-May-2017

Standards Content (Sample)

IEC TR 60493-3 ®
Edition 1.0 2017-05
TECHNICAL
REPORT
colour
inside
Guidelines for the statistical analysis of ageing test data –
Part 3: Minimum specimen numbers at different test conditions with given
experimental data
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IEC TR 60493-3 ®
Edition 1.0 2017-05
TECHNICAL
REPORT
colour
inside
Guidelines for the statistical analysis of ageing test data –

Part 3: Minimum specimen numbers at different test conditions with given

experimental data
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.035.01 ISBN 978-2-8322-4299-5

– 2 – IEC TR 60493-3:2017 © IEC 2017
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms, definitions, symbols and conventions . 6
3.1 Terms and definitions . 6
3.2 Symbols . 6
3.3 Conventions . 7
4 Assumptions . 7
5 General considerations . 8
6 Probability calculation based on normal distributions . 10
6.1 General . 10
6.2 Calculations . 10
6.3 Estimated life at 90 °C (temperature difference is set to be 40 °C) . 12
6.3.1 Ideal case with σ = 0,05, 0,1, 0,2, 0,3 . 12
6.3.2 Test sample numbers of 20, 10, 5, 3 with σ = 0,05 . 13
6.3.3 Test sample numbers of 20, 10, 5, 3 with σ = 0,3 . 14
6.4 Estimated life at 50 °C (temperature difference is set to be 80 °C) . 15
6.4.1 Ideal case with σ = 0,05, 0,1, 0,2, 0,3 . 15
6.4.2 Test sample numbers of 20, 10, 5, 3 with σ = 0,05 . 16
6.4.3 Test sample numbers of 20, 10, 5, 3 with σ = 0,3 . 17

Figure 1 – Ageing time versus survival ratio . 9
Figure 2 – Arrhenius plot of failure time or scatter . 9
σ
Figure 3 – Temperature dependence of . 10
t
Figure 4 – Estimated life at 90 °C for the ideal case . 13
Figure 5 – Test sample numbers of 20, 10, 5, 3 with σ = 0,05 . 14
Figure 6 – Test sample numbers of 20, 10, 5, 3 with σ = 0,3 . 15
Figure 7 – Estimated life at 50 °C for the ideal case . 16
Figure 8 – Test sample numbers of 20, 10, 5, 3 with σ = 0,05 . 17
Figure 9 – Test sample numbers of 20, 10, 5, 3 with σ = 0,3 . 18

Table 1 – Symbols . 7

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
GUIDELINES FOR THE STATISTICAL ANALYSIS OF AGEING TEST DATA –

Part 3: Minimum specimen numbers at different test conditions
with given experimental data
FOREWORD
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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 TR 60493-3, which is a Technical Report, has been prepared by IEC technical
committee 112: Evaluation and qualification of electrical insulating materials and systems.
The text of this Technical Report is based on the following documents:
Enquiry draft Report on voting
112/384/DTR 112/389/RVDTR
– 4 – IEC TR 60493-3:2017 © IEC 2017
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 document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 60493 series, published under the general title Guidelines for the
statistical analysis of ageing test data, can be found on the IEC website.
Future standards in this series will carry the new general title as cited above. Titles of existing
standards in this series will be updated at the time of the next edition.
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
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INTRODUCTION
The objective of this document is to clarify how a statistical analysis can be done even with a
small number of samples.
When the scatter of data is sufficiently small, a statistical analysis should be possible.
Generally, a statistical analysis applies to a larger number of samples similar to ordinary
cases.
On the other hand, this document may be useful in clarifying how the scatter of a small
number of data points can be used to estimate "lifetime" when the number of specimens is
limited (e.g. around five) and there are few ageing conditions (e.g. two or three conditions).
Therefore, the aim is to document, for a small group of specimens with limited scatter of data,
whether or not it is possible to estimate characteristics such as lifetime within a certain
statistical error.
If such a simulation were available, it would be very helpful for users.
Manufacturers, for example, may prefer a new simplified, accelerated test method as an
alternative to their current traditional test methods. A new test method would be easier and
less expensive, especially if the specimens were small in size (dimension), although it may
not be as suitable for large specimen sizes or expensive materials or devices (such as
motors).
It would be very welcome if a statistical treatment method of this type, applying to a smaller
number of specimens, were defined.
Though inappropriate cases are anticipated, this document deals with cases where such
statistical treatment is appropriate.

– 6 – IEC TR 60493-3:2017 © IEC 2017
GUIDELINES FOR THE STATISTICAL ANALYSIS OF AGEING TEST DATA –

Part 3: Minimum specimen numbers at different test conditions
with given experimental data
1 Scope
This part of IEC 60493 clarifies how a statistical analysis can be done with a small
...