Electromechanical elementary relays - Part 2: Reliability

IEC 61810-2:2017 covers test conditions and provisions for the evaluation of endurance tests using appropriate statistical methods to obtain reliability characteristics for relays.
This document applies to electromechanical elementary relays considered as non-repaired items (i.e. items which are not repaired after failure).
This document does not cover procedures for electromechanical elementary relays where enhanced requirements for the verification of reliability apply.
This edition includes the following significant technical changes with respect to the previous edition:
- not only graphical but also numerical methods are added;
- reduction of number of samples in specified cases;
- new subclauses of confidence intervals are added;
- the WeiBayes approach is added to facilitate compliance tests (routine test) with lower effort;
- annexes have been restructured into an Annex A for data analysis (normative) and Annex B (informative) where various examples of the data analysis are given;
- the former Annex C has been incorporated into the modified Annex B;
- a new Annex C replaces the old Annex D.

Relais électromécaniques élémentaires - Partie 2: Fiabilité

L’IEC 61810-2:2017 couvre les conditions d’essai et les dispositions pour l’évaluation des essais d’endurance utilisant les méthodes statistiques appropriées pour obtenir les caractéristiques de fiabilité pour les relais.
Le présent document s’applique aux relais électromécaniques élémentaires considérés comme des entités non réparées (c’est-à-dire des entités qui ne sont pas réparées après défaillance).
Le présent document ne couvre pas les procédures d’essai relatives aux relais électromécaniques élémentaires lorsque des exigences renforcées pour la vérification de la fiabilité s’appliquent.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
- ajout de méthodes non seulement graphiques mais aussi numériques;
- réduction du nombre d’échantillons dans des cas spécifiés;
- ajout de nouveaux paragraphes relatifs aux intervalles de confiance;
- ajout de l’approche WeiBayes pour permettre une réalisation efficiente des essais de conformité (essai individuel de série);
- réorganisation des annexes en Annexe A (normative), dédiée à l’analyse des données et en Annexe B (informative), dans laquelle plusieurs exemples d’analyse des données sont présentés;
- insertion de l’ancienne Annexe C dans l’Annexe B modifiée;
- remplacement de l’ancienne Annexe D par une nouvelle Annexe C.

General Information

Status
Published
Publication Date
29-May-2017
Current Stage
PPUB - Publication issued
Start Date
30-May-2017
Completion Date
30-May-2017
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IEC 61810-2
Edition 3.0 2017-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electromechanical elementary relays –
Part 2: Reliability
Relais électromécaniques élémentaires –
Partie 2: Fiabilité
IEC 61810-2:2017-05(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 61810-2
Edition 3.0 2017-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electromechanical elementary relays –
Part 2: Reliability
Relais électromécaniques élémentaires –
Partie 2: Fiabilité
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.120.70 ISBN 978-2-8322-4388-6

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 61810-2:2017 © IEC 2017
CONTENTS

FOREWORD ........................................................................................................................... 4

INTRODUCTION ..................................................................................................................... 6

1 Scope .............................................................................................................................. 7

2 Normative references ...................................................................................................... 7

3 Terms and definitions ...................................................................................................... 7

3.21 Terms and definitions related to tests ................................................................... 10

4 General considerations .................................................................................................. 10

5 Test conditions .............................................................................................................. 11

5.1 Sample items ........................................................................................................ 11

5.2 Environmental conditions ...................................................................................... 12

5.3 Operating conditions ............................................................................................. 12

5.4 Test equipment ..................................................................................................... 13

6 Failure criteria ............................................................................................................... 13

7 Output data ................................................................................................................... 13

8 Analysis of output data .................................................................................................. 13

9 Presentation of reliability measures ............................................................................... 13

Annex A (normative) Data analysis ...................................................................................... 15

A.1 General ................................................................................................................. 15

A.2 Abbreviations ........................................................................................................ 15

A.3 Symbols and definitions ........................................................................................ 15

A.4 Weibull distribution ............................................................................................... 16

A.5 Procedure ............................................................................................................. 17

A.5.1 Graphical methods ......................................................................................... 17

A.5.2 Numerical methods ........................................................................................ 22

A.5.3 Confidence Intervals ...................................................................................... 23

A.5.4 WeiBayes Approach ...................................................................................... 25

Annex B (informative) Example of data analysis ................................................................... 28

B.1 Graphical methods case study (cumulative hazard plot) ........................................ 28

B.1.1 General ......................................................................................................... 28

B.1.2 Procedure of cumulative hazard plot .............................................................. 28

B.1.3 Example applied to life test data .................................................................... 30

B.2 Numerical methods case study (Weibull probability) .............................................. 33

B.2.1 General ......................................................................................................... 33

B.2.2 Distribution parameters .................................................................................. 33

B.2.3 Mean cycles to failure (MCTF) ....................................................................... 33

B.2.4 Value of B .................................................................................................. 34

B.2.5 Mean time to failure (MTTF) .......................................................................... 34

B.3 Confidence intervals case study ............................................................................ 34

B.3.1 General ......................................................................................................... 34

B.3.2 Interval estimation of β .................................................................................. 34

B.3.3 Interval estimation of η................................................................................... 35

B.3.4 Lower confidence limit for B10 ....................................................................... 35

B.3.5 Lower confidence limit for R .......................................................................... 36

B.4 WeiBayes case study ............................................................................................ 36

Annex C (informative) Statistical tables ................................................................................ 38

---------------------- Page: 4 ----------------------
IEC 61810-2:2017 © IEC 2017 – 3 –

C.1 Table of gamma function ....................................................................................... 38

C.2 Fractiles of the normal distribution ........................................................................ 38

Annex D (informative) Success run – Test without failures ................................................... 40

D.1 General ................................................................................................................. 40

D.2 Confidence level and minimum reliability ............................................................... 40

D.3 Example................................................................................................................ 41

Bibliography .......................................................................................................................... 42

Figure A.1 – An example of Weibull probability paper ........................................................... 18

Figure A.2 – An example of cumulative hazard plotting paper ............................................... 20

Figure A.3 – Plotting of data points and drawing of a straight line ........................................ 20

Figure A.4 – Estimation of distribution parameters ................................................................ 21

Figure B.1 – Estimation of distribution parameters ................................................................ 30

Figure B.2 – Cumulative hazard plots ................................................................................... 32

Figure B.3 – Type test versus WeiBayes analysed periodic test ............................................ 37

Table A.1 – Confidence levels for WeiBayes without failures ................................................ 26

Table B.1 – Worksheet for cumulative hazard analysis .......................................................... 28

Table B.2 – Example worksheet ............................................................................................ 31

Table B.3 – First twenty failures in this example ................................................................... 33

Table C.1 – Values of the gamma function ............................................................................ 38

Table C.2 – Fractiles of the normal distribution ..................................................................... 39

Table D.1 – Number of samples and life cycles ..................................................................... 41

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– 4 – IEC 61810-2:2017 © IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROMECHANICAL ELEMENTARY RELAYS –
Part 2: Reliability
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

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.

International Standard IEC 61810-2 has been prepared by IEC technical committee 94: All-or-

nothing electrical relays.

This third edition cancels and replaces the second edition published in 2011. This edition

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:
a) not only graphical but also numerical methods are added;
b) reduction of number of samples in specified cases;
c) new subclauses of confidence intervals are added;

d) the WeiBayes approach is added to facilitate compliance tests (routine test) with lower

effort;
---------------------- Page: 6 ----------------------
IEC 61810-2:2017 © IEC 2017 – 5 –

e) annexes have been restructured into an Annex A for data analysis (normative) and

Annex B (informative) where various examples of the data analysis are given;
f) the former Annex C has been incorporated into the modified Annex B;
g) a new Annex C replaces the old Annex D.
The text of this International Standard is based on the following documents:
FDIS Report on voting
94/415/FDIS 94/418/RVD

Full information on the voting for the approval of this International Standard 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.

This International Standard is to be used in conjunction with IEC 61649:2008.

A list of all parts in the IEC 61810 series, published under the general title Electromechanical

elementary relays, 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.

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.
---------------------- Page: 7 ----------------------
– 6 – IEC 61810-2:2017 © IEC 2017
INTRODUCTION

Within the IEC 61810 series of basic standards covering elementary electromechanical relays,

IEC 61810-2 is intended to give requirements and tests permitting the assessment of relay

reliability. All information concerning endurance tests for type testing have been included in

IEC 61810-1.

NOTE According to IEC 61810-1, a specified value for the electrical endurance under specific conditions (e.g.

contact load) is verified by testing 1 or 3 relays. None is allowed to fail. Within this document, a prediction of the

reliability of a relay is performed using statistical evaluation of the measured cycles to failure of a larger number of

relays (generally 10 or more relays).

This document is the base for IEC 61810-2-1 to determine reliability values for relays where

enhanced requirements for the verification of reliability (B and B ) apply.
10 10D

The technical committee responsible for dependability has developed IEC 61649 dealing with

Weibull-distributed test data. It contains both numerical and graphical methods for the

evaluation of Weibull-distributed data as well as WeiBayes estimation.

On the basis of this basic reliability standard, this document was developed. It comprises test

conditions and an evaluation method to obtain characteristic reliability values for

electromechanical elementary relays. The life of relays as non-repairable items is primarily

determined by the number of operations. For this reason, the reliability is expressed in terms

of mean cycles to failure (MCTF).

Commonly, equipment reliability is calculated from mean time to failure (MTTF) figures. With

the knowledge of the frequency of operation (cycling rate) of the relay within a piece of

equipment, it is possible to calculate an effective MTTF value for the relay in that application.

Such calculated MTTF values for relays can be used to calculate respective reliability,

probability of failure, and availability (e.g. MTBF (mean time between failures)) values for

equipment into which these relays are incorporated.

Generally, it is not appropriate to state that a specific MCTF value is “high” or “low”. The

MCTF figures are used to make comparative evaluations between relays with different styles

of design or construction, and as an indication of product reliability under specific conditions.

---------------------- Page: 8 ----------------------
IEC 61810-2:2017 © IEC 2017 – 7 –
ELECTROMECHANICAL ELEMENTARY RELAYS –
Part 2: Reliability
1 Scope

This part of IEC 61810 covers test conditions and provisions for the evaluation of endurance

tests using appropriate statistical methods to obtain reliability characteristics for relays.

This document applies to electromechanical elementary relays considered as non-repaired

items (i.e. items which are not repaired after failure).

The lifetime of a relay is usually expressed in number of cycles (CTF). Therefore, whenever

the terms “time” or “duration” are used in IEC 61649, they carry the meaning “cycles”.

However, with a given frequency of operation, the number of cycles can be transformed into

respective times (e.g. times to failure (TTF)).

The failure criteria and the resulting characteristics of elementary relays describing their

reliability in normal use are specified in this document. A relay failure occurs when the

specified failure criteria are met.

As the failure rate for elementary relays cannot be considered as constant, particularly due to

wear-out mechanisms, the cycles to failure of tested items typically show a Weibull

distribution. This document provides numerical and graphical methods to calculate

approximate values for the two-parameter Weibull distribution, as well as lower confidence

limits and a method for confirmation of reliability values with the WeiBayes method.

This document does not cover procedures for electromechanical elementary relays where

enhanced requirements for the verification of reliability apply.

NOTE 1 Such reliability test procedures are specified in IEC 61810-2-1. In particular, when electromechanical

elementary relays are intended to be incorporated in safety-related control systems of machinery in accordance

with IEC 62061 and ISO 13849-1, IEC 61810-2-1 defines procedures for the manufacturer to provide B values.

10D

NOTE 2 Electromechanical elementary relays with forcibly guided (mechanically linked) contacts according to

IEC 61810-3 offer the possibility of a high diagnostic coverage according to 4.5.3 of ISO 13849-1:2015.

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 61649:2008, Weibull analysis

IEC 61810-1:2015, Electromechanical elementary relays – Part 1: General and safety

requirements
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
---------------------- Page: 9 ----------------------
– 8 – IEC 61810-2:2017 © IEC 2017

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
item
any component that can be individually considered

Note 1 to entry: For the purpose of this document, items are electromechanical elementary relays.

3.2
non-repaired item
item which is not repaired after a failure
3.3
sample
one or more sampling items intended to provide information on the population

[SOURCE: IEC 60050-151:2001, 151-16-19, modified – The words "or on the material" have

been deleted from the definition.]
3.4
sample item

one of the individual items in a population of similar items and taken from one place and at

one time

[SOURCE: IEC 60050-151:2001, 151-16-18, modified – The words "or a portion of material

forming a cohesive entity" have been deleted from the definition.]
3.5
cycle
operation and subsequent release/reset
[SOURCE: IEC 60050-444:2002, 444-02-11]
3.6
frequency of operation
number of cycles per unit of time
[SOURCE: IEC 60050-444:2002, 444-02-12]
3.7
reliability

ability of an item to perform a required function under given conditions for a given number of

cycles or time interval

Note 1 to entry: It is generally assumed that the item is in a state to perform this required function at the

beginning of the time interval.

Note 2 to entry: The term “reliability” is also used as a measure of reliability performance (see

IEC 60050-312:2001, 312-07-06).

[SOURCE: IEC 60050-395:2014, 395-07-131, modified – The words "number of cycles or"

have been added to the definition, and the second note has been replaced by a new note.]

---------------------- Page: 10 ----------------------
IEC 61810-2:2017 © IEC 2017 – 9 –
3.8
reliability test

experiment carried out in order to measure, quantify or classify a reliability measure or

property of an item
[SOURCE: IEC 60300-3-5:2001, 3.1.27, modified – The notes have been deleted.]
3.9
life test

test with the purpose of estimating, verifying or comparing the lifetime of the class of items

being tested
[SOURCE: IEC 60300-3-5:2001, 3.1.17, modified – The note has been deleted.]
3.10
cycles to failure
CTF

total number of cycles of an item, from the instant it is first put in an operating state until

failure
3.11
mean cycles to failure
MCTF
expectation of the number of cycles to failure
3.12
time to failure
TTF

total time duration of operating time of an item, from the instant it is first put in an operating

state until failure
3.13
mean time to failure
MTTF
expectation of the time to failure
[SOURCE: IEC 60050-192:2015, 192-05-11, modified – The word "operating" has been
deleted from the term and the definition, and the notes have been deleted.]
3.14
useful life

number of cycles or time duration until a certain percentage of items have failed

Note 1 to entry: In this document, this percentage is defined as 10 %.
3.15
failure

termination of the ability of an item to perform a required function as defined in the failure

criteria

[SOURCE: IEC 60050-603:1986, 603-05-06, modified – The words "as defined in the failure

criteria" have been added to the definition.]
3.16
malfunction
event when an item does not perform an expected function
---------------------- Page: 11 ----------------------
– 10 – IEC 61810-2:2017 © IEC 2017
3.17
contact failure

occurrence of break and/or make malfunctions of a contact under test, exceeding a specified

number
3.18
failure criteria
specified conditions to judge if a fault or malfunction is a failure
3.19
contact load category
classification of relay contacts dependent on wear-out mechanisms
Note 1 to entry: Various contact load categories are defined in IEC 61810-1.
3.20
fault
deviation of the existing condition from the expected condition
3.21 Terms and definitions related to tests
3.21.1
type test

conformity test made on sample relays representative of the production to get basic

performance data or to verify that these relays comply with the specified requirements

3.21.2
routine test
conformity test made on sample without any modifications and specification ch
...

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