SIST EN 62059-41:2006

Electricity metering equipment - Dependability -- Part 41: Reliability prediction

This part of IEC 62059-41 is applicable to all types of stratic  metering equipment for energy measurement and load  control.The main objective is to provide a tool for predicting the  failure rate of electricity metering equipment using the parts  stress method. It also provides an overview of reliability  analysis and prediction methods.

Wechselstrom-Elektrizitätszähler - Zuverlässigkeit -- Teil 41: Zuverlässigkeitsvorhersage

Equipements de comptage de l'électricité - Surêté de fonctionnement -- Partie 41: Prévision de fiabilité

563485

Oprema za merjenje električne energije – Zagotovljivost – 41. del: Napovedovanje zanesljivosti (IEC 62059-41:2006)

General Information

• Status: Published
• Publication Date: 30-Sep-2006
• ICS: 17.220.20 - Measurement of electrical and magnetic quantities
• ICS: 91.140.50 - Electricity supply systems
• Technical Committee: MEE - Equipment for electrical energy measurement and load control
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Oct-2006
• Due Date: 01-Oct-2006
• Completion Date: 01-Oct-2006
• Ref Project: EN 62059-41:2006 - Electricity metering equipment - Dependability - Part 41: Reliability prediction

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 62059-41:2006
01-oktober-2006
2SUHPD]DPHUMHQMHHOHNWULþQHHQHUJLMH±=DJRWRYOMLYRVW±GHO1DSRYHGRYDQMH
]DQHVOMLYRVWL,(&
Electricity metering equipment - Dependability -- Part 41: Reliability prediction
Wechselstrom-Elektrizitätszähler - Zuverlässigkeit -- Teil 41: Zuverlässigkeitsvorhersage
Equipements de comptage de l'électricité - Surêté de fonctionnement -- Partie 41:
Prévision de fiabilité
Ta slovenski standard je istoveten z: EN 62059-41:2006
ICS:
17.220.20 0HUMHQMHHOHNWULþQLKLQ Measurement of electrical
PDJQHWQLKYHOLþLQ and magnetic quantities
91.140.50 Sistemi za oskrbo z elektriko Electricity supply systems
SIST EN 62059-41:2006 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 62059-41:2006

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SIST EN 62059-41:2006


EUROPEAN STANDARD
EN 62059-41

NORME EUROPÉENNE
May 2006
EUROPÄISCHE NORM

ICS 91.140.50


English version


Electricity metering equipment -
Dependability
Part 41: Reliability prediction
(IEC 62059-41:2006)


Equipements de comptage de l'électricité - Wechselstrom-Elektrizitätszähler -
Surêté de fonctionnement Zuverlässigkeit
Partie 41: Prévision de fiabilité Teil 41: Zuverlässigkeitsvorhersage
(CEI 62059-41:2006) (IEC 62059-41:2006)




This European Standard was approved by CENELEC on 2006-02-01. CENELEC members are bound to comply
with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard
the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and notified
to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, the Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels


© 2006 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 62059-41:2006 E

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SIST EN 62059-41:2006
EN 62059-41:2006 - 2 -

Foreword
The text of document 13/1348/FDIS, future edition 1 of IEC 62059-41, prepared by IEC TC 13, Equipment
for electrical energy measurement and load control, was submitted to the IEC-CENELEC parallel vote
and was approved by CENELEC as EN 62059-41 on 2006-02-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
(dop) 2007-01-01
national standard or by endorsement
– latest date by which the national standards conflicting
(dow) 2009-02-01
with the EN have to be withdrawn
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 62059-41:2006 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:
IEC 60300-3-1 NOTE  Harmonized as EN 60300-3-1:2004 (not modified).
IEC 61078 NOTE  Harmonized as EN 61078:1993 (not modified).

__________

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SIST EN 62059-41:2006
- 3 - EN 62059-41:2006

Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications

The following referenced documents are indispensable for the application 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.

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.

Publication Year Title EN/HD Year
IEC 60050-191 1990 International Electrotechnical Vocabulary - -
+ A1 1999 (IEV) - -
+ A2 2002 Chapter 191: Dependability and quality of - -
service


IEC 61709 1996 Electronic components - Reliability - EN 61709 1998
Reference conditions for failure rates and
stress models for conversion


IEC/TR 62059-11 2002 Electricity metering equipment - Dependability- -
Part 11: General concepts


IEC/TR 62059-21 2002 Electricity metering equipment - Dependability- -
Part 21: Collection of meter dependability
data from the field

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SIST EN 62059-41:2006

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SIST EN 62059-41:2006
NORME CEI
INTERNATIONALE
IEC



62059-41
INTERNATIONAL


Première édition
STANDARD

First edition

2006-03


Equipements de comptage de l'électricité –
Sûreté de fonctionnement –
Partie 41:
Prévision de fiabilité

Electricity metering equipment –
Dependability –
Part 41:
Reliability prediction

 IEC 2006 Droits de reproduction réservés  Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any
utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including
électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
microfilms, sans l'accord écrit de l'éditeur. the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: [phone] Telefax: [phone] E-mail: [e-mail] Web: www.iec.ch
CODE PRIX
S
PRICE CODE
Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
Pour prix, voir catalogue en vigueur
For price, see current catalogue

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SIST EN 62059-41:2006
62059-41  IEC:2006 – 3 –
CONTENTS
FOREWORD.5
INTRODUCTION.9

1 Scope.11
2 Normative references .11
3 Terms, definitions and abbreviations .11
4 General information.19
5 Reliability analysis methods .21
6 Reliability prediction using the parts stress method .23
6.1 Overview .23
6.2 Component failure rate data .25
6.3 Stress models .25
6.4 Failure rate prediction using the parts stress method.27
6.5 Phases of the failure rate prediction process .27
6.6 Presentation of results .29
7 Other dependability considerations.29
8 Life time of life limited components.31

Annex A (normative) Reliability prediction – Procedural flow.33
Annex B (informative) Overview of other reliability analysis and prediction methods .35

Bibliography.43

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SIST EN 62059-41:2006
62059-41  IEC:2006 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

ELECTRICITY METERING EQUIPMENT –
DEPENDABILITY –

Part 41: Reliability prediction


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,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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 62059-41 has been prepared by Technical Committee 13:
Equipment for electrical energy measurement and load control.
The text of this standard is based on the following documents:
FDIS Report on voting
13/1348/FDIS 13/1359/RVD

Full information on the voting for the approval of this standard 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.

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SIST EN 62059-41:2006
62059-41  IEC:2006 – 7 –
IEC 62059 consists of the following parts, under the general title Electricity metering
equipment – Dependability:
Part 11: General concepts
Part 21: Collection of meter dependability data from the field
Part 41: Reliability prediction
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result 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.

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SIST EN 62059-41:2006
62059-41  IEC:2006 – 9 –
INTRODUCTION
The main objective is to provide a tool for predicting the failure rate of electricity metering
equipment using the parts stress method. It also provides an overview of reliability analysis
and prediction methods.
The result of the prediction can be used in the design phase to support design decisions, in
relation with type approval to support decisions concerning the certification period and in the
operation phase to determine the necessary maintenance performance to obtain the required
availability.

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SIST EN 62059-41:2006
62059-41  IEC:2006 – 11 –
ELECTRICITY METERING EQUIPMENT –
DEPENDABILITY –

Part 41: Reliability prediction



1 Scope
This part of IEC 62059-41 is applicable to all types of static metering equipment for energy
measurement and load control.
2 Normative references
The following referenced documents are indispensable for the application 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 60050-191:1990, International Electrotechnical Vocabulary (IEV) – Chapter 191: Depend-
ability and quality of service
Amendment 1(1999)
Amendment 2 (2002)
IEC 61709:1996, Electronic components – Reliability – Reference conditions for failure rates
and stress models for conversion
IEC 62059-11:2002, Electricity metering equipment – Dependability – Part 11: General
concepts
IEC 62059-21:2002, Electricity metering equipment – Dependability – Part 21: Collection of
meter dependability data from the field
3 Terms, definitions and abbreviations
For the purposes of this document, the following terms and definitions apply.
NOTE Only those terms relevant to the subject, which have not already been included in IEC 62059-11, are given
here.
3.1
accelerated test
test in which the applied stress level is chosen to exceed that stated in the reference
conditions in order to shorten the time duration required to observe the stress response of the
item, or to magnify the response in a given time duration
NOTE To be valid, an accelerated test shall not alter the basic fault modes and failure mechanisms, or their
relative prevalence.
[IEV 191-14-07]

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SIST EN 62059-41:2006
62059-41  IEC:2006 – 13 –
3.2
administrative delay (for corrective maintenance)
accumulated time during which an action of corrective maintenance on a faulty item is not
performed due to administrative reasons
[IEV 191-08-09]
3.3
ageing failure, wearout failure
failure whose probability of occurrence increases with the passage of time, as a result of
processes inherent in the item
[IEV 191-04-09]
3.4
constant failure intensity period
that period, if any, in the life of a repaired item during which the failure intensity is
approximately constant
[IEV 191-10-08]
3.5
constant failure rate period
that period, if any, in the life of a non-repaired item during which the failure rate is
approximately constant
[IEV 191-01-09]
3.6
equipment under prediction
EUP
static electricity metering equipment for which a reliability prediction is being made
3.7
failure cause
circumstances during design, manufacture or use which have led to a failure
[IEV 191-04-17]
3.8
failure intensity acceleration factor
in a time interval of given duration, whose beginning is specified by a fixed age of a repaired
item, ratio of the number of failures obtained under two different sets of stress conditions
[IEV 191-14-12]
3.9
(instantaneous) failure rate
λ(t)
limit, if it exists, of the quotient of the conditional probability that the instant of a failure of a
non-repaired item falls within a given time interval (t, t + Δt) and the duration of this time
interval, Δt, when Δt tends to zero, given that the item has not failed up to the beginning of the
time interval

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SIST EN 62059-41:2006
62059-41  IEC:2006 – 15 –
NOTE 1 The instantaneous failure rate is expressed by the formula:
1 F(t + Δt) − F(t) f (t)
λ(t) = lim =
Δt→0 Δt R(t) R(t)
where F(t) and f(t) are respectively the distribution function and the probability density of the failure instant, and
where R(t) is the reliability function, related to the reliability R(t ,t ) by R(t) =R(0,t).
1 2
NOTE 2 An estimated value of the instantaneous failure rate can be obtained by dividing the ratio of the number
of items which have failed during a given time interval to the number of non-failed items at the beginning of the
time interval, by the duration of the time interval.
NOTE 3 In English, the instantaneous failure rate is sometimes called "hazard function".
[IEV 191-12-02]
3.10
failure rate acceleration factor
ratio of the failure rate under accelerated testing conditions to the failure rate under stated
reference test conditions
NOTE Both failure rates refer to the same time period in the life of the tested items.
[IEV 191-14-11]
3.11
fault
state of an item characterized by inability to perform a required function, excluding the
inability during preventive maintenance or other planned actions, or due to lack of external
resources
NOTE 1 A fault is often the result of a failure of the item itself, but may exist without prior failure.
NOTE 2 In English, the term “fault” is also used in the field of electric power systems with the meaning as given in
604-02-01: then the corresponding term in French is “défaut”.
[IEV 191-05-01]
3.12
maintenance
combination of all technical and administrative actions, including supervision actions,
intended to retain an item in, or restore it to, a state in which it can perform a required
function
[IEV 191-07-01]
3.13
maintenance policy
description of the interrelationship between the maintenance echelons, the indenture levels
and the levels of maintenance to be applied for the maintenance of an item
[IEV 191-07-03]
3.14
maintenance time
time interval during which a maintenance action is performed on an item either manually or
automatically, including technical delays and logistic delays
NOTE Maintenance may be carried out while the item is performing a required function.
[IEV 191-08-01]

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SIST EN 62059-41:2006
62059-41  IEC:2006 – 17 –
3.15
mean repair time
MRT
expectation of the repair time
[IEV 191-13-05]
3.16
mean operating time between failures
MTBF
expectation of the operating time between failures
[IEV 191-12-09]
3.17
mean time to failure
MTTF
expectation of the time to failure
[IEV 191-12-07]
3.18
operating time
time interval during which an item is in an operating state
[IEV 191-09-01]
3.19
prediction
process of computation used to obtain the predicted value(s) of a quantity
NOTE The term “prediction” may also be used to denote the predicted value(s) of a quantity.
[IEV 191-16-01]
3.20
redundancy
in an item, existence of more than one means for performing a required function
[IEV 191-15-01]
3.21
reference data
data which, by general agreement, may be used as a standard or as a basis for prediction
and/or comparison with observed data
[IEV 191-14-18]
3.22
reliability model
mathematical model used for prediction or estimation of reliability performance measures of
an item
[IEV 191-16-02]

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SIST EN 62059-41:2006
62059-41  IEC:2006 – 19 –
3.23
(instantaneous) repair rate
µ(t)
limit, if this exists, of the ratio, of the conditional probability that the corrective maintenance
action terminates in a time interval, (t, t +Δt) and the duration of this time interval, Δt, when Δt
tends to zero, given that the action had not terminated at the beginning of the time interval
[IEV 191-13-02]
3.24
repair time
that part of active corrective maintenance time during which repair actions are performed on
an item
[IEV 191-08-16]
3.25
required function
function or a combination of functions of an item, which is considered necessary to provide a
given service
[IEV 191-01-05]
3.26
(steady-state) availability
the mean of the instantaneous availability under steady-state conditions over a given time
interval
NOTE Under certain conditions, for instance constant failure rate and constant repair rate, the steady-state
availability may be expressed by the ratio of the mean up time to the sum of the mean up time and mean down
time. Under these conditions, asymptotic and steady state availability are identical and are often referred to as
“availability”.
[IEV 191-11-06]
3.27
stress model
mathematical model used to describe the influence of relevant applied stresses on a reliability
performance measure or any other property of an item
[IEV 191-16-10]
4 General information
Reliability prediction methods are used to determine the probability that in a certain time
interval, an EUP will be in the operating state, will be out of service or will be in the
maintenance process. Results of such prediction methods can also indicate the percentage of
equipment in a given population operating correctly, failed or being repaired, and the mean
length of these intervals.
Reliability prediction is a statistical process reaching into the future, and it is based on
information known from the past. The result therefore is always a probability of certain
variables. To perform reliability predictions, detailed system knowledge and component
reliability data are necessary.
It is important to distinguish between repairable and non-repairable items because the
variables characterizing them are quite different, although there is a relationship between
these variables.

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SIST EN 62059-41:2006
62059-41  IEC:2006 – 21 –
In a non-repairable system, the Time To Failure (TTF) of the system components determines
the useful life, during which the equipment performs its required functions with an estimated
probability.
For a repairable system, its steady-state availability is the most important, and the mean
repair-time or maintainability also become important variables since the cost of maintenance
and the frequency of functional interruptions depend on each other.
This distinction shall also be made because requirements must be set for the correct set of
variables. For example, it is not possible to set or meet requirements for availability by
observing or predicting only the reliability function, without considering maintainability,
including the maintenance policy of the utility.
Before any prediction can be made, the EUP shall be modelled. An EUP usually consists of
several subsystems or components. Components are the smallest units, which form the
system. Components are defined to be non-repairable otherwise they are regarded as sub-
systems. Prediction methods for non-repairable systems are therefore also applicable to
components. System reliability prediction depends on the reliability of the components, and
system reliability calculations use component reliability data. To obtain good prediction
results, the reliability of components must be known as exactly as possible.
It is also important to know the operating conditions of the components, as these have
influence on the reliability of the components. Some prediction methods also require the
structural knowledge of the system.
Predictions are only valid if:
– no unforeseen events in or outside the EUP occur (for example the EUP is damaged);
– the EUP does not change its characteristics except from ageing;
– environmental conditions are constant or predictable;
– functional conditions (e.g. mains voltage) are constant or predictable;
– detailed performance requirements or failure criteria of the EUP exist;
– no design failures are present.
The above criteria are the only scale by which the correct functioning of the EUP can be
judged.
Therefore, reliability prediction results shall always be presented together with the assump-
tions and conditions for which the prediction was made. See also 6.6.
5 Reliability analysis methods
For any reliability model, it is essential to perform an analysis of the EUP to confirm that the
model chosen is suitable to achieve the desired result. Techniques to make this analysis are
outlined in Annex B.

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SIST EN 62059-41:2006
62059-41  IEC:2006 – 23 –
Reliability analysis methods usually provide information on system reliability at a particular
instant of time at present or for a time interval in the past. For reliability analysis and
prediction the relevant variables, characteristics, and parameters are mostly the same.
Additionally, reliability analysis can and should provide information on the failure causes.
If the EUP is considered repairable, then information on the reintroduction into the field after
repair (end of down time interval) will also be known precisely.
6 Reliability prediction using the parts stress method
6.1 Overview
The parts stress method is used for predicting the failure rate of a system based on the failure
rate of its components under the operating conditions experienced during the use of the
system.
The basic assumption is that equal importance is placed on all components concerning
system reliability, i.e. failure of any component is assumed to lead to a system failure (simple
series model). In many practical cases, this assumption is of course not true. In such cases,
this method may lead to pessimistic results.
Additionally, all failure rates are assumed to be constant for the time period considered, i.e.
an exponential failure distribution is assumed. During the operating life of an EUP this is an
acceptable approximation.
The following data are needed:
– the number of components in each component category;
– failure rate of each component under reference conditions;
– stress factors and conversion models for each component;
– structural information for the circuits, which are not intrinsically series connected.
The failure rate of the system is calculated by totalling the failure rate of each component in
each category under their respective operating conditions.
The inverse function of this failure rate is the MTBF, which is the average time between two
failures. The end of the useful life on the other hand is determined by the wear out of the
components and cannot be estimated based on the exponential model.
If redundancy were built in, then due to the higher number of components, the parts stress
method would indicate lower reliability for better systems. In such cases, it is necessary to
combine the parts stress method with other reliability prediction and analysis methods.
Redundant subsystems shall be treated as single elements in order that the resulting failure
rate can be included in the series connected parts model. This failure rate can be calculated
by other methods, for example combinatorial probability computation (multi-level approach).

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SIST EN 62059-41:2006
62059-41  IEC:2006 – 25 –
6.2 Component failure rate data
Component failure rate data may be obtained from appropriate handbooks (see Bibliography).
The advantage of using handbook data is that system designs from different manufacturers
can be readily compared. However, data provided by component suppliers and data on items
and components obtained from field feedback may provide results that are more accurate
hence use of such data is preferred. For components not included in the database chosen,
data may only be obtained from the item supplier or field feedback from previous designs.
IEC 61709 provides guidance on the use of failure rate data for predicting the reliability of
components in electronic equipment. It presents reference conditions and generic and
component category specific stress
...