IEC 62058-11:2008

IEC 62058-11
Edition 1.0 2008-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electricity metering equipment (AC) – Acceptance inspection –
Part 11: General acceptance inspection methods

Equipement de comptage de l'électricite (c.a.) – Contrôle de réception –
Partie 11: Méthodes générales de contrôle de réception

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IEC 62058-11
Edition 1.0 2008-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electricity metering equipment (AC) – Acceptance inspection –
Part 11: General acceptance inspection methods

Equipement de comptage de l'électricite (c.a.) – Contrôle de réception –
Partie 11: Méthodes générales de contrôle de réception

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
XC
CODE PRIX
ICS 17.220; 91.140.50 ISBN 2-8318-9988-5
– 2 – 62058-11 © IEC:2008
CONTENTS
FOREWORD.6
INTRODUCTION.8
1 Scope.9
2 Normative references .9
3 Terms and definitions .9
3.1 Sources of data .10
3.2 Types of sampling .11
3.3 Specifications, values and test results.11
3.4 Types of inspection .12
3.5 Types of acceptance sampling inspection.14
3.6 Acceptance sampling inspection system aspects.15
3.7 Acceptance criteria.16
3.8 Types of operating characteristic curves.18
3.9 Terms relating to operating characteristics .18
3.10 Outgoing quality concepts .21
3.11 Other terms .21
4 Symbols and abbreviations.22
4.1 Symbols .22
4.2 Acronyms .23
5 General .23
5.1 The objectives of acceptance inspection .23
5.2 Acceptance sampling plans, schemes and systems .24
5.3 Practical and economic advantages of using standard sampling plans .24
5.4 Agreement between the parties .25
5.5 Selection of sampling schemes and sampling plans .26
5.6 Considerations influencing a selection.27
5.6.1 Long and short production runs .27
5.6.2 Lot-by-lot inspection .28
5.6.3 Isolated lot inspection.28
5.6.4 Attributes versus variables .28
5.6.5 Single and double sampling.29
5.6.6 “s” method and “σ” method.29
5.7 Nonconformity and nonconforming items .29
5.8 Classification of nonconformities .29
5.9 Operating characteristic (OC) curve .30
5.10 Producer’s risks (PR) and consumer’s risk (CR) .30
5.11 AQL, PRQ, LQ and CRQ .31
5.12 Switching rules for normal, tightened and reduced inspection.31
5.13 Inspection level .32
5.14 Sample size code letter .32
5.15 Place of inspection .33
5.16 Submission of product for acceptance inspection .33
5.17 Drawing of samples .33
5.18 Acceptability of lots .34
6 100 % inspection .34
6.1 Application of the method .34

62058-11 © IEC:2008 – 3 –
6.2 Lot sizes and acceptance numbers.34
6.3 Acceptance and non-acceptance .35
7 Lot-by-lot inspection by attributes .35
7.1 Application of the method .35
7.2 Drawing of samples .36
7.3 Inspection level .36
7.4 Sampling plans.36
7.4.1 Obtaining a sampling plan .36
7.4.2 Single sampling plans.36
7.4.3 Double sampling plans .39
7.4.4 Determination of acceptability.40
7.5 Normal, tightened and reduced inspection (see also 5.12).41
7.5.1 Start and continuation of inspection.41
7.5.2 Normal to tightened .41
7.5.3 Tightened to normal.42
7.5.4 Normal to reduced .42
7.5.5 Reduced to normal .43
7.5.6 Discontinuation and resumption of inspection .43
7.6 Operating characteristic (OC) curves.43
7.7 Process average .46
7.8 Average outgoing quality (AOQ) .46
7.9 Average outgoing quality limit (AOQL).46
7.10 Consumer’s risk (CR) .47
7.11 Producer’s risk (PR) .49
8 Isolated lot inspection.50
8.1 Application of the method .50
8.2 Procedures specified.50
8.2.1 Procedure A .50
8.2.2 Procedure B .50
8.3 Limiting quality .50
8.4 Procedure A .50
8.5 Procedure B .53
8.6 Rules for acceptance and non-acceptance .55
9 Skip-lot inspection .55
9.1 Application of the method .55
9.2 Manufacturer qualification .56
9.3 Product qualification.56
9.4 Detailed procedures .57
10 Lot-by-lot inspection by variables .57
10.1 Application of the method .57
10.2 Choice between the “s” and the “σ” methods.57
10.3 Standard plans .58
10.4 Preliminary operations.58
10.5 Standard multivariate “s” method procedures for independent quality
characteristics with combined control .
10.5.1 General methodology .58
10.5.2 Sampling plans.59
10.5.3 Description of the procedure.60
10.5.4 Simplified exact formula for the “s” method with sample size 4 .61

– 4 – 62058-11 © IEC:2008
10.5.5 Approximate procedure for the “s” method for n > 5 .61
10.6 Standard multivariate “σ” method procedures for independent quality
characteristics with combined control .64
10.6.1 General methodology .64
10.6.2 Sampling plans.65
10.6.3 Description of the procedure.65
10.7 Procedure during continuing inspection .66
10.8 Normality and outliers.66
10.8.1 Normality.66
10.8.2 Outliers .66
10.9 Records .66
10.9.1 Control charts.66
10.9.2 Lots that are not accepted .66
10.10 Normal, tightened and reduced inspection (see also 5.12) .66
10.11 Discontinuation and resumption of inspection .67
10.12 Switching between the “s” and “σ” methods .68
10.12.1 Estimating the process standard deviation .68
10.12.2 State of statistical control .68
10.12.3 Switching from the “s” method to the “σ” method .68
10.12.4 Switching from the “σ” method to the “s” method .69
10.13 Consumer protection .69
10.14 Operating characteristic curves .69
10.15 Consumer’s risk (CR) .72
10.16 Producer’ risk (PR) .74
Annex A (normative) Random numbers.76
Annex B (normative) Procedure for obtaining s or σ .79
Bibliography.80

Figure 1 – Selection procedure of sampling schemes and plans .
Figure 2 – Outline of switching rules .32
Figure 3 – OC curves for AQL = 1,0, single sampling plans, normal inspection .44
Figure 4 – OC curves for AQL = 1,0, single sampling plans, tightened inspection .44
Figure 5 – OC curves for single sampling plans, Ac=0 .45
Figure 6 – Operating characteristic curves for single sampling plans for non-critical
nonconformities, procedure B .54
Figure 7 – OC curves for normal inspection, AQL = 1,0.69
Figure 8 – OC curves for tightened inspection, AQL = 1,0.70
Figure 9 – OC curves for reduced inspection, AQL = 1,0.71

Table 1 – Acceptance number Ac for 100 % inspection .34
Table 2 – Single sampling plans for normal, tightened and reduced inspection, AQL = 1,0.37
Table 3 – Example with lot size = 80, inspection level II.37
Table 4 – Example with lot size = 400, inspection level II.38
Table 5 – Example with lot size = 800, inspection level III.38
Table 6 – Single sampling plans for critical nonconformities Ac = 0.39
Table 7 – Double sampling plans for normal, tightened and reduced inspection, AQL = 1,0 .40

62058-11 © IEC:2008 – 5 –
Table 8 – Calculation of switching scores .43
Table 9 – Tabulated values of OC curves for single sampling, AQL = 1,0 plans .45
Table 10 – Tabulated values of OC curves for single sampling, normal inspection,
accept zero sampling plans.46
Table 11 – Average Outgoing Quality Limit (AOQL) at AQL = 1,0.47
Table 12 – Average Outgoing Quality Limit (AOQL) for Ac = 0 sampling plans, normal
inspection .47
Table 13 – Consumer’s risk quality (CRQ): AQL = 1,0 plans .48
Table 14 – Consumer’s risk quality (CRQ): Accept zero plans.48
Table 15 – Producer’s risk (PR): AQL = 1,0 .49
Table 16 – Producer’s risk (PR): Accept zero plans .49
Table 17 – Sampling plans for non-critical nonconformities, procedure A, LQ = 5,0 .51
Table 18 – Sampling plans for critical nonconformities, procedure A.52
Table 19 – Probability of acceptance for accept zero plans.52
Table 20 – Single sampling plans for non-critical nonconformities, procedure B, LQ = 5,0 .54
Table 21 – Equivalent sample sizes for single and double sampling.55
Table 22 – Equivalent acceptance numbers for single and double sampling.55
Table 23 – Sample sizes for the “s” method and the “σ” method with AQL = 1,0 .58
Table 24 – Sampling plans for the “s” method .60
Table 25 – Values of a .62
n
Table 26 – Sampling plans for the “σ” method.65
Table 27 – Supplementary acceptability constants for qualifying towards reduced
inspection .67
Table 28 – Values of c for upper control limit on the sample standard deviation .68
U
Table 29 – Tabulated values of OC curves for normal inspection, AQL = 1,0 .70
Table 30 – Tabulated values of OC curves for tightened inspection, AQL = 1,0.71
Table 31 – Tabulated values of OC curves for reduced inspection, AQL = 1,0.72
Table 32 – Consumer’s risk quality (CRQ): “s” method .73
Table 33 – Consumer’s risk quality (CRQ): “σ” method .73
Table 34 – Producer’s risk (PR): “s” method.74
Table 35 – Producer’s risk (PR): “σ” method .74
Table A.1 – Random numbers.76

– 6 – 62058-11 © IEC:2008
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICITY METERING EQUIPMENT (AC) –
ACCEPTANCE INSPECTION –
Part 11: General acceptance inspection methods

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
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6) All users should ensure that they have the latest edition of this publication.
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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 62058-11 has been prepared by IEC technical committee 13:
Electrical energy measurement, tariff- and load control.
The text of this standard is based on the following documents:
FDIS Report on voting
13/1430/FDIS 13/1438/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.
A list of all parts of IEC 62058 series, published under the general title Electricity metering
equipment (AC) – Acceptance inspection, can be found on the IEC website.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

62058-11 © IEC:2008 – 7 –
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.
– 8 – 62058-11 © IEC:2008
INTRODUCTION
This part of IEC 62058 describes – based on relevant standards established by ISO TC 69
SC 5 – general acceptance inspection methods of newly manufactured electricity meters,
supplied in lots of 50 and above. The method of acceptance of smaller lots should be agreed
upon by the manufacturer and the customer.
In this standard, it has been taken into account that modern, automated manufacturing
processes operated under quality management systems allow to keep the quality level under
tight control.
This standard, together with IEC 62058-21, containing particular requirements for acceptance
inspection of electromechanical meters for active energy, and IEC 62058-31, containing
particular requirements for acceptance inspection of static meters for active energy, cancels
and replaces the following standards:
• IEC 60514: Acceptance inspection of class 2 alternating-current watt-hour meters and
• IEC 61358: Acceptance inspection for direct connected alternating current static watt-hour
meters for active energy (classes 1 and 2).
Main changes in this standard compared to those earlier standards:
• it is based on the latest standards established by ISO TC 69 SC 5;
• the rules for switching between normal, tightened and reduced inspection have been
adopted;
• the procedures for inspection of isolated lots have been adopted;
• the procedures for skip-lot sampling have been adopted;
• for inspection by variables, the “R” method has been eliminated and the “σ” method has
been adopted.
62058-11 © IEC:2008 – 9 –
ELECTRICITY METERING EQUIPMENT (AC) –
ACCEPTANCE INSPECTION –
Part 11: General acceptance inspection methods

1 Scope
The general acceptance inspection methods specified in this part of IEC 62058 apply to newly
manufactured electricity meters produced and supplied in lots of 50 and above.
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.
ISO 2859-1:1999, Sampling procedures for inspection by attributes – Part 1: Sampling
schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection
ISO 2859-1:1999/Cor 1:2001
ISO 2859-2:1985, Sampling procedures for inspection by attributes – Part 2: Sampling plans
indexed by limiting quality (LQ) for isolated lot inspection
ISO 2859-3:2005, Sampling procedures for inspection by attributes – Part 3: Skip-lot sampling
procedures
ISO 3534-2:2006 Ed. 2 Statistics – Vocabulary and symbols – Part 2: Applied statistics
ISO 3951-1:2005 Ed. 1, Sampling procedures for inspection by variables – Part 1:
Specification for single sampling plans indexed by acceptance quality limit (AQL) for lot-by-lot
inspection for a single quality characteristic and a single AQL
ISO 3951-2:2006 Ed. 1, Sampling procedures for inspection by variables – Part 2: General
specification for single sampling plans indexed by acceptance quality limit (AQL) for lot-by-lot
inspection of independent quality characteristics
ISO 5479:1997, Statistical interpretation of data – Tests for departure from the normal
distribution
3 Terms and definitions
For the purposes of this document, the terms and definitions of ISO 3534-2 and the following
apply.
NOTE In this standard, the term “meter” means any kind of metering equipment in the Scope of TC 13, i.e. meters
for active or reactive energy, time switches, ripple control receivers, etc. The term “customer” is used with the
same meaning as “consumer” and the term “manufacturer” is used with the same meaning as the term “supplier”.

– 10 – 62058-11 © IEC:2008
3.1 Sources of data
3.1.1
characteristic
distinguishing feature
NOTE 1 A characteristic can be inherent or assigned.
NOTE 2 A characteristic can be qualitative or quantitative.
[ISO 3534-2, 1.1.1 modified]
3.1.2
population
(reference) totality of items under consideration
[ISO 3534-2, 1.2.1. modified]
3.1.3
lot
definite part of a population constituted under essentially the same conditions as the
population with respect to the sampling purpose
NOTE The sampling purpose can, for example, be to determine lot acceptability, or to estimate the mean value of
a particular characteristic.
[ISO 3534-2, 1.2.4]
3.1.4
isolated lot
lot separated from the sequence of lots in which it was formed and not forming part of a
current sequence
[ISO 3534-2, 1.2.5]
3.1.5
re-submitted lot
lot which previously has been designated as not acceptable and which is submitted again for
inspection after having been further treated, tested, sorted, reprocessed, etc.
[ISO 3534-2, 1.2.9]
3.1.6
item
entity
anything that can be described and considered separately; for the purposes of this standard,
an electricity meter
[ISO 3534-2, 1.2.11 modified]
3.1.7
nonconforming item
item with one or more nonconformities
[ISO 3534-2, 1.2.12]
3.1.8
defective item
item with one or more defects
[ISO 3534-2, 1.2.13]
62058-11 © IEC:2008 – 11 –
3.1.9
sampling unit
unit
one of the individual parts into which a population is divided
[ISO 3534-2, 1.2.14 modified]
3.1.10
nonconforming unit
unit with one or more nonconformities
[ISO 3534-2, 1.2.15]
3.1.11
sample
subset of a population made up of one or more sampling units
[ISO 3534-2, 1.2.17 modified]
3.1.12
sample size
number of sampling units in a sample
NOTE In a multistage sample, the sample size is the total number of sampling units at the conclusion of the final
stage of sampling.
[ISO 3534-2, 1.2.26]
3.2 Types of sampling
3.2.1
sampling
act of drawing or constituting a sample
[ISO 3534-2, 1.3.1]
3.2.2
simple random sampling
sampling where a sample of n sampling units is taken from a population in such a way that all
the possible combinations of n sampling units have the same probability of being taken
[ISO 3534-2, 1.3.4 modified]
3.2.3
acceptance sampling
sampling after which decisions are made to accept or not to accept a lot based on sample
results
[ISO 3534-2, 1.3.17 modified]
3.3 Specifications, values and test results
3.3.1
specification limit
limiting value stated for a characteristic
[ISO 3534-2, 3.1.3]
– 12 – 62058-11 © IEC:2008
3.3.2
upper specification limit
U
specification limit that defines the upper limiting value
[ISO 3534-2, 3.1.4]
3.3.3
lower specification limit
L
specification limit that defines the lower limiting value
[ISO 3534-2, 3.1.5]
3.3.4
single specification limit
specification limit where the decision criteria is applied only to one limit
[ISO 3534-2, 3.1.7]
3.3.5
combined double specification limit
specification limit where the decision criteria is applied collectively to the upper and lower
limits
[ISO 3534-2, 3.1.8]
3.3.6
combined control
requirement when nonconformity beyond both the upper and the lower specification of a
quality characteristic belongs to the same class, to which a single AQL is applied
[ISO 3951-2, 3.17, modified]
3.3.7
nonconformity
non-fulfilment of a requirement
NOTE See notes to “defect”.
[ISO 3534-2, 3.1.11]
3.3.8
defect
non-fulfilment of a requirement related to an intended or specified use
NOTE 1 The distinction between the concepts defect and nonconformity is important as it has legal connotations,
particularly those associated with product liability issues. Consequently, the term “defect” should be used with
extreme caution.
NOTE 2 The intended use by the customer can be affected by the nature of the information, such as operating or
maintenance instructions, provided by the customer.
[ISO 3534-2, 3.1.12]
3.4 Types of inspection
3.4.1
conformity evaluation
systematic examination of the extent to which an item/entity fulfils specified requirements
[ISO 3534-2, 4.1.1]
62058-11 © IEC:2008 – 13 –
3.4.2
inspection
conformity evaluation by observation and judgement accompanied as appropriate by
measurement, testing or gauging
[ISO 3534-2, 4.1.2]
3.4.3
inspection by attributes
inspection by noting the presence, or absence, of one or more particular characteristic(s) in
each of the items in the group under consideration, and counting how many items do, or do
not, possess the characteristic(s), or how many such events occur in the item
NOTE When inspection is performed by simply noting whether the item is nonconforming or not, the inspection is
termed inspection for nonconforming items. When inspection is performed by noting the number of nonconformities
on each unit, the inspection is termed inspection for number of nonconformities.
[ISO 3534-2, 4.1.3 modified]
3.4.4
inspection by variables
inspection by measuring the magnitude(s) of the characteristic(s) of an item
[ISO 3534-2, 4.1.4]
3.4.5
100 % inspection
inspection of selected characteristic(s) of every item in the group under consideration
[ISO 3534-2, 4.1.5]
3.4.6
sampling inspection
inspection of selected items in the group under consideration
[ISO 3534-2, 4.1.6]
3.4.7
acceptance sampling inspection
acceptance inspection where the acceptability is determined by means of sampling inspection
[ISO 3534-2, 4.1.8]
3.4.8
normal inspection
inspection which is used when there is no reason to think that the quality level achieved by
the process differs from a specified level
[ISO 3534-2, 4.1.10]
3.4.9
reduced inspection
inspection less severe than normal inspection, to which the latter is switched when inspection
results of a predetermined number of lots indicate that the quality level achieved by the
process is better than that specified
[ISO 3534-2, 4.1.11]
– 14 – 62058-11 © IEC:2008
3.4.10
switching score
indicator that is used under normal inspection to determine whether the current inspection
results are sufficient to allow for a switch to reduced inspection
[ISO 2859-1, 3.1.23]
3.4.11
tightened inspection
inspection more severe than normal inspection, to which the latter is switched when
inspection results of a predetermined number of lots indicate that the quality level achieved by
the process is poorer than that specified
[ISO 3534-2, 4.1.12]
3.4.12
isolated lot inspection
inspection of a unique lot or one separated from the sequence of lots in which it was produced
or collected
[ISO 3534-2, 4.1.14]
3.4.13
lot-by-lot inspection
inspection of a product submitted in a series of lots
[ISO 3534-2, 4.1.15]
3.4.14
original inspection
inspection of a lot, or other amount, not previously inspected
NOTE This is in contrast, for example, to inspection of a lot which has previously been designated as not
acceptable and which is submitted again for inspection after having been further sorted, reprocessed, etc.
[ISO 3534-2, 4.1.16]
3.4.15
acceptance inspection
inspection to determine whether a lot or other amount is acceptable
[ISO 3534-2, 4.1.17]
3.5 Types of acceptance sampling inspection
3.5.1
single acceptance sampling inspection
acceptance sampling inspection in which the decision, according to a defined rule, is based
on the inspection results obtained from a single sample of predetermined size, n
[ISO 3534-2, 4.2.2]
3.5.2
double acceptance sampling inspection
multiple acceptance sampling inspection in which at most two samples are taken
NOTE The decisions are made according to defined rules.
[ISO 3534-2, 4.2.3]
62058-11 © IEC:2008 – 15 –
3.5.3
skip-lot acceptance sampling inspection
acceptance sampling inspection in which some lots in a series are accepted without
inspection, when the sampling results for a stated number of immediately preceding lots meet
stated criteria
[ISO 3534-2, 4.2.5]
3.5.4
acceptance sampling inspection by variables
acceptance sampling inspection in which the acceptability of a process is determined
statistically from measurements on specified quality characteristics of each item in a sample
from a lot
NOTE Lots taken from an acceptable process are assumed to be acceptable.
[ISO 3534-2, 4.2.11]
3.5.5
acceptance sampling inspection by attributes
acceptance sampling inspection whereby the presence or absence of one or more specified
characteristics of each item in a sample is observed to establish statistically the acceptability
of a lot or process
[ISO 3534-2, 4.2.12]
3.6 Acceptance sampling inspection system aspects
3.6.1
acceptance sampling inspection system
collection of acceptance sampling plans or acceptance sampling schemes together with
criteria by which appropriate plans or schemes may be chosen
[ISO 3534-2, 4.3.1]
3.6.2
acceptance sampling scheme
combination of acceptance sampling plans with switching rules for changing from one plan to
another
[ISO 3534-2, 4.3.2]
3.6.3
acceptance sampling plan
plan which states the sample size(s) to be used and the associated criteria for lot acceptance
[ISO 3534-2, 4.3.3]
3.6.4
switching rule
instruction within an acceptance sampling scheme for changing from one acceptance
sampling plan to another of greater or lesser severity of sampling based on demonstrated
quality history
NOTE Normal, tightened, reduced inspection or discontinuation of inspection are examples of severity of
sampling.
[ISO 3534-2, 4.3.4]
– 16 – 62058-11 © IEC:2008
3.6.5
inspection level
index of the relative amount of inspection of an acceptance sampling scheme, chosen in
advance, and relating the sample size to the lot size
NOTE 1 A lower/higher inspection level can be selected if experience shows that a less/more discriminating
operating characteristic curve will be appropriate.
NOTE 2 The term should not be confused with severity of sampling which concerns switching rules, which operate
automatically.
[ISO 3534-2, 4.3.5]
3.6.6
severity of sampling
degree of discrimination within an acceptance sampling scheme for changing from a normal to
a reduced/tightened acceptance sampling plan if the quality of the submitted product or
service improves/deteriorates
NOTE The term should not be confused with inspection level (4.3.5) which is independent of switching rules
(4.3.4).
[ISO 3534-2, 4.3.6]
3.6.7
acceptance sampling procedure
operational requirements and/or instructions related to the use of a particular acceptance
sampling plan
NOTE This covers the planned method of selection, withdrawal and preparation of sample(s) from a lot to yield
knowledge of the characteristic(s) of the lot.
[ISO 3534-2, 4.3.7]
3.6.8
curtailed inspection
acceptance sampli
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