SIST EN 61358:1997
(Main)Acceptance inspection for direct connected alternating current static watt-hour meters for active energy (classes 1 and 2)
Acceptance inspection for direct connected alternating current static watt-hour meters for active energy (classes 1 and 2)
Applies to newly manufactured direct connected alternating current static watt-hour meters of classes 1 and 2, covered by EN 61036, which are produced and delivered in quantities of 50 and above. They provide for 100 % inspection or sampling inspection for acceptance by the purchaser.
Annahmeprüfung von elektronischen Wechselstrom-Wirkverbrauchzählern für direkten Anschluß (Klassen 1 und 2)
Contrôle de réception des compteurs statiques d'énergie active pour courant alternatif et à branchement direct (classes 1 et 2)
S'applique aux compteurs statiques d'énergie active pour courant alternatif, neufs, des classes 1 et 2, à branchement direct spécifiés dans la EN 61036, fabriqués et livrés par lots de 50 unités et plus. Elles définissent des règles d'acceptation par l'acheteur, soit par un contrôle à 100 %, soit par un contrôle par échantillonnage.
Prevzemna kontrola za statične števce električne delovne energije izmeničnega toka za direktno priključitev (razreda 1 in 2) (IEC 1358:1996)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 61358:1997
01-april-1997
3UHY]HPQDNRQWUROD]DVWDWLþQHãWHYFHHOHNWULþQHGHORYQHHQHUJLMHL]PHQLþQHJD
WRND]DGLUHNWQRSULNOMXþLWHY UD]UHGDLQ ,(&
Acceptance inspection for direct connected alternating current static watt-hour meters for
active energy (classes 1 and 2)
Annahmeprüfung von elektronischen Wechselstrom-Wirkverbrauchzählern für direkten
Anschluß (Klassen 1 und 2)
Contrôle de réception des compteurs statiques d'énergie active pour courant alternatif et
à branchement direct (classes 1 et 2)
Ta slovenski standard je istoveten z: EN 61358:1996
ICS:
17.220.20 0HUMHQMHHOHNWULþQLKLQ Measurement of electrical
PDJQHWQLKYHOLþLQ and magnetic quantities
SIST EN 61358:1997 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 61358:1997
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SIST EN 61358:1997
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SIST EN 61358:1997
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SIST EN 61358:1997
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SIST EN 61358:1997
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SIST EN 61358:1997
NORME
CEI
INTERNATIONALE IEC
1358
INTERNATIONAL
Première édition
STANDARD
First edition
1996-04
Contrôle de réception des compteurs statiques
d'énergie active pour courant alternatif et
à branchement direct (classes 1 et 2)
Acceptance inspection for direct connected
alternating current static watt-hour meters
for active energy (classes 1 and 2)
© CEI 1996 Droits de reproduction réservés — Copy
right — all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in
utilisée sous quelque forme que ce soit et par aucun pro- any form or by any means, electronic or mechanical,
cédé, électronique ou mécanique, y compris la photocopie et including photocopying and microfilm, without permission
les microfilms, sans raccord écrit de l'éditeur. in writing from the publisher.
Bureau Central de la Commission Electrotechnique Internationale 3, rue de Varembé Genève, Suisse
Commission Electrotechnique Internationale CODE PRIX
International Electrotechnical Commission
P
RICE CODE
IEC Mewityliapomaa 3neln'pot'exHHgecltafi MOMHCCHm
Pour prix, voir catalogue en vigueur
• •
For price, see current catalogue
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SIST EN 61358:1997
1358 ©IEC:1996 – 3 –
CONTENTS
Page
FOREWORD 7
INTRODUCTION 9
Clause
1 Scope 11
2 General remarks 11
3 Normative references 13
4 Definitions 15
5 Acceptance conditions for batches 19
5.1 100 % inspection 19
5.2 Sampling inspection 19
6 Place of inspection 19
7 Test conditions 21
7.1 Reference conditions 21
7.2 Uncertainty of measurement 23
7.3 Cover and seal 23
8 Inspection and test procedure 23
8.1 Preheating 23
8.2 Test no. 1: AC voltage test 23
8.3 Test no. 2: Test of no-load condition 25
8.4 Test no. 3: Test of starting condition 27
8.5 Tests nos. 4 to 9: Tests of accuracy requirements 27
8.6 Test no. 10: Verification of meter constant 27
9 Requirements corresponding to different inspection procedures 29
9.1 100 % inspection 29
9.2 Sampling inspection 29
Tables
1 Reference conditions 21
2 Uncertainty of measurement 23
3 AC voltage tests 25
4 Starting current 27
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SIST EN 61358:1997
1358 ©IEC:1996 — 5 —
Page
Tables
5 Test points and limits of errors 27
6 Acceptance number c 29
7 Example of using random numbers 31
8 Sampling plans 33
9 Double sampling plan 37
10 Specified values for the standard deviation method 41
11 Specified values for the average range method 43
12a Operating characteristic curves N<_
100 46
12b Operating characteristic curves 101 N <_ 500 47
12c Operating characteristic curves 501 s N <_ 1 000 48
13a Acceptance trapezium, T. 3,5 % 49
13b Acceptance trapezium, T. 3,0 % 50
13c Acceptance trapezium, T. 2,5 % 51
14 Inspection sheet 52
15 Random numbers 53
Figures
1 Diagram of the single sampling plan 35
2 Diagram of the double sampling plan 39
3 Acceptance trapezium (standard deviation method) 41
4 Acceptance trapezium (average range method) 43
Annexes
A Symbols 55
B Bibliography 58
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SIST EN 61358:1997
1358 ©IEC:1996 — 7 —
INTERNATIONAL ELECTROTECHNICAL COMMISSION
ACCEPTANCE INSPECTION FOR DIRECT CONNECTED ALTERNATING
CURRENT STATIC WATT-HOUR METERS FOR ACTIVE ENERGY
(CLASSES 1 AND 2)
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization
comprising all national electrotechnical committees (IEC National Committees). The object of the IEC is to
promote international cooperation on all questions concerning standardization in the electrical and
electronic fields. To this end and in addition to other activities, the IEC publishes International Standards.
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. The 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 the 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 National Committees.
3) The documents produced have the form of recommendations for international use and are published in the
form of standards, technical reports or guides and they are accepted by the National Committees in that
sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the
subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 1358 has been prepared by IEC 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
13/1093/FDIS 13/1110/RVD
Full information on the voting for the approval of this standard can be found in the repo rt
on voting indicated in the above table.
Annex A forms an integral pa of this standard.
rt
Annex B is for information only.
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SIST EN 61358:1997
1358 ©IEC:1996 – 9 –
INTRODUCTION
This International Standard describes, in some detail, methods for acceptance inspection,
and testing of newly manufactured static watt-hour meters delivered in quantities of
50 and above. IEC 514 serves as a reference document and annex A of that standard
should be consulted for explanatory notes concerning sampling procedures.
In this standard, wider error limits than those for type tests specified in the relevant
publications have been allowed because:
- acceptance testing conditions have wider tolerances than those for type tests;
– displacing of the zero axis is not applicable for acceptance testing;
–
the effects of handling of meters are taken into account.
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SIST EN 61358:1997
1358 ©IEC:1996 – 11 –
ACCEPTANCE INSPECTION FOR DIRECT CONNECTED ALTERNATING
CURRENT STATIC WATT-HOUR METERS FOR ACTIVE ENERGY
(CLASSES 1 AND 2)
1 Scope
The methods and procedures included in this International Standard apply to newly manu-
factured direct connected alternating current static watt-hour meters of classes 1 and 2,
covered by IEC 1036, which are produced and delivered in quantities of 50 and above.
They provide for 100 % inspection or sampling inspection for acceptance by the purchaser.
2 General remarks
2.1 Two methods of acceptance inspection are proposed, namely:
– 100 % inspection, and
– sampling inspection.
2.2 The 100 % inspection consists of testing all the meters of a batch.
2.3 The sampling inspection is based upon the principles of mathematical statistics and
as a consequence certain specified risks are undertaken both by the manufacturer and
the purchaser. However, sampling inspection generally is more economical than 100 %
inspection.
In this standard, sampling inspection has been planned so that, in practice, the quality
of the meter batches can be judged with nearly the same confidence as with 100 %
inspection.
2.4 Two methods of sampling inspection are described:
– inspection by attributes;
- inspection by variables.
These two methods have been chosen so that the judgement of quality is virtually the
same for both methods.
2.5 Inspection by attributes gives results indicating conformity or non-conformity.
It shall be applied when the characteristics under inspection cannot be measured.
It shall also be applied when a characteristic can be measured but the values are not of
normal distribution (Laplace-Gauss).
It may be applied, when the distribution is approximately normal, in place of inspection by
variables.
The advantage of inspection by attributes is its simplicity of application.
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SIST EN 61358:1997
1358 ©IEC:1996 - 13 -
2.6 Inspection by
variables gives additional information but it is applicable only when the
values of a characteristic are measurable and when those values are approximately
normally distributed. In these circumstances, inspection by variables is the recommended
method.
The advantage of inspection by variables is a smaller sample size than by attributes for
the same risk of decision. However, it requires more calculation.
The test results are represented by:
= sample mean as an estimation of the batch mean;
s =
standard deviation as an estimation of the dispersion of the characteristics x in
= average range the batch.
NOTE - The average range is easier to calculate than the standard deviation. However, when suitable
calculating means are available for making a decision and for preparing additional information, the use of
the standard deviation enables the efficiency of the method to be increased for the same sample size.
2.7 Inspection by variables is based on normally distributed values. It is recommended to
test whether the sample is normally distributed, using e.g. :
- The "w/s" test of David, Hartley and Pearson.
For details of the test procedures see [i]*
w(x
For this test only the figures - x ) and s are needed.
max min
- The Wilk-Shapiro test.
For details of the test procedures see [2].
-
The Pearson chi-square test.
3 Normative references
The following normative documents contain provisions which, through reference in this
text, constitute provisions of this International Standard. At the time of publication, the
editions indicated were valid. All normative documents are subject to revision, and pa
rties
to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent editions of the normative documents indicated
below. Members of IEC and ISO maintain registers of currently valid International
Standards.
IEC 410: 1973,
Sampling plans and procedures for inspection by attributes
IEC 514: 1975, Acceptance inspection of Class 2 alternating-current watthour meters
IEC 1036: 1990,
Alternating current static watt-hour meters for active energy (classes 1
and 2)
ISO 3534-1: 1993, Statistics - Vocabulary and symbols - Pa rt
1: Probability and general
statistical terms
ISO 3534-2: 1993,
Statistics - Vocabulary and symbols - Part 2: Statistical quality control
• Figures in square brackets refer to the bibliography given in annex B.
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SIST EN 61358:1997
1358 © IEC:1996 -15 -
4 Definitions
For the purpose of this International Standard, the following definitions apply.
For definitions concerning meters, reference is made to IEC 1036. The majority of the defi-
nitions of sampling techniques are generally in accordance with [3] and with ISO 3534-1
and ISO 3534-2.
4.1 batch: Definite quantity of meters of the same type, of the same voltage and current
rating and the same register, delivered by one supplier, manufactured or produced under
conditions which are presumed uniform.
4.2 batch size: Number N of meters in a batch. [ISO]
4.3 sample: Meters taken at random for inspection from a batch.
4.4
sample size: Number n of meters in the sample. [ISO]
4.5 100 % inspection: Inspection of every meter in a batch.
4.6 sampling inspection: Inspection of a limited number of meters, taken at random
from the batch, according to a prescribed sampling plan. [ISO, modified]
4.7 sampling plan: Plan according to which one or more samples are taken to obtain
information and possibly to reach a decision. [ISO, modified]
4.8 characteristic (quality characteristic): Property (e.g. dielectric strength, starting,
accuracy at one test point) of a meter which contributes to the quality and which helps
to differentiate between the meters of a given batch. The differentiation may be either
quantitative (by variable) or qualitative (by attributes).
If it is measurable, its value for a given meter i is indicated by xi. [ISO, modified]
4.9 defect: Failure of a meter to meet a standard with respect to a characteristic. [ISO]
modified]
4.10 defective meter: Meter having one or more defects. [ISO, modified]
4.11 Curve showing, for a given sampling plan, the
operating characteristic curve:
probability of acceptance of a batch as a function of its actual quality for a given charac-
teristic. [ISO, modified]
4.12 inspection by attributes: Inspection whereby ce rtain characteristics of the sample
meters are evaluated, classified as conforming or not conforming to the requirements, the
number of defective meters counted and used as the basis for judgement of the batch
(EOQC).
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SIST EN 61358:1997
1358 © IEC:1996 –17 –
4.13 acceptance number:
Maximum permitted number of defects in a sample for in-
spection by attributes.
4.14 inspection by variables:
Inspection whereby certain characteristics of the sample
meters (e.g. a meter error for a particular current) are measured with respect to a
continuous scale (e.g. in per cent), and their mean value, the standard deviation or the
average range calculated and used as the basis for judgement of the batch.
4.15 sample mean x: Arithmetic mean of values xi
for a characteristic (e.g. a meter error
for a particular current) in the sample:
n
r
xi
i =
1
X =
n
4.16 range w: Difference between the maximum and minimum observed values of a given
characteristic in a subgroup:
I
= I xmax - xmin
W
for subgroup j.
NOTE - For the purpose of this standard, the size m of a subgroup j is 5 and there are r subgroups in a
sample.
4.17
average range w: Arithmetic mean of the r ranges wj of the r subgroups in a
sample:
wj
l=1
W
r
NOTE - This is an estimation of the dispersion of the characteristic x in a batch.
4.18 standard deviation of the sample:
s=
NOTE - This is an estimation of the dispersion of the characteristic x in a batch.
4.19
acceptance trapezium: Graph, with control limits, on which are plotted two
corresponding statistical values (i.e. sample mean z and either standard deviation s or
average range w), for each sample.
4.20 (AQL):
acceptable quality level For given characteristic, maximum percentage
of defective meters in a batch that, for the purpose of sampling inspection, can be
considered satisfactory (EOQC).
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SIST EN 61358:1997
1358 © IEC:1996 - 19 -
5 Acceptance conditions for batches
A batch is deemed to comply with the requirements of this standard and shall be accepted
if for each inspected characteristic the proportion of defective meters does not exceed the
following specified values.
5.1 100 % inspection
The tests shall be made according to clause 8.
The number of meters failing the test shall not exceed the acceptance number given
in table 6.
5.2
Sampling inspection
In the case of sampling inspection, the above conditions shall be considered satisfied
when for each characteristic of the meters in the batch:
- for inspection by attributes, the number of defective meters in the sample is smaller
than or equal to the acceptance number given in table 8;
-
for inspection by variables, the graphically presented test result is within the
acceptance trapezium or the calculated test result does not exceed the specified limits
(see 9.2.3).
NOTE - The risk of a wrong interpretation of the results can be read off from the operating characteristic
curves of tables 12a, 12b and 12c.
6 Place of inspection
The inspection shall be carried out by mutual agreement:
- on the manufacturer's premises, but on test benches other than those on which the
adjustments were made;
- or on the purchaser's test benches;
-
or on other agreed test benches.
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SIST EN 61358:1997
1358 ©IEC:1996 - 21 -
7 Test conditions
7.1 Reference conditions
Tests shall be carried out under conditions given in table 1.
Table 1 - Reference conditions
Permissible tolerances
Influence quantity Reference value
Ambient temperature 1> Reference temperature or, ±2 °C
in its absence, 23 °C
Voltage Reference voltage ±1,5 %
Frequency Reference frequency ±0,5 %
Sinusoidal voltages and currents Distortion factor less than 5 %
Waveform
Induction value which causes a
Magnetic induction of external Magnetic induction equal to zero
variation of error not greater
origin at the reference frequency
than ±0,3 % but should in any
case be smaller than 0,05 mT2)
1) For any ambient temperature outside the range 21 °C to 25 °C, but within the range 15 °C to 30 °C, it is
permissible to apply a correction for the reference temperature of 23 °C, using the mean temperature
coefficient of the meter type as declared by the manufacturer.
2)
The test consists of:
a) for a single-phase meter, determining the errors first with the meter normally connected to the mains
and then after inverting the connections to the current circuits as well as to the voltage circuits.
Half of the difference between the two errors is the value of the variation of error. Because of
the unknown phase of the external field, the test should be made at 0,1 at unity power factor
/b
and 0,2 /b at 0,5 power factor;
at unity power factor, after each
b) for a three-phase meter, making three measurements at 0,1
/b
of which the connections to the current circuits and to the voltage circuits are changed over 120°
while the phase sequence is not altered. The greatest difference between each of the errors so
determined and their average value is the value of the variation of error.
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SIST EN 61358:1997
1358 ©IEC:1996 — 23 —
7.2
Uncertainty of measurement
The measuring instruments and other apparatus used for the tests shall be such that the
overall uncertainty of measurement does not exceed the following values:
Table 2 — Uncertainty of measurement
Class of meter
Power factor
1 2
1
0,2 % 0,4 %
0,6 % 0,5 inductive
0,3 %
7.3 Cover and seal
The meters shall be inspected and tested with their covers on and manufacturer's seal
unbroken.
The base and cover shall show no signs of damage.
For sampling procedure damaged meters shall be replaced.
8 Inspection and test procedure
The quality of the batch of meters shall be checked by applying the inspection and test
procedure detailed in this clause.
NOTE — If mechanical aspects have to be tested, the conditions should be agreed on between the parties.
Preheating
8.1
Before any test is made, the circuits shall have been energized for a time sufficient to
reach thermal stability (see 3.6.13 of IEC 1036).
8.2
Test no. 1: AC voltage test
The a.c. voltage test shall be carried out in accordance with table 3.
The test voltage shall be substantially sinusoidal, having a frequency between 45 Hz
and 65 Hz, and applied for 1 min. The power source shall be capable of supplying at least
500 VA. During this test no flashover, disruptive discharge or puncture shall occur.
During the tests relative to earth, the auxiliary circuits with reference voltage equal to or
below 40 V shall be connected to earth.
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SIST EN 61358:1997
1358 © IEC:1996 – 25 –
Table 3 – AC voltage tests
Test voltage r.m.s Points of application of the test voltage
2 kV A) Tests to be carried out with the case closed, the cover and terminal covers
in place
a) between, on the one hand, all the current and voltage circuits as well
as the auxiliary circuits whose reference voltage is over 40 V, connected
together, and, on the other hand, earth;
b) between circuits not intended to be connected together in service
Il
B) Additional tests for insulating encased meters of protective class
a) between, on the one hand, all the current and voltage circuits as well as
4 kV
the auxiliary circuits whose reference voltage is over 40 V, connected
(for test in item a))
together, and, on the other hand, earth 1l ;
b) a visual inspection for compliance with the conditions of protective
class Il;
c) between, on the one hand, all conductive parts inside the meter
40 V
connected together and, on the other hand, all conductive parts, outside
(for test in item c))
the meter case that are accessible with the test finger, connected
together2l
B) is to be carried out with the case closed, and the cover and terminal covers in place.
1) The test in item a) of pa rt
2)
The test in item c) of part B) is not necessary if the test in item b) leaves no doubt.
8.3 Test no. 2: Test of no-load condition
For this test the current circuit(s) shall be open circuit and a voltage of 115 % of the
reference voltage shall be applied to the voltage circuits.
The minimum test period At shall be:
600 . 106
(min) for meters of class 1
At
k.m
.U '/max
480.106
^
(min) for meters of class 2
At
k . m .
Un ' /max
where
is the number of pulses emitted by the output device of the meter per kilowatthour
k
(imp/kWh);
m is the number of measuring elements;
Un is the reference voltage in volts;
is the maximum current in amperes.
/max
During this test the test output device of the meter shall not emit more than one pulse.
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SIST EN 61358:1997
1358 ©IEC:1996 - 27 -
8.4 Test no. 3: Test of starting condition
With the meter energized at reference voltage and connected as shown in the diagram of
connections, the meter shall start and continue to register at a current shown in table 4.
Table 4 - Starting current
Class of meter
Power factor
1 2
Starting current 0,004 0,005
1
/b
/b
8.5 Tests nos. 4 to 9: Tests of accuracy requirements
The tests of accuracy requirements for single-phase and polyphase meters shall be
carried out at the current values and power factor values given in table 5, without waiting
for the thermal equilibrium to be attained.
Table 5 - Test points and limits of errors
For polyphase, Percentage
Test
Current Power Number of
error limits for
whether
no.
factor phases of
balanced or meter of class
the meter
unbalanced
1 2
4 0,05 it.
Single and Balanced ±2,5 ±3,5
polyphase
5 /b 1
Single and Balanced ±1,5 ±2,5
polyphase
6
/b 0,5 Single and Balanced ±2,0 ±3,0
inductive polyphase
7 1 Polyphase 1 phase loaded
±2,5 ±3,5
It)
8
lb 1 Polyphase 1 phase loaded
±2,5 ±3,5
(different phase
from test no. 7)
1 Single and Balanced
±1,5 ±2,5
9 /max
polyphase
NOTE - The test sequence must start at test no. 4 and finish at test no. 9.
8.6 Test no. 10: Verification of meter constant
When measuring a given amount of energy, the increment of the display and the energy
calculated from the number of output pulses emitted during this test from the test output
shall not differ by more than ±0,2 %.
The test shall be done for each meter on at least one tariff register.
NOTE – The amount of energy used for this test should be sufficiently high to be able to resolve a ±0,2 %
difference.
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SIST EN 61358:1997
1358 ©IEC:1996 - 29 -
9 Requirements corresponding to different Inspection procedures
The inspection method shall be fixed by mutual agreement between the parties and all
tests shall be carried out either by 100 % inspection, or sampling inspection.
9.1 100 % inspection
All meters of a batch shall be tested.
9.1.1 Acceptance number c
A meter batch shall be considered as conforming to the requirements of tests nos. 2 to 9
when, for each test, the number of defective meters is not more than c as given in table 6
and when the accumulated number of defective meters for the tests nos. 2 to 9 is not
bigger than two times the acceptance number c of table 6.
Table 6 - Acceptance number c
Batch size N Values of c
Test no. Kind of test
0
1 AC voltage test -
50 to 149 1
150 to 249 2
2 Running with no load
250 to 349 3
350 to 449 4
3 Starting 450 to 549 5
550 to 649 6
650 to 749 7
750 to 849 8
4 to 9 Accuracy
850 to 949 9
950 to 1 000 10
0
10 Meter constant -
9.1.2 Procedure to be applied with regard to defective meters
If the acceptance conditions are satisfied, the defective meters shall be repaired or
replaced by meters fulfilling all the conditions required.
If the acceptance numbers are exceeded, then the results shall be discussed between
manufacturer and purchaser and, where required, meter(s) shall be opened and examined.
9.2 Sampling inspection
When sampling inspection is used, the purchaser's risk of accepting a poor quality or the
manufacturer's risk of rejecting a good quality shall be taken into account.
The risk for every one of the characteristics can be read from the operating characteristics
curves (see 4.11 and tables 12a, 12b and 12c).
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SIST EN 61358:1997
Oc
1358 IEC:1996 – 31 –
9.2.1 General remarks for sampling inspection
9.2.1.1 Assumptions and selection of the sample
The decision regarding conformity of a batch of N
meters to the requirements of this
standard shall be taken in accordance with the sampling plans in table 8 which are based
upon the AQLs and manufacturer's risk a as follows:
Depending upon the sample size:
–
AQL = 1 %, a = 5 % to 10 % for tests nos. 2 to 9;
– AQL = 0,2 %, a = 3 % to 8 % for tests nos. 1 and 10.
NOTE - It would be desirable to have an AQL equal to zero, but this is possible only with 100 % inspection.
An AQL different from zero is permitted only in order to make sampling inspection possible.
The sampling plans are valid for batches from 50 up to and including 1 000 meters.
Quantities larger than 1 000 meters shall be subdivided accordingly into batches of 500 up
to 1 000 meters.
The inspection shall be carried out on a sample of size n (for sample size n, see table 8).
The sample shall be chosen to ensure random selection, either by using the serial numbers of
the meters in connection with random numbers (e.g. table 15) or by any other random selec-
tion method which is more favourable from the economic point of view.
Example of using random numbers according to table 15.
The consecutive set of serial numbers of a batch are from 100 to 300.
A list of three-digit numbers is established by choosing the numbers situated at the
intersections of three columns e.g. columns nos. 1, 11 and 21 and of the successive lines
starting with line no. 6 (the numbers 1, 11, 21 and 6 may be freely chosen):
Table 7 – Example of using random numbers
Random numbers
Numbers of sample meters
908
795
295 First sample meter')
191 Second sample meter))
518
524
428
609
329
Third sample meter1l
152
etc.
1) The random numbers come within the range of the batch serial numbers.
Duplicated random numbers and those falling outside of the set of serial numbers
are disregarded.
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SIST EN 61358:1997
1358 ©IEC:1996 - 33 -
9.2.1.2 Sampling plans
The sampling plans are given in table 8 and explanations are given in 9.2.2 and 9.2.3.
Table 8 - Sampling plans
Test
Kind Sampling plans for inspection by attributes Sampling plans for inspection
no. of test Batch sizes
by variables
Batch sizes
50 SN5100 101
1015NG500 501.5N51 000
2)
n d^ n2 c2
C^ n ^ C ^ n C^ d n2 c2 n n n
1 1
1
AC voltage
tests 15 0 30 0 — — — 40 0 — — — — —
2 Running with
no load 15 0 30 0 2 30 1 40 0 2 40 2 — —
3 Starting
15 0 30 0 2 30 1 40 0 2 40 2 — —
4 to 9 Accuracy.» 15 0 30 0 2 30 1 40 0 2 40 2 15^1 30 40
10 Meter
constant 15 0 30 0 — — — 40 0 — — — — — —
N = batch size
n = sample size
n 1 = first sample size
c1 =
acceptance number for the first sample
d1 = rejection number for the first sample (only when double sampling plan is used)
n2 = second sample size
c2 = total acceptance number when both first and second samples have been taken
1)
Inspection by variables is recommended and the samples shall be taken from the first selection of samples
chosen for tests nos. 1 to 3.
2)
The sample size of n = 15 may be applied when the quality of the small batch i
...
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