Electrical safety in low voltage distribution systems up to 1 000 V AC and 1 500 V DC - Equipment for testing, measuring or monitoring of protective measures - Part 5: Resistance to earth

IEC 61557-5:2019 is available as IEC 61557-5:2019 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.IEC 61557-5:2019 specifies the requirements applicable to measuring equipment for measuring the resistance to earth using an AC voltage. IEC 61557-5:2019 cancels and replaces the second edition published in 2007. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) definitions and symbols in Clause 3 modified;
b) subclauses in Clause 4 restructured and aligned with other parts of the series;
c) limits for reduced voltages 25 V RMS or 35 V peak removed from 4.5;
d) requirements for clamps added;
e) marking for rated voltages to earth and measurement category added to Clause 5;
f) warning about absence of hazardous voltage added in Clause 5;
g) the term "percentage operating uncertainty" replaced by "operating uncertainty" in Clause 6;
h) equation for uncertainty corrected in Table 1;
i) new Annex A on test measurements with loop clamps added.

Sécurité électrique dans les réseaux de distribution basse tension au plus égale à 1 000 V c.a. et 1 500 V c.c. - Dispositifs de contrôle, de mesure ou de surveillance de mesures de protection - Partie 5: Résistance à la terre

IEC 61557-5:2019 est disponible sous forme de IEC 61557-5:2019 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.L'IEC 61557-5:2019 spécifie les exigences applicables aux appareils de mesure destinés à mesurer la résistance à la terre en utilisant une tension alternative. L'IEC 61557-5:2019 annule et remplace la deuxième édition parue en 2007. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) modification des définitions et symboles de l'Article 3;
b) réorganisation des paragraphes de l'Article 4 et alignement sur les autres parties de la série;
c) suppression des limites de tensions réduites de 25 V (valeur efficace) ou de 35 V (valeur de crête) en 4.5;
d) ajout d'exigences relatives aux pinces;
e) ajout du marquage relatif aux tensions assignées à la terre et à la catégorie de mesure à l'Article 5;
f) ajout d'un avertissement relatif à l'absence de tension dangereuse à l'Article 5;
g) remplacement du terme "incertitude de fonctionnement en pourcentage" par "incertitude de fonctionnement" à l'Article 6;
h) correction de l'équation relative à l'incertitude dans le Tableau 1;
i) ajout de l'Annexe A relative aux mesures d'essai avec des pinces de boucle.

General Information

Status
Published
Publication Date
25-Jul-2019
Current Stage
PPUB - Publication issued
Completion Date
26-Jul-2019
Ref Project

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IEC 61557-5
Edition 3.0 2019-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electrical safety in low voltage distribution systems up to 1 000 V a.c. and
1 500 V d.c. – Equipment for testing, measuring or monitoring of protective
measures –
Part 5: Resistance to earth
Sécurité électrique dans les réseaux de distribution basse tension au plus égale
à 1 000 V c.a. et 1 500 V c.c. – Dispositifs de contrôle, de mesure ou de
surveillance de mesures de protection –
Partie 5: Résistance à la terre
IEC 61557-5:2019-07(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 61557-5
Edition 3.0 2019-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electrical safety in low voltage distribution systems up to 1 000 V a.c. and
1 500 V d.c. – Equipment for testing, measuring or monitoring of protective
measures –
Part 5: Resistance to earth
Sécurité électrique dans les réseaux de distribution basse tension au plus égale
à 1 000 V c.a. et 1 500 V c.c. – Dispositifs de contrôle, de mesure ou de
surveillance de mesures de protection –
Partie 5: Résistance à la terre
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.20; 29.080.01; 29.240.01 ISBN 978-2-8322-7159-9

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 61557-5:2019 © IEC 2019
CONTENTS

FOREWORD ........................................................................................................................... 3

1 Scope .............................................................................................................................. 5

2 Normative references ...................................................................................................... 5

3 Terms and definitions ...................................................................................................... 5

4 Requirements .................................................................................................................. 7

4.1 General ................................................................................................................... 7

4.2 Output voltage ........................................................................................................ 7

4.3 Disturbance voltage ................................................................................................ 7

4.4 Permissible resistance of probe and auxiliary earth electrode ................................. 7

4.5 Electrical safety ...................................................................................................... 7

4.6 Clamps intended to measure earth loop resistances according to

IEC 60364-6:2016, Annex C, Clause C.3 ................................................................ 8

5 Marking and operating instructions .................................................................................. 8

5.1 Marking ................................................................................................................... 8

5.2 Operating instructions ............................................................................................. 8

6 Tests ............................................................................................................................... 8

6.1 General ................................................................................................................... 8

6.2 Operating uncertainty .............................................................................................. 9

6.3 Electrical safety .................................................................................................... 10

Annex A (informative) Recommended test configuration for earth loop clamps ..................... 11

A.1 General ................................................................................................................. 11

A.2 Test purpose ......................................................................................................... 11

A.3 Test result............................................................................................................. 11

Bibliography .......................................................................................................................... 12

Table 1 – Calculation of operating uncertainty ........................................................................ 9

---------------------- Page: 4 ----------------------
IEC 61557-5:2019 © IEC 2019 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL SAFETY IN LOW VOLTAGE DISTRIBUTION SYSTEMS
UP TO 1 000 V AC AND 1 500 V DC –
EQUIPMENT FOR TESTING, MEASURING OR MONITORING
OF PROTECTIVE MEASURES –
Part 5: Resistance to earth
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

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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 61557-5 has been prepared by IEC technical committee 85:

Measuring equipment for electrical and electromagnetic quantities.

This third edition cancels and replaces the second edition published in 2007. This edition

constitutes a technical revision.

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

edition:
a) definitions and symbols in Clause 3 modified;

b) subclauses in Clause 4 restructured and aligned with other parts of the series;

c) limits for reduced voltages 25 V RMS or 35 V peak removed from 4.5;
---------------------- Page: 5 ----------------------
– 4 – IEC 61557-5:2019 © IEC 2019
d) requirements for clamps added;

e) marking for rated voltages to earth and measurement category added to Clause 5;

f) warning about absence of hazardous voltage added in Clause 5;

g) the term "percentage operating uncertainty" replaced by "operating uncertainty" in

Clause 6;
h) equation for uncertainty corrected in Table 1;
i) new Annex A on test measurements with loop clamps added.
The text of this International Standard is based on the following documents:
FDIS Report on voting
85/685/FDIS 85/696/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 61557-1:2019.

A list of all parts of the IEC 61557 series, published under the general title Electrical safety in

low voltage distribution systems up to 1 000 V AC and 1 500 V DC – Equipment for testing,

measuring or monitoring of protective measures, 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.
---------------------- Page: 6 ----------------------
IEC 61557-5:2019 © IEC 2019 – 5 –
ELECTRICAL SAFETY IN LOW VOLTAGE DISTRIBUTION SYSTEMS
UP TO 1 000 V AC AND 1 500 V DC –
EQUIPMENT FOR TESTING, MEASURING OR MONITORING
OF PROTECTIVE MEASURES –
Part 5: Resistance to earth
1 Scope

This part of IEC 61557 specifies the requirements applicable to measuring equipment for

measuring the resistance to earth using an AC voltage.
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 60364-6:2016, Low voltage electrical installations – Part 6: Verification

IEC 61010-1:2010, Safety requirements for electrical equipment for measurement, control,

and laboratory use – Part 1: General requirements
IEC 61010-1:2010/AMD1:2016

IEC 61010-2-030:2017, Safety requirements for electrical equipment for measurement, control,

and laboratory use – Part 2-030: Particular requirements for equipment having testing or

measuring circuits

IEC 61010-2-032, Safety requirements for electrical equipment for measurement, control and

laboratory use – Part 2-032: Particular requirements for hand-held and hand-manipulated

current sensors for electrical test and measurement

IEC 61243-3, Live working – Voltage detectors – Part 3: Two-pole low-voltage type

IEC 61557-1:2019, Electrical safety in low voltage distribution systems up to 1 000 V AC and

1 500 V DC – Equipment for testing, measuring or monitoring of protective measures – Part 1:

General requirements
3 Terms and definitions

For the purposes of this document, the terms, definitions and symbols given in IEC 61557-1

and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
—————————

A consolidated version of this publication exists, comprising IEC 61010-1:2010 and

IEC 61010-1:2010/AMD1:2016.
---------------------- Page: 7 ----------------------
– 6 – IEC 61557-5:2019 © IEC 2019
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
resistance to earth
real part of the impedance to earth
Note 1 to entry: resistance to ground (US).

Note 2 to entry: IEC 60364-6 uses the term "earth resistance", which is considered to be the same.

[SOURCE: IEC 60050-195:1998, 195-01-18, modified – Notes 1 and 2 to entry and a symbol

have been added.]
3.2
disturbance voltage

voltage produced between two points on two separate conductors by an electromagnetic

disturbance, measured under specified conditions and superimposed on the measuring

voltage

[SOURCE: IEC 60050-161:1990, 161-04-01, modified – in alignment with the use in this

document; in addition, the deprecated term "interference voltage" has been deleted.]

3.3
earth electrode

conductive part, which may be embedded in a specific conductive medium, for example

concrete or coke, in electric contact with the Earth

[SOURCE: IEC 60050-195:1998, 195-02-01, modified – The US variant, "ground electrode"

has been omitted.]
3.4
earth electrode terminal

connection point for a probe connected to the earth electrode to be tested and that is used for

the injection of the test current required for the purpose of measurement

Note 1 to entry: In accordance with the requirements of this document, earth electrode terminals are marked "E".

3.5
earth electrode probe terminal

connection point for a probe connected to the earth electrode to be tested and that is used as

a voltage probe either connected direct to or nearest to the earth electrode for sampling

potentials during measurement

Note 1 to entry: In accordance with the requirements of this document, earth electrode probe terminals are

marked "ES".
3.6
auxiliary earth electrode terminal

terminal for connection to an additional temporary earth electrode that is used for injection of

a test current required for the purpose of measurements

Note 1 to entry: In accordance with the requirements of this document, auxiliary earth electrode terminals are

marked "H".
3.7
auxiliary earth electrode resistance
resistance of an additional earth electrode
---------------------- Page: 8 ----------------------
IEC 61557-5:2019 © IEC 2019 – 7 –
3.8
probe electrode terminal

additional temporary earth electrode used as a voltage probe for sampling potentials during

measurements

Note 1 to entry: According to the requirements of this document, probe electrode terminals are marked "S".

3.9
probe electrode resistance
resistance of an additional earth electrode
4 Requirements
4.1 General

In addition to the requirements of IEC 61557-1:2019, Clause 4, the requirements of Clause 4

of this document shall apply.
4.2 Output voltage
The output voltage present across the terminals E and H shall be an AC voltage.
4.3 Disturbance voltage

Values of influencing voltages caused by AC or DC currents from distribution systems shall be

stated by the manufacturer in the operating instructions and shall be used for the calculation

in Table 1.
4.4 Permissible resistance of probe and auxiliary earth electrode

The measuring equipment shall be capable of determining whether the maximum permissible

resistances of the probes and auxiliary earth electrodes are exceeded.
4.5 Electrical safety

No hazardous touch voltages shall appear during the measurements. This can be achieved by

a suitable design of the source for the output voltage by:

– limiting the open-circuit value of the output voltage to 50 V AC RMS or 70 V peak;

– or, limiting the short-circuit output current to 3,5 mA AC RMS or 5 mA peak in the event

that the output voltage value could exceed U ;

– if the output voltage source does not comply with either of the above requirements,

automatic disconnection of the output voltage source shall operate within a permissible

time period, in accordance with IEC 61010-1:2010/AMD1:2016, Figure 2.

Terminals shall be rated for voltages less than or equal to 50 V or, at the minimum, for a

working voltage equal to the nominal voltage of the distribution system and measurement

category II in accordance with IEC 61010-2-030.

In the event of ratings less than or equal to 50 V, a warning shall be given in the operating

instructions to check the absence of hazardous voltage on the earthing system with a

two-pole low-voltage detector according to IEC 61243-3.

Test leads and accessories in accordance with IEC 61010-031, except for earth spikes/rods,

shall, at the minimum, correspond to the rating of the terminals.
---------------------- Page: 9 ----------------------
– 8 – IEC 61557-5:2019 © IEC 2019
4.6 Clamps intended to measure earth loop resistances according to
IEC 60364­6:2016, Annex C, Clause C.3

Clamps intended to measure the earth loop resistance in accordance with IEC 60364-6:2016,

Annex C, Clause C.3, whether attached to the instrument or stand alone, shall be specified

according to IEC 61010-2-032 as Type A or Type B.

If specified for Type A, the rating shall, at a minimum, be for measurement category II.

If specified for Type B, the rating shall, at a minimum, be for measurement category II and a

warning shall be given in the operating instructions to check in advance the absence of

hazardous voltages on the earthing system with voltage testers according to IEC 61243-3.

5 Marking and operating instructions
5.1 Marking

In addition to IEC 61557-1:2019, 5.1 and 5.2, the following information shall be provided on

the measuring equipment:
– measurement range within which the maximum operating uncertainty applies;
– frequency of the output voltage;
– name of the terminals (if applicable):
– E: terminal for the earth electrode;
– ES: terminal for the probe electrode placed nearest to the earth electrode;
– S: terminal for the probe electrode;
– H: terminal for the auxiliary earth electrode;
– marking for terminals H, S, E and ES according to the requirements of 4.5;

– rated voltage to earth or measuring category and maximum voltage to earth followed by

the symbol according to IEC 61010-1:2010, Table 1, symbol 12.
5.2 Operating instructions

In addition to IEC 61557-1:2019, 5.3, the following information shall be provided in the

operating instructions:

– the range of applications (e.g. for industrial plants or others) for the equipment for

measuring resistance to earth;

– the influence of series disturbance voltages that are larger than the values stated in 4.3, if

applicable;

– a statement relating to the correct operation of the hand-driven generator (if provided);

– the designations of terminals when different from those specified in 5.1;

– if applicable, a warning shall be given in the operating instructions that in the case of

Type B clamps the absence of hazardous voltages on the earthing system shall be
checked with two-pole low-voltage detector according to IEC 61243-3.
6 Tests
6.1 General

In addition to IEC 61557-1:2019, Clause 6, the following tests shall be performed.

---------------------- Page: 10 ----------------------
IEC 61557-5:2019 © IEC 2019 – 9 –
6.2 Operating uncertainty

The maximum operating uncertainty within the measurement range to be marked or stated

shall not exceed ±30 % with the measured value as fiducial value, as determined in

accordance with Table 1 under the following reference conditions:
– nominal value of the supply voltage;
– nominal r/min of the hand-driven generator when used as a supply;
– nominal frequency of the power supply in the case of mains-operated measuring
equipment according to 6.2;
– reference temperature 23 °C ± 2 °C;
– reference position in accordance with the manufacturer's statement;
– resistances of probes and auxiliary earth electrodes at least 100 Ω;
– disturbance voltage less than 1 V.
Table 1 – Calculation of operating uncertainty
Requirements or test
Intrinsic uncertainty
Reference conditions or Designation in accordance with Type of
or influence
specified operating range code the relevant parts of test
quantity
IEC 61557
Intrinsic uncertainty Reference conditions A IEC 61557-5:2019 6.2 R
Position Reference position ±90° IEC 61557-1:2019,
E R
approximately 4.2
Supply voltage At the limits stated by the IEC 61557-1:2019,
E R
manufacturer 4.2, 4.3
Temperature 0 °C and 35 °C IEC 61557-1:2019,
E T
(± 2°) 4.2
Series disturbance See 4.3 IEC 61557-5:2019,
E T
voltage 4.3
Resistance of the 0 R to 100 R but ≤ 50 kΩ as IEC 61557-5:2019,
A A
probes and auxiliary defined by the manufacturer E 6.2 T
earth electrodes
System frequency between 99 % and 101 % of the IEC 61557-5:2019,
E T
nominal frequency 6.2
System voltage between 85 % and 110 % of the IEC 61557-5:2019,
E T
nominal voltage 6.2
Operating uncertainty IEC 61557-5:2019,
6.2
BA=±+ E R
∑ i
Key
A = intrinsic uncertainty
E = variations B % =±× 100 %
i 
R = routine test
T = type test
F = fiducial value

The operating uncertainty shall apply under the rated operating conditions given in

IEC 61557-1 and the following:

– injection of series disturbance voltages with system frequencies of 400 Hz, 60 Hz, 50 Hz,

16 2/3 Hz (± 5 %) or with DC voltage respectively across the terminals E (ES) and S or to

the earth resistance loop. The RMS value of the series disturbance voltage for equipment

with auxiliary probes shall be 3 V (± 5 %);
---------------------- Page: 11 ----------------------
– 10 – IEC 61557-5:2019 © IEC 2019

– for equipment using current clamps, the presence of interfering disturbances shall be

clearly indicated if the influence quantity exceeds the specified value of the variation E

and of the operating uncertainty. An example of a test configuration for injection of the

series disturbance voltages can be found in Annex A;

– resistance of the auxiliary earth electrode and of the probe electrodes: 0 to 100 times R

but ≤ 50 kΩ;

– system voltages between 85 % and 110 % of the nominal voltage and between 99 % and

101 % of the nominal system frequency for measuring equipment with a mains supply

and/or measuring equipment deriving its output voltage directly from the distribution

system.
6.3 Electrical safety

Check whether the conditions for the open-circuit voltage, short-circuit current and disconnect

delay stated under 4.5 are met in each of the measurement ranges (routine test).

Check whether exceeding the permissible maximum resistances for probes and auxiliary earth

electrodes is indicated (type test).
---------------------- Page: 12 ----------------------
IEC 61557-5:2019 © IEC 2019 – 11 –
Annex A
(informative)
Recommended test configuration for earth loop clamps
A.1 General

This annex gives a recommended test configuration to inject a series disturbance voltage less

than 1 V to measuring circuits of earth fault loop clamps.
A.2 Test purpose

Influence of current flow on resistance measurement (see Figure A.1 for test arrangement).

10 A ~ (16 / / 50 / 400 Hz)
0,3 Ω
100 Ω
IEC
Figure A.1 – Test arrangement

NOTE For measurement circuit ranges above 100 Ω, the values of resistances and of the current can be changed

accordingly.
A.3 Test result
Load No current 10 A; 16,67 Hz 10 A; 50 Hz 10 A; 400 Hz
Reading 107,2 Ω 108,4 Ω 108,6 Ω 109,4 Ω
Change of reading Reference value 1,12 % 1,31 % 2,05 %
---------------------- Page: 13 ----------------------
– 12 – IEC 61557-5:2019 © IEC 2019
Bibliography
IEC 60050-161:1990, International Electrotechnical Vocabulary (IEV) – Part 161:
Electromagnetic compatibility

IEC 60050-195:1998, International Electrotechnical Vocabulary (IEV) – Part 195: Earthing and

protection against electric shock
___________
---------------------- Page: 14 ----------------------
– 14 – IEC 61557-5:2019 © IEC 2019
SOMMAIRE

AVANT-PROPOS .................................................................................................................. 15

1 Domaine d'application ................................................................................................... 17

2 Références normatives ............................................................................................

...

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