IEC 61557-6:2007

INTERNATIONAL IEC
STANDARD
CEI
61557-6
NORME
Second edition
INTERNATIONALE
Deuxième édition
2007-07
Electrical safety in low voltage distribution
systems up to 1000 V a.c. and 1500 V d.c. –
Equipment for testing, measuring or
monitoring of protective measures –
Part 6:
Effectiveness of residual current devices (RCD)
in TT, TN and IT systems
Sécurité électrique dans les réseaux
de distribution basse tension de
1 000 V c.a. et 1 500 V c.c. –
Dispositifs de contrôle, de mesure ou de
surveillance de mesures de protection –
Partie 6:
Efficacité des dispositifs à courant résiduel (DCR)
dans les réseaux TT, TN et IT
Reference number
Numéro de référence
IEC/CEI 61557-6:2007
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INTERNATIONAL IEC
STANDARD
CEI
61557-6
NORME
Second edition
INTERNATIONALE
Deuxième édition
2007-07
Electrical safety in low voltage distribution
systems up to 1000 V a.c. and 1500 V d.c. –
Equipment for testing, measuring or
monitoring of protective measures –
Part 6:
Effectiveness of residual current devices (RCD)
in TT, TN and IT systems
Sécurité électrique dans les réseaux
de distribution basse tension de
1 000 V c.a. et 1 500 V c.c. –
Dispositifs de contrôle, de mesure ou de
surveillance de mesures de protection –
Partie 6:
Efficacité des dispositifs à courant résiduel (DCR)
dans les réseaux TT, TN et IT
PRICE CODE
M
CODE PRIX
Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue
Pour prix, voir catalogue en vigueur

– 2 – 61557-6 © IEC:2007
CONTENTS
FOREWORD.3

1 Scope.5

2 Normative references.5

3 Terms and definitions .5

4 Requirements .6

5 Marking and operating instructions.9

5.1 Marking .9
5.2 Operating instructions.9
6 Tests .9

Annex A (normative) Measuring equipment for residual current protective devices
(RCDs) of type B.11

Bibliography .13

Table 1 – Calculation of operating uncertainty .

61557-6 © IEC:2007 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
ELECTRICAL SAFETY IN LOW VOLTAGE DISTRIBUTION

SYSTEMS UP TO 1000 V a.c. AND 1500 V d.c. –

EQUIPMENT FOR TESTING, MEASURING OR MONITORING

OF PROTECTIVE MEASURES –
Part 6: Effectiveness of residual current devices

(RCD) in TT, TN and IT systems

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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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.
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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 61557-6 has been prepared by IEC technical committee 85:
Measuring equipment for electrical and electromagnetic quantities.
This second edition cancels and replaces the first edition published in 1997. This edition
constitutes a technical revision.
The following changes were made with respect to the previous edition (1997):
a) title and scope complemented;
b) definitions complemented;
c) revision of requirements;
d) “tripping tests” and “non-tripping tests” subclauses complemented;

– 4 – 61557-6 © IEC:2007
e) markings complemented;
f) addition of Annex A.
The text of this standard is based on the following documents:

Enquiry draft Report on voting

85/279A/CDV 85/298/RVC
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.
This part of IEC 61557 shall be used in conjunction with Part 1.
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 a.c. and 1 500 V d.c. – 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 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.
61557-6 © IEC:2007 – 5 –
ELECTRICAL SAFETY IN LOW VOLTAGE DISTRIBUTION

SYSTEMS UP TO 1000 V a.c. AND 1500 V d.c. –

EQUIPMENT FOR TESTING, MEASURING OR MONITORING

OF PROTECTIVE MEASURES –
Part 6: Effectiveness of residual current devices

(RCD) in TT, TN and IT systems

1 Scope
This part of IEC 61557 specifies the requirements for measuring equipment applied to the
testing of the effectiveness of protective measures by regular disconnections of residual
current protective devices (RCD) in TT, TN and IT systems.
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/TR 60755, General requirements for residual current operated protective devices
IEC 60947-2, Low-voltage switchgear and controlgear – Part 2: Circuit-breakers
IEC 61008 (all parts), Residual current operated circuit-breakers without integral overcurrent
protection for household and similar uses (RCCBs)
IEC 61009 (all parts), Residual current operated circuit-breakers with integral overcurrent
protection for household and similar uses (RCBOs)
IEC 61010-1:2001, Safety requirements for electrical equipment for measurement, control, and
laboratory use – Part 1: General requirements
IEC 61557-1:2007, 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 1:
General requirements
3 Terms and definitions
For the purposes of this document, the definitions given in IEC 61557-1 and the following
definitions apply.
3.1
fault current
IΔ
current flowing to earth due to an insulation fault

– 6 – 61557-6 © IEC:2007
3.2
rated residual operating current
I
ΔN
fault current for which the residual current protective device is designed

3.3
residual operating current
I
a
fault current at which the residual current protective device is activated

3.4
test resistance
R
p
resistance by means of which a fault current for test purposes is produced
3.5
total earthing resistance
R
A
resistance between the main earthing terminal and the earth
1)
[IEV 826-04-03 ]
4 Requirements
The following requirements as well as those given in IEC 61557-1 shall apply.
4.1 Tests
4.1.1 Tripping tests
The measuring equipment shall be capable of indicating that the residual operating current of
the protective device is less than or equal to the rated residual operating current.
The tests shall be carried out with a sinusoidal, or mains-derived quasi sinusoidal test current.
The operating uncertainty of the calibrated test currents shall not exceed 0 % to +10 % of the
rated residual current with the rated residual operating current as fiducial value determined in
accordance with Table 1.
The operating uncertainty of measurement of the residual operating current shall not exceed

±10 % of the rated residual operating current as fiducial value determined in accordance with
Table 1.
If the measuring equipment is provided for the purpose of testing residual current protective
devices of 30 mA or below, installed for supplementary protection, the measuring equipment
shall be capable of providing a test of five times the rated residual operating current. The test
period shall be limited to 40 ms. When measuring the trip time, this limit of test period need not
be applied so long as the fault voltage remains below the touch voltage limit.
If the measuring equipment is capable of producing half-wave test currents, testing of residual
current protective devices (RCDs) Type A may alternatively be carried out using half-wave test
currents according to the IEC 61008 and IEC 61009 series, IEC 60947-2 and IEC/TR 60755. In
this case test equipment shall be able to test in both polarities.
––––––––
1)
IEC 60050-826:1982, International Electrotechnical Vocabulary – Part 826: Electrical installations of buildings
(withdrawn and superseded by IEC 60050-826:2004, International Electrotechnical Vocabulary – Part 826:
Electrical installations, in which this definition no longer appears).

61557-6 © IEC:2007 – 7 –
Table 1 – Calculation of operating uncertainty

Requirements or
Intrinsic uncertainty Reference conditions or Designation test in Type of
or specified operating range code accordance with test

influence quantity the relevant

parts of
IEC 61557
Intrinsic uncertainty Reference conditions A Part 6, 6.1 R

Position Reference position ± 90° E Part 1, 4.2 R
Supply voltage At the limits stated by the E Part 1, 4.2, 4.3 R
manufacturer
Temperature 0 °C and 35 °C E Part 1, 4.2 T
Resistance of the Within the limits stated by E Part 6, 4.5 T
probes the manufacturer
System voltage 85 % to 110 % of the E Part 6, 4.5 T
nominal voltage
Operating uncertainty Part 6, 4.1
2 2 2 2 2
B=±(1A+,15E++++E EEE)
1 2 3 5 8 Part 6, 4.2 R
Part 6, 4.3
A = intrinsic uncertainty
B
B []% = ±  × 100 %
E = variations
n
fiducial value
R = routine test
T = type test
4.1.2 Non-tripping tests
When a test at 50 % or less of the rated residual operating current to test the reliability of the
RCD is included, the minimum test period for general type RCDs shall be 0,3 s and for type S
RCDs it shall be 0,5 s. The protective device shall not open.
When a no trip test at 50 % or less of the rated residual operating current is included, the
operating uncertainty of the calibrated test current shall not exceed 0 % to –10 % of the
specified no tripping test current in accordance with Table 1.
NOTE If the purpose of the test is to evaluate other parameters (e.g. fault voltage) the minimum test period may
be shorter but not less than one cycle of the rated frequency.
4.2 The measuring equipment shall be capable of indicating whether the fault voltage at the

rated residual current of the protective device is less than or equal to the conventional touch
voltage limit. The test may be carried out with or without a probe.
NOTE Indication can be by displaying the value of the fault voltage or by the use of other clear indicators.
4.2.1 If a fault voltage is displayed or indicated for the residual operating current and not for
the rated residual current, this shall be indicated in the display or on the measuring equipment,
or calculated according to the following formulae.
The following condition shall be fulfilled:
I
Δ
U ≤ U ∗
F L
I
ΔN
where
– 8 – 61557-6 © IEC:2007
U is the conventional touch voltage limit.
L
4.2.2 The operating uncertainty during the measurement of the fault voltage shall not exceed

0 % to +20 % with the conventional touch voltage limit as fiducial value, determined in

accordance with Table 1.
NOTE The internal resistance of the voltage measuring equipment should be at least 0,7 kΩ/V of the full-scale

value of the measurement range. The influence of the voltage measurement on the measurement of the fault

current should be taken into consideration.

4.3 The measuring equipment shall be capable of measuring the trip time of residual current

protective devices at the rated residual operating current or shall be capable of indicating the

compliance with the maximum allowed trip time.
When measuring the trip time, the operating uncertainty shall not exceed ± 10 % with the
maximum permissible trip time as fiducial value and the influence quantities according to
Table 1.
4.4 On measuring equipment with indicators, the switching value of the indicators shall be the
conventional true value for the calculation of uncertainties, provided nothing to the contrary is
stated.
4.5 The operating uncertainty applies under the rated operating conditions stated in
IEC 61557-1 and the following:
– the protective conductor is free from extraneous voltages;
– the system voltage remains constant during the measurement;
– the circuit following the residual current protective device carries no leakage current;
– the system voltage is within 85 % to 110 % of the nominal system voltage for which the
equipment has been designed;
– the resistance of the probes is within the limits stated by the manufacturer;
– sinusoidal test current.
4.6 When testing with the rated residual operating current, the following conditions shall be
met:
– the current shall be switched on at a zero crossing;
– the test period shall be limited to the maximum allowed trip time of the residual current
protective device under test. When measuring the trip time, these limits of the test periods
need not be applied.
4.7 Prevention of danger during measurements by fault voltages exceeding 50 V within the
system under test shall be ensured. This can be achieved as follows:
– automatic disconnection in accordance with Figure 1 of IEC 61010-1 when fault voltages
with a magnitude >50 V occur;
– use of test resistances R adjustable in steps, or continuously, in such a manner that the
p
test is started with a resistance that permits current of a maximum of 3,5 mA to flow when
all parallel-connected circuits are included. An unambiguous detection shall be ensured, for
example by means of a voltmeter, as to whether this test resistance can be varied without
producing a hazardous fault voltage.
4.8 The user shall not be exposed to danger and the equipment shall not be damaged when
the measuring equipment is connected to 120 % of the nominal voltage of the distribution
system for which the measuring equipment has been designed. Protective devices shall not be
activated.
61557-6 © IEC:2007 – 9 –
4.9 The user shall not be exposed to danger and the measuring equipment shall not be

damaged when the measuring equipment is accidentally connected for 1 min with up to 173 % of

its rated voltage to earth. Protective devices may be activated.

5 Marking and operating instructions

5.1 Marking
In addition to the marking in accordance with IEC 61557-1, the following information shall be

provided on the measuring equipment.

5.1.1 Rated residual operating current or rated residual operating currents of the residual
operating protective devices for which the measuring equipment has been designed.
5.2 Operating instructions
The operating instructions shall state the following in addition to the statements given in
IEC 61557-1.
5.2.1 Where the measuring circuit has no probe and if a possible voltage between the
protective conductor and earth will influence the measurements, a warning must be included.
5.2.2 Where the measuring circuit uses the N-conductor as a probe, a warning shall be given
to test the connection between the neutral point of the distribution system and earth before the
test is started; a possible voltage between the N-conductor and the earth may influence the
measurements.
5.2.3 A warning that leakage currents in the circuit following the residual current protection
device may influence the measurements.
5.2.4 Where the fault voltage is indicated by the test equipment, a clear statement shall be
given as to whether the voltage relates to the rated residual current or to the residual operating
current of the protective device. If applicable, a note to fulfil the conditions of 4.2.1 shall also
be included.
5.2.5 The earth electrode resistance of a measuring circuit with a probe shall not exceed a
value to be stated by the manufacturer.
5.2.6 A warning that the potential fields of other earthing installations may influence the
measurement.
5.2.7 A warning that special conditions in residual current protective devices of a particular
design, for example of S-type (selective and resistance to impulse currents) shall be taken into
consideration.
5.2.8 A warning that equipment, which is connected downstream of a residual current
protective device (RCD) may cause a considerable extension of the operating time. Examples
of such equipment might be connected capacitors or running motors.
6 Tests
The following tests in addition to those required according to IEC 61557-1 shall be executed.
These tests shall be carried out at all rated residual operating currents and also, if applicable,
at 50 % and 500 % of the rated residual operating current.

– 10 – 61557-6 © IEC:2007
The test circuit shall be adapted to test both at the limits of the fault voltage for which the

equipment is designed and also at the appropriate R = R for each range.
A Amax
The test circuit shall be adapted to each test method employed. The manufacturer’s data shall

be heeded.
U
L
NOTE R =
Amax
I
ΔΝ
where
U is the conventional touch voltage limit;
L
I is the rated residual operating current.

ΔN
6.1 The operating uncertainty shall be determined in accordance with Table 1. In this process,
the intrinsic uncertainty shall be determined under the following reference conditions:
– nominal voltage of the distribution system;
– nominal frequency of the distribution system;
– reference temperature (23 ± 2) °C;
– reference position in accordance with the manufacturer's statement;
– protective conductor free from extraneous voltages;
– 100 Ω resistance of the auxiliary earth electrode in a TT system.
The operating uncertainty thus evaluated shall not exceed the limits specified in 4.1 to 4.3.
6.2 Compliance with the permissible operating uncertainty when measuring the fault voltage
shall be tested for measurements with and without a probe.
6.3 Compliance with the conditions for the internal resistance in accordance with 4.2 shall be
(type test).
tested in all measurement ranges
6.4 Compliance with the requirements under 4.6 and 4.7 shall be tested (routine test).
6.5 The overload protection in accordance with 4.8 and 4.9 shall be tested (type test).
6.6 Compliance with the tests in this clause shall be recorded.

61557-6 © IEC:2007 – 11 –
Annex A
(normative)
Measuring equipment for residual current protective

devices (RCDs) of type B
A.1 Scope
This annex specifies requirements for measuring equipment for testing the effectiveness of
protective measures with disconnection by residual current protective devices (RCD) of type B.

A.2 Requirements
The following requirements as well as those given in IEC 61557-1 shall apply.
A.2.1
In addition to the verification of the residual operating current with sinusoidal- or half-wave test
current, for testing a residual current protective device (RCD) of type B, it shall be verified, that
the operating current with a smooth direct residual current, is smaller or equal to 2 times the
rated residual operating current I If the value of the operating current is to be evaluated, a
.
∆N
continuously increasing smooth direct test current starting with 0,2 times the rated residual
current I shall be applied
∆N
NOTE A smooth direct current is a current with less than 10 % a.c. ripple (peak-to-peak).
A.2.2
If the test current increases linearly, the increase shall not be greater than 2 times I in 5 s. If
∆N
the test current increases in steps, the increase per step shall not be more than 2 times I/30
∆N
and the increase shall not be greater than 2 times I in 5 s.
∆N
A.2.3
It shall be possible to perform verifications with smooth direct residual current in both
directions of the test current.
A.2.4
The operating uncertainty for the measurement of the residual operating current shall not
exceed ±10 % of the rated residual operating current and shall comply with the values given in
Table 1 of this standard.
A.2.5
The operating uncertainty according to 4.2 of IEC 61557-1 under rated operating conditions
shall apply and the following:
– the protective conductor is free from extraneous voltages;
– the system voltage remains constant during the measurement;
– the circuit following the residual current protective device carries no leakage current;
– the system voltage is within 85 % to 110 % of the nominal system voltage for which the
equipment has been designed;
– 12 – 61557-6 © IEC:2007
– the resistance of the probes is within the limits stated by the manufacturer;

– smooth direct current.
A.2.6
It is to be ensured that the measurements do not pose any risks within the system under test

by fault voltages exceeding 120 V d.c.

This may be achieved by:
– automatic disconnection in accordance with Figure 1 of IEC 61010-1, if the fault voltage

exceeds 120 V d.c.;
– the use of test resistors R , which are fixed or adjustable and where the test starts with a
P
resistance which limits the test current to a maximum current of 15 mA d.c., included are
parallel measuring circuits.
It must be clearly ascertainable, that the test resistance may be reduced, without producing a
dangerous voltage, for example with the indication of the fault voltage.
A.3 Marking and operating instructions
In addition to the marking in accordance with IEC 61557-1 and this standard, the following
information shall be provided on the measuring equipment.
A.3.1 Explicit indication, that the me
...