SIST EN IEC 60255-181:2020

SLOVENSKI STANDARD
SIST EN IEC 60255-181:2020
01-maj-2020
Merilni releji in zaščitna oprema - 181. del: Funkcijske zahteve za frekvenčno
zaščito
Measuring relays and protection equipment - Part 181: Functional requirements for
frequency protection
Ta slovenski standard je istoveten z: EN IEC 60255-181:2019
ICS:
29.120.70 Releji Relays
SIST EN IEC 60255-181:2020 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN IEC 60255-181:2020

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SIST EN IEC 60255-181:2020


EUROPEAN STANDARD EN IEC 60255-181

NORME EUROPÉENNE

EUROPÄISCHE NORM
April 2019
ICS 29.120.70

English Version
Measuring relays and protection equipment - Part 181:
Functional requirements for frequency protection
(IEC 60255-181:2019)
Relais de mesure et dispositifs de protection - Partie 181: Messrelais und Schutzeinrichtungen - Teil 181:
Exigences fonctionnelles relatives aux protections de Funktionsanforderungen für den Frequenzschutz
fréquence (IEC 60255-181:2019)
(IEC 60255-181:2019)
This European Standard was approved by CENELEC on 2019-04-03. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden,
Switzerland, Turkey and the United Kingdom.


European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2019 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
 Ref. No. EN IEC 60255-181:2019 E

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SIST EN IEC 60255-181:2020
EN IEC 60255-181:2019 (E)
European foreword
The text of document 95/402/FDIS, future edition 1 of IEC 60255-181, prepared by IEC/TC 95
"Measuring relays and protection equipment" was submitted to the IEC-CENELEC parallel vote and
approved by CENELEC as EN IEC 60255-181:2019.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2020-01-03
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2022-04-03
document have to be withdrawn

Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.

Endorsement notice
The text of the International Standard IEC 60255-181:2019 was approved by CENELEC as a
European Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards
indicated:
IEC 60255-24 NOTE Harmonized as EN 60255-24
IEC 61000-2-4:2002 NOTE Harmonized as EN 61000-2-4:2002 (not modified)
IEC 61850-7-4 NOTE Harmonized as EN 61850-7-4
IEC 61850-9-2 NOTE Harmonized as EN 61850-9-2
1
IEC 61869-9:2016 NOTE Harmonized as EN 61869-9:— (not modified)



1
Under preparation. Stage at time of publication: FprEN 61869-9:2016.
2

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SIST EN IEC 60255-181:2020
EN IEC 60255-181:2019 (E)
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications
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.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available here:
www.cenelec.eu.

Publication Year Title EN/HD Year
IEC 60050-103 -  International Electrotechnical Vocabulary - - -
Part 103: Mathematics - Functions
IEC 60050-447 -  International Electrotechnical Vocabulary - - -
Part 447: Measuring relays
IEC 60050-601 -  International Electrotechnical Vocabulary. - -
Chapter 601: Generation, transmission and
distribution of electricity - General
IEC 60255-1 -  Measuring relays and protection equipment EN 60255-1 -
- Part 1: Common requirements
IEC 61850 series Communication networks and systems for EN 61850 series
power utility automation
IEC 61869 series Instrument transformers EN 61869 series

3

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SIST EN IEC 60255-181:2020




IEC 60255-181

®


Edition 1.0 2019-02




INTERNATIONAL



STANDARD




NORME



INTERNATIONALE
colour

inside










Measuring relays and protection equipment –

Part 181: Functional requirements for frequency protection




Relais de mesure et dispositifs de protection –

Partie 181: Exigences fonctionnelles relatives aux protections de fréquence
















INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE


INTERNATIONALE




ICS 29.120.70 ISBN 978-2-8322-6496-6



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

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SIST EN IEC 60255-181:2020
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CONTENTS
FOREWORD . 6
1 Scope . 8
2 Normative references . 9
3 Terms and definitions . 9
4 Specification of the function . 13
4.1 General . 13
4.2 Input energizing quantities / energizing quantities . 13
4.3 Binary input signals . 14
4.4 Functional logic . 14
4.4.1 Operating characteristics . 14
4.4.2 Reset characteristics . 17
4.5 Additional influencing functions/conditions . 18
4.5.1 General . 18
4.5.2 Specific characteristics for under/over frequency function . 18
4.5.3 Specific characteristics for rate of change of frequency (ROCOF)
function . 19
4.6 Binary output signals . 19
4.6.1 General . 19
4.6.2 Start (pick-up) signal . 19
4.6.3 Operate (trip) signal . 19
4.6.4 Other binary output signals . 19
5 Performance specification . 20
5.1 General . 20
5.2 Effective and operating ranges . 20
5.3 Accuracy related to the characteristic quantity . 21
5.4 Start time for under/over frequency function . 21
5.5 Start time for rate of change of frequency (ROCOF) function . 21
5.6 Accuracy related to the operate time delay setting . 22
5.7 Disengaging time . 22
5.8 Reset hysteresis and reset ratio . 22
5.9 Accuracy related to restraint/blocking elements . 23
5.10 Performance with harmonics . 23
5.11 Stability in case of sudden voltage change (phase shift and magnitude shift) . 23
5.12 Voltage input requirements . 23
6 Functional test methodology . 24
6.1 General . 24
6.2 Determination of steady state errors related to the characteristic quantity . 26
6.2.1 Accuracy of the start value . 26
6.2.2 Reset hysteresis or reset ratio determination . 32
6.3 Determination of the start time . 41
6.3.1 General . 41
6.3.2 Under/over frequency . 41
6.3.3 Rate of change of frequency . 47
6.4 Determination of the accuracy of the operate time delay . 50
6.4.1 General . 50
6.4.2 Description of test method . 50
6.4.3 Reporting of the operate time delay accuracy . 52

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6.5 Determination of disengaging time . 53
6.5.1 General . 53
6.5.2 Under/over frequency . 53
6.5.3 Rate of change of frequency . 56
6.6 Performance with harmonics . 58
6.6.1 General . 58
6.6.2 Accuracy of the under/over frequency start value in the presence of
harmonics . 58
6.6.3 Accuracy of the ROCOF start value in the presence of harmonics . 63
6.7 Stability in the case of sudden voltage change (phase shift and magnitude
change) . 65
6.7.1 General . 65
6.7.2 Performance in case of voltage phase shift and magnitude change . 65
6.7.3 Performance in case of voltage magnitude drop and restoration . 68
7 Documentation requirements . 70
7.1 Type test report . 70
7.2 Other user documentation . 71
Annex A (normative) Test signal equation with constant frequency variation (df/dt) . 72
Annex B (normative) Calculation of mean, median and mode . 73
B.1 Mean . 73
B.2 Median . 73
B.3 Mode . 73
B.4 Example. 73
Annex C (informative) Example of frequency measurement and calculation . 74
C.1 Definitions. 74
C.2 Signal observation model . 74
C.3 General requirements on frequency measurement . 76
C.3.1 General requirements on frequency measurement . 76
C.3.2 Periodic algorithm . 76
C.3.3 Analysis algorithm . 78
C.3.4 Error minimization algorithm . 79
C.3.5 Discrete Fourier transformation (DFT) . 82
Annex D (informative) Performance with inter-harmonics . 84
D.1 General . 84
D.2 Proposed test: accuracy of the under/over frequency start value . 84
D.2.1 Description of the generated frequency ramp . 84
D.2.2 Protection function settings . 85
D.2.3 Test points and calculation of frequency accuracy in the presence of
inter-harmonics . 86
D.2.4 Reporting of frequency accuracy in the presence of inter-harmonics . 86
Annex E (informative) Management of sudden frequency change without discontinuity
in voltage waveform . 87
Bibliography . 90

Figure 1 – Operate time and operate time delay setting . 11
Figure 2 – Simplified protection function block diagram . 13
Figure 3 – Underfrequency independent time characteristic . 15
Figure 4 – Overfrequency independent time characteristic . 16

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Figure 5 – ROCOF independent time characteristic (for negative or positive ROCOF) . 16
Figure 6 – Explanatory diagram for start, operate, disengage and reset . 18
Figure 7 – Example of test method for overfrequency . 26
Figure 8 – Example of test method for positive ROCOF function . 29
Figure 9 – Frequency ramps for assessing the reset hysteresis for overfrequency
functions . 33
Figure 10 – Frequency ramps for assessing the reset hysteresis for underfrequency

functions . 33
Figure 11 – Test method for measurement of reset value for ROCOF functions:
example for positive ROCOF function . 37
Figure 12 – Start time measurement of overfrequency with sudden frequency change . 42
Figure 13 – Start time measurement of overfrequency with constant slope frequency
ramp . 43
Figure 14 – Example of start time reporting for under/over frequency protection
function . 47
Figure 15 – Start time measurement of positive ROCOF function . 48
Figure 16 – Histogram for the start time test results for ROCOF. 50
Figure 17 – Operate time delay measurement of overfrequency and positive ROCOF . 51
Figure 18 – Disengaging time measurement of overfrequency with sudden frequency
change . 54
Figure 19 – Disengaging time measurement of overfrequency with constant slope
frequency ramp . 54
Figure 20 – Disengaging time measurement of ROCOF . 56
Figure 21 – Histogram for the disengaging time test results for ROCOF . 58
Figure 22 – Example of an increasing pseudo-continuous ramp for overfrequency

functions . 59
Figure 23 – Voltage signal with superimposed harmonics . 61
Figure 24 – Representation of the input energizing quantity (voltage, RMS) injection
sequence . 67
Figure 25 – Representation of the input energizing quantity (voltage, RMS) injection
sequence with the power system frequency values . 69
Figure C.1 – Zero-crossing algorithm . 77
Figure C.2 – Level-crossing algorithm . 77
Figure D.1 – Example of an increasing pseudo-continuous ramp for overfrequency
function . 84
Figure E.1 – Example of voltage waveform without discontinuity at to = 0,02 s. 88
Figure E.2 – Example of voltage waveform with discontinuity at to = 0,02 s . 89

Table 1 – Frequency protection designation . 8
Table 2 – Example of effective and operating ranges for over/under frequency
protection . 20
Table 3 – Example of effective and operating ranges for ROCOF protection . 20
Table 4 – Test points for under/over frequency function . 28
Table 5 – Reporting of the frequency accuracy . 28
Table 6 – Reporting of the frequency accuracy (alternative solution) . 29
Table 7 – Test points for ROCOF function . 31
Table 8 – Reporting of ROCOF accuracy . 32

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Table 9 – Test points of reset hysteresis for under/over frequency function . 35
Table 10 – Reporting of the reset hysteresis for over/under frequency functions . 36
Table 11 – Test points of reset value for ROCOF function . 40
Table 12 – Reporting of the reset value for ROCOF function . 40
Table 13 – Test points of start time for overfrequency function . 44
Table 14 – Test points of start time for underfrequency function . 45
Table 15 – Reporting of start time for under/over frequency functions . 46
Table 16 – Test points of start time for ROCOF function . 49
Table 17 – Reporting of typical start time for ROCOF function . 50
Table 18 – Test points to measure operate time delay . 52
Table 19 – Test points for accuracy of the operate time delay . 52
Table 20 – Reporting of operate time delay accuracy for under/over frequency
functions . 53
Table 21 – Test points of disengaging time for overfrequency function . 55
Table 22 – Test points of disengaging time for underfrequency function. 55
Table 23 – Reporting of disengaging time for over/under frequency functions . 56
Table 24 – Test points of disengaging time for ROCOF function . 57
Table 25 – Typical disengaging time for ROCOF protection . 58
Table 26 – Superimposed harmonics . 60
Table 27 – Test points for under/over frequency function in the presence of harmonics . 63
Table 28 – Test points for ROCOF function in the presence of harmonics . 64
Table 29 – Under/over frequency settings for stability tests with voltage
drop/restoration . 70
Table D.1 – Superimposed inter-harmonics . 85
Table D.2 – Test points for under/overfrequency function in the presence of inter-
harmonics . 86

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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

MEASURING RELAYS AND PROTECTION EQUIPMENT –

Part 181: Functional requirements for frequency protection

FOREWORD
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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 60255-181 has been prepared by IEC technical committee 95:
Measuring relays and protection equipment.
The text of this International Standard is based on the following documents:
FDIS Report on voting
95/402/FDIS 95/409/RVD

Full information on the voting for the approval of this International Standard can be found in
...