SIST EN 60255-121:2014

SLOVENSKI STANDARD
SIST EN 60255-121:2014
01-september-2014
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Measuring relays and protection equipment - Part 121: Functional requirements for
distance protection
/
Relais de mesure et dispositifs de protection - Partie 121: Exigences fonctionnelles pour
protections de distance
Ta slovenski standard je istoveten z: EN 60255-121:2014
ICS:
29.120.70 Releji Relays
SIST EN 60255-121:2014 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 60255-121:2014

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SIST EN 60255-121:2014


EUROPEAN STANDARD EN 60255-121

NORME EUROPÉENNE

EUROPÄISCHE NORM
July 2014
ICS 29.120.70

English Version
Measuring relays and protection equipment - Part 121:
Functional requirements for distance protection
(IEC 60255-121:2014)
Relais de mesure et dispositifs de protection - Partie 121: Messrelais und Schutzeinrichtungen - Teil 121:
Exigences fonctionnelles pour protection de distance Funktionsanforderungen für den Distanzschutz
(CEI 60255-121:2014) (IEC 60255-121:2014)
This European Standard was approved by CENELEC on 2014-04-11. 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, 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: Avenue Marnix 17, B-1000 Brussels
© 2014 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
 Ref. No. EN 60255-121:2014 E

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SIST EN 60255-121:2014
EN 60255-121:2014 - 2 -
Foreword
The text of document 95/319/FDIS, future edition 1 of IEC 60255-121, prepared by IEC/TC 95
"Measuring relays and protection equipment" was submitted to the IEC-CENELEC parallel vote and
approved by CENELEC as EN 60255-121:2014.
The following dates are fixed:
– latest date by which the document has to be implemented at (dop) 2015-01-11
national level by publication of an identical national
standard or by endorsement
– latest date by which the national standards conflicting with (dow) 2017-04-11
the 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 [and/or CEN] shall not be held responsible for identifying any or all such
patent rights.
Endorsement notice
The text of the International Standard IEC 60255-121:2014 was approved by CENELEC as a
European Standard without any modification.

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SIST EN 60255-121:2014
- 3 - EN 60255-121:2014
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.

NOTE 1 When 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 series International electrotechnical vocabulary - -
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 61869-2 2012 Instrument transformers -- Part 2: EN 61869-2 2012
Additional requirements for current
transformers
IEC 61869-5 2011 Instrument transformers -- Part 5: EN 61869-5 2011
Additional requirements for capacitor
voltage transformers

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SIST EN 60255-121:2014

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SIST EN 60255-121:2014




IEC 60255-121

®


Edition 1.0 2014-03




INTERNATIONAL



STANDARD




NORME



INTERNATIONALE
colour

inside










Measuring relays and protection equipment –

Part 121: Functional requirements for distance protection




Relais de mesure et dispositifs de protection –

Partie 121: Exigences fonctionnelles pour protection de distance
















INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE

PRICE CODE
INTERNATIONALE

CODE PRIX XG


ICS 29.120.70 ISBN 978-2-8322-1399-5



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 60255-121:2014
– 2 – IEC 60255-121:2014 © IEC 2014
CONTENTS
FOREWORD . 9
1 Scope . 11
2 Normative references . 11
3 Terms and definitions . 12
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 . 15
4.4.1 Faulted phase identification . 15
4.4.2 Directional signals . 15
4.4.3 Distance protection function characteristics . 15
4.4.4 Distance protection zone timers . 16
4.5 Binary output signals . 16
4.5.1 General . 16
4.5.2 Start (pickup) signals . 16
4.5.3 Operate signals . 17
4.5.4 Other binary output signals . 17
4.6 Additional influencing functions/conditions . 17
4.6.1 General . 17
4.6.2 Inrush current . 17
4.6.3 Switch onto fault/trip on reclose . 17
4.6.4 Voltage transformer (VT) signal failure (loss of voltage) . 17
4.6.5 Power swings . 18
4.6.6 Behavior during frequencies outside of the operating range . 18
5 Performance specifications . 18
5.1 General . 18
5.2 Effective and operating ranges . 18
5.3 Basic characteristic accuracy under steady state conditions . 19
5.3.1 General . 19
5.3.2 Determination of accuracy related to time delay setting . 19
5.3.3 Disengaging time . 20
5.4 Dynamic performance . 20
5.4.1 General . 20
5.4.2 Transient overreach (TO) . 20
5.4.3 Operate time and transient overreach (SIR diagrams) . 21
5.4.4 Operate time and transient overreach (CVT-SIR diagrams). . 21
5.4.5 Typical operate time . 21
5.5 Performance with harmonics . 22
5.5.1 General . 22
5.5.2 Steady-state harmonics tests . 23
5.5.3 Transient LC oscillation tests . 23
5.6 Performance during frequency deviation . 23
5.6.1 General . 23
5.6.2 Steady state testing during frequency deviation . 23
5.6.3 Transient testing during frequency deviation . 23
5.7 Double infeed tests . 24

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SIST EN 60255-121:2014
IEC 60255-121:2014 © IEC 2014 – 3 –
5.7.1 General . 24
5.7.2 Single line, double infeed system . 24
5.7.3 Double line, double infeed system . 24
5.8 Instrument transformer (CT, VT and CVT) requirements . 25
5.8.1 General . 25
5.8.2 CT requirements . 25
6 Functional tests . 29
6.1 General . 29
6.2 Rated frequency characteristic accuracy tests . 29
6.2.1 General . 29
6.2.2 Basic characteristic accuracy under steady state conditions . 30
6.2.3 Basic directional accuracy under steady state conditions . 43
6.2.4 Determination of accuracy related to time delay setting . 48
6.2.5 Determination and reporting of the disengaging time . 48
6.3 Dynamic performance . 50
6.3.1 General . 50
6.3.2 Dynamic performance: operate time and transient overreach
(SIR diagrams) . 51
6.3.3 Dynamic performance: operate time and transient overreach
(CVT-SIR diagrams) . 61
6.3.4 Dynamic performance: transient overreach tests. 65
6.3.5 Dynamic performance: typical operate time . 69
6.4 Performance with harmonics . 74
6.4.1 Steady state harmonics tests . 74
6.4.2 Transient oscillation tests (network simulation L-C) . 75
6.5 Performance during off-nominal frequency . 82
6.5.1 Steady state frequency deviation tests . 82
6.5.2 Transient frequency deviation tests . 85
6.6 Double infeed tests . 90
6.6.1 Double infeed tests for single line . 90
6.6.2 Double infeed tests for parallel lines (without mutual
inductance) . 96
6.6.3 Reporting of double infeed test results . 100
7 Documentation requirements . 101
7.1 Type test report . 101
7.2 Documentation . 101
Annex A (informative) Impedance characteristics . 102
A.1 Overview. 102
A.1.1 General . 102
A.1.2 Non-directional circular characteristic . 102
A.1.3 MHO characteristic . 102
A.1.4 Quadrilateral/polygonal . 104
A.2 Example characteristics . 106
A.2.1 General . 106
A.2.2 Non-directional circular characteristic (ohm) . 106
A.2.3 Reactive reach line characteristic . 106
A.2.4 MHO characteristic . 107
A.2.5 Resistive and reactive intersecting lines characteristic . 107
A.2.6 Offset MHO characteristic. . 108

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SIST EN 60255-121:2014
– 4 – IEC 60255-121:2014 © IEC 2014
Annex B (informative) Informative guide for the behaviour of timers in distance
protection zones for evolving faults . 110
Annex C (normative) Setting example . 112
Annex D (normative) Calculation of mean, median and mode. 115
D.1 Mean . 115
D.2 Median . 115
D.3 Mode . 115
D.4 Example. 115
Annex E (informative) CT saturation and influence on the performance of distance
relays . 116
Annex F (informative) Informative guide for testing distance relays based on CT
requirements specification . 119
F.1 General . 119
F.2 Test data . 120
F.3 CT data and CT model . 121
Annex G (informative) Informative guide for dimensioning of CTs for distance
protection . 125
G.1 General . 125
G.2 Example 1 . 126
G.3 Example 2 . 128
Annex H (normative) Calculation of relay settings based on generic point P expressed
in terms of voltage and current. 131
H.1 Settings for quadrilateral/polygonal characteristic . 131
H.2 Settings for MHO characteristic . 133
Annex I (normative) Ramping methods for testing the basic characteristic accuracy . 134
I.1 Relationship between simulated fault impedance and analog quantities . 134
I.2 Pre-fault condition . 134
I.3 Phase to earth faults . 134
I.4 Phase to phase faults. . 136
I.5 Ramps in the impedance plane . 139
I.5.1 Pseudo-continuous ramp . 139
I.5.2 Ramp of shots . 140
Annex J (normative) Definition of fault inception angle . 143
Annex K (normative) Capacitive voltage instrument transformer model . 145
K.1 General . 145
K.2 Capacitor voltage transformer (CVT) . 145

Figure 1 – Simplified distance protection function block diagram . 14
Figure 2 – Basic accuracy specification of an operating characteristic . 19
Figure 3 – Basic angular accuracy specifications of directional lines . 20
Figure 4 – SIR diagram – Short line average operate time . 22
Figure 5 – Fault positions to be considered for specifying the CT requirements . 26
Figure 6 – Test procedure for basic characteristic accuracy . 31
Figure 7 – Calculated test points A, B and C based on the effective range of U and I . 32
Figure 8 – Modified points B’ and C’ based on the limited setting range . 32
Figure 9 – Position of test points A, B, C, D and E in the effective range of U and I . 33
Figure 10 – Position of test points A, B’, C’, D and E in the effective range of U and I . 33

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SIST EN 60255-121:2014
IEC 60255-121:2014 © IEC 2014 – 5 –
Figure 11 – Quadrilateral characteristic showing ten test points . 34
Figure 12 – Quadrilateral characteristic showing test ramps. 35
Figure 13 – Quadrilateral characteristic showing accuracy limits . 36
Figure 14 – Quadrilateral/polygonal characteristic showing accuracy limits . 37
Figure 15 – MHO characteristic showing nine test points . 37
Figure 16 – MHO characteristic showing test ramps . 38
Figure 17 – Accuracy limits for MHO characteristic . 39
Figure 18 – Basic directional element accuracy tests . 44
Figure 19 – Directional element accuracy tests in the second quadrant. 45
Figure 20 – Directional element accuracy tests in the second quadrant. 46
Figure 21 – Directional element accuracy tests in the fourth quadrant . 46
Figure 22 – Directional test accuracy lines in the fourth quadrant . 47
Figure 23 – Position of the three-phase fault for testing the disengaging time . 49
Figure 24 – Sequence of events for testing the disengaging time . 50
Figure 25 – Power system network with zero load transfer . 51
Figure 26 – Dynamic performance: operate time and dynamic overreach (SIR diagram) . 55
Figure 27 – SIR diagram for short line: minimum operate time . 56
Figure 28 – SIR diagram for short line: average operate time . 57
Figure 29 – SIR diagram for short line: maximum operate time . 57
Figure 30 – Dynamic performance tests (SIR diagrams). 59
Figure 31 – SIR diagram for long line: minimum operate time . 61
Figure 32 – SIR diagram for long line: average operate time . 62
Figure 33 – SIR diagram for long line: maximum operate time . 62
Figure 34 – Dynamic performance: operate time and dynamic overreach (CVT-SIR
diagram) . 64
Figure 35 – CVT-SIR diagram for short line: minimum operate time . 66
Figure 36 – CVT-SIR diagram for short line: average operate time . 66
Figure 37 – CVT-SIR diagram for a short line: maximum operate time . 67
Figure 38 – Fault statistics for typical operate time . 70
Figure 39 – Frequency distribution of operate time . 73
Figure 40 – Ramping test for harmonics . 75
Figure 41 – Steady-state harmonics test . 77
Figure 42 – Simulated power system network . 78
Figure 43 – Flowchart of transient oscillation tests . 79
Figure 44 – Simulated voltages (U , U , U ) and currents (I , I , I ) . 81
L1 L2 L3 L1 L2 L3
Figure 45 – Transient oscillation tests – Operate time . 82
Figure 46 – Test points for quadrilateral characteristics . 83
Figure 47 – Test points for MHO characteristic . 83
Figure 48 – Test ramp direction for quadrilateral characteristic . 83
Figure 49 – Test ramp direction for MHO characteristic . 84
Figure 50 – Steady-state frequency deviation tests . 86
Figure 51 – Short line model for frequency deviation test . 87
Figure 52 – Flowchart of transient frequency deviation tests . 89

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SIST EN 60255-121:2014
– 6 – IEC 60255-121:2014 © IEC 2014
Figure 53 – SIR diagrams for frequency deviation tests – average operate time . 90
Figure 54 – Network model for single line tests . 91
Figure 55 – Line to earth fault . 92
Figure 56 – Line to line fault . 92
Figure 57 – Line to line to earth fault . 92
Figure 58 – Three-phase fault . 93
Figure 59 – Network model for parallel lines tests . 98
Figure 60 – Network model for current reversal test . 99
Figure A.1 – Non-directional circular characteristic with directional supervision . 102
Figure A.2 – MHO characteristic . 103
Figure A.3 – Quadrilateral/polygonal characteristics . 104
Figure A.4 – Non-directional circular characteristic (ohm) . 106
Figure A.5 – Reactive reach line characteristic . 107
Figure A.6 – MHO characteristics . 107
Figure A.7 – Resistive and reactive intersecting lines characteristics . 108
Figure A.8 – Offset MHO . 108
Figure B.1 – The same fault type evolving from time delayed zone 3 (position 1) into
time delayed zone 2 (position 2) after 200 ms . 110
Figure B.2 – Phase to earth fault in time delayed zone 3 (position 1) evolving into
three-phase fault in the same zone (position 2) after 200 ms . 111
Figure C.1 – Setting example for a radial feeder . 112
Figure C.2 – Phase to earth fault (LN) . 113
Figure C.3 – Phase to phase fault (LL) . 114
Figure E.1 – Fault positions to be considered for specifying the CT requirements . 117
Figure F.1 – Fault positions to be considered . 119
Figure F.2 – Double source network .
...