SIST EN 62689-2:2017
(Main)Current and voltage sensors or detectors, to be used for fault passage indication purposes - Part 2: System aspects (IEC 62689-2:2016)
Current and voltage sensors or detectors, to be used for fault passage indication purposes - Part 2: System aspects (IEC 62689-2:2016)
IEC 62689-2:2016 describes electric phenomena and electric system behaviour during faults, according to the most widely diffused distribution system architecture and to fault typologies, to define the functional requirements for fault passage indicators (FPI) and distribution substation units (DSU) (including their current and/or voltage sensors), which are, respectively, a device or a device/combination of devices and/or of functions able to detect faults and provide indications about their localization. By localization of the fault is meant the fault position with respect to the FPI/DSU installation point on the network (upstream or downstream from the FPI/DSU's location) or the direction of the fault current flowing through the FPI itself. The fault localization may be obtained
- directly from the FPI/DSU, or
- from a central system using information from more FPIs or DSUs,
considering the features and the operating conditions of the electric system where the FPIs/DSUs are installed. This part of IEC 62689 is therefore aimed at helping users in the appropriate choice of FPIs/DSUs (or of a system based on FPI/DSU information) properly operating in their networks, considering adopted solutions and operation rules (defined by tradition and/or depending on possible constraints concerning continuity and quality of voltage supply defined by a national regulator), and also taking into account complexity of the apparatus and consequent cost. This part of IEC 62689 is mainly focused on system behaviour during faults, which is the "core" of FPI/DSU fault detection capability classes described in IEC 62689-1, where all requirements are specified in detail.
Strom- und Spannungs-Sensoren oder Anzeigegeräte zur Erkennung von Kurz- und Erdschlüssen - Teil 2: Systemaspekte
Capteurs ou détecteurs de courant et de tension, à utiliser pour indiquer le passage d'un courant de défaut - Partie 2: Aspects systèmes
L'IEC 62689-2:2016 décrit les phénomènes électriques et le comportement de réseaux électriques en présence de défauts, selon l'architecture de système de distribution la plus diffusée et les typologies de défauts. Il définit les exigences fonctionnelles pour les indicateurs de passage de courant de défaut (FPI) et les unités de poste de distribution (DSU) (y compris pour leurs capteurs de courant et/ou de tension) qui sont respectivement matérialisés par un dispositif ou un dispositif/une combinaison de dispositifs et/ou de fonctions pouvant détecter des défauts et les localiser. La localisation d'un défaut est définie par la position du défaut par rapport au point d'installation des FPI/DSU sur le réseau (en amont ou en aval de l'emplacement des FPI/DSU) ou la direction du courant de défaut qui traverse le FPI. La localisation du défaut peut être obtenue:
- directement depuis le FPI/la DSU, ou
- depuis un système central, à l'aide des informations d'autres FPI ou DSU,
en tenant compte des fonctionnalités et des conditions d'exploitation du réseau électrique sur lequel les FPI/DSU sont installés. Par conséquent, l'objectif de la présente partie de l'IEC 62689 est d'aider les utilisateurs à bien choisir leur FPI/DSU (ou un système utilisant des informations de FPI/DSU) pour une exploitation optimale sur leurs réseaux, en prenant en considération les solutions adoptées et les règles d'exploitation (définies par la coutume et/ou en fonction des éventuelles contraintes relatives à la continuité et la qualité de la tension d'alimentation définies par l'organisme national de règlementation), sans oublier la complexité et le coût de l'appareil. Dans la présente partie de l'IEC 62689, le premier "niveau" de classification FPI/DSU est défini, d'après le comportement du réseau en présence de défauts. La classification FPI/DSU est développée de manière exhaustive dans l'IEC 62689-1, dans laquelle toutes les exigences sont définies.
Tokovna in napetostna zaznavala in detektorji, ki se uporabljajo za javljanje mesta okvare - 2. del: Sistemski vidiki (IEC 62689-2:2016)
Ta del standarda IEC 62689 opisuje električne pojave in obnašanje električnega sistema med okvarami skladno z najbolj razširjeno arhitekturo distribucijskega sistema in tipologijami okvar za namene opredelitve funkcionalnih zahtev za javljalnike mesta okvare (FPI) in distribucijske postaje (DSU) (vključno z njihovimi zaznavali za tok in/ali napetost), ki so naprava ali naprava/skupek naprav in/ali funkcij, ki lahko zaznajo okvare in podajo indikacije glede njihove lokalizacije.
Lokalizacija okvare pomeni mesto okvare glede na mesto namestitve javljalnika mesta okvare/distribucijske postaje v omrežju (na visoko- ali nizkonapetostni strani glede na javljalnik mesta okvare/distribucijsko postajo) ali smer okvarnega toka, ki teče skozi javljalnik mesta okvare. Lokalizacija okvare se lahko pridobi
• neposredno iz javljalnika mesta okvare/distribucijske postaje ali
• pri centralnem sistemu z uporabo informacij več javljalnikov mesta okvare ali distribucijskih postaj,
ob upoštevanju lastnosti in obratovalnih pogojev električnega sistema, v katerem so nameščeni javljalniki mesta okvare/distribucijske postaje.
Ta del standarda IEC 62689 je tako namenjen pomoči uporabnikom pri izbiri ustreznih javljalnikov mesta okvare/distribucijskih postaj (ali sistema, ki temelji na informacijah javljalnika mesta okvare/distribucijske postaje), ki pravilno delujejo v njihovih omrežjih glede na sprejete rešitve in pravila delovanja (opredeljena skladno z običaji in/ali glede na možne omejitve glede neprekinjenosti in kakovosti napajanja, ki jih opredeli nacionalni organ), pri čemer se upoštevajo tudi kompleksnost naprave in posledični stroški.
Ta del standarda IEC 62689 se osredotoča predvsem na obnašanje sistema med okvarami, kar predstavlja »jedro« razredov zmogljivosti zaznavanja okvar javljalnikov mesta okvare/distribucijskih postaj, opisanih v standardu IEC 62689-1, ki vsebuje podrobne opise vseh zahtev.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-november-2017
Tokovna in napetostna zaznavala in detektorji, ki se uporabljajo za javljanje mesta
okvare - 2. del: Sistemski vidiki (IEC 62689-2:2016)
Current and voltage sensors or detectors, to be used for fault passage indication
purposes - Part 2: System aspects (IEC 62689-2:2016)
Ta slovenski standard je istoveten z: EN 62689-2:2017
ICS:
17.220.20 0HUMHQMHHOHNWULþQLKLQ Measurement of electrical
PDJQHWQLKYHOLþLQ and magnetic quantities
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD EN 62689-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
September 2017
ICS 17.220.20
English Version
Current and voltage sensors or detectors, to be used for fault
passage indication purposes - Part 2: System aspects
(IEC 62689-2:2016)
Capteurs ou détecteurs de courant et de tension, à utiliser Strom- und Spannungs-Sensoren oder Anzeigegeräte zur
pour indiquer le passage d'un courant de défaut - Erkennung von Kurz- und Erdschlüssen -
Partie 2: Aspects systèmes Teil 2: Systemaspekte
(IEC 62689-2:2016) (IEC 62689-2:2016)
This European Standard was approved by CENELEC on 2017-06-17. 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: Avenue Marnix 17, B-1000 Brussels
© 2017 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN 62689-2:2017 E
European foreword
The text of document 38/504/FDIS, future edition 1 of IEC 62689-2, prepared by IEC/TC 38
"Instrument transformers" was submitted to the IEC-CENELEC parallel vote and approved by
CENELEC as EN 62689-2:2017.
The following dates are fixed:
(dop) 2018-03-22
• latest date by which the document has to be
implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2020-09-22
standards conflicting with 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 shall not be held responsible for identifying any or all such patent rights.
Endorsement notice
The text of the International Standard IEC 62689-2:2016 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 60044-7 NOTE Harmonized as EN 60044-7.
IEC 60044-8 NOTE Harmonized as EN 60044-8.
IEC 60721-3-4 NOTE Harmonized as EN 60721-3-4.
IEC 60870-5-101 NOTE Harmonized as EN 60870-5-101.
IEC 60870-5-104 NOTE Harmonized as EN 60870-5-104.
IEC 61850-7-2 NOTE Harmonized as EN 61850-7-2.
IEC 61850-7-3 NOTE Harmonized as EN 61850-7-3.
IEC 61869-1 NOTE Harmonized as EN 61869-1.
IEC 61869-4 NOTE Harmonized as EN 61869-4.
IEC 61869-6 NOTE Harmonized as EN 61869-6.
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 62689-1 - Current and voltage sensors or detectors, EN 62689-1 -
to be used for fault passage indication
purposes -
Part 1: General principles and
requirements
IEC 62689-2 ®
Edition 1.0 2016-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Current and voltage sensors or detectors, to be used for fault passage
indication purposes –
Part 2: System aspects
Capteurs ou détecteurs de courant et de tension, à utiliser pour indiquer
le passage d'un courant de défaut –
Partie 2: Aspects systèmes
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.20 ISBN 978-2-8322-3385-6
– 2 – IEC 62689-2:2016 © IEC 2016
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 9
2 Normative references . 9
3 Terms, definitions, abbreviations and symbols . 9
3.1 Terms and definitions related to neutral point treatment . 10
3.2 Abbreviations and symbols . 10
4 Choice of FPI/DSU requirements related to fault detection according to network
operation mode and fault type . 10
4.1 General . 10
4.2 FPIs/DSUs for isolated neutral system . 10
4.2.1 Earth fault detection . 10
4.2.2 Polyphase fault detection . 11
4.3 FPIs/DSUs for resonant earthed (neutral) system – arc-suppression-coil-
earth (neutral) system . 11
4.3.1 Earth fault detection . 11
4.3.2 Polyphase fault detection . 12
4.4 FPIs/DSUs for solidly earthed neutral systems (systems with low-impedance
earthed neutrals) . 12
4.5 FPIs/DSUs for impedance earthed neutral system (resistive impedance
earthed neutral system ) . 12
4.5.1 Earth fault detection . 12
4.5.2 Polyphase fault detection . 13
4.6 FPIs/DSUs for systems with high presence of DER . 13
4.7 Summary of FPI/DSU requirements with respect to fault detection according
to network operation mode and fault type . 13
5 Fault detecting principles according to network and fault type. 15
5.1 General . 15
5.2 Earth fault detection and neutral treatment. 18
5.2.1 General . 18
5.2.2 Earth fault detection in isolated neutral systems . 18
5.2.3 Earth fault detection in resonant earthed systems . 24
5.2.4 Overcurrent detection in absence or negligible presence of DER . 35
5.2.5 Overcurrent detection in presence of a large amount of DER
(significantly increasing short circuit current values) . 37
Annex A (informative) Example of a possible solution for fault detection through
FPIs/DSUs on closed loop feeder . 39
A.1 General . 39
A.2 Double bipole model . 39
A.3 Analysis of zero-sequence values in case of fault on a line out of the closed
loop . 40
A.4 Analysis in case of fault on the closed-loop . 42
A.5 Example of on-field application . 44
Annex B (informative) Example of fault detection coordination technique among
FPIs/DSUs and MV feeder protection relays . 45
B.1 Autonomous fault detection confirmation from FPIs/DSUs . 45
IEC 62689-2:2016 © IEC 2016 – 3 –
B.2 Fault detection confirmation from FPIs/DSUs through voltage
presence/absence detection . 48
Bibliography . 49
Figure 1 – General architecture of an FPI . 8
Figure 2 – General three-phase diagram of an earth fault in isolated neutral system . 16
Figure 3 – General three-phase diagram of an earth fault solidly earthed system
(example 2) . 17
Figure 4 – Isolated neutral system – detection of earth fault current direction from
FPI/DSU upstream from the fault location (fault downstream from the FPI’s/DSU’s
location) . 18
Figure 5 – Isolated neutral system – detection of earth fault current direction from
FPI/DSU downstream from the fault location (fault upstream from the FPI’s/DSU’s
location) . 19
Figure 6 – Isolated neutral system – vector diagrams related to Figure 4 and Figure 5 . 20
Figure 7 – Relationship between FPI/DSU regulated current threshold and earth fault
current in case of non-directional earth fault current detection. Fault downstream from
FPI/DSU A4-2 . 21
Figure 8 – Relationship between FPI/DSU regulated current threshold and earth fault
current in case of non-directional earth fault current detection. Fault downstream from
FPI/DSU A4-1 and upstream from FPI/DSU A4-2 . 22
Figure 9 – Relationship between FPI/DSU regulated current threshold and earth fault
current in case of non-directional earth fault current detection. Fault on MV busbar
(upstream from any FPI/DSU) . 23
Figure 10 – Pure resonant earthed system – detection of earth fault current direction
from FPI/DSU upstream from the fault location (fault downstream from the FPI’s/DSU’s
location) . 25
Figure 11 – Pure resonant earthed system – detection of earth fault current direction
from FPI/DSU downstream from the fault location (fault upstream from the FPI’s/DSU’s
location) . 25
Figure 12 – Pure resonant earthed system – vector diagrams related to Figure 10 and
Figure 11 . 27
Figure 13 – Resonant earthed system with inductance and permanent parallel resistor
– detection of phase to earth fault current direction from FPI/DSU upstream from the
fault location (fault downstream from the FPI’s/DSU’s location) . 28
Figure 14 – Resonant earthed system with inductance with parallel resistor system –
detection of phase to earth fault current direction from FPI/DSU downstream from the
fault location (fault upstream from the FPI’s/DSU’s location) . 28
Figure 15 – Resonant earthed system with inductance with parallel resistor system –
vector diagrams related to Figure 13 and Figure 14 . 30
Figure 16 – Earthing resistor system – detection of phase to earth fault current
direction from FPI/DSU upstream from the fault location (fault downstream from the
FPI’s/DSU’s location) . 32
Figure 17 – Earthing resistor system – detection of phase to earth fault current
direction from FPI/DSU downstream from the fault location (fault upstream from the
FPI’s/DSU’s location) . 32
Figure 18 – Earthing resistor system – vector diagrams related to Figure 16 and
Figure 17 . 34
Figure 19 – Overcurrents in a radial network without DER – correct current detection
by non-directional FPI/DSU (good sensitivity concerning overcurrent detection) . 35
– 4 – IEC 62689-2:2016 © IEC 2016
Figure 20 – Overcurrents in a radial network with negligible DER presence – correct
current detection by non-directional FPI/DSU (good sensitivity concerning overcurrent
detection) . 36
Figure 21 – Overcurrents in a radial network with a large amount of DER – unreliable
fault detection by non-directional FPIs/DSUs (incorrect detection or extremely low
sensitivity) . 38
Figure A.1 – Double bipole. 39
Figure A.2 – Cascade of double bipoles . 41
Figure A.3 – Closed loop double bipoles . 43
Figure A.4 – Equivalent model in case of fault . 43
Figure B.1 – Correctly coordinated fault selection among FPIs/DSUs and protection
relay . 46
Figure B.2 – Incorrectly coordinated selection among FPIs/DSUs and protection relay.
Case 1 . 47
Figure B.3 – Incorrectly coordinated fault selection among FPIs/DSUs and protection
relay. Case 2 . 48
Table 1 – Summary of FPI/DSU requirements referred to fault detection according to
network operation mode and fault type . 14
IEC 62689-2:2016 © IEC 2016 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CURRENT AND VOLTAGE SENSORS OR DETECTORS,
TO BE USED FOR FAULT PASSAGE INDICATION PURPOSES –
Part 2: System aspects
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
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
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Publication(s)”). 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-
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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 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 IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
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members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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 62689-2 has been prepared by IEC technical committee 38:
Instrument transformers.
The text of this standard is based on the following documents:
FDIS Report on voting
38/504/FDIS 38/511/RVD
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.
– 6 – IEC 62689-2:2016 © IEC 2016
A list of all the parts in the IEC 62689 series, under the general title Current and voltage
sensors or detectors, to be used for fault passage indication purposes, can be found on the
IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability 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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
IEC 62689-2:2016 © IEC 2016 – 7 –
INTRODUCTION
0.1 General
The IEC 62689 series is a product family standard for current and voltage sensors or
detectors, to be used for fault passage indication purposes by proper devices or functions,
indicated as fault passage indicator (FPI) or distribution substation unit (DSU), depending on
their performances.
Different names are used to indicate FPIs depending on the region of the world and on their
functionalities concerning capability to detect different kinds of faults, for instance:
• fault detector;
• smart sensor;
• faulted circuit indicator (FCI);
• short circuit indicator (SCI);
• earth fault indicator (EFI);
• test point mounted FCI.
• combination of the above.
Simpler versions, only using local information/signals and/or local communication, are called
FPI, while very evolved versions are called DSU. The latter are explicitly designed for smart
grids and based on IEC 60870-5 and IEC 61850 communication protocols.Compared to
instrument transformers, digital communication technology is subject to on-going changes
which are expected to continue in the future.
Profound experience with deep integration between electronics and instrument transformers
has yet to be gathered on a broader basis, as this type of equipment is not yet widespread in
the industry.
DSUs, besides FPI basic functions, may also optionally integrate additional auxiliary functions
such as:
• voltage presence/absence detection for medium voltage (MV) network automation, with
and without distributed energy resources presence (not for fault confirmation, which can
be a basic FPI function depending on the adopted fault detection method, neither for
safety-related aspects, which are covered by IEC 61243-5);
• measuring of voltage, current, and active and reactive power, etc., for various
applications, such as MV network automation, monitoring of power flows, etc.;
• smart grid management (such as voltage control and unwanted island operation) by
means of a proper interface with local distributed generators (DER);
• local output of collected information by means of suitable interfaces;
• remote transmission of collected information;
• others.
A general FPI scheme is outlined in Figure 1.
A DSU may have a much more complex scheme.
– 8 – IEC 62689-2:2016 © IEC 2016
A
B
C
D
E
F
G
IEC
Key
A Current (and, if necessary, voltage) sensors. 1 or 3 phases may be monitored.
B Transmission of signals between sensors and electronics.
C: Local indications (lamps, LEDs, flags, etc.).
D Analogue, digital and/or communication inputs/outputs for remote communication/commands (hard wired and/or
wireless).
E Connections to field apparatus.
F Signal conditioning, processing and indicating unit (CPIU).
G Power supply.
Current sensor(s) may detect fault current passages without any need of galvanic connection to the phase(s) (for
instance in case of cable type current sensors or of magnetic field sensor).
Not all the above listed parts or functions are necessarily included in the FPI, depending on its complexity and on
its technology. However, at least 1 one of C or D functions shall be present.
Figure 1 – General architecture of an FPI
0.2 Position of this standard in relation to the IEC 61850 series
The IEC 61850 series is intended to be used for communication and systems to support
power utility automation.
The IEC 62689 series will also introduce a dedicated namespace to support integration of
FPIs/DSUs into power utility automation.
In addition, it defines proper data models and different profiles of communication interfaces to
support the different use cases of these FPIs/DSUs.
Some of these use cases rely on the concept of extended substation, which is intended as the
communication among intelligent electronic devices (IED) through IEC 61850 located both
along MV feeders and in the main substation, for the most sophisticated FPI versions (and
therefore DSUs) (for smart grid applications, for instance). Such a profile may not be limited
to FPI/DSU devices, but may embrace features needed to support extensions of these
substations along the MV feeders connected to the main substation themselves.
IEC 62689-2:2016 © IEC 2016 – 9 –
CURRENT AND VOLTAGE SENSORS OR DETECTORS,
TO BE USED FOR FAULT PASSAGE INDICATION PURPOSES –
Part 2: System aspects
1 Scope
This part of IEC 62689 describes electric phenomena and electric system behaviour during
faults, according to the most widely diffused distribution system architecture and to fault
typologies, to define the functional requirements for fault passage indicators (FPI) and
distribution substation units (DSU) (including their current and/or voltage sensors), which are,
respectively, a device or a device/combination of devices and/or of functions able to detect
faults and provide indications about their localization.
By localization of the fault is meant the fault position with respect to the FPI/DSU installation
point on the network (upstream or downstream from the FPI/DSU’s location) or the direction of
the fault current flowing through the FPI itself. The fault localization may be obtained
• directly from the FPI/DSU, or
• from a central system using information from more FPIs or DSUs,
considering the features and the operating conditions of the electric system where the
FPIs/DSUs are installed.
This part of IEC 62689 is therefore aimed at helping users in the appropriate choice of
FPIs/DSUs (or of a system based on FPI/DSU information) properly operating in their
networks, considering adopted solutions and operation rules (defined by tradition and/or
depending on possible constraints concerning continuity and quality of voltage supply defined
by a national regulator), and also taking into account complexity of the apparatus and
consequent cost.
This part of IEC 62689 is mainly focused on system behaviour during faults, which is the
“core” of FPI/DSU fault detection capability classes described in IEC 62689-1, where all
requirements are specified in detail.
2 Normative references
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.
IEC 62689-1, Current and voltage sensors or detectors, to be used for fault passage
indication purposes – Part 1: General principles and requirements
3 Terms, definitions, abbreviations and symbols
For the purposes of this document, the terms and definitions given in IEC 62689-1 and the
following apply.
– 10 – IEC 62689-2:2016 © IEC 2016
3.1 Terms and definitions related to neutral point treatment
3.1.1
arc-suppression coil
single-phase neutral earthing reactor intended for compensating the capacitive line-to-earth
current due to a single-phase earth fault
Note 1 to entry: Instead of a pure reactor, with high quality factor Q, a resistive-reactive impedance may be used
to render easier the earth fault detection and/or clearance.
Note 2 to entry: An arc-suppression coil is also known as a Petersen coil in certain areas.
[SOURCE: IEC 60050-421:1990, 421-01-04, modified – Note 1 and Note 2 to entry have been
added.]
3.2 Abbreviations and symbols
For the purposes of this document, the abbreviations and symbols given in IEC 62689-1
apply.
4 Choice of FPI/DSU requirements related to fault detection according to
network operation mode and fault type
4.1 General
Clause 4 is mainly focused on radially operated distribution networks, because this is,
generally, the most widely adopted mode of operation.
Fault (or fault current passage) detection on such networks strongly relies on MV neutral point
mode of operation.
In case of closed loop distribution networks, different considerations are necessary.
Directional fault detection, both concerning earth faults and overcurrents, based on vector
relationships among voltages and currents, is influenced by the impedance of the feeder and
have to be evaluated case by case. Communication among FPIs may be required.
A simpler solution may consist in opening the closed loop returning to radial operation and/or
to adopt communication among FPIs.
An example of a possible solution is shown in Annex A.
4.2 FPIs/DSUs for isolated neutral system
4.2.1 Earth fault detection
The earth fault current is influenced both by the network configuration and typology and by
the fault resistance.
The capacitive earth fault current contribution of medium voltage feeders' healthy sections is
generally an appreciable percentage of total earth fault current.
NOTE The contribution to earth fault current of an underground medium voltage cable is about 50 times that of an
overhead feeder of the same length.
Hence, in case of a fault upstream from the location of a FPI/DSU not equipped with
directional detection of fault current passage, to avoid incorrect indications regarding the fault
location, the current threshold set on FPI/DSU should be higher than the maximum earth fault
current contribution from the healthy feeder section downstream from the FPI/DSU itself.
IEC 62689-2:2016 © IEC 2016 – 11 –
Low sensitivity with regards to fault resistance could, therefore, be obtained in case of
non-directional FPIs/DSUs.
One method to discriminate the fault current with relatively high sensitivity with regards to
fault resistance could be the adoption of FPIs/DSUs based on directional earth fault detection.
If the contribution to capacitive earth fault current from the network downstream from the
FPI’s/DSU’s location is negligible, non-directional earth fault detection may be considered
without any significant decrease of FPI/DSU performance.
Possible presence of DER has no effect on the direction of fault current.
4.2.2 Polyphase fault detection
For the purpose of this document, the term polyphase is used to include the following faults:
• three phase
• phase to phase
• cross country
as they all involve mainly overcurrent.
If no DER (or not appreciable amount of DER) is present, in case of polyphase faults, the fault
current is coming from the HV/MV transformer. Directional FPIs/DSUs should, generally, be
required if DER contribution to polyphase fault current is appreciably present or in case of
closed-loop configuration.
4.3 FPIs/DSUs for resonant earthed (neutral) system – arc-suppression-coil-earth
(neutral) system
4.3.1 Earth fault detection
4.3.1.1 General
The fault current is influenced by the network configuration, the coil design (pure inductive or
inductive-resistance or inductive with short-term resistance, etc.), the connection to MV
neutral point, the tuning of the resonant coil, the network losses at zero sequence and the
fault resistance.
Two main solutions are possible: a “pure” arc-suppression coil, a fixed or tunable inductor
with negligible resistive component due only to internal losses or an inductance with an
intentional resistor to increase the amount of resistive current due to the coil.
4.3.1.2 “Pure” arc-suppression coil
In case of “pure” arc-suppression coil, tuned nearly to 100% of network capacitve current and
standard losses value in the network components, the earth fault current is extremely low,
mainly resistive, as the capacitive earth fault current contribution from the MV network is
compensated by the inductive contribution from the arc suppression coil. The magnitude of
the earth fault current would have near zero value when an earth fault occurs at any location
on the same HV/MV substation busbar network.
Moreover, earth fault current through all FPIs/DSUs, whatever their location on the network
(upstream or downstream from the fault position), is mainly reactive (vector relationship
between residual current in any FPI/DSU and residual voltage is the same, corresponding to
90° degree leading angle of residual current with respect to residual voltage), with negligible
active component (this component is the only one able to modify vector relationships between
residual current and residual voltage on faulty feeders with respect to healthy ones).
– 12 – IEC 62689-2:2016 © IEC 2016
FPIs/DSUs for pure resonant earthed (neutral) systems should, therefore, be directional for
phase to earth fault detection.
NOTE Without the adoption of a resistive-inductive arc-suppression coil (4.3.1.3), it may be possible to detect an
earth fault with non-directional FPI/DSU and with temporary modification of the network configuration, by, for
instance, creating a mistuning of the arc-suppression coil using a capacitor in parallel to the coil itself and
switching it on and off with different modalities.
4.3.1.3 Resistive-inductive arc-suppression coil
If a high-value resistor is installed in parallel to the arc suppression coil, temporarily or
permanently connected to earth:
• earth fault current through FPI/DSU installed on healthy feeders or downstream from the
fault is mainly reactive (the vector relationship between residual current and residual
voltage nearly corresponds to 90° leading angle of residual current with respect to residual
voltage), with negligible active component;
• earth fault current through FPI/DSU installed on faulty feeders upstream from the fault is
resistive-reactive (the vector relationship between residual current and residual voltage is
usually in the range from 90° to 180° leading angle of residual current with respect to
residual voltage), with non-negligible active component.
The magnitude of the earth fault current would have a value nearly corresponding to the
active current from the earthing resistor when an earth fault occurs at any location on the
same substation busbar network.
FPIs/DSUs for resistive-inductive resonant earthed (neutral) systems should, therefore, have
either directional or non-directional capability for phase to earth fault detection.
Possible presence of DER has no effect on the direction of fault current.
NOTE Detection of intermittent earth faults by FPI/DSU might be required.
4.3.2 Polyphase fault detection
See 4.2.2.
4.4 FPIs/DSUs for solidly earthed neutral systems (systems with low-impedance
earthed neutrals)
Overcurrent detection can be used to detect both earth and polyphase faults.
If no DER (or no appreciable amount of DER) is present, the fault current comes from the
HV/MV transformer. Phase directional FPIs/DSUs may be required only if DER is appreciably
present.
Moreover, earth directional FPIs/DSUs may be required even if, according to the DER neutral
point and the DER transformer group, a phase to earth current contribution may have come
from the DER.
4.5 FPIs/DSUs for impedance earthed neutral system (resistive impedance earthed
neutral system )
4.5.1 Earth fault detection
If the MV system neutral point is earthed by a resistor installed in the HV/MV substation, the
fault current is assumed to come from the HV/MV transformer.
IEC 62689-2:2016 © IEC 2016 – 13 –
FPIs/DSUs could be directional and/or non-directional, depending on the values of the
intentional earthing resistor (the lower it is, the higher is the neutral current, thus directional
detection could be avoided in some circumstances), on the network configuration, on the
network capacitive current and on the desired sensitivity concerning fault resistance value
detection.
In the case of an earthing resistor injecting low or moderate neutral currents in the event of an
earth fault, FPIs/DSUs should preferably be directional for earth fault detection. This is to
obtain appropriate sensitivity with regards to faults with high resistance value. The resulting
earth fault current obtained with this solution is not much higher than the pure capacitive earth
fault current component.
In the case of an earthing resistor injecting moderate or high neutral current in the event of an
earth fault, non-directional FPIs/DSUs may be used. With this solution, the earth fault current
is higher than the network capacitive current.
4.5.2 Polyphase fault detection
See 4.2.2.
4.6 FPIs/DSUs for systems with high presence of DER
The presence of DER on a network is considered to be high when the current contribution
from DER downstream from the FPI’s/DSU’s location for a fault located upstream from the
FPI/DSU itself (even on another MV feeder connected to the same HV/MV or MV/MV
transformer) is comparable to the FPI/DSU overcurrent thresholds.
In this case, FPIs/DSUs shall have directional detection of phase faults if the DER
significantly contributes to short-circuit currents (see 5.2.4 and 5.2.5). Concerning phase to
earth fault detection, see 4.2.1, 4.3.1, 4.4, 4.5.1. In any case, if directional detection is
present for polyphase overcurrents, the same should be true for phase to earth currents.
NOTE This version of FPI/DSU can also be able to:
• manage many smart grid network configurations, assuming that smart grids are distribution networks with a
high penetration of DERs;
• offer additional features (for instance, advanced network automation, including self healing and automatic
supply restore) even in the presence of DER;
• support easy network reconfiguration, DER active power and reactive power control for voltage regulation, etc.
Even additional distribution network operation structures, different from the main diffused radial ones, may be
successfully handled by these FPIs/DSUs (for instance closed loop operation of MV feeders).
4.7 Summary of FPI/DSU requirements with respect to fault detection according to
network operation mode and fault type
Table 1 gives a summary of FPI/DSU requirements described in 4.1 to 4.6.
Table 1 refers only to whether it is possible or not to adopt the directional fault detection
principle on FPIs, i.e. the detection of the fault current through the FPI itself.
The direction may be obtained with different solutions: by measuring the angle between
residual/phase voltage and residual/phase current, by transient analysis of current (and/or
voltage) of the first millisecond after fault occurrence, etc.
The complete FPI (and DSU) classification by classes is included in IEC 62689-1.
The content of Clause 4 is technically justified in Clause 5.
– 14 – IEC 62689-2:2016 © IEC 2016
Table 1 – Summary of FPI/DSU requirements referred to fault detection
according to network operation mode and fault type
Fault type MV network neutral point operation mode
Earth fault FPIs/DSUs for FPIs/DSUs for FPIs/DSUs for FPIs/DSUs for FPIs/DSUs for
isolated neutral resonant earthed resonant earthed solidly earthed impedance earthed
systems neutral system
system (neutral) system – (neutral) system –
arc-suppression- arc-suppression-coil- (systems with (resistive
coil-earth earth (neutral) low-impedance impedance earthed
(neutral) system system earthed neutral system)
neutrals)
Pure inductive Pure resistive-
arc-suppression- inductive arc-
coil suppression-coil
Earth fault Earth fault current Earth fault current Earth fault Earth fault current
current = MV negligible in nearly equal to current similar higher than
network comparison to active current from in amplitude to network capacitive
capacitive network intentional polyphase fault current
current capacitive current resistance (usually current
(if perfect tuning) much lower than
network capacitive
current, if perfect
tuning)
Fault current in Fault current in Fault current in Fault current in Fault current in
FPIs/DSUs: FPIs/DSUs: FPIs/DSUs: FPIs/DSUs: FPIs/DSUs:
value depending value depending value depending on value and value depending
on capacitive on capacitive capacitive current vector phase on capacitive
from network shift of residual current from
current from current from
network network downstream from the current with network
downstream from downstream from FPI/DSU location respect to downstream from
the FPI/DSU the FPI/DSU residual voltage the FPI/DSU
vector phase shift of
location location depending on location and from
residual current with
the ratio R/X of resistive current
vector phase shift respect to residual
v
...
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