SIST EN 62751-1:2014
(Main)Determination of power losses in voltage sourced converter (VSC) valves for high-voltage direct current (HVDC) systems - Part 1: General requirements
Determination of power losses in voltage sourced converter (VSC) valves for high-voltage direct current (HVDC) systems - Part 1: General requirements
This part of IEC 62751 sets out the general principles for calculating the power losses in the
converter valves of a voltage sourced converter (VSC) for high-voltage direct current (HVDC)
applications, independent of the converter topology. Clauses 6 and 8 and subclauses 9.1, 9.2
and A.2.12 of the standard can also be used for calculating the power losses in the dynamic
braking valves (where used) and as guidance for calculating the power losses of the valves
for a STATCOM installation.
Power losses in other items of equipment in the HVDC substation, apart from the converter
valves, are excluded from the scope of this standard. Power losses in most equipment in a
VSC substation can be calculated using similar procedures to those prescribed for HVDC
systems with line-commutated converters (LCC) in IEC 61803. Annex A presents the main
differences between LCC and VSC HVDC substations in so far as they influence the method
for determining power losses of other equipment.
This standard does not apply to converter valves for line-commutated converter HVDC
systems.
Bestimmung der Leistungsverluste in Spannungszwischenkreis-Stromrichtern (VSC) für Hochspannungsgleichstrom(HGÜ)-Systeme -- Teil 1: Allgemeine Anforderungen
Détermination des pertes de puissance dans les valves à convertisseur de source de tension (VSC) des systèmes de transport d’énergie en courant continu à haute tension (CCHT) -- Partie 1: Exigences générales
L'IEC 62751-1:2014 définit les principes généraux de calcul des pertes de puissance dans les valves à convertisseur de source de tension (VSC) pour des applications en courant continu à haute tension (CCHT), quelle que soit la topologie du convertisseur. Plusieurs articles de la norme peuvent également être utilisés pour calculer les pertes de puissance dans les valves à freinage dynamique (le cas échéant) et comme guide pour le calcul des pertes de puissance des valves d'une installation STATCOM.
Ugotavljanje izgub moči v napetostnih pretvorniških ventilih za visokonapetostne enosmerne sisteme - 1. del: Splošne zahteve (IEC 62751-1:2014)
Ta del standarda IEC 62751 določa splošne zahteve za izračun izgube moči v napetostnih pretvorniških ventilih (VSC) za uporabo v visokonapetostnih enosmernih sistemih (HVDC), neodvisno od topologije pretvornika. Točki 6 in 8 ter točke 9.1, 9.2 in A2.12 standarda se lahko prav tako uporabijo za izračun izgube moči v dinamičnih zavornih ventilih (kjer so uporabljeni) in kot smernice za izračun izgube moči v ventilih za namestitev STATCOM. Izgube moči v drugih elementih opreme v napravi HVDC, razen pretvorniških ventilov, so izključene iz področja uporabe tega standarda. Izgube moči v večini opreme v napravi VSC je mogoče izračunati s podobnimi postopki, ki so predpisani za sisteme HVDC s pretvorniki z linijsko komutacijo (LCC) v standardu IEC 61803. Dodatek A predstavlja glavne razlike med pretvorniki LCC in napravami VSC, HVDC, predvsem njihov vpliv na metodo določanja izgube moči druge opreme.
Ta standard se ne uporablja za pretvorniške ventile za sisteme HVDC s pretvorniki z linijsko komutacijo.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 62751-1:2014
01-december-2014
8JRWDYOMDQMHL]JXEPRþLYQDSHWRVWQLKSUHWYRUQLãNLKYHQWLOLK]DYLVRNRQDSHWRVWQH
HQRVPHUQHVLVWHPHGHO 6SORãQH]DKWHYH ,(&
Determination of power losses in voltage sourced converter (VSC) valves for high-
voltage direct current (HVDC) systems - Part 1: General requirements
Bestimmung der Leistungsverluste in Spannungszwischenkreis-Stromrichtern (VSC) für
Hochspannungsgleichstrom(HGÜ)-Systeme -- Teil 1: Allgemeine Anforderungen
Détermination des pertes de puissance dans les valves à convertisseur de source de
tension (VSC) des systèmes de transport d’énergie en courant continu à haute tension
(CCHT) -- Partie 1: Exigences générales
Ta slovenski standard je istoveten z: EN 62751-1:2014
ICS:
29.200 8VPHUQLNL3UHWYRUQLNL Rectifiers. Convertors.
6WDELOL]LUDQRHOHNWULþQR Stabilized power supply
QDSDMDQMH
29.240.01 2PUHåMD]DSUHQRVLQ Power transmission and
GLVWULEXFLMRHOHNWULþQHHQHUJLMH distribution networks in
QDVSORãQR general
SIST EN 62751-1:2014 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 62751-1:2014
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SIST EN 62751-1:2014
EUROPEAN STANDARD EN 62751-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2014
ICS 29.200; 29.240
English Version
Power losses in voltage sourced converter (VSC) valves for
high-voltage direct current (HVDC) systems - Part 1: General
requirements
(IEC 62751-1:2014)
Pertes de puissance dans les valves à convertisseur de Bestimmung der Leistungsverluste in
source de tension (VSC) des systèmes en courant continu Spannungszwischenkreis-Stromrichtern (VSC) für
à haute tension (CCHT) - Partie 1: Exigences générales Hochspannungsgleichstrom(HGÜ)-Systeme - Teil 1:
(CEI 62751-1:2014) Allgemeine Anforderungen
(IEC 62751-1:2014)
This European Standard was approved by CENELEC on 2014-10-01. 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 62751-1:2014 E
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SIST EN 62751-1:2014
EN 62751-1:2014 - 2 -
Foreword
The text of document 22F/302/CDV, future edition 1 of IEC 62751-1, prepared by SC 22F "Power
electronics for electrical transmission and distribution systems", of IEC/TC 22 "Power electronic
systems and equipment" was submitted to the IEC-CENELEC parallel vote and approved by
CENELEC as EN 62751-1:2014.
The following dates are fixed:
– latest date by which the document has to be implemented at (dop) 2015-07-01
national level by publication of an identical national
standard or by endorsement
– latest date by which the national standards conflicting with (dow) 2017-10-01
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 62751-1:2014 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard indicated:
IEC 61803:1999 NOTE Harmonised as EN 61803:1999.
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SIST EN 62751-1:2014
- 3 - EN 62751-1:2014
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 60633 - Terminology for high-voltage direct current EN 60633 -
(HVDC) transmission
IEC 60747-2 - Semiconductor devices - Discrete devices - -
and integrated circuits -- Part 2: Rectifier
diodes
IEC 60747-9 2007 Semiconductor devices - Discrete devices - - -
Part 9: Insulated-gate bipolar transistors
(IGBTs)
IEC 62747 2014 Terminology for voltage-sourced EN 62747 2014
converters (VSC) for high-voltage direct
current (HVDC) systems
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SIST EN 62751-1:2014
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SIST EN 62751-1:2014
IEC 62751-1
®
Edition 1.0 2014-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Power losses in voltage sourced converter (VSC) valves for high-voltage direct
current (HVDC) systems –
Part 1: General requirements
Pertes de puissance dans les valves à convertisseur de source de tension (VSC)
des systèmes en courant continu à haute tension (CCHT) –
Partie 1: Exigences générales
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX V
ICS 29.200; 29.240 ISBN 978-2-8322-1835-8
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 62751-1:2014
– 2 – IEC 62751-1:2014 © IEC 2014
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
3.1 Converter types . 7
3.2 Semiconductor devices . 7
3.3 Converter operating states . 8
3.4 Device characteristics . 9
3.5 Other definitions . 9
4 General conditions. 10
4.1 General . 10
4.2 Causes of power losses . 11
4.3 Categories of valve losses . 11
4.4 Operating conditions . 12
4.4.1 General . 12
4.4.2 Reference ambient conditions . 12
4.4.3 Reference a.c. system conditions . 12
4.4.4 Converter operating states. 12
4.4.5 Treatment of redundancy . 12
4.5 Use of real measured data . 13
4.5.1 General . 13
4.5.2 Routine testing . 13
4.5.3 Characterisation testing . 13
5 Conduction losses . 14
5.1 General . 14
5.2 IGBT conduction losses . 16
5.3 Diode conduction losses . 16
5.4 Other conduction losses . 17
6 D.C. voltage-dependent losses . 17
7 Losses in d.c. capacitors . 18
8 Switching losses . 18
8.1 General . 18
8.2 IGBT switching losses . 19
8.3 Diode switching losses . 20
9 Other losses . 21
9.1 Snubber circuit losses . 21
9.2 Valve electronics power consumption. 21
10 Total valve losses per converter substation . 22
Annex A (informative) Determination of power losses in other HVDC substation
equipment . 25
A.1 General . 25
A.2 Guidance for calculating losses in each equipment . 25
A.2.1 Circuit breaker . 25
A.2.2 Pre-insertion resistor . 25
A.2.3 Line side harmonic filter . 26
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SIST EN 62751-1:2014
IEC 62751-1:2014 © IEC 2014 – 3 –
A.2.4 Line side high frequency filter . 26
A.2.5 Interface transformer . 26
A.2.6 Converter side harmonic filter . 27
A.2.7 Converter side high frequency filter . 27
A.2.8 Phase reactor . 27
A.2.9 VSC unit . 27
A.2.10 VSC d.c. capacitor . 27
A.2.11 D.C. harmonic filter . 27
A.2.12 Dynamic braking system . 27
A.2.13 Neutral point grounding branch . 28
A.2.14 D.C. reactor . 28
A.2.15 Common mode blocking reactor . 28
A.2.16 D.C. side high frequency filter . 28
A.2.17 D.C. cable or overhead transmission line . 28
A.3 Auxiliaries and station service losses . 29
Bibliography . 30
Figure 1 – On-state voltage of an IGBT or diode . 14
Figure 2 – Piecewise-linear representation of IGBT or diode on-state voltage . 15
Figure 3 – IGBT switching energy as a function of collector current . 19
Figure 4 – Diode recovery energy as a function of current . 20
Figure A.1 – Major components that may be found in a VSC substation . 26
Table 1 – Matrix indicating the relationship of data needed for calculation of losses
and the type of valve losses (1 of 2) . 23
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SIST EN 62751-1:2014
– 4 – IEC 62751-1:2014 © IEC 2014
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
POWER LOSSES IN VOLTAGE SOURCED CONVERTER (VSC)
VALVES FOR HIGH-VOLTAGE DIRECT CURRENT (HVDC) SYSTEMS –
Part 1: General requirements
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,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
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-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
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
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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 62751-1 has been prepared by subcommittee 22F: Power
electronics for electrical transmission and distribution systems, of IEC technical committee 22:
Power electronic systems and equipment.
The text of this standard is based on the following documents:
CDV Report on voting
22F/302/CDV 22F/321A/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.
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SIST EN 62751-1:2014
IEC 62751-1:2014 © IEC 2014 – 5 –
A list of all parts in the IEC 62751series, published under the general title Power losses in
voltage sourced converter (VSC) valves for high-voltage direct current (HVDC) systems, 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.
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SIST EN 62751-1:2014
– 6 – IEC 62751-1:2014 © IEC 2014
POWER LOSSES IN VOLTAGE SOURCED CONVERTER (VSC)
VALVES FOR HIGH-VOLTAGE DIRECT CURRENT (HVDC) SYSTEMS –
Part 1: General requirements
1 Scope
This part of IEC 62751 sets out the general principles for calculating the power losses in the
converter valves of a voltage sourced converter (VSC) for high-voltage direct current (HVDC)
applications, independent of the converter topology. Clauses 6 and 8 and subclauses 9.1, 9.2
and A.2.12 of the standard can also be used for calculating the power losses in the dynamic
braking valves (where used) and as guidance for calculating the power losses of the valves
for a STATCOM installation.
Power losses in other items of equipment in the HVDC substation, apart from the converter
valves, are excluded from the scope of this standard. Power losses in most equipment in a
VSC substation can be calculated using similar procedures to those prescribed for HVDC
systems with line-commutated converters (LCC) in IEC 61803. Annex A presents the main
differences between LCC and VSC HVDC substations in so far as they influence the method
for determining power losses of other equipment.
This standard does not apply to converter valves for line-commutated converter HVDC
systems.
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 60633, Terminology for high-voltage direct current (HVDC) transmission
IEC 60747-2, Semiconductor devices – Discrete devices and integrated circuits – Part 2:
Rectifier diodes
IEC 60747-9:2007, Semiconductor devices – Discrete devices – Part 9: Insulated-gate bipolar
transistors (IGBTs)
IEC 62747:2014, Terminology for voltage-sourced converters (VSC) for high-voltage direct
current (HVDC) systems
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SIST EN 62751-1:2014
IEC 62751-1:2014 © IEC 2014 – 7 –
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60633, IEC 62747,
IEC 60747-2, IEC 60747-9 as well as the following apply.
NOTE 1 Related terms and definitions can also be found in IEC TR 62543, IEC 62751-2 and in the other relevant
parts of the IEC 60747 series.
NOTE 2 Throughout this standard, the term “insulated gate bipolar transistor (IGBT)” is used to indicate a turn-off
semiconductor device; however, the standard is equally applicable to other types of turn-off semiconductor devices
such as the GTO, IGCT, ETO, IEGT, etc.
3.1 Converter types
3.1.1
2-level converter
converter in which the voltage between the a.c. terminals of the VSC unit and VSC unit
midpoint is switched between two discrete d.c. voltage levels
Note 1 to entry: VSC unit midpoint is defined in 3.5.9.
3.1.2
multi-level converter
converter in which the voltage between the a.c. terminals of the VSC unit and VSC unit
midpoint is switched between more than three discrete d.c. voltage levels
Note 1 to entry: VSC unit midpoint is defined in 3.5.9.
3.1.3
modular multi-level converter
MMC
multi-level converter in which each VSC valve consists of a number of MMC building blocks
connected in series
Note 1 to entry: MMC building block is defined in 3.5.4.
Note 2 to entry: This note applies to the French language only.
3.1.4
cascaded two-level converter
CTL
modular multi-level converter in which each switch position consists of more than one IGBT-
diode pair connected in series
Note 1 to entry: IGBT-diode pair is defined in 3.2.4.
Note 2 to entry: This note applies to the French language only.
3.2 Semiconductor devices
3.2.1
turn-off semiconductor device
controllable semiconductor device which may be turned on and off by a control signal, for
example an IGBT
3.2.2
insulated gate bipolar transistor
IGBT
turn-off semiconductor device with three terminals: a gate terminal (G) and two load terminals
emitter (E) and collector (C)
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SIST EN 62751-1:2014
– 8 – IEC 62751-1:2014 © IEC 2014
Note 1 to entry: By applying appropriate gate to emitter voltages, current in one direction can be controlled, i.e.
turned on and turned off.
Note 2 to entry: This note applies to the French language only.
3.2.3
free-wheeling diode
FWD
power semiconductor device with diode characteristic
Note 1 to entry: A FWD has two terminals: an anode (A) and a cathode (K). The current through FWDs is in
opposite direction to the IGBT current. FWDs are characterized by the capability to cope with high rates of
decrease of current caused by the switching behaviour of the IGBT.
Note 2 to entry: This note applies to the French language only.
3.2.4
IGBT-diode pair
arrangement of IGBT and FWD connected in inverse parallel
Note 1 to entry: An IGBT-diode pair is usually in one common package; however, it can include individual IGBTs
and/or diodes packages connected in parallel.
3.3 Converter operating states
3.3.1
no-load operating state
condition in which the VSC substation is energized but the IGBTs are blocked and all
substation service loads and auxiliary equipment are connected
3.3.2
idling operating state
condition in which the VSC substation is energized and the IGBTs are de-blocked but with no
active or reactive power output at the point of common connection to the a.c. network
Note 1 to entry: The “idling operating” and “no-load” conditions are similar but from the no-load state several
seconds may be needed before power can be transmitted, while from the idling operating state, power transmission
may be commenced almost immediately (less than 3 power frequency cycles).
Note 2 to entry: In the idling operating state, the converter is capable of actively controlling the d.c. voltage, in
contrast to the no-load state where the behaviour of the converter is essentially “passive”.
Note 3 to entry: Losses will generally be slightly lower in the no-load state than in the idling operating state,
therefore this operating mode is preferred where the arrangement of the VSC system permits it.
3.3.3
operating state
condition in which the VSC substation is energized and the converters are de-blocked
Note 1 to entry: Unlike line-commutated converter, VSC can operate with zero active/reactive power output.
3.3.4
no-load power losses
power losses in the VSC valve in the no-load state
Note 1 to entry: In some converter designs, it may be necessary to make occasional switching operations for the
purposes of balancing voltages between different parts of the converter. In such converters, the calculation of no-
load losses shall take into account the switching frequency of such an operating mode.
3.3.5
idling operating losses
losses in the VSC valve in the idling operating state
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SIST EN 62751-1:2014
IEC 62751-1:2014 © IEC 2014 – 9 –
3.3.6
operating losses
losses in the VSC valve in the operating state
3.4 Device characteristics
3.4.1
IGBT collector-emitter saturation voltage
V
CE(sat)
collector-emitter voltage under conditions of gate-emitter voltage at which the collector current
is essentially independent of the gate-emitter voltage
3.4.2
IGBT turn-on energy
E
on
energy dissipated inside the IGBT during the turn-on of a single collector current pulse
3.4.3
IGBT turn-off energy
E
off
energy dissipated inside the IGBT during the turn-off procedure of a single collector current
pulse
3.4.4
diode forward voltage
V
F
voltage across the terminals of a diode which results from the flow of current in the forward
direction
3.4.5
diode reverse recovery energy
E
rec
energy dissipated inside the diode during the turn-off procedure
3.5 Other definitions
3.5.1
VSC valve level
smallest indivisible functional unit of VSC valve
Note 1 to entry: For any VSC valve in which IGBTs are connected in series and operated simultaneously, one
VSC valve level is one IGBT-diode pair including its auxiliaries. For MMC type valve, one valve level is one
submodule together with its auxiliaries.
3.5.2
redundant levels
maximum number of series connected VSC valve levels or diode valve levels in a valve that
may be short-circuited externally or internally during service without affecting the safe
operation of the valve as demonstrated by type tests, and which if and when exceeded, would
require shutdown of the valve to replace the failed levels or acceptance of increased risk of
failures
Note 1 to entry: In valve designs such as the cascaded two level converter, which contain two or more conduction
paths within each cell and have series-connected VSC valve levels in each path, redundant levels shall be counted
only in one conduction path in each cell
3.5.3
valve electronics
electronic circuits at valve potential(s) which perform control and protection functions for one
or more valve levels
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SIST E
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