SIST EN 62823:2016

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.LVWRUVNLPThyristor valves for thyristor controlled series capacitors (TCSC) - Electrical testing31.080.20TiristorjiThyristors17.220.20Measurement of electrical and magnetic quantitiesICS:Ta slovenski standard je istoveten z:EN 62823:2015SIST EN 62823:2016en01-marec-2016SIST EN 62823:2016SLOVENSKI
STANDARD
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 62823
November 2015 ICS 29.240.99
English Version
Thyristor valves for thyristor controlled series capacitors (TCSC) - Electrical testing (IEC 62823:2015)
Valves à thyristors pour condensateurs série commandés par thyristors (CSCT) - Essai électrique (IEC 62823:2015)
Thyristorventile für thyristorgesteuerte Reihenkondensatoren (TCSC) - Elektrische Prüfung (IEC 62823:2015) This European Standard was approved by CENELEC on 2015-09-24. 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 © 2015 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN 62823:2015 E SIST EN 62823:2016

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 62823:2015 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 60068-1 NOTE Harmonized as EN 60068-1. IEC 60143-1 NOTE Harmonized as EN 60143-1. IEC 60721-1 NOTE Harmonized as EN 60721-1. IEC 61000-6-5 NOTE Harmonized as EN 61000-6-5. IEC 61954 NOTE Harmonized as EN 61954. SIST EN 62823:2016

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 60060-1 2010
High-voltage test techniques - Part 1: General definitions and test requirements EN 60060-1 2010
IEC 60071-1 -
Insulation co-ordination - Part 1: Definitions, principles and rules EN 60071-1 -
IEC 60071-2 -
Insulation co-ordination - Part 2: Application guide EN 60071-2 -
IEC 60270 -
High-voltage test techniques - Partial discharge measurements EN 60270 -
IEC 62823 Edition 1.0 2015-08 INTERNATIONAL STANDARD NORME INTERNATIONALE Thyristor valves for thyristor controlled series capacitors (TCSC) – Electrical testing
Valves à thyristors pour condensateurs série commandés par thyristors (CSCT) – Essai électrique
INTERNATIONAL ELECTROTECHNICAL COMMISSION COMMISSION ELECTROTECHNIQUE INTERNATIONALE
ICS 29.240.99
ISBN 978-2-8322-2860-9
– 2 – IEC 62823:2015 © IEC 2015 CONTENTS FOREWORD . 5 1 Scope . 7 2 Normative references . 7 3 Terms and definitions . 7 4 TCSC valve and valve operation in general . 10 4.1 TCSC installation and TCSC valve . 10 4.2 TCSC valve current and voltage at capacitive boost operation . 12 4.2.1 General . 12 4.2.2 Waveshapes of valve current and voltage in capacitive boost operation . 12 4.2.3 Formulas for TCSC valve current and voltage stresses calculation . 13 4.3 Typical operating pattern of TCSC installation . 15 5 General requirements . 15 5.1 Guidelines for the performance of type tests . 15 5.1.1 Evidence in lieu . 15 5.1.2 Sequence of tests . 16 5.1.3 Ambient temperature for testing . 16 5.1.4 Frequency for testing . 16 5.1.5 Test reports . 16 5.2 Test conditions for dielectric tests . 16 5.2.1 General . 16 5.2.2 Treatment of redundancy in dielectric tests . 16 5.2.3 Atmospheric correction factor . 17 5.3 Test conditions for operational tests . 17 5.3.1 General . 17 5.3.2 Treatment of redundancy in operational tests . 17 5.4 Criteria for successful type testing . 18 5.4.1 General . 18 5.4.2 Criteria applicable to valve levels . 18 5.4.3 Criteria applicable to the valve as a whole . 19 6 Summary of tests . 19 7 Dielectric tests between valve terminals and valve enclosure . 20 7.1 Purpose of tests . 20 7.2 Test object . 21 7.3 Test requirements . 21 7.3.1 AC test . 21 7.3.2 Lightning impulse test . 22 8 Dielectric tests between valve terminals . 22 8.1 Purpose of tests . 22 8.2 Test object . 22 8.3 Test requirements . 23 8.3.1 AC test . 23 8.3.2 Switching impulse test . 24 9 Periodic firing and extinction tests . 24 9.1 Purpose of tests . 24 9.2 Test object . 24 SIST EN 62823:2016

IEC 62823:2015 © IEC 2015 – 3 – 9.3 Test requirements . 25 9.3.1 General . 25 9.3.2 Maximum continuous capacitive boost test . 25 9.3.3 Maximum temporary capacitive boost test . 26 9.3.4 Minimum capacitive boost test . 26 9.3.5 Operation at bypass. 27 10 Fault current tests . 29 10.1 Purpose of tests . 29 10.2 Test object . 29 10.3 Test requirements . 29 10.3.1 Fault current without subsequent blocking . 29 10.3.2 Fault current with subsequent blocking . 29 11 Test for valve insensitivity to electromagnetic disturbance . 30 11.1 Purpose of tests . 30 11.2 Test object . 30 11.3 Test requirements . 30 12 Testing of special features . 30 12.1 Purpose of tests . 30 12.2 Test object . 31 12.3 Test requirements . 31 13 Routine tests . 31 13.1 General . 31 13.2 Visual inspection . 31 13.3 Connection check . 31 13.4 Voltage grading circuit check . 31 13.5 Voltage withstand check . 31 13.6 Partial discharge tests . 31 13.7 Check of auxiliaries . 32 13.8 Firing check . 32 13.9 Cooling system pressure test . 32 14 Presentation of type test results . 32 Annex A (informative)
TCSC valve operating and rating considerations . 33 A.1 Overview. 33 A.2 TCSC characteristics . 33 A.3 Operating range . 34 A.4 Reactive power rating . 35 A.5 Power oscillation damping (POD) . 35 A.6 SSR mitigation . 35 A.7 Harmonics . 36 A.8 Control interactions between TCSCs in parallel lines . 36 A.9 Operating range, overvoltages and duty cycles . 36 A.9.1 Operating range . 36 A.9.2 Transient overvoltages . 36 A.9.3 Duty cycles . 37 Annex B (informative)
Valve component fault tolerance. 38 Bibliography . 39
– 4 – IEC 62823:2015 © IEC 2015 Figure 1 – Typical connection and nomenclature of a TCSC installation . 11 Figure 2 – TCSC subsegment . 11 Figure 3 – TCSC steady state waveforms for
control angle . and conduction interval 1 . 12 Figure 4 – Thyristor valve voltage in a TCSC . 13 Figure 5 – Example of operating range diagram for TCSC . 15 Figure A.1 – TCSC power frequency steady state apparent reactance
characteristics according to Formula (A.1) with
= 2,5 . 34
Table 1 – Valve level faults permitted during type tests . 19 Table 2 – List of tests . 20 Table A.1 – Peak and RMS voltage relationships . 33
IEC 62823:2015 © IEC 2015 – 5 – INTERNATIONAL ELECTROTECHNICAL COMMISSION ____________
THYRISTOR VALVES FOR THYRISTOR CONTROLLED
SERIES CAPACITORS (TCSC) – ELECTRICAL TESTING
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 62823 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/342/CDV 22F/354A/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. SIST EN 62823:2016

– 6 – IEC 62823:2015 © IEC 2015 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 62823:2015 © IEC 2015 – 7 – THYRISTOR VALVES FOR THYRISTOR CONTROLLED
SERIES CAPACITORS (TCSC) – ELECTRICAL TESTING
1 Scope This International Standard defines routine and type tests on thyristor valves used in thyristor controlled series capacitor (TCSC) installations for AC power transmission.
The tests specified in this International Standard are based on air insulated valves operating in capacitive boost mode or bypass mode. For other types of valve and for a valve operating in inductive boost mode, the test requirements and acceptance criteria are agreed between purchaser and supplier. 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 60060-1:2010, High-voltage test techniques – Part 1: General definitions and test requirements IEC 60071-1, Insulation co-ordination – Part 1: Definitions, principles and rules IEC 60071-2, Insulation co-ordination – Part 2: Application guide IEC 60270, High-voltage test techniques – Partial discharge measurements 3 Terms and definitions
For the purposes of this document, the following terms and definitions apply. 3.1
thyristor valve
electrically and mechanically combined assembly of thyristor levels, complete with all connections, auxiliary components and mechanical structures, which can be connected in series with each phase of the reactor of a TCSC 3.2
valve section electrical assembly, comprising a number of thyristors and other components, which exhibits prorated electrical properties of a complete valve Note 1 to entry: This term is mainly used to define a test object for valve testing purposes. 3.3
thyristor level part of a valve comprising an anti-parallel connected pair of thyristors together with their immediate auxiliaries, and reactor, if any SIST EN 62823:2016

– 8 – IEC 62823:2015 © IEC 2015 3.4
redundant thyristor levels, pl
maximum number of thyristor levels in the thyristor valve that may be short-circuited, externally or internally, during service without affecting the safe operation of the thyristor valve as demonstrated by type tests and which, if and when exceeded, would require either the shutdown of the thyristor valve to replace the failed thyristors or the acceptance of increased risk of failures 3.5
valve arrester
arrester connected across a valve
3.6
valve electronics
VE electronic circuits at valve potential(s) that perform control functions Note 1 to entry: This note applies to the French language only. 3.7
valve interface electronics unit electronic unit which provides an interface between the control equipment, at earth potential, and the valve electronics or valve devices Note 1 to entry: Valve interface electronics units, if used, are typically located at earth potential close to the valve(s). Note 2 to entry: The term “valve base electronics” (VBE) is also used to designate this unit. 3.8
thyristor-controlled series capacitor bank
TCSC bank assembly of thyristor valves, reactor(s), capacitors, and associated auxiliaries, such as structures, support insulators, switches, and protective devices, with control equipment required for a complete operating installation 3.9
TCSC reactor one or more reactors connected in series with the thyristor valve
SEE: Figure 1, item 4. 3.10
valve enclosure platform-mounted enclosure containing thyristor valve(s) with associated valve cooling and electronic hardware 3.11
temporary overload
short-term overload capability of the TCSC at rated frequency and ambient temperature range SEE: Figure 5. Note 1 to entry: Temporary overload is typically of several seconds duration, less than 10 s. 3.12
valve protective firing means of protecting the thyristors from excessive voltage by firing them at a predetermined voltage
IEC 62823:2015 © IEC 2015 – 9 – 3.13
line current
iL power frequency line current SEE: Figure 2. 3.14
rated current IN
RMS line current (IL) at which the TCSC should be capable of continuous operation with rated reactance (XN) and rated voltage (UN) 3.15
valve current iV current through the thyristor valve
SEE: Figure 2. 3.16
bypass current
current flowing through the thyristor valve in parallel with the series capacitor, when the series capacitor is bypassed 3.17
capacitor voltage UC voltage across the TCSC SEE: Figure 2. 3.18
nominal reactance XN
nominal power frequency reactance for each phase of the TCSC with nominal boost factor 3.19
rated TCSC voltage UN
power frequency voltage across each phase of the TCSC that can be continuously controlled at nominal reactance (XN), rated current (IN), nominal power frequency, and ambient temperature range 3.20
apparent reactance X(.)
TCSC apparent power frequency reactance as a function of thyristor control angle (.)
SEE: Figure 3, Figure A.1 and Formula A.1. 3.21
rated capacitance CN capacitance value for which the TCSC capacitor has been designed
– 10 – IEC 62823:2015 © IEC 2015 3.22
physical reactance XC
power frequency reactance for each phase of the TCSC bank with thyristors blocked and a capacitor internal dielectric temperature of 20 °C
()NNC1CX⋅=ω 3.23
boost factor kB
the ratio of apparent reactance X(.) divided by physical reactance XC kB = X(.) / XC 3.24
conduction interval 1
part of a half of a power frequency cycle during which a thyristor valve is in the conducting state
1 = 2 SEE: Figure 3. 3.25
control angle . time expressed in electrical angular measure from the capacitor voltage (UC) zero crossing to the starting of current conduction through the thyristor valve
SEE: Figure 3. 3.26
internal fault line fault occurring within the protected line section containing the series TCSC subsegment 3.27
external fault line fault occurring outside the protected line section containing the series TCSC subsegment 4 TCSC valve and valve operation in general
4.1 TCSC installation and TCSC valve Transmission line series reactance can be compensated by combinations of fixed series capacitors (FSC) and TCSC based controllable segments, as shown in Figure 1. A TCSC subsegment uses a thyristor-controlled reactor (TCR) in parallel with a capacitor bank with the rated capacitance CN, as shown in Figure 2. The thyristor valve used in this TCSC subsegment is a TCSC valve (See Figure 1, item 5). SIST EN 62823:2016

IEC 62823:2015 © IEC 2015 – 11 –
Key
1 TCSC unit 8 Discharge current limiter, if applicable
2 Additional TCSC unit when required 9 Bypass switch
3 TCSC capacitor
10 Bypass gap
4 TCSC reactor 11 External bypass disconnector 5 TCSC thyristor valve 12 External isolating switch 6 TCSC subsegment 13 External earth switch 7 Capacitor arrester 14 Additional FSC unit when required Figure 1 – Typical connection and nomenclature of a TCSC installation
Figure 2 – TCSC subsegment IEC TCSC reactor (L)Thyristor valveArresterCapacitor (C)iLiViCUCIEC 10941211531368712PhasePhase141213SIST EN 62823:2016

– 12 – IEC 62823:2015 © IEC 2015 4.2 TCSC valve current and voltage at capacitive boost operation 4.2.1 General Even if a TCSC valve can be, theoretically, operated in an inductive boost mode, this operation is not used in practice in a TCSC installation due to the system compensation need and other limitations. Capacitive boost operation mode is a used operation mode of a TCSC valve.
4.2.2 Waveshapes of valve current and voltage in capacitive boost operation At a sinusoidal line current and voltage (see Figure 3 a)), the capacitive boost operating of a TCSC valve leads to a deformed sinusoidal current flow through the capacitor bank, C, and TCSC valve (see Figure 3 b)). This current boosts the fundamental frequency voltage drop across the TCSC subsegment.
The waveform of the thyristor valve voltage in a TCSC is shown in Figure 4.
a) Capacitor bank voltage UC and current iL at a = 180° b) Capacitor bank voltage UC and current iC at a = 145° Figure 3 – TCSC steady state waveforms for
control angle . and conduction interval 1
IEC UC at . = 145º.Boosting factor ≈ 2,0Electric angle (º)2,01,51,00,50,0-0,5-1,0-1,5-2,0090180270360Normalized units (peak)1iC = iL + iViLiVIEC iLUC at . = 180º.Boosting factor = 1,0Electric angle (º)2,01,51,00,50,0-0,5-1,0-1,5-2,0090180270360Normalized units (peak)SIST EN 62823:2016

IEC 62823:2015 © IEC 2015 – 13 –
Figure 4 – Thyristor valve voltage in a TCSC 4.2.3 Formulas for TCSC valve current and voltage stresses calculation
4.2.3.1 Capacitive boost operation mode
In TCSC capacitive boost operation mode, the TCSC valve current follows the formulation below: ()⋅⋅⋅⋅−⋅⋅−⋅⋅−=ttiinNN2L2vcoscoscoscos11ωλβλβωλλ,
n⋅π −
≤ ωN⋅t ≤ n⋅π +
0v=i n⋅π += < ωN⋅t < (n + 1)⋅π −
n = 0, 1, 2, 3, … where λ is the ratio of TCSC subsegment LC branch natural frequency and AC system power frequency,CL⋅⋅=N1ωλ; iL is the AC system line current; ωN nominal angle frequency of AC system; β is half of the maximum conduction angle of TCSC valves in one direction for capacitive boost at iL. IEC 60 55 50 45 40 35 30 25 20 0,25 0 0,5 0,75 1 –1 –0,5
0,5
1 Valve voltage 60 120 180 240 300 360 SIST EN 62823:2016

– 14 – IEC 62823:2015 © IEC 2015 The rate of current change, di/dt, at thyristor turn-on and turn-off derives as follows: ()()⋅⋅⋅⋅−⋅⋅−⋅=+=⋅βλβλβωβωλλβπωsincoscossin1ddNN2L22vNitit The peak current through the TCSC valve is equal to:
()⋅−⋅−⋅=βλβλλcoscos112L2v_peakii The capacitor voltage, UC_N, at thyristor turn-on and turn-off instants is equal to:
[])tan(cossin102LC_Nβλβλβλλ⋅⋅⋅−⋅⋅−⋅=XiU where X0 is the TCSC subsegment LC branch impedance:
CLX=0, where L is the inductance of TCSC subsegment LC branch (Figure 2); C is the capacitance of TCSC subsegment LC branch (Figure 2). The capacitor voltage peak, appearing on the TCSC valve, is equal to:
−⋅−⋅⋅⋅+⋅⋅⋅=1)sin)tan((cos120LPλβλβλβλλXiU The capacitive boost factor of the TCSC subsegment is equal to:
()[]()⋅−−−⋅⋅⋅−⋅⋅−⋅+=βββββλλλβλλπ2sintantan1cos21212222Bk 4.2.3.2 Bypass operation mode
In TCSC bypass operation mode the TCSC valve is full conduction and the valve conducts a power frequency sinusoidal waveform bypass current equal to: L2Nbypass11iCLi⋅⋅⋅−=ω The capacitor voltage at bypass operation follows the formula below:
()CiU⋅⋅−−=N2LC1ωλ SIST EN 62823:2016

IEC 62823:2015 © IEC 2015 – 15 – 4.3 Typical operating pattern of TCSC installation See Figure 5.
Continuous capacitive boost operation area
Temporary capacitive boost operation area
Continuous bypass operation
Temporary bypass operation Figure 5 – Example of operating range diagram for TCSC 5 General requirements
5.1 Guidelines for the performance of type tests 5.1.1 Evidence in lieu 5.1.1.1 General Each design of valve shall be subjected to the type tests specified in this International Standard. If the valve is demonstrably similar to the one previously tested, the supplier may, in lieu of performing a type test, submit a test report of a previous type test for consideration by the purchaser. IEC 00,20,40,60,81,01,21,41,61,82,0A1A2A3B1B2B3C1Line current (p.u.)Boosting factor (p.u.)0,50,0-0,5-1,0-1,5-2,0-2,5-3,0-3,5C3C2SIST EN 62823:2016

– 16 – IEC 62823:2015 © IEC 2015 5.1.1.2 Test object The tests described apply to the valve (or valve sections), the valve structure and those parts of the coolant distribution system and firing and monitoring circuits which are contained within the valve structure or connected between the valve structure and platform. Other equipment, such as valve control and protection and valve interface electronics units may be essential for demonstrating the correct function of the valve during the tests but are not in themselves the subject of the valve tests. Certain type tests may be performed either on a complete valve or on valve sections, as indicated in Table 2. For those type tests on valve sections, the total number of valve sections tested shall be at least as many as the number in a complete valve. The same valve sections shall be used for all type tests unless otherwise stated.
5.1.2 Sequence of tests
Prior to commencement of type tests, the valve, valve sections and/or the components of them should be demonstrated to have withstood the routine tests to ensure proper manufacture.
The type tests specified can be carried out in any order. 5.1.3 Ambient temperature for testing The tests shall be performed at the prevailing ambient temperature of the test facility, unless otherwise specified. 5.1.4 Frequency for testing AC dielectric tests can be performed at either 50 Hz or 60 Hz. For operational tests, specific requirements regarding the frequency for testing are given in 5.3.1. 5.1.5 Test reports
At the completion of the type tests, the supplier shall provide type test reports in accordance with Clause 14. 5.2 Test conditions for dielectric tests
5.2.1 General
Dielectric tests shall be performed on a completely assembled valve. The valve shall be assembled with all auxiliary components except for the valve arrester, if used. Unless otherwise specified, the valve electronics shall be energized. The cooling and insulating fluids in particular shall be in a condition that represents service conditions such as conductivity, except for the flow rate and anti-freezing media content, which can be reduced. If any object or device external to the structure is necessary for proper representation of the stresses during the test, it shall also be present or simulated in the test. Metallic parts of the valve structure which are not part of the test shall be shorted together and connected to enclosure earth in a manner appropriate to the test in question. 5.2.2 Treatment of redundancy in dielectric tests All dielectric tests on a complete valve shall be carried out with redundant thyristor levels short-circuited, except where otherwise indicated. SIST EN 62823:2016

IEC 62823:2015 © IEC 2015 – 17 – 5.2.3 Atmospheric correction factor When specified in the relevant clause, atmospheric correction shall be applied to the test voltages in accordance with IEC 60060-1. The reference conditions to which correction shall be made are the following. – Pressure:
If the insulation coordination of the tested part of the thyristor valve is based on standard rated withstand voltages according to IEC 60071-1, correction factors are only applied for site altitudes as exceeding 1 000 m. Hence, if the altitude of the site at which the equipment will be installed is less than 1 000 m, then the standard atmospheric air pressure (b0 = 101,3 kPa) shall be used with no correction for altitude. If as [ 1 000 m, then the standard procedure according to IEC 60060-1 is used except that the reference atmospheric pressure b0 is replaced by the atmospheric pressure corresponding to an altitude of 1 000 m (b1 000m). If the insulation coordination of the tested part of the thyristor valve is not based on standard rated withstand voltages according to IEC 60071-1, then the standard procedure according to IEC 60060-1 is used with the reference atmospheric pressure b0 (b0 = 101,3 kPa). – Temperature: design maximum valve hall air temperature (°C). – Humidity: design minimum valve hall absolute humidity (g/m3).
The values to be used shall be specified by the supplier. 5.3 Test conditions for operational tests
5.3.1 General Where possible, a complete thyristor valve should be tested. Otherwise the tests may be performed on thyristor valve sections. The choice depends mainly upon the thyristor valve design and the test facilities available. Where tests on the thyristor valve sections are proposed, the tests specified in this International Standard are valid for thyristor valve sections containing five or more series-connected thyristor levels. If tests on thyristor valve sections with fewer than five thyristor levels are proposed, additional test safety factors shall be agreed upon. Under no circumstances shall the number of series-connected thyristor levels in a thyristor valve section be less than three. Operational tests may be performed at a power frequency different from the service frequency, e.g. 50 Hz instead of 60 Hz or vice versa. Some operational stresses such as switching losses or I2t of short-circuit current are affected by the actual power frequency during tests. When this situation occurs, the test conditions shall be reviewed and appropriate changes made to ensure that the valve stresses are at least as severe as they would be if the tests were performed at the service frequency. The coolant shall be in a condition representative of service conditions. Flow and temperature, in particular, shall be set to the most unfavourable values appropriate to the test in question. Anti-freezing media content should, preferably, be equivalent to the service condition; however, where this is not practicable, a correction factor agreed between the supplier and the purchaser shall be applied. Unless otherwise specified, the thyristor junction temperature during operational tests shall not be less than the temperature in service. 5.3.2 Treatment of redundancy in operational tests For operational tests, redundant valve levels shall not be short-circuited. The test voltages used shall be adjusted by means of a scaling factor kn: SIST EN 62823:2016

– 18 – IEC 62823:2015 © IEC 2015 rttutnNNNk−= where Ntut
is the number of series thyristor levels in the test object; Nt
is the total number of series thyristor levels in the valve; Nr
is the total number of redundant series thyristor levels in the valve. 5.4 Criteria for successful type testing 5.4.1 General Experience in industry shows that, even with the most careful design of valves, it is not possible to avoid occasional random failures of thyristor level components during service operation. Even though these failures may be stress-related, they are considered random to the extent that the cause of failure or the relationship between failure rate and stress cannot be predicted or is not amenable to precise quantitative definition. Type tests subject valves or valve sections, within a short time, to multiple stresses that generally correspond to the worst stresses that can be experienced by the equipment not more than a few times during the life of the valve. Considering the above, the criteria for successful type testing set out below therefore permit a small number of thyristor levels to fail during type testing, providing that the failures are rare and do not show any pattern that is indicative of inadequate design. 5.4.2 Criteria applicable to valve levels
The following criteria are applicable to valve levels. a) If, following a type test as listed in Clause 6, the number of failed thyristor levels is greater than the value specified in column 2 of Table 1, then the valve shall be deemed to have failed the type tests. b) If, following a type test, one thyristor level (or more if still within the limit in column 2 of Table 1) has become short-circuited, then the failed level(s) shall be restored and this type test repeated.
c) If the cumulative number of short-circuited thyristor levels during all type tests exceeds the number given in column 3 of Table 1, then the valve shall be deemed to have failed the type test programme. d) When type tests are performed on valve sections, the criteria for acceptance above also apply since the number of valve sections tested shall be not less than the number of sections in a complete valve (see 5.1.1.2). e) The valve or valve sections shall be checked after each type test to determine whether or not any thyristor levels have become short-circuited. Failed thyristors or auxiliary components found during or at the end of a type test may be replaced before further testing. f) At the completion of the test programme, the valve or valve sections shall undergo a series of check tests, which shall include the following checks as a minimum: – check for voltage withstand of thyristor levels in both forward and reverse directions; – check of the gating circuits, where applicable; – check of the monitoring circuits; – check of the thyristor level protection circuits by application of transient voltages above and below the protection setting(s), where applicable; – check of the voltage grading circuits. g) Thyristor level short circuits occurring during the check tests shall be counted as part of the criteria for acceptance defined above. In addition to short-circuited levels, the total number of thyristor levels exhibiting faults which do not result in thyristor level short circuit, which are discovered during the type test programme and the subsequent check SIST EN 62823:2016

IEC 62823:2015 © IEC 2015 – 19 – tests, shall not exceed the number given in column 4 of Table 1. If the total number of such levels exceeds the number given in column 4 of Table 1, then the nature of the faults and their cause shall be reviewed and additional action, if any, agreed between purchaser and supplier. h) When applying the percentage criteria to determine the permitted maximum number of short-circuited thyristor levels and the permitted maximum number of levels with faults which have not resulted in a thyristor level becoming short-circuited, it is usual practice to round off all fractions to the next highest integer, as illustrated in Table 1. Table 1 – Valve level faults permitted during type tests Number of thyristor levels in a completed valve minus the number of redundant levels Number of thyristor levels permitted to become short-circuited in any one type test Total number of thyristor levels permitted to become short-circuited in all type tests Additional number of thyristor levels, in all type tests, which have experienced a fault but have not become short-circuited Up to 33 1 2 2 34 to 67 2 3 3 [ 67 2 4 4
The distribution of short-circuited levels and of other thyristor level faults at the end of all type tests shall be essentially random and not show any pattern that may be indicative of inadequate design. 5.4.3 Criteria applicable to the valve as a whole
No breakdown of or external flashover across common electrical equipment associated with more than one thyristor level of the valve shall occur. There shall be no disruptive discharge in dielectric material forming part of the valve structure, cooling ducts, light guides or other insulating parts of the pulse transmission and distribution system. Component and conductor surface temperatures, together with associated current-carrying joints and connections, and th
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