SIST IEC/TR 61241-2-2:1998

Electrical apparatus for use in the presence of combustible dust - Part 2: Test methods - Section 2: Method for determining the electrical resistivity of dust in layers

Specifies a test method to determine, by application of a d.c. voltage, the electrical resistivity of a layer of dust. Is to be used in the design, construction, testing and application of electrical apparatus for use in the presence of combustible dust. This publication has the status of a technical report.[
]The contents of the corrigendum of May 1994 have been included in this copy.

Matériels électriques destinés à être utilisés en présence de poussières combustibles - Partie 2: Méthodes d'essais - Section 2: Méthode de détermination de la résistivité électrique des couches de poussières

Indique une méthode d'essai pour la détermination de la résistivité électrique d'une couche de poussière lorsqu'on y applique une tension continue. S'applique à la conception, à la construction, aux essais et à l'utilisation du matériel électrique destiné à être utilisé en présence de poussière combustible. Cette publication a le statut d'un rapport technique.[
]Le contenu du corrigendum de mai 1994 a été pris en considération dans cet exemplaire.

Electrical apparatus for use in the presence of combustible dust - Part 2: Test methods - Section 2: Method for determining the electrical resistivity of dust in layers

General Information

• Status: Withdrawn
• Publication Date: 31-Mar-1998
• Withdrawal Date: 31-Jan-2001
• ICS: 29.260.20 - Electrical apparatus for explosive atmospheres
• Technical Committee: EXP - Electrical apparatus for explosive atmospheres
• Current Stage: 9900 - Withdrawal (Adopted Project)
• Start Date: 01-Feb-2001
• Due Date: 01-Feb-2001
• Completion Date: 01-Feb-2001
• Ref Project: IEC 60071-5:2014 - Insulation co-ordination - Part 5: Procedures for high-voltage direct current (HVDC) converter stations

Relations

• Replaced By: SIST EN 61241-2-2:2001 - Electrical apparatus for use in the presence of combustible dust -- Part 2: Test methods -- Section 2: Method for determining the electrical resistivity of dust in layers
• Effective Date: 01-Feb-2001

Standards Content (Sample)

IEC 60071-5
®

Edition 1.0 2014-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside


Insulation co-ordination –
Part 5: Procedures for high-voltage direct current (HVDC) converter stations

Coordination de l’isolement –
Partie 5: Procédures pour les stations de conversion à courant continu haute
tension (CCHT)
IEC 60071-5:2014-10(en-fr)

---------------------- Page: 1 ----------------------
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IEC 60071-5

®


Edition 1.0 2014-10




INTERNATIONAL



STANDARD




NORME



INTERNATIONALE
colour

inside










Insulation co-ordination –

Part 5: Procedures for high-voltage direct current (HVDC) converter stations




Coordination de l’isolement –

Partie 5: Procédures pour les stations de conversion à courant continu haute

tension (CCHT)















INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE

PRICE CODE
INTERNATIONALE

CODE PRIX XD


ICS 29.080.30 ISBN 978-2-8322-1887-7



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® Registered trademark of the International Electrotechnical Commission
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---------------------- Page: 3 ----------------------
– 2 – IEC 60071-5:2014 © IEC 2014

CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 General . 9
1.1 Scope . 9
1.2 Additional background . 9
2 Normative references . 10
3 Terms and definitions. 10
4 Symbols and abbreviations . 16
4.1 General . 16
4.2 Subscripts . 16
4.3 Letter symbols . 16
4.4 Abbreviations . 17
5 Typical HVDC converter station schemes . 17
6 Principles of insulation co-ordination . 21
6.1 General . 21
6.2 Essential differences between a.c. and d.c. systems . 21
6.3 Insulation co-ordination procedure . 21
6.4 Comparison of withstand voltage selection in a.c. and d.c. systems . 22
7 Voltages and overvoltages in service . 24
7.1 Continuous operating voltages at various locations in the converter station . 24
7.2 Peak continuous operating voltage (PCOV) and crest continuous operating
voltage (CCOV) . 28
7.3 Sources and types of overvoltages . 30
7.4 Temporary overvoltages . 31
7.4.1 General . 31
7.4.2 Temporary overvoltages on the a.c. side . 31
7.4.3 Temporary overvoltages on the d.c. side . 31
7.5 Slow-front overvoltages . 31
7.5.1 General . 31
7.5.2 Slow-front overvoltages on the a.c. side . 31
7.5.3 Slow-front overvoltages on the d.c. side . 32
7.6 Fast-front, very-fast-front and steep-front overvoltages . 33
8 Arrester characteristics and stresses. 34
8.1 Arrester characteristics . 34
8.2 Arrester specification. 35
8.3 Arrester stresses . 35
8.3.1 General . 35
8.3.2 AC bus arrester (A) . 36
8.3.3 AC filter arrester (FA) . 37
8.3.4 Transformer valve winding arresters (T) . 37
8.3.5 Valve arrester (V) . 37
8.3.6 Bridge arrester (B) . 40
8.3.7 Converter unit arrester (C) . 41
8.3.8 Mid-point d.c. bus arrester (M) . 41
8.3.9 Converter unit d.c. bus arrester (CB) . 42
8.3.10 DC bus and d.c. line/cable arrester (DB and DL/DC) . 42

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IEC 60071-5:2014 © IEC 2014 – 3 –
8.3.11 Neutral bus arrester (E, EL, EM in Figure 3, EB, E1, EL, EM in Figure 1) . 42
8.3.12 DC reactor arrester (DR) . 43
8.3.13 DC filter arrester (FD) . 44
8.3.14 Earth electrode station arrester . 44
8.4 Protection strategy . 44
8.4.1 General . 44
8.4.2 Insulation directly protected by a single arrester . 44
8.4.3 Insulation protected by more than one arrester in series . 45
8.4.4 Valve side neutral point of transformers . 45
8.4.5 Insulation between phase conductors of the converter transformer . 45
8.4.6 Summary of protection strategy . 45
8.5 Summary of events and stresses . 47
9 Design procedure of insulation co-ordination . 49
9.1 General . 49
9.2 Arrester requirements. 49
9.3 Characteristics of insulation. 51
9.4 Representative overvoltages (U ) . 51
rp
9.5 Determination of the co-ordination withstand voltages (U ) . 52
cw
9.6 Determination of the required withstand voltages (U ) . 52
rw
9.7 Determination of the specified withstand voltage (U ) . 54
w
10 Study tools and system modelling . 54
10.1 General . 54
10.2 Study approach and tools . 54
10.3 System details . 55
10.3.1 Modelling and system representation . 55
10.3.2 AC network and a.c. side of the HVDC converter station . 57
10.3.3 DC overhead line/cable and earth electrode line details . 58
10.3.4 DC side of an HVDC converter station details . 58
11 Creepage distances . 59
11.1 General . 59
11.2 Base voltage for creepage distance . 59
11.3 Creepage distance for outdoor insulation under d.c. voltage . 59
11.4 Creepage distance for indoor insulation under d.c. or mixed voltage . 60
11.5 Creepage distance of a.c. insulators . 60
12 Clearances in air . 60
Annex A (informative) Example of insulation co-ordination for conventional HVDC
converters . 62
A.1 General . 62
A.2 Arrester protective scheme . 62
A.3 Arrester stresses, protection and insulation levels. 62
A.3.1 General . 62
A.3.2 Slow-front overvoltages transferred from the a.c. side . 63
A.3.3 Earth fault between valve and upper bridge transformer bushing . 63
A.4 Transformer valve side withstand voltages . 66
A.4.1 Phase-to-phase . 66
A.4.2 Upper bridge transformer phase-to-earth (star). 67
A.4.3 Lower bridge transformer phase-to-earth (delta) . 67
A.5 Air-insulated smoothing reactors withstand voltages . 67
A.5.1 Terminal-to-terminal slow-front overvoltages . 67

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– 4 – IEC 60071-5:2014 © IEC 2014

A.5.2 Terminal-to-earth . 68
A.6 Results . 68
Annex B (informative) Example of insulation co-ordination for capacitor commutated
converters (CCC) and controlled series capacitor converters (CSCC) . 72
B.1 General . 72
B.2 Arrester protective scheme . 72
B.3 Arrester stresses, protection and insulation levels. 72
B.3.1 General . 72
B.3.2 Transferred slow-front overvoltages from the a.c. side . 73
B.3.3 Earth fault between valve and upper bridge transformer bushing . 74
B.4 Transformer valve side withstand voltages . 77
B.4.1 Phase-to-phase . 77
B.4.2 Upper bridge transformer phase-to-earth (star). 77
B.4.3 Lower bridge transformer phase-to-earth (delta) . 77
B.5 Air-insulated smoothing reactors withstand voltages . 78
B.5.1 Slow-front terminal-to-terminal overvoltages . 78
B.5.2 Terminal-to-earth . 78
B.6 Results . 79
Annex C (informative) Considerations for insulation co-ordination of some special
converter configurations . 87
C.1 Procedure for insulation co-ordination of back-to-back type of HVDC links . 87
C.2 Procedure for insulation co-ordination of parallel valve groups . 87
C.2.1 General . 87
C.2.2 AC bus arrester (A) . 88
C.2.3 AC filter arrester (FA) . 88
C.2.4 Valve arrester (V) . 88
C.2.5 Bridge arrester (B) and converter unit arrester (C) . 88
C.2.6 Mid-point arrester (M) . 88
C.2.7 Converter unit d.c. bus arrester (CB) . 88
C.2.8 DC bus and d.c. line/cable arrester (DB and DL) . 89
C.2.9 Neutral bus arrester (E) . 89
C.2.10 DC reactor arrester (DR) . 89
C.2.11 DC filter arrester (FD) . 89
C.2.12 New converter stations with parallel valve groups . 89
C.3 Procedure for insulation co-ordination of upgrading existing systems with
series-connected valve groups . 89
C.3.1 General . 89
C.3.2 AC bus arrester (A) . 90
C.3.3 AC filter arrester (FA) . 90
C.3.4 Valve arrester (V) . 90
C.3.5 Bridge arrester (B) and converter unit arrester (C) . 90
C.3.6 Mid-point arrester (M) . 90
C.3.7 Converter unit d.c. bus arrester (CB), d.c. bus and d.c. line/cable
arrester (DB and DL) . 91
C.3.8 Neutral bus arrester (E) . 91
C.3.9 DC reactor arrester (DR) . 91
C.3.10 DC filter arrester (FD) . 91
C.4 Overvoltages in the a.c. network due to closely coupled HVDC links . 91
C.5 Effect of gas-insulated switchgear on insulation co-ordination of HVDC
converter stations . 92

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IEC 60071-5:2014 © IEC 2014 – 5 –
Annex D (informative) Typical arrester characteristics . 93
Bibliography . 94

Figure 1 – Possible arrester locations in a pole with two 12-pulse converters in series . 19
Figure 2 – Possible arrester locations for a back-to-back converter station . 20
Figure 3 – HVDC converter station with one 12-pulse converter bridge per pole . 25
Figure 4 – Continuous operating voltages at various locations (location identification
according to Figure 3) . 27
Figure 5 – Operating voltage of a valve arrester (V), rectifier operation . 29
Figure 6 – Operating voltage of a mid-point arrester (M), rectifier operation . 29
Figure 7 – Operating voltage of a converter bus arrester (CB), rectifier operation . 30
Figure 8 – One pole of an HVDC converter station . 57
Figure A.1 – AC and d.c. arresters . 69
Figure A.2 – Valve arrester stresses for slow-front overvoltages from a.c. side . 69
Figure A.3 – Arrester V2 stress for slow-front overvoltage from a.c. side . 70
Figure A.4 – Valve arrester stresses for earth fault between valve and upper bridge
transformer bushing . 70
Figure A.5 – Arrester V1 stress for earth fault between valve and upper bridge
transformer bushing . 71
Figure B.1 – AC and d.c. arresters for CCC and CSCC converters . 80
Figure B.2 – Valve arrester stresses for slow-front overvoltages from a.c. side . 81
Figure B.3 – Arrester V2 stress for slow-front overvoltage from a.c. side . 82
Figure B.4 – Valve arrester stresses for earth fault between valve and upper bridge
transformer bushing . 84
Figure B.5 – Arrester V1 stress for earth fault between valve and upper bridge
transformer bushing . 85
Figure B.6 – Stresses on capacitor arresters C and C during earth fault between
cc sc
valve and upper bridge transformer bushing . 86
Figure C.1 – Expanded HVDC converter with parallel valve groups . 88
Figure C.2 – Upgraded HVDC converter with series valve group . 90
Figure D.1 – Typical arrester V-I characteristics . 93

Table 1 – Classes and shapes of overvoltages, standard voltage shapes and standard
withstand voltage tests . 11
Table 2 – Symbol description. 20
Table 3 – Comparison of the selection of withstand voltages for a.c. equipment with
that for HVDC converter station equipment . 23
Table 4 – Arrester protection on the d.c. side: Single 12-pulse converter (Figure 3) . 46
Table 5 – Arrester protection on the d.c. side: Two 12-pulse converters (Figure 1) . 46
Table 6 – Events stressing arresters: Single 12-pulse converter (Figure 3). 48
Table 7 – Types of arrester stresses for different events: Single 12-pulse converter
(Figure 3) . 48
Table 8 – Arrester requirements . 50
Table 9 – Representative overvoltages and required withstand voltages. 51
Table 10 – Indicative values of ratios of required impulse withstand voltage to impulse

protective level . 54
Table 11 – Origin of overvoltages and associated frequency ranges. 56

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– 6 – IEC 60071-5:2014 © IEC 2014

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

INSULATION CO-ORDINATION –

Part 5: Procedures for high-voltage
direct current (HVDC) converter stations

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 th
...

SLOVENSKI STANDARD
SIST IEC/TR 61241-2-2:1998
01-april-1998
Electrical apparatus for use in the presence of combustible dust - Part 2: Test
methods - Section 2: Method for determining the electrical resistivity of dust in
layers
Electrical apparatus for use in the presence of combustible dust - Part 2: Test methods -
Section 2: Method for determining the electrical resistivity of dust in layers
Matériels électriques destinés à être utilisés en présence de poussières combustibles -
Partie 2: Méthodes d'essais - Section 2: Méthode de détermination de la résistivité
électrique des couches de poussières
Ta slovenski standard je istoveten z: IEC/TS 61241-2-2
ICS:
29.260.20 (OHNWULþQLDSDUDWL]D Electrical apparatus for
HNVSOR]LYQDR]UDþMD explosive atmospheres
SIST IEC/TR 61241-2-2:1998 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST IEC/TR 61241-2-2:1998

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SIST IEC/TR 61241-2-2:1998
RAPPORT CEI
TECHNIQUE - TYPE 2 IEC
1241-2-2
TECHNICAL
Première édition
REPORT - TYPE 2 First edition
1993-08
Matériels électriques destinés à être utilisés
en présence de poussières combustibles -
Partie 2:
Méthodes d'essais -
Section 2: Méthode de détermination de
la résistivité électrique des couches de poussières
Electrical apparatus for use in the
presence of combustible dust -
Part 2:
Test methods -
2: Method for determining the electrical
Section
resistivity of dust in layers
réservés — Copyright — all rights reserved
© CEI 1993 Droits de reproduction
No part of this publication may be reproduced or util ized in
Aucune partie de cette publication ne peut être reproduite ni
any form or by any means, electronic or mechanical,
utilisée sous quelque forme que ce soit et par aucun pro-
including photocopying and microfilm, without permission
cédé, électronique ou mécanique, y compris la photocopie et
les microfilms, sans l'accord écrit de l'éditeur. in writing from the publisher.
Genève, Suisse
Bureau Central de la Commission Electrotechnique Internationale 3, rue de Varembé
Commission Electrotechnique Internationale CODE PRIX
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IEC MemnyHapoaHaa 3nelsrporexHHVecKaa KoMuccaa
catalogue en vigueur
Pour prix, voir •
•
For price, see current catalogue

---------------------- Page: 3 ----------------------

SIST IEC/TR 61241-2-2:1998
IEC Publication 1241-2-2
Publication 1241-2-2 de la CEI
(First edition - 1993)
(Première édition - 1993)
Matériels électriques destinés Electrical apparatus
for use in the presence
à être utilisés en présence
of combustible dust
de poussières combustibles
Part 2: Test methods
Partie 2: Méthodes d’essais
Section 2: Method for determining
Section 2: Méthode de détermination
the electrical resistivity
de la résistivité électrique
of dust in layers
des couches de poussières
C O R R I G E N D U M 1
Page 14
Page 15
6.3 Calcul de la résistivit
6.3 Calculation of resistivity
Sous la seconde équation de l’article, au
Under the second equation in the clause,
lieu de:
instead of:
o
where
ρ est la résistivité en Ω;
ρ is the resistivity in Ω;
lire:
read:
o
where
Ω m;
ρ est la résistivité en • ρ Ω•m;
is the resistivity in
May 1994
Mai 1994

---------------------- Page: 4 ----------------------

SIST IEC/TR 61241-2-2:1998

---------------------- Page: 5 ----------------------

SIST IEC/TR 61241-2-2:1998
1241-2-2 © I EC:1993 - 5 -
INTERNATIONAL ELECTROTECHNICAL COMMISSION
ELECTRICAL APPARATUS FOR USE IN THE
DUST -
PRESENCE OF COMBUSTIBLE
Part 2: Test methods -
Section 2: Method for determining the electrical resistivity
of dust in layers
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization
comprising all national electrotechnical committees (IEC National Committees). The object of the IEC is to
promote international cooperation on all questions concerning standardization in the electrical and
electronic fields. To this end and in addition to other activities, the IEC publishes International Standards.
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. The 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 the IEC on technical matters, prepared by technical committees on
which all the National Committees having a special interest therein are represented, express, as nearly as
possible, an international consensus of opinion on the subjects dealt with.
They have the form of recommendations for international use published in the form of standards, technical
3)
reports or guides and they are accepted by the National Committees in that sense.
In order to promote international unification, IEC National Committees undertake to apply IEC International
4)
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
The main task of IEC technical committees is to prepare International Standards. In excep-
tional circumstances, a technical committee may propose the publication of a technical
report of one of the following types:
cannot be obtained for the publication of an Inter-
• type 1, when the required suppo rt
national Standard, despite repeated efforts;
• type 2, when the subject is still under technical development or where for any other
reason there is the future but not immediate possibility of an agreement on an Inter-
national Standard;
type 3, when a technical committee has collected data of a different kind from that
•
which is normally published as an International Standard, for example "state of the art".
Technical reports of types 1 and 2 are subject to review within three years of publication to
decide whether they can be transformed into International Standards. Technical reports of
type 3 do not necessarily have to be reviewed until the data they provide are considered
to be no longer valid or useful.
IEC 1241-2-2 which is a technical report of type 2, has been prepared by sub-committee 31H:
Apparatus for use in the presence of combustible dust, of IEC technical committee 31:
Electrical apparatus for explosive atmospheres.

---------------------- Page: 6 ----------------------

SIST IEC/TR 61241-2-2:1998
1241-2-2 - 9 -
40 I EC:1993
INTRODUCTION
This technical repo rt is applicable to the determination of the electrical resistivity of dust in
layers.
The test method is not suitable for use with recognized explosives, gunpowder, dynamite,
or substances or mixtures of substances which may, under some circumstances, behave
in a similar manner. Where any doubt exists about the existence of a hazard due to
explosive properties, an indication may be obtained by placing a very small quantity of
the dust in question on the heated surface of the apparatus prescribed in IEC 1241-2-1*,
heated to 400 °C.
The test for explosivity will not always reveal the explosive nature of a dust so that a "fail
to danger* situation could arise.
NOTE - Precautions should be taken to safeguard the health of personnel conducting the tests against the
risk of fire, explosion and/or the effects, including toxic effects, of combustion.
This test method is applicable to the construction and application of electrical apparatus
for use in the presence of combustible dust.
Electrical apparatus for use in the presence of combustible dust – Part 2: Test
* IEC 1241-2-1: 1993,
methods – Section 1 (under consideration).

---------------------- Page: 7 ----------------------

SIST IEC/TR 61241-2-2:1998
- 13 -
1241-2-2 ©IEC:1993
4 Test apparatus
Figures 1 and 2 give details for the construction of the test apparatus. The test cell (see
figure 1) is of open construction, and consists of two stainless steel bars with nominal
dimensions: length (W) - 100 mm, height (H) - 10 mm, breadth (B) - 20 mm to 40 mm.
These bars are placed at a nominal distance apart of (L) - 10 mm on a base with a thick-
ness between 5 mm and 10 mm.
NOTE - Glass or polytetrafluorethylene (PTFE) have been found to be suitable materials for the base.
Two glass bars, also with a nominal height of 10 mm, are placed across the ends of the
electrodes to keep the dust layer in place.
Figure 2 illustrates an example of a suitable electrical circuit for making the resistivity
measurement. It contains a 10 kf2 resistor to restrict the breakdown current to a maximum
value of 0,2 A at a maximum supply voltage of 2 000 V d.c. Other circuits with comparable
characteristics and accuracy may be used.
The current-to-voltage converter has six ranges to deal with the various values of supply
voltage and dust resistivity. A voltage inverter is present to provide a positive output.
All resistors are 5 %, 0,5 W high-stability carbon-film type.
5 Test sample
The test sample shall be homogeneous and representative of the dust received for testing.
When dust is received, it should be put in a closed vessel until tested, or it should be
conditioned, or it should be tested directly, and the moistu
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