kSIST FprEN IEC 60079-25:2020

Explosive atmospheres - Part 25: Intrinsically safe electrical systems

IEC 60079-25:2020 contains the specific requirements for design, construction and assessment of intrinsically safe systems, Type of Protection “i”, intended for use, as a whole or in part, in locations in which the use of Group I, II or III Ex Equipment is required. This document supplements and modifies the general requirements of IEC 60079-0 and the intrinsic safety standard IEC 60079-11. Where a requirement of this standard conflicts with a requirement of IEC 60079-0 or IEC 60079-11, the requirement of this standard takes precedence. The installation requirements of Group II or Group III systems designed in accordance with this standard are specified in IEC 60079-14. This third edition cancels and replaces the second edition published in 2010 and constitutes a technical revision.

Explosionsfähige Atmosphäre - Teil 25: Eigensichere Systeme

Atmosphères explosives - Partie 25: Systèmes électriques de sécurité intrinsèque

IEC 60079-25:2020 contient les exigences spécifiques de conception, de construction et d’évaluation des systèmes de sécurité intrinsèque, de mode de protection "i", destinés à être utilisés, en tout ou en partie, dans des atmosphères qui exigent l’emploi de matériel Ex du Groupe I, II ou III. Le présent document complète et modifie les exigences générales de l’IEC 60079-0 et de la norme de sécurité intrinsèque IEC 60079-11. En cas de contradiction entre une exigence de la présente norme et une exigence de l’IEC 60079-0 ou de l’IEC 60079-11, l’exigence de la présente norme prévaut. Les exigences d’installation pour les systèmes du Groupe II ou du Groupe III conçus conformément à la présente norme sont spécifiées dans l’IEC 60079-14. Cette troisième édition annule et remplace la deuxième édition parue en 2010 et constitue une révision technique.

Eksplozivne atmosfere - 25. del: Lastnovarni električni sistemi

General Information

• Status: Not Published
• Public Enquiry End Date: 30-May-2019
• ICS: 29.260.20 - Electrical apparatus for explosive atmospheres
• Technical Committee: EXP - Electrical apparatus for explosive atmospheres
• Current Stage: 5020 - Formal vote (FV) (Adopted Project)
• Start Date: 30-Mar-2020
• Due Date: 18-May-2020
• Completion Date: 12-Jun-2020
• Directive: 2014/34/EU - Directive 2014/34/EU Of The European Parliament And Of The Council of 26 February 2014 on the harmonisation of the laws of the Member States relating to equipment and protective systems intended for use in potentially explosive atmospheres (recast)
• Mandate: M/BC/CEN/92/46 - Standardization mandate assigned to CEN/CENELEC concerning equipment and protective systems intended for use in potentially explosive atmospheres
• Ref Project: FprEN IEC 60079-25:2020 - Explosive atmospheres - Part 25: Intrinsically safe electrical systems

RELATIONS

• Revised: SIST EN 60079-25:2010 - Explosive atmospheres - Part 25: Intrinsically safe systems (IEC 60079-25:2010)
• Effective Date: 13-Jun-2017
• Revised: SIST EN 60079-25:2010/AC:2014 - Explosive atmospheres - Part 25: Intrinsically safe electrical systems
• Effective Date: 13-Jun-2017

Standards Content (sample)

SLOVENSKI STANDARD
oSIST prEN IEC 60079-25:2019
01-maj-2019
(NVSOR]LYQHDWPRVIHUHGHO/DVWQRYDUQLHOHNWULþQLVLVWHPL
Explosive atmospheres - Part 25: Intrinsically safe electrical systems
Explosionsfähige Atmosphäre - Teil 25: Eigensichere Systeme
Atmosphères explosives - Partie 25: Systèmes électriques de sécurité intrinsèque
Ta slovenski standard je istoveten z: prEN IEC 60079-25:2019
ICS:
29.260.20 (OHNWULþQLDSDUDWL]D Electrical apparatus for
HNVSOR]LYQDR]UDþMD explosive atmospheres
oSIST prEN IEC 60079-25:2019 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN IEC 60079-25:2019
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oSIST prEN IEC 60079-25:2019
31G/294/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 60079-25 ED3
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2019-03-22 2019-06-14
SUPERSEDES DOCUMENTS:
31G/279/CD,31G/284A/CC
IEC SC 31G : INTRINSICALLY-SAFE APPARATUS
SECRETARIAT: SECRETARY:
United Kingdom Mr Nicholas Ludlam
OF INTEREST TO THE FOLLOWING COMMITTEES: PROPOSED HORIZONTAL STANDARD:
TC 18
Other TC/SCs are requested to indicate their interest, if
any, in this CDV to the secretary.
FUNCTIONS CONCERNED:
EMC ENVIRONMENT QUALITY ASSURANCE SAFETY

SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING

Attention IEC-CENELEC parallel voting
The attention of IEC National Committees, members of
CENELEC, is drawn to the fact that this Committee Draft
for Vote (CDV) is submitted for parallel voting.
The CENELEC members are invited to vote through the
CENELEC online voting system.

This document is still under study and subject to change. It should not be used for reference purposes.

Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of

which they are aware and to provide supporting documentation.
TITLE:
Explosive atmospheres - Part 25: Intrinsically safe electrical systems
PROPOSED STABILITY DATE: 2025
NOTE FROM TC/SC OFFICERS:

Copyright © 2019 International Electrotechnical Commission, IEC. All rights reserved. It is permitted to

download this electronic file, to make a copy and to print out the content for the sole purpose of preparing National

Committee positions. You may not copy or "mirror" the file or printed version of the document, or any part of it, for

any other purpose without permission in writing from IEC.
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oSIST prEN IEC 60079-25:2019
IEC CDV 60079-25  IEC:2019 – 2 – 31G/294/CDV
1 CONTENTS

3 FOREWORD ........................................................................................................................... 4

4 1 Scope .............................................................................................................................. 8

5 2 Normative references ...................................................................................................... 8

6 3 Terms and definitions ...................................................................................................... 8

7 4 Descriptive system document .......................................................................................... 9

8 5 Grouping and temperature classification ........................................................................ 10

9 6 Levels of Protection ....................................................................................................... 10

10 6.1 General ................................................................................................................. 10

11 6.2 Level of Protection “ia” .......................................................................................... 10

12 6.3 Level of Protection “ib” .......................................................................................... 10

13 6.4 Level of Protection “ic” .......................................................................................... 10

14 7 Non-intrinsically safe circuits ......................................................................................... 11

15 8 Interconnecting wiring / cables used in an intrinsically safe system ............................... 11

16 8.1 General ................................................................................................................. 11

17 8.2 Cables containing a single intrinsically safe circuit ................................................ 11

18 8.3 Cables containing more than one intrinsically safe circuit ...................................... 11

19 9 Requirements of single and multi-circuit cables ............................................................. 11

20 9.1 General ................................................................................................................. 11

21 9.2 Dielectric strength ................................................................................................. 12

22 9.2.1 Cables containing a single intrinsically safe circuit ......................................... 12

23 9.2.2 Cables containing more than one intrinsically safe circuit .............................. 12

24 9.3 Intrinsic safety parameters of cables ..................................................................... 12

25 9.4 Conducting screens .............................................................................................. 12

26 9.5 Types of multi-circuit cables .................................................................................. 12

27 9.5.1 General ......................................................................................................... 12

28 9.5.2 Type A cable ................................................................................................. 12

29 9.5.3 Type B cable ................................................................................................. 13

30 9.5.4 Type C cable ................................................................................................. 13

31 10 Enclosures .................................................................................................................... 13

32 11 Earthing and bonding of intrinsically safe systems ......................................................... 13

33 12 Assessment of an intrinsically safe system .................................................................... 13

34 12.1 General ................................................................................................................. 13

35 12.2 Systems containing only apparatus certified to IEC 60079-11 ............................... 14

36 12.3 Systems containing apparatus not separately evaulated to IEC 60079-11 ............. 14

37 12.4 Systems containing a single power source ............................................................ 14

38 12.5 Systems containing more than one power source .................................................. 14

39 12.5.1 General ......................................................................................................... 14

40 12.5.2 Systems containing linear and non-linear sources of power ........................... 14

41 12.6 Simple apparatus .................................................................................................. 16

42 12.7 Assessment of capacitance, inductance and cable L/R ......................................... 17

43 12.7.1 General ......................................................................................................... 17

44 12.7.2 Unspecified Parameters ................................................................................. 17

45 12.7.3 Output Parameter adjustments for Level of Protection ................................... 17

46 12.7.4 Effect of combined lumped capacitance and inductance ................................ 17

47 12.7.5 Determination of L/R ...................................................................................... 17

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48 12.8 Faults in multi-circuit cables .................................................................................. 18

49 12.9 Type verifications and type tests ........................................................................... 18

50 13 Predefined systems ....................................................................................................... 18

51 Annex A (informative) Assessment of a simple intrinsically safe system ............................... 19

52 Annex B (informative) Assessment of circuits with more than one power source .................. 21

53 Annex C (informative) Interconnection of non-linear and linear intrinsically safe circuits ...... 24

54 C.1 General ................................................................................................................. 24

55 C.2 Assessment of the output characteristics of the power sources ............................. 24

56 C.3 Assessment of interconnection possibilities and resultant output

57 characteristics ...................................................................................................... 27

58 C.4 Determination of intrinsic safety and the use of graphs ......................................... 30

59 C.5 Verification against IEC 60079-11 ......................................................................... 31

60 C.6 Illustration of the procedure .................................................................................. 31

61 C.7 Diagrams .............................................................................................................. 35

62 Annex D (normative) Verification of inductive parameters .................................................... 46

63 Annex E (informative) Example format for a descriptive system document ........................... 48

64 Annex F (informative) Use of simple apparatus in systems .................................................. 50

65 F.1 General ................................................................................................................. 50

66 F.2 Use of apparatus with ‘simple apparatus’ .............................................................. 51

67 Annex G (normative) FISCO systems ................................................................................... 52

68 G.1 General ................................................................................................................. 52

69 G.2 System requirements ............................................................................................ 52

70 G.2.1 General ......................................................................................................... 52

71 G.3 Additional requirements of “ic” FISCO systems ..................................................... 53

73 Figure 1 – Systems analysis ................................................................................................. 16

74 Figure B.1 – Power sources connected in series ................................................................... 22

75 Figure B.2 – Power sources connected in parallel ................................................................. 23

76 Figure B.3 – Power sources not deliberately connected ........................................................ 23

77 Figure C.1 – Equivalent circuit and output characteristic of resistive circuits ......................... 25

78 Figure C.2 – Output characteristic and equivalent circuit of a source with trapezoidal

79 characteristic ........................................................................................................................ 27

80 Figure C.3 – Current and/or voltage addition for interconnections ......................................... 30

81 Figure C.4 – Example of an interconnection .......................................................................... 32

82 Figure C.5 – Sum characteristics for the circuit as given in Figure C.4 .................................. 33

83 Figure C.6 – Current and/or voltage addition for the example given in Figure C.4 ................. 34

84 Figure C.7 – Limit curve diagram for universal source characteristic − Group IIC .................. 40

85 Figure C.8 – Limit curve diagram for universal source characteristic – Group IIB .................. 45

86 Figure D.1 – Typical inductive circuit .................................................................................... 47

87 Figure E.1 – Typical block diagram for IS system descriptive system document ................... 49

88 Figure G.1 – Typical system ................................................................................................. 54

90 Table A.1 – Simple system analysis ...................................................................................... 20

91 Table C.1 – Parameters necessary to describe the output characteristic ............................... 25

92 Table C.2 – Assignment of diagrams to equipment Groups and inductances ......................... 30

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oSIST prEN IEC 60079-25:2019
IEC CDV 60079-25  IEC:2019 – 4 – 31G/294/CDV
95 INTERNATIONAL ELECTROTECHNICAL COMMISSION
96 ______________
98 EXPLOSIVE ATMOSPHERES –
100 Part 25: Intrinsically safe electrical systems
101
102
103 FOREWORD

104 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

105 all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

106 international co-operation on all questions concerning standardization in the electrical and electronic fields. To

107 this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

108 Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

109 Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

110 in the subject dealt with may participate in this preparatory work. International, governmental and non-

111 governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

112 with the International Organization for Standardization (ISO) in accordance with conditions determined by

113 agreement between the two organizations.

114 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

115 consensus of opinion on the relevant subjects since each technical committee has representation from all

116 interested IEC National Committees.

117 3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

118 Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

119 Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

120 misinterpretation by any end user.

121 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

122 transparently to the maximum extent possible in their national and regional publications. Any divergence

123 between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

124 the latter.

125 5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

126 assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

127 services carried out by independent certification bodies.

128 6) All users should ensure that they have the latest edition of this publication.

129 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

130 members of its technical committees and IEC National Committees for any personal injury, property damage or

131 other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

132 expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

133 Publications.

134 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

135 indispensable for the correct application of this publication.

136 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

137 patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

138 International Standard IEC 60079-25 has been prepared by subcommittee 31G: Intrinsically

139 safe apparatus, of IEC technical committee 31: Equipment for explosive atmospheres.

140 This third edition cancels and replaces the second edition published in 2010 and constitutes a

141 technical revision.

142 The significance of the changes between IEC Standard, IEC 60079-25, Edition 2 (2010) and

143 IEC 60079-25, Edition 3 (2019) are as listed below:
144
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oSIST prEN IEC 60079-25:2019
IEC CDV 60079-25  IEC:2019 – 5 – 31G/294/CDV
Type
Changes Clause Minor and Extension Major
editorial technical
changes changes
References to “electrical systems” changed to 1 X
“systems”, and note added that installation
requirement for Group I are being considered
Normative references updated to remove 2 X
references that were outdated or not mentioned in
the body of the standard
Reference to IEC Electropedia and ISO Online 3 X
Browsing platform added, abbreviations dropped
from title. Definition of “system designer” deleted,
definitions of certified intrinsically safe electrical
system, and uncertified intrinsically safe electrical
system dropped
“Intrinsically safe electrical system” changed to 3.1 X
“intrinsically safe system”
Definition for “multi-circuit cable” added
3.2 X
“Maximum” changed to “total” on definitions of 3.4, 3.5 X
cable capacitance and cable inductance
“Maximum” deleted on definition of cable 3.6 X
inductance to resistance ratio
FISCO changed to definition from abbreviation 3.9 X
The requirement for the system designer to sign 4 X
and date the document dropped, editorial changes
for clarity made, and a reference to Annex E made
to show typical descriptive system documents
Title of clause changed to “Grouping and 5 X
temperature classification”, ambient temperature
range added to things to be included in the system
document, and reworded for clarity
Notes moved and reworded among the clauses. 6.1, 6.2, X
6.3, 6.4
Changed from “Ambient temperature rating” which 7 X
was moved to Clause 5, and new section renamed
“Non-intrinsically safe circuits” added
Clause reorganized into sections and some 8 X
rewording done for clarity
Title changed to “Requirements of single and multi- 9 X
circuit cables”
Requirement for insulation thickness moved into 9.1 X
this clause, and it now applies to all cables
Title changed to “Dielectric strength” and 9.2 X
consolidates requirements for single circuit and
multi-circuit cables. Requirement for dielectric
testing changed to twice circuit voltage with a
minimum of 500VAC
Dielectric strength requirements for single circuit 9.2.1 X
cables consolidated here
Dielectric strength requirements for multi- circuit 9.2.2 X
cables consolidated here
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oSIST prEN IEC 60079-25:2019
IEC CDV 60079-25  IEC:2019 – 6 – 31G/294/CDV
Type
Changes Clause Minor and Extension Major
editorial technical
changes changes
Title changed to “Intrinsic safety parameters of 9.3 X
cables”
Title changed to “Enclosures” 10 X
Most the old Clause 12 moved to 60079-14. 11 C1
This clause was Clause 13 in the previous edition, 12 X
and the entire clause has been re-arranged for
clarity and easier reading
This General clause has been re-written in list 12.1 X
format to make it easier to understand, and analysis
of single and multiple power supplies moved to 12.4
and 12.5 respectively
This clause added to clarify fault applications in 12.2 X
assemblies of certified equipment
This clause added to provide guidance on how to 12.3 X
handle non-certified items in larger assemblies.
Analysis of single power source information 12.4 X
collected here and amplified
Analysis of multiple power sources information 12.5 X
collected in this clause, information added for
clarity
The circuit analysis example dropped in text for 12.6 X
simple apparatus, new Annex F added with more
information
This section added to provide more information on 12.7 X
determining capacitance, inductance and L/R that
was moved in from Annex A
Requirements for Type A, B, and C cables 12.8 X
reworded for clarity
Information on evaluation of capacitance and Annex A X
inductance moved to 12.7
Changed from normative to informative Annex B
Reordered and rewritten for greater clarity Annex C X
Annex updated for clarity Annex E X
The former Annex F on surge protection has been Annex F C2
removed .
Annex G in the previous edition was on testing of Annex G X
cable parameters and has been removed from this
edition. Annex G is now FISCO systems.

145 NOTE: The technical changes referred to include the significance of technical changes in the revised IEC

146 Standard, but they do not form an exhaustive list of all modifications from the previous version. More guidance

147 may be found by referring to the Redline Version of the standard.
148 Explanations:
149 A) Definitions
150 Minor and editorial changes clarification
151 decrease of technical requirements
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152 minor technical change
153 editorial corrections

154 These are changes which modify requirements in an editorial or a minor technical way. They

155 include changes of the wording to clarify technical requirements without any technical change,

156 or a reduction in level of existing requirement.
157 Extension addition of technical options

158 These are changes which add new or modify existing technical requirements, in a way that

159 new options are given, but without increasing requirements for equipment that was fully

160 compliant with the previous standard. Therefore, these will not have to be considered for

161 products in conformity with the preceding edition.
162 Major technical changes addition of technical requirements
163 increase of technical requirements

164 These are changes to technical requirements (addition, increase of the level or removal)

165 made in a way that a product in conformity with the preceding edition will not always be able

166 to fulfil the requirements given in the later edition. These changes have to be considered for

167 products in conformity with the preceding edition. For these changes additional information is

168 provided in clause B) below.

169 Note: These changes represent current technological knowledge. However, these changes should not normally

170 have an influence on equipment already placed on the market.
171 B) Information about the background of ‘Major Technical Changes’

172 C1 – Most of the earthing and bonding requirements have been moved to IEC 60079-14, and

173 the surge protection requirements that were in the old Clause 12 were added here in Clause

174 11. The rest of the old Clause 12 was also removed and moved to IEC 60079-14

175 C2 – The former Annex F on surge protection has been removed and will be covered in IEC

176 60079-14, Annex F is now Simple Apparatus, which was Annex H in the previous edition

177 The text of this standard is based on the following documents:
FDIS Report on voting
31G/ /FDIS 31G/ /RVD
178

179 Full information on the voting for the approval of this standard can be found in the report on

180 voting indicated in the above table.

181 This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

182 A list of all parts of IEC 60079 series, under the general title Explosive atmospheres, can be

183 found on the IEC website.

184 The committee has decided that the contents of this publication will remain unchanged until

185 the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data

186 related to the specific publication. At this date, the publication will be
187 • reconfirmed,
188 • withdrawn,
189 • replaced by a revised edition, or
190 • amended.
191
192
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oSIST prEN IEC 60079-25:2019
IEC CDV 60079-25  IEC:2019 – 8 – 31G/294/CDV
193 EXPLOSIVE ATMOSPHERES –
194
195 Part 25: Intrinsically safe electrical systems
196
197
198
199 1 Scope

200 This part of IEC 60079 contains the specific requirements for design, construction and

201 assessment of intrinsically safe systems, Type of Protection “i”, intended for use, as a whole

202 or in part, in locations in which the use of Group I, II or III Ex Equipment is required.

203 NOTE 1 This standard is intended for use by the designer of the system who may be a manufacturer, a specialist

204 consultant or a member of the end-user’s staff.

205 This document supplements and modifies the general requirements of IEC 60079-0 and the

206 intrinsic safety standard IEC 60079-11. Where a requirement of this standard conflicts with a

207 requirement of IEC 60079-0 or IEC 60079-11, the requirement of this standard takes

208 precedence.

209 This document supplements IEC 60079-11, the requirements of which apply to apparatus

210 used in intrinsically safe systems.

211 The installation requirements of Group II or Group III systems designed in accordance with

212 this standard are specified in IEC 60079-14.

213 NOTE 2 Group I installation requirements are presently not provided in IEC 60079-14. Installation requirements

214 for Group I are being considered.
215 2 Normative references

216 The following referenced documents are indispensable for the application of this document.

217 For dated references, only the edition cited applies. For undated references, the latest edition

218 of the referenced document (including any amendments) applies.

219 IEC 60079-0, Explosive atmospheres – Part 0: Equipment – General requirements

220 IEC 60079-11, Explosive atmospheres – Part 11: Equipment protection by intrinsic safety “i”

221 IEC 60079-14, Explosive atmospheres – Part 14: Electrical installations design, selection

222 and erection

223 IEC 61158-2, Industrial communication networks − Fieldbus specifications – Part 2: Physical

224 layer specification and service definition
225 3 Terms and definitions

226 For the purposes of this document, the following terms and definitions, specific to intrinsically

227 safe systems, apply. They supplement the terms and definitions which are given in IEC

228 60079-0 and IEC 60079-11.

229 ISO and IEC maintain terminological databases for use in standardization at the following

230 addresses:
231 • IEC Electropedia: available at http://www.electropedia.org/
232 • ISO Online browsing platform: available at http://www.iso.org/obp
233 3.1
234 intrinsically safe system

235 assembly of interconnected items of apparatus, described in a descriptive system document,

236 in which the circuits or parts of circuits, intended to be used in an explosive atmosphere, are

237 intrinsically safe circuits
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238 3.2
239 multi-circuit cable
240 multi-core cable containing more than one intrinsically safe circuit
241 3.3
242 descriptive system document

243 document in which the items of apparatus, their intrinsic safety parameters and those of the

244 interconnecting wiring are specified
245 3.4
246 total cable capacitance
247 C

248 total capacitance of the interconnecting cable that can be connected into an intrinsically safe

249 circuit
250 3.5
251 total cable inductance
252 L

253 total inductance of the interconnecting cable that can be connected into an intrinsically safe

254 circuit
255 3.6
256 cable inductance to resistance ratio
257 L /R
c c

258 value of the ratio inductance (L ) to resistance (R ) of the interconnecting cable connected

c c
259 into an intrinsically safe circuit
260 3.7
261 linear power source

262 power source from which the available output current is determined by a resistor; the output

263 voltage decreases linearly as the output current increases
264 3.8
265 non-linear power source

266 power source where the output voltage and output current have a non-linear relationship

267 Note 1 to entry: For example, a supply with a constant voltage output that can reach a constant current limit

268 controlled by semiconductors
269 3.9
270 FISCO
271 Fieldbus Intrinsically Safe Concept

272 intrinsically safe system architecture which is bus-powered and designed in accordance with

273 IEC 61558-2, Industrial communication networks − Fieldbus specifications – Part 2: Physical

274 layer specification and service definition
275 4 Descriptive system document

276 A descriptive system document shall be created for all intrinsically safe systems. The

277 descriptive system docume
...