IEC 61892-2:2012

IEC 61892-2


®


Edition 2.0 2012-03



INTERNATIONAL



STANDARD






Mobile and fixed offshore units – Electrical installations –
Part 2: System design


IEC 61892-2:2012(E)

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IEC 61892-2



®



Edition 2.0 2012-03







INTERNATIONAL





STANDARD






















Mobile and fixed offshore units – Electrical installations –

Part 2: System design




























INTERNATIONAL

ELECTROTECHNICAL

COMMISSION

PRICE CODE
XC


ICS 47.020.60 ISBN 978-2-88912-993-5



  Warning! Make sure that you obtained this publication from an authorized distributor.


® Registered trademark of the International Electrotechnical Commission

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– 2 – 61892-2 © IEC:2012(E)



CONTENTS


FOREWORD . 7

INTRODUCTION . 9

1 Scope . 10

2 Normative references . 10

3 Terms and definitions . 11


4 Sources of electrical power . 16

4.1 General . 16
4.2 Main source of electrical power . 17
4.3 Emergency source of electrical power . 18
4.4 Starting arrangements for emergency generators . 21
4.5 Additional requirements for periodically unattended machinery spaces . 22
4.6 General requirements for renewable sources of electrical power . 22
4.6.1 Photovoltaic system . 22
4.6.2 Eolic system . 23
5 System earthing . 23
5.1 General . 23
5.2 General requirements . 23
5.3 Neutral earthing methods . 24
5.4 Neutral earthing for systems up to and including 1 000 V a.c. . 24
5.5 Neutral earthing for systems above 1 000 V . 25
5.6 Generators operated in parallel with source transformers . 25
5.7 Earthing resistors, connection to hull/structure . 25
6 Distribution systems . 27
6.1 DC distribution systems . 27
6.1.1 Types of distribution systems . 27
6.1.2 TN d.c. systems . 28
6.1.3 IT d.c. systems . 31
6.1.4 DC voltages . 31
6.2 AC distribution systems . 32
6.2.1 Primary a.c. distribution systems . 32
6.2.2 Secondary a.c. distribution systems . 32

6.2.3 TN a.c. systems . 32
6.2.4 IT a.c. systems . 34
6.2.5 AC voltages and frequencies . 34
6.2.6 Control voltage . 36
7 Distribution system requirements . 37
7.1 Earthed distribution systems . 37
7.2 Methods of distribution . 37
7.3 Balance of loads . 37
7.3.1 Balance of load on three-wire d.c. systems . 37
7.3.2 Balance of loads in three- or four-wire a.c. systems . 37
7.4 Final circuits . 37
7.4.1 General . 37
7.4.2 Final circuits for lighting . 37
7.4.3 Final circuit for lighting in accommodation spaces . 38

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61892-2 © IEC:2012(E) – 3 –


7.4.4 Final circuits in offices and workshops . 38

7.4.5 Final circuits for heating . 38

7.5 Control circuits . 38

7.5.1 Supply systems and nominal voltages . 38

7.5.2 Circuit design . 38

7.5.3 Motor control . 38

7.5.4 Protection . 38

7.5.5 Arrangement of circuits . 39

7.6 Socket-outlets . 39

7.7 Shore connections for mobile units . 39

7.8 Motor circuits . 39
7.8.1 Starting of motors . 39
7.8.2 Means of disconnection . 40
7.8.3 Starters remote from motors . 40
7.8.4 Master-starter system . 40
8 Diversity (demand) factors . 40
8.1 Final circuits . 40
8.2 Circuits other than final circuits . 40
8.3 Application of diversity (demand) factors . 40
8.4 Motive power circuits – General . 40
9 System study and calculations . 41
9.1 General . 41
9.2 Electrical load study . 42
9.3 Load flow calculations . 42
9.4 Short-circuit calculations . 43
9.5 Protection and discrimination study . 44
9.6 Power system dynamic calculations. 45
9.7 Calculation of harmonic currents and voltages. 47
10 Protection . 47
10.1 General . 47
10.2 Characteristic and choice of protective devices with reference to short-circuit
rating . 48
10.2.1 General . 48
10.2.2 Protective devices . 48
10.2.3 Backup protection . 48

10.2.4 Rated short-circuit breaking capacity . 49
10.2.5 Rated short-circuit making capacity . 49
10.2.6 Co-ordinated choice of protective devices with regard to
discrimination requirements . 49
10.3 Choice of protective devices with reference to overload . 49
10.3.1 Mechanical switching devices . 49
10.3.2 Fuses for overload protection . 49
10.4 Choice of protective devices with regard to their application . 50
10.4.1 General . 50
10.4.2 Generator protection . 50
10.4.3 Protection of essential services . 51
10.4.4 Protection of transformers . 51
10.4.5 Circuit protection . 51
10.4.6 Motor protection . 51

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10.4.7 Protection of lighting circuits . 52

10.4.8 Protection of power from external sources . 52

10.4.9 Secondary cells and battery protection . 52

10.4.10 Protection of meters, pilot lamps and control circuits . 52

10.4.11 Protection of static or solid state devices . 52

10.4.12 Protection for heat tracing systems . 53

10.5 Undervoltage protection . 53

10.5.1 Generators . 53

10.5.2 AC and DC motors . 53

10.6 Overvoltage protection . 53

10.6.1 General . 53
10.6.2 AC machines . 53
10.6.3 DC networks . 54
11 Lighting . 54
11.1 General . 54
11.2 General lighting system . 54
11.3 Emergency lighting system . 55
11.4 Escape lighting system . 56
11.5 Lighting circuits in machinery spaces, accommodation spaces, open deck
spaces, etc. . 57
11.6 Navigation and obstruction signals and lights . 58
11.7 Luminaires . 58
11.7.1 Discharge lamp luminaires of voltages above 250 V . 58
11.7.2 Searchlights . 58
12 Control and instrumentation . 58
12.1 Safeguarding . 58
12.2 Supply arrangement . 58
12.3 Dependability . 58
12.4 Safety . 59
12.5 Segregation . 59
12.6 Performance . 59
12.7 Integration . 59
12.8 Development activities . 59
12.9 Electromagnetic compatibility . 59
12.10 Design . 59

12.10.1 Environmental and supply conditions . 59
12.10.2 Circuit design . 60
12.10.3 Monitoring equipment . 60
12.10.4 Time delays . 60
12.10.5 Closed circuits . 60
12.10.6 Earth faults . 60
12.11 Installation and ergonomics . 60
12.11.1 General . 60
12.11.2 Remote controls . 60
12.12 Specific installations . 61
12.12.1 Safety critical systems . 61
12.12.2 Fire and gas protection control installations and other control
systems . 62
12.13 Automatic control installations for electrical power supply . 63

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61892-2 © IEC:2012(E) – 5 –


12.13.1 General . 63

12.13.2 Automatic starting . 63

12.13.3 Automatic disconnection . 64

12.13.4 Automatic starting installations for electrical motor-driven
auxiliaries . 64

12.13.5 Manual control . 65

12.14 Machinery control installations . 65

12.14.1 General . 65

12.14.2 General requirement . 65

12.15 Public address and general alarm systems . 65

12.15.1 Audibility . 65
12.15.2 Operation . 65
12.15.3 Emergency broadcast . 65
12.15.4 Minimum sound level . 65
12.15.5 Fault tolerance . 65
12.15.6 Redundancy . 66
12.15.7 Segregation . 66
12.15.8 Power supplies . 66
12.15.9 Cabling . 66
12.16 Computer-based systems . 66
12.16.1 General . 66
12.16.2 System integration . 66
12.16.3 Power supply . 66
12.16.4 Data communication links . 67
12.16.5 Alarm, control and safety functions . 67
12.17 Software . 68
12.17.1 General . 68
12.17.2 Configuration . 68
12.17.3 Documentation . 69
12.18 Tests . 70
12.18.1 General . 70
12.18.2 Hardware . 70
12.18.3 Software . 71
12.18.4 System testing . 71
12.19 Documentation . 71

12.19.1 Apparatus description . 71
12.19.2 Circuit diagrams. 71
13 Degrees of protection by enclosures . 72
Annex A (informative) Variable a.c. speed drives . 76
Bibliography . 77

Figure 1 – Continuity of supply/continuity of service . 16
Figure 2 – TN-S d.c. system . 28
Figure 3 – TN-C d.c. system . 29
Figure 4 – TN-C-S d.c. system . 30
Figure 5 – IT d.c. system . 31
Figure 6 – TN-S a.c. system . 33
Figure 7 – TN-C-S a.c. system . 33

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Figure 8 – TN-C a.c. system . 34

Figure 9 – IT a.c. system . 34


Figure A.1 – Typical a.c. drilling system . 76



Table 1 – Recommended maximum earth fault currents . 25

Table 2 – Summary of principal features of the neutral earthing methods . 26


Table 3 – Voltages for d.c. systems . 32

Table 4 – AC systems having a nominal voltage between 100 V and 1 000 V inclusive

and related equipment . 35

Table 5 – AC three-phase systems having a nominal voltage above 1 kV and not
a
exceeding 35 kV and related equipment . 36
Table 6 – General lighting illumination levels . 55
Table 7 – Recommended measuring points for measuring illumination in an area . 55
Table 8 – Escape lighting illumination levels . 56
Table 9 – Minimum requirements for the degree of protection for mobile and fixed
offshore units (Degree of protection as defined in IEC 61892-1) . 73

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61892-2 © IEC:2012(E) – 7 –



INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________




MOBILE AND FIXED OFFSHORE UNITS –

ELECTRICAL INSTALLATIONS –



Part 2: System design



FOREWORD
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