Clasification Society Rulefinder 2016 - Version 9.25
Clasification Society Rules and Regulations - Rules and Regulations for the Classification of Offshore Units, January 2016 - Part 6 CONTROL AND ELECTRICAL ENGINEERING - Chapter 2 Electrical Engineering - Section 6 System design – Protection |
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![]() Section 6 System design – Protection6.1 General6.1.1 The general requirements for protection are given in IEC 61892-2:2012, Mobile and fixed offshore units – Electrical installations – Part 2: System design, Section 10 and Pt 6, Ch 2, 6.1 General of the Rules for Ships, which are to be complied with. 6.2 Protection against short-circuit6.2.1 The general requirements for protection against short-circuit are given in Pt 6, Ch 2, 6.2 Protection against short-circuit of the Rules for Ships, which are to be complied with. Additions or amendments to these requirements are given in the following paragraph(s) of this sub-Section. 6.2.2 The rated short-circuit making and breaking capacity of every protective device is to be adequate for the prospective fault level at its point of installation; the requirements for circuit-breakers and fuses are detailed in Pt 6, Ch 2, 6.5 Circuit-breakers and Pt 6, Ch 2, 6.6 Fuses respectively. 6.3 Protection against overload6.3.1 The general requirements for protection against overload are given in Pt 6, Ch 2, 6.3 Protection against overload of the Rules for Ships, which are to be complied with. 6.4 Protection against earth faults6.4.1 The general requirements for protection against short-circuit are given in Pt 6, Ch 2, 6.4 Protection against earth faults of the Rules for Ships, which are to be complied with. For systems of 15 kV a.c. and above, see also Pt 6, Ch 2, 5.6 High voltage distribution systems. Additions or amendments to these requirements are given in the following paragraph(s) of this sub-Section. 6.4.2 Where any circuit, other than an intrinsically safe circuit, passes into or through any Zone 0 area, the circuit is to be disconnected automatically and/or is to be prevented from being energised in the event of an abnormally low level of insulation resistance and/or high level of leakage current. 6.4.3 Where a circuit passes into any zone 0 area, the protective systems shall be arranged so that manual intervention is necessary for the reconnection of the circuit after disconnection as the result of a short-circuit, overload or earth-fault condition. 6.5 Circuit-breakers6.5.1 The requirements for circuit-breakers are given in Pt 6, Ch 2, 6.5 Circuit-breakers of the Rules for Ships, which are to be complied with. 6.6 Fuses6.6.1 The requirements for fuses are given in Pt 6, Ch 2, 6.6 Fuses of the Rules for Ships, which are to be complied with. Additions or amendments to these requirements are given in the following paragraph(s) of this sub-Section. 6.6.2 The use of fuses for overload protection is permitted up to 320A, provided they have suitable characteristics, but the use of circuit-breakers or similar devices is recommended above 200A. For high voltage a.c. systems (above 1 kV a.c.), the use of fuses for overload protection is not acceptable. Is Limiters The use of Is Limiters is permitted in situations where circuit-breakers cannot provide any protection against unduly high peak short-circuit currents, as circuit-breakers are too slow. NOTE Only the Is Limiter is capable of detecting and limiting a short-circuit current at the first rise, i.e. in less than 1 ms. The maximum instantaneous current occurring remains well below the level of the peak short-circuit current. 6.7 Circuit-breakers requiring back-up by fuse or other device6.7.1 The requirements for circuit-breakers requiring back-up by fuse or other devices are given in Pt 6, Ch 2, 6.7 Circuit-breakers requiring back-up by fuse or other device of the Rules for Ships and IEC 61892-2:2012, Mobile and fixed offshore units – Electrical installations –- Part 2: System design, Section 10.2.3, which are to be complied with. 6.8 Protection of generators6.8.1 The requirements for the protection of generators are given in Pt 6, Ch 2, 6.8 Protection of generators of the Rules for Ships and IEC 61892-2:2012, Mobile and fixed offshore units – Electrical installations – Part 2: System design, Section 10.4.2, which are to be complied with. Additions or amendments to these requirements are given in the following paragraph(s) of this sub-Section. 6.8.2 Generators not arranged to run in parallel are to be provided with a circuit-breaker arranged to open simultaneously, in the event of short-circuit, overload or under-voltage, all insulated poles. In the case of generators rated at less than 50 kW, a multipole linked switch with a fuse, complying with Pt 6, Ch 2, 5.3 Isolation and switching 5.3.2, in each insulated pole will be acceptable. 6.8.3 Where generators are intended to operate in parallel:
6.9 Load management6.9.1 The requirements for load management are given in IEC 61892-5:2010, Mobile and fixed offshore units – Electrical installations – Part 5: Mobile units, Section 9.9.2, IEC 60092-504, Electrical installations in ships – Part 504: Special features – Control and instrumentation and Pt 6, Ch 2, 6.9 Load management of the Rules for Ships, which are to be complied with where applicable. Additions or amendments to these requirements are given in the following paragraph(s) of this sub-Section. 6.9.2 Arrangements are to be made to disconnect automatically, after an
appropriate time delay, circuits of the categories noted below, when the generator(s)
is/are overloaded, sufficient to ensure the connected generating set(s) is/are not
overloaded:
6.10 Feeder circuits6.10.1 The requirements for feeder circuits are given in IEC 61892-2:2012, Mobile and fixed offshore units – Electrical installations – Part 2: System design, Section 10.4.5 and Pt 6, Ch 2, 6.10 Feeder circuits of the Rules for Ships, which are to be complied with. 6.11 Motor circuits6.11.1 The requirements for motor circuits are given in IEC 61892-2:2012, Mobile and fixed offshore units – Electrical installations – Part 2: System design, Section 10.4.6 and Pt 6, Ch 2, 6.11 Motor circuits of the Rules for Ships, which are to be complied with. 6.12 Protection of transformers6.12.1 The requirements for protection of transformers are given in IEC 61892-2:2012, Mobile and fixed offshore units – Electrical installations – Part 2: System design, Section 10.4.4 and Pt 6, Ch 2, 6.12 Protection of transformers of the Rules for Ships, which are to be complied with where applicable. 6.13 Harmonic filters6.13.1 The requirements for protection of transformers are given in Pt 6, Ch 2, 6.13 Harmonic filters of the Rules for Ships, which are to be complied with. |
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