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发表于 2017-9-23 16:20
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来自: 中国江苏苏州
一般情况下,电缆的铠装层主要作用是防碾压的,增强电缆的强度;但是特殊情况下,比如说短路的时候,铠装层在作为保护层的基础上还具有导电性,在这个时候就可以充当回路的角色!在一定程度上防止了重大事故的产生。
船上一般电制属于三相三线制的IT系统,电源侧和用电设备侧电机外壳做好接地保护,3芯线作为电机动力线以满足要求
请看一下下面LR的规范
2.1.1 The following systems of supply and distribution are acceptable provided that adequate safeguards are taken to minimize shock hazard to divers:
d.c., two-wire, insulated from earth IT System;
d.c., two-wire earthed system TN-S system;
a.c., single-phase, two-wire, insulated from earth IT system;
a.c., three-phase,
Three-wire insulated from earth IT system;
Four-wire with neutral solidly earthed but without hull return. TN-S system.
Note Refer to IMCA D 045 “Code of Practice for The Safe Use of Electricity Under Water” for additional guidance.
2.1.2 Earthing systems complying with IEC 61892-2:2012, Mobile and fixed offshore units – Electrical installations – Part 2: System design, section 5 and IEC 60092-502:1999, Electrical installations in ships – Part 502: Tankers – Special features, section 5 are acceptable. While both insulated and earthed distribution systems (TN-S) are permitted, systems which may result in the presence of electrical currents within the hull or unit structure return (TN-C and TN-C-S) are not permitted.
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