Installation Recommendations

Transcription

1 Installation Recommendations Cable pulling recommendations The process of pulling electrical cables on board marine vessels is a relatively standard procedure. Nevertheless, NEXANS would suggest the following rules should be respected to avoid any degradation of cables arising as a result of the pulling process. - Prior to commencing actual pulling care must be taken to ensure that the pulling equipment attached directly to the cable is tightly fitted over the complete cable and not only to one element such as the outer sheath, braiding or conductors. - The maximum pulling tension exerted on the cable must not exceed 0 N/mm² (per square millimetre of copper) whether the cable is being pulled manually or with a winch or other mechanical equipment. - If the cable section is pre-cut before pulling, the cable has to be correctly coiled to avoid any over-twist. Precut cable sections in waiting position before final installation must be protected. - All cable runs must be smooth and clean or covered with a complementary protection, to prevent any damage on the protective covering of the cable. - In installations where several cables are to be installled together, the use of talcum is recommended to reduce friction and abrasion between the outer sheaths and to ease the pulling process by allowing the cables to slide more freely against each other. - Where cables being pulled come into contact perpendiculary with cables already installed, it is strongly advised to protect the latter to avoid abrasive damage. - In order to avoid the effects of unwanted electromagnetic interference (EMI) as far as possible, Nexans has distinguished the main cable circuit types with outer sheaths of different colours: - Red: Medium Voltage cables - Black: Power cables 0.6/1 kv, Control cables 10/20 V and 0.6/1 kv - Blue: Cables for intrinsic circuit, 10/20 V - 0.6/1 kv - Orange: Instrumentation, Telephone cables 10/20 V It is recommended that, where possible, only cables of the same colour be installed in cable runs and cable trays. In order to reduce the installation time, NEXANS has designed a cable range which offers: - safety for people connecting the cables, due to the easy stripping of cables; - low volume and weight; - easy and fast drawing due to the very good friction coefficient of polyolefin outer sheath leading to important cost savings for laying and connection of the cables. It is always necessary, before unrolling, to store the cables for at least twelve hours in warmed premises (about +10 C) However, a longer period might be necessary for the largest drums. The cables can be pulled with a minimum outer temperature of minus 1 C but with a slow and regular speed (about 20m/min) without shock. Bending radii for cables rated up to 1.8/3 (3.6) kv Minimum internal bending radius Cables Type Unarmoured Cables Armoured Cables Cables with circular copper conductors: D = < 2 mm 4D 6D D > 2 mm 6D 6D Cables with sector shaped copper conductors for any overall diameter of cable: 8D 8D Bending radii for cables rated at to 3.6/6 (7.2) kv and above Cables Type Minimum internal bending radius Single core cables 12D 3 Cores cables 9D for any overall diameter of cable 89

2 Cable type Bending radius Temperatur Tension Fixed installation Fixed Installation* Maximum x D C C MPRX (All types) D=<2mm 4-30 to to +0 0 N/mm² D> 2mm 6-30 to to +0 0 N/mm² MPRXCX (All types) 6-30 to to +0 0 N/mm² BFOU 0,6/1KV 6-30 to +7-1 to +0 0 N/mm² MEPRX 6,6/12KV Single core to to +0 0 N/mm² Multicore 9-30 to to +0 0 N/mm² LYONOTOX 40/70V 6-20 to to +0 0 N/mm² Silicone SIHGLCSI to to N TX(I) 10/20V 6-30 to to +0 0 N/mm² TCX(C ) 10/20V 6-30 to to +0 0 N/mm² TCX(I) 10/20V 6-30 to to +0 0 N/mm² TCX( C) /20V 6-30 to to +0 0 N/mm² BFOU(I) 20V 6-30 to +7-1 to +0 0 N/mm² MX 4-30 to to +0 0 N/mm² UX 0,6/1KV 4-30 to +7-1 to +0 0 N/mm² RADOX 12 D=< 12mm 3-40 to to +0 0 N/mm² S-FTP Cat e -20 to to N RE-V2Y(ST+Ce)H PIMF 8-30 to to N PROFIBUS to to N Fibre optic cable 1-20 to to N TWINAX RG to to N COAX RG to to N COAX RG214-2 to to N * It is always necessary, before unrolling, to store the cable for at least twelve hours in warmed premises (about +10 C), however, a longer periode might be necessary for larges drums. Minimum bending radius figures to be doubled during laying operations. 90

3 Cross sectional area of neutral conductor The neutral conductor must have an adequate cross section to carry the fault current resulting from a single phase short circuit and to cause the protection devices to operate within 1 second. For cross section of 16 mm² or less however, the cross section of the neutral conductor must not be less than the phase cross section. For larger cross sections, the neutral cross section must be at least 0% of the cross section of the conductor of the phase conductor but not less than 16 mm². Installation of single core cable in A.C. Recommended method for cable installation on horizontal or vertical supports is shown in the table below. The references L1, L2, L3 indicate the location of the respective phase conductor Number of conductors per phase Recommended cable positionning 2 L1 L2 L3 L3 L2 L1 L1 L2 L3 3 L2 L3 L1 L3 L1 L2 L3 L1 L2 L3 4 L2 L3 L1 L2 L1 L2 L3 L1 L1 L2 L3 L1 L2 L2 L3 L1 L2 L3 L3 L1 L2 L3 L1 L1 L2 L3 L1 L2 L3 6 L2 L3 L1 L2 L3 L1 L3 L1 L2 L3 L1 L2 L1 L2 L3 L1 L2 L3 L1 7 L2 L3 L1 L2 L3 L1 L2 L3 L1 L2 L3 L1 L2 L3 L1 L2 L3 L1 L2 L3 L1 L2 8 L2 L3 L1 L2 L3 L1 L2 L3 L3 L1 L2 L3 L1 L2 L3 L1 91

4 Permissible current rating (A) at ambient temperature of 4 C Ambient temperature of 4 C IEC Temperature class 90 C Cross section (mm²) 1 core cable 2 core cable 3-4 core cable Current ratings in Amperes, for ambient temperature of 4 C, according to IEC standard. Correction factors for air ambiant temperature IEC Max. conductor temp. Correction factors for various air ambiant temperatures 3 C 40 C 4 C 0 C C 60 C 6 C 70 C 7 C 80 C 8 C 70 C C C C C C Correction factors for cables grouping IEC The current rating values may be considered applicable, without correction factor, for cables bunched together on cable trays, in cable conduit, pipe or trunking, unless more than 6 cables, which may be expected to operate simultaneously at their full rated current, are laid close together in a cable bunch in such a way that there is an absence of free air circulation around them. In this case, a correction factor of 0.8 should be applied on current rating value. 92

5 RADOX Correction factor for higher ambient temperature Ambient temperatur Radox C C C C C C C C C C C 0 Correction factors for wire bundles according to IEC Number of cores Correction factor Number of cores Correction factor

6 Resistance of copper conductors and design of the conductors cores according to IEC for classes 2 and Cross section (mm²) Number of wires Class 2 Class Maximum Resistance 20 C Ohm/km D.C. Max. Diameter of wires in conductor Maximum Resistance 20 C Ohm/km D.C. Bare copper Tinned copper Bare copper Tinned copper Rt = R20 x L Kt x 1000 Rt = Resistance in ohms at a temperature t in C for a length in meters R20 = Resistance in ohms at 20 C for a length of 1 km L = Length in meters Kt = Temperature correction factor for a temperature t in C Resistance of copper conductors and design of the conductors cores according to - IEC for 0.3 mm² and - IEC from 0. to 2. mm² Cross section (mm²) Number of wires Class 2 Maximum Resistance 20 C Ohm/km D.C. Bare copper Tinned copper

7 Temperature correction factors according to IEC Temperature correction factors Temperature ( C) Kt

8 Short circuit rating The short circuit rating calculation is based on the maximum conductor temperature depending of the type of insulation compound and the final temperature after short circuit. The short circuit current is calculated from the following formula: It = A t A It t = Short circuit current rating during 1 sec. (A) = Short circuit current for a given period (A) = Duration of the short circuit (sec) Cross-section mm² Short circuit current rating during 1 sec (A) XLPE insulation compound withstands short circuit temperature up to 20 C. Parallel connection of cables Cables can be installed in parallel if they have: equal cross section conductor cross section 10 mm² or more equal lengths the same type and have a common protection the same class of temperature Parallel connected single core cables are to be laid together and in such way that necessary ventilation is provided. Parallel connection of flexible cables is not permitted. The total current rating must not be higher than the sum of the current rating for individual cables. 96

9 Communication and instrumentation cables Cross-section (mm²) Number of pairs Loop resistance (ohm/km - D.C. 20 C) Bare copper Tinned copper Capacitance Individual screen (nf/km) Collective screen (nf/km) 2p p p p p p Loop Inductance (mh/km) Screening efficiency: NEXANS, has studied screening efficiency of our cable range TX and TCX. This study shows the transfer impedance (Zt) related to frequency (khz). The results are as follows: - TX (C): (Unarmoured, collective screen) Electromagnetic screening of the TX (C) cable is simple and shows a medium protection in polluted electromagnetic surroundings. - TX (I): (Unarmoured, individual screen) TX (I) is an excellent compromise between TX (C) and TCX (C) cables. - TCX (C): (Armoured, collective screen) The TCX (C) cable shows a low transfer impedance in low frequency and an effective screening in high frequency. TCX (C) would be recommended in polluted electromagnetic surroundings. - TCX (I): (Armoured, individual screen) This cable type shows an excellent protection in both low and high frequency runs. 97

10 Transfer impedance Value (Zt) according to the frequency (F) Zt (mω/m) F (khz) This diagram is based on a 7 pairs cable Recommendations Table Level of electromagnetic pollution Cable type Low Frequency High Frequency High Medium Low TCX (I) Excellent Excellent x x x TCX (C) Excellent Good x x x TX (I) Good Good - x x TX (C) Medium x 98