Offshore Transformer Platform Technical Standard Energinet.dk HV, MV, LV and Signal Cables and Cable Routing ETS - 03 Rev. 1 Acadre doc. 44858-09
Revision survey Chpt. Description Revision Date Resp. - 1st edition and revision 1 12-10-09 SGH Appendix no. and description Revision None ETS - 03 Rev. 1
Table of contents 1. Scope 1 2. References 1 2.1 Statutory Regulations 1 2.2 Codes and Standards 1 3. Definitions 2 3.1 Definitions 2 4. Technical Requirements 3 4.1 General 3 4.1.1 Requirements 3 4.1.2 Cable segregation 3 4.1.3 Cable ladders and trays 3 4.1.4 Cable installation 4 4.1.5 Cable pulling force and bending radius 4 4.1.6 Cable cleating and strapping 4 4.1.7 Cable splicing 5 4.1.8 Temporary cables 5 4.1.9 Cable gland selection 5 4.1.10 Termination 5 4.1.11 Spare conductors 6 4.1.12 Marking 6 4.2 HV cables 7 4.2.1 Specification 7 4.2.2 Selection 7 4.3 MV cables 8 4.3.1 Specification 8 4.3.2 Selection 8 4.4 LV cables 10 4.4.1 Specification Power supply cable 10 4.4.2 Selection 11 4.5 Signal cables 11 4.5.1 Specification for category 5e cables 12 4.5.2 Specification for coax cables 12 4.5.3 Specification for optical fibre cables 12 4.5.4 Specification for twisted pair cables 12 4.5.5 Selection 13 5. Certificates / Data books 13 6. Appendix 13 ETS - 03 Rev. 1
1. Scope This technical standard specifies the basic requirements for the High, Medium and Low Voltage and signal cables to be used on an offshore located transformer platform for offshore wind farms established in the Danish offshore sector. Further the installation, segregation and support of cables is described in general terms. 2. References 2.1 Statutory Regulations Energi Styrelsen RETNINGSLINIER FOR DESIGN AF FASTE OFSHOREANLÆG Direktiv 2006/95/EF Lavspændingsdirektivet BEK nr. 27 af 10/01/2007 Bekendtgørelse om radio-og teleterminaludstyr og elektromagnetiske forhold (EMC Direktiv 2004/108/EF) 2.2 Codes and Standards ANSI/TIA 568B Communications cabling standard EN 50167 Sectional specification for horizontal floor wiring cables with a common overall screen for use in digital communication EN 50173 Information technology Generic cabling systems IEC 11801 Information technology Generic cabling for customer premises IEC 60038 IEC standard voltages IEC 60092 Electrical installations in ships IEC 60183 Guide to the selection of high-voltage cables IEC 60287 Electric cables Calculating of the current rating IEC 60228 Conductors of insulated cables IEC 60331 Tests for electrical cables under fire conditions IEC 60332 Tests on electric and optical fibre cables under fire conditions IEC 60364 Low-voltage electrical installations IEC 60724 Short-circuit temperature limits of electric cables with rated voltages from of 1 kv (U m =1,2 kv) and up to 3 kv (U m =3,6 kv) IEC 60754 Test on gasses evolved during combustion of electric cables ETS - 03 Rev. 1 1
IEC 60793 Optical fibres IEC 60794 Optical fibre cables IEC 60840 Power cables with extruded insulation and their accessories for rated voltages above 30 kv (U m = 36 kv) up to 150 kv (U m =170 kv) Test methods and requirements IEC 60885 Electrical test methods for electrical cables IEC 60949 Calculation of thermally permissible short-circuit currents, taking into account non-adiabatic heating effects IEC 60986 Short-circuit temperature limits of electric cables with rated voltages from of 6 kv (U m =7,2 kv) and up to 30 kv (U m =36 kv) IEC 61034 Measurement of smoke density of cables burning under IEC 61034 Measurement of smoke density of cables burning under defined conditions IEC 61443 Short-circuit temperature limits of electric cables with rated voltages above 30 kv (U m =36 kv) IEC 61892 Mobile and fixed offshore units Electrical installations IEC/TR 62095 Electric cables Calculation for current ratings Finite element method 3. Definitions 3.1 Definitions Shall: Verbal form used to indicate requirements to be strictly followed in order to conform to the standard and from which no deviation is permitted, unless accepted by all parties. Should: Verbal form used to indicate that among several possibilities one is recommended as particularly suitable, without mentioning or excluding others, or that a certain course of action is preferred but not necessarily required. May: Verbal form used to indicate a course of action permissible within the limits of the standard. Can: Verbal form used for statements of possibility and capability, whether material, physical or casual ETS - 03 Rev. 1 2
4. Technical Requirements 4.1 General 4.1.1 Requirements Cables shall comply with the relevant standards applicable for the particular use of the cable. All cables used shall be minimum flame retardant (IEC 60332). Fire resistant cables shall be used for essential services such as fire detection and alarming and emergency lighting. Generally all cables should have a tinned copper braid armouring and an outer sheath which is UV resistant. Cables without armour may be used in staff rooms and in control equipment rooms. 4.1.2 Cable segregation Signal cables shall be routed separate from HV, MV and LV cables. Minimum distance should be 600mm to HV and MV cables and 300mm to LV cables. Instrument cables and communication cables can generally be routed together. Signal cables crossing at a right angel with LV cables is acceptable without further segregation. High voltage cables shall in the full length be separated from medium voltage and low voltage cables by at least 300 mm unless mechanically separated by earthed metal partitions or pipes. Medium voltage cables shall in the full length be separated from High voltage and low voltage cables by at least 300 mm unless mechanically separated by earthed metal partitions or pipes. Considerations must be taken during installations of cables entering and leaving equipment like power transformers, crane etc. related to the requirements of segregation. 4.1.3 Cable ladders and trays All cables should be routed on cable ladders, cable trays and/or J-tubes. Outdoor cable ladders and trays shall be fibre reinforced plastic. Indoor cable ladders and trays may be galvanized steel. Conduits may be used for special mechanical protection of single field routed cables for shorter distances. ETS - 03 Rev. 1 3
The cable ladders and trays should not be filled so the height of their side rail is exceeded. Further the ladders and trays should not be filled beyond 50% of their total capacity. Redundant cable systems shall as far as possible be routed separately. MV cables should be routed and grouped depending of the chosen current carrying capacity estimation method, according to section 4.3.2. 4.1.4 Cable installation Access for maintenance and an orderly layout shall be ensured when cabling below raised floor is performed. Once a cable has been cut, a protective cap/sealing shall be applied on the end, when being exposed to humid atmosphere. All cable entries to equipment located outdoor and in deluge covered areas should be from below. Top entry is not allowed and side entry shall be provided with additional protection against ingress of moisture. Sufficient cable spare length shall be provided for equipment which needs future adjustments (floodlights, loudspeakers, TV cameras etc.) or where equipment have to be dismounted for maintenance and calibration without disconnecting the cable. Single core cables for three-phase AC shall run in trefoil formation. The braided armour shall be earthed in one end only. Single core cables shall not be installed separately through openings surrounded by magnetic materials. Non-magnetic stainless steel separation walls and stay plates shall be used in cable transits used for single core cables. 4.1.5 Cable pulling force and bending radius The maximum pulling force and minimum permissible bending radius specified by supplier shall be adhered to. 4.1.6 Cable cleating and strapping All cables shall be fixed properly to the cable support systems. Plastic coated stainless steel straps shall be used for all cable runs outside and in non ventilated areas. UV resistant nylon straps may be used in indoor and ventilated locations. The Plastic coated stainless steel straps shall be used for vertical runs and for horizontal runs in the vertical plane both indoor and outdoor. For strapping of fibreoptical and coaxial cables, supplier guidelines shall be adhered to. ETS - 03 Rev. 1 4
The distance between cable straps shall not exceed: 600mm for horizontal runs 300mm for vertical runs and for horizontal runs in the vertical plane Ten times the cable outer diameter from cable entry to the first strap Single core power cables for three-phase AC shall be fixed with trefoil cable cleats which shall be approved for the potential short circuit stress. The cleats shall outdoors, in naturally ventilated areas and deluge covered areas be made of stainless steel. The distance between trefoil cleats shall be as specified by the cable manufacturer based on the calculated short circuit level. The distance shall be selected such that the cable will not be damaged by a possible short circuit. Normal distance is 300mm, and on every step on bends and risers. 4.1.7 Cable splicing Cable splicing should be avoided. If splicing seems unavoidable it shall be agreed with Energinet.dk for the installation in question. 4.1.8 Temporary cables Temporary cables routed on permanent cable support systems shall be installed such that they will not obstruct permanent installations and are easy to remove. 4.1.9 Cable gland selection Cable glands, bushings, modular multi cable transits (MCT) or fittings for screwed conduits, shall be provided according to the way in which the cables enter the equipment or rooms. All entries shall maintain the degree of protection provided by the enclosure of the associated equipment or room. These shall apply to the whole range of cable dimensions specified by the manufacturer of the cable entries as suitable for use with those entries. Bottom entry is preferred for outdoor or deluge protected areas. Side entry is acceptable by use of drip nose installation for the cable in question. Types, maximum numbers and positions of Cable glands and blanking element entries for mounting in electrical apparatus for installation in explosive gas atmospheres shall be specified in a document submitted by the manufacturer. Shrouds and similar shall not be used on cable glands. 4.1.10 Termination All cable conductors shall be terminated by use of compression lugs or ferrules dependent upon the type of termination. The compression ferrule should be the type ETS - 03 Rev. 1 5
where the conductor strands are inserted through the whole ferrule and reach the bottom of the terminal. Support for cleating of cables when entering the panels should be provided. In switchboards and distribution boards adequate space shall be provided for the use of a clip-on ampere meter without causing undue stress on the cable conductors or connections. The braid armour and the screen shall be separated from each other as well as from the conductors, twisted and fitted as required. This shall be done without any reduction of the cross sectional area. Where the screen shall be left disconnected, which is applicable for field instruments, it shall be sealed and isolated with an isolating cap, allowing for insulation testing without any disconnecting. Only one conductor is allowed in each terminal of a terminal block/row for external connections. This is not related to terminals as integrated part of internal components (e.g. relays and contactors) of the equipment. Two conductors may in certain cases be used in one approved type ferrule connected to one terminal. 4.1.11 Spare conductors Spare conductors in instrument and telecom cables shall be terminated at the cabinet end and left floating at the field end. In cabinets all spare conductors shall be marked with terminal number and connected to terminals linked together by solid terminal links, which shall be connected to the relevant earth bar. Spare cores in instrument and telecom cables shall be connected to instrument earth in supply end only. If there are no spare terminals left in the cabinet, all spare conductors shall be covered with yellow/green sleeves and marked with relevant cable number and connected directly to the relevant earth bar. 4.1.12 Marking Numbering of cables shall be in accordance to the relevant document standard for the platform. Each cable shall be marked with indelible and non-corrosive cable markers indicating the cable number. The cable markers shall be clearly visible after cleating and strapping. Outdoors, in exposed- and deluge covered areas the cable markers should be made of stainless steel. Each cable shall have a cable marker located: ETS - 03 Rev. 1 6
At both sides of cable transits At both ends Outside cabinets with gland entries Inside cabinets with open entries 4.2 HV cables The designation High Voltage cables (HV cables) applies to submarine cables in a.c. three-phase systems having a nominal voltage above 35 kv and not exceeding 250 kv. The characteristics of the High Voltage range is specified according to IEC 60038, IEC standard voltages. 4.2.1 Specification The cable shall be three-core submarine cable with conductors made of copper. The insulation shall be dry extruded (XLPE) and longitudinally watertight. The sheat shall be made of lead or lead alloy. The cable shall be armoured with additional external corrosion protection capable of resisting forces acting on the cable during laying, embedding and possible repair. the armouring shall be applied in a continuous process. The cable shall have integrated optical fibres. 4.2.2 Selection A guidance for the selection of the cable conductor size, cable insulation level and cable construction is given according to IEC 60183. The lightning overvoltage of the cable must comply with the defined lightning protection zones and the effects of the installed lightning protection provisions. The choice of cables of appropriate cross-sectional area of conductors and current carrying capacity should be estimated according to information given in IEC 60287 and IEC/TR 62095. The selected cables and their insulated conductors shall be capable of withstanding the mechanical and thermal effects of the maximum short circuit current which can flow in any part of the circuit in which they are installed, taking into consideration not only the time/current characteristics of the circuit protective device, but also the peak value of the prospective short circuit current during the first half cycle. The cable short-circuit current withstand capability should be evaluated according to information given in IEC 61443 and IEC 60949. New and modified cable installations should be electrically tested as specified according to IEC 60840. ETS - 03 Rev. 1 7
4.3 MV cables The designation Medium Voltage cables (MV cables) applies to cables for fixed installations in all installations, whether permanent, temporary, transportable or hand-held, to a.c. three-phase systems having a nominal voltage above 1 kv and not exceeding 35 kv. The characteristics of the Medium Voltage range is specified according to IEC 60038, IEC standard voltages. 4.3.1 Specification Cables constructed in accordance with IEC 60092-350, IEC 60092-353, IEC 60092-354 and IEC 60092-376 are recommended for use as MV cables on fixed offshore units. 4.3.2 Selection The selection of the standard MV cable characteristics and type is based on the actual nominal system voltage and the demanded current carrying capacity. The choice of standard cables of appropriate voltage designations for particular systems depends upon the system voltage and the system earthing arrangements. A guidance for the selection of the cable conductor size, cable insulation level and cable construction is given according to IEC 60183. The rated voltage of any cable shall not be lower than the nominal voltage of the circuit for which it is used. To facilitate the choice of the cable, the values of U recommended for cables to be used in three-phase systems are listed in Table 1 in which systems are divided into the following three categories, A, B and C. Category A This category comprises those systems in which any phase conductor that comes in contact with earth or an earth conductor is automatically disconnected from the system. Category B This category comprises those systems that, under fault conditions are operated for a short time, not exceeding 8 hours on any occasion, with one phase earthed. Category C ETS - 03 Rev. 1 8
This category comprises all systems that do not fall into Categories A and B. Table 1 - Choice of cables for a.c. systems System voltage System Category Minimum rated voltage of cable U 0 /U Nominal voltage U kv Maximum sustained voltage, U m kv Unscreened kv Single-core or screened kv 3 3,6 A or B 1,8/3,0 1,8/3,0 3 3,6 C 3,6 / 6,0 6 7,2 A or B 3,6 / 6,0 6 7,2 C 6,0/10 10 12 A or B 6,0/10 10 12 C 8,7 / 15 15 17,5 A or B 8,7 / 15 15 17,5 C 12 /20 20 24 A or B 12 / 20 20 24 C 18 / 30 30 36 A or B 18 / 30 30 36 C NA 35 45 A or B NA 35 45 C NA The lightning overvoltage of the cable must comply with the defined lightning protection zones and the effects of the installed lightning protection provisions. The choice of standard cables of appropriate cross-sectional area of conductors and current carrying capacity should be estimated according to one of the following methods: - As described according to IEC 60287 - By calculation using a recognized method provided that the method is stated - According to IEC 61892-4, Annex A - According to IEC 61892-4, Annex B ETS - 03 Rev. 1 9
The estimated current carrying capacity should be modified with the adequate correction factors for different ambient air temperatures, according to IEC 61892-4, clause 4.3.4. The selected cables and their insulated conductors shall be capable of withstanding the mechanical and thermal effects of the maximum short circuit current which can flow in any part of the circuit in which they are installed, taking into consideration not only the time/current characteristics of the circuit protective device, but also the peak value of the prospective short circuit current during the first half cycle. The cable short-circuit current withstand capability should be evaluated according to information given in IEC 60724, IEC 60986 and IEC 60949. New and modified cable installations should be electrically tested as specified according to IEC 60885. 4.4 LV cables The following specified LV cables are intended for use in power supply to installations such as lighting, socket outlets, heaters, panels etc. Same cables shall be used whether AC or DC power. 4.4.1 Specification Power supply cable With the exception of single core cables, all power supply cables from switch gear to consumers shall have an integral dedicated green/yellow earth wire. Cable design for non-essential services should be: Conductor: Stranded bare copper Insulation: Cross linked polyethylene (XLPE) Inner covering: Halogen free filler (i.e. polyolefin) Armouring: Copper braid (Tinned) Outer sheath: Polyolefin Cable design for essential services should be: Conductor: Stranded tinned copper Insulation: Mica tape and XLPE ETS - 03 Rev. 1 10
Inner covering: Polyolefin Armouring: Tinned copper braid Outer sheath: Polyolefin 4.4.2 Selection LV cable types shall be selected to meet the requirements specified according to IEC 60092-352, Clause 3.1. All cables or insulated wiring shall meet the requirements for flame spread as specified according to IEC 60092-352, Clause 3.14. The cable voltage rating shall comply with the requirements specified according to IEC 60092-352, Clause 3.2. Cable cross-sectional areas and current carrying capacity of conductors shall comply with the requirements specified according to IEC 60092-352, Clause 3.3. Cable current ratings for continuous service shall, according to IEC 60092-352, Clause 3.3.3, be selected from Annex B, Tabulated Current Carrying Capacities General Installations. The conductor current carrying capacity of parallel connections of single core cables or multi core cables shall comply with the requirements specified according to IEC 60092-352, Clause 3.6. Cables and their insulated conductors shall be capable of withstanding the mechanical and thermal effects of the maximum short circuit current which can flow in any part of the circuit in which they are installed, taking into consideration not only the time/current characteristics of the circuit protective device, but also the peak value of the prospective short circuit current during the first half cycle. Further information is given in IEC 60949 and IEC 60724. Cables for essential/emergency power supply shall fulfil the requirements of IEC 60331. 4.5 Signal cables The following systems shall have their own dedicated cables: Digital communication (category 5e, optical fibre and coax) Fire detection and alarming (Twisted pairs) Equipment monitoring and alarm (Twisted pairs) The detailed specifications in the following sections should be regarded as recommendations. Other cable specifications may be used provided accepted by Energinet.dk ETS - 03 Rev. 1 11
4.5.1 Specification for category 5e cables Category 5e communication cables should be standard twisted 4 pair 100 MHz manufactured in accordance with ANSI/TIA 568B. Conductor: Bare copper (D. 0.52mm) Conductor insulation: Polyethylene, PE Collective screen: Outer sheath: Aluminium/polyester tape with tinned copper drain wire and tinned copper braid Orange Polyolefin 4.5.2 Specification for coax cables Coax cables should be standard 50 ohms. Conductor: Bare copper-stranded 7 x 0.75mm Dielectric: Solid polyethylene Ø7.24mm Inner screening: Inner jacket: Bare/tinned copper braid Halogen free compound (outer sheath if used inside) Armouring: Tinned copper braid (applicable for outdoor use) Outer Sheath: Halogen free compound (applicable for outdoor use) 4.5.3 Specification for optical fibre cables Optical fibre cables should be carefully chosen for the particular use. Preferably patch cables shall be used for indoor connections between panels. 4.5.4 Specification for twisted pair cables Twisted pair cables should normally be with common screen unless the particular installation require individual screen. Conductor: Stranded bare copper (Ø 0.75mm 2 ) Twisted in pairs Insulation: Cross linked polyethylene, XLPE Collective screen: Armouring: Aluminium/polyester tape with tinned copper drain wire and tinned copper braid Tinned copper braid Outer sheath: Polyolefin ETS - 03 Rev. 1 12
4.5.5 Selection The Category 5e cable should be used for all communication which is not fibre based. This cable should be for indoor use only, if used outdoor it shall be protected from the sun and from mechanical damage. The coax cable should be used for the transmission of signals from control panel to VDU, and for radio transmission via externally fixed antennas. The optical fibre cable should be used for most other communication. It shall be noted that the optical fibre for communication to shore will be integrated in the main 150kV power cable to shore. 5. Certificates / Data books NA. 6. Appendix NA. ETS - 03 Rev. 1 13