IEC 63026-2019 pdf free.Submarine power cables with extruded insulation and their accessories for rated voltages from 6 kV(Um =7,2 kV) up to 60 kV(Um= 72,5 kV)-Test methods and requirements.
For all cables, the selected insulation thickness shall result in a nominal electric stress at theconductor screen not higher than 8,0 kV/mm and at the insulation screen not higher than4,0 kV/mm.
Higher stress cables are under consideration.
The thickness of any separator or semi-conducting screen on the conductor or over theinsulation shall not be included in the thickness of the insulation.
5.4 screening
Screening of individual cores in single or three-core cables,shall consist of a conductorscreen and an insulation screen.
The conductor screen shall be non-metal and shall consist of an extruded semi-conductingcompound，which may be applied on top of a semi-conducting tape. The extruded semi-conducting compound shall be firmly bonded to the insulation.
The insulation screen shall consist of a non-metal semi-conducting layer in combination with ametal screen.
The non-metal layer shall be extruded directly upon the insulation of each core and consist ofa firmly bonded semi-conducting compound.
For submarine cables,semi-conducting screens should be firmly bonded in order to betterresist the mechanical stresses during the cable laying.
A layer of semi-conducting tape or semi-conducting compound may then be applied over theindividual cores or the core assembly.
5.5 Metal screen
The metal screen shall be applied over the individual cores or the core assembly and shallconsist of one or more tapes, or a braid, or a concentric layer of wires,or a combination ofwires and tape(s), or a metal sheath.
Measures may be taken to achieve longitudinal water-tightness in the metal screen. Whenchoosing the material of the screen, special consideration shall be given to the possibility ofcorrosion, to ensure satisfactory mechanical and electrical performance.
In particular cases,the steel wire armour of three-core cables can be considered a metalscreen.
5.6Core oversheathing materials
When requested, an oversheath is applied over the metal screen.An oversheath based onpolyethylene (PE) type ST- is recommended,see tables 5 and 7.
Alternatively, a semi-conductive PE oversheath is allowed. lt is recommended that thisoversheath material should have the same non-electrical properties as for ST-, except for thecarbon black content.
Particular care should be taken to limit the transient overvoltages that may affect longsubmarine cables.
5.7Assembly of three-core cables and fillers
The assembly of three-core cables shall maintain an approximately round shape.
The materials used for the fillers and the bedding shall be suitable for the operatingtemperature of the cable and compatible with the insulating material and/or sheath materialand with the marine environment.
5.8Cable armour
This document covers round or flat wire armour，the wires shall be of galvanized steel,stainless steel, copper or tinned copper or other corrosion-resistant metal alloys. In somecircumstances in order to make the cable lighter the armour can be a mixture of metal wiresand plastic wires.
An additional layer of metal tapes may be applied for extra protection in special applications ifrequired.
The armour may be a single or a double layer of wires that may be applied in the same oropposite direction depending on the laying conditions and the mechanical performancerequested for the cable.The armour shall be applied on a bedding layer to avoid damagingthe core(s).
Non-magnetic armour shall be used for single-core cables.
When choosing the material of the armour，special consideration shall be given to thepossibility of corrosion, not only for mechanical safety, but also for electrical safety.IEC 63026 pdf download.