Technical Information for C.P Cables
This document covers the minimum requirements for the materials, construction, dimensions,packaging and tests of cables, intended for DC services in cathodic protection installation for pipelines, well casings, storage tanks,ships and other buried or water-submerged metallic structures.
2 - GENERAL CABLE CONSTRUCTION REQUIREMENTS
The conductors shall be plain annealed stranded copper. Stranding shall be circular (non-compacted).
The material shall be copper of such quality and purity that the finished product shall have the properties and characteristicsprescribed in IEC Publication 228 Class 2, or ASTM specification B8 Class B. Conductor sizes, as will be specifiedby the Purchaser, shall be in accordance with one of the designations listed in Table 1 to achievethe resistance value required:
TABLE 1 –Physical Properties of XLPE/PVC Cables
|MaximumResistance Of Conductor at 20°C||Approx. Weight||Approx. Overall Diameter (mm)||Nominal Sheath Thickness||Nominal Insulation Thickness||Nominal Cross Section|
|4.52 Ω/Km||77 kg/km||6.8 mm||1.4 mm||0.7 mm||4 mm²|
|3.02 Ω/Km||100 kg/km||7.4 mm||1.4 mm||0.7 mm||6 mm²|
|1.79 Ω/Km||144 kg/km||8.3 mm||1.4 mm||0.7 mm||10 mm²|
|1.13 Ω/Km||207 kg/km||9.3 mm||1.4 mm||0.7 mm||16 mm²|
|0.712 Ω/Km||305 kg/km||11.0 mm||1.4 mm||0.9 mm||25 mm²|
|0.514 Ω/Km||406 kg/km||12.2 mm||1.4 mm||0.9 mm||35 mm²|
|0.379 Ω/Km||560 kg/km||14 mm||1.5 mm||1.0 mm||50* mm²|
|0.262 Ω/Km||770 kg/km||16 mm||1.6 mm||1.1 mm||70 mm²|
|0.19 Ω/Km||1015 kg/km||18 mm||1.6 mm||1.1 mm||95 mm²|
* The actual cross-sectional area is approximately 47 mm².
The size, cross-sectional areas, and direct current resistance of the conductor in the completed cable shall conform theminimum and maximum values allowed by the above referenced standards.
TABLE 2 –Physical Properties of XLPE / PVC / SWA / PVC Cables
Single Core Plain annealed copper conductor, XLPE insulated / PVC extruded bedded / steel wire armoured / PVC sheathed. 600 / 1000 volts grade to BS5467.
|Approximate Weight (Kg/Km)||Approximate Overall Diameter||Number of Strands||Nominal Cross-Sectional Area|
Cable insulation shall be made from materials chemically and physically resistant to the environmental effects to be anticipated in buried or submerged service. It shall provide continuous coverage, adequate dielectric properties, and have a high resistance to abrasion, stress cracking and notch propagation. The insulation shall be one of the types listed in subclause 2.2.2. The insulation shall be applied tightly to the conductor without adhering to it and shall form a compact and homogeneous body.
The sheath (jacketing) shall be an extruded layer of the types listed in subclause 2.2.2. The sheath shall be continuous having a thickness as uniform as possible and not less than the values specified. It shall be possible to remove the sheath of the cable without damaging the insulation of the conductor. Cable insulation (primary insulation and sheath) shall be completely free of cracks, nicks, scratches, or other discontinuities. Cable insulation shall have a voltage rating of 600/1000 Volts in accordance with National Electrical Code.
2.2.2. Insulating and sheath materials
The types of insulation and sheath compound covered by this Part of Standard specification are listed below.
Insulation and sheath compound based on polyvinylchloride or copolymer of vinylchloride and vinyl acetate
conforming to ASTM specifications D 2219 (as Insulation) and D 1047 (as Jacketing).
Insulation and sheath compound based on thermoplastic polyethylene conforming to ASTM specifications D 1351
(as Insulation) and D 2308 (as Jacketing).
The polyethylene before application to the conductor (or cable) shall comply with the requirements of ASTM specification D 1248 for type I, Class A, B, or C; category 5; grade E5 or J3.
Insulation compound based on chemically cross-linked polyethylene conforming to ASTM specification D 2655.
The base polymer of this insulation consists substantially of polyethylene or a polyethylene copolymer.
Insulation compound based on especially chemical-resistant modified polyvinylidene fluoride conforming to ASTM specification D 3144.
3. SPECIFIC CABLE REQUIREMENTS
Cable insulation, as will be specified by the Purchaser, shall be either standard or chlorine resistant type and shallconform to one of the following alternatives:
3.1. STANDARD TYPE CABLE
A single jacket of High Molecular Weight Polyethylene (HMWPE).
A double jacket of High Molecular Weight Polyethylene primary insulation/Polyvinylchloride sheath
A double jacket of Cross-Linked Polyethylene (XLPE) primary insulation/Polyvinylchloride sheath.
The average thickness of cable insulation shall be 2.8 mm for conductor sizes up to 35 sq. mm and 3 mm for
larger sizes. The minimum thickness at any point shall not be less than 90% of the specified average thickness. In case of double jacket the thickness of sheath shall not be less than 1.5 mm.
3.2. CHLORINE RESISTANT TYPE CABLE
(To be used in saline water and salty soil ground beds).
Cable insulation shall be in accordance with one of the following alternatives, as will be specified by the Purchaser.
A single jacket of Polyvinylidene Fluoride (PVDF), single or double extruded with the minimum thickness of 0.75 mm.
A double jacket of a radiation cross-linked Polyvinylidene Fluoride primary insulation/High Molecular Weight Polyethylene sheath (minimum thickness 0.5 + 1.7 = 2.2 mm).