This article is about Medium Voltage IEC Cable Material Selection Criteria & Design Requirements of Electrical Power System as per International Codes and standards for Commercial Buildings, Plants and Refinery Projects.
Medium Voltage IEC Cable Material Selection Criteria & Design
Certification for IEC Cables
- The MV power cable shall be manufactured and tested in accordance with International Electrotechnical Commission ( IEC) 60502-2.
From IEC 60228 STANDARD METRIC SIZES OF CABLES”
Medium-voltage cables meeting the requirements of 15-SAMSS-502 are suitable for use in Class I, Division 2 and Zone 2 locations. Cables manufactured in accordance with IEC 60502-1 and rated 600/1000 V, having similar constructions to those listed in NEC Article 501-4 (b), are suitable for use in Class 1, Division 2 and Zone 2 locations.
General Requirements For MV Cables
Acceptable Manufacturers – The list of acceptable manufacturers of MV Power Cable is as shall in Table.
- Substitution of IEC cable with AEIC cable, if IEC cable is specified, and vice versa, is prohibited.
- New and Unused – Electrical materials shall be new and unused.
- As Designed – Electrical materials shall be in accordance with the Saudi Aramco-approved project-specific design drawings, diagrams, schedules, lists, databases, and associated documents.
- Free of Damage – Electrical materials shall be free of damage. Cable ends are not damaged. Factory-sealed ends or factory installed pulling eyes, if installed, are intact.
- QC Before Installation – Electrical materials shall conform to all applicable requirements, standards, and specifications prior to release to be used as part of the work. Upon receipt on-site, the cable shall be tested on reels for continuity and insulation resistance.
- Identification – Electrical materials shall be identified by using tags, stamps, color coding, stencils or labels. The location and method of identification shall not affect the function or quality of the materials.
- Traceability – Electrical materials shall be traceable from the manufacturer and supplier through delivery, storage, fabrication, erection, installation, repair, modification and use.
- Each phase of multi-conductor cables shall be permanently identified.
- Cables shall be marked on the outer non-metallic sheath (jacket) at intervals not exceeding 1 m with the following information:
1) Rated voltage
2) Insulating compound (XLPE or EPR)
3) Number, size and material (“”COPPER”” or “”CU””) of conductors
4) Manufacturer’s name
5) Year of manufacture” - Reels shall be made of steel, or, alternatively, shall be heavy duty wood reels. Reels shall be lagged with wood, and shall be marked with a durable label securely attached to a flange of the reel and plainly stating Buyer’s Purchase Order number, shipping length of cable on reel, number, type and size of conductors, cable configuration, and voltage rating. Cable ends shall be sealed and capped.
- Additional Optional Water and Water Tree Protection
- One or more of the following shall be provided, if specified:
1. Longitudinal water protection, in the form of semiconducting water blocking swellable tapes applied under and over the metallic screen or concentric neutral.
2. Longitudinal water protection for the conductors, in the form of strand sealant.
3. Radial water ingress protection, in the form of plastic coated laminated aluminum or copper tape immediately under the outer jacket and firmly bonded to it.
4. Tree-Resistant XLPE (TRXLPE) instead of XLPE insulation.” - Minimum size of MV cable shall be as follows: (Table -1)
Voltage Size
5 kV 10mm² (8 AWG)
15 kV 35mm² (2 AWG)
35 kV 50 mm² (1/0 AWG) ”
Maximum size of conductors rated below 69kV shall be 500mm² or 1,000 kcmils.
Specific Requirements For IEC Cables
- Insulating Material – Insulating material shall be crosslinked polyethylene (XLPE) or ethylene propylene rubber (EPR), as specified. Thermoplastic insulating compound are not acceptable.
- The rated voltage, nominal insulation thickness of the cable shall be in accordance with the table below.
- The conductors shall be of Class 2 annealed copper in accordance with IEC 60228, plain or metal coated as specified. Conductor sizes shall be standard metric IEC 60228 sizes.
Exception: Conductor sizes shall be permitted to be standard AWG or kcmil sizes, if so specified in the purchase order, for accommodation of equipment such as separable connectors (elbows). In this case, all requirements of IEC 60228 and 60502-2 shall apply, as they relate to the closest standard metric size.” - Conductor and insulation screening is required for all cables.
- Conductor screening (shield) shall be easily removable from the conductor, and shall consist of either a layer of extruded semiconducting compound, or a layer of extruded semiconducting compound over a semiconducting tape.
- The non-metallic part of the insulation screen (shield) shall consist of a layer of extruded semiconducting compound. Semiconducting coatings (paints) are not allowed.
- The metallic part of the insulation screen (shield) shall consist of copper tape(s), and shall be applied separately over each of the semicon-shielded, insulated conductors. Copper tape shall be a minimum of 0.125 mm (5 mil) thickness, applied with a minimum of 20% overlap.
- If a concentric neutral conductor is specified in the purchase order, it shall consist of copper wires with the specified cross section, and shall be plain or metal coated as specified. The concentric neutral conductor shall be under the outer jacket. The concentric neutral wires may serve as, and take the place of the copper tape screen (shield).
- Concentric neutral wire, metallic armor, and metallic sheaths shall be protected with a PVC or equivalent jacket.
- IEC 60502-2 Class 2, stranded copper ground conductor(s) shall be provided in the interstices of the cable, if specified in the purchase order.
- Fillers (extruded material or non-hygroscopic fibers) shall be used in order to ensure the cable is compact and round in cross-section.
- Metallic armor, when specified in the purchase order, shall be galvanized steel double tape armor, or galvanized steel wire armor.
Exception: For single conductor cables, material shall be aluminum instead of steel.” - All cables shall have a continuous overall outer nonmetallic sheath (jacket).
- The outer sheath (jacket) shall be polyvinyl chloride (PVC), suitable for 90°C maximum rated conductor temperature.
- The outer sheath (jacket) shall be sunlight resistant and oil resistant.
- Cables shall be suitable for direct burial and for installation in duct banks, above grade rigid steel conduit and cable trays.
International Standard and Codes for Medium Voltage IEC Cable
- Non-Hazardous Indoor Enclosures, Installation and Pre-Commissioning
- Boxes, Enclosures, and Accessories Materials Selection & Requirements
- SAES-P-101 Regulated Vendors List for Electrical Equipment, 09 June 2007
- SAES-P-104 Wiring Methods and Materials, 13 January 2008
- 15-SAMSS-502 Medium Voltage Power Cable 5 kV through 35 kV, 02 August 2006
- NFPA 70 National Electrical Code (NEC), 2008 Edition
- IEC 60502-2 Power Cables with Extruded Insulation and Their Accessories for Rated Voltages from 1 kV up to 30 kV – Part 2: Cable for Rated Voltages from 6 kV up to 30kV
- IEC 60038 IEC Standard Voltages
- IEC 60228 Conductors of Insulated Cables
- IEC 60332-3 Tests on Electric Cables Under Fire Conditions – Part 3 : Tests on Bunched Wires and Cables