Type OnGcekż/w-GW, O2nGcekż/w-GW 3.6/6 kV

4-, 7-, and 10-core mining cables with two screens for a rated voltage of 3.6/6 kV

1. Overview and Standard

• Application:

  
  These cables are designed for underground mining applications, particularly to supply power to mobile equipment.

• Voltage Rating:

  
  They are built for a nominal voltage of 3.6/6 kV.

• Construction Types:

  
  Available in 4-, 7-, and 10-core versions, each featuring two screening layers for enhanced protection.

• Standard Compliance:

  
  Manufactured in accordance with the Polish standard ZN-KFK-011:1999.

2. Construction and Materials

• Conductors (Working & Auxiliary):

  • Made of multi-stranded, galvanized copper wires (class 5 as per PN-EN 60228).

  • The protective (or earth) conductor is created by interconnecting the screens of both working and auxiliary conductors.

• Separator:

  • A non-hygroscopic separator—typically a polyester film or similar material—is placed between the working conductors.

• Insulation:

  • All conductors are insulated with type IEP (ethylene-propylene) rubber following PN89/E-29100.

  • Thickness:

    • Working conductors: 3.4 mm

    • Auxiliary conductors: 1 mm

  • Color Coding:

    • Working conductors: available in natural, red, or blue.

    • Auxiliary conductors: provided in two natural, two red, and two blue variants.

• Screening System:

  • Individual Conductor Screen:

    • Each conductor is wrapped in a metallic braid made from galvanized copper wires combined with plastic yarn.

    • This braid is applied directly onto a non-metallic, conductive tape.

  • Overall (General) Screen:

    • An additional metallic braid, also of galvanized copper wires, is applied over a non-metallic screen.

    • Its design ensures a minimum copper cross-sectional area of 6 mm².

• Additional Components:

  • Separators & Inserts:

    • Components such as a three-armed separator made from conductive rubber (type P), vulcanized rubber inserts, and an inner rubber sheath (ON5) are used for structure and stability.

  • Outer Sheath (“Opona”):

    • Made of flame-retardant, oil-resistant rubber.

    • The variant marked with “O2n” has a two-layer construction reinforced with a plastic braid.

3. Explanation of Cable Marking

The designation (e.g., OnGcekż/w-GW or O2nGcekż/w-GW) can be broken down into its components:

• O₂n / On:

  • Indicates the type of outer sheath. “O2n” means a two-layer outer sheath with a reinforcing plastic braid, while “On” refers to a single-layer flame-retardant rubber sheath.

• Gc:

  • Refers to the insulated copper conductors (with ethylene-propylene rubber insulation).

• ekż:

  • Means that each conductor is individually shielded with a braid made of galvanized copper wires.

• w:

  • Denotes the presence of an overall (general) metallic screen made of galvanized copper wires.

• G:

  • Indicates that the cable is specifically designed for mining applications.

• GW:

  • Implies that the cable features longitudinal sealing (for additional protection, such as against moisture).

Example:

A cable marked as “OnGcekż/w-GW 4-żyłowy” is a 4-core mining cable rated for 3.6/6 kV, with working conductors of 70 mm² and a protective conductor of 25 mm².

4. Internal Structure (Core Configurations)

• 4-Core Cables:

  • Contain three insulated and screened working conductors.

  • The protective conductor is formed by three uninsulated screens (from the working conductors) arranged in grooves between them and twisted around a filler.

• 7-Core Cables:

  • Have three insulated and screened working conductors twisted around a central separator.

  • Include an assembly of auxiliary and protective conductors placed in the grooves between the working conductors. This assembly typically comprises a rubber insert, an auxiliary conductor (as a wrap or braid), its insulation, and a protective conductor (again as a wrap or braid).

• 10-Core Cables:

  • Feature three insulated and screened working conductors (twisted on a central separator).

  • Their auxiliary/protective system is more complex—formed by a pair of twisted insulated conductors, overlaid with an additional layer, a conductive tape braid, and an outer metallic braid placed in the grooves.

5. Electrical and Mechanical Characteristics

• Test (Withstand) Voltages:

  • Working Conductors:

    • 11 kV for AC tests

    • 26.4 kV for DC tests

  • Auxiliary Conductors:

    • 2 kV for AC tests

    • 4.8 kV for DC tests

• Mechanical Durability:

  • Excellent resistance to impacts, abrasion, and tearing.

  • The outer sheath is resistant to flame spread and oils.

• Temperature Ranges:

  • Ambient: −30°C to +50°C

  • Maximum Operating Temperature: +90°C

• Bending Radius:

  • The minimum recommended bending radius is specified as either 4 times the cable diameter (4D) or 2.5D, depending on the design.

• Packaging:

  • Typically supplied on reels, with a standard length of 250 meters.

6. Technical Data (Summary of Tables)

The documentation also includes detailed tables specifying various parameters for different cable configurations, such as:

• Conductor Details:

  • Nominal cross-sectional areas for working, auxiliary, and protective conductors.

  • Conductor diameters and insulation thickness.

• Current Ratings:

  • Continuous (long-term) current-carrying capacity.

  • Short-circuit current-carrying capacity.

• Earth Fault Characteristics:

  • Unit earth capacitance and earth short-circuit current values.

• Inductive Parameters:

  • Unit inductance and the reactance of the working conductors.

These tables help in selecting the appropriate cable type based on specific application needs and ensure that the cable’s electrical and mechanical performance meets the rigorous demands of underground mining environments.