Mining Cable Guide: Type G, G-GC, W & DLO

Mining cable is a heavy-duty, portable power cable designed for the harsh conditions found in surface and underground mining operations. Built to withstand repeated reeling, dragging over rough terrain, exposure to moisture, and mechanical abuse that would destroy standard power cable, mining cable delivers reliable power to mobile and semi-mobile equipment in some of the most demanding electrical environments in industry.

This guide covers the four primary mining cable types — Type G, Type G-GC, Type W, and DLO — along with their construction, voltage ratings, applicable standards, and how to select the right cable for your application.

Governing Standards: ICEA and MSHA

Mining cable is manufactured and tested under stricter requirements than general-purpose industrial cable. Two organizations define the standards that matter:

ICEA (Insulated Cable Engineers Association) publishes the design and performance standards for portable mining cable. The primary standard is ICEA S-75-381 / NEMA WC-58, which covers portable and power feeder cables for use in mines. This standard defines conductor construction, insulation thickness, jacket requirements, voltage ratings, and test methods.

MSHA (Mine Safety and Health Administration) is the federal regulatory body that approves cables for use in U.S. mining operations. Cables used underground or in surface mines must carry MSHA approval (flame test acceptance per 30 CFR Part 7). MSHA-approved cables are tested for flame resistance to ensure they self-extinguish and do not propagate fire in mine environments where ventilation can feed combustion. An MSHA approval number is printed on the cable jacket.

In addition to ICEA and MSHA, mining cables are commonly listed by UL® (Underwriters Laboratories) and CSA (Canadian Standards Association). Many cables also meet OSHA requirements under 30 CFR 56/57 (surface metal/nonmetal mines) and 30 CFR 75/77 (underground/surface coal mines).

Mining Cable Types at a Glance

All four types are rated 2,000V (2 kV) and are designed for portable or semi-portable use in mining environments. The key differences are conductor count, ground-check capability, and application flexibility.

Type G Mining Cable

Type G is a three-conductor portable power cable with an overall grounding conductor, rated 2 kV. It is the standard trailing cable for connecting portable and mobile mining equipment — continuous miners, shuttle cars, roof bolters, load-haul-dump (LHD) machines, and longwall equipment — to the mine power distribution system.

Construction

Type G cable contains three insulated power conductors and one or more grounding conductors (some constructions include two grounds for lower impedance), all within a heavy-duty overall jacket. The power conductors use flexible, finely stranded copper (Class H or Class K stranding) for repeated flexing during reeling operations. Individual conductor insulation is typically EPR (ethylene propylene rubber) or XLPE rated for 2 kV. The grounding conductor(s) may be cabled into the interstices or applied as a concentric layer. The overall jacket is a heavy thermoset rubber compound — typically CPE (chlorinated polyethylene) or neoprene — engineered for flame resistance, abrasion resistance, oil resistance, and flexibility in cold temperatures.

When to Use Type G

Type G is specified when three-phase portable power is needed and the mine’s electrical system does not require a separate ground-check conductor. This is common in surface mining operations and some underground applications where ground-fault protection is achieved through other means (ground-fault relays on the power center). Type G is also used in industrial applications outside of mining where a rugged, flame-resistant portable power cable is needed.

Type G-GC Mining Cable

Type G-GC is identical to Type G in construction, with one addition: a separate ground-check conductor. The “GC” designation stands for ground-check.

What Is a Ground-Check Conductor?

The ground-check conductor is a small-gauge insulated conductor (typically 10 AWG or 8 AWG) that is part of a continuous ground-monitoring circuit. This circuit monitors the integrity of the equipment grounding system while the cable is energized. If the grounding conductor is broken, damaged, or disconnected, the ground-check circuit detects the fault and trips the power, de-energizing the equipment before a ground-fault can create a hazardous condition.

When to Use Type G-GC

MSHA regulations (30 CFR 75.703) require continuous ground-check monitoring on trailing cables in underground coal mines. Type G-GC satisfies this requirement. It is also increasingly specified in underground metal/nonmetal mines and in surface operations where enhanced ground-fault protection is desired. If you are supplying cable for an underground coal mine, Type G-GC is almost always the required cable type for trailing cable applications.

Type G vs. Type G-GC

Type W Mining Cable

Type W is a general-purpose portable power cable commonly used in mining and heavy industrial applications. Unlike Type G, which is fixed at three power conductors, Type W is available in configurations ranging from single-conductor to six or more conductors, with or without ground-check conductors. This flexibility makes it the most versatile option in the mining cable family, though its use extends well beyond mining into shipyards, steel mills, construction, and other demanding environments.

Construction

Many Type W cables use individually jacketed conductors assembled under an overall jacket. In this construction, each power conductor has its own EPR or XLPE insulation plus an individual CPE or neoprene jacket, and the assembled conductors are then enclosed in a heavy overall jacket. This double-jacketed construction provides additional mechanical protection and makes it easier to strip and terminate individual conductors in the field.

Common Configurations

Type W vs. Type G

Type W with three power conductors and a ground serves the same function as Type G. The difference is in construction: Type W’s individually jacketed conductors offer better mechanical protection and easier field termination, while Type G’s construction (conductors share a common jacket) results in a slightly smaller overall diameter and can be more flexible at equivalent sizes. The choice often depends on mine preference, equipment requirements, and whether the cable will be spliced or terminated frequently in the field.

DLO (Diesel Locomotive) Cable

DLO cable is a single-conductor, 2 kV-rated cable originally designed for wiring diesel-electric locomotives in underground mines. The name stands for “Diesel Locomotive” — but its use extends far beyond locomotives. DLO has become a standard heavy-duty single-conductor cable used across mining, industrial, and power distribution applications.

Construction

DLO uses a flexible, finely stranded bare or tinned copper conductor (Class H or Class K stranding per ASTM B172) with EPR insulation and a heavy CPE or CSPE outer jacket. The combination of fine stranding and thermoset rubber compounds gives DLO excellent flexibility for its voltage rating — comparable to welding cable in pliability, but with a 2 kV insulation rating instead of 600V.

Common Applications

Despite the name, DLO cable is used for far more than locomotive wiring:

DLO vs. Welding Cable

DLO and welding cable are physically similar — both use fine-stranded copper with thermoset rubber insulation and are highly flexible. The critical difference is voltage rating and flame resistance. DLO is rated 2 kV and many DLO constructions carry MSHA flame-test approval; welding cable is rated 600V and is not MSHA-approved. In mining applications or anywhere a 2 kV rating and flame resistance are required, DLO is the correct choice. For standard welding, battery cable, and 600V portable power applications where MSHA approval is not needed, welding cable is typically more economical.

Construction Details and Sizing

Conductor Stranding

Mining cables use finely stranded copper conductors for flexibility during reeling and repeated bending. Common stranding classes include Class H (flexible), Class K (extra-flexible, 30 AWG strands), and Class M (extremely flexible, 34 AWG strands). Class H is standard for most mining cable; Class K and M are specified for applications requiring tighter bend radii or more frequent flexing cycles.

Insulation

EPR (ethylene propylene rubber) is the dominant insulation material for mining cable. EPR provides excellent dielectric strength at 2 kV, resists moisture, handles temperature extremes (−40°C to +90°C typical), and remains flexible after years of service. Some cables use XLPE insulation, which provides similar electrical performance with slightly different mechanical properties.

Jacket

The overall jacket is the cable’s first line of defense against the mine environment. CPE (chlorinated polyethylene) is the most common jacket material, offering flame resistance, oil resistance, abrasion resistance, and cold-temperature flexibility. Neoprene (polychloroprene) is also used, with superior resistance to oils and chemicals. All jackets must pass MSHA flame testing (30 CFR Part 7, Subpart K) for underground use.

Standard Sizes

Mining cables are available in a wide range of conductor sizes. Power conductors typically range from 8 AWG for small equipment feeds up to 4/0 AWG or 500 kcmil for most trailing cable applications. Large dragline trailing cables and main power feeders can exceed 500 kcmil, with some dragline cables sized at 1000 kcmil or larger. DLO extends up to 2000 kcmil for switchgear and transformer connections. Conductor sizing follows NEC® and MSHA ampacity requirements, derated for the cable’s installation conditions (ambient temperature, number of conductors, and whether the cable is reeled or unreeled).

Common Mining Applications

Underground Coal Mining

Underground coal mines have the strictest cable requirements in the industry. MSHA mandates flame-resistant, MSHA-approved trailing cables with ground-check conductors (Type G-GC) for all portable equipment. Continuous miners, shuttle cars, roof bolters, feeder-breakers, and battery scoops all connect to the mine power system via trailing cables that are reeled and unreeled as equipment advances. DLO is used throughout mine power centers for internal wiring and as feeder cable from transformers to distribution boxes.

Underground Metal/Nonmetal Mining

Hard-rock underground mines (gold, copper, zinc, etc.) use Type G, G-GC, and Type W trailing cables for LHD loaders, jumbos (drill rigs), bolters, and haulage equipment. Ground-check conductors are increasingly specified even where not strictly required by regulation, as an added safety measure. DLO is used for power distribution in mine substations and for connecting transformers to switchgear.

Surface Mining

Surface mines — open-pit, strip, and mountaintop operations — use mining cable for draglines, electric shovels, drills, conveyors, and portable crushing and screening plants. Cable lengths can be considerable (1,000+ feet for dragline trailing cables), and cables are subjected to dragging, reeling, and exposure to sunlight, mud, rock, and extreme temperatures. Type G and Type W are the standard trailing cable choices for surface operations. DLO is used as power feeder cable from substations to portable power centers.

Tunneling and Construction

Tunnel boring machines (TBMs), roadheaders, and other heavy tunneling equipment use mining-type cable because it meets the flame-resistance and mechanical durability requirements of underground construction environments. Mining cable is also used in shaft sinking, mine ventilation fan power feeds, and dewatering pump connections.

How to Select the Right Mining Cable

1. Determine the Cable Type

Start with the regulatory requirements. Underground coal mines require Type G-GC for trailing cables. Surface mines and underground metal/nonmetal mines typically use Type G or Type W. If ground-check monitoring is required or preferred, specify G-GC or Type W with a ground-check conductor. For single-conductor power feeds, battery connections, and switchgear wiring, use DLO.

2. Size the Conductors

Size power conductors based on equipment full-load amperage (FLA), derated for ambient temperature and installation conditions per NEC® Article 400 and applicable MSHA regulations. For trailing cables on reeling equipment, also consider voltage drop over the total cable length — long runs to mobile equipment can produce significant voltage drop that degrades motor performance.

3. Confirm Voltage Rating

Standard mining cable is rated 2 kV. For higher-voltage applications (5 kV, 8 kV, 15 kV, 25 kV), medium-voltage mining cable is available with additional shielding and insulation per ICEA S-75-381. Higher-voltage cables are used for main power feeders, longwall power supplies, and large dragline trailing cables.

4. Verify MSHA Approval

Any cable used in a U.S. mine must carry MSHA approval appropriate to its intended use. Check that the cable’s MSHA acceptance number is printed on the jacket and corresponds to the correct cable type and voltage rating. For Canadian operations, verify CSA certification.

5. Match the Jacket to the Environment

CPE jackets cover most mining applications. Specify neoprene if the cable will be exposed to significant oil, fuel, or chemical contact. For extreme cold (−40°C and below), verify the jacket compound’s cold-bend rating. For surface installations with UV exposure, confirm the jacket is sunlight-resistant.

6. Plan for Splicing and Repair

Mining cables are frequently spliced in the field after damage. Type W’s individually jacketed conductors are generally easier to splice than Type G’s shared-jacket construction. If frequent field splicing is expected, Type W may be the more practical choice. All splices must use MSHA-approved splice kits and be performed by qualified personnel per 30 CFR requirements.

Frequently Asked Questions

What is the difference between Type G and Type G-GC mining cable?

The only difference is the ground-check conductor. Type G has three power conductors and a grounding conductor. Type G-GC adds a small insulated ground-check conductor that provides continuous monitoring of the grounding circuit’s integrity. Underground coal mines require Type G-GC per MSHA regulations (30 CFR 75.703). Surface mines and underground metal/nonmetal mines may use either type depending on the mine’s electrical safety requirements.

Can I use Type W instead of Type G?

Yes. Type W with three power conductors and a ground is functionally equivalent to Type G, and Type W with a ground-check conductor is functionally equivalent to Type G-GC. Type W’s individually jacketed conductors provide additional mechanical protection and easier field termination. The choice between Type G and Type W often comes down to mine preference, equipment OEM specifications, and whether frequent field splicing is anticipated.

Is DLO the same as welding cable?

No, although they look and feel similar. Both use finely stranded copper with thermoset rubber insulation and are highly flexible. The key differences are voltage rating and flame resistance. DLO is rated 2 kV and many DLO constructions carry MSHA flame-test approval. Welding cable is rated 600V and is not MSHA-approved. In mining and industrial applications requiring a 2 kV rating or flame resistance, DLO is required. For standard welding and 600V applications outside of mining, welding cable is typically sufficient and more economical.

Do I need MSHA-approved cable for surface mines?

Yes. MSHA regulations apply to both surface and underground mining operations in the United States. Cables used in surface metal/nonmetal mines must meet 30 CFR 56/57, and cables in surface coal mines must meet 30 CFR 77. While the specific cable construction requirements may differ between surface and underground operations, MSHA approval is required for both. Always verify the cable’s MSHA acceptance number and ensure it corresponds to the intended use.

What conductor stranding should I specify?

Class H stranding is standard for most mining cable applications and provides good flexibility for reeling operations. Class K (30 AWG strands) offers greater flexibility and is specified for applications with tight bend radii or higher flex-cycle requirements. Class M (34 AWG strands) provides maximum flexibility but is less common in mining cable and costs more. For most trailing cable applications, Class H is sufficient. Specify Class K for equipment with small reels or very frequent reeling cycles.

Can mining cable be used outside of mining?

Yes. Mining cable is frequently used in non-mining applications where a rugged, flame-resistant portable power cable is needed. Common industrial uses include steel mills, marine terminals, construction sites, shipyards, and any environment where cable is subjected to heavy mechanical abuse, reeling, or exposure to oil and chemicals. The 2 kV rating and MSHA flame resistance make mining cable a premium choice for demanding industrial power distribution.

Related Resources

• Portable Cord Guide: Types, Ratings & Applications
• Welding Cable: Sizing, Types & Selection Guide
• How to Choose the Right Cable for Your Project
• Wire & Cable for Mining
• Wire & Cable for Northern Nevada Mining

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