Detailed Description
What Is a Single Core Power Cable?
A single core power cable is a 0.6/1 kV cable containing one insulated conductor — one phase, one neutral, one earth, or one DC polarity — in a single cable assembly with its own armour and outer sheath. It is not "incomplete" three-core cable; it is a distinct cable type with its own applications, advantages, and installation requirements.
In power distribution, single-core cables are used in three ways:
- For single-phase circuits: One line conductor and one neutral conductor, each as a separate single-core cable
- For DC circuits: Separate positive and negative single-core cables
- For three-phase circuits: Three single-core cables laid in parallel (trefoil or flat formation), replacing one three-core cable
Single-Core vs Three-Core — When Separate Phases Are Better
| Consideration | Single-Core (3 Cables) | Three-Core (1 Cable) |
|---|---|---|
| Weight per cable | Lower — one phase per cable | Higher — three phases in one assembly |
| Handling and pulling | Easier — individually manageable | Difficult — heavier reel, requires larger team or winch |
| Bending radius | Smaller individual OD — smaller bend radius | Larger OD — larger bend radius; may require larger cable trench radius |
| Heat dissipation | Better — each phase has full air circulation around the cable | Worse — phases are in mutual thermal contact |
| Ampacity (same total cross-section) | Higher — better cooling | Lower — mutual heating |
| Phase balancing | Easier — each cable can be routed independently to equalize length | Fixed — all phases follow the same path |
| Magnetic field | Higher external magnetic field if phases are separated; canceled if laid in trefoil | Lower external field — phases are tightly coupled |
| Armour heating (AC) | Critical issue — steel SWA on single-core must use non-magnetic glands; aluminum armour preferred | Less critical — phase currents sum to near zero, minimizing net induced current |
| Installation cost | Higher — three cable pulls, three terminations | Lower — one cable pull, one termination set |
| Typical cross-section range | Any size, but preferred ≥185 mm² | ≤400 mm² standard; up to 630 mm² on request |
The Single-Core SWA Problem — Non-Magnetic Glands Are Not Optional
This is one of the most common installation errors in industrial power distribution: installing single-core steel wire armoured (SWA) cable with standard steel cable glands. The problem:
In a single-core AC cable, the current in the conductor induces a magnetic field around the cable. This time-varying magnetic field induces eddy currents in any conductive material surrounding the conductor — including the steel armour wires, the steel gland, and the steel gland plate. The eddy currents generate I²R heating. If the gland and gland plate are magnetic steel, the magnetic permeability concentrates the flux, increasing the eddy current heating. The result: the gland can reach temperatures exceeding 100°C, damaging the cable sheath at the gland entry and potentially causing insulation failure.
The solution has three parts:
- Non-magnetic glands: Brass or aluminum cable glands replace standard steel glands. These materials are non-magnetic and have higher resistivity, reducing eddy current magnitude
- Non-magnetic gland plates: The gland mounting plate must also be non-magnetic — brass, aluminum, or non-magnetic stainless steel (grade 316). A steel gland plate with brass glands still creates a magnetic circuit through the plate
- Aluminum wire armour (AWA) for single-core: Where SWA is traditionally specified, aluminum wire armour is electrically and magnetically superior for single-core AC applications. Aluminum is non-magnetic (relative permeability ≈1) and has lower resistivity than steel, further reducing eddy current losses
Parallel Phase Installation — Ampacity Through Multiplication
When a single 630 mm² conductor cannot carry the required current (e.g., a 2 500 A feeder), parallel conductors are the solution: two or more single-core cables per phase, connected in parallel at both ends. The current divides between the parallel cables in inverse proportion to their impedances.
For successful parallel operation:
- All parallel cables per phase must have the same conductor material, cross-section, length, and routing. Differences in length create impedance imbalance, causing unequal current sharing — one cable carries more current, approaches its thermal limit, while the other runs cool
- The cables must be grouped by phase triplet (L1, L2, L3 together in trefoil or flat), not by parallel group (both L1 cables together). Grouping by phase cancels the magnetic field, reducing external field and inductive reactance
- Cable spacing between parallel groups must be equal to maintain equal impedance per group
Why Choose Yichi Single Core Power Cables
- XLPE or PVC, copper or aluminum, armoured or unarmoured — you choose: We manufacture all standard combinations. The specification is defined by the application requirements — we do not limit the options to simplify our production
- Full 1.5–1 000 mm² cross-section range: From control power to utility feeder — a single manufacturer for the complete single-core cable specification
- AWA (aluminum wire armour) available: For single-core AC applications, aluminum wire armour reduces eddy current losses compared to steel armour. Specify AWA for installations where magnetic gland issues are a concern or where the efficiency loss from armour heating must be minimized
- Application support for parallel installations: Provide the circuit current, voltage, length, and installation method — we calculate the required cross-section, recommend the number of parallel cables per phase, and verify the current sharing and voltage drop per IEC 60287
- Type test data available: Full test certificates for conductor resistance, insulation resistance, high-voltage withstand, and armour continuity per IEC 60502-1 for every production batch