Cable Basics | Understand Cables & Avoid Pitfalls When Purchasing

Cables act as the “blood vessels” for electricity and signals. They are used everywhere, from household socket wiring to photovoltaic power stations and factory power supply. Many buyers only focus on the cable diameter when selecting products, ignoring conductor material, cable type and application scenarios. This may lead to potential safety hazards. Let’s learn some practical cable knowledge to easily tell good cables from bad ones.

1. Basic Structure of Power Cables

A standard power cable mainly consists of three parts: conductor, insulation layer and outer sheath.

1. Conductor: The core part for electric transmission. Copper is the mainstream material, and aluminum conductors are also widely available. Copper features excellent conductivity, good flexibility and strong fatigue resistance, widely used in home wiring and precision equipment. Aluminum cables are lightweight with lower cost, suitable for long-distance outdoor large-capacity power transmission.
2. Insulation Layer: Wraps the conductor to isolate electric current and prevent electric leakage and short circuit. Common materials include PVC, cross-linked polyethylene (XLPE), low-smoke halogen-free compounds, etc. These materials vary greatly in temperature resistance and flame retardancy.
3. Outer Sheath: The outermost protective shell of the cable. It protects the cable against pulling force, moisture, corrosion and sunlight exposure. Buried and outdoor applications require stronger sheaths.

2. Copper Cable vs Aluminum Cable: How to Choose

✅ Copper Core Cable Advantages: Superior conductivity, low resistance and less heat generation; good ductility, stable connection and low oxidation risk; longer service life. Application: Indoor home wiring, control cabinets, short-distance power supply, scenarios with high safety requirements.

✅ Aluminum Core Cable Advantages: Light weight, lower raw material cost, great cost advantage for large cross-section long-distance wiring. Disadvantages: Higher resistivity; larger cross-section is required for the same current carrying capacity; connectors tend to oxidize, demanding higher construction standards. Application: Main lines of urban power grid, long-distance outdoor power transmission.

Tip: Do not compare prices blindly. If the cross-section of aluminum wire is undersized, severe overheating will occur and bring fire risks.

3. Flame-Retardant, Fire-Resistant & Low-Smoke Halogen-Free Cables

These cable types have similar names but totally different functions, which are often confused during procurement:

1. Flame-retardant Cable (ZR): It is hard to keep burning once exposed to fire. It will self-extinguish after the fire source is removed to stop flame spreading along cables. It cannot guarantee power supply during fire.
2. Fire-resistant Cable (NH): It can maintain power supply for a certain period under flame conditions. It is used for fire pumps, emergency lighting and other circuits that must keep working in fire accidents.
3. Low-smoke Halogen-free Cable (WDZ): Releases little smoke and no toxic halogen gas when burning. In case of fire, it reduces poisoning risk caused by dense smoke. Ideal for shopping malls, underground garages, office buildings, tunnels and other enclosed crowded spaces.

4. Larger Cross-section Is Not Always Better. Matching Current Carrying Capacity Matters

Current carrying capacity refers to the maximum current that a cable can safely carry for long-term operation. It is affected by conductor material, installation method (conduit, cable tray, direct burial), ambient temperature and the number of bundled cables.

• Too small cross-section: Overload current will cause continuous heating, accelerate insulation aging and easily result in short circuit and fire.
• Unnecessarily large cross-section: Wastes materials and raises project cost.

For engineering selection, calculate the current according to equipment power and line length, and reserve proper safety margin.

5. Tips for Cable Application

1. Avoid long-term overload operation.
2. Prevent cables from long-time soaking or heavy corrosion. Select waterproof & anti-corrosion types for special environments.
3. Do not bend or drag cables violently during installation to avoid damage to insulation.
4. Buy certified products from regular manufacturers and check certificates. Inferior cables use impure conductors and thin insulation, which carry serious safety risks.

Conclusion

Cables look ordinary, yet they are the cornerstone of power system safety. Whether for home wiring, industrial or photovoltaic projects, choosing the right cable type according to environment and power demand is far more important than simply chasing low prices.