Impact of temperature on conductor core performance

For electrical wires and cables, the conductor core plays a crucial role in transmitting electrical power. However, hot or cold ambient temperatures significantly affect the core's performance. So how exactly does temperature impact conductor cores? And how can we minimize these effects? This article will help you gain a deeper understanding of this issue.

1. Importance and physical mechanism of conductor cores

1.1 Importance of conductor cores

The conductor core is the most important component of any electrical wire or cable, responsible for carrying electric current in electrical devices and systems. The quality of the conductor core determines the stability, safety and efficiency of the entire system. One key factor directly influencing the core's performance is the surrounding ambient temperature as well as the core's own temperature when carrying current. Understanding and controlling temperature effects is absolutely essential to ensure safe operation and longevity of electrical systems.

1.2 Physical mechanism of temperature effects on conductive materials

Changes in temperature alter the electrical properties of conductive materials, explained by the following mechanism:

As temperature rises, free electrons in conductors tend to oscillate more vigorously around their equilibrium positions. This increases collisions between electrons and atoms in the crystal lattice, obstructing current flow and raising resistivity.

The increased oscillations also cause atoms in the lattice to tend to move further apart, leading to thermal expansion of the conductor.

The relationship between resistivity (ρ) and temperature (T) is described by the formula:

ρ = ρ₀[1 + α(T – T₀)]

Where:

ρ₀ is the resistivity at temperature T₀,
α is the temperature coefficient of resistivity, i.e. the rate of resistivity increase per unit temperature rise.

2. Temperature effects on conductor core performance

2.1 Electrical resistivity

As temperature increases, the resistivity of the conductor core also rises, leading to a decline in electrical conductivity. Consider this example:

Pure copper at 20°C has a resistivity of 1.68 x 10⁻⁸ Ω.m. The temperature coefficient of copper is 0.0039 K⁻¹.
Using the formula from section 1.2, when temperature rises to 70°C, the resistivity of copper wire increases by about 20%. This means the current carrying capacity of the conductor is significantly reduced.

To address this issue, the conductor cross-section needs to be increased, low-resistivity materials used, or operating temperature lowered.

2.2 Mechanical strength

High temperatures cause thermal expansion of the conductor, increasing mechanical stress. This greatly impacts the strength and lifespan of the conductive material:

Thermal expansion can induce mechanical stresses that deform the conductor. When exceeding the tolerance threshold, the conductor may crack or break.
Prolonged high temperatures also accelerate aging of the material, reducing its load-bearing capacity over time.

Therefore, the maximum allowable temperature of the conductor must be limited and appropriate materials selected to avoid mechanical failures.

2.3 Thermal conductivity and thermal expansion

Poor thermal conductivity combined with thermal expansion causes several issues for conductor cores:

Low thermal conductivity leads to uneven temperature distribution in the conductor, creating localized hot spots. This increases the risk of the insulating material being damaged by excessively high temperatures.
Thermal expansion at different rates between the conductor and surrounding insulation layers can create gaps that reduce the cable's insulation performance.

To mitigate this, materials with good thermal conductivity should be used, along with cooling systems using liquid nitrogen and reducing thermal stress on the wire.

3. Comparing temperature effects on different conductor core materials

Copper and aluminum are the two most commonly used metals for conductor cores. They have their own advantages and disadvantages in terms of electrical conductivity and heat resistance. Here are the resistivity and temperature coefficient values for copper and aluminum:


Property	Copper	Aluminum
Resistivity at 20°C (Ω.m)	1,68 x 10⁻⁸	2,65 x 10⁻⁸
Temperature coefficient of resistivity (K⁻¹)	0,0039	0,0043
Heat resistance	High	Medium

As can be seen, copper has lower resistivity and better heat resistance compared to aluminum. However, aluminum has lower density and is less expensive. Therefore, you can choose the appropriate material depending on the specific application.

Some special conductive materials can help minimize the adverse effects of temperature on conductor cores:

Heat-resistant aluminum alloys such as A6061, A5052, A7075… have good mechanical properties, can withstand high temperatures, and are suitable for applications in harsh environments.
High-temperature superconductors like YBCO (Yttrium-Barium-Copper-Oxide) compounds can conduct electricity with zero resistance at higher temperatures than traditional superconductors, completely eliminating resistive heat losses.

4. Measures to mitigate temperature effects

To reduce the negative impact of temperature on conductor cores, the following measures can be applied:

Design effective cooling systems to control conductor temperature, such as using oil, liquid nitrogen refrigerants, or natural cooling methods like placing cables in well-ventilated areas for heat dissipation.
Utilize heat-resistant insulating materials such as silicone, XLPE, etc.
Enhance heat dissipation by increasing surface area, such as using flat, rectangular, or grooved conductor shapes.
Use conductive materials with low resistivity that are less dependent on temperature, like copper or aluminum alloys.
Limit operating current to avoid overheating the conductor.

5. Frequently asked questions (FAQs) about conductor cores

5.1 What temperature is safe for conductor cores?

The safe operating temperature for a conductor depends on the type of insulating material surrounding it. For example, with PVC insulation, the core temperature should not exceed 70°C. For XLPE insulated cables, the temperature limit can be up to 90°C.

5.2 How to accurately measure the temperature of a conductor core?

Temperature sensors such as thermistors, RTDs (Resistance Temperature Detectors), or thermocouples can be used to measure conductor core temperature. For underground cables, fiber optic temperature sensing cables are often used along the cable length to obtain distributed temperature data.

5.3 What material is best for conductor cores in high-temperature environments?

Copper and heat-resistant aluminum alloys A6061, A5052, A7075… are top choices for conductors operating in high-temperature environments. They have low resistivity, low thermal expansion, and good mechanical strength at high temperatures.

6. Conclusion

Through this article, we have understood the significant impact of temperature on the performance of conductor cores. High temperatures increase resistance, reduce lifespan, and cause many undesirable issues for electrical systems. Therefore, thoroughly studying thermal effects and applying technical measures to minimize the impact of temperature on conductor core performance is crucial for safe operation of electrical systems.