I. Advantages of copper core cables over aluminum core cables:
1. Low resistivity:
The resistivity of aluminum core cables is about 1.68 times greater than that of copper core cables.
2. Good ductility:
The elongation rate of copper alloys is 20-40%, the elongation rate of electrical copper is more than 30%, while that of aluminum alloys is only 18%.
3. High strength:
The allowable stress at room temperature for copper is 7-28% higher than for aluminum. Especially at high temperatures, the voltage difference between the two is even more significant.
4. Fatigue resistance:
Aluminum material is prone to fracture after repeated bending, while copper is not. In terms of elasticity index, copper is also about 1.7-1.8 times higher than aluminum.
5. Good stability, corrosion resistance:
The copper core is resistant to oxidation and corrosion, while the aluminum core is susceptible to oxidation and corrosion.
6. Large current carrying capacity:
Due to low resistivity, the allowable current-carrying capacity (the maximum current that can pass) of copper-core cables with the same cross-section is about 30% higher than that of aluminum-core cables.
7. Low Voltage Loss:
Due to the low resistivity of copper core cables, they have a lower voltage drop when the same current passes through the same cross section.
Therefore, for the same transmission distance, it can guarantee higher voltage quality; or in other words, under permissible voltage drop conditions, copper core cables can transmit power over greater distances, i.e., they have a larger power coverage area, which is beneficial for planning temporary power networks and reduces the number of power points required. .
8. Low heating temperature:
Under the same current, the heat generated by copper core cables of the same cross section is much lower than that of aluminum core cables, making the operation safer.
9. Low Power Consumption:
As copper has low resistivity, compared to aluminum cables, copper cables have less electrical energy loss, which is obvious. This is beneficial to improve power generation efficiency and protect the environment.
10. Oxidation resistance, corrosion resistance:
Copper core cable connections are stable and do not cause accidents due to oxidation. The joints of aluminum core cables are often unstable and can cause accidents due to increased contact resistance and oxidation heating. Therefore, the accident rate is much higher than that of copper core cables.
11. Easy to Install:
- The copper core is flexible with a small allowable bending radius, so it is easy to bend and pass through conduits;
- The copper core is fatigue resistant and is not prone to breaking after repeated bending, making wiring convenient;
- The copper core has high mechanical resistance, can withstand greater mechanical stress, bringing great convenience to the laying of the construction, in addition to creating conditions for mechanized construction.
II. Advantages of aluminum core cables over copper core cables
1. Cheapest Price:
The price of copper bar is 3.5 times that of aluminum bar, and the specific gravity of copper is 3.3 times that of aluminum, so aluminum core cables are much cheaper than copper core cables, suitable for low capital projects or temporary power supply.
2. The cable is very light:
The weight of aluminum core cables is 40% of the weight of copper core cables, resulting in lower construction and transportation costs.
3. Oxidation resistance, corrosion resistance:
Aluminum reacts quickly with oxygen in the air to form an oxide film, which prevents further oxidation, making aluminum conductors the preferred material for high voltage, large cross section, long range overhead transmission.
4. Aluminum wire dissipates heat faster than copper wire.
Copper wire has lower resistance. Aluminum wire has greater resistance than copper wire, but dissipates heat more quickly than copper wire.
Although aluminum core cables are very cheap, copper cables have notable advantages in cable power supply, especially in the field of underground cable power supply.
The use of copper core cables for underground power supply has characteristics such as low accident rate, corrosion resistance, high reliability and convenient construction and maintenance. This is also the reason why copper cables are mainly used in underground cable power supply in China.
III. Related specifications
1. Civil electrical project specifications:
Cables and wires can be copper core or aluminum core, but copper core cables or wires should be used for civil buildings. Copper core cables or wires should be used in the following locations:
(1) Flammable and explosive places;
(2) Public buildings and important residential buildings;
(3) Locations that are particularly humid and corrosive to aluminum;
(4) Places with a large concentration of people;
(5) Important data rooms, computer rooms and important warehouses;
(6) Mobile equipment or places with strong vibration;
(7) Other locations with special regulations.
2. Power engineering cable design specifications
Control cables must use copper conductors. Power cables used in the following situations must use copper conductors:
(1) Circuits that need to maintain high connection reliability, such as motor excitation, important power sources, mobile electrical equipment, etc.;
(2) Adverse work environments with intense vibrations, explosion risks or corrosive agents;
(3) Fire resistant cables;
(4) Arranged close to high temperature equipment;
(5) Public installations with high security requirements;
(6) When a larger working current is required, the number of cables needs to be increased.
Except for products that are limited to having only copper conductors and where it is determined that copper conductors will be used, the cable conductor material may be copper or aluminum.
4. Calculation of current load capacity
A 25m2 copper cable, when placed overhead, allows a current of 120A with a capacity of 67KW, and when directly buried it is 110A, 61KW. A 35m2 copper cable is allowed a current of 147A, 82KW and a current of 130A, 75KW. A 35m 2 aluminum wire, if reduced by 30%, allows a current of 103A, 57KW; and a current of 91A, 53KW.
Not as good as 25m 2 copper cable (capacity is based on 380V three-phase, Cosφ=0.85; if 220V single-phase, Cosφ=0.85, the capacity should be multiplied by 1/3); copper conductors have better thermal stability compared to aluminum conductors, and the current rating is also one level higher, which means that a 10 square millimeter copper conductor is equivalent to a 16 square millimeter aluminum conductor. Copper also has better corrosion resistance, tensile strength and oxidation resistance than aluminum.
The “Specification for acceptance and construction of busbar devices of electrical equipment installation engineering” clearly stipulates: When busbars overlap busbars, busbars with branch lines and busbars with electrical terminal connections, the treatment of the overlapping surface must meet the following requirements :
1. Copper on Copper:
In external environments, in conditions of high temperature and humidity, or in internal environments with corrosive gases to the bus, tin plating must be applied; in dry indoor environments, direct connection is possible.
2. Aluminum to aluminum:
Direct connection.
3. Copper in Aluminum:
In dry indoor environments, the copper conductor must be tinned. In external or internal environments where the relative humidity of the air is close to 100%, a copper-aluminum transition plate must be used, and the copper end must be tinned. Similarly, when connecting copper cables to aluminum cables, copper-aluminum connectors can be used, and when connecting copper cables to aluminum wires, copper-aluminum terminals can be used, with the end tinned copper, etc.
V. When selecting electrical wires and cables, attention should generally be paid to choosing the type and specifications (conductor cross-section) of wires and cables
1. Selection of types of electrical wires and cables
- When selecting wires and cables, consider purpose, placement conditions and safety;
- Depending on the purpose, you can choose power cables, aerial insulated cables, control cables, etc.;
- Depending on the placement conditions, you can choose general plastic insulated cables, steel tape armored cables, steel wire armored cables, anti-corrosion cables, etc.;
- Depending on the safety requirements, you can choose flame-retardant cables, flame-retardant cables, halogen-free flame-retardant cables, fire-resistant cables, etc.
2. Selection of electrical wire and cable specifications
When determining specifications for the use of wires and cables (conductor cross-section), selection conditions such as heating, voltage loss, economic current density, and mechanical strength must generally be considered.
Based on experience, for low-voltage power lines with larger load currents, the cross section is generally selected first based on the heating conditions, and then the voltage loss and mechanical strength are checked; for low voltage lighting lines, which have higher voltage level requirements, the cross section can be selected first based on the allowable voltage loss conditions, and then the heating conditions and mechanical strength are checked.
Although aluminum core cables are cheaper, copper cables have notable advantages in the field of cable power supply, especially underground cable power supply. The use of copper core cables for underground power supply has characteristics such as low accident rate, corrosion resistance, high reliability and convenient construction and maintenance.
