Why Aluminum Lines in Electrical Wires Are More Likely To Catch Fire Than Copper Lines

1, load power:

 the same cross-sectional area of copper wire and aluminum wire wire, copper wire load power is greater than aluminum wire.

2. flexibility: 

Copper wire is more flexible, easy to bend and strong fatigue resistance. Aluminum wires are relatively easy to break when bending.

3, stability: 

aluminum wire is very easy to oxidize, so that the resistance becomes large, reduce the load of the wire, prone to safety problems. But the copper core has excellent stability.

4, resistivity: 

the resistivity of copper wire is small, compared with the resistivity of aluminum wire is lower than 1.68 times, resulting in the power loss of aluminum wire, heat is more serious, which affects the utilization rate of electricity.

5, price:

 the price of aluminum wire is much cheaper than copper wire, the price of copper wire is generally many times of aluminum wire, copper wire is heavier than aluminum wire. As you know, the risk of aluminum wire fire is much greater than that of copper wire, aluminum wire fire is not in the aluminum wire itself but in the aluminum wire connection. Compared with copper wire, the reasons for the high fire danger of aluminum wire connection are as follows: 

The surface of aluminum wire is easy to oxidation in the air where the conductor surface has more or less membrane resistance. If the membrane resistance causes the connection to overheating, and the overheating increases the membrane resistance, the more conductive situation becomes, and the kind of overheating in the aluminum wire connection is particularly serious. This is because even if the surface of the aluminum wire is polished, it can be exposed to air for a few seconds and immediately form an alumina film. Although its thickness is only a few microns, but it has a very high resistivity, thus presenting a large membrane resistance. Therefore, in the construction of aluminum wire connection, it should be applied immediately after scraping the aluminum wire surface to block the contact between the aluminum wire connection surface and air, otherwise it will increase the contact resistance.

1. . High expansion coefficient The expansion coefficient of aluminum is as high as 2310-6 / ℃, 39% larger than copper and 97% larger than iron. When the aluminum wire is connected to the two metal conductors and passes through the current, the connection point is heated by the presence of contact resistance. All three conductors expand, but aluminum expands more than copper and iron, thus squeezing the aluminum wire. After the line is cut off and cooled, the aluminum line is slightly flattened and can not be completely restored to its original state, so a gap at the connection and an alumina film is formed because of entering the air, so that the contact resistance increases. The next time the power is on, the heat will be more intense, making the situation worse, serious may be due to abnormal high temperature or electric sparks and ignite the fire. For this reason, the aluminum conductor should be connected with copper and iron conductors. The connection of small cross-section area (not more than 6mm 2) aluminum wire should be spring compression cap, so that whether the connection is electrified, heat or not, the connection contact surface is under the spring pressure, so that the air and moisture can be entered, so as to keep the connection well conductive.

2.  easy to appear electrolytic corrosion effect if there is an acidic or alkaline liquid between the two metals with different potentials, then the two metals will form a local battery. The potential of aluminum is-0.78V, while copper is-0.17V. This local battery is formed when there is salty water between the aluminum conductor and the copper conductor. Ionization will make the low potential aluminum conductor corrosion and increase the contact resistance.

3. , easy to be hydrogen chloride corrosion for PVC insulated aluminum core wire, cable, there may be another problem. In order to prevent the decomposition of hydrogen chloride gas from PVC insulation, a stabilizer is added to prevent the decomposition of hydrogen chloride in PVC insulation. However, when the line temperature exceeds 75℃, such as the line overload or the connection temperature is too high for other reasons, the stabilizer can no longer prevent the formation of hydrogen chloride, which will corrode aluminum, which will also increase the risk of contact resistance and fire.