Aluminum core cable conductor connection method

Aluminum and copper cores are commonly used cable conductors, but they cannot be connected directly. The main reasons are:

(1) When the copper and aluminum core conductors are directly connected, the metal contact surface can easily form an electrolyte under the action of moisture, carbon dioxide, and other impurities, thereby forming a primary battery having aluminum as a negative electrode and copper as a positive electrode, so that the aluminum can be electrified. Corrosion causes increased contact resistance at the junction of copper and aluminum cores.

(2) Since the modulus of elasticity and thermal expansion coefficient of copper and aluminum are very different, after many times of cold and hot cycles (power and power off) in operation, a large gap will be created at the contact point and affect the contact. Also increases the contact resistance.

(3) The increase of contact resistance will cause the operating temperature to rise, and the corrosion oxidation will increase at high temperatures. After the vicious cycle, the connection quality will be deteriorated. Finally, the contact point will be overheated, smoked, burned, and other accidents.

The "Code for the Construction and Acceptance of Busbar Installations for Installation of Electrical Installations" clearly stipulates that copper and aluminum core conductors should be connected using copper-aluminum transition joints, and if copper pressure pipes are used, the inner wall of the busbars must be tin-plated. The industry standard stipulates that the DC resistance of the copper-aluminum transitional connection pipe should not be greater than 1.2 times the DC resistance of the aluminum conductor of the same length and section.

After connecting aluminum conductors with different cross-section conductors, the problem is that the connection of copper and aluminum core conductors with different cross-sections is more complicated. For conductors of the same type in construction, the method of removing or adding conductor monofilaments may be used to solve the problem. However, firstly removing or adding the conductor monofilament causes local stress to be large in the crimping of the conductor connectors, and the long-term operation may result in a large contact resistance. .

Secondly, removal or addition of conductor monofilaments usually forms sharp corners or sharp edges, which may damage the intermediate joints. At this time, the external joints are in tension and cause mechanical damage. At the same time, sharp corners or sharp edges will also cause electric field distortion at joints. , planting hidden dangers for the accident. The connection of conductors of different cross-sections can only be done by using special conductors of different internal diameters. If copper and aluminum conductors are connected, only copper-aluminum transitional connection tubes can be used.

Connection of Aluminum Core Cable Conductors Aluminum core cable conductors are generally crimped with aluminum connectors. However, they are actually crimped with tinned copper connectors. In the past 20 years, copper core cables have been used as the main power systems. At present, the crimping tools deployed by the cable installation department are mainly crimped copper core cables. At present, crimping tool manufacturers do not manufacture aluminum core cables. Crimping tool.

The point pressure method of crimping the aluminum core cable has the advantages of less pressure, easy to make the metal surface penetrate the contact surface of the local crimping place, and damage the aluminum core wire and the oxide film on the surface of the connecting pipe, but the connecting pipe is easily deformed after crimping.

The advantages of the confining pressure method for the crimped copper core cable is that the surface shape of the connecting pipe after crimping is relatively flat and does not deform, and it is easy to solve the problem of electric field concentration at the connecting pipe.

GB/T14315 specifies that the aluminum pipe is smaller than the copper pipe by one cross-section pipe whose outer diameter is the same as that of the copper pipe1. For example, the 240mm2 aluminum pipe and the 300mm2 copper pipe have the same outer diameter. Therefore, when the copper and aluminum conductors use the same series of crimping tools, the pressure die of the aluminum pipe crimped to the same section is one size greater than that of the copper pipe of the same section.