1. main reasons for the fuse of copper aluminum transition terminal

At present, copper-aluminium transition terminals are mostly used in outdoor cable installation, and copper-aluminium transition terminals are also the main faults. Therefore, the author takes eight common copper-aluminium transition terminals used in outdoor cable installation of Nanyang Power Supply Company as an example to explain the main reasons for cable terminal fusing. This is the following analysis.

1.1 the quality of the terminals is not up to the national standard.

Taking eight common copper-aluminium transition terminals as examples and comparing them with national standards, we find that there are some problems in the quality of current terminals: too large screw holes reduce the contact area of terminals, and the fixed bolts are easy to loosen; the outer diameter of terminals becomes thinner, and the tube wall becomes thinner; Shallow, wire insertion part is shorter; copper length of copper-aluminum transition part is shorter; the width of the contact part is reduced, so that the contact area is reduced; the thickness of the contact part is reduced.

1.2 the installation process is not precise.

In the process of installation, the connection between the terminal and the clamp is also one of the conditions to ensure safe power supply. After careful examination of the outdoor cable head terminal fusing, it is found that the contact part between the terminal and the clamp has a melting point shape, which is also the corrosion of two different metal contacts of copper and aluminium. There are second reasons for the overheating of the contact surface due to the poor contact of the battery.

1.3 uneven load distribution

In the process of power transmission, if the load of each phase is uneven, the load of one phase or two phases will be lower, and the load of the other phase or two phases will be higher. If the load current is too large for a long time, it will increase the failure probability of cable lines, accelerate insulation aging, shorten the service life of cables, and cause external connection of terminals. The danger of overheating and overloading of cable lines is obvious.

1.4 lightning strikes and others

In addition to the above three reasons, lightning strikes and line faults in summer are also another cause of cable outdoor terminal fusing.

2 countermeasures and measures

2.1, strict purchase and selection of equipment.

Firstly, when using terminals, the constructors should boycott spare parts that do not conform to the national standards, refuse to use them and close the use of materials. Second, the material department should make good use of the way to purchase goods, organize procurement personnel to visit the grass-roots level more to understand the use of the goods in the installation process, collect timely opinions on their use, select cable accessories from national designated manufacturers, select good terminals and fittings, and avoid unqualified quality standards in operation. Problems arise.

2.2, strict installation process.

Skills training should be carried out to improve the installation and operation level of employees through skills training and on-the-job training. The installation process must be strictly in accordance with the installation process. For example, when installing terminal, the contact surface of terminal should be polished and coated with conductive paste (or vaseline) to make good contact between terminal and lead clamp, to meet the requirements of connection strength and electrical performance, and to reduce the chance of heating.

2.3 allocate electricity load rationally and set up regular load measurement system.

Because the distribution line sometimes extends several kilometers, or even tens of kilometers, we should consider the power and capacity of the user's electrical equipment, pay attention to the field investigation, formulate the plan of power consumption should be ahead of time, reasonably distribute three-phase load, not only consider the economy of power consumption, but also realize the safety of power consumption. Operating departments should regularly measure and monitor the load of cable lines, adjust and transfer the load urgently under special circumstances to ensure that the cable runs in accordance with the prescribed carrying capacity.

2.4, pay attention to other measures.

Although many operating cables are hidden and less likely to suffer direct lightning strikes, after all, some cables are connected with overhead lines or other electrical equipment, or will be affected by the intrusion of lightning currents. Therefore, we must take more effective lightning protection measures to ensure electricity. Safe and stable operation of cable. In addition, the People's Republic of China's Electric Power Law and Regulations on Protection of Electric Power Facilities should be widely publicized to arouse great attention from all walks of life and the general public. Regular inspection should be carried out on the distribution lines led by cables, trees on both sides of the distribution lines should be regularly repaired, and facilities affecting the safety of the lines should be quantified and rectified. To ensure that the lines around the barrier free, reduce the external fault factors and natural hazards of distribution lines.