When conducting tests on metal enclosed switchgear, the following points should be noted:
a. The busbars in the cabinet or in other compartments, due to the poor quality of the copper material (some manufacturers use aluminum as the conductor), have a high content of impurities, which results in a high material resistivity and may cause a significant temperature rise.
b. Magnetic field influence: For ferromagnetic materials, it is prone to generate eddy current heating, resulting in an excessive increase in the temperature of the conductive part. This phenomenon is more prominent in large current switch cabinets. Such situations occur frequently and generally, replacing ferromagnetic materials with stainless steel plates can avoid such problems.
c. The outlet cabinet has a large amount of heat generated by the fuse tube, which makes the temperatures at both ends of the terminals prone to exceeding the limit. Generally, for fuse tubes with a rated current of 100A or above, the temperatures at the terminals are likely to exceed the limit. In such cases, a common solution is to use a suitable fuse tube, or to adjust the terminals that fix the fuse tube. The fundamental solution lies in the quality of the fuse tube. If there is a good fuse tube available, such problems can be easily resolved.
d. The outgoing lines of the cabinet should be connected to cables. The cable terminals (allowing a temperature rise of 50K) are prone to be affected by the heat generated by the switch equipment, resulting in excessive temperature. Such situations occur frequently. The main reasons are that the main circuit resistance of the switch equipment is relatively large, causing significant heat generation, and some manufacturers use poor-quality cables, leading to excessive temperature.
e. Switchgear with a rated current of 3150 A or above is generally equipped with a fan to cool and reduce the temperature in the circuit breaker compartment and busbar compartment. However, some manufacturers have improper duct designs, resulting in the fan not functioning effectively and causing the internal temperature of the switchgear to exceed the limit. Such situations occur frequently and should mainly be addressed by improving the design of the cabinet or increasing the power of the fan.
f. The terminals of the current transformers in the switchgear exceeded the temperature limit due to quality issues with the transformers. The terminals coated with silver are allowed a temperature rise of 75K, while those coated with tin are allowed a temperature rise of 65K.
Problems to be noted in mechanical tests
During the assembly of the mechanism, due to poor fit, it is prone to cause uneven force distribution on the connecting rod, resulting in the rod breaking.
b. When the number of service cycles is high, under the condition that the main components of the equipment are operating normally, some small parts may become severely worn, resulting in the inability of the equipment to operate normally.
c. The failure of the opening and closing operations due to improper conversion caused by the quality issue of the auxiliary switch is mainly attributed to the quality problem of the auxiliary switch.
d. Some circuit breakers have poor stability and their mechanical characteristics during the life cycle tests reveal issues such as excessive bouncing, prolonged closing time, and failure to meet technical requirements for opening and closing speeds. These problems are more likely to occur in circuit breakers with spring mechanisms compared to those with electromagnetic mechanisms. In contrast, circuit breakers with permanent magnet mechanisms tend to have higher stability.
e. During the pressure resistance test after the lifespan test, it was found that the arc extinguishing chamber was leaking.
f. After conducting the life test, it was found that the loop resistance changed by more than 20%. This issue is related to the wear of the arc-extinguishing chamber contacts, and it is currently very rare to occur.
Post time: Mar-06-2026