With the emergence of modern engineering equipment and devices, the electricity consumption of various industries has increased rapidly, especially in many high-rise buildings and large factory workshops. Traditional cables, as transmission lines, can no longer meet the requirements in high current transportation systems. The parallel use of multiple cables has brought many inconveniences to the construction and connection of on-site equipment. Plug in busbar trunking, as a new type of distribution wire, has emerged and fully demonstrated its effectiveness in high current transportation. Due to the use of new technologies and processes, the touch resistance and temperature rise at the connection between the two ends of the busbar trunking and the junction of the distribution port have been greatly reduced, and high-quality insulation materials have been used in the busbar trunking, thereby advancing the safety and reliability of the busbar trunking and making the entire system more perfect.

1. Select qualified products from legitimate enterprises:

The busbar trunking should use products with 3C mandatory certification symbols and have type test reports. There are many manufacturers in China who produce busbar trunking, and the production methods are mostly handmade. They are mainly concentrated in Jiangsu and Zhejiang provinces, and Yangzhong, Jiangsu is the hometown of busbar trunking and cable trays. When making a purchase, it is necessary to conduct a thorough investigation of the manufacturer's production scale, skill level, worker nature, and production environment, especially the production environment. Because if insulation treatment is carried out in an unclean space, there may be some conductive particles in the insulation layer, and there is no contact at the beginning of the work, but over time it will cause insulation damage.

2. According to the conductor material of the bus duct

At present, the main products are copper bars, aluminum bars, and copper aluminum composite, with significant price differences. In addition to emphasizing its purity, attention should also be paid to the mechanical function of the material after bending. Here we will focus on copper aluminum composite. The interface strength of copper aluminum composite directly affects its processing function and application reliability. Copper aluminum composite busbars do not bubble or show obvious orange peel when bent at 90 °, and do not show copper aluminum delamination when punched or sheared. Only then can they be used in electrical equipment to meet the requirements of interface bonding strength. The interface bonding strength varies depending on the manufacturing process. Using mechanical pressure to press and composite copper and aluminum can only activate the interface atoms to form atomic bonds. After heat treatment and dispersion, point bonding becomes surface bonding, but the dispersion depth is thin and the interface bonding strength is not high. Under specific processing conditions, copper and aluminum are fused to form a uniformly bonded interface with a certain thickness of composite layer, achieving high interfacial bonding strength.

After many experiments and finite element analysis, it has been found that when the copper layer section accounts for 20% of the total section, the conductivity is much higher due to the skin effect, and the hardness is enhanced and the lifespan is increased. The proportion of copper layer section is confirmed to be related to the proportion of copper aluminum composite busbar. When the copper layer section accounts for 10%, 15%, and 20% of the entire section, their proportions are 3.32, 3.63, and 3.94 (g), respectively/㎝3) . The simple method for detecting the cross-section of a copper layer is to take a sample, weigh it, calculate the sample volume, and determine the specific gravity.

3. Select the section of the bus duct

Generally, the busbar cross-section should be selected based on the long-term operating current. And verify the short-term thermal stability and dynamic stability of the bus duct under short-circuit cable conditions. Due to factors such as resistance in conductors and the AC current trend when multiple conductors are in close proximity, heating can occur when current passes through the bus duct. The allowable temperature for heating during long-term operation of copper and aluminum bare bus ducts is 70 ℃. However, when the touch surface is reliably covered with tin (such as ultrasonic tinning), the allowable temperature advances to 85 ℃. Constrained by this continuous heating allowable temperature, bus ducts of different materials and sections provide corresponding long-term allowable current values. When selecting a bus duct section, the actual long-term operating current of the bus duct should be lower than the long-term allowable current value of the selected section bus duct. In situations where the average annual load is high and the bus duct is long (such as outdoor distribution equipment bus ducts), the bus duct is generally selected using the economic current density method. Economic current density refers to the current flowing through a unit cross-sectional area of a bus duct, taking into account the losses of the bus duct, the annual repair and depreciation costs of the bus duct and its associated equipment. The cross-sectional area of the bus duct is obtained by dividing the economic current density by the long-term operating current that does not include overload. The cross-sectional area of the bus duct selected by the economic current density method is generally larger than that selected by the long-term operating current.

4. Maximum temperature increase of bus duct

What is the maximum temperature increase of bus duct? The maximum temperature increase of a bus duct refers to the temperature increase obtained by subtracting the ambient temperature from the stable high temperature of the bus duct when it operates at full load with rated current. It is generally indicated by K. During busbar planning, temperature rise limit tests are conducted. Temperature rise limits the current carrying capacity of the busbar, causing a reduction in its lifespan, an increase in electrical energy loss, and a decrease in voltage. This also affects the surrounding environment temperature, accelerates the aging of insulation materials for surrounding equipment, and may even lead to safety accidents.

In China, fire accidents caused by electrical hazards account for over 60% of all fire accidents. The perpetrators of electrical fire accidents include cables, wires, high and low voltage complete sets of equipment, transformers, bus ducts, electrical components, etc. Most of them are caused by long-term temperature rise and heat generation, leading to insulation material aging and short circuits, resulting in fire accidents.

The maximum temperature increase can be said to be a safety skill parameter for bus ducts, and it is also an important goal that reflects the overall function of bus ducts. Users can also understand the following issues from the temperature rise of the bus duct: ① Purity of copper bars: The copper content is directly related to the electrical resistivity of the conductor. The higher the electrical resistivity of the same conductor specification, the naturally higher the temperature rise. ② The cross-sectional area of a conductor: A conductor with the same structure and skill, and the same copper content, has a smaller cross-sectional area and naturally higher temperature rise. ③ The heat dissipation function of bus duct: The insulation material and shell structure have poor heat dissipation, resulting in naturally high temperature rise. ④ The quality of the connector structure: If the connector touch is not good, the temperature rise will also be high.

5. Select bus duct based on current capacity

Based on the planned current capacity, selecting corresponding busbar products can prevent waste and reduce costs.

6. Select bus ducts based on the application environment and equipment methods

① When selecting busbar trunking, the application environment should be taken into consideration, and the selection of the enclosure protection level of the busbar trunking should comply with the following rules: 1. For indoor dedicated clean places, IP30 or above level should be selected. 2. Indoor ordinary places should be selected with a rating not lower than IP40. 3. For indoor places with splash proof requirements, choose a level not lower than IP54. 4. For indoor humid places or places with anti spray requirements, choose IP65 or above rating. 5. For places or outdoors with anti-corrosion requirements, use fully enclosed resin cast bus ducts with IP68 rating.

② According to different equipment methods, when selecting bus ducts, attention should also be paid to: if the bus duct is horizontal and the bracket can be set according to the requirements, a bus duct with a length of about 3m should be selected. When the distance between brackets is 6m or more, ultra long bus ducts should be selected. When constructing bus ducts along flat equipment in different shapes, it is advisable to choose bus ducts with rectangular shells. When installing equipment along a curved surface, it is advisable to use resin cast bus ducts or cylindrical bus ducts. When the bus duct is installed vertically, it is advisable to use a bus duct covered with insulation or resin casting, and the insulation material should be selected from materials suitable for long-term operation with a temperature not lower than 130 ℃. To prevent chimney effect, when using air insulated bus ducts, fire-resistant intervals should be set between each unit inside the bus duct casing.

③ When used for emergency power supply, fire-resistant and waterproof bus ducts should be selected.