Dense bus ducts and air-insulated busbars differ significantly in their structural design, directly impacting their insulation methods, heat dissipation efficiency, space utilization, and applicable scenarios. From conductor arrangement and insulation medium to shell structure, both designs revolve around core functional requirements, forming complementary technological approaches.
Dense bus ducts employ a "sandwich-style" tightly stacked conductor arrangement, with no gaps between phases. The conductors are in direct contact and isolated by insulation material. This design significantly reduces the lateral dimensions of the busbar, making its structure more compact. In contrast, air-insulated busbars require gaps between conductors, using air as the insulation medium, supplemented by insulation material for double protection. Their conductor arrangement resembles a grid, and the gap size directly affects insulation performance; therefore, strict control of spacing is necessary to avoid the risk of phase-to-phase short circuits.
The choice of insulation medium is the core difference between the two structures. Dense bus ducts use organic insulation materials, such as flame-retardant cross-linked polyethylene heat-shrink tubing, directly wrapping the conductor surface to form a continuous insulation layer. This design not only provides stable insulation performance but also effectively retards flames and releases no toxic gases when exposed to fire. Air-insulated busbars rely on air as their primary insulation medium, with conductors fixed by insulating supports or partitions, creating independent air ducts within the casing. While air insulation is less expensive, it necessitates increased conductor spacing to ensure safety, leading to increased volume.
Differences in casing design further enhance functional characteristics. Dense bus ducts typically use metal plates (such as steel or aluminum) for their casings, tightly fitted to the conductors to form heat dissipation channels. The casing also serves as the PE (protective earth) conductor, reducing material usage and improving the continuity of the protection circuit. The joints are designed with an enlarged structure to accommodate double-connecting copper busbars and insulating bolts, maximizing the contact area. Air-insulated busbars, on the other hand, must balance mechanical strength and ventilation requirements, often employing aluminum alloy or steel grid structures with ventilation holes for air convection. While their shape is uniform from top to bottom, their overall volume is significantly larger than dense busbars due to conductor spacing.
The difference in heat dissipation efficiency stems from fundamentally different structural designs. In dense bus ducts, the conductors are in direct contact with the metal casing, allowing heat to be rapidly conducted to the external environment, resulting in high heat dissipation efficiency. Some designs also add heat dissipation fins to the outer casing to further enhance heat exchange capabilities. Air-type bus ducts, on the other hand, rely on air convection for heat dissipation; heat must first be conducted to the air between the conductors and then exhausted through ventilation holes in the casing. This process is significantly affected by airflow speed and ambient temperature, resulting in relatively low heat dissipation efficiency, especially prone to localized overheating in long-distance or high-load scenarios.
In terms of space utilization, dense bus ducts have a clear advantage due to their compact structure. Their small size and light weight make them suitable for vertical installation in confined spaces or electrical shafts in high-rise buildings, significantly reducing the floor space required. Air-type bus ducts, due to conductor spacing and ventilation requirements, are larger and require ample installation space, especially placing higher demands on building structures when laid horizontally. However, their modular design allows for flexible length adjustments by adding or removing conductor segments to adapt to different scenario requirements.
In terms of safety design, dense bus ducts employ a fully enclosed structure, effectively isolating dust, moisture, and foreign object intrusion, reducing the risk of failure. Their insulation materials are moisture-proof and corrosion-resistant, making them suitable for harsh environments. While air-insulated busbars enhance safety through double insulation, their open structure still poses a risk of foreign objects falling in, requiring regular maintenance and cleaning. Furthermore, air-insulated busbars may create a chimney effect in a fire, accelerating its spread, while dense busbars, due to their flame-retardant materials, can slow the fire's spread.
This differentiation in application scenarios stems from the combined effects of their structural characteristics. Dense busbars, with their high current carrying capacity, low loss, and compact design, are the preferred choice for high-power transmission scenarios such as industrial plants, data centers, and commercial complexes. Their convenient branching and flexible branch expansion meet dynamic load requirements. Air-insulated busbars, on the other hand, are more suitable for humid environments such as underground tunnels, shafts, or laboratories due to their excellent moisture resistance. Their low cost and ease of maintenance also make them a viable option for small to medium-sized load applications.
