Analysis of the reasons for the problem of small laminated inductance in high-voltage insulated copper tube busbars

05.16,20230

Brief Introduction

Due to the use of tubular conductors, the cross-sectional coefficient of the busbar is large and the mechanical strength is high. Therefore, it can be arranged with a large span while reducing the number of busbar supports. Under a short-circuit current of 50kA, the suspended span of the Φ 100 × 5mm copper busbar can reach 9 meters. With the support of the busbar bracket, the busbar span can reach 13 meters. The fully shielded insulated copper busbar uses hollow copper tubes as conductors. The outer surface of the copper tube consists of a thermal insulation layer, a pressure equalization shielding layer, an insulation waterproof layer, a grounding shielding layer, an outer insulation protective tube layer, and an anti ultraviolet insulation three color sheath outer protective layer. The main insulation is made of polytetrafluoroethylene material, the pressure equalization layer (shielding layer) is made of woven copper mesh, and the insulation sheath is made of polyolefin polymer material. The structure of the fully insulated shielded tube busbar is somewhat similar to the outer structure of a cable, and the busbar operates safely and reliably in a sealed and insulated environment. Insulated copper tube busbar is essentially a busbar product that uses copper tubes as conductors and external insulation. Correspondingly, there is also an insulated aluminum tube busbar. It is called "tubular cable" abroad. Insulated copper tube busbars have characteristics such as high current, up to 12000A, high mechanical strength, good insulation, and wide applicability, so they are increasingly recognized and accepted by customers. Its advantages such as small footprint, large load-bearing capacity, high installation coefficient, and easy maintenance have been accepted by most users. The laminated power tube bus is stacked together in the form of thin and wide copper.

What causes the laminated inductance of the busbar to be small? Copper tube bus is a type of bus mainly used for current transmission in high current operating places such as power, petrochemical, steel, new energy, urban rail transit, etc. The advantages of small footprint, large load-bearing capacity, high installation coefficient, and convenient maintenance have been widely accepted by users. The laminated power tube busbar is isolated between layers by stacking high insulation strength materials in the form of thin and wide copper. In order to reduce the mutual inductance between busbars, the distance between busbars is relatively uniform. The position required for each layer of copper strip is reliably insulated from other layers, allowing different potentials to be exposed on the same plane, which is more convenient than the main current.

All components in the circuit are connected to it, and according to electromagnetic field theory, the superimposed power bus makes the connector a flat cross-section. The thinner and wider the connection under the same section, the smaller the parasitic inductance. The currents on adjacent wires are opposite, and magnetic field offset can also reduce parasitic inductance. Igbt, rectifier module, heat sink, and capacitor are composed of a stacked power bus. The connection between the stack bus and the device is made through different terminals and connectors, so the contact resistance between the contact surface and the bus is very small, and parasitic inductance is reduced by orders of magnitude. Recommended reading: Main performance of copper tube busbar

There are three situations that can change the inductance: the position around the positive and negative busbars of the current will affect the magnetic flux around the current, thereby changing the inductance. The magnetic flux of two parallel conductors is different from that of a single conductor.

Reverse will cancel each other out, flux research has changed, and inductance has undergone significant changes. If the working current passes through an object and its fixed magnetic circuit object is placed in a system sealed magnetic flux metal box, there will be no induction outside because these magnetic target objects are blocked by the metal box. The copper tube busbar manufacturer believes that this is the case in China. Perhaps we can calculate that the inductance exists due to economic current. If the current data cannot offset the inductance, it cannot be changed. In fact, the existence of inductance is due to the magnetic flux of the control circuit current, which varies with the main direction of the current, the position and shape of the conductor. Once the magnetic flux changes, the inductance will be altered.

A tubular bus is a power line within a power station that connects various motors and appliances, transmits current and electricity, and distributes power through distribution devices. Due to the minimal skin effect of busbars, which improves flow rate, many people now use busbars. When the busbar attacks a short-circuit fault, a huge force effect will be generated due to the short-circuit current being many times greater than the normal operating current.

Installation of low-voltage bus duct

1.1 Vertical installation of low-voltage bus duct

At that time, the use of low-voltage bus ducts in the power system mainly involved vertical installation methods. In the vertical installation of low-voltage bus ducts, it was necessary to grasp the fundamental and critical links well, and promote their strong and reliable application function in subsequent practical applications. Firstly, in the vertical installation of low-voltage bus ducts, it is necessary to ensure that their installation orientation is clear and can be strictly analyzed according to the planning plan, combined with the practical environment of the construction site, to ensure that their installation orientation can be more accurate and reflect strong practical benefits. Especially for some relatively messy areas, it is necessary to clarify the installation orientation of low-voltage bus ducts to ensure that they can form a more ambitious application value in the vertical shaft. In addition, in order to improve the operational effectiveness of low-voltage bus ducts in the power system, it is necessary to strictly control the fixed links and promote the strong fixation of low-voltage bus ducts. The installation of flanges and tension spring brackets can be used for effective fixation, which can promote their reliable performance in long-term operations, better cope with the constraints caused by thermal expansion and contraction, minimize possible corrosion and adverse disturbances, and ensure their good use.

In the production process of dense bus ducts, the important raw material is the conductor. The choice of conductor material directly affects the price of fine busbar tubes. The function of the conductor is directly related to the performance indicators of the fine busbar tube. The selection of internal conductors is particularly important for qualified dense busbar trunking products to meet user requirements and play a role in power transmission and distribution. The conductor used is high-quality T2 electrolytic copper, and its motor can be much better than ordinary brass copper.

Comparison of Copper and Aluminum Conductor Metal Materials: Copper has a density of 8.9g/cm3, while aluminum has a density of 2.7g/cm3; The conductivity of copper is second only to silver, and its IACS value is 100% (standard annealed electrolytic copper standard value). The IACS values of high-purity aluminum (99.996%) and industrial pure aluminum (99.5%) are 64.94% and 59%, respectively, indicating that the conductivity of copper is about 35% -40% higher than that of aluminum. Copper has better chemical stability in the atmosphere. Aluminum is more vibrant, but adding trace alloying elements can enhance its chemical stability; Copper has better strength and hardness, while pure aluminum is slightly inferior, but aluminum alloys can achieve higher strength and hardness after heat treatment. Due to its lightweight, its strength is much greater than that of copper.

What are the advantages of bus ducts compared to traditional cables in power distribution systems?

The volume of the bus duct is smaller, saving space, while the cables need to be controlled in the distribution room.

Bus ducts can meet a rated current of up to 5000A, while cables require multiple parallel connections.

The sub interface of the bus duct can add sub circuits, and the cables must be laid from the distribution room.

The lifespan of bus ducts can reach 50 years and can be reused, while the lifespan of cables is relatively short and cannot be reused.

Bus ducts can be controlled from a position close to the equipment, while cables must be controlled in the distribution room

The bus duct is equipped with standard device brackets and does not require any other support; Cables must be laid using separate cable trays or pipelines.

The sub interface of the bus duct can add sub circuits; And cables are relatively expensive.

The above are the primary advantages of bus ducts in power distribution systems, so wires and cables are gradually being replaced.

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