1. Application Scope

The GFM series high-voltage enclosed busbar is a new type of busbar channel jointly developed by our factory and several domestic research institutions. It is applicable to power supply systems with an AC frequency of 50-60Hz, a voltage range of 3.6kv - 40.5kv, and a rated current of 400 - 6300A.  

2. Structural Characteristics and Technical Parameters

Structural features:
1) This series of enclosed busbars possess excellent short-circuit resistance performance. Due to the protection provided by an aluminum (or weak magnetic steel plate) enclosure (available for selection for currents below 2500A), it can effectively reduce the structural heating caused by eddy currents or circulating currents, lower the temperature of the enclosed busbar enclosure, decrease electrical energy loss, increase the current-carrying capacity, and reduce the electrodynamic force.

2) The structure of this series of enclosed busbars is advanced. The installation and maintenance holes can be freely set at the top or bottom of the busbar slot. For large current indoor enclosed busbars, ventilation louvers are provided on both sides and at the bottom of the shell to enhance heat dissipation and reduce temperature rise.

3) Double insulation and multi-point connection grounding of the shell are adopted to significantly reduce the maintenance workload and significantly improve the safety performance.

4) Wave tube expansion joints are used for installation, which is simple and can achieve two degrees of freedom of adjustment in both horizontal and vertical directions. This not only meets the expansion requirements caused by temperature changes and thermal expansion and contraction, but also compensates for errors caused by foundation settlement.

5) To address the negative impact of vibrations generated by the operation of transformers, generators, and distribution cabinets on the enclosed busbars, soft connections or copper braided belts are used at the connection points with the enclosed busbars. Rubber pads are added between the shells to reduce vibrations; for the enclosed busbar itself, shock absorbers are installed in the system to provide elastic support for porcelain bottles and conductive rails, effectively avoiding mechanical vibrations and seismic waves caused by the shells that may damage the enclosed busbars.

6) The heat transfer of the enclosed busbars mainly relies on radiation. To make good use of radiation heat, light gray paint is sprayed on the outer surface of the enclosed busbars to reduce absorption of visible light; black paint is sprayed on the inner surface to enhance the radiation of internal heat to the shell and prevent corona.

7) To avoid accidental condensation caused by temperature changes in winter outdoors and indoors, wall-mounted bushings are set at the connection points, completely isolating the outdoor and indoor enclosed busbars; when installed vertically, the flange is on the inside, and when installed horizontally, the flange is on the outside.

8) To avoid resonance frequencies that may cause resonance, and to reduce the electrodynamic force acting on the busbar, the span between insulators is reasonably determined, and the type, specification, and strength grade of the insulator are selected.

9) To monitor the temperature of the detachable joints, sealed observation windows are set at the connection outlets of the transformer, generator, and distribution cabinet with the enclosed busbars. Temperature can be directly measured using temperature stickers or infrared temperature measurement devices to monitor the operation of the busbar system.

10) To facilitate users, current transformers can be installed at the generator outlet and the primary side of the excitation transformer according to user requirements, making it convenient for users to detect current. 

Main technical parameters

1) Insulation resistance: The insulation resistance value of each closed busbar unit should be greater than or equal to 1000 MΩ (measured with a 2500V megohmmeter).

2) Dielectric strength: Each closed busbar unit undergoes a 1-minute power frequency withstand voltage test before leaving the factory. The values of power frequency withstand voltage and lightning impulse withstand voltage are shown in the table. 

3) Grounding system: Compliant with the requirements of IEC 364-5-54 for grounding systems.

    4) Protection class: Indoor type: IP40; Outdoor type: IP43, IP54.

    5) Load performance: Under the rated current, the temperature rise of the enclosure complies with the requirements of GB763-90 "Thermal Generation of High-Voltage Electrical Appliances during Long-Term Operation".

    6) Short-circuit performance: The dynamic thermal stability test complies with the requirements of GB2706-89 "Test Methods for Dynamic Thermal Stability of High-Voltage Electrical Appliances".
The enclosed busbar is widely used in power plants, industrial and mining enterprises, etc., as the electrical connection between generators and main transformers, transformers and high-voltage distribution cabinets, and the main circuits of high-voltage equipment. The supply length is set at 2m per section, and the length of each section is generally not more than 3m.