1. Application
The GGD type AC low-voltage fixed switch cabinet is suitable for the AC 50Hz, rated working voltage 380V, rated working current up to 3150A power distribution system of power users such as power plants, power stations, and industrial and mining enterprises. It is used for power conversion, distribution and control of power equipment.
The GGD type AC low-voltage switch cabinet is a new type of low-voltage switch cabinet designed based on the requirements of the majority of power users and design departments, adhering to the principles of safety, economy, rationality and reliability. The product features high segmentation capability, good dynamic and thermal stability, flexible electrical scheme, convenient combination, strong series and practicality, novel structure, and high protection level, etc. It can be used as an updated and replaced product for low-voltage complete switchgear.
The GGD type AC low-voltage switch cabinet complies with standards such as IEC439 "Low-voltage Enclosed Switchgear and Controlgear" and GB7251 "Low-voltage Enclosed Switchgear and Controlgear".
2. Operating Conditions
2.1 The ambient air temperature shall not exceed +40℃ and shall not be lower than -5℃. The average temperature over 24 hours shall not exceed +35℃.
2.2 For indoor installation, the altitude of the usage location shall not exceed 2000m.
2.3 The relative humidity of the ambient air shall not exceed 50% at the maximum temperature of +40℃. At lower temperatures, a higher relative humidity is allowed, and the influence of occasional condensation due to temperature changes should also be considered.
2.4 The inclination angle of the equipment installation relative to the vertical plane shall not exceed 5%.
2.5 The equipment should be installed in a place without severe vibrations and impacts, as well as in a location where corrosive effects on electrical components are not sufficient.
2.6 When there are special requirements from the user, they can negotiate with the manufacturer for solutions.
3. Electrical Performance
3.1 Main Circuit Design
The main circuit of the GGD cabinet has 129 schemes, totaling 298 specifications (excluding the schemes and specifications derived from functional changes and control voltage variations of the auxiliary circuit). The main circuit schemes were selected based on the opinions of various design and usage departments. Schemes required by power plants have been added, with the rated current increased to 3150A, suitable for distribution transformers of 2000KVA and below. In addition, to meet the needs of reactive power compensation, GGG1 and GGG2 capacitor compensation cabinets have been designed, with 4 main circuit schemes and a total of 12 specifications.
3.2 Auxiliary Circuit Scheme
The design of the auxiliary circuit is divided into two parts: the power supply and load scheme and the power plant scheme. There is sufficient space in the GGD cabinet to install secondary components. Meanwhile, NLS has also developed and produced the dedicated LMZ3D type current transformer to meet the needs of power plants and special users for installing relay protection.
3.3 Main Busbar
When the rated current is 1500A or less, a single-row busbar is used; when the rated current is greater than 1500A, a double-row busbar is used. Our company manufactured prototype machines in accordance with these regulations and passed the type test. The connection surfaces of the busbars are all treated with tin plating process.
3.4 Selection of Electrical Components
a. The GGD cabinet mainly uses advanced electrical components that are already available in large quantities domestically, such as RMW, RMM, KFW, KFM, CW, CM, SM, TM30, and DZ20.
b. The HD13BX and HS13BX type rotating-operated knife switches are specialized components designed by NLS to meet the unique structure requirements of GGD cabinets. They have changed the original operating method of the mechanism while retaining the advantages of the old products. They are a practical new type of electrical component.
c) If the design department selects more advanced and superior electrical components that meet the user's requirements, since the GGD cabinet has excellent installation flexibility, the installation process is unlikely to encounter difficulties due to the replacement of electrical components.
d) To further enhance the dynamic stability of the main circuit, NLS has designed the ZMJ type combined busbar clamp and insulating support components specifically for GGD cabinets. The busbar clamp is thermoplastic molded from high-strength, flame-retardant PPO synthetic materials, featuring high insulation strength, good self-extinguishing performance, and a unique structure. It can be conveniently combined into a single busbar clamp or a double busbar clamp by adjusting the modular inter-blocks. The insulating support is a sleeve-type molded structure with low cost, high strength, and increased creepage distance, resulting in better safety.
4. Structural Characteristics
4.1 The cabinet body of the GGD type low-voltage switchgear adopts a universal cabinet form. The frame is assembled by local welding of 8MF cold-formed steel sections. The specialized accessories for the frame parts are supplied by a dedicated steel production factory to ensure the accuracy and quality of the cabinet. The components of the cabinet are designed based on modular source force, and there are 20 modules of installation holes. The general coefficient is high, enabling the factory to achieve production compatibility, thereby not only shortening the production and manufacturing cycle of the product but also improving work efficiency.
4.2 When designing the GGD cabinet, the issue of heat dissipation during operation was fully taken into consideration. Different numbers of heat dissipation slots were set at the top and bottom of the cabinet. When the electrical components inside the cabinet heat up, the heat rises and is discharged through the upper slots. Meanwhile, cold air continuously enters the cabinet from the lower slots through the bottom slots, forming a natural ventilation channel from bottom to top within the sealed cabinet, achieving the purpose of heat dissipation.
4.3 The GGD cabinet is designed in accordance with the requirements of modern industrial product styling. The cabinet body shape and the dimensions of each part are designed using the golden ratio method, making the entire cabinet elegant and modern.
4.4 The cabinet door is connected to the framework by a rotating shaft-type movable hinge. It is convenient for installation and disassembly. At the folded edge of the door, a curved rubber strip in the shape of a mountain is embedded. When closing the door, the embedded strip between the door and the framework has a certain compression stroke, which can prevent direct collision between the door and the cabinet body, thereby improving the protection level of the cabinet.
4.5 The instrument door equipped with electrical components is connected to the framework via multi-strand soft copper wire. The components installed within the cabinet and connected to the framework are secured with knurled screws, and the entire cabinet forms a complete grounding protection circuit.
4.6 The surface paint of the cabinet is made of polyester orange-brown enamel, which has strong adhesion and good texture. The entire cabinet has a matte color tone, avoiding the glare effect and creating a more comfortable visual environment for the duty personnel.
4.7 The top cover of the cabinet can be removed when needed, facilitating the assembly and adjustment of the main busbars on site. The four corners of the cabinet top are equipped with lifting rings, which are used for lifting and transportation.
4.8 The protection level of the cabinet is IP30. Users can also choose from IP20 to IP40 based on the requirements of the usage environment.
