GGD Low Voltage Switchgear

Main Circuit Schemes

The main circuit of the GGD cubicle is designed with 129 schemes and 298 specifications in total (excluding schemes and specifications derived from changes in auxiliary circuit functions and control voltages). The GGD low-voltage switchgear is designed in three types — GGD1, GGD2 and GGD3 — with rated current up to 3200 A, suitable for distribution transformers of 2000 kVA and below.

Namely:

• GGD1: 49 schemes, 123 specifications
• GGD2: 53 schemes, 107 specifications
• GGD3: 27 schemes, 68 specifications

The main circuit schemes were compiled after soliciting the opinions of a large number of design and user departments, and schemes required by power plants have been added. The rated current is increased to 3200 A, suitable for distribution transformers of 2000 kVA and below. In addition, GGJ1-GGJ2 capacitor compensation cubicles are designed to meet the needs of reactive power compensation, with 4 main circuit schemes and 12 specifications in total.

Auxiliary Circuit Schemes

The auxiliary circuit design is divided into two parts: power supply and consumption schemes and power plant schemes. There is sufficient space inside the GGD cubicle for installing secondary components.

Selection of Electrical Components

• ◇ The GGD cubicle mainly adopts relatively well-developed electrical components that can already be mass produced domestically, such as ME, DW15, DW17, DW45, CM1 and NM1; at the same time, on the principles of economy and rationality and with full consideration of feasibility, some still usable older products such as DZ20 are retained. Obsolete products are not selected.
• ◇ The HD13BX and HS13BX rotary-operated knife switches are dedicated components designed to meet the needs of the unique structure of the GGD cubicle; they change the operating mode of the mechanism while retaining the advantages of the older products, and are utility-model electrical components.
• ◇ If the design department selects new electrical components with better performance and more complete technology according to user needs, the GGD cubicle offers good installation flexibility, so updating the components will generally not cause difficulties in manufacture and installation.
• ◇ To further improve the dynamic stability of the main circuit, the ZMJ combined busbar clamp and insulating support dedicated to the GGD cubicle are used. The busbar clamp is thermoformed from a high-strength, highly flame-retardant PPO alloy material, with high dielectric strength, good self-extinguishing performance and a unique structure; a single or double busbar clamp can be conveniently assembled simply by adjusting the building-block spacers. The insulating support is of sleeve-type moulded structure with low cost and high strength, overcoming the insufficient creepage distance of older products.

Structure

• ◇ The cubicle body of the GGD AC low-voltage distribution cubicle adopts a universal cubicle form; the frame is assembled from 8MF cold-formed steel by local welding, and the frame parts and dedicated matching parts are supplied by designated steel section manufacturers to guarantee the accuracy and quality of the cubicle.
• ◇ The parts of the universal cubicle are designed on the module principle and have 20-module mounting holes. The high degree of standardisation allows the factory to carry out pre-production, which shortens the manufacturing cycle and improves working efficiency.
• ◇ Full consideration is given to heat dissipation during operation in the design of the GGD cubicle. Different numbers of heat-dissipation slots are provided at the top and bottom of the cubicle: when the components inside heat up, the heat rises and is discharged through the upper slots, while cool air is continuously drawn in through the lower slots, so that the sealed cubicle forms a natural air duct from bottom to top and the purpose of heat dissipation is achieved.
• ◇ In accordance with the requirements of modern industrial product styling, the GGD cubicle is designed using the golden ratio for the external shape and the division dimensions of each part, making the whole cubicle elegant and completely new in appearance.
• ◇ The door is connected to the frame by a pivoting hinge, making installation and removal convenient; a mountain-shaped rubber-plastic strip is embedded in the folded edge of the door. When the door is closed the strip has a certain compression travel, which prevents direct collision between the door and the cubicle body and also improves the degree of protection of the door.
• ◇ The instrument door carrying electrical components is connected to the frame by a stranded flexible copper wire, and the mounting parts inside the cubicle are connected to the frame by knurled screws, so that the whole cubicle forms a complete earthing protection circuit.
• ◇ The cubicle surface is plastic-sprayed, with strong adhesion and good texture; the whole cubicle has a matt tone that avoids glare and creates a more comfortable visual environment for the operators on duty.
• ◇ The top cover of the cubicle can be removed when required, facilitating on-site assembly and adjustment of the main busbar; lifting rings are fitted at the four corners of the cubicle top for lifting and transport.
• ◇ The degree of protection of the cubicle is IP30; users may also choose between IP20 and IP40 according to the service environment.
• ◇ The outline and installation dimensions are shown in Figures 1 and 2.

Installation & Operation

After the product arrives at the receiving site, first check whether the packaging is intact; if any problem is found, notify the relevant department in time to find the cause. Products that are not installed immediately shall be placed in a proper location in accordance with the normal service conditions.

Installation

The product shall be installed according to the installation drawing (see attached Figure 2). The foundation channel steel and bolts shall be provided by the user. When installing the main busbar, the contact surfaces shall be made flat and clean, coated with neutral vaseline or treated by other means, and then tightened with bolts.

Inspection & test items to be carried out after installation and before commissioning

• Check whether the paint on the cubicle surface has peeled off and whether the interior is dry and clean.
• Check whether the operating mechanisms of the electrical components are flexible, without jamming or excessive operating force.
• Check whether the making and breaking of the main components is reliable and accurate, and whether the auxiliary contacts operate reliably and accurately.
• Check whether the instrument indications and the ratio and polarity of the instrument transformers are correct.
• Check whether the busbar connections are sound and whether the insulating supports, mounting parts and accessories are installed firmly and reliably.
• Check whether the auxiliary contacts meet the requirements, whether the fuse link ratings are correct, whether the relay settings meet the design requirements and whether the operation is accurate.
• Check whether the circuit contacts comply with the electrical schematic diagram.
• Check whether the protection circuit system meets the requirements.
• The insulation resistance measured with a 500 V megohmmeter shall not be lower than 10 megohms.

Precautions for use

• This product is a low-voltage distribution cubicle installed away from the wall, operated from one side (the front) and maintained by opening doors on both sides. The maintenance channel and doors of the product may only be entered or opened by qualified professional personnel for operation, inspection and maintenance.
• After many closing and opening operations, the main contacts of an air circuit breaker may be locally burnt and carbon deposits produced, increasing the contact resistance; the air circuit breaker shall be maintained and serviced periodically according to its instruction manual.
• It is strictly forbidden to open or close the disconnector under load.

Delivery Documents & Accessories

The manufacturer shall supply the following documents and accessories:

• Packing list
• Product certificate and factory test report
• Instruction manual
• Relevant electrical drawings
• Instruction manuals of the main components
• Cubicle door keys, operating handles and spare parts specified in the contract.

Ordering Information

The user shall provide the following when ordering:

• Main circuit distribution system diagram and layout drawing, rated operational voltage, rated operational current, setting current of the protection device and the necessary technical parameters.
• Specify the specifications of the incoming and outgoing cables.
• Models, specifications and quantities of the main electrical components in the switchgear.
• If a busbar bridge or busway is required between switchgear cubicles or for the incoming cubicle, the specific data such as span and height above ground shall be stated.
• If the switchgear is used under special environmental conditions, this shall be described in detail when ordering.
• Surface colour of the switchgear and other specific requirements.

Outline & Installation Dimensions

Related Products

Low-voltage switchgear of the same series and other types available for selection:

• GGJ Low Voltage Reactive Power Compensation Device
• MNS Low Voltage Draw-out Switchgear
• GCK Low Voltage Draw-out Switchgear
• GCS Low Voltage Draw-out Switchgear
• GZDW Microcomputer DC Power Screen
• GZDW-1B Wall-mounted DC Power Supply