SF6-free RMUs | BGS-24

BGS-24, a versatile switchboard

BGS-24 is a medium voltage dry air-insulated switchboard up to 24kV, used in secondary distribution applications. It can be fitted with the following protection devices:

• Transformer protection
• Line protection

Its compactness, wide range of functions and ease of installation and extensibility, make it a versatile switchboard to fit many distribution applications such as: public distribution, industry, infrastructure or renewables.

Electrically insulated using dry air

The high voltage conductive parts of the BGS-24 switchboard are placed in green insulating air (dry and clean air) . The dry air is confined in a hermetically sealed stainless steel tank. BGS-24 is insensitive to the outside environment and to any possible aggressions such as:

• Humidity
• Dust
• Pollution
• Dirt
• Harmful rodents

The use of dry air as an insulating gas, and the design of BGS-24, makes it one of the most compact environment friendly MV switchboards on the market.

Simple operation and maintenance

With a service life of 30 years for the main circuit without maintenance, the overall design of the range of BGS-24 switchboards guarantees simple and reliable use:

• Simplified maintenance of the functional units
• No air filling is required on site at installation nor during the service life of BGS-24
• Under normal operating conditions
• Long service life
• Interlocking to ensure the correct sequences of operations
• Can be used in substations with or without walk-in operation corridors
• Voltage presence indicator light
• Wide cable compartment to allow the installation of various types of cable, etc.

Quality system certified

During manufacture, each BGS-24 functional unit is subject to systematic routine testing with the aim of checking the quality and conformity of the following features:

• Measuring of opening and closing speeds
• Dielectric test
• Testing of safety systems and interlocks
• Testing of low voltage components
• Conformity with drawings and diagrams

The results obtained are recorded and approved by the quality control department on each device’s test certificate. This therefore guarantees product traceability.

Environment system certified

As part of the manufacturer’s environmental policy, Brunstock equipment is managed under an environmental management system. BGS-24 has been designed with environmental protection in mind:

• All materials used, for instance gas tank and conductors, are identified, and easily separable for recycling
• Our production sites are certified to ISO 14001

Health and safety system certified

Workplace Health and Safety (WHS) bears the highest importance at Brunstock. The manufacture of BGS-24 includes controlling risks and making improvements in performance in compliance to ISO 45001: 2018. Brunstock supports the system’s focus on eliminating or minimising risks to personnel and other interested parties who could be exposed to WHS hazards associated with the manufacture of BGS-24.

Operating conditions

• Ambient temperature: from –5°C to +40°C (*)
• Average value over 24 hours (max.): +35°C
• Typical maximum altitude for installation above sea level is 1,000 m However, much higher altitudes are possible on request
• Type of insulating gas: Dry clean air
• Rated pressure at +20°C: 0.03 MPa

(*) Lower/higher ambient temperature on request.

Protection index (IP)

• Main electrical circuits (gas tank): IP67
• Enclosure: IP4X
• Between compartments: IP2X
• Switchgear: IK10

Partition class and loss of service continuity category

• Partition Class: PM
• Loss of Service Continuity Category: LSC1

Internal Arc Cl assification

BGS-24 is a pressurized sealed-unit system that complies with IEC 62271-1. Its tank is filled with dry air that is used as an insulating and breaking medium. BGS-24 internal arc classification as per IEC 62271-200 is detailed in the table below. In the unlikely event of air overpressure, the dry air is discharged via safety valves away from the operator.

IEC standards

Our BGS-24 switchboards comply with the standards shown below:

Advantages

Diversified solutions

• This SF6-free switchgear is an integral part of a green GIS solution
• Bus and line VT solution
• Load breaker switch solution
• Metering

Capability of development

• Self-developed the core components (circuit-breaker and threeposition switch)

Features

• Dry air insulation, vacuum interruption, environmentally friendly;
• No need to fill in dry air when on-site installation;
• Rated pressure for air filled is lower to 0.03MPA;
• With unique natural air cooling duct;
• Modular design, removeable gas tank and compartment;
• The main circuit is fully enclosed and insulated with IP67;
• The circuit-breaker is up to 630A, main busbar up to 630A and the rated breaking current 20kA;
• Main bus VT and arrester with isolation switch, easy for operation and maintenance;
• Compact size.

Vacuum circuit-breaker

Vacuum breaking technology is adopted for the circuit-breaker on BGS-24. The maximum rated current is 630A, the rated short-time withstand current is 20kA (3s), the electrical life is E2 (30 times), the mechanical life is M2 (10000 times). The three phases of A/B/C are horizontally arranged from left to right.

After the installation and commissioning of the cabinet, it is fixed in the “cabinet” after the overall installation. The specific structure is shown as below.

Function

• Rated opening and closing current;
• Short-circuit breaking and making operations;
• Corporate with TPS to achieve grounding function.

The TPS can only be operated the earthing switch when there is no current in the circuit, the earthing switch can only be closed once circuit-breaker opened.

The three-phase pole of the CB is horizontally placed in the CB gas tank, the operating mechanism is located outside for easy maintenance. The mechanism and the pole are connected by movable sealing bellows.

User interface description

Thanks to its clear mimic diagram, the user interface makes it easy and safe to operate BGS-24. Each switching device is equipped with an access point for the control lever and an indicator of the mechanical position.

The switch-disconnectors and vacuum circuit-breakers can be equipped, as an option, by a motorised control mechanism

1. CB motorised push button
2. Manometer
3. Circuit-breaker position indicator
4. Circuit-breaker manual close operation button
5. Spring charge indicator
6. Earthing switch operation hole
7. Disconnector position indicator
8. Earthing switch position indicator
9. Protection relay
10. Voltage presence indicating system
11. Circuit-breaker counter
12. Circuit-breaker manual operation button
13. Circuit-breaker operation hole
14. Disconnector operation hole
15. Observation window

Extensibility of BGS-24

• BGS-24 offers extensible configurations for secondary distribution applications;
• The connection of each functional unit allows for multiple combinations depending on the installation requirements. BGS-24 extensible permits the connection of additional units on the left or right-hand side, thereby offering greater flexibility in the choice and positioning of the medium voltage switchboard functions.
• The installation and in-line connection of BGS-24 extensible does not require any handling of gas;
• Maximum current: 630A.

Erection and assembly

The extension is a very simple process thanks to:

• The extension device used to connect the busbars of two cubicles. Variations in positioning are compensated by fixed, spherical contacts and mobile couplings that can be adjusted axially and radially;
• Highly secure dielectric seals made with silicone insulating conical connectors adapted to the electrical voltage; The assembly of the insulating connectors is maintained by a mechanical force generated by:
• Integrated guiding pins for the correct alignment of the cubicles
• An assembly by bolts secured by mechanical stops

During the assembly of an extension cubicle, an additional space of at least 450 mm is necessary to allow for handling.

Cable compartment

The cables connection compartment has been designed to accept connection systems that are:

• Completely insulated;
• In metallic housing;
• Partially insulated.

Cable support mountings are adjustable horizontally and vertically to enable installation of various cable systems. The cable mountings are equipped with either round or long holes for standard cable terminals. Additional support structures can be supplied for the installation of two cables per phase cable plug-in connections or surge arresters.

Current transformer

BGS-24 adopts straight-through type CTs, which can go through incoming/outgoing single or multiple cables and the main busbar. The external cone cable is used to connect the CT on the BGS-24. The three-phase integrated CT can be directly fixed on the outer cone sleeve. The primary current of current transformer is 100 to 1250A, and the secondary current is 1A or 5A. The specific secondary coil quantity, accuracy and capacity of CT shall be determined when ordering.

CT installation in the cable side

The cable-side circuit transformer passes through the incoming/ outgoing cable and is fixed on the beam on the cable compartment, as shown as below.

VT solution

Brunstock provides VT solution:

• A block VT (24 kV)
• Plug for VT

Surge arrester

BGS-24 surge arrester can be divided into two types according to the cable sockets, one with outer cone sleeve and the other with inner cone cable socket, plug in connection with the cubicle, and match with the 2# inner cone socket; The surge arresters of main busbar and line side are placed on the bottom of the cubicle. The specific technical parameters of arresters shall be determined when ordering.

Interlocking of the functional units

During the development of BGS-24, emphasis was placed on personnel safety and the reliability of the switchgear in operation. An interlocking system prevents any incorrect use. Thus, the operating levers can only be inserted if the service status permits it. Access to the cables compartment is only possible if the appropriate outgoing feeder is connected to earth. These ring main units are equipped with the following interlocks:

Packaging

For road and rail transport:
BGS-24 switchboard is packaged under protective sheeting. It is delivered fixed on to a wooden pallet by two plastic tapes.

For maritime transport:
BGS-24 is packaged in a heat-sealed cover with bags of desiccant, then enclosed in a wooden case with a solid leak tight bottom (including transport by container).

For air transport:
BGS-24 switchboard is packaged in a wooden boxes (crates) with solid walls and a protective cover (dust cover).

Handling

The BGS-24 must be transported vertically:

• When moving using a forklift: Only move the device on a pallet.
• When moving without a pallet: A lifting sling must be hooked on to the switchgear’s lifting rings. The angle with the lifting sling must be at least 45°.
• When transporting on pallet: Don’t tilt the switchgear. Respect the centre of gravity markings.
• When transporting with slings: Use the two lifting rings.

Plan

Brunstock representatives help you to plan the full design and execution of your solution, to secure your process and optimise your time. With training provided by Brunstock, our reps usually offer the following:

• Technical feasibility studies: Accompany you to design a solution specifically for the given environment
• Preliminary design: Accelerate turn-around time to come to a final solution design

Install

Brunstock representatives will help you to install efficient, reliable and safe solutions based on your plans.

• Project Management: Designed to help you complete your projects on time and within budget
• Commissioning: Ensures your actual performance versus design, through on-site testing, commissioning tools and procedures.

Operate

Brunstock reps help you maximise your installation uptime and control your capital expenditure through their services. Please ask them for specific details about their:

• Advantage service plans: Customised services plans which cover preventive, predictive and corrective maintenance
• On-site maintenance services: Extensive knowledge and experience in electrical distribution maintenance
• Spare parts management: Brunstock reps are able to ensure spare parts availability and can help you optimise thmaintenance budget for your spare parts
• Technical training: To build up necessary skills and competencies. In order to properly operate your installations in safety.

Frequency of maintenance intervention

Brunstock equipment manufacturers recommend a schedule for maintenance activities to extend Electrical Distribution equipment performance over time. Further information is available in the product manual and can be discussed with your Brunstock representative.