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  Type 8BK20 Switchgear up to 24 kV with Withdrawable Circuit-Breakers
   
   
 

8BK20 switchagear for indoor installation with withdrawable circuit-breakers is suitable for:
• Rated voltages from 7.2 kV to 24 kV
• Rated short-circuit breaking currents up to 50 kA
• Feeder and busbar rated currents up to 4000 A

8BK20 switchgear is used in the following typical areas:
• Power stations, transformer stations and switching substations of public utilities
• Cement industry
• Automotive industry
• Iron and steelworks
• Rolling mills
• Mines
• Food and fibre industry
• Chemical industry
• Oil industry
• Pipelines
• Offshore installations
• Electrochemicals
• Railway power supplies
• Shipbuilding
• Diesel power stations
• Emergency power supplies
 
Personnal Safety Switching operation with door closed
Personnel safety increased by:
• Opening and closing of the switching device:
- In the disconnected or connected position
- Mechanically or electrically
- With the door closed.
• Isolation by moving the withdrawable section, manually or motorized, with the door closed.
• Verification of safe isolation from supply.
- According to DIN VDE 0105, Part 1, there are three alternative methods.
- Closing of make-proof earthing switch with the door closed
- Pole-by-pole testing with a capacitive voltage detector with the door closed
- Testing with conventional voltage testers to DIN VDE 0681, Part 4, but with the door open.
• Opening and closing of the earthing switch, optionally make-proof, with the door closed:
- Feeder: manual or motorized
- Busbar: manual
 

Interlocking of door/withdrawable section
The door is incorporated in the interlocking concepts as follows:
• Opening is possible only when the withdrawable section is locked in the disconnected position.
The withdrawable section can be moved from the disconnected to the service position only when the door is closed.

Protection against electric shock and ingress of foreign bodies
8BK20 switchgear provides both external and internal protection.
• External protection is provided by:
- Complete enclosure of the panels in all operating states.
• Internal protection is provided by:
- Internal metal compartmentalization with enforced-operation shutters, optional arc-resistant version of the busbar compartment.
- The inter-cubicle partitions; optional arc-resistant version.
• Degree of protection
Standard version IP4X/IP3XD.
Higher degrees of protection, such as IP31D, IP50 and IP51 can be obtained by additional measures.

Arc-tested sheet-steel enclosure or compartmentalization
8BK20 switchgear has been tested according to relevant standard for resistance to accidental arcing to ensure:
• External protection ( personnel safety )
• Optional resistance to internal arcing of the busbar compartment and between neighbouring panels ( going beyond the scope of the standards ).
 

Equipment reliability
Switchgear interlocking
All interlocks are mechanical with preven-tive, key-operated access shutters, i.e.:
• Operating levers can only be inserted when the interlocking conditions are fulfilled
• This prevents overstraining of the interlocking mechanisms.

Electric strength
Adequate electric strength of 8BK20 switchgear is assured by:
• Sufficiently large air gaps between phases and to earth
• Suitable electrode from
These design features allow all conductor insulation to be dispensed with entirely.

Highest level of independence of climate and environment
This is provided by:
• Ribbed insulators and bushings in cast reain, with high resistance to pollution
• Total enclosure under all operating conditions.

Maintenance
Minimal maintenance effort is assured by:
• Total enclosure under all operating conditions
• Use of proven, maintenance-free vacuum switching device.
Availability
Easy procurement of parts for extensions and repairs through the use of:
• Standard insulators
• Standard instrument transformers
• Standard vacuum switching devices
• Standard copper sections.

Operation
Moving a withdrawble section inside a panel
Little effort is required by hand or motor to move a withdrawble section inside a panel with the aid of:
• A spindle mechanism
• Ball-bearing rollers.

Moving a withdrawble section outside a panel
A withdrawble section is light and easy to move outside a panel:
• With a central service truck
• By one man
• Without tools
• Regardless of floor surface.
 

Sequence for removing the withdrawble section
• Move the withdrawble Section into the disconnected position
• Open the door
• Unplug the low voltage connector
• Unlock the withdrawble section ( unintentional removal of the withdrawble section is prevented by an additional interlock )
• Bring up the central service truck and lock it onto the panel ( additional interlock is then overridden )
• Pull out the withdrawble section onto the truck as far as it will go ( it cannot fall )
• Detach the central service truck and withdrawble section from the panel.

Remote control
Electric remote control, e.g. from a central control room, can be provided for the following functions:
• Moving a motorized withdrawble section info the disconnected or connected position
• Opening and closing of the switching device
• Feeder earthing and short-circuiting with motor-operated earthing switch.
There is also always local manual operation for all functions.
Installation Location