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Air-Insulated, Metal-Enclosed and Metal-Clad Medium-Voltage Switchgear


Air-insulated, metal-enclosed, metal-clad and type-tested medium-voltage switchgear.

IEC 62271

3AH series vacuum circuit-breakers

3TL series vacuum contactor

Rated short-circuit breaking currents from 31.5 kA to 50 kA

Rated voltage from 7.2 kV to 24 kV

Rated busbar and feeder normal currents up to 4000 A .

Typical Uses

Power stations, transformer stations and switching substations of public utilities.

Cement industry

Automotive industry

Iron and steelworks

Rolling mills


Food and fiber industry .

... .

Personnel Safety

•Protection against electric shock and ingress of solid 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.


•Bolted galvanized steel sheets subdivide the panel into

-Busbar compartment

-Withdrawable part compartment

-Connection compartment.

•Degree of protection between the individual compartments: IP4X/IP3XD

•Thanks to integrated cup type bushings, complete Compartmentalization even when the withdrawable part is in the connected position

•Upper and lower mating contacts fixed in cup-type bushings

•Enforced operated metal shutters for opening or closing the cup-type bushings when moving the withdrawable part

•Metal shutters can be locked when the withdrawable part is racked out

•Upper barrier (access to the busbar) or lower barrier (access to the cable) can be unscrewed independently of one another

•Optional resistance to internal arcing of the busbar compartment

High-voltage door

•Inspection window


-For checking the withdrawable part position

-For reading off the CLOSED/OPEN position indicator of the switching device, of the operating cycle counter and of the “closing spring charged” indication Lock

-For locking or unlocking the high-voltage door (taking the interlocking conditions into account) with an interlocking key

•Hand crank opening

-Hand crank for charging the operating mechanism springs of the switching device

-Opening closes automatically

•Door handle

-After the lock has been unlocked, the door is opened by lifting or is closed by lowering (taking the interlocking conditions into account)

•CLOSED/OPEN pushbutton of the switching device

-CLOSED/OPEN switching when the withdrawable part is in the connected position: When the door is closed, mechanically with pushbutton and tiltable extension mechanism for pushbutton actuation

-CLOSED/OPEN switching when the withdrawable part is in the disconnected position: When the door is closed mechanically by means of pushbuttons (direct actuation)

•Lever for tilting over the extension mechanism (see adjacent figure for operating principle)

•Openings for withdrawable part actuation

-For the hand crank for moving the withdrawable part (taking the interlocking conditions into account)

-For the interlocking key of the withdrawable part (same key as for the high-voltage door). .

Busbar mounting

•On commercially available cast-resin insulators

•Busbars bolted, length according to panel width .


•Metal compartmentalization to the withdrawable part and connection compartments with degree of protection IP4X/IP3XD

•Busbar compartment continuous throughout the entire installation, transverse compartmentalization with respect to neighboring panels possible .

Panel connection

•Connection of cables or bars to current transformers or post insulators

•Connection variants or types of installation are as shown in the illustrations

•Earthing and short circuiting via earthing switch directly at the point of connection

•Fixed-mounted voltage transformers within the current transformer protection zone .

Low-voltage compartment

•For accommodating the devices for protection, control, measuring and metering, e.g. bay controller SIPROTEC

•Shock-proof partitioning from the high-voltage section

•Pressure-resistant partitioning from the high voltage section

•Control cables of the panel are flexible and have metallic covers